Quote:
Originally Posted by john charlton
Feel the coil and starter if you are having prolonged attempts you could cook the six volt battery if you overdo it but I never have . The jumper cables provide a voltage drop as does the starter motor so the coil does not get the full 12 volts anyway .
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Yes, the jumper cables provide a voltage drop. So does the car's 6V battery, which will absorb current to recharge itself. For a few seconds I don't think there is a concern, and yes, I've done it too. If someone wants to take the time and do an experiment, hook up a voltmeter to the wire coming off the starter or fuse block, and jump the car with 12V. Report back on what you see.
I'll bet a Heady Topper that it is considerably less than 12V. (It should vary with the state of charge of the 6V battery though)
I seem to remember checking cranking voltage once on a 12V modern system, and it was 9-10V. When you draw 200 amps for a big load like a starter, the voltage drops.
When I've jumped with 12V the starter did turn more smartly than with the 6V alone though.
I do agree to turn off all the light before doing this, no point tempting fate. If you need a jump, why are the lights on in the first place?