[1]
The Model A was not the only car of the time to have a positive ground
system. [2] Manufacturers using the Westinghouse system
were positive grounded, while those using the Delco system or the Remy system
were negative grounded.
The
automotive battery is composed of some number of smaller batteries called
cells. These cells with 2 Volts of
potential each are connected in series to provide the Battery Voltage
Rating. Batteries are sized to provide a
certain amount of energy which is stored within the battery case in the form of chemical
energy. This stored energy is called
“capacity”. The more the capacity, the
more electrical energy is available to be discharged into an electrical circuit
or device. The largest user of this
energy in the Model A Ford is the starting system. Lead-acid
automotive type batteries are usually made up of plates of lead and lead oxide,
which are submerged into an electrolyte solution of 35% sulfuric acid and 65%
water. When a battery is connected to an electrical load a chemical reaction
begins that releases electrons, allowing them to flow through conductors to
produce electricity. As the battery discharges, the acid of the electrolyte
reacts with the materials of the plates, changing their surface to lead
sulphate. When the battery is recharged, the chemical reaction is
reversed: the lead sulphate reforms into lead oxide and lead. With the plates
restored to their original condition, the process may now be repeated. In
modern batteries, not available to “Henry’s Battery”, several elements are
alloyed with the lead such as calcium, cadmium or strontium to change density,
hardness, or porosity of the plates and to make the plates easier to
manufacture.
There are two basic types of automotive batteries. The starting/shallow cycle type as used in
most automobiles, and the deep cycle type used in recreation vehicles and
boats. The starting (cranking) or
shallow cycle type is designed to deliver quick bursts of energy, usually to
start an engine. They usually have a greater plate count in order to have a
larger surface area that provides high electric current for short period of
time. Once the engine is started, they are usually being continuously recharged. The
deep cycle battery type are designed with thicker plates to withstand providing
continuous power for long periods of time and a higher number of
charge/discharge cycles. While it is
possible to use a “deep cycle” battery for a short period of time as an
automotive battery, it is not recommended to use this battery type in this
manner for a long period of time.
The original Model A Ford storage
battery had evolved from that of the Model T battery [3].
It was shipped with all Model A Ford’s.
All years of the Model A, had the same battery design. The battery that was shipped with the Model A
Ford in the years 1928 to 1931 was a flooded electrolyte 6 volt battery, with
an Amp-Hour capacity rating of 80 AH.
The battery was manufactured by the Ford Motor company itself, to
specifically meet the requirements of the Ford car. Ford was the only
automobile manufacturer to make its own battery. [4] The original battery as shown in the adjacent
picture from page 514 of the Model A Ford Service Bulletins, contained 13 lead
plates and a hard rubber casing. Ford
claimed that the original battery had a “starting capacity” of 98 Amps. It is not clear that this value corresponds
to any of the current definitions of various battery ratings. Research shows that when the temperature is
about 80 degrees F. the battery will provide about 98 Amps of cranking current [5]. Various Ford service bulletins showed a
charging rate of 6 to 14 Amps depending on the season and driving habits. The physical size of the original battery is
6 ¾ x 8 7/8 x 9 ¼ high.
Original
type batteries with the Ford script are available from various Model A parts
mail order dealers if you want to have a show quality battery. See Appendix 1 for various options available.
Ford
recommended checking the electrolyte in the battery every two weeks, to see
that it is at the proper level at the bottom of the filling tube. It was recommended that distilled water that
was stored in clean glass, rubber, lead, or china vessels. Ford in the Model A instruction book,
recommends that in cold weather, water should be added only just before the car
is started, to prevent freezing. Ford
also recommended that the battery be kept clean, and wiping the battery with a
rag moistened with ammonia to counteract the effect of any water/electrolyte
solution on the outside of the battery.
Additionally, they recommended a coating of vasoline
on the terminals to counteract corrosion.
The basic function of the Model A Ford battery is to
start the car. It is this starter motor
power requirement which sizes the battery system for the Model A. Unfortunately, there are several opposing factors
which combine to make it difficult for the Model A. Firstly,
the voltage of the Model A Ford electrical system was designed around the most
common voltage in the low cost automotive industry of the time, 6 volts. There were other voltage systems including 12 volt systems prior to the Model A, such as
the Dodge Brothers cars built from 1914 to 1925, but most manufacturers
designed around the 6 volt “standard”.
Henry Ford’s Model T was a 6 volt system. The eventual universal 12 volt standard of today
was yet to be established. Secondly, the lower voltage
starter motors of that day were less efficient than the 12 volt starters of
today. More importantly, thirdly due to engine friction,
poorer combustion, and oil viscosity, a Model A engine requires more power to
start as the temperature goes down. Les
Andrews, in his Model A Ford Mechanics Handbook [6] , shows that it takes nearly double the power
to crank a Model A engine at zero degrees Farenheit than it does at 80
degrees. Unfortunately the starting
power capacity available from the battery goes down by 60 percent over the same
temperature range. Finally, the Model A was shipped with the lowest capacity
battery of all makes in those years.
Furthermore, the conditions of the connections between the battery and
the starter, and the battery to the frame ground, will affect the ability of
the car to start, especially in cold weather.
The remainder of this discussion assumes that the connections are good
and do not cause a reduction in capability to start.
We can compare the Model A Ford battery to those used in
other makes of automobiles of the time.
In 1928 the capacities ranged from 80 Amp-Hr used in the Model A to 192
Amp-Hr. used in the Stearns Knight. The
average was about 130 Amp-Hr with the larger capacities in the more expensive
cars. Only Overland and the Pontiac 6
used a compariable 80 AH battery. Other
low cost cars, used somewhat higher Amp Hour batteries such as; Chevrolet 90 AH, Dodge 100 AH, Essex 105 AH,
Nash 110 AH, Plymouth 90 AH, and
Studebaker at 100 AH.
To understand the operation of the starter motor –
battery relationship we must reverse engineer the Model A starting system. The original design specifications are sparse
and do not give a complete story.
Fortunately, we have some test details and some estimates, as well as
some Ford specifications to work from.
In this paper, what is important is the relationship of starting motor
performance versus temperature. After
developing these values we can then apply these requirements to the battery
design to see the capacity to start the Model A under unfavorable conditions
and/or under multiple attempts to start the car.
Here is what we have to work with.
1) Tests of the Starter Motor [7]
have determined the relationship between starter motor torque, voltage,
amperes, and starter revolutions per minute.
2) The Starter Motor to Engine Flywheel gear ratio = 11.2
: 1 [8]
3) Les Andrews table of Temperature vs. Starter Motor
Power 1
These
values can then be related to the following chart. The following discussion is limited to the
starting motor performance for a Model A Ford manufactured during the years
1928 to 1931 using an original stock 6 Volt battery with positive ground.
Figure 1 Battery Voltage to
Starter vs. Engine Turning Rev/Sec
The open circuit voltage of the Model A battery is 6.3
Volts. As long as the current draw for
any other device is small, this is the voltage that will be initially applied
to the starter if the battery is fully charged.
When the starter motor switch is depressed this voltage will instantly
drop according to the current draw, and is applied to the starter motor and
current will begin to flow through the starter and thence to ground. The motor will turn its pinion gear at an RPM
that is determined by the load on the gear and the battery voltage. The load on the gear is applied via a large
gear on the flywheel. The ratio of the
flywheel gear to the starter pinion gear is 11.2 :1 Depending on the temperature, friction, oil
viscosity, and the condition of the battery at the time of starting, the engine
will begin to turn if its starter motor torque can overcome the value of the
stalled power requirement. Testing has
shown that the starter motor will stall (be locked) at a power of about 3 Volts
x 550 Amps = 1650 Watts and is equivalent to about 15 ft-lbs of torque when the
pinion has Zero Revolutions per Second (RPS) . Likewise, if the starter motor
has no load (engine disconnected) the starter motor free running speed is 4000
RPM at 6 Volts and 50 Amps (300 Watts) or an equivalent engine Revolutions per
Second of about 6 RPS. Typical Model A
starting revolutions are between these two values.
The starting current of the Model A with a 6 Volt Battery
is high, nominally 100 to 200 Amps. This
high current demand causes the Voltage of the battery to sink from its open
circuit voltage of 6.3 Volts, the higher
the current demand the lower the voltage that will be applied to the starter.
Higher currents and therefore lower voltage is caused by the Model A having an
increased friction load. This
relationship is shown in the above chart.
Typically, at high temperatures and low friction, with a fully charged
battery, the current demand is about 100 Amps which drops the battery voltage
to about 5.9 Volts. At this value the
engine will turn at about 4 revolutions per second. As the temperature goes down, and friction
goes up due to oil viscosity and friction within the engine, the starter motor
torque requirement increases causing the starter motor to demand more
current. Increased current, can cause
currents in the starter motor windings to be up to 275 Amps or higher. As the demand for current goes up the battery
can only supply this current at a loss in voltage and subsequent lower
revolutions per second. For
example; if the current demand is
increased to 175 Amps, the battery voltage will sink to about 5.3 Volts and the
engine revolutions per second will drop from 4 RPS to 2 RPS. This effect is repeated until the Model A
engine is turned with great difficulty.
This point is typically reached when the battery voltage is about 4.5
Volts [9]
and the starter current is about 275 Amps.
The nominal recommended battery voltage for starting the Model A is
determined from the chart as between 5.9 and 5.3 Volts which produces 100 to
175 Amps of current. These values will
turn the Model A Engine (in good working order) at between 2 and 4 revolutions
per second. Below 5.3 Volts and down to
4.5 Volts it is uncertain whether the Model A will start. While it is possible
that the engine can catch a spark and power up between 1 and 2 RPS it is not
reliable. Below 4.5 Volts it is unlikely
that the Model A will start.
Now we turn to the consideration of starter motor
performance versus temperature. The
reference to starter motor requirements versus temperature are from Les Andrews
[10]
. This chart shows the “starting power”
required by the engine (starter motor torque) versus temperature. These values over the range from 80 to -20
degrees are in close agreement with test observations. The experimental data shows that as the
temperature approaches -20 the linear relationship of temperature versus torque
(and therefore the starter current) required to spin the pinion begins to
become non-linear and increases exponentially to finally locking up at about
-40 deg F. Figure
2 Starter Motor Performance vs Temperature
shows these relationships.
Bench tests on the starter motor, yielded the starter
motor current versus engine RPS during the starting cycle. However, these tests did not include
temperature effects and oil viscosity or the ability of the battery capacity to
supply the needed power. The Ford
engineers of the time understood the need to reduce oil viscosity in the winter
to allow the Model A to be started after standing in below zero farenheit
temperatures for some time. Therefore,
they recommended using 20 weight oil in the winter and 40 weight oil in the
summer. It is unknown which oil has been
used to determine the effect on starter motor torque due to lower temperatures
in the Les Andrews chart of starter motor power versus temperature. However, we can speculate that using a modern
multigrade oil such as 10W-40 in a Model A will inprove the performance
somewhat in the lower temperature range, perhaps even allowing the Model A to
be more reliably started in temperatures approaching -20 degrees.
Figure 2 Starter Motor Performance vs Temperature
The Figure
2 Starter Motor Performance vs Temperature
also shows that the Model A is reliably started between 100 and 32 degrees
Farenheit, but begins to show difficulties below 0 degrees F. The engine revolutions per second generated
by the starter are determined primarially by the battery voltage as shown in Figure
1 Battery Voltage to Starter vs. Engine
Turning Rev/Sec. The Model A’s battery condition and state of
charge at the time of attempting to start the car, will determine the battery
voltage that can be applied to the starter, and therefore the revolutions per
second of the engine. Assuming that the
battery is “fresh” [11],
fully charged and able to deliver at least about 5 volts, the engine should
reliably start between the temperatures of 100 degrees and to below 0 degrees
F. However, if the battery capacity is
reduced because of age, lack of complete recharging, or have some of the
internal lead plates defective, or if the engine friction is high, and the oil
is heavy and viscous, the car may only reliably start between 100 and about 32 degrees F. Therefore, we divide
the curve depicting Engine revolutions versus temperature into a red zone, a
blue zone, and a black zone. The red
zone means reliable starting under most conditions, blue under favorable conditions,
and black starting only under rare conditions.
These observations are made from the available data. [12]
Now that we know the starter motor performance versus
temperature, we can estimate the capability of the original Model A Ford 6 volt
battery with its 80 Amp-Hour capacity to start the car at various temperatures
The Ford Motor company sized its 6 volt battery as an 80
AH battery as shown in its literature of the time. As discussed before, the Amp Hour capacity
of the Model A battery was the lowest of the manufacturers of the time. Data by Jim Schild [13]
shows that the Ford Motor company used near traditional means of estimating Amp
Hour rating for its batteries.
Traditionally the battery Amp-Hour rating is given by the following
equation:
Rating Amperes = Rated Capacity /20
For the Original Ford Battery would be 80/20 = 4 Amperes. However, there is no evidence that the Ford
engineers used this value.
Evidence for this provided in Schild’s book where he
states that the “lighting capacity was 5 Amps for seventeen hours. This translates to a capacity of 85
Amp-Hours, pretty close to the original
80 AH Ford battery.
It is widely known, both then and now, that heavy current draws or rapid discharging
reduces capacity of the battery to deliver energy. For example; if we assume that an 80 AMP-Hour
batttery (rated at 4 Amps) is being drained with a 100 AMP load that the
battery capacity would allow cranking at this level for 0.8 hours we would be
in error. A German scientist named W.
Peukert experimented with batteries in 1897, and established Peukert's [14] Law, which expresses the capacity
of a battery in terms of the rate at which it
is discharged. As the rate increases, the battery's capacity to deliver
decreases, although its actual capacity tends to remain fairly constant. In other words, as the temperature decreases
the battery ampere draw increases, linearly at first, and non-linearly as the
temperature drops below 0 deg F. As this
current draw increases, the capacity of the battery to supply this current
decreases. Peukert’s
law (described in Appendix 2) can be expressed so that we can calculate the
time that a rate of Amps of current can be extracted from a battery. Peukert’s work has
been used for many decades as the means of determining battery capacity during
high current discharge. Other
researchers have improved on the means of using Peukert’s
work and have determined an equation which utilizes commonly advertised
capacity ratings for various batteries.
