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Old 12-08-2012, 12:17 PM   #1
PBOB OP
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Very confused: 82 cb900c charging problem

I got a cb900c a couple months ago. Wasn't charging battery. Did voltage test on system. Undercharging. Rotor was not within spec. Got it rebuilt, bought Electrosport rectifier and stator. Installed it all and was charging at 14v. Rode it for 500-750 miles over next couple months. Hooked GPS unit up to cigarette lighter on vetter fairing for 20 min. Worked fine no adverse reaction. Unhooked it and didn't use it since. Also, battery is recently new, sealed type.
Last night went to start it and it slowly drained battery while idling and finally died.
Rechecked rotor rings, good, 4.9 ohms. Checked continuity on stator wires, good. Check rectifier, mixed ohms readings but they appeared to register in the flow indicated in manual. Meaning, there was continuity in one direction then switched wires, continuity in the other direction.....
So, now I'm royally confused. There no point in just buying more parts. What should I do next?
How do I track down this gremlin? I looked at Electrosport finding fault guide... But did not complete all test. Still there has to be someone out there who can point me in the right direction...
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1982 Honda CB900c
2002 Kawasaki KL250G "Super Sherpa"
1999 Honda CN250 Helix
1995 Honda XR650L (in Shasta white and Uranus violet of course)
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Old 12-08-2012, 12:21 PM   #2
Boon Booni
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Quote:
Originally Posted by PBOB View Post
I got a cb900c a couple months ago. Wasn't charging battery. Did voltage test on system. Undercharging. Rotor was not within spec. Got it rebuilt, bought Electrosport rectifier and stator. Installed it all and was charging at 14v. Rode it for 500-750 miles over next couple months. Hooked GPS unit up to cigarette lighter on vetter fairing for 20 min. Worked fine no adverse reaction. Unhooked it and didn't use it since. Also, battery is recently new, sealed type.
Last night went to start it and it slowly drained battery while idling and finally died.
Rechecked rotor rings, good, 4.9 ohms. Checked continuity on stator wires, good. Check rectifier, mixed ohms readings but they appeared to register in the flow indicated in manual. Meaning, there was continuity in one direction then switched wires, continuity in the other direction.....
So, now I'm royally confused. There no point in just buying more parts. What should I do next?
How do I track down this gremlin? I looked at Electrosport finding fault guide... But did not complete all test. Still there has to be someone out there who can point me in the right direction...
How long did you let it idle? Many bikes are barely breaking even at idle.
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Old 12-08-2012, 12:55 PM   #3
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Idle and revving it. 10 min. Still at 1700rpm it should have read 13.5v. It was at 11v. After I put new hardware on, it charged at 13.5-14.5v at 1700rpm.
My only guess is the rebuilt rotor has already failed. Like maybe there is a flat spot or short in just one part of face plate were rings are at. It measured 4.9. But when I tested a coule diff locations around the rings, reads would fall or jump all over the place...
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1982 Honda CB900c
2002 Kawasaki KL250G "Super Sherpa"
1999 Honda CN250 Helix
1995 Honda XR650L (in Shasta white and Uranus violet of course)
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Old 12-10-2012, 06:38 PM   #4
hardwaregrrl
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I'd do a load test on the battery. Faulty alt/rotors can sometimes harm the battery.
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Old 12-11-2012, 12:56 PM   #5
Kai Ju
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Are you checking slip ring resistance through the brushes or directly against the slip ring ?
If you're getting the different readings through the brushes, are they in spec length wise ?
Also, what does it do when you full field the Regulator ?
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Old 12-23-2012, 08:42 PM   #6
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Are you checking slip ring resistance through the brushes or directly against the slip ring ?
If you're getting the different readings through the brushes, are they in spec length wise ?
Also, what does it do when you full field the Regulator ?


i tested brushes when i bought new charging system components, length was well beyond scrib mark.... brushes are the only not new things. also, to verify my recently new battery was not at fault, i took the battery out of my other cb900c (the blue one, that currently has no issues) and hooked it to the at fault cb900c (red one). i got same low output readings as before. stator wires give good 0.9ohm reading. rotor gives 4.9-5 ohm reading. rectifier is new....to help everyone get idea of the trouble im having here are my recorded test below: (note- the red cb900c 17,000 miles, has vetter fairing and bags, maybe it was wired poorly causing my low reading and frying system; the blue cb900c is bone stock 34,000 miles and charges right)------manual says bike begins charging at 1700rpm

