Hi all, I wanted to find out if it's ok to run a second battery in my car without having to change the alternatoR.

Asked by May 06, 2015 at 07:04 PM about the 2007 Volkswagen Citi

Question type: Car Customization

I usually play sound with the car moving at
high volumes, but would like to be able to
pump the sound for a good 2 hours without
draining the battery, or without having the
car on. I currently have 2 6500w amps,  1 of
them being a 4 channel which runs split
systems for my doors which about 300w
and the other a monoblock which runs a
single 5000w 12". Please advise. Thanks in
advance for any and all answers.

1 Answer


If you're wattage numbers are correct, you would need a trunk-full of batteries to run that system for two hours. If you actually meant 650W amps, then it's possible. You would still need 3 Optima batteries (or other deep cycle units) to meet the amp-hour requirement and possibly and external charging system to avoid over-loading the alternator. While parked, the audio batteries would be charged to capacity...while driving the alternator would only "see" fully charged batteries and support them under normal charging while driving. Once parked for the 2 hours of music, the audio batteries should be isolated from the car's charging system and can then operate only the audio system without draining the car. I recommend seeking the advice of someone locally with extreme car audio experience. There's a lot of things that can go wrong with this much electricity in a car. Play it safe...get all the information you can FIRST!

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