I think it's just a bad battery.
Maybe you ned a fully charged battery to do a proper test?
Yeah I think the battery is most likely bad or getting there. I have been meaning to replace it with a new sealed battery. Although it does seem that the alternator should power the electrical system even if the battery were dead. Which would mean either the alternator or the regulator is bad. The regulator is built in with the rectifier. There is a rectifier regulator unit test in the service manual. It says to check voltage at battery with engine a 3000 RPMs and there should be between 12.2 and 13.5 volts. I guess I'll try replacing the battery. I hope I can find one in town and not have to order one.
A new sealed or gel battery is the way to go. Did you keep the OEM battery on the 'tender whenever the G5 sat?
So battery is probably bad, but that doesn't explain the bike cutting out, backfiring, and now dying at idle. Chris
I had something similar to this last summer when I spluttered home on a flat battery. In my case it was duff wiring rather than a duff battery as in the wiring was wrong from the day it left the factory allowing it to carry on running directly off the battery with all fuses blown and no charging. Once the battery is flat it stops running. Leave it half an hour and it recharges itself just enough to run a bit longer but then it will stop again as there isn't enough power to run the fuel pump. That's what was happening to you too.