How do i hook up two batteries to my alternator in my car?

Question

How do i hook up two batteries to my alternator in my car?

Answer 1

You must go to auto supply or wal mart and get a BATTERY ISOLATOR with the amperage you wish to handle. The instructions for connecting it will be supplied with the isolator.

Answer 2

A second battery is never a good idea as it's an added strain on the alternator to charge two batteries AND supply power for the car. The ONLY time a second battery is useful is if the audio system is to be used with the car off.

If you need more current, get a high output alternator...

If your total system power is 1200 watts RMS or more,  you will need to:

1. Upgrade the alternator to a high output alternator

2. Upgrade to a heavy duty deep cycle battery

3. Upgrade the "Big 3" - that is to replace (or add to) the power wire between the battery and alternator, the ground from the battery to the chassis and the ground strap from the engine/tranny to the chassis with at least 2 AWG wire.

Failure to do this will result in the early death of the alternator  as it will eventually fail.

Here is a guide that will calculate what size alternator and power wires you need http://www.box.net/shared/uchv4dbk88

You will need Microsoft Excel. If you don't have Excel, use this link

http://www.box.net/shared/nkkw1dhk4g