The following discussion is limited to lead-acid batteries such as used
in the Model A Ford. Peukert
determined that there is a constant which can be used to derate
the capacity of a battery as the discharge rate increases. This constant cannot be used across different
battery chemistries. It must be used to
predict performance within the group of batteries to which it applies.
Having
said all that, the Peukert equation for discharge
time can be stated as:
where:
H is the hour rating that the battery is
specified against
C is the rated capacity at that
discharge rate.
I is the discharge current, expressed in
A.
k is the Peukert
constant
and
t is the time of discharge, expressed in
hours
The
battery capacity for starting the Model A has been stated by Jim Schild as “Starter Capacity required is 98 AMPS for 20 minutes” [15]
. To determine if Schild is correct,
since he does not state where he got this information, we can check the Ford
Motor company specifications. Ford
published [16]
that the Model A battery is an advertized 80 AH battery. At the specified low current draw of 5 Amps
this yields 16 hours of capacity. Using
Peukert’s equation, with a Peukert constant of 1.3 for a “fresh” battery [17] and the advertized values;
16 16
t = --------- = --------
= .334 hours = 20.01 Minutes
(98 x 16/80)1.3 47.85
where:
H is 16 hours (80 amp-hours divided by 5 amps) where 5 amps
is the low discharge rate.
C is 80 Amp-Hours
I is 98 Amps
k is the Peukert
constant = 1.3 for “fresh” lead-acid batteries
t is the time of discharge
and
t is expressed in hours at a constant 98 Amp
discharge rate
Therefore, Schild is quite correct in that the original
Ford battery can deliver 98 Amps of cranking power for 20 minutes. Now we can extrapolate this to other values
of current discharge rates at various temperatures.
The Figure
3 Capacity versus Temperature describes the capacity of a Model A battery
to deliver the required starting power to the Model A starter versus the
temperature of the system at the time of initiating starting. The conditions of the validity of this chart
are; a “fresh battery” (not one that is 4 years old), a fully charged battery,
a battery with at least the 80 AH rating of the original Ford battery.
At temperatures of about 70 to 80 degrees Farenheit, the
required starter motor curren is about 100 Amps, this heavy draw causes the
battery to have a capacity reduced to 40% of its rated capacity or about 32 Amp
Hours. It can deliver the current for
about 16 minutes. The chart shows that
at a low temperature of -20 deg F, the
extra current draw, reduces the advertized capacity to about 25% of the
original, and can only deliver about 3 minutes of cranking power to start the
Model A .
This does not mean that the car will actually start, that
depends on the volitility of the gasoline, the condition of the engine and the
type and condition of ignition system.
Older batteries, and those batteries that have been poorly maintained,
and have high degrees of sulphation (we will discuss this later on), will
deliver much less capacity than shown in the chart.
Since it is unlikely, that a restored Model A owner, will
be using the vehicle in such adverse condtions, the 80 Amp Hour capacity is
adequate for the hobby car. In 1928 to
1931, a higher capacity would certainly have been welcome.
Figure 3 Capacity versus Temperature
The original Model A Ford battery recharging system is
equipped with a generator and a sort of psudo-regulating system called “the
third brush”. The Model A Ford is also
equipped with a “cutout” The purpose of
the cutout is to prevent the battery from discharging back through the generator
to ground if the car is stopped or moving at a slow speed. The cutout does not perform any voltage or
current regulation at speeds above 10 mph.
The cutout will close and the generator will begin to supply current to
the electrical system at about 700 RPM or a car speed of about 10 mph. This varies of course depending on the cutout
and the 3rd brush settings.
The generator will act as an electric motor if it is connected directly
to the battery, with the engine running
the engine drives the generator pully enough to provide the current necessary
to operate the various electrical circuits and charge the battery. When the
Model A gets up to 9 or 10 mph the generator produces enough current to cause
the magnetic field in the relay of the cut-out switch to activate and “close”
the contacts, connecting the generator
to the battery, allowing the generator to provide power to charge the
battery. When the Model A speed drops to
about 7 to 8 mph the current flow to the cutout winding drops below the value
to keep the relay closed and the cutout “opens” and disconnects the generator
from the battery. Typically, the
generator is adjusted to produce some number of Amperes of charging current
with the lights and other current draws are turned off. The amount of Amperes was manually adjusted
by the owner, according to his driving habits and the season of the year. The output of the generator is adjusted by
moving the third brush of the generator.
During daylight operation the battery is charged with about 9 to 10
Amperes which is reduced at night by the lights which draw about 6 Amperes. Thus at night the battery charge is reduced to
about 4 Amperes.
As opposed to modern voltage regulated charging systems
such as found in older generator charging systems, and modern alternators, the
stock Model A Ford will not charge the battery when idling. Typically, the idle speed of a Model A is
below 700 RPM, therefore, the generator is not providing enough current to
close the cutout switch. Thus, to charge the battery we must drive the car at
some speed above 10 mph for a long enough time to replace the amp-hours of
capacity that were removed from the battery during the starting cycle. To understand this, we resort to an example
or two.
Example 1: A
Model A with a “fresh” battery is started at 60 degrees Farenheit. From our previous chart we have shown the
starter motor to requireabout 125 Amperes to turn the engine at 2 ½ revolutions
per second. From experience this takes
up to about 15 seconds to start the engine.
We can calculate the Amp-Hours extracted from the battery from the
equation:
AH (removed) = Starting Current(amperes) x Time Starting(in hours) = 125
x 15 seconds = 0.52 AH
To replace this capacity lost due to starting we must
drive the car with the generator charging at 10 Amps for the time shown below:
AH (replaced) = Charging Current(amperes)
x Time Driving(in hours)
Solving this for the time required yields:
AH (removed) 0.52
AH
Time Driving =
----------------
= ------------ = .052 hours = 3.1 Minutes
Charging Current(Amperes) 10 A
Not a very long time.
But consider the next example:
Example 2:
A Model A with an older battery which has had some
neglect is started at 0 degrees Farenheit.
From our previous chart we have shown the starter motor to require about
250 Amperes to turn the engine at about 1 ¼
revolutions per second. At this
temperature it may take up to a minute of cranking (4 attempts at 15 seconds
each). As before, we can calculate the
Amp-Hours extracted from the battery.
AH (removed)
= 250 A x 60 seconds = 250
x .0167 hr = 4.3 AH
The driving time to replace this capacity is
4.3 AH
Time Driving =
---------- = .43 hours = 26 Minutes
10 A
If this is at night the time necessary is increased since
the battery is only charged at about 4 Amps
requiring about 1 hour of driving time to replace the capacity.
Consider the 1931 pastor of a church in the midwest
during the winter at 0 degrees F. He
goes out to his Model A with a fully charged battery that has about 22 AH of
equivalent starting capacity and starts
the engine in the evening with the temperature at 0 degrees and drives 10
minutes to visit one of his congregation.
He removed 4.3 AH from the battery and replaced only 1.7 AH. Therefore his battery is now down to about 20
AH. He stays for a couple of hours and
the engine cools down to ambient. He
then starts the car and drives 5 minutes with the lights on to the church to
attend a committee meeting. He is now
down to about 18 AH. After 3 hours, the
pastor again starts the Model A and drives home after dark with the lights on,
and since it is snowing and icy he drives slow at less than 10 mph, and parks the car. The next morning the temperature has dropped
to -10 and the pastor is stuck with a car which won’t start!
Lucky for us, the modern day owners of our pride and joy
restored Model A’s, we pamper and baby the 75 year olds and wouldn’t think of
taking them out in 0 degree or below weather.
Therefore we will probably never be in the situation of the old time
pastor. But, think of those times, it
was not easy to be a Model A owner then.
The owners of these cars in the olden days had to think of the
conditions that they were going to be in, and travel accordingly. I remember that my father, who owned a 1935
Ford during World War II , would agonize over attempting to travel from Long
Beach to Pasadena in southern California for hours if the temperature was below
32 degrees. This distance was all of 25
miles, but for him it was the equivalent of 1000 miles for us today.
Battery
Life depends on how they are used and maintained, temperatures, and even
storage periods. Deep discharges, rapid
charging, extreme temperatures, and continuous use all shorten a battery’s
life. A poorly maintained battery, that
is consistently overcharged by the Model A generator, and stored for several
months without a maintenance charger may only have a life of 2 years. On the other hand a properly maintained
battery, that has had limited overcharging, or one with a voltage regulator
that prevents overcharging, and has been stored with a maintenance charger may
last up to 5 years. While batteries are
not the most expensive devices on a Model A, it is comforting to know that
while you are on the tour, in the middle of nowhere, your Model A is going to
start. The ability to find an 80 AH 6
Volt battery in Podunkville Kansas, may be difficult.
The main
four problems of battery life are, lack of electrolyte due to evaporation
caused by the charging process, storage at a low state of charge, storage at
low temperatures with the battery at a low charge level, and overcharging by the Model A generator. The ability to discharge and recharge flooded
electrolyte lead-acid batteries is also limited by battery life, as the battery
ages the recharge capability decreases.
We will now discuss the main problems that cut short the life of a
battery.
For the
Model A Ford the easy one to keep under control is prevention of the lack of
electrolyte. However, we too often
forget about the battery, since it is hidden away under the floor boards. Too low an electrolyte level in the battery
has two effects. Firstly, the
concentration of acid to water is increased.
This increase in electrolyte acid concentration chars and disintegrates
the separators between the lead plates.
In addition, the plates themselves become partially exposed to air,
stopping chemical action from taking place, and limits recharge ability, and
reduces capacity. It is a relatively
simple maintenance procedure to remove the battery inspection plate attached to
the floor board, directly under the steering wheel, remove the battery caps (if
you are not using a “maintenance free” battery) and check the electrolyte level
in the cells. The electrolyte should be
level with the bottom of the filler tube.
This process has not changed since the Model A Ford was produced. Ford, in its instruction book [18],
says that the owner should;
“Every two weeks check the
electrolyte in the battery to see that it is at a proper level. The solution (Electrolyte) should be
maintained at a level with the bottom of the filling tube. If below this point,
add distilled water until the electrolyte reaches the proper level”
Even if
there is no load on a typical automotive battery, the battery will lose a small
amount of charge as time goes on. Just
sitting around, the battery will “self discharge”. As the battery discharges lead sulphate accumulates on the surface of the plates and
reduces capacity. When recharged, most
but not all, of the lead sulphate returns to the
electrolyte. However, the remaining
small amount accumulates and reduces capacity.
Therefore, a battery as soon as the electrolyte is added, begins a slow
automatic “wearout mechanism” and will deteriorate
over time, even if it is not used, or even if it is trickle charged. If a battery is left in a low state of charge
for a prolonged period of time, the plates become heavily sulphated
and may permanently lose the capability of being recharged.
Storage
of the Model A with a low state of charge can cause the battery to fail in cold
weather. Leaving a battery in the car
over the winter without maintenance charging will cause the battery to
self-discharge and have a low state of charge.
When batteries are left in a low state of charge they quickly become sulphated and may even permanently lose the ability to be
recharged. While, at a high state of
charge, a fully charged battery is quite resistant to freezing and can survive
temperatures well below zero. However,
when discharged, they have a much higher ratio of water to acid level and can
freeze at just a few degrees below the 32 degree freezing point of water. Therefore, it is important for these two
reasons to keep the battery on a maintenance charger during the winter when the
car is not being driven. Freezing of the
battery water-acid mixture can crack the case and destroy the battery.
The more
difficult of these enemies of battery life to prevent is over charging. The charging system of the Model A does not
have a voltage regulator to reduce the amount of charge current put into the
battery during driving after the battery is charged. Overcharging causes the positive lead plates
to flake and float to the bottom of the case and form a “floor” of a thick mud
like substance. This substance is
conductive and if it reaches the level of the plates will short out one or more
of the battery cells, causing the battery to fail due to low voltage
supply. The battery case is designed to
allow some amount of this flaking. The
Model A Ford the life of the battery is directly related to overcharging. Since the stock generator charging system is
regulated for current only and puts out a constant current, determined by the
position of the 3rd brush, to the battery regardless of the state of
charge, it is easy to see that the battery can be overcharged. Ford introduced voltage regulation to provide
overcharge protection in 1935.
For
example:
A Model
A Ford with a fully charged 6 Volt battery is started at about 60 degrees Farenheit. The
amount of energy taken from the 80 AH capacity battery is about 0.52 Amp-Hours which is replaced by the
generator after only about 3 minutes of driving. After this, the generator is supplying excess
charge which is not needed.
Overcharging
of the Model A battery due to constant current operation of the generator was a
continuing problem for the Ford Motor company and the Model A owners of the
time. This problem existed for not only
the Model A owners of the time, but other manufacturers as well. Ford issued seven (7) service bulletins over a
three year period advising dealers and mechanics to address the issue of
overcharging.
With the
stock Model A Ford charging system, using the 3rd brush generator,
it is probably not possible to prevent overcharging. Various charge rate settings can be trialed
but non will fit all driving conditions that you will face.
The
“right” generator charging rate for a stock Model A Ford is a matter of debate.
The Ford Motor Company during the years
of manufacture, issued a number of
Service Bulletins which have shown ever lowering generator charge rate settings. Over the years, restoration specialists have
recommended other settings. Some
specialists recommend setting the 3rd brush for 10 Amps [19],
others much lower . However, as shown
below, this rate is too high for summer time and touring of the stock Model A
Ford. Jim Schild
recommends a general setting of 6 Amps and reducing this to 2 to 4 amps when on a tour [20]. To learn more about the proper setting, and
to learn how to prevent overcharging read the following.
