Hi, I can only guess by using my trailer for an example. My radio does not have any subwoofers or amplifiers connected to it, so the draw from the radio is practically nothing. I know the water pump draws a lot of power when actually pumping. I have incandescent lights in my trailer and we usually only have a few on at a time. If I had all of my lights on, as you stated, I would become blind and my trailer would melt from all the heat. [slight exaggeration] With all of my lights on, radio on, and water pump on, I believe it would draw faster from my batteries than my converter could put out. Therefore draining the batteries.