Charger on, 12 volt system shut off using deactivate switches in main panel. Only two items running are the fridge on 120v and the charger, everything else off. Group 27 AGM batteries installed in November of 06. I checked the output posts on the charger and they read battery voltage(after charging using mains). Input was 122v. Did not have an ammeter to check for draw but will next trip. Open for suggestions. I am thinking the charger has a bad diode possibly. But, I am obviously not very knowledgeable in this area.