FW: Fuse Amperage??? for a fuse between the battery and the car.

[Huw Powell]

> This is an interesting question.
>
> Doesn't a starter motor present pretty close to a short to the battery
> (600 amps limited by the source impedance of the battery)?

One that is answered better by facts than theory, considering they are
pretty easy to come by.

I once had a starter that was on its way out, combining with some tuning
issues, to make hot restarts difficult.

A current meter on the cable showed peaks of 200 amps while cranking.
This is way too high.

We also have a lister running a 115A fuse with no starting/cranking
trouble unless the car was in gear.

to draw 100 amps at 12 volts, you're talking roughly a 1/8 ohm load,
which does not sound like much, but it is not a "dead short."  That 1/8
ohm, of course, is the combined resistance of the starter, the wires,
and the battery.

I like the 100-120 amp fuse/breaker idea - remember, there are times,
theoretically, when you might want to dump your full alternator output
(90-130A) into the battery via that circuit.

--
Huw Powell

http://www.humanspeakers.com/

http://www.humanthoughts.org/