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30 Closed Cab PU · 02-25-2020, 12:14 PM

Correct the below if I am wrong.

The math

Assume the starter draws 40 amps at 6 volts (probably not correct but used for comparison of 6v vs. 12v)

6V: R (Resistance) = Volts (E)/Current (I), 6/40 = .15 ohms
W (Power Watts) = I x E, 6 x 40 = 240 Watts

12V: R does not change, same starter as above = .15 ohms
I = E/R, 12/.15 = 80 amps
P = I x E, 80 x 12 = 960 Watts

So when going from 6 Volts to 12 volts using the same starter, Current doubles and Power quadruples

Running a 6 V starter under load continuously like a motor at 12 Volts would destroy the starter . Since it is only used intermittently for a few seconds, it does not heat up dangerously and is allowed to cool off even at 12 Volts.

02-25-2020, 12:14 PM	#11
30 Closed Cab PU Senior Member Join Date: Aug 2018 Posts: 2,332	Re: I wish I would have waited Correct the below if I am wrong. The math Assume the starter draws 40 amps at 6 volts (probably not correct but used for comparison of 6v vs. 12v) 6V: R (Resistance) = Volts (E)/Current (I), 6/40 = .15 ohms W (Power Watts) = I x E, 6 x 40 = 240 Watts 12V: R does not change, same starter as above = .15 ohms I = E/R, 12/.15 = 80 amps P = I x E, 80 x 12 = 960 Watts So when going from 6 Volts to 12 volts using the same starter, Current doubles and Power quadruples Running a 6 V starter under load continuously like a motor at 12 Volts would destroy the starter . Since it is only used intermittently for a few seconds, it does not heat up dangerously and is allowed to cool off even at 12 Volts.