During
the years of manufacturing the Model A, Ford told owners that the generator
charging rate should be adjusted seasonally [21]. Ford recommended the following;
“During winter months where low
temperatures prevail the charging rate should be adjusted to 10 Amperes; in the summer this rate should be cut down to
6 Amperes.
Ford
went on to also say that owners should increase or decrease the charging rate
to individual requirements and that:
“An owner who takes long daylight
trips could cut down the charging rate even less. On the other hand, the owner who makes
frequent stops, should increase the normal rate if his battery runs down.”
Beginning
in June 1928 Ford began to notify its dealerships, through the Service
Bulletins, of the problem of overcharging the battery. The following information has been gleaned
from a book which compiles all of the Model A Service Bulletins. [22]
The Ford
Service Bulletin for January 1928 [23]
said something different than the instruction book. The service bulletin stops short of recommending
an average charging rate of 12 Amperes.
The service bulletin says;
During winter months the charging
rate should be adjusted to 14 Amperes; in the summer this rate should be cut
down to 10 Amperes. The rate can of
course, be increased or decreased to meet individual requirements. For example, the owner who takes long
daylight trips should cut down the charging rate to 8 Amperes to prevent
battery overcharging. On the other hand,
the owner who makes numerous stops, should increase the normal rate if his
battery runs down.
The Ford
Service Bulletins for June 1928 and May 1929 told the dealer mechanics that
“with the arrival of warm weather” the
charging rate of the generator should be changed and provided information on
how to adjust the charging rate. Apparently Ford considered that its original
rates of 14 Amps winter, and 10 Amps summer was too high, and suggested a 40%
lower rate of 6 Amps. The rate
recommended was;
“For average driving a charging
rate of 6 amperes or slightly less is sufficient and prevents the possibility
of overcharging the battery. This rate
can, of course, be increased or decreased to meet individual requirements. For example, the owner who takes long
daylight trips can operate with a comparatively low rate. On the other hand, the owner who makes
numerous stops can increase the normal charging rate if the battery shows
indications of running down.”
Another
Service Bulletin for December 1928 tells the Ford dealers to inspect cars
carefully for battery charging rates, and again reduced the charging rate;
Generator Charging Rates:
Should be adjusted to suit
individual requirements. For average
driving during cold weather, a charging rate of 10 Amperes at 1500 RPM will
prove satisfactory.
Yet
another Service Bulletin for May 1929 tells the Ford dealers that:
For average driving during the
summer months a charging rate of 6 Amperes is sufficient. This rate can of course be increased or
decreased to meet individual requirements.
For example the owner who takes long daylight trips could cut the
charging rate down even less. On the
other hand the owner who makes numerous stops should increase the normal rate
if his battery becomes weak.
By mid
1929 Ford was even more worried about customer satisfaction and advised the
dealer mechanics to check with the owners and adjust the charging rates. The May 1929 Service Bulletin adds an
admonition in bold letters that the dealers should;
“Instruct
mechanics to check owners’ cars and adjust the charging rate to suit conditions
under which the car is operated. This is
important.”
The
October 1929 Service Bulletin shows that Ford has become sensitive to owners
having trouble with the “affect of cold
weather on the electrolyte in the battery, and the failure of mechanics to correctly
adjust the generator charging rate to meet the conditions under which the cars
are operating.”
The
October 1929 Service Bulletin admits that “Hard
Starting Resulting in Run Down Batteries” is a possibility at Zero
temperatures. The bulletin states;
At Zero temperatures the starting
ability of a battery is reduced to one-half its normal capacity and its
internal resistance proportionally increased.
In other words, a battery that will crank the engine for five minutes at
normal temperatures, will only crank it 2 ½ minutes at zero temperatures, and
only about half as fast. In addition,
the amount of daylight driving is considerably reduced. Also due to congealed
oil, the engine is stiff and requires considerably more power to turn it
over. These conditions often result in a
battery becoming partially or fully discharged.
When trouble of this kind is
experienced the remedy is to increase the generator charging rate by 3 to 5
amperes.
This
bulletin goes on to say that the cause of bulbs burning out can be caused by
the generator charging rate being set too high.
The bulletin also claims that if all of the connections to the
electrical system are clean and tight the remedy is to “cut down the generator charging rate approximately 2 to 4 amperes” However, the bulletin says that battery charge
status should be monitored and adjusted again accordingly.
The Ford
Service Bulletin for April 1930 says that;
“Adjust the charging rate for
summer driving 6 to 8 amperes at 25
miles per hour should be sufficient.”
The
October 1930 Service Bulletin had a large article on the generator charging
rate. It started out with a statement
that the Ford Dealers should “Keep the
customer satisfied, make sure that the generator charging rate is NOT too high
or too low.”
The
bulletin says that Ford Dealers should
“Check generator charging rate
for cold weather operation on all cars coming into your shop”
and
that;
“For average driving during cold
weather, a charging rate of 10 to 12 amps is sufficient.
This
bulletin also gave the now familiar song about the rate can be adjusted up or
down for the customers driving conditions.
The Ford Company said in this bulletin that;
“it takes 20 minutes running,
with the generator set at average charging rate to replace in the battery the
current taken out by one minute’s use of the starting motor. “
The
bulletin fails to say what the “average charging rate” is. The bulletin also repeats the hard starting
information that was presented in the October of 1929 Service Bulletin on
cranking time.
Jim Schild in his book on restoration of the Model A claims
that the generator is capable of putting out as much as 22 Amps, but it is
recommended [24] that it
be set at 6 Amps for normal driving situations.
He claims that “for extended daytime trips, a lower rate of 2 to 3 Amps
is desirable to prevent damage to the generator and battery.
The
earliest non-Ford Service Bulletin discussion on the issue of overcharging the
battery is found in a book by Victor Page [25]
published in 1931. He writes that
“During the Winter months, the charging rate should be increased from the 10
Amp “Summer Average” to 14 Amps. He also
writes that the rate should be increased or decreased “to meet individual
requirements”, and gives an example which is probably accurate for the type
touring and driving of our Model A’s.
“The owner who takes long daylight trips should cut down the charging
rate to 8 Amperes to prevent battery overcharging.” Page concludes that for “average conditions,
however, a charging rate of twelve (12) amperes [26]
is the most suitable”. Page’s
information is consistent with the earliest Ford Service bulletins, but is not
up to date with the latter ones that recommend a lower charging rate. More
recently, Les Andrews in his book on the Model A says to adjust the generator
brush for a 10 Amp charging rate.[27]
Summary of Battery Charge Rate Recommendations
We can
now make a table of the various suggestions on how to set the generator charging
rate versus driving conditions and seasons.
|
Where to Set the Model A Ford
Generator Charging Rate (Amps)?
|
|
Recommender
|
Overall
Average
|
Summer
|
Winter
|
|
Average
|
Long
Day Trips
|
Average
|
Long
Day Trips
|
|
Ford
Service Bulletin Jan 1928
|
Adjust Seasonally
|
10
|
8
|
14
|
Less than 10
|
|
Ford
Service Bulletin June 1928
|
Adjust
Seasonally
|
6
|
Less than 6
|
|
|
|
Ford
Service Bulletin Dec 1928
|
Adjust Seasonally
|
|
|
10
|
|
|
Ford
Service Bulletin May 1929
|
Adjust
Seasonally
|
6
|
Less than 6
|
|
|
|
Ford
Service Bulletin Oct 1929
|
Adjust
Seasonally
|
|
|
9 to 11
|
|
|
Ford
Service Bulletin Apr 1930
|
Adjust
Seasonally
|
6 to 8
|
|
|
|
|
Ford
Service Bulletin Oct 1930
|
Adjust
Seasonally
|
|
|
10 to 12
|
|
|
|
|
|
|
|
|
|
Ford
Instruction Book 1931
|
Adjust Seasonally
|
6
|
Less than 6
|
10
|
Less than 10
|
|
|
|
|
|
|
|
|
Victor
Page’s Book in 1931
|
12
|
10
|
8
|
14
|
|
|
Les
Andrews Handbook 2000
|
10
|
|
|
|
|
|
Les
Andrews Diagnostic 2000
|
10
|
|
8
|
|
|
|
Jim
Schild Shop Manual
|
6
|
|
2 to 3
|
|
|
From the
Ford Service Bulletins issued, it appears that Ford always recommended
adjusting the charging rate seasonally, and continued to revise its recommended
charging rate downward. Final settings
recommended by Ford seem to be those presented in the 1931 Instruction book,
since there are no service bulletins on the subject in 1931. It appears that Ford finally settled on an
average setting of 6 Amps for the summer season and 10 Amps for the
winter. These values were, however, to
be adjusted up or down to meet individual customer requirements.
Victor
Page seems to make his recommendation stemming from the original Ford settings
of 10 to 14 Amps in early 1928 and in general these settings are too high.
Jim Schild recommends a charge rate setting on the low end with
an average setting of 6 Amps, with a reduction to 2 to 3 amps for long tours. This would conform to Ford’s recommendation
for summer driving. Whilst, Schild does not state information about winter driving, it
is perhaps since he assumes that the restored vehicle is going to be used in
warm weather only.
Les
Andrews recommended setting of 10 Amperes seems too high for summer driving and
may lead to an overcharged battery.
Since
there seems to be a wealth of values postulated as where to set the generator
charging rate, where does this leave
us? It appears that for our typical
restored Model A driving conditions, especially in the summer when driving
around town, we should adjust the generator, if you don’t have a voltage
regulator, charging rate to somewhere in
the vicinity of 5 to 8 Amperes. If we
take a long tour (anything over 100 miles) we should cut the charging rate down
to about 4 to 6 Amperes. One must be
careful in these lower settings, because if there is much night driving with
the lights on, it is possible, since the headlights draw about 5 Amperes or more,
to put the battery into a discharge condition all the time while driving at
night. During the winter, if we start
the Model A in temperatures about 32 degrees or less we should set the charging
rate up to about 8 to 10 Amperes.
If we
take a longer trip with the generator charging rate set to the high side say 10
Amps, there is a trick we can play. The lights can be used as a generator
charge reduction trick. This trick was
commonly known by the owners of both the Model T and the Model A during the 20s
and 30s. The ammeter is used to gauge
the charging rate to the generator.
Since the generator both supplies power to run the electric lights and
to supply the battery recharge. The current demanded by the lights will
automatically reduce the generator charging current to the battery.
The
Ammeter a means of monitoring the charge rate, is connected as shown in the
figures below.
Figure
4
Electrical System "Garaged"
The
figure shows the electrical system with the Model A not running and with the
lights and other devices turned off. The
ammeter is positioned between the output of the cutout and the battery,
therefore it will always indicate the total flow of the current to or from the
battery which will be dependent on various conditions. It will not indicate the current flow to the
starter. When “garaged” with the motor
not running, and all lights etc. turned off.
The ammeter should read zero (0 Amps).
When
starting the Model A the current flow will be from the Battery
to the Starter Motor as shown Figure
5 Model A Ammeter Reading during Start. Since only
a small amount of current is flowing to the ignition circuit, the ammeter will
be reading near zero or slightly negative.
Figure 5 Model A Ammeter Reading during Start
The
generator, while turning slowly, is not generating enough current to close the
cutout relay. The battery will discharge
a large amount of energy to the starter.
In warm weather the amount of Amp-Hours withdrawn from the battery is
typically about 5 seconds of cranking at about 100 Amperes or about 0.3 Amp
Hours. During cold weather or in the
morning this can be on the order of 15 seconds at 175 Amperes or about 0.7
Amp-Hours. This energy will need to be
replaced by the generator after the car is running. At Idle or below about 700 RPM (about 10
MPH) the stock generator cutout will not close and the current flow as shown below will be out
of the battery to the ignition system.
If you have replaced the stock relay cutout with a diode type any
current available from the generator will flow through the ammeter.
Figure
6
Model A Ammeter Reading at Idle
At idle
or, during driving the Model A, at speeds below about 10 MPH the battery will
discharge, since the generator is not connected. [28] If the car is driven at this speed or less
with the lights on, an additional discharge of about 5 Amps times the time at
speeds of 10 MPH or less. This additional
discharge will add to the amount of Amp-Hours extracted from the battery. Figure
7 Model A Ammeter Reading No Lights shows the current flow above about 10 MPH.
After
the cutout closes the generator develops an output current which depends on the
setting of the 3rd brush.
This current flows out of the generator at the output of the cutout and
divides into that required of the electrical circuits turned on in the Model A
and battery charging. During daylight
this is the ignition circuit and any other accessories or the brake light. The remainder of the current flows through
the ammeter and thence to the battery providing charging current. With the
lights on the current to the electrical circuits increases due to the lighting
load and decreases to the ammeter and the battery. One can see this effect simply by starting
the car, and observing the ammeter. With
the Model A running at 1200 to 1500 RPM observe the reading of the ammeter, it
will be near the setting of the 3rd brush of the generator. If set at the example 10 Amps the ammeter
should read about 10 Amps. Now step on
the brake. The additional current to the
brake lights will reduce the charging current from 10 Amps to approximately 5
to 8 amperes [29].
Figure 7 Model A Ammeter Reading No
Lights
Turning
the headlights on will cause a large current to flow to them, about 5
Amps. This current reduces the current
flow to charge the battery as shown Figure
8 Model A Ammeter Reading with Lights On.
Figure 8 Model A Ammeter Reading with Lights On
In the
1930’s and 1940’s this trick was used by drivers to keep from overcharging the
battery. During the daylight, the driver
would start the car and drive for 10 to 15 minutes to replace the charge in the
battery due to starting. Then the driver
would turn on the headlights to reduce the charge to the battery thus helping
to not over charge the battery. In the
above example the setting of the generator 3rd brush is to give a 10
Amp generator output. Turning on the
headlights causes them to draw about 5 Amperes.
The 10 Amps divided current remaining from the generator is about 5 Amperes
and shows on the Ammeter as a 5 Amp reading.
