I'd like to leverage a spare 1,500 watt 12v inverter on cloudy days as AC input for PowerAssist while we drive. The 12v inverter is powered by the alternator in my F350 and it works perfectly. The challenge is when I connect the output of the 12v inverter to the input of the MultiPlus. The MultiPlus clicks, the 12v inverter maxes its load, and nothing further happens. I've set the input limit to 9 amps. What am I missing?