Originally Posted by Roni

Okay, everybody, here's your opportunity to have a laugh at my expense. I'm certain that I've got a dead battery. Everything points in that direction. In fact, if this were a car instead of a bike, I wouldn't even bother. I would just change the battery and be done with it.

So, here's the scenario. A few days ago, the engine light and the battery light come on while I'm driving to work. After work, half expecting the bike not to start, I was pleasantly surprised to find that the bike starts normally. About half way home, the engine light and battery light come on again. Okay, so I've got battery problems.

So far, so good. I pull the battery and slap it on the charger. Once the charger tells me it's at 100%, I check it with the multimeter. It's reading 13.4 V. I check the date on the battery. It's dated July 2012, which would put it at 25 months. Maybe it's not the battery after all.

I put the charged battery back in the bike and take it for a test spin. About 5 miles out, the lights come on again, so I finish the loop. I get home and check the battery in the bike, it's at 10.8 V. Great. It could still be the battery or the charging system.

Here's the kicker. I check for codes. No codes. I either get NO RSP or NONE.

So, I go outside to play with the bike some more. The battery is at 12.2 V, which is interesting because it was at 10.8 earlier. I start the bike up, and check between the Pos terminal and the jugs and the bike is reading at 12.2 V. I run the engine for a while and it's down to 11.9. A little while later, it's down to 11.5 V. All indications of a charging system failure.

I turn the bike off, go eat dinner, come back out about an hour later and -- guess what! -- the battery's back to 12.2 V, which technically is a dead battery, but I'm pretty sure that I can charge it up to 13 V. And I leave the multimeter on the + terminal and ground while the bike is running, and you can slowly watch the voltage drain off, about 0.01 volts every 15-20 seconds or so at an idle, faster if I revved the engine.

Like I said, if it weren't for all of the damned HD diagnostic stuff, I would start with a new battery. However, all indications, especially the slow drain while running indicates a weak charging system, maybe a bad voltage regulator or (hopefully not) a bad stator. But there are no codes, even after the engine and battery lights come on. I would expect codes every time one of those lights come on, but Talulah isn't giving up her secrets.

As a sanity check, I have checked all of the connections at the battery and at the other ends of the cables, and they are tight. I haven't pulled them, cleaned them and reseated them (although according to the Service Manual, that's what you are supposed to do in order to remove the battery), but I will tomorrow after work.

So, what's a fella to make of this? I'll go buy a new battery if I need to do so, but I hate to replace a 25 month old battery, especially if it's not the battery. I still need to read up on how to check the voltages on the charging system, but I'm wondering if I've missed something obvious here.

BTW, in all of the years that I've been riding, I've never actually had a bike battery go bad on me. Yeah, I usually replace the bike before I replace the battery. I guess I've just been lucky to date.a