3, The ORIGINAL CHEVY MAIN POWER SYSTEM
the “NEW System” by M.A.D.)
For all systems…
a good job of distributing power from the alternator to
various parts of the electrical system is a requirement
for good electrical system performance.
small voltage drop in wiring will cause a major loss of
The original factory system had enough voltage drop
problems in wiring to the dash area; there is no need to
make matters worse by installing a new alternator and
wiring it directly to the battery.
Installation of a “high-powered”
“ONE-WIRE” alternator, wired directly to the battery,
would cause deficiency with the original CHEVY system.
refer to the diagram of “THE ORIGINAL CHEVY SYSTEM,”
as the diagram will support the following text.)
true that the “ONE-WIRE” alternator wired directly to
the battery would be a consistent battery charger, as the
battery would be maintained at about 14.2 volts.
But the battery is at the opposite side of the car
from the “main power distribution hub.” An alternator output wire connected to the battery will not
provide consistent voltage at the “main power
Power for the electrical system would have to flow
from the battery area at the right, to the Horn Relay at
the left, through the old “battery charging wire.”
With lighting and accessories switched ON, a large
amount of current will flow to the dash area, and a
voltage drop will occur.
With the “typical” ONE-WIRE installation,
the voltage regulator would no longer maintain the Horn
Relay at 14volts.
We can use the ONE-WIRE model of
alternators, but we have to wire it properly to get good
explained in our Tech Section feature on “REMOTE
VOLTAGE-SENSING,” the “ONE-WIRE” alternator was
created with simplification of alternator wiring the
primary intent. The
“ONE-WIRE” is okay with simple machinery, and with no
lights or involved wiring to support the many accessories
we have on cars. (This
is why GM did not install “ONE-WIRE” alternators on
cars and trucks. Although
the “ONE-WIRE” would have saved GM a fortune in
wiring, it also would have compromised performance.)
spread promotion and sales of the “ONE-WIRE alternator
for use on custom cars was intended as a “no-brainer”
in truth it has created an ironic situation.
Creating an effective wiring method for the
“ONE-WIRE” alternator will cause the brain to work
best use of “ONE-WIRE” alternators is with the “NEW
SYSTEM,” which was previously diagramed.
Remote voltage sensing is not available with the
ONE-WIRE alternator, therefore the wire from the
alternator to the terminal block must be sufficient in
gauge size to handle all electrical system load without
significant voltage drop.
Good performance with the “NEW SYSTEM” will
require that the terminal block run at about 14volts.
(Also see our Tech Section feature on “ONE WIRE
compared to THREE-WIRE” alternators.)
CHARGING WIRE” (in
the original CHEVY system)
This is a simple but very important part of the
involves only a single wire, which will deliver charging
current to the battery.
Alternator power is first routed to the power
distribution “hub” (a splice in the original system,
or the terminal block on the firewall in the “NEW
SYSTEM” by M.A.D.).
The “battery charging wire” connects the main
hub to the battery. In
these systems, the battery charging wire only charges the
battery; it does not operate the electrical system.
many other cars, the alternator output wire routes
directly to the battery (or to the battery POSITIVE cable
at the starter solenoid).
And power-up wires to operate the dash area and
electrical system will also connect at the battery.
In these systems the battery charging wire charges
the battery plus operates the entire electrical
system–and a heavy gauge wire will be needed to handle
there was yet another variation of wiring for the
alternator output current; send multiple wires from the
alternator in different directions.
Pontiac made most of their cars during this period
using the alternator output stud for the main power
Fusible Link wires for the dash area and accessory
power-up connected directly to the alternator output stud
separate battery charging wire was routed directly from
the alternator to the battery POSITIVE cable.
(In some Pontiac models from this period, the
charging wire connected at the battery, and others
connected at the starter).
the Chevy system
(and in the “NEW SYSTEM” by M.A.D.)…
maximum battery-charging rate can be slowed down with
proper selection of wire gauge size and length.
Battery voltage needs to rise to about 14.2volts to
keep a battery topped off with charge.
(14.2volts is the popular textbook standard.)
But when recharging a battery it’s less abusive
to slow the charge rate a little.
A perfect system might also reduce voltage to about
13.8 or 13.9 with severe summer
heat, or for extended periods of charging, as with
cross-country or all day travel. Battery life would be extended, and we would see much less
corrosion at batteries with voltage reduced in hot or
extended use situations.
