It cut's off 12 volt feed into the MH when disconnected (or connected) to outside power. Yes you can push the disconnect button. Being hooked to electric, you have a charger built in to your inverter which keeps the storage batteries charged. You may use a 1/2 inch wrench to loosen the cable bolts, wearing gloves is a good idea and just disconnect the alleged bad battery, take it to nearest auto parts battery store Costco etc and exchange it for a new one. Stop at the auto store for some batter terminal lube and a battery terminal brush, clean the inside of the cable of all dirt, go put it back together being careful not to break the terminal off when you tighten the cable. http://carbatteryonline.net/how-to-change-a-car-battery.html