Charging at 13.5V

I have a 1983 GR650 twin and I have a bit of a different charging problem. It charges between 12.9v and 13.5v. It charges highest at around 1800RPM and lowest at about 5000RPM. I hooked up my multimeter to the battery and placed it in my tank bag for testing. I suspected a faulty stator but it spec'd out good. It has 1.9 ohms between the three legs and no short to ground. It gives 72VAC, 72VAC, and 75VAC on the three phases on start up. After an hour ride the AC voltage test drops a bit to 63, 65, and 75. Could the weaker battery following the ride account for the lower AC voltage? Oh yeah, the battery is new and gets treated to a Genius charger after a ride. I tried another good battery as a test, but got the same results. I had a new spare Ricks Reg/Rec, so I wired that in, and it made no change. I ran a ground from the RR mounting bolt to the negative post as well. The harness wires at the Reg/Rec are new and secure, I don't know about the wires nearer the stator, could that be a problem even though the stator ACV seems good? What else am I missing?

HamamatsuSuzi said:

I have a 1983 GR650 twin and I have a bit of a different charging problem. It charges between 12.9v and 13.5v. It charges highest at around 1800RPM and lowest at about 5000RPM. I hooked up my multimeter to the battery and placed it in my tank bag for testing. I suspected a faulty stator but it spec'd out good. It has 1.9 ohms between the three legs and no short to ground. It gives 72VAC, 72VAC, and 75VAC on the three phases on start up. After an hour ride the AC voltage test drops a bit to 63, 65, and 75. Could the weaker battery following the ride account for the lower AC voltage? Oh yeah, the battery is new and gets treated to a Genius charger after a ride. I tried another good battery as a test, but got the same results. I had a new spare Ricks Reg/Rec, so I wired that in, and it made no change. I ran a ground from the RR mounting bolt to the negative post as well. The harness wires at the Reg/Rec are new and secure, I don't know about the wires nearer the stator, could that be a problem even though the stator ACV seems good? What else am I missing?

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Are you sure the meter is ok? Sometimes meters read incorrectly.

If you do a "Quick Test" and post the results I can probably steer you in the right direction.

Sounds like the stator is weak or you are loosing voltage in the wiring. I've recently worked on a bike with similar charging voltage even though the no load AC voltage from the stator was reasonably high.

Stator should be wired directly into the R/R, bypassing the factory harness. R/R grounded to the battery or a solid frame point. Not the battery box or side panel. Lastly, verify you are not loosing power though resistance between the R/R power output line and the battery. Check the Stator Papers on how to check the system.

OK quick test completed. The battery charger was taken off 1/2 hour prior to test.
Key off--------13.05v
key on--------12.37v
at idle---------13.44v
at 2500--------13.06v
at 5000---------13.06
key off-----------13.14

I'm confident my multimeter is good. I have a 2nd one I bought a month ago and they both read very close. Thanks for doing this BTW.

Nessism said:

Sounds like the stator is weak or you are loosing voltage in the wiring. I've recently worked on a bike with similar charging voltage even though the no load AC voltage from the stator was reasonably high.

Stator should be wired directly into the R/R, bypassing the factory harness. R/R grounded to the battery or a solid frame point. Not the battery box or side panel. Lastly, verify you are not loosing power though resistance between the R/R power output line and the battery. Check the Stator Papers on how to check the system.

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If I bypass the harness, how close to the stator should I cut the wires. Is it good enough to cut them off behind the sprocket cover where I can get at them to solder? I have attached a lead from the battery neg to the reg/rec mounting bolt, is that good enough or should I run the black wire (ground) from the R/R to the battery instead of into the harness.
I will read more about the R/R power line. That's a check I don't know about.

HamamatsuSuzi said:

If I bypass the harness, how close to the stator should I cut the wires. Is it good enough to cut them off behind the sprocket cover where I can get at them to solder? I have attached a lead from the battery neg to the reg/rec mounting bolt, is that good enough or should I run the black wire (ground) from the R/R to the battery instead of into the harness.
I will read more about the R/R power line. That's a check I don't know about.

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I don't think you need to worry about the stator wires themselves, it's the harness proper that causes issues with resistance. Battery to R/R mount will work.

HamamatsuSuzi said:

OK quick test completed. The battery charger was taken off 1/2 hour prior to test.
Key off--------13.05v
key on--------12.37v
at idle---------13.44v
at 2500--------13.06v
at 5000---------13.06
key off-----------13.14

I'm confident my multimeter is good. I have a 2nd one I bought a month ago and they both read very close. Thanks for doing this BTW.

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Thes results say you are charging some we just don't know if it is stator or bad connections. Test the voltage drops according to the revised phase A stator tests. Measure at 5k rpm if they are bad start looking for the drops you need to chemically clean connections and crimps . See gs charging health in my signature. Seems to me the volt meter and battery are fine just low charging with fold back says very poor connections.

