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Shout out to Hartzell/PlanePower

Dorfie

Well Known Member
In September 2022 my main alternator (PP 60 amp) failed after 472 hours in service. I was in Prescott, AZ at the time. I flew back on the backup alternator (B+C 40 amp) without any issues.
Back at home I removed and disassembled the PP alternator. It was clear that some of the diodes were blown. My plan was to replace the diodes and use the alternator again. To my surprise I also found that the rear outer bearing shell was loose in its housing and could rotate inside the housing. The bearing itself was smooth as can be and spun normally. This did not seem normal to me. I wrote to Hartzell to report what I believed was a new (to me) mode of failure and an unacceptable mode of failure. I have always set the belt tension per Vans instructions using the torque-slip method and did not think that the belt tension was excessive to explain the loose rear bearing. At this time I was already planning on replacing the PP alternator with another make.
Within a couple of hours, I received a detailed response from Hartzell. I copy the response from Timothy Gauntt from Hartzell below with his permission. I was impressed with their rapid response as well as the improvements that were made to the later model alternators. I now still have a PP alternator and will see what the future holds!

"Thank you for your feedback. Regarding our AL12-EI60 kits and/or the 99-1012 alternator in those kits, there have been production improvements implemented since we purchased the product line from the legacy Plane Power company. In short, what many owners have experienced is a known and resolved issue to us. We feel there was a design discrepancy in the product prior to our acquisition. To explain; originally, there are four bolts that secured the front and rear housings. Two of these bolts have “feet” incorporated that secure the stator assembly. If the stator is not secured, it will loosen, contact the rotor and “spin”, ultimately failing the alternator rectifier assembly and/or rear bearing. The housings clamp together with no gap between them as found in other typical alternator designs so stator retention was dependent on the housing tolerances and through bolt torque, especially on the through bolts with the “feet”. We upgraded this design several years ago which now requires the stator be a press fit into the rear housing and that, along with the original “feet”, correctly positions and secures the stator assembly. This has fully rectified the known field issue. Failures of this type would have been the most prevalent in the 2018 and prior manufacturing dates by serial number. (H-Sxxxx = 2018, H-Rxxxx = 2017, H-Qxxxx = 2016, etc.) The serial number provided indicates the alternator was manufactured in approximately the 38th week or 2013.
We also believe a Plane Power customer should expect to get more than 470 hours’ time-in-service from any of our products. To that end, please complete the linked form and return per the form instructions so we can replace the alternator to you as a customer service. https://planepower.aero/aircraft-alternator-support/warranty/"
 
Apparently mileage may vary. I’ve had two PP alternators fail in the last week. First one had 150 hours, second one had less than 10 minutes before it failed.

Both alternators were part of Van’s firewall forward kit.

When I called Hartzell to ask for warranty replacement, they asked for the serial numbers. The lady I was talking to advised me those alternators were built in 2012 and 2014 and hartzell did not build them so would not warranty them, even though they were well within the warranty period. Lady remarked to me and I quote “ would you warranty something you didn’t build”. And I replied well if it had my company name and logo on the data plate of course I would.

They agreed to have a look at them so I sent them in.

Today I was informed that they would not warrant or repair them as it was according to them not a manufacturer defect. They claimed the diode burned out due to over heating. I didn’t buy into that in that the second alternator never even flew, ran less than 5 minutes on an un cowled engine.

When I suggested that there was quite a lot of bad reviews on the forum their response was “ you have to take that with a grain of salt, most people cause the failure by using lipo batteries without a battery manager, or introduced FOD during aircraft construction.

I have now had 3 PP alternators fail.
 
To my surprise I also found that the rear outer bearing shell was loose in its housing and could rotate inside the housing.

That particular problem has been around a while. I had one in which the rotor would just barely scrape the stator when hot. The rear bearing recess was enlarged, so the brush end of the rotor could wobble around.

