How old is the battery? I would do a load test on it first. Turn the key on and turn the lights on, if it drops badly then the battery is probably bad. Im guessing it is more of a battery issue than a charging. Charge the battery and see if it goes up to about 15 volts. If it does then the battery is probably sulfated and needs replaced. If you want you can try trickle charging it first to try and save a little money.
2008 Can Am DS450
PRM Baja Bumper and Skid
2007 Honda Rincon 680
Fuel Injected
ITP Mudlites
Hopefully some more goodies soon
1986 Honda ATC 250SX
Knobby tires all-round
otherwise.................... STOCK