I have results from the positive and negative voltage drop tests.
The positive lead tested good at 0.15v at idle and 0.06v at 5000 RPM
The negative lead test was 0.66v at idle and 0.52v at 5000 RPM. So the negative lead test is a problem as it's above the 0.25v baseline. I already have an additional negative lead from the R/R mount to the neg battery post installed. Also I tested 0 resistance between the neg lead between the battery and its grounding bolt on the engine.
What do you make of the results?

HamamatsuSuzi said:

I have results from the positive and negative voltage drop tests.
The positive lead tested good at 0.15v at idle and 0.06v at 5000 RPM
The negative lead test was 0.66v at idle and 0.52v at 5000 RPM. So the negative lead test is a problem as it's above the 0.25v baseline. I already have an additional negative lead from the R/R mount to the neg battery post installed. Also I tested 0 resistance between the neg lead between the battery and its grounding bolt on the engine.
What do you make of the results?

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You can only measure the resistance using voltage drop. The resistance levels are well below 0.1 ohms.

You have a poor connections (resistance) somewhere. That is why there is voltage.

The positive leads measurements is suspect. It should always increase with RPM as the current goes up. Are you sure it is not 0.6V at 5K RPM?

Hamamatsu was a favorite of mine when I lived in Japan.
I would give a honda RR a try. The regulator part seems to be an issue
And you might have a bad diode out of the 6 causing problems. The oem
Regulators are suspect any way

Someone correct me if I'm wrong, but wouldn't a simple test be to connect the R/R ground and positive wires straight to the battery and then test voltage at 5000 rpm? If the system charges at 14 volts this way and 13.5 volts when the R/R is connected though the harness, then you have definitive evidence of a wiring problem. At any rate, this is what a member and I did with his bike when it was charging poorly. We took a known good R/R and hooked it up, yet the charging voltage was still low. Odd thing was the no-load AC voltage out of the stator was pretty good, yet the system was charging poorly at the battery under load.

I just tried Nessism's idea and hooked up a jumper between the R/R and the battery using the positive and negative leads. The results were 13.64v at 1500 RPM and 13.32v at 5000 RPM. A slight improvement, but not the answer. I guess this shows that the voltage drop in the harness is minimal.
Previous to this I closely examined the positive lead and the fuse box. Every spade connection is clean and shiny and measures no resistance within the fuse box and the positive lead to the battery.
Posplayr, I'm a bit confused on the positive lead voltage drop test. My test was a loss of under 0.25v. I thought that was a good thing. The negative test shower a loss of greater than 0.25v. But you are saying the voltage drop should increase with RPM, the same way battery voltage should increase with RPM?

duaneage said:

The regulator part seems to be an issue
And you might have a bad diode out of the 6 causing problems. The oem
Regulators are suspect any way

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This was my first thought as well. I did wire in a new Ricks R/R and got the identical results as the other R/R. Do you think a Honda R/R would make a difference?

Nessism said:

Someone correct me if I'm wrong, but wouldn't a simple test be to connect the R/R ground and positive wires straight to the battery and then test voltage at 5000 rpm? If the system charges at 14 volts this way and 13.5 volts when the R/R is connected though the harness, then you have definitive evidence of a wiring problem. At any rate, this is what a member and I did with his bike when it was charging poorly. We took a known good R/R and hooked it up, yet the charging voltage was still low. Odd thing was the no-load AC voltage out of the stator was pretty good, yet the system was charging poorly at the battery under load.

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Yes Ed, a swap out method is a well established approach to system diagnosis. Assuming that the swap out times minimal time, it works very well.

In diagnosing the issue there are really only four things that can be wrong

Low battery
Bad R/R
Bad Stator
Bad Wiring

So under "swap out theory"
If you can show a change in performance with a change of one of the items then you have identified the problem. The problem is complicated if you test with not known good. But eventually if you can show one case then that is sufficient for making a diagnosis of a bad part.

For purposes of "swap out" testing of the wiring, going direct to the battery should come close to eliminating the resistance and potential for voltage drops. And would confirm that wiring was an issue.

The Quick Test is an integrated test, which observes the charging system under different conditions. Depending upon deviations from normal operation, there is an ambiguity group (set of problems) that are indicated by a symptom or combination of symptoms. The down side of the Quick Test is that there are no absolutes, and there are a multiplicity of symptoms. How ever on the upside it does not require any swap out and is performed very quickly so any reduction in the ambiguity group (indicated failures) can be obtained very quickly and without much cost (time or money in parts).

If you can't tell I have been working on optimal diagnostic theories and approaches.

HamamatsuSuzi said:

This was my first thought as well. I did wire in a new Ricks R/R and got the identical results as the other R/R. Do you think a Honda R/R would make a difference?

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The ugly truth may end up being the stator. If the stator can't deliver power under old then it's done. All things considered it's easy to fix compared to other problems and other bikes. With no battery the system should run above 14 volts. You could try starting it then removing the negative from the battery. The bike should stay running and system voltage should be 14 or higher

If not the stator ( with the ricks rr ) is the last thing. It is the power source after all.

