Quote:
Originally Posted by Jacksonlll
For the same power, a 12 volt system will draw half the current. If you double the voltage, current is halved. Power (watts)=voltagexcurrent.
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Quite so but it is not the whole story. it is the resistance that remains the same - not the power.
For the sake of the discussion, let's say the starter has a resistance of 1 ohm. That would mean it would draw 6 amps at 6 volts. (Resistance = voltage / current) If 12 volts (double) is connected across it, the resistance doesn't change and the current goes to 12 amps - double). As you say, the power = current x voltage. If both current
and voltage is doubled, the power is quadrupled.
In short, running a 6 volt starter on 12 volts will make it run at 4 times the power - that's why they crank so fast. With 4 times the power available, a smaller cable is desirable to restrict the current, even if only a little.