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Overvoltage Protection Help

Flyyak

Well Known Member
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Need help with a basic overvoltage protection module or system. I have an RV7 with about 300 hours, a two screen G3X non touch and a G5, wiring harness prepared by Stein Air. Basic circuit breakers together with a 24 place fuse panel with 12 places assigned for avionics buss and 12 for sub fuse block buss. I have a alternator field CB and an Alternator field switch. The switch will cut/turn off the alternator to the main buss. I have installed an emergency battery LiFePO4 which is connected via a switch to back feed the avionics buss. I will attempt to attach a copy of my wiring diagram, photo of emergency battery and fuse panel for your review. I have replaced the Narco and indicator with a Garmin SL30 which is wired by RS232 direct to G5 rather than going through the can buss.

I have had very poor luck with PC680 odyssey batteries and have just replaced my last one with a Shorai LFX18A1-BS12. I have monitored the charging system closely since this replacement and have noted that after starting, the voltage may read on the G3X up to 14.6 or 7 and amps +3 or 4 for a very short period. I leave it at engine idle for several minutes before moving and the voltage drops to 14.4 and amps to +1 or 2. After a very short period the voltage will read 14.4 and amps will be at 0. Is that normal?

I have never had voltage above 14.8 with a dying odyssey or amps over +4. After reading many post when researching the Shorai battery there were concerns about a malfunctioning alternator, I have thought that it would be prudent to install an over voltage system to protect my avionics and the Shorai LiFePO4 battery and an under voltage protection for the battery. My emergency battery is not connected to be recharged by the alternator and I use it strictly as an emergency power source for my avionics. I charge it outside of my aircraft with a special charger (CTEK) and it will power up to 10 amps for over an hour (at least that what my bench test confirmed).

I have reviewed the Perhelion Design OV module and it may be sufficient wired per his diagram in between my alt fld switch. I have also purchased a relay module from Amazon VR1000 Single Phase Protection Relay Over-Voltage 9V-18V Under-Voltage 0.1V-6V AC/DC(D12)
by YWBL-WH but I do not think it will work.

If you have a simple wiring diagram or modules that I can plug and play, please post. I have attached a couple of pdf photos and a woiring diagram but I am not sure that I did it right. ThanksView attachment Electrical Schematic - Rev. 4.pdf

View attachment emergency LifePo4 bat.pdf

View attachment fuse panel with lighted fuses.pdf
 
You don't mention what alternator you have or whether it is internally or externally regulated. Also, does your Shorai battery have a BMS?
 
It's a standard Van's alternator, internally regulated and has operated flawlessly. Here is another attempt to add my wiring diagram. It's a pdf file so if it does not upload and someone can tell me a better way to attach it I would appreciate it.
 

Attachments

  • Electrical Schematic - Rev. 4.pdf
    195.3 KB · Views: 229
No BMS on Shorai. They have a special charger that is suppose to balance cells but I understand that you may only need to use it maybe every 6 months. Shorai customer support indicated that my CTEK which is specifically made to charge LIfEpo4 batteries should do fine. I also spoke to a couple of guys on this forum who said that they hardly ever attach a charger to their Shorai.
 

Right, I note that Shorai batteries don't have a BMS. But even those Lithium batteries that do, over-voltage protection is still required or recommended. So your plan to install the Perihelion unit would be a good move with the internally regulated alternator.

You could wire your back-up battery with a diode and resistor to have your alternator trickle charge it in flight if you wanted to. It certainly would be more convenient.
 
OV protection

As stated above, 14.7V is fine. The initial jump of +4A is fine. It's showing the amount of amps charging the battery. You will always see 0 to +2A to keep the battery topped off.

If you have an alternator with an internal regulator that doesn't have OV protection like a regular automotive alternator (regardless if it's a 1-wire or 3-wire) then you would want to add a contactor between the alternator and battery contactor so you can disconnect the B-lead from the main bus. The reason is because it's possible for the alternator to fail in such a way that you will not be able to turn Off the alternator with the field wire so by using a contactor you can manually disconnect the B-lead. The field wire is connected to the contactor which connects/disconnects the B-lead with a breaker switch (field breaker switch). The OV Protection module (whether it be Perhelion, B&C, or some other brand) is connected to in series between the field breaker switch and the contactor. When the OV module detects a voltage a little above 16V the OV module automatically trips the field switch which causes the contactor to open. OV module detects the over voltage in milliseconds. I don't know how true it is but it's said voltage runaway on an alternator (although rare) can happen quickly, 2-5 secs, I don't know. It's cheap insurance in protecting your electronics.

