get yourself a battery charger that has both a 6 amp, 2amp, 2amp trickle charge built into it. U can use if for your other battery needs, ie, lawn mower, car, cycle, etc..
If u don't wat the, charger get the battery tender...I find that my battery was doing the same thing and I put it on the 2 amp trickle charge overnight and it had a full charge vice a couple of hours on the charger..Also use your kickstart/decompressor and get the piston at tdc or jjust over tdc and start the bike in that position with your electric start...It makes it alot easier for the battert/electrics to kick in with a bit of help with downward motion of the crank and piston...This is common theme for these bikes...Worst case scenario is the battery but wouldn't go there yet without trying this...Mine is a 06 iron and when new the battery/electrics would start the bike at any piston position..That was short lived and I now try to rememmber to put the piston at tdc when I park it in the garage...Makes it easier to start and its a good thing to do re. wet sumping too....cheers