The bore is machined as a slip fit (same ID as the bearing OD), to allow for axial expansion of the rotor in operation. Bill Lane did a nice analysis illustrating radial bore expansion at 250F as being 0.0015". Unless some provision is made to keep the outer race from turning in the expanded bore, the bore will wear and enlarge...potentially a lot. Read here:

https://vansairforce.net/community/showthread.php?p=1535221

Note the inspection procedure which will catch an enlarged bore...chuck the pulley in lathe jaws, or in a padded vice, and wiggle the brush/regulator end of the case back and forth. Any movement is cause for overhaul.
 
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Anyone have a source for the wire harness or plug for the Denzo alternator?

Just buy the one from B&C, $17. The L-40 is the same alternator except B&C takes it apart and modifies it for external regulator, works perfect with Denso internal regulator. The field connector and harness are the same.

https://bandc.com/product/replaceme...-alternators-l-40-bc410-h-bc425-h-sk35-lom30/

and depending on your engine, you might need the mounting kit from B&C order from their replacement parts link I posted above where you order the field plug and wire harness
 

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I have often posted negative things about the all too common failures of these alternators. It is encouraging to hear that Hartzell is not just kicking the can on this issue and taking accountability and fixing what I always assumed was a poor design. I hope it makes this a better product for those that are purchasing it, but I still wonder if there are other issues in the design that plague this product. My dollars will continue to vote for other options.

Larry
 
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A

I have now had 3 PP alternators fail.

between that and all of the bad experiences reported here, I have to say some of that is on you. At some point you have to accept the fact that quality is an issue with this product and any way you cut it, they just do not last as long as most products we are accustomed to. I have had a $40 denso on my 6 for 850 trouble free hours. The B&C alt's don't seem to have issues like the PP. I think it is time for you to move on to another option.

Kind of sad that hartzell doesn't recognize that when you buy a company, you buy all of it, including their failures. This is why we do due diligence.
 
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between that and all of the bad experiences reported here, I have to say some of that is on you. At some point you have to accept the fact that quality is an issue with this product. I have had a $40 denso on my 6 for 850 trouble free hours. The B&C alt's don't seem to have issues like the PP. I think it is time for you to move on to another option.

Don’t know how you could say some of that is on me. That is what Vans supplied in the firewall forward kits on planes I acquired.

The early versions that Vans supplied before hartzell bought them out had a design flaw no doubt. Hartzell did replace the one with a bearing failure.

The other two previously discussed they refused to warranty.

What upsets me the most is they will not repair failed alternators.

And no where did I say I was buying another PP alternator
 
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Don’t know how you could say some of that is on me. That is what Vans supplied in the firewall forward kits on planes I acquired.

The early versions that Vans supplied before hartzell bought them out had a design flaw no doubt. Hartzell did replace the one with a bearing failure.

The other two previously discussed they refused to warranty.

What upsets me the most is they will not repair failed alternators.

And no where did I say I was buying another PP alternator

Sorry, didn't mean to be negative. Only saying that with the resources available today, we are more empowered to weed out issues like this. I use the information available on this site to research most products that I purchase. Fortunately most any common issue with quality or vendor support can be found in the archives, as our brothers and sisters here are pretty good about posting their problems and experiences. An example, I read that the Vans supplied kit tires did not wear that well and seemed to have a short life. Not Vans fault as they are just trying to keep costs down, but based upon that chose to have them removed from my kit and instead bought different tires. If I had ordered an FWF kit, I would have eliminated the PP alt based upon what I have read here and instead purchased a B&C, which has a stellar reputation here.
 
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Yes, let me get the link posted - - i have to look it up.

All the pieces, connector, terminals, and strain relief plugs. https://www.driftmotion.com/category-s/1847.htm

Connector only =https://www.driftmotion.com/Oval-Alternator-Conn-3-Pin-p/dm2085.htm https://www.driftmotion.com/Oval-Alternator-Conn-3-Pin-p/dm2085.htm




That connector wont work on the Denso I posted a link to, there are different Denso connectors. The Denso I posted in this thread is the model B&C buys and converts to the L-40, I posted a link to the correct connector with harness, or you can get a connector from autozone with a shorter harness, but the one B&C sells for 17 bucks comes with aviation wire and a 3 or 4 foot long harness. I have the Denso alternator and B&C install kit and field harness in my basement, bought one for another plane after having good experience with my first one, I will go look at the field harness length and post the length

here is the Alternator and B&C L-40 harness

Thats about 10 feet of wire with the B&C $17. harness

Thats under $150. total for alternator and harness, the mount kit B&C sells will add another 100 or so if you need that
 