-1st test on red honda output (the one at fault) with fully charged battery
1000-1200 rpm idle: 12-12.05
1400rpm: 12-12.3v
2000rpm: 12.6-12.8
3000rpm-3500rpm: 14.4-14.5
4000rpm: 14.4-14.5

a couple days later, i test red cb900c again, with worse results on fully charged battery
1000rpm idle: 11.9-12v slowly falling
2000rpm: 12.1-12.3v
3000rpm: 12.-13v
4000rpm: 13v

so i though it was a bad battery, so i swapped above mentioned battery from other bike, same results on voltmeter...

so i decided to test my properly charging blue cb900c:
1000rpm: 12.9v slow drop to 12.3 and holds there after 3minutes
1300rpm: 13.9-14.1v
1500: 14.2-14.3v
2000rpm:14.5-14.6v
3000-3500rpm: 14.3-14.6

if you look at the bule bike results- it maintains a slight bump off 12v on a weak 1000rpm. as soon as i give it gas, it starts dumping current into battery.

here is what im guessing, suggestions welcome...
a. my carbon brushes are bad or not good. they are plenty long enough past scrib line, may i put them in wrong places?
b. my rebuilt rotor has already failed maybe. a short somewhere? (still test ok, 4.9ohms. but when i move ohm meter around slip rings, readings change and jump all over every couple of trys on different spots on slip rings, reason to worry? may just be tester)
c. magnetic charge from rotor isnt sufficient
d. my aftermarket vetter wiring throughout bike is sucking my voltge. a PO did this at some piont, not me...
e. my new rectifier is dumping too much voltage (i even swaped in my old rectifier for a minute or 2, same crappy results)
d. the 20 mins i hooked up my gps to the cig lighter, it fried my system or something. (but i had a 3amp inline fuse on other side of gps in case it pulled too much or something was amiss...

please help. your suggestions are welcome and your input valued....
__________________
1982 Honda CB900c
2002 Kawasaki KL250G "Super Sherpa"
1999 Honda CN250 Helix
1995 Honda XR650L (in Shasta white and Uranus violet of course)
The list is long, I'll stop there....
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Old 12-23-2012, 09:09 PM   #7
retiredgentleman
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A simple test is to measure the current flow in the rotor. You would need to connect your VOM in series with one of the wires that go to the brushes. Select the meter to read amps on the 10 amp scale. Start the engine, and with the engine idling, you should read around 2 amps of current flow. That is the current required to produce a strong magnetic field. If you do get 2 amps, rev the engine to 3000 rpm and the current should drop back to around 1 amp.
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Old 01-11-2013, 08:59 PM   #8
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Originally Posted by retiredgentleman View Post
A simple test is to measure the current flow in the rotor. You would need to connect your VOM in series with one of the wires that go to the brushes. Select the meter to read amps on the 10 amp scale. Start the engine, and with the engine idling, you should read around 2 amps of current flow. That is the current required to produce a strong magnetic field. If you do get 2 amps, rev the engine to 3000 rpm and the current should drop back to around 1 amp.

well i'm not sure exactly what you are asking me to do... but i did recieve my 2nd rebuilt rotor today from tim parrot.
to remind you, all components are new, except brushes which are well past scribe.... anyway so i retested the entire system. all individual items check good- stator yellow wire read 0.9ohms. rotor reads 5ohms.
next....
i started bike and tested DC volts at battery terminals: 12v barely.
bumped up rpm to 2000: 12.2-12.5v
a 3000rpm: 13v slow climb to 13.8v (manual says at 3000rpm DC volts should read 14-15v)

then with stator wires still hooked up and bike at idle (12-1500rpm)- i put tester to the yellow wires of the stator as manual describes: all read 9.5-10 volt AC. (manual specs 8-10v AC). so that was in specs.It appears my stator and rotor are generating power.

Its like my regulator is dumping to much current maybe?
I just cant see how 10v AC converts to 12-15v DC. Can anyone explain?
does anyone have any additional suggestions?
tomrw i will get a new battery ground wire- just in case i cant see some corrosion behind insulation. and i will try to get auto store to trade a new battery for the one i bought 2-3 months ago from them....
__________________
1982 Honda CB900c
2002 Kawasaki KL250G "Super Sherpa"
1999 Honda CN250 Helix
1995 Honda XR650L (in Shasta white and Uranus violet of course)
The list is long, I'll stop there....
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Old 01-12-2013, 01:29 PM   #9
retiredgentleman
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Originally Posted by PBOB View Post
well i'm not sure exactly what you are asking me to do... but i did recieve my 2nd rebuilt rotor today from tim parrot.
to remind you, all components are new, except brushes which are well past scribe.... anyway so i retested the entire system. all individual items check good- stator yellow wire read 0.9ohms. rotor reads 5ohms.
next....
i started bike and tested DC volts at battery terminals: 12v barely.
bumped up rpm to 2000: 12.2-12.5v
a 3000rpm: 13v slow climb to 13.8v (manual says at 3000rpm DC volts should read 14-15v)

then with stator wires still hooked up and bike at idle (12-1500rpm)- i put tester to the yellow wires of the stator as manual describes: all read 9.5-10 volt AC. (manual specs 8-10v AC). so that was in specs.It appears my stator and rotor are generating power.