If the
Model A owner had adjusted his generator to the 6 Amp output as recommended by
Ford in one of its service bulletins, the additional current draw of the
headlights would reduce the battery charge current to, theoretically, 1
Amp. On the other hand if you have more
current draw for the lights [30] you may be driving with the ammeter showing
discharge. This will not cause great
difficulty since even if you drive with a 5 ampere discharge for one hour the
draw from the battery is only 5 ampere hours, from a fully charged 80 Amp-Hour
battery. This will result in only a 6%
reduction in capacity. Therefore, don’t
worry too much about driving with a discharge for an hour.
If you
have a Model A with an original cutout [31]
and generator, it is possible to drive for a long distance and avoid, somewhat,
overcharging the battery by a combination of setting the generator to a lower
than 10 Amp output and using the lights as a sort of manual charge
regulator. Figure
9
Charge/Discharge Rate vs Ammeter Reading shows the relationship between 3rd Brush
settings, the charge or discharge rate and current consumed by the electrical
circuits in the Model A.
To use
the chart look to the example shown in the green lines with arrows. Observe your ammeter reading with the Model A
running at about 1200 to 1500 RPM. With
the 3rd brush set to charge at 8 Amps and the lights and other
accessories off, the ammeter reading should be about 8 Amps (assuming that your
ammeter is accurate). Now turn the
lights on. The ammeter reading will drop
to another value. In our example, the
reading is then -4 Amps. To find the
lighting load, read up from your ammeter reading on the Ammeter scale to “Load in
Amps”. Find your brush setting on the
left and read across to where the ammeter reading and the brush reading
intersect. The value in our example is
12 Amps at a brush setting of 8 Amps.
Now to find the amount of capacity loss due to this load, simply follow
the ammeter reading up to the diagonal line on the chart, then read across to
the Rate of Change in Capacity scale on the left side of the chart. In the example, the reading of -4 Amps is the
current drawn from the battery, and results in a 5% loss in capacity of an 80
Amp-Hour battery during one hour of driving with the engine RPM of over 1200
RPM. Likewise in 2 hours driving you
would remove 10% of the capacity of the battery.
Of
course you must use some judgment in using the lights as an overcharge
prevention method. If you are using the
car in a parade or driving in town with many stop lights, this is not a very
good idea. In these cases it is best to
keep the lights off, and risk some over charging.
Figure 9
Charge/Discharge Rate vs Ammeter Reading
You can
also get some idea of the amount of overcharging you are experiencing from this
chart. If you have the 3rd
brush setting at 8 Amps, then with all of the accessories and the lights turned
off your ammeter reading will be about 8 Amps.
Reading up the chart from +10 Amps on the bottom scale to the diagonal
line you can then see that the rate of overcharge, when driving at a constant
1200 RPM for one hour is 8 Amp-Hour per hour.
This means that you are putting in about 10% more charge than the battery
requires, resulting in an overcharge condition.
While
you can operate a Model A using these tools and some guessing about
overcharging, it is a better idea to provide some means of controlling the
voltage in the generator to drop the charge current to what is required to
operate the car. We will now discuss
ways to prevent overcharging automatically.
This
leaves the question; how do we know whether or not the battery is fully charged
after a trip, or has it been overcharged?
Due to the many factors involved in determining the state of charge or
overcharge, the methods available to us are:
a)
Method
1 … The “I Don’t Care Way”. I am not going to worry about overcharging,
so I simply set the generator charging rate to about 10 Amps, and plan to buy a
new battery every 2 to 3 years.
b)
Method
2 … The “Engineering Way”. Fully charge the battery, set the charging
rate to 5 Amps and drive the car in your normal pattern every day or so for 2
to 3 weeks. Use a hydrometer to check
the charge status of the battery. A
specific gravity test reading between 1.275 and 1.300 means that the battery is
fully charged, and is probably being overcharged. Reduce the charging rate to 4 Amps and repeat
the test. If the specific gravity test
shows a reading of 1.15 to 1.200 it means that the battery is not being fully
recharged and is at about ½ full charge.
Increase the charging rate to 6 Amps and repeat the test. In this manner, you will eventually reach an
understanding of what setting to make on the generator. However, this will not prevent overcharging
during a long trip or be valid if you change the driving conditions.
c)
Method
3 … The “Keep It Charged Way”. Set the
charging rate to about 6 Amps and don’t worry about summer or winter under
charging problems. Disconnect the
battery between vehicle uses and put a “battery minder” on the battery that
will ensure that the battery is fully charged when you use it again. This method will not prevent overcharging,
and reduced battery life, but it will give you some measure of “comfort”.
d)
Method
4 … The “Fix the Problem Way”
… There is a way to add a “voltage regulator” to the generator which will
isolate the generator yet prevent overcharging.
Nu-Rex makes a cutout with a “Voltage
Regulator” built into it and a version that replaces the generator brush cover
band. It looks like stock, but functions as a modern car’s regulator. To use this you either replace the cutout on
top of the generator with this device or replace the cover band on the
generator. Then set the 3rd
brush to put out a lot of amperes … 14 or more.
The device will automatically sense the voltage of the battery and
reduce the battery charge current to what is necessary. The cost is about $75 … cheap insurance for
batteries. For info see Appendix 3.
e)
Method
5 … The “Change To An Alternator way” … Finally, it is possible to eliminate
many of the problems of the old Model A .
The most high performance (and price) solution is to convert the
electrical system to use a modern alternator with a built in voltage regulator. There are two possibilities for this, keep
the positive ground 6 volt system, or change the electrical system to a more
modern 12 Volt system also eliminating the use of inverters.
Figure 10 Generator or Alternator what are the Choices?
The Figure
10 Generator or Alternator what are the
Choices? provides the various tradeoffs and costs involved
in choosing a generator or an alternator.
It is always possible to avoid overcharging your battery with both the
generator and the alternator solutions.
Your choice of methods depends on how you plan to use the Model A and
where you are in the restoration process.
There are three situations that Model A owners are usually in. Firstly, you may be starting out with a
basket case or a Model A which needs extensive restoration. Secondly, you may own an older restoration
that you drive and tinker with. Finally you may be restoring or upgrading an
older restoration or a new restoration for long distance touring. How you approach the issue of restoring,
upgrading or repairing the Model A charging and generating system depends on
you making certain choices along the way.
We now discuss the potentials for the battery and charging system in
terms of a series of decisions and tradeoffs.
The
choice of method for making the Model A charging system trouble free depends on
your objectives for your car. There are
two basic paths for updating your Model A, authentic versus performance. The “authentic” path keeps the Model A
looking like what Henry designed and uses the generator as its building
block. The “performance path”, installs
a modern vehicle alternator, and gives increased charging, as well as a path to
the conversion to +12 Volt operation. If
you are going to have to replace the generator anyway, the costs involved are
approximately the same. All “authentic” path solutions meet MARC and MAFCA
judging standards, while alternator versions do not. Both the “authentic” and
the “performance” paths can provide automatic overcharge protection. The
following paragraphs describe your choices.
A new
restoration of a Model A may be for “show” or for hobby driving. The choice of charging system for the “show”
car is only one. To show the car for
points in the MAFCA or MARC competitions you must have a generator. You have some decisions that you can make
about cutouts and voltage regulators, but you will have to stick to the
positive grounded 6 Volt battery and a generator. The car which is being restored for “hobby”
driving has a wider choice of possibilities.
The first decision you will have to make is whether to use a generator
or an alternator. This decision depends
on how authentic you want the Model A to “look” when you lift the drivers side
engine compartment hood. An alternator
cannot be made to look like a Model A generator/cutout assembly. If you have a good generator, and want to
retain the “authentic” look, and
you are not going to use a lot of +12 Volt accessories you may want to stay
with the good old generator. On the
other hand you may want to upgrade your electrical system to have brighter
lights, no charging problems, and have a larger variety of +12 Volt
accessories, such as high power CB and FM radios, CD players, and even air
conditioners available while driving. In
this case, you will want to use an alternator.
You may
have an older restoration, which needs to have its generator or generating
system replaced, or you want to use your old generator but avoid
overcharging. On the other hand, you may
simply want to upgrade the generating system for more performance, or to use
more 12Volt accessories. If you choose the “authentic” path you need
to make a decision between the amount of “authenticity” you desire. For the “purest” Model A enthusiast, choose the “I don’t care
about overcharging” path and select the stock generator with a stock
electro-magnetic cutout. If you are not
completely a “purest” you can choose a diode cutout to eliminate sticking
contacts. On the other hand, if you want
the stock look, and want to prevent battery overcharging choose the path that
eliminates 3rd brush adjustments and install a voltage regulator.
Some
Model A owners will be building a “touring” Model A from scratch, or may be
upgrading an older restoration to use for long distance touring. While you can still choose the “authentic”
path as discussed above, and can choose a generator with a voltage regulator,
it will have limited performance to provide you with long distance touring
needs. Most builders of long distance
touring Model A’s want high performance, reliability, and elimination of electrical
problems. The solution to this is to use
an alternator. There is a basic choice
you must make when contemplating adding an alternator. You must choose between the use of the Model
A positive ground 6 Volt system, or conversion to a negative ground 12 Volt
system. Both of these will give better
performance, brighter lights, and increased charging capability. The advantage of a 12 volt system over
keeping the 6 Volt system is better component ground reliability, increased
accessory convenience, and elimination of the need for an inverter.
Battery Voltage
Batteries
are nominally rated at either 6 or 12 Volts, however, the actual battery
voltage will vary during the charge and discharge cycles under load. The no load, open circuit voltage of a 6 Volt
battery is actually about 6.3 Volts. A
12 Volt battery’s open circuit voltage is about 12.7 volts.
The
actual Model A battery voltage during discharge will vary depending on several
factors, including state of charge, applied electrical load, battery temperature
and electrolyte specific gravity. The
largest load applied to the battery is the starter motor. The voltage of a 6 Volt Model A battery
during starting will be below 6 Volts as shown in Figure
1 Battery Voltage to Starter vs. Engine
Turning Rev/Sec. The
starting voltage will be below 6 volts and can drop to as much as 5 volts under
adverse conditions. Below 4.5 Volts the
Model A will probably not start.
State of Charge versus Battery
Voltage
Temperature
and state of charge has the most influence on the ability of the battery to
supply the necessary power to the Model A starting motor. The power that is
able to be applied to the starter motor is both dependent upon the voltage
available at a certain temperature and the conditions of the connections
between the starter to the battery and the battery to ground. As the temperature goes down the amount of
power required to turn the engine goes up, and at the same time the available capacity
of the battery to supply this power goes down.
These two factors work together to ensure that a weak battery will fail
to start the Model A Ford in winter conditions.
Open
circuit voltage of lead-acid batteries vary with temperature, electrolyte
specific gravity and state of charge. The
following table lists open circuit voltage as a function of the state of
charge.
|
State
of Charge
|
Open
Circuit Voltage 12V Battery
|
Open
Circuit
Voltage
6V Battery
|
|
100%
(SG = 1.28)
|
12.65
|
6.32
|
|
75%
|
12.45
|
6.22
|
|
50%
|
12.24
|
6.12
|
|
25%
|
12.06
|
6.03
|
|
0% (SG = 1.1)
|
11.89
|
5.95
|
Poor
battery connections can contribute to difficulty in starting the Model A Ford,
especially if you have a 6 Volt system.
Bad connections are generally the fault of having corrosion at the
terminals of the battery. Batteries
outgas during the charging cycle, causing a gas to escape. This gas interacts with the lead terminal
posts to form a white lead oxide which is an insulator, reducing the capability
of the terminal to transfer high starting currents. In addition, the gas interacts with the
copper wires in the cable to the starter also deteriorating the ability of the
cable to carry the current. These bad connections
can reduce the battery voltage by ½ Volt or more. This means that the ability of the car to
start in cold weather is reduced approximately as shown Figure
11 Effect of Bad Connections on Starting. This chart
is not necessarily a worst case condition and is provided as an illustration.
The loss
of battery voltage that can be applied to the starter motor due to bad
connections causes the starter to need more amperage to turn the engine. The effect is to shift the starter motor
performance versus temperature curve to the left. The above chart has been constructed assuming
that the connection causes a ½ volt degradation in battery voltage during the
cranking cycle. These bad connections
can cause up to an apparent 40 degree shift in the temperature that the engine
can be started at. While a Model A with
GOOD connections can be easily started at about 32 degrees F, one with POOR
connections may have difficulty in starting below 50 degrees F.
Figure 11 Effect of Bad Connections on Starting
The
obvious solution is to clean and tighten all connections. In “Henry’s days” it was recommended that the
terminals (after tightening) be coated with vasoline.
[32] While you can still do this, the gooey mess
may be avoided by using modern sprays and/or anti-corrosion compounds available
at most auto parts stores. It is
important to check the conditions of the starter cable, by pealing back the
insulation and checking for green and white deposits on the cable copper wire. Replace the cable if there are signs of
degradation.
A good insurance
to assure a good, high current, connection to the starter is to add a 19 inch
long #4 gauge battery cable from ground
connection of the battery on the frame to a bolt on the transmission. A good discussion of this is shown in Les
Andrew’s book [33].
While it
is not applicable to the Model A, the following discussion is provided for
reference.
You can
use two batteries to gain more electrical power by wiring the batteries in
parallel or in series.
Figure
12
Batteries in Series
As shown
here, two 6 volt batteries can be
connected in series to form a 12 Volt battery with double the capacity of one
of the batteries. In this case a
charging system is required which will charge the two batteries as a 12 Volt
system. Alternatively, you can remove
the batteries and charge them individually as 6 Volt batteries. Be sure to select batteries of the same
voltage rating.
On the
other hand you can get more electrical capacity by connecting batteries in
parallel.
Figure
13
Batteries in Parallel
As shown
here the two batteries continue to deliver electrical current at 6 Volts,
however, the capacity of the system is doubled.
One thing to remember is that if one battery is weaker than the other or
two unequally charged batteries are
connected in parallel, the stronger of the two will discharge into the weaker
battery until an equilibrium is obtained.
