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

Originally Posted by Roni

I checked the stator. The resistance from plug to ground is infinite from both sides of the plug, and both sides of the plug together produce 0 ohms. Once battery is sufficiently charged that it can start the bike, I'll do a voltage output reading for the stator. While I'm out there, I'll check the ground wire on the regulator as well.

I got the battery charged, installed and the bike started. The output from the stator was 30-32 V at idle and up to 80 V at ~3K rpms. (It's my guess about the rpms. I could be off by a few hundred rpms either way. It sounded like 3K, but how could I tell? I'm used to hearing it in the saddle with my 3/4 helmet, not with my uncovered ears by the front header pipe. You must either be a simian or far more talented that I am in order to hold the multimeter, hold the probes in the stator plug, twist the throttle and read both the tach and the multimeter simultaneously.)

So, I guess that means the stator is in good shape. Next is to verify the regulator/rectifier. I suppose the real test of the regulator at this point is the output at the battery, which we already know is well below 14 V most of the time whether under load or at an idle. I'm going to double check the connections, though, just to be sure.

BTW, fresh from the charger, the battery shows 13.1 V on the multimeter.

Originally Posted by Darren Dyna

Hi I had endless trouble with my regulator. It was a bad earth on the rear fender what initially caused the issue. It was spiking voltage and died on ame a couple of times on the road. I replaced the ground lead and regulator, worked great for around 2 years or so. Then it went again . It was both the regulator and stator what packed in this time, just been for a ride and when i got it home the pigtail on the battery tender was flashing like the battery was dead?? Tried to start it and nothing , lucky to get home actually . On initial inspection and testing the regulator i found out it was letting back through the regulator which shouldnt happen. So i ordered a new one and put it on and still no charge!!! so that pointed to the stator , after doing the engine run test with the meter it was differing quite alot with voltage . on further inspection one of the wireson the stator plug was green so rust had travelled down the wire and trashed the stator . after a fiddly removal of the stator plug i cut the wires back as far as i could and reattached then (soldered). Plugged it back in started the bike and still the same issue , they had rotted through in the case which i couldnt see.. Stator came within a week and i'd sorted it within a few hours . Bingo the bike is back up and running and the voltage is now at correct level . i have just purchased a little meter that connects to the battery to show me the voltage charge going into the battery while riding , so if it starts to drop while riding im heading home !! And doubles as a usb charger ..

Originally Posted by Darren Dyna

Hi I had endless trouble with my regulator.