In opposite of the hot summer weather, where cold
winter climate and with short drives is the primary use,
the ideal voltage regulator setting might be ideal at 14.3
to 14.6volts. The
battery likes a slightly higher charge rate in cold
the slightly increased voltage would help keep the battery
charged for starts on those extreme cold winter mornings.
slowing the battery recharge rate can be desirable for
many of us with cars, provided electrical system
performance is not affected.
The slow rate battery recharging is less abusive to
batteries than fast rate charging.
Less gassing and therefore less corrosion will
occur with slow rate charging.
And slow rate charging can reduce alternator
overheating. (Also see our feature on “VOLTAGE REGULATOR,
ALTERNATOR and BATTERY CHARGING, HOW IT WORKS.)
alternator system is intended to maintain the battery, but
not to recharge “dead” batteries.
Yet, the occasion can arise when we have the need
to completely recharge a battery while driving. Accidentally leaving the lights ON can thoroughly discharge
the battery. And
often the most convenient solution is to get a
“jump-start” with booster cables from another car.
After getting the jump-start, the alternator will
recharge the battery while driving.
special interest cars are not often used as a “daily
when parked for extended periods, small “drains” can
partially discharge the battery.
In this example the alternator will often be
recharging the battery, when the car is driven.
(Also see our Tech Section page on “CHARGING
BATTERIES for MAINTENANCE and STORAGE.”)
of the heavy gauge cable for fast battery charging is most
appreciated in applications that need fast battery
recovery, as with electric winch operations in 4x4 trucks.
But it can give us car people headaches.
FOR THE BATTERY CHARGING WIRE IN
THE “NEW SYSTEM”
Based upon many years of measuring charge rates and
battery voltages when checking charging systems, here are
recommendations for the minimum wire gauge size, and also
wire lengths, for the “battery charging wire” in the
one battery (not dual battery systems) mounted
at it’s original location up front; use
a seven feet to ten feet length of 10gauge wire with a
14gauge fusible link.
(With the preference at close to ten feet.
The ten feet preference is about the right length
to slightly slow the battery charge rate.
Also, by reducing current flow the long 10 gauge
wire will reduce the possibility of warming the Fusible
the battery is relocated to the rear using
M.A.D.’s rear mounted starter solenoid system, then the
battery charging wire will be much longer.
In that case we recommend twelve to twenty feet
of 8gauge battery charging wire with a 12gauge fusible
link at the rear.
(Preference for length is with about eighteen feet
of the 8gauge charging wire. And this recommendation is also for one battery, not dual
please note that M.A.D.’s Tuff-Wire is recommended for
the new battery charging wire.
The Tuff-Wire insulation is double thick and has a
much higher temperature rating than ordinary wire.
made the recommendations for the “battery charging
wire,” we will offer explanation.
determining the minimum gauge size of battery charging
wire, we have two considerations.
amount of heat generated in the wire at maximum current
will be affected with voltage drop in the wire, also at
maximum current flow.
THE “BATTERY CHARGING WIRE”
There is sensible explanation as to why it
doesn’t happen when charging only one battery with the
“original CHEVY system” and in the “NEW SYSTEM” by
wire is only used to charge the battery (not operate the
electrical system), and a car battery will not
absorb enough current to overheat the wire we have
recommended for these systems.
small amount of resistance from a long length of
reasonably heavy gauge wire does not generate much heat
per foot of wire, with the maximum amount of current flow
during peak battery charging.
But a not so good situation would be the same
amount of resistance in a short length of small gauge
wire, which will generate more heat per foot of wire.
maximum amount of current flow through the battery
charging wire will depend upon how much current the
battery can absorb, with voltage limited to about
really large battery intended to crank up the diesel
engine in an eighteen-wheeler, during sub-zero weather,
can absorb a lot of current when charged at 14volts.
(When the big battery has been discharged.)
discharged battery in an ordinary car will absorb much
less current than the big truck battery.
Ultimately the “perfect” length and gauge size
for the battery charging wire in this system will depend
upon battery capacity, temperature of the battery and
wiring, and characteristics of the particular battery.
for a wide range of car batteries, our recommendations for
the “battery charging wire” have proven to work well.
(The recommendations were:
With battery up front use a seven feet to
ten feet length of 10gauge wire with a 14gauge fusible
the preference at close to ten feet.)