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Just buy the one from B&C, $17. The L-40 is the same alternator except B&C takes it apart and modifies it for external regulator, works perfect with Denso internal regulator. The field connector and harness are the same.

https://bandc.com/product/replaceme...-alternators-l-40-bc410-h-bc425-h-sk35-lom30/

and depending on your engine, you might need the mounting kit from B&C order from their replacement parts link I posted above where you order the field plug and wire harness

Looks perfect but no over voltage protection.
 
<<<<SNIP>>>>

Kind of sad that hartzell doesn't recognize that when you buy a company, you buy all of it, including their failures. This is why we do due diligence.

[While I use the snippet from this poster, this message is NOT targeted at the poster but a commentary to us all. If you wish to flame me about it, please send to me directly.]

''''''''''''''''''''''''

I must offer a DIFFERENT opinion here.

First, (AGAIN), I own B&C as well as PP alternators in different RVs.
So this is not about a bias for one over another.

Since the Hartzell purchase, I have had nothing but superior responses and support from PP regarding failures of "legacy PP alternators". (As mentioned by the OP on this thread.)

They (Hartzell) OWNED the problems. They described the "re-engineering" that they felt that they had to do and DID IT.

They did not back down one iota from the problems during my interactions.
And yes, I too have had multiple failures of the PP (and other) alternators.

My point here is to say, yes, we need to call out issues with products but when there is evidence that the manufacturer is working hard to fix such, we need to acknowledge that as well.

To each his/her own regarding what you purchase. But let's make sure that we don't cause manufacturers who are trying very hard, each and every day, to say it's no longer worth it and we we are left with fewer options.

On a more personal side, I, like another poster mentioned, like to use as many of the "other" vendors as possible.

The innovators.

The ones who take a chance on the experimental world when others would not.

Without them, we would not have the bevy of quality products that are available to us today.

Every supplier that I have referenced in posts on this forum has had some serious issues at one time or another. But each and every one that I have quietly worked with has gone the extra mile to provide (as far as I am concerned) a most acceptable solution.
 
[While I use the snippet from this poster, this message is NOT targeted at the poster but a commentary to us all. If you wish to flame me about it, please send to me directly.]

''''''''''''''''''''''''

I must offer a DIFFERENT opinion here.

First, (AGAIN), I own B&C as well as PP alternators in different RVs.
So this is not about a bias for one over another.

Since the Hartzell purchase, I have had nothing but superior responses and support from PP regarding failures of "legacy PP alternators". (As mentioned by the OP on this thread.)

They (Hartzell) OWNED the problems. They described the "re-engineering" that they felt that they had to do and DID IT.

They did not back down one iota from the problems during my interactions.
And yes, I too have had multiple failures of the PP (and other) alternators.

My point here is to say, yes, we need to call out issues with products but when there is evidence that the manufacturer is working hard to fix such, we need to acknowledge that as well.

To each his/her own regarding what you purchase. But let's make sure that we don't cause manufacturers who are trying very hard, each and every day, to say it's no longer worth it and we we are left with fewer options.

On a more personal side, I, like another poster mentioned, like to use as many of the "other" vendors as possible.

The innovators.

The ones who take a chance on the experimental world when others would not.

Without them, we would not have the bevy of quality products that are available to us today.

Every supplier that I have referenced in posts on this forum has had some serious issues at one time or another. But each and every one that I have quietly worked with has gone the extra mile to provide (as far as I am concerned) a most acceptable solution.

No flaming at all. Multiple opinions help all of us. I felt the same way you did when I read the intial post, at least until the other poster mentioned that Hartzel told him that the product made by the previous company was not their problem and wouldn't address it and further blamed the installer. I am glad they are fixing the problems, but IMHO they need to address the problems with the legacy products that are still failing. You buy a company, you are responsible for what they did in the past. Sorry, but that is just the way it works. If you can't accept that, then don't buy them. Many ways to address it, including charging a nominal price to upgrade a customers product to the new version or selling a field upgrade kit, etc.

