Topic: Charging system test results...diagnosis help UPDATE

[NCSUEngineer]

So after scouring the forums for information on charging system diagnosis I zipped tied my multimeter to CB500 and went for a ride....

Key off: 12.64V
Key on: 12.61V -> ignition on: 12.4V
Idle (1000ish rpm): 12.36V
1500: 12.36
2000: 12.37
3000: 12.38
4-5000: 12.4V

I validated these numbers by testing it again at a standstill.

After my little 10 minute ride (im scared to take it too far for fear of the battery dying again) everything gets turned off and the voltage slowly starts increasing from 12.4X back up to 12.6X.

I was having battery drain problems on a new battery (that i just recently replaced with ANOTHER new one that i tested on).   So did changing the battery solve my problems or are these numbers abnormal?

[Sporkfly]

Have you tested the resistance on your field coil? They seem a little bit low... I was getting similar voltage reads with low resistance on the field coil. Have you cleaned your clips, fuses and various other contacts?

[NCSUEngineer]

I haven't...where is it located, and what sort of reading should i be looking for? I'll give try cleaning up the connections a shot.

[ofreen]

So after scouring the forums for information on charging system diagnosis I zipped tied my multimeter to CB500 and went for a ride....

Key off: 12.64V
Key on: 12.61V -> ignition on: 12.4V
Idle (1000ish rpm): 12.36V
1500: 12.36
2000: 12.37
3000: 12.38
4-5000: 12.4V

I validated these numbers by testing it again at a standstill.

After my little 10 minute ride (im scared to take it too far for fear of the battery dying again) everything gets turned off and the voltage slowly starts increasing from 12.4X back up to 12.6X.

I was having battery drain problems on a new battery (that i just recently replaced with ANOTHER new one that i tested on).   So did changing the battery solve my problems or are these numbers abnormal?

A good battery fully charged should show 12.8 volts with no load after sitting.  So your battery is not fully charged.  Your tests show no increase in voltage with a rise in RPM.  By 4000-5000 RPM you should be getting at least around 14 volts.  For whatever reasons your charging system is not working.  Cleaning all coonections and plugs is a good place to start.  Do a thorough job cleaning, then repeat your tests.

[NCSUEngineer]

i was under the impression that in a 6 cell wet battery, each cell held 2.1 V, so 12.6 volts was normal.

[Tower]

After analyzing the data in the CB750 service manuals, I plotted the known values, interpolated the remaining values for 250 rpm intervals and extrapolated out to 6000 rpm operation, then charted the results for your viewing pleasure....

[TwoTired]

You have a charging system issue to track down and correct.

Cheers,

[NCSUEngineer]

tower, thanks for the graphs.  I ride a CB500, however, though i can imagine the curves would look similar.

I cleaned some things up and then started blowing the main fuse...only to realize it was a 10amp and not a 15 so thats been replaced.

the multimeter is showing a much great change in voltage when throttle is applied - though the overall voltage is now generally lower - hovering around 12V

[Bodi]

This is probably the most popular thread topic here (next to oil) and you'll find a LOT of stuff if you search a bit.
Basically the situation is that the electrical system has a power demand - the lights, ignition, and alternator field coil. There's also the electrical power supply - the alternator power coils.
Hopefully there's more supply than demand. The original bike when hew presumably worked fine and charged the battery, so what's changed?
1 - Age: the electrical connectors and switch contacts have gotten corroded and most probably have a higher resistance than as new. Nothing else really ages to cause a problem in the electrics. The trouble is that applying Ohms Law of electricity, a higher resistance in a circuit carrying current means a lower voltage at the output of the circuit. This has a lot of effects (stay tuned).
2 - Modifications: Nobody seems to install dimmer, lower power headlights - H4 lamps are popular, and finding a low power bulb to match the factory headlight draw is possible but rarely practiced. Lots of people add marker lights. 3 Ohm (stock is 5 ohm) ignition coils are a fairly popular "hot rod" modification. Adding to the demand when there's little extra supply available - the 350, 400, 500 and 550 are all marginal - will often lead to battery discharge or at least low running voltage and an inability to use the electric start regularly.
3 - Battery. No system will work with an old half-dead battery.
4 - Regulator: These are actually more reliable than most people think and are rarely the problem, but they do fail.
The cure? First, clean all those bullet connectors in the harness, and any multi-conductor connectors (engine plug, rectifier plug, fuseblock plug?). Shoot some contact cleaner into the ignition switch and exercise it a while.
Measure the voltage drop at your regulator with the bike all up and running.

Well. I've been writing this while sausages grill. They're done now. I'll try and get back for more later!

[Logite]

tower, thanks for the graphs.  I ride a CB500, however, though i can imagine the curves would look similar.