And with our battery at the rear system, twelve
to twenty feet of 8gauge charging wire with a 12gauge
fusible link. (With
the preference at about eighteen feet.)
Our page on “RECHARGING A DISCHARGED BATTERY”
shows approximate amounts of current flow that a car
battery will accept when being recharged. And, our page on “REMOTE VOLTAGE SENSING” consistently
shows a ONE VOLT DROP with 60amps to 65amps of current
flow through twelve feet of 10gauge wire.
This amount of current flow is considered an
overload, as voltage drop is excessive.
However with extensive use, the wire never became
warm–it remained cool as if there was no current flow
through the wire.
60 to 65amp test serves as a good stress test of our
minimum recommendations for the battery charging wire.
A 60 to 65amp current load is about twice the
amount of current that a car battery will absorb, when
being recharged by the alternator and with our wiring
system in place. (See
voltage drop with current flowing through this wire, in
the photo below.)
In the above photo, the VOLT SELECTOR switch is set
to the 3volt scale. The
“external voltmeter” wires of the SUN model VAT-40 are
connected at each and of a twelve feet long 10gauge wire,
and the black scale at the volt meter displays a ONE VOLT
drop in the wire. Also
in this photo the blue scale at the AMP meter is
displaying between 65amps and 70amps through the twelve
feet of 10gauge wire.
The photo above is one of many from our page on
“REMOTE VOLTAGE SENSING.” In this photo, the current flow is greater than with other
VAT-40 used is over-due for calibration tune-up and
general service. Also,
the amp gauge on the model VAT-40 machines was never
THE AMOUNT OF HEAT GENERATED IN THE WIRE
First we must calculate the amount of resistance at
the wire used for the test (The amount of resistance is
much too small to be measured with an ordinary ohmmeter).
÷ 60amps = 0.0167ohm resistance in the twelve feet of 10
0.0167ohms ÷ 12feet of wire = 0.0014ohms per foot of 10
know that the AMP meter of the SUN model VAT 40 is not
precise, and that could cause small error with our above
calculation of resistance per foot of wire. We reached for a book that would list resistance of wire per
foot, in various gauge sizes.
The book listed AWG 10gauge at 0.0011ohm per foot,
but did not include temperature of the wire.
In our library, we also found a GM engineering
manual from the Muscle Car period, which warned that we
should expect a 25% increase of resistance when wire
temperature is increased from 700F to 1700F.
Routing of the alternator output wire and the
battery charging wire placed parts of those long wires
where they will be subjected to radiator heat, especially
when driving in city traffic.
happens that our calculation of 0.0014ohms per foot of
10gauge wire is almost exactly 25% more than the listing
of 0.0011ohms per foot.
Knowing that aging connections and temperature of
the wire will contribute resistance to the battery
charging wire circuit, we will use our calculated 0.0014
ohms per foot of 10gauge for this discussion.
(It’s a number that will be most representative
for wire in this circuit, with a typical car.)
Since our resistance value is slightly on the
high side, our calculations for heat and performance will
show the worst to expect with a 10gauge battery charging
Now that we have the resistance value, watts of
heat generated with various amounts of current flow will
be calculated using the math formula from Joule’s Law.
The math formula is AMPS2 X OHMS = WATTS
(of heat). And
please notice that the AMPS factor in the formula is
squared. In the finished calculations, we will see that reducing the
amp value by only a few percent will reduce the watts of
heat to nearly one half.
(And in opposite direction, increasing the AMP
value by a few percent would double the amount of heat
large capacity, discharged battery
capacity, discharged battery
capacity, discharged battery
1/2, charged battery
full charged battery
fully charged battery
of resistance value, and also the resulting watt of heat
calculation, are both per one foot of 10gauge wire.
no wonder that we could not detect any heat being
generated in the 10gauge wire used for the “REMOTE
VOLTAGE SENSING” feature!
The amount of heat generated at that amount of
current flow overload was too small to notice.
In the “original CHEVY system,” and in the
“NEW SYSTEM” by M.A.D., we will have considerably less
than 60 amps of current flow through the “battery
charging wire.” And
with less current flow, the amount of heat generated in a
10gauge charging wire will be much less than in the
example used for the calculations above.
a 40amp current flow through the battery charging wire...
x 0.0014ohms = 2.224watts of heat per foot of wire
with only a 20amp current flow through the battery
x 0.0014ohms = 0.56watts of heat per foot of wire
the 8gauge wire serving as the “battery charging wire”
in our trunk mounted battery system, the amount of heat
per foot of 8gauge wire will be a fraction of the amount
with the 10gauge wire in the battery up front system.
how much heat is 2 or 3watts spread out over twelve inches
of 10gauge wire? Please
see the photo below.
