What coach do you have or did I miss it? I have a Freedom Elite 22FE and when I plug into my 20 amp garage outlet shore power, the use switch automatically comes on when I set the breaker. As far as over charging your batteries, this is all depending on the converters output as if it's working properly or not. If working properly, will not over charge batteries. if NOT will ruin your batteries. As far as storing my rig, I don't use my shore power because I don't trust it even though works o.k. I have my use switch off and use a Battery Tender trickle charger of course making sure batteries are full of water 1st. I've use a Battery Tender on other cars and a truck I have had left/stored in garage in other house in another state for up to 6 months with no problems of over charging etc. Best little device around and will charge, trickle charge automatically shut off when batteries are up, turn back on when they drop down. Battery Tenders have been around a long time and like I say, used them for years for car stored in winter season in WA. state and another stored in summers in AZ. I just don't trust those darn converters they put in our R.V.'s.