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Discussion Starter #1
Hi everyone,

I’m new here, so thanks for indulging me. I looked through some very helpful previous threads on charging system issues, but none seemed to address the exact problem I’m having, so I decided to start my own.

I have a 2009 Versys with approx. 36,000 miles. I recently had what I see is a common problem with this model — charging system failure due to a burnt stator. I replaced the stator with an ElectroSport ESG638, and the bike is now running fine, but I’m getting what I think are strange charging voltage readings.

At idle, voltage at the battery is around 14.1-14.4, but as engine speed rises to around 4,000-5,000 RPM, voltage DROPS to between 13.4-13.9 V. A little bit more information:

-Battery tested good at the local auto parts store. And it holds a charge (~12.8 V) very well.

-Tested rectifier resistance with a multimeter and everything seemed fine, but I didn’t have 3 12V batteries to complete the testing suggested in the service manual. Decided to replace with a $20 used stock R/R from Ebay, but nothing changed after switching them out — I’m getting the same voltage readings at the battery.

-Checked and cleaned engine and chassis grounds. They are clean and tight.

-After replacing the stator, voltage at the alternator lead connector seems fine, if a little high (I’m getting around 48-50 V).

My electrical knowledge is limited, and at this point I’m at a loss… could the battery be bad even though it load tested good? Could this be caused by a loose or corroded connection somewhere (if so, what might be a good place to start looking, since it’s not the engine or chassis grounds, and the alternator and R/R connectors look fine)? Or does the voltage drop with increasing RPM I’m describing fall somewhere in the range of normal behavior for the stock Versys charging system? Output at 4,000-5,000 RPM might (?) still be enough to charge the battery, but it’s not what I should be seeing according to the service manual.

The Polaris R/R mod seems like a great idea, and I think I'll give it a try this winter, but I want to figure out what’s going on with the setup I have now before diving into that…

Thanks again for reading.
 

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14.4V ~ 13.0V you at optimum operating voltage and from what I read all system is fine with your charging system. Take a few rides and see if there is any volyage drop in the battery. Polaris is good as its maintains constant voltage at 14.2V.
 

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How is the voltage after 5000RPM? does it keep dropping?
If the output voltage drops with an increase in frequency (rpm in this case), It might be due to parallel captivate effects or series inductive effects. Both are highly unlikely. I've never heard of these effects affecting motorcycles, but they are a constant pain during my work (as an electrical engineer). if your charging voltage is above the nominal voltage of the battery your good.
 

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Discussion Starter #4
Thanks for the replies. I went for a ~90 mile ride yesterday, and the battery seems to be maintaining a charge, so maybe I should forget about it. Just confused about why voltage would drop with increasing RPM, which seems backwards. @Lacsapix, there is pretty steady relationship between voltage drop and increase in RPM, and yes, it continues to decrease past 5000RPM. Seems like on average it drops about 0.1V per 1000RPM. But as @Fastoman points out, even at high RPM output is probably still enough to charge the battery. FYI there's no aftermarket electrical stuff or wiring on the bike other than a voltmeter (which I've verified using a multimeter at the battery). I'll probably just do the Polaris switch soon for peace of mind!
 

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Thanks for the replies. I went for a ~90 mile ride yesterday, and the battery seems to be maintaining a charge, so maybe I should forget about it. Just confused about why voltage would drop with increasing RPM, which seems backwards. @Lacsapix, there is pretty steady relationship between voltage drop and increase in RPM, and yes, it continues to decrease past 5000RPM. Seems like on average it drops about 0.1V per 1000RPM. But as @Fastoman points out, even at high RPM output is probably still enough to charge the battery. FYI there's no aftermarket electrical stuff or wiring on the bike other than a voltmeter (which I've verified using a multimeter at the battery). I'll probably just do the Polaris switch soon for peace of mind!

Two ideas:

1) Total long shot but wondering if there could be any loose/high resistance connections between regulator output and battery. In theory the output from the stator goes up with RPM. The Versys 650 uses a shunt regulator (many great posts from Onewizard on that subject matter) that shorts the output when the output voltage goes too high. The theory is as the RPMs increase the current output increases which creates a voltage drop that the regulator interprets as high battery voltage and kicks off the shunt activity. At lower RPMs there is less current, so the smaller voltage drop does not kick off the shut activity. Bottom line, double check all electrical connections (at these current levels you would probably see evidence of overheat/burning of the connections).

2) Another long shot, but since the stator isn’t stock could there be an issue with saturating the core at higher RPMs/higher current? Perhaps the stator is only capable of putting out XX watts of power and what you are seeing is the power limitation. Make sure to discuss this situation with the stator manufacturer.

Good luck.
 