Battery Ratings
There
are a number of battery ratings used to provide sizing information to consumers
who are buying replacement batteries for automotive use. These ratings, while important in a relative
sense, are not absolute in their application to real situations.
Battery Capacity Ratings
Power
ratings are important to understand how to size your battery. To better understand battery capacity one
must understand some basic terminology.
The electrical current flow to or from a battery are measured in amperes
or “amps”. For a battery, the most
important number is the “amp-hours (AH) rating”. This means, in theory, that if you had a
battery with a 80 AH rating and the load drew a steady 4 amperes, the battery
would discharge in 20 hours. However,
this rating is only useful in a relative sense.
Real batteries are not this efficient.
For example, as the battery discharges the voltage will remain steady
for only a small percentage of the time, then will drop in an ever increasing
amount as the battery discharges, causing the load to demand more current. The battery will discharge at a constant rate
for only a period of time, then more rapidly at the end of the discharge
cycle. In fact, a fast discharge rate,
will cause the battery to produce much less effective power capacity. For example, the same 80 AH battery which
fully discharges in 4 hours may only deliver a portion of its available power
capacity. Peukert’s
Law, developed by W. Peukert in 1897, states that the
“real” capacity for a battery decreases as the current drawn from the battery
increases. A discussion of Peukert’s Law is found in Appendix 2.
Ampere-hours
(A·h) is the product of the time that a battery can
deliver a certain amount of current (in hours) times that current (in amps),
for a particular discharge period at a specified discharge current. This is one
indication of the total amount of charge a battery is able to store and deliver
at its rated voltage.
Historically,
battery manufacturers have stated their capacity in Amp-Hours for a constant
discharge rate of Amp-Hours/20. This means that an 80 Amp-Hour battery is
typically rated to deliver this capacity with a constant discharge current of
80/20 = 4 Amps. However, be careful …
the manufacturers may state different values of current, or more usually, none
at all [34].
Battery Reserve
Capacity
Another
rating that you see on some automotive batteries is Reserve Capacity (RC)
. This is defined as the time in minutes
that at a specific temperature a fully charged
battery can be discharged at a specific amperage before its voltage
drops to a certain value. Typically,
this is shown as the reserve capacity (RC in minutes) at 80 degrees Farenheit that the battery can be discharged at 25 amperes
before it reaches 10.5 Volts (for a 12 Volt battery). This rating is rarely stated.
Battery Cranking
Ratings
Cranking
Amperes (CA) is used to compare batteries and indicates the number of amperes
that a fully charged 12 volt battery at 32 degrees Farenheit
can deliver for 30 seconds and maintain at least 7.2 Volts. For a 6 volt
battery this is the number of amperes that the battery can deliver at 32
degrees Farenheit for 30 seconds and still maintain a
voltage of 3.6 Volts.
Cold
Cranking Amperes (CCA) are used to compare automotive batteries and indicate
the number of amperes a fully charged 12 Volt battery can deliver at 0 degrees Farenheit for 30 seconds and maintain at least 7.2 Volts.
For a 6 volt battery this is the number of amperes that the battery can deliver
at 0 degrees Farenheit for 30 seconds and still
maintain a voltage of 3.6 Volts.
Hot
Cranking Amperes (CCA) are used to compare automotive batteries and indicate
the number of amperes a fully charged 12 Volt battery can deliver at 80 degrees
Farenheit for 30 seconds and maintain at least 7.2
Volts. For a 6 volt battery this is the number of amperes that the battery can
deliver at 80 degrees Farenheit for 30 seconds and
still maintain a voltage of 3.6 Volts.
There
are three basic automotive batteries available on the market today. Conventional flooded electrolyte, absorbed
glass mat, and gelled electrolyte also called gel-cells. This section describes
these types and provides information on what is good and bad about each.
Flooded
Electrolyte type batteries are the oldest and most common batteries in
automotive use. The original Model A
Fords were manufactured and delivered with these type batteries. These batteries contain a mixture of about
90% water and 10% sulfuric acid. They
provide good capacity at a reasonable price.
They come in two sub-types, those with removable caps that require
periodic refilling with water, and those newer versions called “maintenance
free”. The non-maintenance free original
flooded electrolyte batteries are lead-antimony types that require periodic
checking and refilling with water to maintain their electrolyte level. You should use distilled water to prevent a
buildup of minerals in the battery case.
The
newer “maintenance free” batteries (easily discernable because they do not have
removable caps) are lead-calcium types.
These so called maintenance free batteries use less water (but still
some), as they are designed to run low on water about the time that they are
worn out. These “maintenance free”
batteries, when used in hot weather and/or are frequently deep discharge cycled
will use more water, and may be weakened or ruined in these situations due to
the electrolyte levels dropping below the top of the internal lead plates. Model A owners that do not have a voltage
regulator should avoid maintenance free batteries since overcharging will cause
them to “boil out” quicker, thus fail sooner.
On the “good” side of maintenance free flooded electrolyte batteries, they usually vent less fumes, and
therefore have lower rates of corrosion at the battery terminals.
For more
information visit www.interstatebatteries.com
or www.exidebatteries.com
Absorbed
Glass Mat (AGM) type batteries don’t require water since their electrolyte is
absorbed in a silica glass matting wrapped around the internal lead
plates. AGM batteries are vibration and
maintenance free, however, are quite pricey.
They generally, deliver higher power and efficiency than gel cell or
flooded electrolyte types. This battery type looks more like a Model A
battery. None of the Model A mail order
parts suppliers offer AGM batteries.
For more
information visit www.dekabatteries.com
Gel type
batteries contain a jellied electrolyte rather than a liquid. Gel cell batteries usually don’t require any
water, but if they are discharged at too high a rate, they will lose some
electrolyte through out gassing, and will have shortened life. Gel cell batteries are more tolerant of being
left partially discharged and they do not self-discharge fast. However, they do not tolerate repeated deep
discharge cycles. Gel types require
slightly different charging voltages and therefore are more difficult to
install and keep charged with typical automotive charging systems. Gel cell batteries cost substantially more
than the lead acid types. This battery
looks “space age” being constructed as either 3 or 6 cylinders not as a square
box. For the Model A owner, this battery
type requires a different battery hold down top plate, further increasing the
price. The gel cell batteries are
offered by some of the Model A parts suppliers.
For more
information visit www.optimabatteries.com
The
automotive battery is somewhat different than other storage batteries, in that
its main load is a quick discharge at high amperages during the starting of the
vehicle, followed by a rather slower recharge cycle. This demand is especially hard on the Model A
battery, since it has an inefficient 6 Volt operation, and poor recharge
capability and the problem of overcharging unless you have a voltage regulator.
In
normal automotive service a modern vehicle's engine-driven alternator powers
the vehicle's electrical systems and restores capacity, used from the battery
during engine cranking, while driving. As discussed above in the section on the
“Original Model A Battery” the potential to recharge the Model A battery may be
limited due to starting conditions, mainly temperature. For the Model A Ford, the original charging
system may be deficient when the vehicle is used in winter weather at
temperatures below 0 degrees F. Modern
alternators can supply a large current to recharge the battery quickly during
cold weather, thereby eliminating the problem of cold weather operation.
The
ability to discharge and recharge flooded electrolyte lead-acid batteries can
be limited by battery aging. The main
two problems of battery life are, lack of electrolyte due to evaporation, and
over charging. Modern battery chargers
can be purchased with “taper” charging or two level charging which reduce the
charging levels as the battery approaches full charge.
When
installing a new battery or recharging a battery that has been accidentally
discharged completely, one of several different methods can be used to charge
it. The most gentle of these is called trickle charging. Other methods include
slow-charging and quick-charging, the latter being the harshest. Typically, automotive battery chargers used
for recharging batteries that have been discharged do not have an auto – float
charging feature and are not useful for maintenance charging.
Maintenance
charging when the battery is in storage is best accomplished by a “maintenance”
charger sometimes called a “battery minder”.
These devices have a feature called auto – float which only provides a
small charge when the battery needs it.
Battery Charging Voltage Set Points
Different
battery types have different charging voltage set points and auto-float charge
voltage settings.
|
Type
of Battery
|
Charge
Voltage Set Point
|
Auto-Float
Charge Setting
|
|
Flooded
Electrolyte 6 Volt
|
7.1 –
7.3
|
6.6 –
6.8
|
|
Flooded
Electrolyte 12 Volt
|
14.2 –
14.6
|
13.2 –
13.7
|
|
AGM 12
Volt
|
14.1 –
14.4
|
13.2 –
13.4
|
|
Gel
Cell 12 Volt
|
13.8 –
14.0
|
13.2
|
Battery Charging Current Rate
For best
battery life, batteries should not be recharged at a rate exceeding 20% of
their AMP-Hour rating. The Model A 6
Volt battery is typically rated at 80 AMP-Hour so it should be charged at a
maximum rate of 16 Amps. Using a lower
charge rate is preferred if you can spare the time.
When
storing a battery for the winter, a charger with an auto – float charging
feature should be used. A typical
maintenance type charger for a 12 Volt battery will provide a charge rate of
about 1.5 to 2 Amps until the battery voltage has reached 14.4 volts (on
average). At this point the internal
reference of the charger will change to maintain the battery voltage at 13.2
Volts (on the average). At this lower
voltage, a charging current of a few milli-amperes is
provided constantly to the battery. At
this condition, most batteries can be left charging indefinitely. Usually, maintenance battery chargers have
some internal electronic current needs, and do not have a on-off switch,
therefore do not leave these devices connected to the battery when unplugged
from the 110 Volt home electrical supply or the battery will discharge.
Battery Chargers
Many
battery chargers available have switches that allow charging of both 6 Volt and
12 Volt automotive batteries. Many
chargers have switches which allow a high charge rate and a low charge rate
such as 15 Amp and 5 Amp. The best
charging solution is to use a multi-stage charger with an automated charge
regulation that keeps recharging time to a minimum, but prevents
overcharging. If you are going to use a
gel cell or an AGM battery choose a charger which can provide the proper
charging voltage set point.
Battery Maintenance Charger System for the Model A
A simple
battery maintenance charging system can be added to a Model A Ford to make it easy
to connect the maintenance charger when it is garaged for a week or a month
between tours. A simple system is shown
in Figure
14 Easy Maintenance Charger Installation
A
battery disconnect switch is installed at the negative terminal of the battery,
to isolate the Model A from the maintenance charger ( a good safety item to
have anyway). Then two wires are routed
to a plastic bracket which will insulate the negative terminal from the Model
A. The two studs make an easy place to
connect the leads from the maintenance charger.
To operate, simply turn the battery disconnect switch to OFF, and
connect the clamps to the studs, plug in the maintenance charger and your done!
To
install a battery disconnect switch refer to Les Andrews book. [35]
Alternatively
battery disconnect switches that attach directly to the battery can be
purchased at WalMart inexpensively, however can
require some additional cables and brackets to attach to the Model A without
interfering with the battery hold down. In addition, to be effective, it is
important to make the disconnect easy to use.
Since
the terminals are always “hot” be careful that they cannot be shorted. Also, these terminals provide a convenient 6
Volt connection for accessories.
Figure 14 Easy Maintenance Charger Installation
While
most Model A owners do not have a power converter in their Model A, many of us
also have Recreation Vehicles. An RV may
be in the form of a trailer, a 5th wheel, or a motor home. If the RV is a motor home, it typically
combines the function of engine starting with 12 Volt power to the remainder of
the RV. For trailers and 5th
wheels, they typically have a separate deep cycle battery system with two or
more batteries in parallel to provide more capacity. The RV usually has an Inverter which changes
12 volt DC battery power into 120 Volt AC power and may combine this with a 110
Volt to 12 Volt power converter for converting the RV park electricity input to
12 volts necessary to power the lights and other features. Many of these have the ability to recharge
the 12 Volt batteries in the trailer or 5th wheel while plugged into
an external 110 Volt source. Be sure
that these are not simply trickle chargers running at 2 to 5 Amps, but have an
auto – float feature to prevent overcharging.
If the RV’s power pack does not feature an auto – float maintenance
charger, and if you are not going to use the RV for two weeks or a month, you
can simply disconnect the battery from the power pack, and connect an external
auto – float maintenance charger. During
the winter, when the RV is stored outside for several months, it is best to
remove the batteries and put them in the garage on a maintenance charger with
auto – float.
One
convenient system, usually not provided by the manufacturer, is shown below.
Figure
15
RV Battery Storage Operation
I
installed a 110 volt connection in the battery storage compartment and a quick
battery disconnect that you can buy at Walmart or an
automotive parts supply retailer. The
battery switch (about $15) is attached at the input to the battery system and
is connected to the supply cable coming from the RV power pack. This simple modification allows you to not
overcharge your RV battery while the RV is not being used for a month or
so. I keep a 12 Volt maintenance charger
with auto – float in my storage compartment.
If I am not going to use the RV for two weeks or a month, I simply plug
the RV into an external 110 Volt supply (my house wiring), turn the battery
disconnect off, and dig around in my storage bin for the maintenance
charger. It only takes a minute or two
to connect the maintenance charger and I am then confident that I will not be
having to buy two expensive batteries, due to overcharging, in the near
future. Just remember to disconnect the
maintenance charger and turn the battery switch to ON before the next trip.
Proper
care and maintenance can extend battery life.
Here are a few things you can do to extend the life of your Model A
battery. For more detailed information
see the discussion of Battery Life.
·
Always
recharge a discharged battery as soon as possible
·
Be
sure to check and replace water in non-maintenance free batteries regularly
·
If
you are not going to drive the car for a couple of weeks, a month, or longer connect a
maintenance charger (not a battery charger or a so called trickle charger – See
Automotive Battery Operation for more information)
·
Never
leave a battery at a low state of charge for a long period
·
Remove
the battery from the car in the winter, when it is not being driven and connect
a maintenance charger to the battery.
(See Battery Maintenance for more information)
·
Do
not leave a battery with a low state of charge in an unheated garage where they
can freeze. A fully charged battery can
survive temperatures well below zero.
