Battery or alternator? UPDATE

[Mike in AR]

Went out for a ride to on my '97 Bumble bee today. Had gone about 20 miles and decided to pull over to shuck some the layers that I had on. Got back on the bike, and it wouldn't start. Had the wife bring me some jumper cables, and it started right up. While sitting there, I reached over and rev'd the engine, while the wife watched the headlight. It did not get brighter when rev'd. So, my question is, do I need a battery, or is my alternator shot and not charging the battery up? The battery is about a year old. I am guessing that the alternator is 21 years old. The bike has 67,145 miles on it, of which I have put about 50,000 miles of that.                                    
     Also, is there a way to check the alternator while it on the bike, keeping i mind that I know little to nothing about electrical stuff.  

[sandy]

Put a brief charge on the battery and get a voltmeter (12.1 approx.). Check the voltage with the engine off. Start the bike and recheck it as you slowly run the RPMs up (14.1 Approx). If not 14V then the alternator is bad.

[Mike in AR]

Thanks Sandy. I checked the battery without the engine running, and it was 12.16-12.18, so I'm guessing it is good. I checked it with the engine running and it was 14.18-14.22 (it was fluctuating). Does that mean the alternator is good also? If yes, then maybe I just need to charge the battery for awhile on a trickle charge.

[gordonv]

I checked it with the engine running and it was 14.18-14.22 (it was fluctuating). Does that mean the alternator is good also? If yes, then maybe I just need to charge the battery for awhile on a trickle charge.

Yes. You have a fully charging alternator, giving power to the battery. Nothing wrong there.

I checked the battery without the engine running, and it was 12.16-12.18, so I'm guessing it is good.

You have voltage showing on the battery that on the surface shows good. But I suspect that there is no Amps left in there. You'll need to pull the battery and take it to a shop that can test it, to be sure.

You say it's new, can you take it back to the supplier?

There is some write ups about the proper method for charging a new battery.

[Mike in AR]

Thanks gordonv. I will pull the battery in the next day or two and have it tested. It is a year old, give or take, but this past year I did not ride it much. I would start it every 3-4 weeks and let it warm up, but just didn't get out on it much. I think I put around 1000 miles on it over the course of the year. My wife prefers the 2000 Valk trike, so that is what we road the most.

 I will get back to this post to let you know what I find out.  Again, thank you.

[LB]

Mike, 12.6 volts is 100% charged.  12.4 = 75% , 12.2 = 50%, and 12.0 = 25%. Below 12 the battery is dead.  After fully charged, if there is any droppage in voltage after 24 hours, the battery needs replacement. This is at 80 degree temps, and subtract .01 volts per 10 degrees. If you have access to a load tester, anything below 9.6 volts under load is a bad battery. Also keep in mind that a bad battery will come up to charge, but it won't hold the charge.

[Mike in AR]

Thank you LB, I did not know that about the battery. I will put the battery on the charger and then see what voltage is after it is charged. I am probably going to pull the battery in the next day or two and take to the shop to have it checked out. I will post my results when I have some answers.
 
         Thanks, Mike

[da prez]

  Mike , do the basics also. Remove and clean the connections, all of them. This includes the grounds. I use silicone dia electric compound on them. I wire brush or sand them. I have seen many batteries and alternators sold that that were good. When the new one was installed , the connection made contact. As our bikes get older , corrosion grows in the connections. Dis similar metals form oxidation. When current passes thru , they heat up , then cool . This causes connection failure. Yes , the alternator or battery may have failed , but these maintenance steps are needed. 

                                  da prez

[Gryphon Rider]

After the battery is fully charged, disconnect the charger and wait a couple of hours before reading the voltage.  This allows the "surface charge" to dissipate so you get a true reading.

"Full charge" voltage of a battery also depends on battery temperature.  The stock, sealed battery in our Valkyries is an AGM type, so look at the last 5 columns on this table:



BTW, the over 14V reading you are getting with the engine running indicates a working alternator.

[Steel cowboy]

Check your starter switch too. have you taken it apart and cleaned the contacts. If all else looks good, check the kick stand switch too.

[Mike in AR]

Finally had time to pull the battery and have it tested. It is bad. Will have to wait until Wednesday to get a replacement. Thanks to all of you for the suggestions and advice. I have saved this post to my favorites so that I have all the good info you guys have given where I can find it.

   Installed the new battery and went for a short ride (about 85 miles). No problems. Ran like a top. Thanks to all for the replies and suggestions. Special thanks to

Gryphon Rider for the battery temp table. Got that saved so I can find it again.