I just had a fairly long conversation about my Magnum system. The purpose of an inverter is to provide 110 volt power fom the 12 volt system. If you are plugged in to 110 volt (30 amp or 50 amp) or on generator power, you do not need to have your inverter turned on. Your 110 volt power is coming from shore line or generator. Depending on how many house batteries you have, your system (under setup) can be programmed for different time periods of charging. When the voltage level drops to 12.6 volts the charger aspect of the inverter will begin to charge your house batteries. It will charge for the amount of time programmed and go through several different phases of charging depending on the condition of your batteries. The inverter does not need to be tuned for the charger aspect of it to function. After the programmed time, it will stop charging. If your batteries will not hold a charge, as mine were not, I had a "load test" performed on them and found a dead battery among them. Replaced that battery and have not had any charging issues. The technical support department at Magnum Sine was very helpful and informative. Call them if you have any questions. Their on hold time can be lengthy, I tried the"have them call me back" feature and found if I just stay on hold, I get helped faster that to use their call me back system.