So I was called out a couple of weeks ago to assist a friend of mine who is an ATV Safety Course instructor. Rhino was DOA on arrival to training site - battery deader than dead. Fortunately I also carry a starter pack that got me going but instruments acted crazy all day due to what I thought was a bad battery. Turns out battery was just heavily discharged (due to inactivity) so I slow charged it the following day and brought it back to life.
Since I don't have the luxury of extra garage space, the Rhino pretty much stays covered on a trailer when not in use - which is sadly most of the time. To help prevent future battery issues I installed a 30 watt solar panel on the trailer. The attached link shows the details.