·
Clean
all connections with sand paper, and keep tight.
·
Apply
anti-corrosion protection to battery terminals.
·
Replace
any corroded battery cables.
Battery Safety
Procedures
Batteries
can be dangerous. Flooded Electrolyte
Batteries (lead-acid types) contain sulfuric acid, which damages almost
anything it touches. If you are adding
electrolyte to a new uncharged battery use eye protection, rubber gloves, and
old clothes. Use baking soda and water
to neutralize any spilled acid.
Avoid
sparks. It is possible for the battery
to explode, causing a fire, destroying your Model A, and causing personal injury
or even death to you. Batteries vent
hydrogen and oxygen gases during normal battery operation, which can explode if
sparks from loose connections, jumper cables, or smoking occur nearby the
battery. Especially, when charging, near
the end of the charging cycle, you will notice that the electrolyte in the
battery is bubbling. This means that
much gas is being liberated from the electrolyte and this time is especially
dangerous. If you are within an enclosed
space use a fan to circulate the air around the battery.
The
following precautions should be used when working with your battery in or out
of your car.
·
Someone
should be within range of your voice
·
Have
plenty of water and soap nearby incase battery acid comes in contact with your
skin, clothing or eyes. If battery acid
contacts your skin, immediately wash with soap and water, and flood the area
with running cold water for at least 15 minutes, then seek medical attention.
·
Wear
eye protection, and avoid touching your eyes when working near the battery
·
Never
smoke or allow a spark or flame in the vicinity of the battery
·
Never
attempt to charge a frozen battery.
To
prevent sparks and reduce the probability of a battery explosion during work on
the battery, especially if you are going to remove it from the car, do the
following;
·
Keep metal tools from dropping on the battery, which can cause a spark if it
contacts both the positive and negative terminals.
·
TURN
OFF ALL ACCESSORIES AND SYSTEMS IN THE CAR, to prevent current draw from the
battery when loosening or removing the battery terminals.
·
Remove the Grounded Terminal of the Battery first, since any current flowing to
devices turned on will reduce the probability of sparking.
·
DISCONNECT
THE GROUNDED TERMINAL OF THE BATTERY WHEN WORKING ON THE MODEL A’s ELECTRICAL
SYSTEM. If you are going to do some work
on the car, or just want to disconnect the battery to keep it from draining,
use the grounded terminal NOT the starter cable to disconnect the battery.
Safety
precautions should be used during charging of the battery, either in or out of
the vehicle.
·
BE
SURE THE AREA AROUND THE BATTERY IS
VENTILATED. The battery gases can be
blown away by a fan if necessary
·
ADD
DISTILLED WATER TO THE RECOMMENDED LEVEL.
This helps purge gas from the cells.
Do not overfill.
·
PUT
THE CHARGER AS FAR FROM THE BATTERY AS THE CABLES WILL ALLOW. Never place the charger near or above the
battery. Do not sit the battery on top
of the battery!
·
CONNECT
THE BATTERY TO THE CHARGER BEFORE CONNECTING THE CHARGER TO
THE 110 VOLT AC SUPPLY. Connecting the
AC supply last will prevent sparking at the battery terminals.
·
WHEN
DISCONNECTING THE CHARGER, DISCONNECT THE AC SUPPLY FIRST, THEN DISCONNECT THE
GROUNDED TERMINAL, THEN FINALLY THE POSITIVE
(negative for the Model A) TERMINAL.
Battery Testing
We live
in a throw away society and you may never need to test a battery. However, to make this report complete I will
list methods you can use to test a battery to gauge its ability to perform. These testing methods are specific to a
flooded electrolyte (lead acid) battery.
Battery tests can be made to determine
the state of charge, if the battery is worn out, and to reveal the amount of
remaining life. [36]
The
state of charge can be tested by measuring the specific gravity or by measuring
the open-circuit voltage of the battery.
(1)
Open
Circuit Voltage Test
To
do this test a volt meter with a range that includes the standard voltage of
the battery, 12.7 Volts for a 12 Volt battery and 6.3 Volts for a 6 Volt battery. A digital volt meter that reads and displays
voltage with an accuracy of 0.01 is preferred. To make the measurement place
the volt meter probes between the individual cells of a fully charged battery. If there is no access to the individual cell
terminals, this test cannot be performed.
A recently charged battery will have a “surface charge” giving an
abnormally high reading. To avoid this
abnormal reading, dissipate the surface charge by turning on the lights of the
car for a few minutes. Alternatively, you can wait an hour after charging the
battery. With the volt meter connected
across the terminals of the cells, the reading should be 2.05 to 2.15
volts. Between 2.03 volts and 2.05 volts
the battery needs more recharging. Below 2.03 volts the battery needs
recharging.
Applying
the volt meter across the battery from the + terminal to the – terminal we can
get a “quick” look at the battery state of charge. This test is not conclusive since one of the
cells may substantially lower than the others or failed. However, a reading of 6.15 to 6.45 volts
means that the battery is fully or nearly fully charged. A reading between 6.09 and 6.15 means the
battery may need charging. Below 6.09
Volts the battery needs recharging.
(2)
Hydrometer
(Specific Gravity) Test
To
do this test you will need a hydrometer.
They can be purchased from auto supply stores. You cannot do this test on a maintenance free
battery, since you will not have access to the electrolyte. Do not make this test after water has been
added to the battery, since the water will float on top. Remove the vent plugs and draw some
electrolyte into the tube to cause the float to rise in the tube. Read the
specific gravity on the scale. Note the
temperature of the sample and use the compensation table to get the specific
gravity. After noting the specific
gravity compress the bulb and return the sample to the battery. Batteries with compensated readings of 1.250
to 1.295 with a variation between cells of less than 0.015 is considered fully
charged. If the reading is 1.225 to
1.250 the battery should be recharged.
If below 1.225 the battery should be further tested to check if it is
worn out and needs replacing.
Battery Capacity Testing
Batteries
were capacity tested as a routine matter in the 1930s through the 1950s. While not in vogue in this “throw away
society” we live in, many of the old methods and equipment still exist. If you have an antique “Battery Capacity
Tester” you can make the test with the outside the car. If you do not, a subjective cranking test can
be accomplished.
(1)
Testing
with a Battery Capacity Tester
There
were several different types of battery test equipment available. Some were built into battery chargers and
others were hand held devices. Some just
had “good”, “poor”, or “replace” colored bands.
Others showed percentage of capacity remaining. In all cases, the test was not all that
accurate, but instead gave a relative reading.
In the “old” days if the tester showed “poor” or about 60% capacity
during the test, it was probable that the car would not start in cold
weather. Basically, the capacity tester
consists of a carbon pile rheostat which can be adjusted to discharge the
battery at a predetermined rate, and an ammeter to read discharge rates, and a
volt meter to read battery voltage. The
rheostat setting is selected for the battery design used, and was determined by
the battery amp-hour rating. Typically,
this meant that the discharge rate was 25 times the number of positive plates
in the battery. The Model A had 13
plates, of which 7 were positive. Thus
the discharge rate for the tester would be set at 175 Amps. A resistance of 6 divided by 175 = 0.0348 Ohms would give the test adequate
discharge.
With
the setup in place, connect the tester across the battery terminals. The meter reading should hold 5.4 volts for a
battery in good condition. If the
battery reading is below 5.4 volts but above 5 volts the battery has lost up to
40% of its capacity and should be replaced.
Keep the tester connected for a few seconds, if the tester shows
initially good, then drops back rapidly the battery is defective and will need
replacing. If the tester voltage shows
less than 5 volts the battery needs replacing.
(2)
Capacity
Test While Cranking the Engine
Ok,
what if you don’t have a battery test setup?
A capacity test can be made on the Model A with the battery in the
car. To make this test a volt meter is
required. A digital volt meter that reads and displays voltage with an accuracy
of 0.01 is preferred. Run the car until
the temperature is in a normal operating range.
Turn the ignition switch to OFF. [37] With the volt meter connected across the
battery terminals, crank the engine for about 30 seconds. If the engine cranks at a good speed and the
voltage does not drop below 5.4 volts the battery can be considered to be in
good condition and at or nearly at full charge.
If the voltage is below 5.4 volts and especially if it approaches 4.5
volts the battery capacity may be low and the battery may need replacing. However, it also may mean that the battery
state of charge is too low, or that the battery terminals are corroded, or
other problems, such as a faulty starter.
Battery Charging in
the Vehicle
The 6
volt positive grounded battery in the Model A can be charged while in the
vehicle. There are two ways to
accomplish this. The safest method is to isolate the battery from the car, and
connect the charger directly to the battery.
A less safe, but quick method is to connect the charger to the starter
input bolt and a bolt on the engine.
This approach avoids removing the floor boards.
The
safest method is to remove the horizontal floorboard just in front of the
driver’s seat. Then disconnect the
positive ground cable to the frame, and then the negative cable to the starter.
Figure
16
Safely Charging the Battery in the Vehicle
With the
battery isolated, connect the charger with the positive cable to the positive
terminal and the negative cable to the negative terminal on the battery. Be sure to observe the safety considerations
when connecting the charger to the battery.
Open the windows and the doors of the Model A before connecting the
cables to vent any gases. Check the
battery electrolyte level, and top off any low electrolyte level cells with
distilled water. Connect the positive
charging cable first, then the negative cable, and finally plug in the battery
charger.
The 6
volt positive grounded battery can be charged without removing the floor
boards, by connecting to the starter terminal located in the engine compartment
near the steering column. This means
taking precaution to turn OFF any accessories, lights, and the ignition. Care must be taken when connecting the
NEGATIVE charging cable to the starter bolt, to ensure it does not get grounded
on the starter push rod or the steering column.
Wrap electrical tape over portions of the clamp which can become
grounded.
When
jump starting the Model A be careful to not create sparks near the
battery. Use a heavy wire jumper cable
set since 100 to 200 Amps will be flowing through them. For a positive grounded Model A (the stock
arrangement) use another Model A with a 6 Volt battery. The use of another Model A may not work. [38] There is so much current flowing through the
jumper cables that the voltage drop due to too small of jumper cable wire
causes the starter motor to turn too slowly.
In this case use a modern car with a 12 volt battery. It will not be necessary to start the modern
car. Make sure that the terminals are
correctly connected according to polarity.
The following procedure should be used for connecting the two Model A’s
or a modern car to a Model A, to perform
the jump start. Since the battery is under
the floor boards and not easily available, we can use the starter terminal on
the driver’s side of the Model A to connect the jumper cables.
·
Connect
the “good Model A” cables first. Connect
the NEGATIVE Jumper cable to the starter
terminal. Be sure to wrap some
insulating material, heavy cardboard, or plastic around the clamp to ensure
that the clamp does not contact the starter push rod, or the steering
column. Then connect the POSITIVE Jumper
cable to a clean (not painted) portion of the Frame or to an engine bolt.
·
Now
connect the “Model A needing starting”.
Connect the NEGATIVE Jumper cable to the starter terminal. Again, be
sure to wrap some insulating material, heavy cardboard, or plastic around the
clamp to ensure that the clamp does not contact the starter push rod, or the
steering column Then connect the POSITIVE Jumper cable to a clean (not painted)
portion of the Frame or to an engine bolt.
·
After
starting, remove the cables in the reverse order to the above paragraphs.
For a 12
Volt NEGATIVE grounded system (modern vehicles) just reverse the procedure;
·
Connect
the “good vehicle” cables first. Connect
the POSITIVE Jumper cable to the battery
(+) terminal. Then connect the NEGATIVE
Jumper cable to a clean (not painted) portion of the Frame or to an engine bolt
well away from the battery.
·
Now
connect the “Vehicle needing starting”.
Connect the POSITIVE Jumper cable to the battery (+) terminal. Then connect the NEGATIVE Jumper cable to a
clean (not painted) portion of the Frame or to an engine bolt well away from
the battery.
Battery
Storage
The best
approach is to remove the battery from the car and connect it to a maintenance
charger. Keep the battery cold, storage
in an unheated garage is preferred to storage in a heated basement.
When
connecting one or more batteries to a maintenance charger use the following
procedure.
·
Charge
each battery fully. If the battery has
been in the car recently simply connect it to a maintenance charger. If the battery has been sitting for a month
or two, charge it with a battery charger before connecting the maintenance
charger.
·
Connect
the batteries in parallel (that is plus terminal to plus terminal and negative
terminal to negative terminal) using cables with alligator clips. It is not necessary that these cables be
heavy, any 12 or 14 gauge wire will do.
·
Connect
the maintenance charger to one of the end batteries observing the proper
polarity.
·
Plug
in the maintenance charger to a 110 volt AC supply.
·
The
maintenance charger current will be a few hundred milliamps. Check the charger for multiple battery
charging.
The
following data has been gleaned from various catalogs and by checking retail
stores.
(1)
Shipped
DRY – No electrolyte included (you must do this yourself)
(2)
Shipping
Charges Extra $10 to $36 depending on retailer
(3)
Requires
a different battery bracket top piece at $15 each.
From Wikipedia, the free encyclopedia on the web at
Wikipedia.com
Peukert's Law, developed by the German
scientist W. Peukert in 1897, expresses the capacity
of a lead-acid battery in terms of the rate at which it
is discharged. As the rate increases, the battery's capacity decreases,
although its actual capacity tends to remain fairly constant.
Peukert's law is as follows:
where:
C is the capacity according to Peukert, at a one-ampere discharge rate, expressed in A·h.
I is the discharge current, expressed in
A.
k is the Peukert
constant, dimensionless.
and
t is the time of discharge, expressed in
h.
However,
more commonly, manufacturers rate the capacity of a battery with reference to a
discharge time. Other researchers have
extended Peukert’s Law to use Amp Hour ratings. Therefore, the following equation should be
used:
where:
H is the hour rating that the battery is
specified against
C is the rated capacity at that
discharge rate.
