I find it difficult to believe that a stator gone bad would result in excessive voltage. The stator is just 3 pairs of coils which generate voltage when the magnetic poles of the rotor pass close by them. The amount of voltage is a product of how powerful the magnetic field is, how close the magnets are to the coils, how fast they pass by the coils and how many turns are in the coils.
In order to get a higher voltage from the stator windings at least one of the following would have to be true:
-someone has added turns to the stator windings (highly unlikely)
-the magnets in the rotor have become stronger than when they were new (highly unlikely)
-the clearance between the rotor and stator coils has decreased (highly unlikely)
-engine rpm is way higher than normal causing the magnets to pass by the coils faster (not likely)
Stators can fail: coil windings can short out due to vibrations--this reduces the output voltage. Rotors can detiorate: the magnets can lose some strength--this reduces the output voltage.
My guess is that you don't have a stator problem, so here's how I would proceed.
Undo all connections to the battery and measure your battery voltage--a good battery should be 12.6 volts or so, but not below 12.0
I am going to assume that CA wire colors are the same as the CB schematic so there should be a brown, a pink and a yellow coming from your stator. Verify that the pink goes up to your headlight switch and that one branch of the yellow also goes to the headlight switch. The brown wire should go to one of the rectifier AC terminals.
The other branch of the stator yellow should go to the other rectifier AC terminal. The + positive rectifier terminal is for the red battery wire. The - negative rectifier terminal goes to a good, clean chassis ground connection. Also check that you have a good, clean chassis ground connection from the negative battery cable to the chassis and from the engine block to the chassis.
I'm thinking you have a wiring problem somewhere but I'll leave my speculation until later.
Wilf
Over voltageGreat info, Wilf. All that I remembered about generators but was not 100% sure enough to mention here was confirmed by your message.
I'm sure that I've read here that voltage on these charging systems gets quite high. I swear I remember somebody that monitored their system thru the RPM range, with and without the lights on and they reported voltages much higher than 12vdc. But that does not mean power is high and I suspect the current is only has high as it needs to be based on the load. So that would mean that the battery would not be over-charged. So, what you are saying is something else is drawing down his battery and it is not related to charging voltage. I would tend to agree. I just went back and read the decription of the problem again. At first I thought there might be a problem with the starter circuit, like a high resistance connection causing insufficient power to the starter motor. And that still could be the case. Could be a loose connection, bad terminal, etc. Other thought is something bad internal to the motor itself. This is supposed to be a newly electrical system minus the parts mentioned by the owner so I would rule out corroded connections. He said that the first time this problem arose the bike quit running. That would indicate no charging current and it was running off the battery as a total loss system. I cannot explain the high charging voltage, but maybe the charging voltage is not getting to the battery. I know, seems like a stretch, but things are just not adding up here. Any chance the polarity is reversed and the charging system is connected backwards wrt the battery? I'm going to ignore the 15v for now. A short in the system, could be dragging down the battery. I suggest the following. First, with the ignition off, disconnect negative terminal of the battery and connect your DMM set to read max amps and put in series between the neg terminal and ground. You should read zero current with the ign. off. If you see any current, you have something drawing down your battery when the bike is shut off. Once you are sure you have nothing drawing down your battery, set your meter to DC volts and clip to the battery terminals. Should read battery voltage, same as with battery completely disconnected from the system. Note that you have your meter connected properly wrt polarity, red lead to + and black/common to -. Now turn on the ignition (no lights) and just note if the voltage drops. Now kick start the bike and watch the voltage on the DMM. It should go up with the engine running. Might just barely go up or might be near zero change at idle. Rev engine and it should go up. If all those things happen, shut off the bike. Disconnect the neg terminal from the battery. This is for safety. Now, remove the power lead going to the starter motor. I suggest you do it at the starter solenoid so you don't have a hot lead dangling that could short. With the starter motor not connected, reconnect the battery, turn on the ign, put your DMM across the battery again measuring DC volts and press the starter button. Starter solenoid should click and you should see a minor drop in voltage. If you see a major drop in voltage, you have something wrong in that circuit that is dragging down your battery. Another test is to take a test lead of proper wire size and run a jumper directly from the battery to the pos terminal of the starter motor. If it spins fine and cranks the engine without dying, then it is telling you that the battery and starter are good and there is something wrong in the starter circuit. Could be bad contacts in the solenoid. If the starter has trouble cranking the engine, try another known good battery. A car battery would be fine. If starter motor still struggles, you have a starter motor problem. Following Wilf's points, I suggest you ring out all the wires and make sure everything is connected properly. That's probably the first thing you should do. regards, Rob Hi Rob,
With our AC generators the no-load output voltage can indeed get quite high. That's why these bikes will blow bulbs if the battery will not accept a charge or if it is taken out of the circuit. The stator coils have some resistance and with no load, there is no voltage drop across the coil resistance so the full output voltage shows up at the rectifier. As soon as current flows (charging the battery, supplying ignition etc.), the resistance of the coils results in a voltage drop across the coils and therefore a reduced voltage at the rectifier. The trick is to balance the loads to the generator output so as to neither over or undercharge the battery. The 15 V dc measured at the battery terminals is too high a charging voltage for a 12.6 v battery. Usually it would be a volt or so more than the nominal battery voltage, so 13.6 would be about right. 15 V suggests that the battery is not charging (not drawing a heavy enough current load), so I would be looking for resistance sources between the battery and the stator wires. These could be poor grounds, poor connectors, nicked or broken or corroded wiring, high forward resistance in the rectifier etc. I made some measurements on my CB77 over a range of rpm's and lighting demands but I'll have to look in my journal to find them. Wilf Rob,
I think I found the post you were reminded of: Say What? Too much charging? by Goodysnap, Jun 18, 2010 in Electrical-Wiring In his case of high charging voltage, his light switch was 'on' but his filament had blown. This added the outputs of the second and third pairs of stator coils to the rectifier, but because the filament was gone, there was no matching load added to keep the system balanced. My measurements are in a reply somewhere in that thread. Wilf I'm trying to absorb what you are saying, Wilf. Because it sounds conflicting.
You are saying that if there is a high resistance between the battery and the wiring from the stator/rectifier, then this will reduce the current flow into the battery and hence not charge the battery. That makes sense. For a given RPM, we have a given output in power (watts or volts x amps) which is fixed by the speed, strength of the magnets and number of windings in the stator. If we increase the resistance in the circuit, the power will remain the same. But Ohm's law, E=IxR says that if the resistance goes up, either the current must go down or the voltage must go up. Since the power (watts) is fixed by the conditions mentioned above and the current is now shared between the resistance in the circuit (bad resistance) and the resistance in the battery (good resistance) then current to the battery is reduced by the bad resistance and the voltage is driven up at the battery. Is this correct? I hope this discussion is helping HSF (I keep thinking his name is Flynn and not Flyin'. And I have to admit that I think High Sky Flynn has a nice ring to it) with his problem. It has enlighten me a bit more about the charging circuit and function (assuming I've understood you correctly). So, my suggestion of putting a zener in the circuit would buy him nothing here, would it. Battery would still continue to not charge. It's not over-voltage, it's under current, correct? regards, Rob Rob,
He's a pilot, so I'm betting on 'flyin' as opposed to 'Flynn'. Zener diode regulation is not efficient in this application--too much power lost in heat dissipation. If all the wiring and components are good, the system works reasonably well as designed. Stepping aside from all the theory, it appears to me that there is too high a charging voltage and also a problem with the battery not having enough jam to run the starter. With no additional info from our pilot, there's not much more to go on. I'm pretty sure the stator is not the problem though. Wilf
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