I cleaned some things up and then started blowing the main fuse...only to realize it was a 10amp and not a 15 so thats been replaced.

the multimeter is showing a much great change in voltage when throttle is applied - though the overall voltage is now generally lower - hovering around 12V

Firstly you're going to want to check the Rotor's slip rings. Put a multimeter between the smaller ring towards the inside of the rotor as well as the outside ring towards further away from the center. If you don't get a reading, time to replace the rotor. If you do, it should be around 4 ohms or so.

If the rotor is working, check the brushes that contact the slip rings. If they don't feel springy or are too worn you'll want to replace them.

If none of these are off, your best bet would be to check the regulator/rectifier and replace it with a new one.

[NCSUEngineer]

Those things you just mentioned are checked by taking off the alternator cover, right?

[Tower]

The easy and most obvious things first...
1. Check the voltage regulator and adjust as per the manual.
2. Verify the generator coils have the proper impedance.

edit: mmm, Sausages...aghagh!

[TomC]

Hi NCSUEngineer
     If the CB500 is a SOHC Four you will have a lot of trouble finding any of the things Logite mentioned.
     The CB500 SOHC Four does not have slip rings.
          TomC in Ohio
Hi Tower
     The voltage regulator should not be touched until everything else in the charging system is in perfect order.
     Do you have an impedance meter? Do you know what the impedance should be?
          TomC in Ohio

[NCSUEngineer]

Yes its definitely FOUR.  I sometimes forget that they also made a 2 cylinder model and neglect to specify occasionally.

I don't have an impedance meter, only a multimeter capable of measuring voltage, current, and resistance.  Unless by impedance you mean 'resistance'...but i believe they are somewhat different.

[Tower]

From where I stand TomC, if the voltage isn't climbing past 12v, I'd say either the regulator relay arm is making contact with the relay coil(resistor),or the contact points are pitted and adding a large amount of resistance, or the points are not making very poor contact, in any case, reducing the field coil charge below the required amount and hence not charging the battery.  Mostly mechanical device - easy to check and verify with feeler gauge, screwdriver and emery paper - very likely the problem.

Checking generator coils is only slightly more complicated as the yellow leads must be disconnected from the rectifier before testing.  Needs only an ohmmeter (although impedence is not exactly the same as resitance for this test they may as well be the same), and basic skills - also very likely to be the problem.

Edit: Sometime back I recall a thread on rated coil resistance for CB650 vs CB750 generator coils ....now if only I could remember who posted the info   

[bryanj]

Quick and dirty check is to connect a lead from the battery positive to the white wire connected to the regulator ---- DISSCONNECT IT FROM THE REG FIRST

If your battery voltage climbs at anything over 3,000 revs the generator, rectifier and connections between are ok but reg and or connections aint

If battery volts dont climb could be anything

[NCSUEngineer]

UPDATE:

Well heres what ive done so far.


Adjusted the Vreg to within spec -> no change
Shorted the black and white wires together, off the Vreg, and started her up -> no change
Tried testing the rectifer for continuity by testing the resistance through all the yellow connections that lead out of plug - > could not get any readings

Is the field coil checked by removing the bottom most plug and checking the solid green and white wires' (coming from the engine) resistance?

[TwoTired]

Have you checked the electrics FAQ?

Do you have a Honda shop Manual?

Do you have a wire diagram for your bike?

Have you checked the Field coil resistance? 

The rectifier is checked by using a diode test function and measuring both polarities of the green to Red terminals.  Only one way should conduct.  There is a diode connected to each yellow to Green and another from each yellow to Red.  Twelve tests using the diode test function will prove/disprove your rectifier diodes.

Cheers,

[NCSUEngineer]

I've got a manual and the rectifer testing isn't very clear to me.  It only tells me to test continuity... in the 'normal' direction'...continuity in both directions is bad.

I just tested field coil resistance via the electrics FAQ (much better than the manual)...and i got 1.2 Ohms...according to the FAQ the field coil has failed.

Also, under the "testing the regulator wires" i tested the black regulator wire and ground and got 6.4 Ohms..so i assume i have a faulty wiring insulation/connection on that end.

I'll get back with the rectifier results, the FAQ is a little better than  the manual which is pretty vague on that process.

thanks

[TwoTired]

The field coil (White and Green wires) S/B 4.9 Ohms +/- 10% for the Cb500.  Before you condemn the coil, measure again at the connectors nearer the coil proper.

The quick and dirty rectifier test is just with green and red wires.  To find out if any of the diodes have failed open you have to do the twelve tests.

The black regulator wire has all sort of loads on it in the bike connections.  The black regulator terminal is a different story.  Which are you measuring?

With the stock regulator (disconnected) you should have continuity between the Black and White terminals.  These would also be stamped I and F, I think.

Cheers,