I is the expected discharge rate in Amps
Note
that no longer Cp appears in this equation, which is good since
battery manufacturers do not provide this rating.
For
example; take a typical Model A battery. The Model A lead acid battery
typically has a Peukert’s Constant of 1.3 and has a Amp-Hour rating of 80. AH.
For an
ideal battery, the constant k would equal one, in this case the actual capacity
would be independent of the current. For a lead-acid
battery, the value of k is typically between 1.1 and 1.3 however. The
Peukert constant varies according to the age of the
battery generally increasing with age.
Technical Applications
Peukert's Law cannot be applied across different
battery chemistries, or even from one battery structure to another in the same
chemical class. The Peukert factor for a particular
battery chemistry and stucture can only be used to
predict performance within that group of batteries.
Example
1
Given a
Lead Acid class of battery that has been previously tested to determine a Peukert's Exponent of 1.3 you can make the following
calculations to determine the possible performance at different discharge
rates.
At an
advertised rate of 200 Ah the battery will produce 200 A·h
over a constant period of 20 Hours. Simply put, the battery was designed to
discharge at the rate of 10 Amps for 20 Hours. Amps (10) times Hours (20)
equals Amp Hours (200).
Since
everyone sees battery capacity as somewhat likened to water in a glass, one
might want to think that the A·h capacity of a
battery would remain constant while the time and discharge rate remained
connected in a linear fashion. This is not the case. Given this same battery under a load of 20A
you would think that it would operate for 10 Hours, but it will not, it will
operate for only 8.1 Hours. The resulting Ah rating falls to 162.5Ah. An
apparent loss of 37.5 Ah or 18.75%. This is the effect of Peukert's
law on this particular battery chemistry and structure.
Now we
have a new starting point. 20A for 10 Hours. If we double the discharge rate to
40A can we expect to see a predictable loss of 18.75%? At 40A we would expect
our Peukert adjusted 162.5 A·h
battery to operate for 4.06 Hours. Since we already experienced a loss of
18.75% in the first test, after doubling the discharge rate, lets adjust our
capacity in this test to see if it falls in line. 18.75% of 162.5Ah is 30.47 A·h. Subtracting this from 162.5 A·h
leaves us 132.03 A·h. How close to the mark is our
"guestimate"? Pretty darn close. In
actuality the battery will test out at 131.96 A·h.
Now we
have a new mark, a 40A discharge rate produced 132.03 A·h
on paper, and very close to that in the real world. If we go to 80 Amps can we
expect the same loss of 18.75% from the Peukerts
adjusted 132.03 A·h battery? Mathematicaly
we should see 107.29 A·h. In the real world you will
see 107.18 A·h. Nearly on the mark!
You can
now simply create points on your graph for any given battery by testing once,
and then extrapolating using the above process.
Note that this holds for lead-acid batteries and not other types.
References
W. Peukert, Über die Abhängigkeit der Kapacität von der Entladestromstärcke bei Bleiakkumulatoren, Elektrotechnische
Zeitschrift 20 (1897)
D. Doerffel, S.A. Sharkh, A critical
review of using the Peukert equation for determining
the remaining capacity of lead-acid and lithium-ion batteries, Journal of Power
Sources, 155 (2006) 395–400
Voltage
or Current regulators can be used to reduce or eliminate overcharging in a
Model A battery. These devices are
available from various Model A parts suppliers.
This report has not evaluated any of these devices and only provides
information that the parts suppliers have in their catalogs.
In
addition, to prevent overcharging, you can replace your stock Model A generator
with a modern alternator. Model A parts
suppliers can provide you with these devices.
There are a couple of ways to go if you are going to make this
substitution.
There
are a couple of types of these devices available.
This
type keeps the Model A generator and cutout “pristine”. It keeps the look and operation of the
generator and cutout the same as the stock version. What you do is purchase a replacement
generator band (the cover that goes around the back portion of the
generator). Mounted to the inside of
this band is a solid state voltage regulator.
This system is made by Nu-Rex. You must still use a cutout, to prevent a
connection to the generator while the Model A is not running and can be of the
stock relay or diode type. This Voltage
Regulator is limited to use with 6 Volt Positive grounded systems. This type of
voltage regulator cannot be used with the 1928 “power house generator”. If you want to install a voltage regulator
for use with a “power house” generator you will need to use the cutout mounted
regulator discussed below.
When
used with a stock generator, this regulator will “electronically” move the
third brush as the voltage demand changes.
At night when the lights are on, this will automatically increase the
charging rate. The ammeter should read
Zero after the battery is fully charged.
This device senses the battery voltage and automatically changes the
charging rate so that the battery is not overcharged. The manufacturer claims that you will have
stronger lights, and horn performance. [39] According to the manufacturer, you will have
higher charging rates at slower speeds. [40]
This
type keeps the Model A generator looking “completely stock” and you do not have
to replace the generator brush cover band.
It will work with the 1928 “Power House” generator. What you do is purchase a replacement cutout
voltage regulator. The new cutout
voltage regulator, while looking completely like a stock Model A Ford cutout,
has a modern voltage regulator built into it.
This device is also manufactured by Nu-Rex. The Model A electrical system MUST BE
Positive ground. To use the voltage
regulator you set the generator charging rate high then the voltage regulator
will automatically adjust the actual rate to what is needed. This type comes in three versions:
·
#1
for use with stock Model A generators
·
#2
for use with a generator has wires coming out of it instead of a post
·
#3
for use with a 12 Volt Battery if you have a 6
Volt generator
This
type is includes a diode as a cutout, and therefore eliminates the old Ford
mechanical relay system with its tendency to have “sticking generator
contacts”.
Almost
all of the mail order Model A parts suppliers can supply these voltage
regulators. The following chart shows as
of December 2007 the various suppliers.
A visit to the website of Nu-Rex, the
manufacturer of these voltage regulators does not show these devices in their
on-line catalog or provide any technical specifications.
|
Supplier
|
Type
|
Price
|
|
Bert’s
|
Cutout
VR
|
$75
|
|
Mike’s
A Fordable Parts
|
Cover
Band VR
|
$50
|
|
Mac’s
|
Cover
Band VR
|
$67
|
|
Cutout
VR
|
$69
|
|
Snyder’s
|
Cover
Band VR
|
$50
|
|
Cutout
VR
|
$63 -
$69
|
|
Bratton’s
|
No
longer carries VRs
|
|
For more
performance the “ultimate” generator replacement is to use a modern alternator,
which replaces the entire generator, voltage regulator and cutout system in the
Model A. There are advantages and
disadvantages to making this replacement.
The most obvious downside is that the “look” of the alternator is
completely different than the generator/cutout of the original Model A Ford. The second downside, is that if you have a working
generator, the change to an alternator is costly, and your “good old” generator
will be sitting useless on the shelf in your garage. On the other hand, an alternator can
eliminate the problems associated with the original Model A charging system, and
prevent overcharging.
There
are two ways to go when considering an alternator solution. You can keep the positive ground 6 Volt
system, all of the lighting, and accessories of the original Model A, by
installing a new specially built or modified older alternator that can operate
with the 6 volt positive ground system and battery. Alternatively, you can modify the Model A’s
electrical system to 12 Volt negative ground and use a modern alternator to
power it.
This
appendix is provided to give some background to the discussion of the Model A
generator system, and why, and how it was developed.
Early
manufacturers of automobiles, wanting to provide electric lighting for their
cars experimented with various means of generating and storing electric
power. Batteries were well known by 1903
and were available in low enough voltage that could provide lighting. Generating an electric current from a
magneto, driven by the engine (called a dynamo in those days) was well
known. Electric power generators with
series, compound, and shunt wound configurations were also known. These generators, operating at constant speed
could easily generate the power.
However, the automobile did not operate at a constant speed, and the
problem of regulating the power to provide a constant voltage or current eluded
the manufacturers for many years. Early
generators, which provided current at ever increasing values as the engine
increased its revolutions per minute, caused the lights to either burn dimly or
so bright that eventually they would burn out.
The earliest versions, 1903 to 1905, of a generator current regulator were
mechanical centrifugal governors using slipping clutches. These were largely unsuccessful until 1908
when a few regulators of this type were added to expensive automobiles.
The
advent of the electric starter, and its need for stored battery power, caused a
flurry of activity in the automotive industry to develop an electro magnetic
regulator system. The first practical design to reduce the charging current as
the battery became fully recharged was the Bijur
Voltage regulator [41].
The Bijur regulator used an electro-magnet winding
and a pivoted armature which used a spring and a set of contacts which vibrates
as long as the Voltage is high enough to energize the magnet. The decrease in the amount of current was in
proportion to the number of pulsations per minute of the regulator. By 1912 the industry had developed a means to
weaken the excitation of the generator fields to cut down the current as the
engine increased RPM. Eventually, two
types of regulation developed, they were called external and inherent. The first type to develop was an external
regulation method based on the Bijur which used
electro-magnetic relays to cause a vibration which rapidly closed and opened
the current flowing through the fields as the generator built up speed which
caused the current to remain constant while the voltage varied according to a
set point. The second type caused the
current to vary while the voltage remained constant.
The
early vibrator regulator types, which worked, had a flaw. If the points stuck open the generator could
burn up, if they stuck closed, the generator (attempting to be a motor) could
run the battery down. At that time, the
notion of a cutout in addition to the regulator had not developed. A few of these “vibrator” types were found on
the more expensive cars. In turn, the industry
sought a better means of regulation that did not require a separate vibration
unit, which in those early days proved to be somewhat unreliable and tricky to
set and maintain. Experiments and inventions yielded two methods inherent to
the generator. One inherent means of
regulation of the current was the so called bucking coil windings and the
other, more common, was called 3rd brush regulation. All generators of these early days relied
upon an electro-magnetic relay to “cut out” the generator from the battery when
the car was either parked or traveling at a slow speed.
During
the period from 1912 into the early twenties manufacturers continued to
experiment with various electrical power starter and generator
configurations. Common versions were either
combination generator/starter units and those with separate starters and
generators (called two unit systems).
Many of the component manufacturers such as Delco, and Northeast offered
both. During this period, General Motors
offered cars with both kinds of systems, while the Dodge Brothers offered only
the single unit design. Ford, however,
shunning the self starter, offered neither until 1919. The 1914 Cadillac, Hudson, Olds, Packard and Oakland offered a Delco Self Starter combined
with a generator, and used a mercury rectifier composed of a plunger which
dropped into and was pulled out of a mercury reservoir and was operated by an
electro magnet. In 1915 – 1916 the Delco starter/generator used a mechanical
regulator as the mercury type proved to be prone to failure. Beginning is 1917 Delco changed once again to
add a 3rd brush to the generator section of the starter/generator,
by 1921 a thermostatically controlled bi-metallic regulator was used
briefly. Finally, by 1923, the industry
separated the starter and the generator into two separate units and the 3rd
brush generator became the pseudo standard.
Ever the innovators, the Dodge Brothers in 1914 offered a low cost car
with a self starter, a 12 Volt battery system [42],
and a 3rd brush generator which was to be set to charge at 7 Amperes
on the average.
The
problem of current regulation in automotive generators persisted for the next
50 years. Various early external means
divided into voltage and current regulators all based on the vibrating relay
concept, while inherent to the generator means of regulation settled in on
bucking coil windings for 4 pole (4 brush) generators and a variation on the
two pole (2 brush generator) called 3rd brush regulation. While none of these methods were really
satisfactory as a permanent solution, the industry by the late teens and early
1920’s settled in on the 3rd brush generator regulation as a
pseudo-standard. Early versions of the
external constant current and constant voltage regulators were unreliable and
failures caused the generators that were attached to them to burn up. Many of the more expensive makes, that had
higher current and reliability requirements continued to use external current
or voltage regulators in combination with the 3rd brush two pole
generator. The 4 pole generator with
external regulation also continued to be used, especially with the single unit
starter – generator.
The
problem of overcharging the battery in early automobiles was well known to
automotive electrical engineers prior to 1920 and well into the 1930s. While early versions of various generator
regulation means were unreliable, they persisted throughout the teens and into
the twenties. Expensive automobiles used
them as part of the starter/generator system (Delco) or as stand alone
regulators, used in combination with current regulators, prior to 1926 by both
Westinghouse and Delco. [43] Ford did not utilize an external means of
regulating the generator output until 1935 when it introduced a two stage
current regulator, and finally in the late 1930s introduced a voltage regulator
to prevent overcharging. The reason that
an unregulated voltage could be used on low performance cars was that the roads
of the day prevented high speeds, therefore limiting the speed of the
generator. In addition, long distance
driving had not yet become fashionable.
Combining these factors meant that overcharging could be managed by
seasonally adjusting the charge rate, and owners could manually adjust their
generator charge rate to suit their driving habits. By the mid 1930s this method had proved
impossible to maintain, and the industry returned to the vibrator voltage and
current regulation first invented in 1908 to 1912.
By the
1950s Ford was using a three component regulator, which combined a cutout, a
current regulator and a voltage regulator in one box, usually mounted on the
firewall.
Eventually
the automotive industry settled on the most reliable means of starting and
power generation methods. The industry selected the two unit starter –
generator combination that we have today.
Except for the more expensive cars, the 3rd brush regulation
became the most commonly used means of regulating the current in the generator
in the 1920s. The Model T and the Model
A were users of the 3rd brush generator without an external vibrator
regulator. While some manufacturers
continued to apply external vibrating current or voltage regulators to their
systems the most common designs did not, thus requiring the owner to make
seasonal and driving habit 3rd brush setting changes
periodically. Literature of the time,
shows that one of the most prominent discussions was “where and how to set the
3rd brush”. There were many
theories and old wives tales on how set the 3rd brush.
The
problem with regulation of the generator output versus automobile speed is
shown in Figure
17 Generator Output vs
MPH with various regulation. Most cars of
the early twenties used 3rd brush generators with regulators that
developed their maximum current output at about 25 MPH and as shown were
capable of about 15 to 18 Amps at that speed.
