I didnt have any problems untill i changed the battery, now when my car heats up, and when i press on the breaks the battery voltage drops. This also happens at idle speed though its not offten. The car stalls when i back up, though only when the car is warmed up. I had my alternator tested and thats good, i replaced the starter as well as changed the battery terminals. The car runs great when its cold, I need help for i am unable to keep changeing out parts. I have an after market sterio system, and alarm installed and when i turn up the volume on my stero it shuts off the stero that is. Any ideas as to whats cauesing this to happen?

 

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Do you have an amp or cross-overs for your stereo? you may need to get a capacitor so you aren't drawing so much voltage from your battery to your stereo. The increased draw from the brake lights, stereo, reverse lights are probably the reason it keeps dying. If the battery is being used to power all that auxiliary crap, then it may not have enough left for the car's factory electronics.