Innovation is great until the innovator starts using customers as their test bed and refuses to push updates to them once they have been used to flush out the flaws. By their own admission, it was a poor design so why not step up with a remediation plan for all the affected customers out there. It doesn't have to be free, just reasonable. I think most customers would understand the spot Hartzel is in and would pay to cover some or all of the actual costs. Saying "tough S***, buy another one at full price" isn't an answer that will protect your reputation.
 
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Looks perfect but no over voltage protection.

You are kidding right

Plenty of overvoltage protection, my voltmeter. The reason I changed to the Denso is the generator was overvolting the system. The voltmeter is in my scan, right next to the altimeter, never fly without it.

What is your dont crash into the ground protection? You look at it.
 
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You are kidding right

Plenty of overvoltage protection, my voltmeter. The reason I changed to the Denso is the generator was overvolting the system. The voltmeter is in my scan, right next to the altimeter, never fly without it.

What is your dont crash into the ground protection? You look at it.

You're kidding, right?
 
Searched overvolt protection and this thread popped up, interesting
.
Frank they do have OV protection. The crow bar is a bad bad idea with internal VR alternators.

The internal VR has an IC chip that includes all the functions needed to protect from a list of possible conditions:

>SHORT-CIRCUIT FIELD PROTECTION
>SHORT-CIRCUIT LIGHT PROTECTION
>SHORT-CIRCUIT CHOKE (ACTIVE LIGHT)
>SOFT-START FREQUENCY 100HZ
>LOAD RESPONSE, 10 SECOND DELAY
>PULSE WIDTH MODULATION
>PASSES FULL LOAD DUMP
>OVERVOLTAGE, UNDERVOLTAGE, BROKEN-BELT and FAIL-SAFE INDICATOR LIGHT FUNCTIONS
>LOSS OF SENSE INDICATOR FUNCTION
>BIPOLAR TRANSISTOR
>TEMPERATURE COMPENSATION PERFORMANCE (-10MV/C)

A lot of the mis-information and myths are based on old ideas. A few other folks (not Frank) with a big soapbox perpetuate myths about internally regulated alternators, like they have no OV protection. That's totally NOT true and just ignorant. Also claims they are prone to wild "runaway" OV conditions are ball face lies with no documented cases. Yes ND alternators can fail, but they are mild or benign failures. Despite sensational comments like "smoke from your panel" or a B&C sales pitch, "On a dark stormy night your panel goes dark", internally regulated alternators are extremely reliable and safe, provide you have adequate backup, wire and operate them appropriately.

Crow Bars needlessly damage ND alternators, which are NOT designed to use them. To use a "crow bar" with an I-VR alternator, you ALSO need to add a circuit breaker and a big (master sized) relay on the output lead of the alternator (called B-lead). THIS is a lot of extra STUFF, cost and WEIGHT you are adding to an alternator that has internal OV PROTECTION. IT IS NOT NEEDED.

OK you have a crow bar on your ND alternator: "OV relay" on B-lead gets power thru a CB and crow bar attaches to the CB. If an OV is detected the crow bar SHORTS to GROUND! :eek:, POPPING the CB, cutting the power to the relay which than opens the relay (creating a big spark). OK it is all good if you had a real OV, but the problem is the CROW BAR has a nuisance trips or faults trips. This happens while the alternator is running, under load (high output). The abrupt cut of the b-lead (output) causes a huge voltage spike or LOAD DUMP. This will FRY the alternator. It has happened many times.

Hear are the facts and two guiding principals of safe alternator operations:
1) Do not run the alternator unless connected to a battery
2) Do not short or cause arcs in the wiring of the alternator.

THE CROW BAR GOES AGAINST BOTH OF THE ABOVE: 1) cuts battery from alternator, 2) Creates a large arc (internal to relay). While the crow bar shorts, it opens the relay.