HamamatsuSuzi said:

I just tried Nessism's idea and hooked up a jumper between the R/R and the battery using the positive and negative leads. The results were 13.64v at 1500 RPM and 13.32v at 5000 RPM. A slight improvement, but not the answer. I guess this shows that the voltage drop in the harness is minimal.
Previous to this I closely examined the positive lead and the fuse box. Every spade connection is clean and shiny and measures no resistance within the fuse box and the positive lead to the battery.
Posplayr, I'm a bit confused on the positive lead voltage drop test. My test was a loss of under 0.25v. I thought that was a good thing. The negative test shower a loss of greater than 0.25v. But you are saying the voltage drop should increase with RPM, the same way battery voltage should increase with RPM?

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All voltage drops should be low and a total of less than 0.25V is acceptable. That would drop a 14.5V charging level to only 14.25V

Remember the voltage drops are associated with resistance values that are well below 0.1 ohms. At 10 amps it only requires 0.025 ohms to produce a 0.25V drop. So using alligator clips to go around the harness is probably not going to do it.

I used the 0.25V as an upper limit because if you have 0.25v on both + and - leads then a 14.5V R/R charging level will be reduced to 14.0V at the battery.

This is the absolute worst I would recommend and I would hope that you are closer to 0.25v total for both rather than 0.25v individually. If you clean the fuse box and ground chemically and then uses a contact cleaner like Deoxit you should be able to get the total drops under 0.1V-0.2V (TOTAL). Thus is then on the order of the voltage drops due to just finite wire sizes. Also the single point grounding I describe makes the current flowing between the battery and R/R less and so the voltage drops are less as well.

When you charging voltage drops as RPM goes up it is more than likely the connections. There is an increase in current demand as RPM goes up and so with increase current there are increased voltage losses and therefor less voltage at the battery.

It is also possible the stator is just at the hairy edge, but the only way to know that is if the battery voltage levels are no less than 14.5V - (total voltage drops).

HamamatsuSuzi said:

This was my first thought as well. I did wire in a new Ricks R/R and got the identical results as the other R/R. Do you think a Honda R/R would make a difference?

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Before changing any R/R, I would use the one you have and go through a process of cleaning the wiring until the voltage drops are as good as you can get them and then report the Quick Test results again. Then go from there.

I want to thank everyone for their assistance so far. I'm quickly learning about resistance and voltage drops, interesting.
I have cleaned my connections and was pretty happy with them, but I will go at it again. The fuse block is a sealed plastic unit with blade fuses. I would have to cut it to get inside. The ground cable is attached to a rear engine case bolt that requires the monoshock and mounting brackets be removed. Dam you Suzuki.
How acutely can resistance build up? It was only a short time ago that my system was putting put 14.7v at 5000 RPM. Like most riders here, I monitor it regularly.
Let me give you more history about my charging issue. The very first indication there was a problem was a dead battery during a ride. I charged the battery and hooked up my multimeter and went for a test ride. Charging was normal with high 13's at idle and 14.7v max at speed. After 8 minutes the voltage acutely dropped to battery voltage through all rev ranges. I replaced the battery the next day and did another test ride. Same results, normal charge, but at the 8 minute mark the charge was lost. I didn't include this information earlier because once I changed out the Reg/Rec, the intermittent charge was fixed, it was no longer an issue. It was just low.

HamamatsuSuzi said:

I want to thank everyone for their assistance so far. I'm quickly learning about resistance and voltage drops, interesting.
I have cleaned my connections and was pretty happy with them, but I will go at it again. The fuse block is a sealed plastic unit with blade fuses. I would have to cut it to get inside. The ground cable is attached to a rear engine case bolt that requires the monoshock and mounting brackets be removed. Dam you Suzuki.
How acutely can resistance build up? It was only a short time ago that my system was putting put 14.7v at 5000 RPM. Like most riders here, I monitor it regularly.
Let me give you more history about my charging issue. The very first indication there was a problem was a dead battery during a ride. I charged the battery and hooked up my multimeter and went for a test ride. Charging was normal with high 13's at idle and 14.7v max at speed. After 8 minutes the voltage acutely dropped to battery voltage through all rev ranges. I replaced the battery the next day and did another test ride. Same results, normal charge, but at the 8 minute mark the charge was lost. I didn't include this information earlier because once I changed out the Reg/Rec, the intermittent charge was fixed, it was no longer an issue. It was just low.

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If you have blade fuses you don't need to open it just clean all contacts on the outside. The back will pop off and only nee a little glue if you want to convince yourself of the same.

You ask:

How acutely can resistance build up?

I responded before that 0.025 ohms IS ACUTE to your charging system.


Try and measure 0.025 ohms with your VOM and
Compare it to the resistance to what get measuring other things that you think are a direct shorts. Your VOM probably does not even go below 0.1 ohms.

At 0.1 ohms lowest resolution of your VOM, corresponds to 1 V of error at 10 amps flow. You have two sides to measure, so you could measure 0.1 ohms on both sides and not be able to get over 12.5V at the battery when your R/R is putting out 14.5V (14.5-2.0=12.5V)


It takes very very very little (1/Very^3) resistance to upset the charging system so very very little (1/Very^2) is ACUTE. :-\\\