Looking for any tips on troubleshooting a battery issue I am having and I will be working through tonite to try and fix in time for a trip this next weekend. Checked the camper this weekend and found the batteries dead which was a surprise, I thought the battery switch was off and should have been sitting at about a 75% charge after watching my Victron patterns. Related or unrelated clue I tried plugging the camper into a 20amp extension cord outlet thinking it should be able to run the inverter and charge things back up. The GFI would pop after about an minute no matter how much I checked to make sure everything was turned off that might be tripping the breaker with overload like AC, water heater etc. On my old camper I was always able to plug in using the same procedure and never had the GFI trip issue. I hooked up my portable generator and plugged the camper in that way for two hours to try and start the recharge process and the camper worked when running off generator power. I shut off the generator and checked to see what my Victron said for battery state and everything is dead again. Tonight when I have more time, I am going to check the WFCO battery charger and see if it has any power output. Is their a fuse that would affect the charging I should be looking for? Anyone have any other tips as I try to get this fixed ASAP for next week's trip? I don't know if that popping GFI is a clue to this overall problem? I've always been able to plug in and kept my batteries charged and yes i've used proper 12ga 50ft extension cords that should have been able to carry the current without significant voltage drop or heat etc.

Thanks
Larry