Keeping batteries charged while not in use?

Simple, I bought one of those light sensative outdoor light timers, the kind with several settings, 2, 4, 6 and dawn till dusk. I also made up a little piece of wire with 2 alligator clips on it, I use it to bridge the 2 main terminals of the battery isolator relay.

I just plug it in between the coach and the outdoor plug and set it to 2 hours. Everyday at dusk all 3 batteries get a little top up. Not enough to harm them though.

Fully automatic and simple.