Battery tender.....
Works great! I use the small one found typically at the motorcycle shop.
Routinely, I plug it in if it is going to be a while before flying again or if I have been messing with the avionics.---AKA trying to figure out GRT menu systems and "Which button to push when" .
My -8 has the battery in the rear, I took the plug in extension lead and routed it back to the passenger compartment for easy use.
Now if you have left the master on it will take an overnight to charge but no worries of overheating, etc.
The Sears chargers are fine when more/faster juice is needed and have the distinction of a 3 year low hassle warranty and relatively low prices.