Can I charge this auxiliary battery using an AC battery charger plugged into one of the cigarette lighter receptacles in the cabin?  I'll be camping -- with no driving -- for a week, in a campground with AC, and I'd like to be able to use the battery for charging my electronics (iPad, phone) and running a DC fan (15 watt).  I won't be using the battery to run a fridge or cooler.  Just wondering if it's recommended to 'trickle charge' this battery if it's being used for camping, and the van won't be driven, for say a week or so.