how do you hook up a second battery in your car.?

Question

do you run the batteries in series or parallel?

Answer 1

2 6volt batterys in series to get to 12 volts two 12 volt batteries parallel to increace amps ,,,,,,, i have an isolater and hooked up an extra starter relay so both batteries crank bonis if i leave my lights on to long and 1 goes dead i can flip a switch and start off the other battery

Answer 2

Parallel

Answer 3

Parrell if you want 12 volts,series if you want 24 volts as a diesel. However diesel have a switch to let the other things run on 12 volts.

Answer 4

They sell kits to do this safely at autoparts stores and RV shops.

You need to hook negative to negative, positive to positive. This will result in a 12 volt output.

If you hook negative to positive, etc., you will have a 24 volt battery.

Answer 5

Pos. - Pos.
Neg. - Neg.