I have a Zion SRT 2018 with 2 ecotreks and 300w roof solar. Being a promaster the chassis battery doesn't last as long as I store it for, so I've bought a battery maintainer, which I want to connect to the solar and the chassis battery. Does anyone know where I would connect it on the solar/house battery side? I'd prefer not to carry another solar panel with me when I already have a roof full doing nothing in storage. I do mean actually where, not 'attach the wire to the positive terminal', but where is the connecting point and how do I get to it? TIA..