By the 1930s the need for more amperage increased the maximum current to
about 25 Amperes. The Ford Model A
generator was capable of 22 Amperes, the green line on the chart, but Ford Engineers recommended settings of
half or less of that amount.
Figure 17 Generator Output vs MPH
with various regulation
As shown
in the blue dotted line, the engine
speed builds up the current produced by the generator after the cutout connects
the generator to the battery. Without
regulation of some form the current produced will increase, being forced
through the battery and the electrical circuits, burning out components and
overcharging the battery. The chart,
concentrating on the 3rd brush design eventually used on the Model
A, shows the operation of a 3rd brush generator with and without
external regulation. Automobile speeds
in those days were typically below 40 MPH,
the 3rd brush generator in low cost cars could be used
without any further voltage regulation.
The solid black line shows the relationship of automobile speed to
generator output. Typically, the designs
were made to peak at about 15 Amperes at 25 MPH and then fall off as shown as
the engine speeded up. For expensive
cars, such as the Packard, with more accessories and power demands, the
manufacturer would add a vibrator current regulator and a voltage regulator to
cause the generator to have a constant current, as shown with the red line
after speeds of 25 MPH or so and reduce the charging when the battery became
fully charged. Eventually, the systems
prevalent on the more expensive cars was adopted by all manufacturers,
including Ford. By 1950 most
manufacturers provided adequate automatic battery charge protection for
overcharging.
The
Model A 3rd brush generator was basically the same as the Model T
generator used in the later part of the 1920s.
As shown in Figure
17 Generator Output vs
MPH with various regulation , the Model A generator was capable of about 22
Amperes of current output, however typical settings were much less than that as
shown by the dotted black line. The
Model T and the Model A battery charging system used a “pure” 3rd
brush system without any external regulation.
While this was adequate for most driving habits of the day, the high
constant current output overcharged the batteries. This problem continued to plague the owners
of Model A cars then and still today [44]. As will be discussed below, the Ford Motor
company eventually responded to customer concerns about battery overcharging,
the difficulty in manual adjustment, peer pressure, and the continuing
requirement for more power to be developed, by introducing external regulation.
Charging
current from most generators of the 1920s and early 1930s were of the constant
current type. Overcharging of the
battery and electrical system problems and concerns prompted the automotive
industry to return to some form of generator voltage regulation. By the mid 1930s most of the manufacturers
had added some form of regulating the charging current that would taper off the
charge current to the battery as the battery became fully charged. There were several types of voltage
regulation developed during this period.
The interest in the earlier 1912 to early twenties vibrator types
revived, as well as types that used new techniques. Figure
18 Early Voltage Regulation Operation shows the basic method of voltage regulation
applied in automobiles developed soon after the Model A.
Figure 18 Early Voltage Regulation Operation
The
regulation of the charging current is shown in the lower part of the diagram.
Without voltage regulation of the charging current the generator charging
current is applied to the battery constantly as long as the vehicle is
operating above 10 MPH. Two of the many
kinds of voltage regulation are shown.
All types of charging regulation are caused by reducing the field
voltage developed by the windings of the generator. The black line shows a 3rd brush
generator with a vibrator type of voltage regulation. The red line shows no regulation, and the
blue line shows a two step relay type regulator used in early Fords after
1935.
The
upper part of the diagram shows the battery charge condition as time increases
from the starting of the car. Initially,
the battery charge decreases to some value below 6 Volts depending upon how
much charge is taken from the battery and the initial state of charge of the
battery. Once the car has been started
and the cutout has closed, the generator charging current is applied to the
battery and the voltage of the battery begins to rise. Eventually the battery regains its charge and
its voltage approaches the open circuit voltage of 6.3 Volts [45]. Eventually, the battery becomes fully
recharged. It is this point that the
regulation of the charging current becomes important to prevent
overcharging. Notice that if the field
voltage in the generator is not reduced the charging current (the red line)
continues to attempt to charge the battery at the Ampere setting of the 3rd
brush causing the overcharging. If a
vibrator type of regulator is employed, as the battery voltage approaches 6.3
Volts an electro-magnetic relay is energized pulsating according to engine
speed, and causes the field voltage to collapse reducing the charging current
to zero. If a two step regulator is
used, when the battery voltage reaches a certain set point, usually slightly
above the open circuit value of the battery, a resistance is applied to the
field winding, reducing the current and causing the generator current to be
reduced to a much smaller value. Either
of these approaches, and there are more, will reduce or eliminate battery
overcharging.
The
early Fords had no electrical system except for that required to provide the
ignition. This system was a magneto
system, which was kept from the earliest Ford cars until the end of the Model T
production in 1927. Early designs used
12 to 16 Volt magnetos, which were eventually revised to the 18 Volt
design. The unregulated magneto could
provide electric power to run lights with “good” illumination at 8 MPH and full
candle power at 12 MPH. As the speed
went up it was possible to burn out the lights.
Many owners added a battery to run the lights and recharged it manually,
since the car had no generator. For $85 [46]
you could add a Westinghouse 12 Volt starter [47],
battery and lighting power system. For
$5 you could add a Double EE charger to charge a 6 volt battery from the
magneto.
The Ford
Model T after 1919 was the first Ford Model to have a self starter. Driven by the wide spread use of the Model T
in the 1st World War, Ford moved to add a self starter to the
original design of the “T” and to improve the overall design. The Ford Model T, manufactured after 1919,
had a self starter and had an electrical design [48]
with a 6 Volt negative grounded battery, which supplied a 98 Amp hour cranking
capability for 20 minutes. The starter
had a cranking capability requirement of 120 Amps at 5.2 Volts, which yielded
an engine speed of about 150 RPM (2.5 RPS). The lighting capacity was 5 Amps
for 17 hours. Ford manufactured its own
generator, applying it to the Model T manufactured after 1919. This generator was not the same as the one
used in the Model A. The Model T
generator was a 4 pole design with a 3rd brush.
The
Model A electrical design followed closely the Model T design, except for a few
requirements. The Model A changed the
polarity of grounding the battery from negative to positive, following the
practice of the times and changed the design of the generator. The Model A
version is a 2 pole design with the 3rd brush. It typically had a maximum current of 22 Amps
and is shown with the green line. Model
T and Model A owners were admonished to set the 3rd brush well below
this current level.
Today we
do not think much of the battery and charging system, since batteries today are
inexpensive, and last 5 years or more.
Likewise, the modern alternators found in almost all modern cars are
reliable and easy to service and replace.
The operation of these electrical devices in our highly sophisticated
cars with computers and advanced electronic devices is automated, and we rarely
consider their use or how they were developed.
To put the Model A electrical power generation operation in perspective
we will provide the reader with a short history of the development of the
modern battery charging system.
Figure
19
History of Modern Charging Systems
The
modern charging system has had only three major evolutions. Two of these evolutions came after 60 years
of the use of the first. The evolution
of the need for “on board electric power” caused by the needs of the motoring
public, the automotive industry evolved the current battery plus generator (or
alternator) system. With the future
advent of the fuel cell for motive power, this may soon change.
Soon
after the development of the motor car in the 1880s, the motoring public began
asking for electric lights for night driving, and a self starter. [49]
The earliest solution to these needs utilized acetylene lamps and mechanical
starters of various types. The first
lighting system was acetylene lamps, but these were soon destined for the scrap
pile due to the time consuming task of purging the gas lines and lighting. Soon dry cell storage batteries and wet cell
rechargeable batteries appeared. These
rechargeable batteries were a pain, since they would require removal from the
car and recharging by an external battery charger.
Self Starters
The
earliest self starters were mechanical devices.
Electric motors, lead cell electrolyte batteries, and electric
generators were known to the early automotive engineers prior to 1900 and early
attempts to work out how to combine these into a practical system needed a new
invention. When a motor was run to start
the car, it would consume most of the power of the battery. The basic problem was how to recharge the
battery onboard the car. Generators
worked fine at a constant speed, but when the speed was increased, while
driving, the generator field voltage rose so high that the generator would burn
out. A form of regulation was required
to make the electric system on a car be practical.
Various
mechanical means of generator regulation, using centrifugal devices, and
slipping clutches were tried as early as 1903.
[50]
No practical version emerged until 1908.
The mechanical regulator had a brief usage time, but by 1907 to 1910 the
engineers had worked out an electro-magnetic means. The concept of a vibrating set of points
which interrupted the flow of current through the field windings and caused the
collapse of the generator current was invented.
This invention caused the self starter, generator, and battery
combination to become standard, which essentially continues today.
Beginning
in 1912 to 1914, the automotive industry abandoned the early mechanical means
of self starting the car and soon adopted the electric self starter. These new self starters began to appear on
expensive and low cost cars. Henry Ford,
however, shunned these improvements for nearly 7 years, claiming that there was
no real need for a self starter.
Finally, in 1919 the “ Improved Model T ” was introduced with a self
starter and electric lighting. Prior to
that owners had to modify their cars themselves to include these features. This was not cheap, Westinghouse offered a
self starter/electric light system with a generator and battery for $85 in
those days dollars, a whopping 25% of the cost of the automobile originally.
Batteries
Batteries
found their way onto automobiles before 1900.
Electric Cars and electric lighting was common from 1900 on. Early batteries had to be charged by an
external battery charger until the advent of the automobile generator after
1903. Batteries were to be found in 6,
12, and 18 volt versions, with varying capacities. Two standards emerged by the late teens, 6 volt and 12 volt versions. The 12 volt battery lasted until late 1925
when Chrysler changed the venerable Dodge 12 volt design back to 6 volts. The 6 volt battery standard continued for 28
years until the early 1950s.
Ford
finally put a battery on the Model T, after much customer pressure, in
1919. This battery was a 6 volt design
with 80 Amp Hours of capacity. The Ford
Motor Company, in keeping with Henry Ford’s policy, made its own battery
becoming the only automobile manufacturer to do so. The Ford Model T battery is the same battery
that is found on the Model A. The
battery in the Model T was negative grounded.
For some unknown reason, Ford engineers changed to positive grounding
with the Model A. The 6 volt battery
design, with positive grounding persisted until the positive ground was
changed to negative in 1949.
The most
common battery design after 1925 was 6 volts with either positive or negative
grounding. General Motors started the
modern configuration [51]
in 1953 when it introduced the 12 volt negative grounded battery on Buick,
Cadillac, and Oldsmobile. Quickly, the
other manufacturers completed the change over to the new 12 volt negative
grounded standard by 1956. Ford made
its change over in 1956.
Generators
Many
different types of generators were developed and tried. After about 10 years of development, the 3rd
brush generator emerged as the design of choice for a large part of the
automotive industry. This was driven by
the development of the regulator. A wide
variety of regulation means were developed by the automotive industry over the
period 1912 to 1920. Most of these
utilized some form of vibrating relay.
These devices both constant current and constant voltage types, had a common
problem. They would either fail closed,
causing the generator to drain the battery when the car was stopped, or fail
open causing the generator to burn up.
The industry quickly sought a new design, inherent in how the generator
system worked. The most used solution
was the 3rd brush generator, which had brushes to control the
charging current not relays which could stick or fail. The manufacturers of generators, Northeast, Leese-Nevelle, Delco, Dyneto,
Westinghouse, Atwater-Kent quickly went to work perfecting the 3rd
brush design. Some, such as Delco and Bijur offered various improved constant voltage regulators
to prevent overcharging, but a wary public complained about reliability and a
large percentage of the automobile manufacturers offered a straight 3rd
brush design.
Regulators
The
Model T Ford used an 18 Volt magneto for powering the engine. Henry Ford used this magneto to power the
Model T lights. With no battery, the
lights provided “good” light at 8 MPH and “Full Candle Power” at 12 MPH. [52] Many owners added a 6 volt battery with a
switch to cut the lights in, but with no generator, it required an external
battery charger. After the 12,225,528th
Model T , Ford finally added a generator.
The generator introduced to the Model T was the 3rd brush
type, and it was manufactured by Ford until 1927. It is the same as the “Power House” generator
on the earliest Model A. There was no external regulation using this generator,
but a electro-magnetic cutout was used to connect the battery to the generator
above speeds of 10 MPH. The Model T
continued to use the magneto spark until its demise in 1927.
The Model T and Model A 3rd
brush generator design was used at Ford until after 1935. In 1935 Ford added a two step regulator to
the 3rd brush generator to eliminate the battery overcharging
problem. The two step voltage regulator
was followed by a two pole generator, with a combined cutout and voltage
regulator, and finally a three coil unit combining the cutout, a voltage
regulator, and a current regulator. This
combination continued until Ford finally abandoned the old fashioned
electro-magnet relay regulators in favor of the solid state regulator in 1969.
Alternators
Generators
with electro-magnetic relay regulators continued to be used by all
manufacturers until the advent of the alternator. The first practical alternator was developed
by the Leese-Nevill company in 1952 and called the
“Rectified Alternating Current Generating System”. [53] Eventually this name was shortened to “
alternator“. Leese-Nevill
developed both 6 volt and 12 volt designs.
The “big three” were not impressed at first and it was 8 years before
Chrysler introduced an alternator on the Dodge Valiant in 1960, then on the
Chrysler Imperial and Plymouth
in 1961. By 1964 the alternator’s
benefits of operating at stop and go driving was recognized, and by 1969 they
were in wide spread usage. Ford began
using the Leese-Nevell alternator in 1965 in
combination with the older electro-magnetic regulators, finally changing over
to solid state regulation in 1968. [54] . Eventually, Ford settled on the Auto Lite alternator. Alternators
finally transitioned to their current form in 1969 with the addition of the Zener Diode and the integral regulator.
Foot Notes:
direct-current electricity from
an outside source back into chemical energy.
The external direct-current power is typically provided by a generator
while the car is being driven, but can also be provided by an external battery
charger. The discharge cycle is shown
here. The electrical flow is from the
stored energy in the battery to the various loads such as the lights and the starter. The energy is used to power the components. Connection from the components to ground
through the Model A Frame completes the circuit.