Its like my regulator is dumping to much current maybe?
I just cant see how 10v AC converts to 12-15v DC. Can anyone explain?
does anyone have any additional suggestions?


.
tomrw i will get a new battery ground wire- just in case i cant see some corrosion behind insulation. and i will try to get auto store to trade a new battery for the one i bought 2-3 months ago from them....
13.8 volts at 3000 rpm means you are charging, but just not fully charging. To be fully charging the battery you need to read 14.1 volts. Even though the brushes seem to be long enough, might be a good idea to try some new ones.

Your meter measures AC voltage, which is RMS voltage. RMS voltage is 0.707 of peak voltage. To convert the 10 volts RMS to peak voltage, you multiply by 1.414. So 10 volts AC actually converts to 14.14 volts DC after it has been rectified and filtered by the battery (there is small voltage drop through the rectifier, so may only get 13.5 volts, not 14.1 volts) . However, you will only reach the 14.14 volts if the amps coming out of the alternator are enough to match the amps drawn by the loads on the bike.

Just for your information, on my Yamaha 1978 XS650 SE, at 1200 rpm idling, I measure 12.5 volts AC across any 2 phases of the alternator's stator output.

I suggest you remove some of the bikes electrical load. If your bike has 1 or 2 #1157 bulbs in its tail light, they consume a ton of power. Find a replacement LED tail light, as they only use a very small amount of power. Make sure your headlight is not on high beam. Consider changing to a 40 watt head light if you now have a 55 watt head light.
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Old 01-12-2013, 03:06 PM   #10
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Originally Posted by retiredgentleman View Post
13.8 volts at 3000 rpm means you are charging, but just not fully charging. To be fully charging the battery you need to read 14.1 volts. Even though the brushes seem to be long enough, might be a good idea to try some new ones.

Your meter measures AC voltage, which is RMS voltage. RMS voltage is 0.707 of peak voltage. To convert the 10 volts RMS to peak voltage, you multiply by 1.414. So 10 volts AC actually converts to 14.14 volts DC after it has been rectified and filtered by the battery (there is small voltage drop through the rectifier, so may only get 13.5 volts, not 14.1 volts) . However, you will only reach the 14.14 volts if the amps coming out of the alternator are enough to match the amps drawn by the loads on the bike.

Just for your information, on my Yamaha 1978 XS650 SE, at 1200 rpm idling, I measure 12.5 volts AC across any 2 phases of the alternator's stator output.

I suggest you remove some of the bikes electrical load. If your bike has 1 or 2 #1157 bulbs in its tail light, they consume a ton of power. Find a replacement LED tail light, as they only use a very small amount of power. Make sure your headlight is not on high beam. Consider changing to a 40 watt head light if you now have a 55 watt head light.



^note taken on advise above.....
also- today i took the 900 out for a 1hr ride.
i hooked up a digital meter to battery terminals and taped it to gas tank while i rode.
when riding between 3,000-4,000 rpm- it read 13.5 and slowly built up to 14.5ish and stayed while cruising.
when slowing to a stop @ 2000rpm or so- it dropped to 12.8 down to 12.5.
at idle 1500rpm ( i torqued up idle for more rpms when standing still) it read 12.05-12.25
now- here is my delema... i waited 5min and noted terminal surface charge after i shut bike off - it read 12.57.
if i go back and re-check that every day and it drops any amount- should i believe a drain or bad ground could be killing my battery when it sits?
because bike appears to be charging adequately while riding- it could be loosing volttage as it sits too rapidly,...
thx
__________________
1982 Honda CB900c
2002 Kawasaki KL250G "Super Sherpa"
1999 Honda CN250 Helix
1995 Honda XR650L (in Shasta white and Uranus violet of course)
The list is long, I'll stop there....
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Old 01-12-2013, 03:11 PM   #11
photomd
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Sounds like it's OK. Put the amp meter between the battery cable and battery and see if any current is flowing when the bike is off.
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Old 01-13-2013, 01:08 PM   #12
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Sounds like it's OK. Put the amp meter between the battery cable and battery and see if any current is flowing when the bike is off.

