2 batteries

[gotgohan]

I once asked if I should do this and I got different opinion from someone and I just wanted to double check. I have 2 top of the line interstate batteries for my cavalier in my trunk atm. Only one is hooked up to the car, and it does really good except for the fact that if I have lights on and brake it dims all the lights. Think 2 batteries would help, or just get a new alternator still?

 

[Aussie]

You should probably get a better alternator. Your system isn't made to handle two batteries in the same circuit.