Home Made Voltage Booster charges TT battery off 7-pin

I personally think you are just creating a parasitic load that adds nothing to your batteries. If you measure the actual current going into the batteries, I bet you find it higher without your device. Having said that, if you were to put a dc-dc switching power supply at the front of the truck and upped it to 72 volts and then another one at the rv to drop it back to 14+ volts, then you have done something.