Here is my suggestion:
1-Wire the NipponDenso alternator as in the application it's designed for. I HIGHLY recommend you wire in the warning light, and the remote voltage sense. The warning light is an important feature and Van ignores this. USE it. Why not? Also use the remote voltage sense by connecting direct to the battery. Van suggests you tie the IGN wire and remote sense together, which is OK, but to get the best performance from the alternator use it. Not all ND alternators have this function, but if it does why not use it. (VAN SUGGESTS A SIMPLE WIRING OF THE ALTERNATOR WHERE THE WARNING LIGHT AND REMOTE VOLTAGE SENSE ARE NOT USED. It will work this way, but recommend using the warning light at least, see ref below.)

2-Operate the alternator as it was meant in the application it was designed for (CAR). DO NOT MANUALLY TURN IT ON AND OFF THRU THE IGN WIRE POWER LEAD. The way the alternator should be used is, BEFORE engine start apply power top the IGN lead (with the master BATT switch). AFTER engine shut down turn the IGN lead off (with the BATT master). Builders are doing weird things like starting the engine with the alternator off and turning the alternator on manually after the engine is turning the alternator. This is not how it works in a car and not the intent of the IGN wire. The IGN wire comes on with the master and off with the master. If you have a problem and shut the alternative down you can turn it off then. HOWEVER the IGN wire cannot be used or trusted to shut the alternator down for a non-normal condition. (SEE NEXT PAR, item 3)


3-BIG MIS-CONCEPTION, The IGN wire is NOT a "Field Wire". The IGN wire is a Come alive or Go to sleep wire for VR power. That is it. Now some people will tell you that IF (and that's a big IF) the VR goes crazy (for a very rare and unlikely reason) you would have NO control. In this scenario the IGN wire will NOT turn the alternator OFF. This is TRUE. So how do you control an OV condition? THERE IS A SIMPLE SOLUTION: IT IS CRITICAL THAT YOU PUT A CIRCUIT BREAKER ON THE B-LEAD (alternator output), MOUNTED IN THE PANEL YOU CAN PULL. Think of it as a manual crow bar. IF for any reason the alternator is not stable or working properly you can reach over and pull the alternator's OUTPUT CB and ISOLATE the alternator positively from the aircraft. Alternator problems have signs well before a super NOVA. Have good gauges and Hi/Lo warning lights. Don't rely on the IGN wire to control the alternator. (I know it's popular to use FUSES you cannot access or replace in flight, but this concept is NOT compatible with I-VR alternators, at least use a CB for the b-lead.)

4-If you have an all-electric airplane, electric depended engine (electronic ignition / fuel injection), full EFIS panel, heated pitot and all the lights-bells-N-whistles, DONT install a 35-amp alternator. Vans alternator is rated at 60 amps, BUT it may not be big enough. It really is a 55-amp alternator. IT IS GOOD PRACTICE NOT to load the alternator continuously over 1/2 to 2/3rds of rated power. Most can live with this. However if you need more, ND has some nice alternators that put out 80 to 90 amps that are not much larger and will fit just fine. Heat kills ANY alternator.

5-PROVIDE COOLING AIR TO THE BACK OF THE ALTERNATOR. ND alternates have efficient internal dual fans and shield. However the max ambient temp is a little over 250F. Try to provide air and a heat shield between exhaust may not be a bad idea. The radiant heat from a 1400F exhaust pipe a foot away is not helping. If you keep it cool and don't over tax it the alternator will last to TBO, easily.

6- IT'S A BIG LIE THAT I-VR ARE PRONE TO SERIOUS FAILURE. I researched this and found stories of OV where just that STORIES. OV stories are left over from the OLD external VR alternators in Cessna's & Pipers. These aircraft are using 1950's technology and did have OV problems. Old VR's had mechanical relays to control voltage and no OV protection. THEREFORE THEY NEEDED AN OV MODULE ADD-ON LIKE. Many old timers think I-VR are based on this technology. FACT, an internal VR has an IC chip, with both analog and digital function, using 100's if not a few 1000 equivalent transistors. External VR's JUST regulate voltage and don't have the sophistication of INTERNAL VR's. Most E-VR's JUST regulate voltage, that's it and nothing more. A typical external VR (like the B&C unit) has 2 or 3 transistors and just a handful of other components. In fact the voltage reference in these plan external VR's use a simple zener diode reference scheme. Advanced I-VR have a much more stable voltage reference incorporated in the IC chip. There are modern external VR's, but the one B&C sells is not one of them.

