Whenever I have cabin lights or cockpit lights on when I start engines they dim as much that they almost go out, also if bass is hitting then voltage goes up and down on port battery only. It's dimming in concert with the beat or the engine turning over. Put new deep cycle batteries in a month ago and installed a new deep cycle for the house battery last week. I don't think the batteries are wired in parallel they are dedicated one to each motor. The perko switch allows both batteries to be linked together but warns against it unless it's an emergency so one switch is on 1 and the other is on 2 as directed by switch box. Any insight would be appreciated.

It's the amp draw that does it. Starting the engines not much you can do, as far as when the bass hits, either an alternator with more amp output or a capacitor, 1 or 1.5 farad depending on the size or amount of amps will fix the dimming when the bass hits.

Thanks I'll let my audio guy know and see if that fixes it.

More batteries and/or a capacitor will help with the dimming lights.

Capacitor will be first fix, no room for another battery.

you have mini starters on the engine?that should help.plus,how clean are the power and grounds?

Don't know what mini starters are, all connections to the batteries are clean.

what size batteries do you have? I prefer 1000 amp'ers..


and yes its not good to run all the batteries on unless its a dead battery starting issue.

I think they are 800 deep cycle, wait that's the house battery. The engine batteries are 900 deep cycle.

thats plenty