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

 

100% 12.7 - 13.2v
75% 12.4v
50% 12.2v
25% 12.0v
Discharged 0 - 11.9v

Hold your voltmeter to the terminals on the battery.
Now push the starter button and watch what the voltage drops to.
It doesn't matter if the bike starts or not, what you're looking for is a voltage reading.

A healthy 12 volt motorcycle battery should maintain a range from 9.5 - 10.5 volts under the load for a good 20 - 30 seconds straight.
If the battery holds and then steadily drops in voltage, there is a problem

if it drops below 9.5 the battery is dead ----

get the scoot running - with the meter hooked up it should read more voltage as you raise the rpm --- this will let you know that it is charging or tryin to charge the battery


or just goto auto parts store have them load test it

 

Have you checked the charging voltage?
Check for 13.5v at the battery at 2000rpm.

 

You have a bad stator, regulator, or both.
With the bike running at at fast idle, you should measure between 13.8 - 14.8 VDC. Anything thing lower than 13.8 means your battery is got being recharged.

 

Well, that's my fear. I'll check all of those values again using the techniques described above. I'll look in the FSM and see if there are voltage output listings for the stator and regulator and checkpoints for the multimeter.

What I don't get is, why aren't there any codes when I put the bike in diagnostic mode? I would think that the bike would be smart enough to tell me which components are bad without having to go through all of this manual troubleshooting. After a half-a-goodnight's sleep, I think this is what bothers me more than anything else. Why no diag codes? I would think that a bad/failing stator or a bad/failing regulator or even a bad/failing battery would rate codes of their own.

 

Update. So, I went out this morning and checked. The battery was at 11.20V from + pole to ground/jug, but it still had enough juice to turn over. While cranking, the voltage dropped as low as 6.8 V but then rebounded instantly when the engine started.

Initially, the voltage between + term and ground was 13.8 V, and ran as high as 13.88 V at 2K rpm. However, as the bike warmed up, the voltage dropped to 11.97 and stayed close to that no matter the revs. it didn't matter if I turned it off and then back on, it stayed consistent in that range.

I'm going to repeat the cold engine test after lunch. It will be interesting to see if the charging system runs at 13.8 V while cold but drops as the engine warms.

And still no codes.

So, I might have a bad battery, but I don't think so. Next, I need to figure out if it's the voltage regulator or the stator that's the culprit. In the interim, I'm going to recharge the battery.

 

The stator output should ~20 VAC at idle and climb well above 60 VAC as you increase RPM. If the stator does 30VAC at a fast idle (~1500 RPM), it should be good.

 

You got a failed battery. Buy yourself a new battery.....

 

Read up on what your battery voltage should be at idle, when the bike is turned off, and open circuit (disconnected) The values you listed are a bit low. I would seriously consider a voltage regulator problem. Unfortunately, the values of your charging/static voltage tests are the only way to test a voltage regulator. If your voltage regulator fails and you ignore it too long, stator replacement is soon to follow. You can do a quick check of your stator by disconnecting it with the bike turned off and check continuity through the windings. Some resistance, but not much should be your answer, I'm thinking less than 50 ohms. Check continuity from one lead of your stator to the ground on the bike. A reading in the mega ohms (million) range would be good, infinity even better

 

Also check to make sure you are getting a good earth ground at the regulator.


Here is a good read too.


http://www.harley-davidson-hangout.c...ng-system.html