WHY are all modern alternators in cars equipped with I-VR? Don't cars have expensive on-board computers and sensitive sensors (airbags) that need OV protection? Yes. That's why auto alternators have good OV protection. LOOK :eek: I checked the NATIONAL HIGHWAY SAFETY FOUNDATION database. This tracks all automotive related safety issues: Consumer complaints, Service Bulletins, Recalls, accidents related to vehicle defects. THERE HAVE BEEN NO COMPLAINTS AGAINST the alternator Van sells. This is not true of many other brands of alternators, which do have problems, but in general the ND alternator BRAND is the cream of the crop. The alternator Van sells is common in late 80's early 90's Suzuki and Geo cars. Variations of this model are found is 100's of thousands of cars and industrial equipment (forklifts, tractors) all over the world. These are going 24/7 all year round with great reliability. Some ND alternators have over 8-10 years of trouble free service in homebuilt planes. My two Acuras have a combined total of 400,000 miles and 25+ years of service, both have ND alternators still going strong.

Small Suzuki and Geo alternators are not made new anymore by ND, because today's cars need more power, even a Geo. However the new high power ND models are just larger variations of the smaller units. This leads to a point about rebuilds that some may not know. Not all rebuild alternators are the same. Pick your supplier carefully. I don't know who Van uses but you can get all new units made with after market parts. Not all rebuilds use genuine ND parts. Many aftermarket manufactures make rebuild parts. Good bad or indifferent it is something to think about.

I have checked many of the OV STORIES that I-VR allegedly had. They usually go like this: "I have a friend, and he knows some one who had an over voltage in his ND alternator in his Cessna 172." Well there are no ND alternators in factory planes. Tracking down the facts, they have nothing to do with a ND alternator or over voltage.

LEAVE THE CROW BAR OFF AS VAN SUGGEST.

George

https://vansairforce.net/community/showthread.php?t=4089
 
You are kidding right

Plenty of overvoltage protection, my voltmeter.

No, he is not kidding. And we're not talking about an overcharge rate, like 16V. Quite a few builders are moving to lithium iron phosphate batteries, and we've seen some melt because an alternator overvoltage blew right through the battery management system at 60+ volts.
 
No, he is not kidding. And we're not talking about an overcharge rate, like 16V. Quite a few builders are moving to lithium iron phosphate batteries, and we've seen some melt because an alternator overvoltage blew right through the battery management system at 60+ volts.

You have my attention, can you share the reports, would like to learn more about the overvoltages, what caused them?
 
That connector wont work on the Denso I posted a link to, there are different Denso connectors. The Denso I posted in this thread is the model B&C buys and converts to the L-40, I posted a link to the correct connector with harness, or you can get a connector from autozone with a shorter harness, but the one B&C sells for 17 bucks comes with aviation wire and a 3 or 4 foot long harness. I have the Denso alternator and B&C install kit and field harness in my basement, bought one for another plane after having good experience with my first one, I will go look at the field harness length and post the length

here is the Alternator and B&C L-40 harness

Thats about 10 feet of wire with the B&C $17. harness

Thats under $150. total for alternator and harness, the mount kit B&C sells will add another 100 or so if you need that

I was not responding to you. You are correct, not alternators are alike one should state what model, serial number and manufacturer before a reliable answer can be provided. I assumed, but will be sure it does not happen again.:D
 
I was not responding to you. You are correct, not alternators are alike one should state what model, serial number and manufacturer before a reliable answer can be provided. I assumed, but will be sure it does not happen again.:D


I agree with you that way we would have known for sure. He asked the question right after my post about the Denso that I posted a link to, so thought he was referring to that Denso, but I may be rong :)
 

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No, he is not kidding. And we're not talking about an overcharge rate, like 16V. Quite a few builders are moving to lithium iron phosphate batteries, and we've seen some melt because an alternator overvoltage blew right through the battery management system at 60+ volts.

