a little late, but most Oriellys will stock a good quality AGM motorcycle battery for about $90. if your charging system is working ... 13.8v-14.2v measured at battery while engine is revved up past idle. yes your charging system can charge intermittently. resting voltage for gel and AGM cells fully charged is about 12.8v. it's common for dead batteries to charge to 12.5v, then drop to 10.5v under load. battery at 12.5v resting is about 80% charged. when a new fully charged battery is installed. everything will return back to normal even on a system not charging. your bike will run normally until battery is depleted. which without lights will be about 1-2hours depending on amp hour rating. folks have been known to strap on a full size car battery. then run completely off battery until bike can be limped home.