Battery issue

Ok, I know these are notorious for the R/R failing and i searched for a similar situation and didnt quite see a cut and dry way to determine. To me, it seems simple. My battery reads a solid 12 volts while running but the bike will not start. If i bump start the bike i can ride it for however long id like...Seems like my bikes charging but the battery is bad? I only pose the question because of the R/R problems ive heard so much about. I'm not 100% sure what the bike should be charging at while running either, so i figured id post up. So whats the deal, just a bad battery, or am i wrong? Thanks in advance.
-Daver

 

Well, to be honest I haven't looked much at the R/R problem so I'm not real helpful in that respect.

In general the alternator puts out excessive current and voltage when it's turning. As RPM increases both voltage and current output from the alternator increase. The alternator is generating an AC voltage so the rectifier converts the AC to DC. Next, the regulator limits the voltage to 13.8 volts maximum which is what you should see at the battery when everything is charging correctly. The excess over what is required to run the engine and electrics (ECU, lights, gauges, etc.) is used to keep the battery charged.

Keep in mind that CURRENT and VOLTAGE are completely different. You can show 13.8 volts at the battery during charging but it can be at such a low current flow that there isn't enough to top off the battery, or in severe cases even provide enough to keep the electronics on the bike running.

My recommendation would be to charge the battery with an off-the-bike charger. If it will not hold a charge then you have a bad battery. You can also take it somewhere and have it "Load Tested" to see if it will provide the rated current flow under load conditions (i.e. what you would see starting the bike).

Sorry I can't be more help. I understand electricity and electronics, I just don't know what the symptoms of this exact problem are.

 

Seems as though I should be seeing 13.8 volts when charging then, and I'm not...I should have mentioned i load tested the battery and it showed weak, but that still doesn't explain why when the bike is running I'm not seeing the ~14 volts charging....hhrrmmm.

 

Bumpity bump b4 i head to bed...any insight guys?

 

S14Daver:

I have a feeling its your RR.

Do you have a multimeter?

BZ

 

Yes, using the multimeter i found that
A) The battery is dead as a door nail on it own
B) While running it reads 12v, not the ~14 it should

This led me to believe that its just a really dead battery, since i can bumpstart it and ride it and that it seems to be "trying" to charge it.

This is why im consulting you experts though, is this signs of a bad R/R resulting in my dead battery and I need both?!? I'm thinking just battery, but you guys are saying R/R??

Thanks for the help, and let me know if you want to me to check anything else with the meter.

 

Well, buy just the battery, install it and take your readings then.

If its less than 13.8 volts, you'll know its the RR too.

If this is the case remove the new battery immediately! Order a new RR and only put the battery in with the new RR installed.

BZ

 

That's my plan! Thanks for the info though guys.

 

With a fully charged battery, depending on how you keep the revs, how much you brake and how much you indicate, you can run on a fully charged battery, that is no longer charging for about 90 minutes, before they battery wont have enough charge to start the bike or run the electrics.

I have found that anything reading less that 12v wont start the bike. If the bike is running, and you are only getting 12v, then its most likely your R/R.

In this case, it could be either, so change the battery anyway. However I think you will find it is still your r/r. so best to change them both anyway.

90% of the time, it is an R/R, so for $120, its an easy and quick fix.

 

Dont replace the R/R without replaceing the battery first (because of weak load test) and then take your voltage reading at idle and at a higher RPM the charging point may be above idle some bikes charge as high as 3000 RPMs. If you have a service manual it should tell you how to test the R/R with your multimeter. It is not hard and checking thing first is better than spending money.

Trust me do these test

GOOD LUCK.

 

^thats the plan, due to the weak load test i want to try just a battery for a second and see what shes charging at...hopefully i can get around to it after class tomorrow.

 

UPDATE
Replaced cheap dead battery with a good replacement...still reads around 13v...took it for a ride came back and the battery read 12.1ish. Consensus, its not charging the battery...is this definitely a R/R problem? And if so wheres the best place/price to get one? Thanks again for the ongoing help with the diagnosis. It's probably cut and dry to you guys, but i want to make sure before i go buying the part. I knew the battery was toast and would need one anyways, but want to make sure i need a R/R...

 

I'd say "yes"

Classic RR symptoms.

BZ

 

Thanks Mello, allow me to be lazy and ask where is it located? I haven't bothered to look and the manual is in my garage and that 50ft is just too far lol.

 

Thanks Mello, and I'm definitely up for a ride come spring!