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  #21  
Old 02-14-2017, 10:17 AM
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Quote:
Originally Posted by Alan Carroll View Post
I may be misreading the OP's statement; I took it to be saying that the battery was at 12.65 after flight (without the engine not turning). If that's the case then it doesn't appear the battery is actually discharging. If he means its reading 12.65 with the alternator operating then yes, something's broken.
If the battery is fully charged then wouldn't the voltage regulator reduce the voltage if its not required across the bus?
Joe?
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Last edited by Jetguy : 02-14-2017 at 10:32 AM.
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  #22  
Old 02-14-2017, 10:42 AM
Mich48041 Mich48041 is offline
 
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The voltage regulator tries to maintain a constant voltage regardless of the battery state of charge. It seems that the Ducati is set for about 13.8 volts, at least on my plane. Since the Rotax starts so quickly, the battery does not get discharged very much and 13.8 volts is adequate, barely. The John Deere regulator that I installed maintains about 14.1 volts. Many car regulators are set at 14.2 volts. Anywhere between 14 and 14.5 is OK. At engine RPM below about 3000, the dynamo is unable to maintain that high of a voltage with a full electrical load. If system voltage drops below battery voltage, then current will be drawn from the battery. Electrical loads will always draw current from the source with the highest voltage, either battery or charging system.
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  #23  
Old 02-14-2017, 10:53 AM
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Originally Posted by Mich48041 View Post
The voltage regulator tries to maintain a constant voltage regardless of the battery state of charge. It seems that the Ducati is set for about 13.8 volts, at least on my plane. Since the Rotax starts so quickly, the battery does not get discharged very much and 13.8 volts is adequate, barely. The John Deere regulator that I installed maintains about 14.1 volts. Many car regulators are set at 14.2 volts. Anywhere between 14 and 14.5 is OK. At engine RPM below about 3000, the dynamo is unable to maintain that high of a voltage with a full electrical load. If system voltage drops below battery voltage, then current will be drawn from the battery. Electrical loads will always draw current from the source with the highest voltage, either battery or charging system.
Next question, is it possible that the voltage seen on the skyview could have an error of +- .4?
Joe?
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  #24  
Old 02-14-2017, 11:02 AM
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Originally Posted by Jetguy View Post
Next question, is it possible that the voltage seen on the skyview could have an error of +- .4?
Joe?
Can't comment on the Skyview specifically but on my plane I have volts measured by two different instruments, and its common for them to disagree by a couple of tenths. An error of 0.4v sounds seems less likely though.
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  #25  
Old 02-14-2017, 11:44 AM
Mich48041 Mich48041 is offline
 
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The accuracy is a question for Dynon. I do not know. There is a big difference between resolution and accuracy. Digital displays might have a resolution of 0.1 or even 0.01, but their accuracy might only be plus or minus 1. Fuel level and fuel pressure are examples. They both have analog sensors but display high resolution digital numbers that are far from accurate.
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  #26  
Old 02-14-2017, 11:49 AM
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Phantom30 Phantom30 is offline
 
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Quote:
Originally Posted by BillL View Post
It is not just the RV12 - a little searching turned up this: From an electrical engineer of 34 years of product development

"In our over 1000 hours in our CRUZ LSA, we have replaced our Rotax Specified Ducati AC to DC Rectifier/Regulator (R/R) box four times."

So - it is not just the RV12 - Vans is your agent to beat on Rotax, Vans can not fix this issue. Gather a group, talk to The Man, get some action.
Bill,

Very interesting article....looks like changing the capitor could have more to do with this problem; also, the SH vr (if considering a li-fe battery)!!
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  #27  
Old 02-14-2017, 12:49 PM
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Originally Posted by olderthandirt View Post
Sorry I know this has been beaten to death, but today my Ducati VR is probably on last leg..I have 26.4 total hours on plane and VR is under panel....today it was showing at idle -.1 and -.2 and in air +2 and battery discharged to 12.6 after hour of flight..it started out 13.7 because I have a battery maintainer on it...if everyone agrees it is going out I have a JD VR which I can install with a modified plate...just asking
After reading through this thread and considering my own experience with my RV12 and without further data this regulator seems to be operating normally! Here is my rational.

Normal battery voltage is 12.6 volts. He had it on a maintainer which would show a higher voltage which may go down over a few days without the maintainer.

We are only talking about a few tens of a volt here so 13.7 seen on the skyview could have been 14.0 volts.

At lower RPMs like idle you're not going to see much more than battery voltage because the charging system on the rotax is similar to an old generator. More RPM means higher voltage and vice versa.

Again at low RPMs like in the pattern the battery supplements the electrical requirement of the 12. So you would see -.1 and -.2 occasionally.

I suggest flying the plane some more to see how the regulator operates before changing it out. Leave the maintainer off the battery for a while to.
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  #28  
Old 02-14-2017, 02:19 PM
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Phantom30 Phantom30 is offline
 
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Quote:
Originally Posted by Mich48041 View Post
The accuracy is a question for Dynon. I do not know. There is a big difference between resolution and accuracy. Digital displays might have a resolution of 0.1 or even 0.01, but their accuracy might only be plus or minus 1. Fuel level and fuel pressure are examples. They both have analog sensors but display high resolution digital numbers that are far from accurate.
Joe,

If one were to install a 47mf 63v capacitor.....would you know where the easiest place to wire into our electrical system? And would the 22mf capacitor have to be removed?
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Ric Dickison
307 (CAB) Phantom
Search and Destroy (Can
Tho RVN)
Distinguished Flying Cross Society Member
CH-47 & UH-1H "Driver"
Rotax 9 Series Service IRMT

RV-12 Kit#729 "N312RD" is now a full functioning fun machine!! Thanks Van for fulfilling my dream😎
2017 Dues Paid
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  #29  
Old 02-14-2017, 02:55 PM
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KALEWIS KALEWIS is offline
 
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When ours "failed" it was only showing 12.5 or so in cruise flight .... which means no charge at all. Anything below 3500 RPM is not telling you the whole story as far as recharging the battery.
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  #30  
Old 02-14-2017, 03:01 PM
olderthandirt olderthandirt is offline
 
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Default VR going out

Thanks to everyone for suggestions/help...I will go up again for longer period and see if batter goes down below 12...which it did originally till the guys at Arlington change a wire and it then maintained a good charge up flying..till couple days ago...happy to go up just give me a excuse to fly
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