The advise about the battery tender is good. I have them on all my toys...........the Harleys, 4 wheeler, etc.
The nice part about the tender vs. a standard trickle charger is the tender will charge to full then place a working draw on the battery then repeat this. I have had one on my '01 Roadking from day one, it has the original battery in it (8yrs now) I just recently ran a test on the battery.........still perfect. I usually plug them in if I am not going to use any of them in more than a weeks time.
Wal Mart has them by Black & Decker for @ $18 and change, comes with all the hardware and jumper leads. I have used one on my p/u battery when it is stored for the winter months, no problems so far.
FDXX75