Here's the sequence of events/troubleshooting I've gone through recently.

1) The motorcycle wouldn't start and I found out the battery was dead

2) The later levels on the battery were low. I filled it, and charged the battery on a trickle charger.

3) Rode around a bit, and battery died again.

4) I assumed the battery was dead, and bought a new battery.

5) The new battery also died after a few days.

6) Traced the problem to the voltage regulator. 55 volts AC were going in, and 0.5 volts DC were coming out.

7) Note - while troubleshooting, I did notice some water inside one of the voltage regulator connectors (the one prong connector), but it did not seem corroded or damaged.

8) I replaced the voltage regulator and the system voltage read ~12.5 volts at idle.

9) I took out the new battery and reinstalled the old battery, as it fit better on the bike.

10) After a ride (or maybe a couple of short rides) I noticed the battery had boiled over and out. I pulled and checked the battery and found that 5 of the cells were still full of water; but one of them is completely dry.

11) I reinstalled the new battery and disconnected the charging system to ride the bike back to a garage where I can work on it.

I'm guessing the problem is one of two things: Either the old battery was just damaged and it shorted out and the charging system is now fine. Or, there's still a loose/damaged wire causing the charging system to malfunction.

What's the next step? How can I try to track down the problem from here?

Thanks!

P.S. 2000 Sportster 883 XLH

 

At the top of this Tech Electrical section there are two Stickies with tips on checking your charging system. They will lead you through a series of checks, which should isolate the culprit. You will need a multimeter, but it sounds as if you may already have one. I suggest you charge your new battery up off the bike, to give it the best start in life. While you're having problems it will thank you for a full charge!

 

Thanks. I'll go and read those stickies now.

But to be clear, I do have a multimeter. I tracked the charging problem to a dead voltage regulator. I replaced that voltage regulator and thought everything looked good.

But then the battery boiled over.

 

If your voltage regulator is putting out 12.5V at idle, It's out of spec. It should be above 13V. What does it look like at 2000RPM?

It should be in the 13-~14.8v range and increase with engine speed

 

nhrider1, it's possible I just read it wrong.

Today, I sprayed some contact cleaner on the voltage regulator connections and everything looks fine.

The battery was a bit low to start with, as to be expected as I rode it home without the voltage regulator connected -- 12.18 volts.

I spray on the connection cleaner and system voltage with the voltage regulator connected was between ~13 and 14.5 volts.

After running the bike for just a few minutes, then shutting off the engine the battery voltage (after settling) was 12.48 volts almost where it should be.

But the BIG question remaining is why did the previous battery boil over??

What if anything can I do to make sure there isn't some continuing problem which will cause the new battery to boil over too?

 

The old battery may be shorted internally.

 

It is also an old fashioned style, with cells that can be topped up with water! They don't have a very long service life.

Adam, next time you buy a battery buy an AGM one, which is sealed, higher performance and has a longer service life. That's a style of battery construction, not a brand - Absorption Glass Mat.

 

Thanks for the help and advice everyone.

Is there anything you can think of that I might be able to test?

Or, should I just assume the old battery had an issue which caused it to over boil and start riding the bike?

 

Adam, go through those two Stickies I mentioned in #2 - we're trying to help ya!

 

They seem to be checklists for what to test if your charging system isn't working. I did not test the resistance because I didn't fully understand it, but from looking at the voltages my charging system now seems fine.