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Charging System Health

Toobuilder

Well Known Member
Seems like we read an awful lot about alternator issues on this forum. I’m wondering why we seem to suffer disproportionately with these issues compared to the rest of the motorsports/industrial world? After all, when was the last time you had the alternator in your car go rogue and fry the computer? There has been a lot of attention given to OV crowbar protection, fuses, alternator shutdown schemes, etc, but shouldn’t we also focus on what can we do to minimize the frequency of failure in the first place?

I’m no expert, but it seems we are turning these units much higher than needed. Reading suggests that the output curve flattens out at around 6000 RPM, so if we take the typical 3.25 overdrive ratio of the large Lycoming pulley (9.75/3.0), we see we are spinning the alternator at almost 8800 RPM at takeoff (and maybe cruise for you FP guys).

2vwii49.jpg


To that end, I’ve added a 4.5 inch pulley to my alternator to slow it down. The resulting 2.16 ratio gives me a nice 5850 at takeoff and a comfortable 4750 at cruise.
Will it work? Only testing will tell. But I refuse to accept the dismal record of electrical systems installed in aircraft as “normal”. Alternator technology was figured out decades ago and there have been billions of hours racked up with what I suspect is a very acceptable MTBF rate. There MUST be something we are doing wrong. Off the top of my head, I suspect we could;

Slow the RPM (big pulley)
Cool the regulator (blast tube)
Proper teminations (General Practices)

Anybody have any other hints, tips, speculation?

BTW, the reason I picked the 4.5 inch pulley was simply a matter of availability. It was $29 bucks at Summit Racing so worth the experiment. Given a choice I would have gone a touch smaller.
 
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Interesting

I had no idea airplanes were spinning the altenators so fast. In my experience, what kills electronics is the on/off/on switching transients. If the rectifiers and the voltage control electronics are seeing much higher switching frequencies, then the expectations are the switching voltage transients are much higher. I think these switching transients are what kills the electronic parts.

There might be an old wives tale that spinning the altenator faster is better and gives more power. I don’t think this is true with modern altenators as long as the minimum speed is reached and the field current is sufficient. Higher speed might help to charge the battery during idle, but if it causes higher stress and failures during cruise conditions, I would think it is not worthwhile.

JMHO. YMMV
 
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Perhaps its the RPM situation, there have been multiple reports of poor terminations/connections/corrosion etc. causing issues for sure and well documented. Putting blast tubes to help cool the regulators is perhaps inconclusive from reading the posts on the subject, but sure can't hurt. Some of the alternators on vehicles are hung low and are subject to water splashing in the rain and road dirt and debris, some are mounted up in the "V" of the engine and behind the radiator fan blowing 180 degree air on them, yet as a whole they are very reliable and go many years and thousands of miles trouble free. I've never heard of an automotive installation that took out the electronics, not to say there have been none, but it is so rare as to never or rarely hear of it. As a general rule aviation is using purpose built or specially modified alternators. Some manufacturers seem to have significantly less issues than others, and that may be a quality issue, but across the board aviation units seem to be short lived compared to automotive fleet. The ND style alternators used in the experimental installations seem particularly short lived if they have an internal regulator.

So how do we get the reliability of the automotive installations? Perhaps someone much smarter than me can give us the answer.
 
Yet those same ND alternators are extremely long lived in auto applications.
If you're going to analyze, use all the data you can get, and do logical analysis.

High rpm will wear bearings & brushes faster, but it won't cause an overvoltage event. Remember, the alternator itself is just iron, aluminum and copper. Without the electronics in the regulator, it won't make any voltage at all.

Brutal vibrations and resonances from un-analyzed mounting systems and flat four engines with 5" diameter pistons, those and other things are quite different from the automotive world. There are probably more hours of *testing* in an automotive alternator \ regulator mounting system than most of us will put on an engine.
 
I tried to fry the internal regulator with a heat gun just to see if there was anything to it. The regulator kept working even after the potting material surrounding it started to melt. Now, this isn't prolonged heat, just short term exposure to extreme heat.
Once I started leaving the alternator field switch "on" during shut down, instead of shutting it off, I haven't had a failure since.
This has been covered in quite a few discussions here for many years, but to your point, they are still failing disproportionally.
 
rotor balance

Wouldn't changing the pulley change the rotor balance?
At 6,000rpm you are still looking at significant vibration if you have a rotor imbalance, and it might eventually break the armature wires off, which seems to be a common failure mode.
Does anyone know how do they balance these things?
 
Once I started leaving the alternator field switch "on" during shut down, instead of shutting it off, I haven't had a failure since.
This has been covered in quite a few discussions here for many years, but to your point, they are still failing disproportionally.

That is another (significant) data point in doing analysis. Cars don't do it, but many pilots do.
 
My 70A Denso internally regulated alternator (external field terminal) puts out 45 amps at 2000 rotor rpm, 65 at 3000 and 70 at 4000. I have a larger pulley on mine, no issues charging with the usual electrical loads on at a 1200 rpm idle (geared engine).

No point in turning these at 8000+ rpm in cruise, just wearing the brushes, shaft and bearings out sooner and increasing the internal vibration for zero gain in output which essentially peaks at 6000 rpm.

Heat possibly reduces life but most auto installations bathe the alternator almost continuously in 160-180F rad air. Doubt if the typical aircraft installation is worse than that.

Engine vibration maybe but the regulators are all potted, components can't move under vibration.

I believe the switching the field theory is no cause for failure. I've switched mine off and on while running many hundreds of times now (lots of .5 to 1 hour flights in the last 5 years at least).

