Expert: Cleggsan - 2/17/2009

Question
how do/can i hook up a second batter to my car for my audio system? it is an 2003 toyota matrix.

Answer
I am not a fan of dual batteries because of the difference in charge and discharge rates.  You are much better off by using one battery with higher output.

In the case of the Matrix, there may not be room to mount another battery anyway.  And it must be nearby the original due to the IR drop of long wires if the second battery where other than next to the original.

Maybe you can get by with a Power Cap.  Or, maybe you should go to a car parts place and source out heavy duty truck battery that has twice the output of the stock Matrix battery.

What you should look for is a battery with the correct position of the terminals so it will connect into the same battery holder as the original and find one with about twice the amp.hour rating as the original battery.  Most small cars are around 50 AH.  Look for a 100 AH battery.   There is some danger the alternator cannot handle the necessary charge current, but I have not heard of it being a problem.

If you are going to run the sound up at high volumes over long periods of time you should think about replacing the stock alterntor with a heavy duty one, also.

Hope this helps.
C