Need a little help with an electrical problem. Recently had an audio system installed with speakers, subs and an amp. It was done by a reputable audio place, not a teenager at best buy. Long story short, I took the car into my mechanic for what I thought was a battery/alternator problem. (Car would not start if sat for longer than 3-4 days) They tested the battery and said it had a dead cell. and said my alternator was only charging at 13 volts. I replaced the battery, and had the alternator rebuilt. With new battery and rebuilt alternator, it was overcharging the battery at 17 volts. The only way my mechanic could stop this was to disconnect the amp for my subs. Taking it back to the audio installer, but curious if anyone has any ideas? Thanks in advance.