Thor Forums

[javelin]

Hi, your converter (120VAC converted to 12vdc) is basically the 12vdc battery charger for both the coach and chassis batteries (in most coaches with appropriate battery control electronics) and since you say you have a BIM then it should control a relay that connects or disconnects the coach and chassis batteries together depending on charging or no charging conditions. It is possible that if the BIM is faulty it may have left the relay connection “on” between coach and chassis batteries (or that relay may be shorted closed), which might account for the discharge of both battery strings overnight........especially if the converter (battery charger) was not on or for some reason is not connecting to the coach batteries to charge like it should. If you have a BIM do you also have separate coach and chassis battery on/off switches near the door of your coach? Even if you only have a use/store switch make sure the coach battery switch (or use/store switch) is “on” so the converter will connect to the batteries. There are other reasons why the converter may not charge batteries also, but when you have fully charged your battery sets (with external charger) then use a voltmeter to ensure they are charging properly from the coach converter on shore power as a minimum.