Find out what alternator you have and check if it has OV protection. If it's a B&C then it has OV protection
 
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I have monitored the charging system closely since this replacement and have noted that after starting, the voltage may read on the G3X up to 14.6 or 7 and amps +3 or 4 for a very short period. I leave it at engine idle for several minutes before moving and the voltage drops to 14.4 and amps to +1 or 2. After a very short period the voltage will read 14.4 and amps will be at 0. Is that normal?

I think what you're seeing is normal and just your regulator adjusting the voltage between 14.4 and 14.7 volts. Some of that could be indication error, I suppose. Initially after engine start, it is normal to have an inrush of amperage to your battery to replace the energy that you just used to start, and once it's topped off, the amps should settle near zero. Looks like your shunt is set up to measure amps going to and from the battery and not the output of the alternator, so what you're seeing is normal.
 
Maybe it's just me

I would never be comfortable with an internally regulated alternator and a Lithium iron battery. I know it's rare, but it has already happened to an RV-8A. The alternator failed, and the internal voltage regulator dumped the alternator's output directly back into the field causing a huge over voltage. There was no way to turn the alternator off! The lithium iron battery torched off, and the pilot had to land on a road with a toxic smoke filled cockpit and a battery fire by his right foot! That was a close one!

I say just don't do it! I don't think you will find an internally regulated alternator on a certified aircraft. Add a lithium battery, and you are courting a possible inflight fire disaster.

Note: I have a Shorai lithium iron battery in my Kawasaki jetski, and my Yamaha motorcycle. I love the way they hold their charge for months. If I ever have one torch off, I'll stop the bike and get off or go swimming.
 
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Van's supplied Nippon-Denso alternators are internally regulated and in their stock state you're not controlling the field with the alternator switch or CB, you're only removing a signal to the regulator to do it's job (IGN). These regulators get field power internally and if the regulator fails there is a remote possibility it could fail in overvoltage and the interruption of the IGN signal with a crowbar over voltage module won't do anything to stop alternator output.

It's suggested to add a contractor to open alternator output (B lead) to the system. This is one way of doing it. There is the possibility that sudden interruption of alternator output this way will fry your regulator, but if the regulator wasn't doing its job then it's not an issue.

Option #2 is to modify the internal regulator to remove internal field supply and make the IGN wire a true field wire. Then use the OVM to interrupt the field. This is the route I took and how a popular PMAed aircraft alternator company modifies ND alternator and sells them for a premium. Here are the directions from Bob Nickols to accomplishs this...

http://www.aeroelectric.com/articles/Nipon-Denso_Alternator_Mod.pdf

Also here's a good write-up by another Tim that clearly shows this same mod made to ND alternators by name brand companies. https://www.myrv10.com/N104CD/maintenance/20191213_Fall_Winter_Projects/index.html
 
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Wow. Great articles. Do you know if the Van’s supplied alternators are true Nippondenso alternators?
 
Vans Alternators

I believe that Van’s supplies Plane Power alternators in their FF kits. Plane Power alternators have OV protection. My FF kit from 11 years ago had a Plane Power alternator.
 
Why would you risk all your avionics and a possible fire? Use an aircraft alternator such as the BandC, with an external regulator and OV protection circuit. If you are not familiar with working on electronics, modifying an alternator probably not for you. I agree with Danny. Also, I would not use the Shorei batt. Earth X has spent a lot of effort getting their Lifpo batt certified and safe for aircraft use. If you insist on using a Lifpo in your aircraft, you might consider them. I personally have been using the Odessey’s and get about 5 years out of them.
 
Why would you risk all your avionics and a possible fire? Use an aircraft alternator such as the BandC, with an external regulator and OV protection circuit. If you are not familiar with working on electronics, modifying an alternator probably not for you. I agree with Danny. Also, I would not use the Shorei batt. Earth X has spent a lot of effort getting their Lifpo batt certified and safe for aircraft use. If you insist on using a Lifpo in your aircraft, you might consider them. I personally have been using the Odessey’s and get about 5 years out of them.

