Does anyone know what the voltage should be across the battery terminals when the bike is started and the terminals are disconnected from the battery? I'm only getting 5 volts.

The battery was low Friday after a 60 mile round trip commute to work on the highway.

When the bike is started and I disconnect the terminals from the battery, the headlight gets real dim until I replace the terminal to the battery.

I'm thinkung that the battery isn't charging properly and it's slowly draining as I ride instead of charging. Thanks.

M

 

Do you mean the battery terminals or the wires?

Be careful, you may damage the regulator.
It doesn't surprise me that the voltage is low when the battery is out of the loop. Especially at very low rpm.

Measure the voltage across the battery with it connected and the rpm over 3000 maybe 4000.
Should be up around 14.5v.
A battery in good condition on it's own should be around 13.2v.

 

Neil

I removed the positive leg from the battery after the bike was started and measured the five volts on the disconected wire. I threw the battery on a charger when it was low and it charged ok so I know the battery is good. It's less than a year old.

I'm really wondering why the battery was so low in the first place. It's been cold and I haven't used the bike much this winter.I thought the bike produced its own 12 volts without the battery when it was running.

If the lights need help from the battery to illuminate them while the bike is running, then it would seem to me that the battery is gonna slowly discharge while in operation instead of recharging. I'd really hate to get stranded tonight on my way home from work.

Mike

 

Check the big three wire connector beside the battery, and check the ground connection at the ignition coil. I had the ground connection leave me stranded once, the battery voltage was almost normal 12.5-13v at idle, but any thing above 2K RPMs and the voltage fell to around 12v.

 

neilaction is correct on this advice. Every automotive instruction manual will state "Never disconnect the battery from a running motor". I can't remember the reason for that statement, but I think you got lucky that you didn't ruin the voltage regulator! These same manuals state that a fully charged lead-acid battery will show a voltage of 12.62 volts (some state 12.65 volts) Obviously one must be using a digital voltmeter to get these accurate readings!

 

Wonderful... I won't be doing that again. I checked the battery before I left for work this afternoon and it was at 13v. After a 30 minute commute in a mostly 65mph zone I was still just above 13v on the battery.

I'll check it again after the trip home tonight. I use the nite-glow LED's at night so maybe that's part of the problem. LED's draw very little power so I dunno. Thanks for the input guys.

Mike

 

You can run most bikes without the battery.
But, you will need to put a large capacitor in it's place.
Otherwise the pulses from alternator may cause issues.

I don't know about the KLX specifically in that what the regulator/alternator output voltage is at low RPM.
If its too low then the lights etc may not run bright enough.

The other thing is with a normal incandecent bulb the attack and decay time of the filament will cause it to glow a dull orange at low RPM without a battery. And pulse as well.

A lead acid battery in good condition will produce 2.2v per cell or 13.2v.
The charging system will produce around 14.5v +/- a bit at the designated RPM.
This voltage difference is what charges the battery.

 

Update:

Got the bike home tonight after work with the full LED illumination all the way back. I mostly took the side roads home with some 55mph zones mixed in, and everything was 'Kool and the Gang". The battery registered 13.36 volts when I measured it immediately after pulling into my garage. Which was an improvement from the 13.1* I measured before leaving my office. Which shows that the charging system is working and that the battery is fully charged after the ride.

Not sure what happened to drain the battery in the first place but whatever it was has my full attention.

I park the KLX in my office, so I brought a battery tender and stowed a volt meter in the fender bag to be safe. Very easy to charge the battery when an A/C outlet is a few feet away from the parked bike.

Neil-
I'd love to know what the 'alternator' output is for the KLX at low rpm's. I would hope that even at idle it could still power up the lights and an accessory. I was really trepidatious on the ride home. Luckily it worked out. Thanks for the input.

M

 

.
It's the output after the regulator thats important.

If this voltage is higher than the batteries voltage, its charging.
It would be borderline at idle.
The way to measure it is with the battery connected.

Connect the meter across the battery and the rpm point at which the voltage across the battery exceeds the voltage across the battery with the engine off is the point you get the battery charging.

There will be minor inaccuracies due mainly to what the meter is reading.
The meter will not respond to brief pulses that will be a factor in reality. It's measuring average over a sample time. Or if its an analogue meter, the needle dampening will be what is holding the needle steady.
The batteries capacitive effect will iron out all the bumps and thats why it can be dangerous to run it without the battery without putting a capacitor in its place.

I did that with my DR350.
As it was a kick start only bike, the battery was of no real use to me.
So I removed it and put a capacitor in it's place to reduce weight.
The lights would not run properly at low RPM without some sort of smothing device and also I may have risked damage to the CDI at higher rpm's.
In saying that modern regs are pretty good.

DC needs to be like a good malt wiskey, Nice and smooth.