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Two ideas:

1) Total long shot but wondering if there could be any loose/high resistance connections between regulator output and battery. In theory the output from the stator goes up with RPM. The Versys 650 uses a shunt regulator (many great posts from Onewizard on that subject matter) that shorts the output when the output voltage goes too high. The theory is as the RPMs increase the current output increases which creates a voltage drop that the regulator interprets as high battery voltage and kicks off the shunt activity. At lower RPMs there is less current, so the smaller voltage drop does not kick off the shut activity. Bottom line, double check all electrical connections (at these current levels you would probably see evidence of overheat/burning of the connections).

2) Another long shot, but since the stator isn’t stock could there be an issue with saturating the core at higher RPMs/higher current? Perhaps the stator is only capable of putting out XX watts of power and what you are seeing is the power limitation. Make sure to discuss this situation with the stator manufacturer.

Good luck.
Actually, after rereading your first post (sorry, reading comprehension not a strength!) the AC voltage output seems really high. Again, search for posts from Onewizard and/or look at the service manual. I seem to recall open circuit voltages in the 35V range (please double check me on that). If that is the case then the stator core is probably saturating because it's limiting power output (too many turns on the stator? Wye to delta conversion?).
 

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First check the 3 phase plug near the stator. maximum output is at or above 3500 RPM, voltage does not drop unless your fan is coming on or you have a loose connection.
Here are some links below. I would advise you to do my stator test using your voltmeter on volts AC at the stator plug, open circuit, follow my test procedure using 2000 RPM and the idle adjustment screw. Electrosport is one of the top recommended stator suppliers. If in doubt ask away, I check in every day or two, provided a response is made in the thread.


 

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Discussion Starter #8
Thanks @HelloFrom2012Versys650, all that is helpful. A few thoughts in response:

-The manual states AC output should be "42V or more," and says "If the output voltage shows much higher... the regulator/rectifier is damaged. A much lower reading... indicates that the alternator is defective." My guess was that 48V was okay in that case, but I could be wrong. It would be helpful if the manual was more specific about what "much higher" means.

-Your post reminds me of something I forgot to include in the original post. AC output (measured at alternator lead connector) rises from about 20-ish V (at idle) to around 48 V (at 4000-5000RPM), while DC voltage measured at the battery drops from, say, ~14.3 to ~13.8.

-Here is a thread in which another poster, @leftbrain99, had success using the same aftermarket stator, which is delta wound (Electrosport ESG638): Stator replacement. Not to say that saturation couldn't be the issue in my case.

Thanks @onewizard for the response, I will give your stator test a try and report back.
 

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First ignore what the manual says. My open circuit test and others exceed anything in the manual.
 

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Discussion Starter #10
Hi @onewizard, just did your stator test with the idle set to ~2000RPM. All three readings were very close to each other, between 27.1 and 27.4 V. Based on that I'm guessing the Electrosport stator checks out okay?
 

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Discussion Starter #12
Thanks. Like you say, since the stator, R/R (stock), and battery all check out fine, I'm starting to suspect this is some kind of wiring / connection issue (yay). The chassis and engine grounds look good. The alternator lead connector and R/R connector both look fine (no signs of burning, melting, etc.). Since the battery is charging okay, I'll probably put this on the back burner and just trace the relevant wiring next time I take the bike apart more substantially. Will update if any new developments...
 

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Explanation as applied using a Series regulator

If it were possible, 14.2 VDC measured at the battery isn't a issue, as to 13.3 to 13.5 VDC at idle is normal, I run my idle close to 1500 RPM, which gives me a higher idle voltage, the prime reason for that is during hot days, the fan draws approximately 80 watts, this will discharge the battery. Note what most battery tenders and chargers have a 1 amp charge limit. Consider on a hot day that the battery will also be hot, Going from 1300 to 1350 RPM and say 13.2 VDC or less with the fan running and then raising to 3500 RPM or higher, expect the charge current to be around 6 to 8 amp, yes possibly 3 or 4 minutes, the point is, this could very well cause a shortened battery life and or failure.


Explanation as applied using a Shunt regulator

Using a shunt regulator, no advantage of going above 1350 RPM, nore is there a advantage of converting to LED lighting, unless it is for more lumins. In fact doing a drastic conversion to LED could cause shunt regulator and stator failure. My 2015 650ABS is 100%LED. I am using SafeGo LED in both low and high beam, I can run both at idle ( 1500 RPM) and stay in the green with all 3 led on;
 

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Discussion Starter #15
Just in case anyone was following this thread, I never did get to the bottom of what was causing the drop in charging voltage with increased RPM, but I did replace the stock regulator with a Polaris 4012941. Charging voltage is now behaving as it should, consistently around ~14.2 V. Thanks to those of you who made that mod possible.
 
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