i think i am doing what u suggested....
as mentioned, i measured surface charge after i went for ride yesterday- 12.57v
today i checked it after 24hrs- it was at 12.45
sign of drain?...
i will not run it- and check it tomrw and report back....
as suggested in previous post- my bike appears to be charging like it is supposed to.
i think we have narrowed it down to a faulty sealed new battery (3 months old) or a drain or short casing the battery to discharge while sitting---- sound about right?
and so here are my suggestions---
1. i have a drain at the battery bc of an old battery terminal wire- unlikely bc bike is charging properly
2. i have a faulty battery
3. the drain is comming from a working, yet bush-league done wiring set-up for vetter fairing and saddlebags
eh?,,,,
__________________
1982 Honda CB900c
2002 Kawasaki KL250G "Super Sherpa"
1999 Honda CN250 Helix
1995 Honda XR650L (in Shasta white and Uranus violet of course)
The list is long, I'll stop there....
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Old 01-13-2013, 01:22 PM   #13
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There's no need to wait. Go ahead and test it: Put your multimeter on 10 amp setting. Disconnect the neg battery cable. Put one lead of the multimeter on the neg batter lead and the other on the neg battery cable. Does it read anything? If so, you have a drain on the battery. Disconnect stuff or pull fuses until you find what's pulling current. It doesn't sound like a drain to me.

Also, don't worry about the surface charge. Put your voltmeter on the battery and hit the starter button. It'll drop with each rotation. IMHO, if it quickly drops below 10 volts, the battery is on it's way out. I got this from using wet batteries for years. I think test the specific gravity of the electrolyte is the best way to test a battery. When they'd quickly drop below 10 volts, the electrolyte would show a lower specific gravity which would tranlate into about a 50% charge. At that point I could nurse it awhile longer, but was afraid it would leave me stranded on a longer trip.
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Old 01-13-2013, 01:29 PM   #14
retiredgentleman
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Quote:
Originally Posted by PBOB View Post
i think i am doing what u suggested....
as mentioned, i measured surface charge after i went for ride yesterday- 12.57v
today i checked it after 24hrs- it was at 12.45
sign of drain?...
i will not run it- and check it tomrw and report back....
as suggested in previous post- my bike appears to be charging like it is supposed to.
i think we have narrowed it down to a faulty sealed new battery (3 months old) or a drain or short casing the battery to discharge while sitting---- sound about right?
and so here are my suggestions---
1. i have a drain at the battery bc of an old battery terminal wire- unlikely bc bike is charging properly
2. i have a faulty battery
3. the drain is comming from a working, yet bush-league done wiring set-up for vetter fairing and saddlebags
eh?,,,,
12.57 going down to 12.45 volts after 24 hours is quite normal. Yes check for current flow using the amp meter on your VOM.

I have a very poor opinion of sealed (AGM) batteries. A friend of mine had an AGM battery that was only 1 year old. He kept telling me his starter would not crank the engine. I drove over to his place and installed my 7 year old lead acid battery, into his bike (1976 XS650). With my battery, fresh out of my bike (1978 XS650 SE), his bike started right up. His new AGM battery was crap.
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Old 01-13-2013, 02:33 PM   #15
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Originally Posted by photomd View Post
There's no need to wait. Go ahead and test it: Put your multimeter on 10 amp setting. Disconnect the neg battery cable. Put one lead of the multimeter on the neg batter lead and the other on the neg battery cable. Does it read anything? If so, you have a drain on the battery. Disconnect stuff or pull fuses until you find what's pulling current. It doesn't sound like a drain to me.

Also, don't worry about the surface charge. Put your voltmeter on the battery and hit the starter button. It'll drop with each rotation. IMHO, if it quickly drops below 10 volts, the battery is on it's way out. I got this from using wet batteries for years. I think test the specific gravity of the electrolyte is the best way to test a battery. When they'd quickly drop below 10 volts, the electrolyte would show a lower specific gravity which would tranlate into about a 50% charge. At that point I could nurse it awhile longer, but was afraid it would leave me stranded on a longer trip.


like this?????
not sure if im right....




and hooked up like this?????


thx for the help in advance....
__________________
1982 Honda CB900c
2002 Kawasaki KL250G "Super Sherpa"
1999 Honda CN250 Helix
1995 Honda XR650L (in Shasta white and Uranus violet of course)
The list is long, I'll stop there....
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