ER?
er motors have a lower in-
ternal resistance than stock,
which in turn draws more
current. If you remember
from science class, power (in
watts) is voltage (E) multiplied
by the current (I). Since the
voltage cannot go any higher
than the battery’s 48volts (or
36volts), the current increas-
es in order to satisfy the
power demand of the motor.
Unfortunately, this is where
the resistance of the battery
cables come into play. As the
current increases in a con-
ductor, power is lost in the
form of heat at a rate of I2R,
where R is the cable resis-
tance. In an ideal cable and
to transfer max power, the
cable resistance (R) should be
zero ohms. Unfortunately all
cables have some resistance.
The cable resistance causes
the voltage to drop (E=IR)
and results in lost power to
the motor. The solution; in-
crease the size of the battery
cables (the larger the cable
the less the resistance). Of
course, the cable diameter
can only be increased with-
in reasonable mechanical
size limitations, but that is
what is required to reap the
full benefits of a high pow-
er aftermarket motor. Our
example used the locked
rotor current to explain the
worst case effects. They are
less drastic at partial throt-
tle, where the current draw
is significantly less. If you
want to do the drag racing,
burnouts, wheelies and such
with your cart though, you
will need the bigger cables to
supply the required massive
inrush of current to the mo-
tor. Although the resistance
of the cables seems tiny (#6
= 0.00047ohms/ft vs. #2 =
0.00015 ohms/ft), the voltage
drop is significant when large
currents are present, which
will reduce performance. So
for the high power motor
users out there, use large di-
ameter cables and keep them
as short as possible. Size will
matter to you.
Look for other articles by
Randy Wade and check out
www.digitaloverdrivesys-
tems.com regularly for news,
tips and performance prod-
ucts including the new Maxil-
ink Extreme Duty EV cables.
NOVEMBER 2019
29