Looks like I may have an alternator problem...

One thing to keep in mind is that ignition uses less power at higher RPMs. Because of this, the battery voltage tends to creep up slightly when you rev it, even if the charging system is completely removed.

Since you had 14v the other day, it does seem like you have something flakey in the charging system.

Post edited by: loudhvx, at: 2006/02/08 19:41

Tested the stator again and it's still testing good. What else could cause it charge low? I can only get it in the 13v range holding the throttle at 4k for quite a while.

If I recall it should go to 14-15v right away when it's operating correctly.

Can I perform this test with the battery disconnected?

savedrider wrote:

Can I perform this test with the battery disconnected?

No. It could melt your electrical system.

Thanks for the help. I'm going to pull my electrical panel tomorrow and check some of the wiring on the back. I have a feeling it's a dirty connection. Not sure what else it could be unless my new rectifier/regulator took a dump.

All charging system troubleshooting starts with the battery. Your battery must be in good condition, otherwise it will throw off readings when the engine is running. I'd check the battery and then move to other areas...
Because you suddenly got good readings after you had gotten bad ones, and then bad readings again, I'm betting on a bad or corroded connection...

Yeah I have a feeling the battery might be on the way out. I pulled it today and threw it on the charger while I removed the electrical panel and throughly cleaned everything. Prior to putting the battery on the charger it was showing about 12.5v. I also tested the charging voltage again before taking the battery out and I was able to just barely get 14v at 4k rpms.

So after cleaning everything and checking over all the connections I took the battery off the charger and retested the charging system. Right away it hit 14.5v - 15v easily at 4k rpm whereas before I had to hold the throttle at 4k for a while to get the voltage to increase.

So now I'm not sure if cleaning everything helped or it was simply charging the battery. I will have to keep an eye on it and if it acts up again I will test the battery.

Post edited by: savedrider, at: 2006/02/09 19:53

I've been using dielectric grease on all my connections as I pull them apart and clean them hoping to keep them from getting corroded again... It'l help to waterproof them too...
Ain't nothing more frustrating than charging problems to deal with and figure out. There are some good charging system troubleshooting procedures posted here I believe in the articles section.

It's possible that your battery is pulling down the voltage on charging system. It may simply be discharged from sitting (or a bunch of really short rides 2 miles or less), or it may actually be slightly damaged internally.

It's also possible that one of the 3 phases is bad on the charging system. This could be caused by the reg/rect, or it could be the alternator.

Either way, when the battery is charged up, it's easier for the charging system to hit 14 volts. (what is the highest voltage it hits? 14.5? or closer to 14.0?)

Are you using the electric-start to start the bike? If so, then the battery is not totally toast.

When I checked right after taking the battery off the charger I was able to get to 15v easily.

I have always started the bike with the e-start since day one. I commute 14mi. each way to work 5 days a week and use my headlight both day and night.

It started acting up again and not pulling any charging voltage. I took the battery down today to have it tested at my local parts house. Their tester would not test it because it was not at peak charge.

I decided to buy a new battery anyway since I'm fairly confident it's my problem ($34.99 Champion/Exide 219 CCA @ 32 deg. F + $6 core fee). It came with acid and I took it home and filled it. Per the instructions it will take 6 hours to initially charge using my 2amp charger. I noticed the battery gets real warm after adding just the acid. I know charging and heat don't go together so I decided to wait until tomorrow to charge it. Also, since I will be home for at least 6 hours and able to monitor it.

I also threw my old battery on the charger today and retested the charging voltage before I left for work. It made it up to 14 - 15v, but took some time for the voltage to climb up there. When I tested it earlier in the day (before charging) it would barely move up to maybe 12.7v.

I really hope it's just a battery issue, I hate throwing money away on parts I didn't really need. I will take the old battery down to have it retested after charging it and see what the poop is.

Ok, this battery thing is really getting to me. I have a brand new battery in the bike. When the battery is fully charged I have no problem getting the proper charging voltage when I test.

Problem is after a few days of riding I check the charging voltage and it's only around 13.5v at 4k rpms.

Further testing of the battery (using a hydrometer) reveals the battery down to 1/4 charge on each cell.

What gives? I ride with my light on day and night and average 30 miles 5 days a week. Could the headlight be pulling the charging voltage down enough that the battery will require frequent charging? Am I not charging the battery correctly by using a 2amp charger on a 14 amp/hour battery?

You are doing things right.
Now it's time to illiminate the possibilities one by one. Here's a few:

It's possible you have something draining the battery while it's parked.

It's possible you have one faulty leg on the alternator, or one faulty leg on the reg/rec.

It's possible there is a load on the system somewhere that is drawing down the system. (This one is less likely unless it is intermittent.)

It's possible the magnet on the alternator is weak.


First step is to make sure there isn't a constant drain on the system. Disconnect the battery at the positive terminal. Touch a small 12v bulb (like a gauge light bulb or even an LED) to the battery terminal and the battery cable to see if it lights up. If there is significant current, the LED might blow up so wear glasses. Or you can use an ammeter if you have one on your multimeter. Anything more than 1 or 2 milli-amps is too much.

Post edited by: loudhvx, at: 2006/02/25 00:42