Battery - or charging circuit?

OK guys, so this is my first XS, but not my first rodeo. But I have been lucky I guess, my electrical has always just worked fine.

This bike is different. I haven't had the time to clean connections etc... I work 80 hours a week so I kind of rely on help from you guys to help cut out the basic stuff.

Anyway, when I got the bike it had about 10% fluid in the battery. Wasn't holding a charge over 9 volts.

I topped off with distilled water. It is holding steady @ 12.48v roughly.
Now I know when running it should hit around 14.5v. It really does not go over 13.5v.

What I want to know is, is this battery more than likely, or can it be my alternator or regulator? I don't know enough about this type of system and am learning now that I sort of have to.

What I am think is that it's not necessarily the battery - because if it's holding 12.5v, then it should be ok?
Is my alternator NOT putting out enough?
Is the regulator cutting it off too early? (is this even possible? If the regulator goes back, I would assume it just lets full power loose, not limit it more?)

Could it be a combo of both? I really don't want to drop $50 on a battery, just to find out the one I have is OK and it was my alternator crapping out.

I don't really use the electric start, I love to kick it. So could I buy a $20 walmart battery just to hold the charge and test the rest? Or do I have to have a big battery like designed?

The manual is so confusing to read when you don't know the basics of how the wiring works etc... hell I don't even know points yet. I am going to google some basics, not sure where to start. Don't even know what TCI is. lol.

Thanks for any help guys, I can work on computer building, household wiring or car wiring, but this whole system is new to me.

PS - if I fire up the motor, and kill it w/ the kill switch... leaving the charger cables connected, I should have functioning EVERYTHING, including brake light, horn, blinkers, dash lights etc correct?

dpawl31,

Do one of two things:

1. Take the battery to a shop that can load test it.
2. Charge the battery overnight.
3. Disconnect charger.
4. Wait a couple of hours.
5. Measure battery voltage. Should be 12.6 or 12.7 volts.

If the battery fails either of these tests, it is probably toast. Sometimes a bad battery will draw more current when charging, so you will read a lower voltage on the battery when the engine is ruining and charging.

But, in any event:

1. Remove the brushes and the brush holder.
2. Measure the resistance of the copper slip rings on the rotor. Should be 5 Ohms.
3. Check the length of your brushes. Should be at least 3/8". (The book says 1/4, but that's not good enough)
4. Use a piece of very fine sand paper wrapped around the eraser of a pencil
5. Start the engine and use the pencil / sandpaper to clean the copper slip rings on the rotor.
6. Reinstall the brushes. Use new brushes if test #3 fails.
7. Check the battery voltage at 2500 RPM after the battery has had some time to recover its charge.

Thanks Pete, when I get time I will probably check and clean the brushes first.
I have a battery monitor/temp gauge that I am installing soon, that will help me monitor as I ride to see how it's working.

So can I rule out my regulator? That should be fine right?

dpawl31,

Aaahh....life should be so simple....

When the regulator fails, generally, you will experience either a very low battery voltage or a very high battery voltage. 13.5 seems to say that the regulator is trying.

When a diode shorts out in the rectifier, the battery voltage may go as high as 12.5 volts, or just enough to get you home, so 13.5 seems to be saying that your rectifier is OK.

But, the real reason I am suggesting having a look at the brushes and the rotor slip rings is because those are the two most common sources of failure and they are the starting point for your charging system troubleshooting.

Good luck....

Well without checking the alternator etc yet... I added my dash mounted battery monitor.

Running 12.5v off, 13.5 ish @ idle, 14.2 over 2k rpm... sounding better now?
Probably still need a battery?

dpawl31,

That sounds like you do not have a problem. If the battery voltage is 12.6 in the morning, without the trickle charge overnight, then it is OK as well. Do you use the electric starter? If so, then that is a pretty good load test. If it cranks over fast and starts right up, then the battery is probably OK.

You can get a few years out of a battery if it is maintained right, but yours sounds like it has been abused. But, the real killer of batteries is overcharging rather than undercharging because the overcharging current heats up the battery and warps the plates.

So, I would keep my eye open for a battery on sale, but keep riding while you're lookin!

Well it's not 12.6, it's 12.0 to 12.5.
If I try and use the starter, it does crank, and cranks for a while... but won't fire unless hooked to the charger because the starter is sucking all the juice from the coils.

On the ride home tonight, I kept the battery monitor going. Never went below 13.2 while idling, most of the time was 13.6. Anytime over 2k it stayed put right @ 14.2v.

The battery has to be toast, the starter drains it very fast. But it seems I can ride the way it is, just not use the starter. Once I have time to go through all the connections, I'll know whether the blinkers and such work. But as for now, it looks like the alternator is putting out well, and the regulator is ok.

Thanks for the help pete!

dpawl31,

Well, that puts a different light on the subject. If you are cranking but not starting, then that's going to fry the starter motor. If the battery is not holding a charge, then that puts a strain on the rotor, which will fry before its time, so now I would recommend that you invest in a new battery because it's going to cost a lot more if you don't.

I knew the starter would fry, hence I don't use it

But, didn't know about the rotor strain...

Can I buy a 12v battery from walmart? I don't plan on using the electric, I love the kick... so can I but a much smaller battery? Like a 4" or so lawnmower battery? I think they are like $20

I have had Walmart batteries before and they do ok. I have one in my Harley now, about two years, no trouble. The 650 battery is from the tractor supply. They had a big opening sale. got a better battery at Walmart price.
If you don't abuse them they are ok.

The lawn mower batteries are physically bigger than the stock battery. And Don't think they can hold up to the vibration.