Originally Posted by Charley38
Just installed a second house battery in my 2019 Forester. When I hooked up the ground cable there was a small arc, even though the battery disconnect switch was in the off position. Something that bypasses the disconnect switch is drawing current from the house batteries. Does anyone know what this might be? Or can someone point me to a source for a coach wiring diagram?
Even if everything
is disconnected from the batteries
you will still get a small spark if they are at different levels of charge. The battery with more charge will be charging the other battery--current will flow, as evidenced by the small spark at the time of connection. If one battery is newer than the other, I'm not surprised.
You don't need to "fix" anything, but if you have an old battery and a new one, the new one may be limited to the charge/voltage the old one can provide.