How many cranking amps?

[Birmingham Bill]

I have been told most cars produce around 13-13.8 amps, and should not drop below 13 amps. Just curious, how many amps are actually needed to crank the car? Thanks.

[911pcars]

Originally posted by Birmingham Bill
I have been told most cars produce around 13-13.8 amps, and should not drop below 13 amps. Just curious, how many amps are actually needed to crank the car? Thanks.

That's probably 13-13.8 volts. Under running conditions, the voltage produced by the alternator could be in the 14's depending on the battery's state of charge and the number and type of electrical accessories in use. Voltage is pressure. Amps is current, and current is what's needed to crank the engine; maybe 150 amps or so from the storage battery. During cranking, a good battery shouldn't drop below 9 volts.

Hope this helps,
Sherwood

[Birmingham Bill]

Thanks, Sherwood. I sure appeciate your time. Bill

[wcc]

The cold cranking amps really depends on where you are located. That's what you should really look at when buying a battery. I live in Michigan and I wouldn't run anything less than 500 cold cranking amps (CCA). Summer time anything works, but in the winter you gotta have lots of CCA.

Both my P-cars have batteries from the PO and I only drive them in the summer. But when it's time to change them out I'm going to get a battery around 300 CCA. Unless you live somewhere warm all year around I wouldn't go with anything less.

Good Luck!

[Gunter]

Birmingham Bill:
If you don't have a Repair Manual for your 964, get one and read it from cover to cover.
It'll help you understand your car much better.

[911pcars]

"....and I wouldn't run anything less than 500 cold cranking amps (CCA). Summer time anything works, but in the winter you gotta have lots of CCA."

I agree, but to avoid any confusion, the CCA rating is the capacity of a battery to create current at low temperature. The current required to rotate the starter motor is an amount independent of the battery rating.

Sherwood