Charging ancillary battery on boat.
I have a motorcycle battery that I use for powering my dinghy inflator.
When this needs charging is it OK to simply connect it in parallel to my boat's engine or domestic battery? Thus charging it either from the boat's AC battery charger or charging it while running the engine.
I would have thought it was Ok but an "expert" tells me one should never connect different size batteries in parallel for any reason.
Don't supppose it matters too much if the m/cycle battery doesn't gat a full charge as long as it's enough to inflate the dinghy.
Thanks in anticipation
Life may not be the party you wanted but while here you may as well dance.