For the last month or so I've been keeping my chassis battery charged while my van it connected to shore power by using a small jumper cable to connect the two outer posts of my isolator.
I remove it when I use my van.
I don't know if this is a good idea or not but it works for me.
If anyone knows a reason why I shouldn't do this please let me know.
I'll still use my Battery Minders for longer lay ups but this is quicker. I do not use my van regularly so I have to maintain the chassis battery.
I measure 13.4 volts at the chassis battery when connected this way. Your converter or charger has to have a "float" mode if not you could over charge the battery.