Though I agree the modification of a voltage regulator should be left for the familiar, it is hardly difficult and not risky. If you're building an airplane it is certainly within the scope of those capabilities. Besides, BnC and PP are just ND clones modified for OV protection and/or external regulation. They were certainly smart to just modify what works very well (ND alts) instead of reinventing the wheel.

I see your point though...if you're dishing out fat stacks for an airplane why not just pay for the already modified ND alternator from BnC? I just chose to modify the Van's ND alternator so if I'm in BFE I can purchase the same rig from Napa to get airborne rather than pay for a rental car and chance my life on the road with the normal crazies...now that is risky!
 
I have done a great deal of research and my alternator is Van’s 60A 14684 alternator which is an alternator that has been used for many years in the automotive industry. There have been several articles written as they relate to modifying these alternators to an externally regulated alternator with overvoltage protection. Nuckolls is the author of one modification and a couple of other (I think engineers) have simplified the modification.

I will use the process set forth in the last article in kitplane using the spacer and removal of the internal regulator with the addition of the TranspoV1200 external regulator with overvoltage protection (Amazon for $69.00)

I would appreciate others review of this modification of the 14684 alternator that many RV’s are probably using. I think many of us non engineers or electrically handicapped folks will appreciate your opinions and insights. Thanks

http://www.aeroelectric.com/articles/Alternators/One-Wire_Alternator_Conversion.pdf

https://www.kitplanes.com/rewiring-a-nippondenso-alternator/

https://www.kitplanes.com/alternator-mods-without-major-surgery/
 
Planning my eventual plane power defection....

I’m running a plane power 60a and planning my eventual failure/ defection (currently 133 hours, picking up my pace). I’m thinking a real ND internally regulated alt with a Perihion OV is an elegant and not-intrusive solution. How/ where do you get a REAL NEW ND alternator?
 
From my limited research, I do not think the internal regulator plus perihelion OV module will solve the run away alternator. When one reads Mr. Nuckolls he points out that interruption of the alternator field wire will not cut off the run away alternator. But he also points out that if the Nippondenso alternator is modified to accept an external regulator, then an overvoltage devise can be added whether it is separate or part of the external regulator. I have now read about a few, BandC and TranspoV1200. You may be able to use another regulator and the perihelion as the OV module.
 
Field control

Maybe my understanding is off, but I thought if the field, which is externally controlled, is turned off, the alternator is shut down completely. In other words, the alternator makes no power without the field energized. The OV module does this- opens the field circuit when thinks her whonky.
 
I’m running a plane power 60a and planning my eventual failure/ defection (currently 133 hours, picking up my pace). I’m thinking a real ND internally regulated alt with a Perihion OV is an elegant and not-intrusive solution. How/ where do you get a REAL NEW ND alternator?

It took some research on the part numbers (they dont use Lester #s), but I found alternators that were rebuilt by ND themselves. More expensive, but you can count on the ND quality. I am confident that they leave the factory with the same quality as new, unlike your average aftermarket rebuilder. Got one at Summit for $70 last year.

Larry
 
I’m running a plane power 60a and planning my eventual failure/ defection (currently 133 hours, picking up my pace). I’m thinking a real ND internally regulated alt with a Perihion OV is an elegant and not-intrusive solution. How/ where do you get a REAL NEW ND alternator?

Search for Lester #14684, but unfortunately this alternator has been out of new production for a while so you can only get rebuilds.

Adding Perihion OV to IR ND alternator doesn't cover you 100%...there is a failure internally that could cause the OV to occur and the OV module doesn't shut down the alternator. If you complete the modifications I posted in the article, the modifications PP does, you can keep internal regulation and prevent the OV situation explained in the article.
 
It took some research on the part numbers (they dont use Lester #s), but I found alternators that were rebuilt by ND themselves. More expensive, but you can count on the ND quality. I am confident that they leave the factory with the same quality as new, unlike your average aftermarket rebuilder. Got one at Summit for $70 last year.

Larry

Great to know!!
 
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