As said previously mentioned your chassis batteries are probably not charged while on shore power and parasitic loads are draining them. Google LSL products and take a look at the Amp-L-Start or the Trik-L-Start. The amp-l-start is a little more heavy duty but either will do the job. Very simple install and excellent customer service. After initial install it will take a couple of days for the chassis batteries to charge up but after that they will always stay fully charged as long as you are plugged into shore power and your inverter is functioning properly.
I installed the trik-l-start 6 yrs ago and have never had a problem again.
Blessings; kdk