I think it would benefit everyone if you shared the details of the overvoltage faults, is there a place here in the forum dedicated to this discussion? I have tried to rationalize changing to the lighter newer batteries but as good as AGM batteries are I wont switch to save 15 pounds, but an overvolting alternator could damage am AGM battery too, not just the lith iron batteries, so it would be great to learn more of these alternators that overvolted and melted the batteries. My Denso with the internal regulator has worked perfect over the last 7 years, my other plane with external regulated alternator quit working but was a fault of my own, the regulator was bad and during troubleshooting I full fielded the alternator for about a second by bypassing the broke regulator, thats the only time I have ever witnessed an overvoltage of an alternator and it was on purpose.
 
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I think it would benefit everyone if you shared the details of the overvoltage faults, is there a place here in the forum dedicated to this discussion? I have tried to rationalize changing to the lighter newer batteries but as good as AGM batteries are I wont switch to save 15 pounds, but an overvolting alternator could damage am AGM battery too, not just the lith iron batteries, so it would be great to learn more of these alternators that overvolted and melted the batteries. My Denso with the internal regulator has worked perfect over the last 7 years, my other plane with external regulated alternator quit working but was a fault of my own, the regulator was bad and during troubleshooting I full fielded the alternator for about a second by bypassing the broke regulator, thats the only time I have ever witnessed an overvoltage of an alternator and it was on purpose.

There are a lot of articles on overvoltage events both on VAF and Aeroelectric. It's something you don't want to have, and some protection from OV is a good thing. Several ways to deal with it.

https://www.google.com/search?ie=&o...=aeroelectric.com&sitesearch=aeroelectric.com

https://www.google.com/search?q=overvoltage+site:vansairforce.*
 
I think it would benefit everyone if you shared the details of the overvoltage faults, is there a place here in the forum dedicated to this discussion? I have tried to rationalize changing to the lighter newer batteries but as good as AGM batteries are I wont switch to save 15 pounds, but an overvolting alternator could damage am AGM battery too, not just the lith iron batteries, so it would be great to learn more of these alternators that overvolted and melted the batteries. My Denso with the internal regulator has worked perfect over the last 7 years, my other plane with external regulated alternator quit working but was a fault of my own, the regulator was bad and during troubleshooting I full fielded the alternator for about a second by bypassing the broke regulator, thats the only time I have ever witnessed an overvoltage of an alternator and it was on purpose.

That is the classic failure. All VR's (int or ext) are just microprocessors (used to be relays years ago) that read the ign input voltage and adjust the Field output current in order to force the alternator to reach a target voltage. If that microprocessor goes crazy it can apply to much current to the field and voltage climbs. Lets say it goes to 50 volts. At low current demand situations, this can occur in miliseconds. By the time you get the alarm, process and pull the breaker, all the damage is done. This is why folks use processor based OV controllers that pop the field breaker at around 16 volts. The OV can respond in miliseconds, as the voltage is ramping up. Pilots cannot do this. I made one via the schematic the Bob Knukles released for about $8 in parts. Cheap insurance and mandatory IMHO if using Lipo batteries. However, to integrate these into internal VR alternators is hard, excluding the ones like PP, that have a wire for turning them on or off. Instead, the OV module will pull power from a relay the connects the B lead to the alt, achieving the same result.
 
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It would be nice if somebody would post these meltdowns that have happened that's what I'm interested in reading about. The voltage regulator problem I had was caused by the mechanic grounding the main bus took out the voltage regulator. The modern Denso alternators they're good quality if you get the actual Denso version and not a China knockoff, I've never heard of one causing any issues at all, I know a lot of people flying with them. Imagine most issues with the VR are pilot-related wiring, or companies like PP purchasing Denso alternators and altering a product that was good quality strait from Denso. Again it would be nice to see the meltdowns Dan mentioned posted here so we could see why the happened.
 
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