In comparison, a #194 miniature light bulb operating at
14volts, which is common for instrument lighting at dash
panels, will produce about 3.75watts of heat. But the light bulb is very small, and heat will be radiated
from a much smaller area than in twelve inches of 10gauge
small dimension light bulb with this much wattage will
feel much hotter than 2 or 3watts of heat spread out over
12inches of 10gauge wire.
Yet even installed at small closures in instrument
panels and clearance lights, the heat does not melt the
ordinary plastic at the dash.
And although it is warm, it also doesn’t burn
Also, regarding overheating the charging wire in the
systems we are discussing, there is another consideration.
The photo above shows a stator winding assembly
removed from a 94amp model 12SI DELCO alternator.
Notice that the diameter of the single strand wire
used with each of the three windings from the stator is
output is actually produced in these three stator
windings, and there is a limit with the amount of current
that these stator windings can stand before the insulating
varnish of the wire burns and the windings become shorted.
With many models of alternators, the stator winding
would burn before our recommendations for the “battery
charging wire” would be heat damaged.
So now we know that
heat is not a problem with our recommendations for the
battery charging wire.
Let’s check on the performance issue (voltage
CALCULATING VOLTAGE DROP AT THE
amount of voltage drop will change with the amount of
current flow, but unlike the watts of heat generated,
voltage drop is a “direct proportion.)
we calculated the amount of heat per foot of the 10gauge
charging wire, we used the resistance value of 0.0014ohm.
We will use the same resistance per foot value here
for calculating voltage drop, but now we are concerned
with voltage drop in the entire length of wire.
The resistance value for the 10 feet length is
we will use the formula AMPS X OHMS = VOLTS (drop) to
perform the calculations at the same battery charge rates
as when we checked for heat. And then we will subtract the “VOLTS (drop)” from a
14.3volt regulator setting to calculate “VOLTS at
BATTERY” as the alternator is recharging the battery.
large capacity, discharged battery
capacity, discharged battery
“plus” capacity, discharged battery
½ to ¾ charged
full charged battery
fully charged battery
of resistance value, and also the resulting voltage drop
calculation, are both at the 10feet length of 10gauge
“VOLTS at BATTERY” was calculated by subtracting the
amount of “VOLTS(drop)” in the table above from
textbook level for voltage regulator setting is 14.2volts,
with a range between 14.1 and 14.5 generally acceptable.
We have chosen to use 14.3volts as voltage
regulator setting for these calculations, as 14.3volts is
the “NEW SYSTEM” diagram, the voltage regulator would
maintain voltage at the terminal block on the firewall at
14.3volts, which is the regulator setting we have chosen
for this example calculation. And voltage drop would occur
with current flow through the “battery charging wire,”
which is routed to battery POSITIVE.
“VOLTS at BATTERY” in the table above is the
voltage that would be measured at the battery as it was
being charged by the alternator with this wiring system.
60AMP and 50AMP CHARGE RATE
CALCULATIONS (posted in the table
The first two example calculations in the table
above are with more current flow through the battery
charging wire than we will see when charging one, car
standard dimension car battery that would accept 50 or
60amps current flow at about 13.5volts would be dangerous,
as gassing would be severe, and the battery would soon
CHARGE RATE CALCULATIONS
in the table above)
Expect that a
powerful model of car battery might peak with a 40amp
charge rate if battery voltage was
pushed to 14.2 volts or higher. (But 30 to 35 amps are more realistic figures.)
battery charging, the battery that would accept 40 amps at
14.3 volts might reach peak charging rate at only 25 to
30amps, with our wiring system in place.
The reduction would help to reduce battery gassing.
example calculation at 40amps charge rate is a little on
the high side of charging current that a normal car
battery will accept at 13.74volts, but these numbers are
getting close to the maximum we might see when recharging
a powerful model of battery.
CHARGE RATE CALCULATIONS
in the table above)
the battery begins to recover and gain charge condition,
it accepts less current flow.
And the amount of voltage drop at the battery
charging wire is a much smaller amount as charging current
the 20amp charge rate, voltage drop in the battery
charging wire is under three tenths of a volt.
