I have installed a Victron 3000/120/12/50 into a new van build and when I have it plugged into a 20 amp shore power and have 3-4 amps (in breaker panel) already turned on with breaker; I turn on the inverter and it trips always. Now the inverter shows low battery when it trips......why when the batteries are full and the shore power is on. If I shut the two breakers off and turn on the inverter first before I flip a couple low amperage breakers the inverter will not kick off. Any ideas. Thx