2 batteries, 1 maintainer

[Jaxonalden]

Of course, rotating a trickle charging battery maintainer is better than not. Press on. I have my lawn mower, Harley, VW bug, Boxster and a spare 12 v battery all on maintainers.

[gschotland]

Plug this into both cars and let it go, no rotating.

http://batterytender.com/automotive/2-bank-international-charger-usa-western-hemisphere.html

I've got a single bank unit that my Dad and I share (he uses it most of the time) and it works well.