I use a battery tender while my Georgetown is in storage (2 12 V batteries). And I hook the positive to the front battery and the negative to the rear most connection. Works great.
On my unit, a 2005, I must not have a very smart on board charger because I boiled my old batteries dry in just a few days. Ended up shortening their life. Now use the battery tender on the newer ones.
When I go to Florida in the winter, I leave my van in the storage unit with the battery tender to keep that battery alive until I return.
I also put a battery tender on the battery on my golf cart over the winter.
I am a big fan of battery tenders.
Life is a journey, not a destination.
2005 Georgetown 359ts
Bill & Virginia, Kentucky
Nights camped in 2011...78 , 2012...73,
Nights camped in 2013...123, 2014 ...101