CHARGE RATE CALCULATIONS
in the table above)
With the battery accepting only 5 amps current at
14.23volts, it is now approaching a charged condition.
Notice that the small amount of resistance at the
10feet long 10gauge battery charging wire is no longer
causing much voltage drop.
½ AMP CHARGE RATE CALCULATIONS
in the table above)
And with the battery accepting only 1.5amps of
current at 14.28volts, the battery is about fully charged.
(If we were working with a workshop battery
charger, we would stop charging the battery now.)
And with the battery nearly topped off with charge,
the small amount of resistance in the 10feet long 10gauge
battery charging wire does not have significant effect.
The battery will be maintained at a fully charged
condition when driving with this system.
performance is excellent with our minimum recommendations
for the battery charging wire.
It’s a system much appreciated by those of us who
don’t like occurrences such as corrosion at the battery
area, battery gassing, short battery life, and alternators
damaged with overheating.
many years of real world experience, the NEW SYSTEM has
worked very well. And
for years now, customers have enjoyed it with installation
of our trunk mount battery system. (The battery charging and power distribution was purposely
built into our trunk mount battery system years ago, we
have been selling it since 1989 but have never before told
people how good it really is.)
Electrical system performance and reducing battery
gas in the trunk were considerations when our original
trunk mount battery system was assembled back in the
1980’s. This never published before tech feature merely explains
existing advantages about our trunk mount battery system!
customers with the battery up front have also enjoyed the
“NEW SYSTEM,” and they have installed it using an
older M.A.D. diagram titled “IMPROVED SYSTEM,” which
was actually published in a Chevy High Performance
magazine feature, a few years ago.
(The story title was “BRIGHT EYES.”)
all standards the system should work well, because actual
calculations provide support for the system function and
It really is about time that we let people know
about these special attributes of a system that so many
people have enjoyed for years. 100amp rated alternators used to be “hot stuff,” nowadays
100amp available output is becoming ordinary.
A few short years ago, it was rare to see our
favorite models of classic cars equipped with electric
radiator fans, now they are popular and the fans are more
powerful than ever. And
with all this electrical power produced and used, wiring
system design is more important than ever
it really was about time.
Sorry for the delay with writing about this topic
for all the many friends of Mark Hamilton and M.A.D.
SUMMARY of the CHEVY MAIN POWER SYSTEM
(And also the
“NEW SYSTEM, by M.A.D.)
obvious that we should consider more than just battery
charging, when working with the alternator system.
Certainly charging the battery is an important job
that cannot be ignored.
But charging the battery is the simple part.
Because the original dash area main power-up wire
is on the opposite side of the car from the battery;
allowing the alternator-voltage regulator system to
maintain the power distribution area at about 14 volts
deserves the most attention.
Voltage at the battery will eventually follow what
happens at the main power distribution hub.
ignition and electrical system performance is dependent
upon the amount of voltage delivered to electrical system
Weak voltage levels will result with weak
Performance can be measured by reading voltage at
the part, while the part is powered-up and operating.
And with most systems, we are looking for about
In this Chevy system, we must to a good job of
maintaining the “power distribution hub” at about 14
volts even when electrical demands are heavy.
also in this unique Chevy wiring system, the “battery
charging wire” does not handle the amount of alternator
output used to support the electrical system.
The battery charging wire in this system is a rare
occasion when a little resistance caused by a long length
of wire is okay.
It’s not a performance issue that will affect
brightness of lights or strength of ignition and other
accessories in this system, because the charging wire does
not support those items.
And because it can slow the battery charging rate,
a little resistance at the charging wire can actually
provide a cushion when recharging the battery while
NEW SYSTEM works in the same way as the original Chevy
system, but the NEW SYSTEM has many advantages over the
It improves overall performance, including better
voltage at the dash area.
The NEW SYSTEM provides a very good “main
frame” for adding accessories.
It also fits in with battery relocation.
And the NEW SYSTEM can handle more powerful
alternators than the original wiring system.
And that about completes this analysis of “THE
ORIGINAL CHEVY SYSTEM” and also recommendations in the
“NEW SYSTEM” by M.A.D.
The original wiring system will work fine with the
alternators up to 63amps gross output rating, which is the
most powerful of a typically equipped Chevy that used this
The “NEW SYSTEM” can handle more powerful
alternators and support more accessories.