With at least 20,000 hours driving ND IR alternators with zero regulator or OV events and my immediate family driving another 60,000 hours + also with no failures, one can only conclude something is different on our aircraft to have so many failures with such few hours.

Someone posted a couple months back saying auto alternators didn't spin as fast typically. I disagree. I measured drive and alternator pulleys on a bunch of cars around here. The pulley ratios vary from about 3- 4 to 1. So a 3000 rpm cruise on the highway gives you 9,000 to 12,000 rpm and around 20,000 at redline. Yet I've seen many ND alternators go 5000+ hours until the brushes or bearings finally wear out.

Cars need these high ratios because they have to charge at a 650 rpm idle with heater fan, heated seats, heated window, lights and all the other loads on- much higher idle loads than most light aircraft see at idle.
 
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Pulley size and alternator speed was the talk around 1999 2000 when a 4 inch aftermarket pulley was offered to us by one of the (can't remember who) experimental parts and tool supplier.

Cowling clearance was a problem with some RV's. Older E2d's like found on Mid 70's Warriors had a much smaller flywheel pulley and was closer to the ratio of auto's at that time.

Here is where you can get a 4 inch pulley..... http://www.jegs.com/i/Powermaster/713/182/10002/-1
 
Pulley size and alternator speed was the talk around 1999 2000 when a 4 inch aftermarket pulley was offered to us by one of the (can't remember who) experimental parts and tool supplier.

Cowling clearance was a problem with some RV's. Older E2d's like found on Mid 70's Warriors had a much smaller flywheel pulley and was closer to the ratio of auto's at that time.

Here is where you can get a 4 inch pulley..... http://www.jegs.com/i/Powermaster/713/182/10002/-1

Cowl clearance can be an issue, I agree. I made a mount that really tucks it in close to the case, but I still may have issues, we'll see.

Here is the version I started with:

https://www.summitracing.com/parts/sum-g3969/overview/

Also note that like the Jeg's version, it may need a bushing to fir the shaft size of the ND. I machined a press fir bushing in mine and reamed it to final size.

Also noteworthy is the fact that the Summit version (and I presume the Jegs counterpart) are "deep groove"... This means that the belt sits about .250 deep. Though the OD is 4.00 inches, the "effective" OD is 3.5. I machined off the extraneous material and now have a flush belt and 3.5 OD.
 
Wouldn't changing the pulley change the rotor balance?..

In automotive applications the pulley is often removed off the core for use on the new. They are often not indexed either, so as long as the pulley is neutrally balanced, there should be no issue.
 
4"

I went to a 4" pulley about a year ago to slow down Alt speed I used a program to figure speed of Alt at take off and cruise mine has about 1/8 clearance between pulleys and no cowl issues with SJ cowling.I figured it would extend life of ALt by slowing it down on take off.After installing 4" pulley I'm experiencing a little vibration in the 1200 to 1500 range anyone have idea to balance the assembled Alt with new pulley as one unit.
Bob
 
Once I started leaving the alternator field switch "on" during shut down, instead of shutting it off, I haven't had a failure since.
This has been covered in quite a few discussions here for many years, but to your point, they are still failing disproportionally.

The only way I can shut down the alternator in my RV-6 is turning off the master, there is no alternator switch. I have a 5A breaker in the field circuit but it isn't the switchable type. The alternator has been "on" all the time since the plane started flying in 1999.

I use a 35A ND alternator (Honda Civic) with a Ford regulator and Nuckols OV module. The pulley is what comes on the alternator when it is plucked from the aviation shelf at a local auto parts store.
 
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If you are using an automotive IR Denso alternator, be sure you have a separate, external field terminal. Not being able to turn the thing off could lead to some expensive damage.

denso1

 
I think we are generally all in agreement that switching the field, slowing RPM, and blast cooling the diodes are probably not "the" fix for the short lifespan of some alternators. I do think they are good practice and at the least, don't hurt.

All that said - what are we missing? As Ross points out, car alternators are running in a very hot environment, often doused in water, mud, debris and generally receive zero maintenance. And when they do fail, 99 times out of 100 they just stop charging the battery. I would love to get to that level of comfort with my electrical system.
 
my take

I think what is killing the alternators are the two things that are different between cars and planes. First is the RPM, I think the RPM is too high on airplanes. Second, most cars have the battery really close to the alternator. This keeps the inductance down from the alternator to the battery. Put these two together, and the electrical noise imposed on the rectifiers and solid state regulators in an airplane is probably much more severe. I would bet the internal electrical transients on the alternator parts are much higher on an airplane.

The talk of heat, vibration, etc are all mechanical things, but what we seem to be dealing with is electrical death.

We all need data. I would be curious if there is a correlation between alternator death, distance of battery away from alternator, and alt speed.
 
I think what is killing the alternators are the two things that are different between cars and planes. First is the RPM, I think the RPM is too high on airplanes. Second, most cars have the battery really close to the alternator. This keeps the inductance down from the alternator to the battery. Put these two together, and the electrical noise imposed on the rectifiers and solid state regulators in an airplane is probably much more severe. I would bet the internal electrical transients on the alternator parts are much higher on an airplane.

The talk of heat, vibration, etc are all mechanical things, but what we seem to be dealing with is electrical death.

We all need data. I would be curious if there is a correlation between alternator death, distance of battery away from alternator, and alt speed.

Read my post 10 where I measured the pulley sizes. No way the average Lycoming alternator installation sees anywhere near the rpm that cars do.

Tons of stuff being turned on and off in cars with far higher current draws than our RVs. Lots of cars like BMWs have the battery in the trunk, don't see regulator failures there. I've been working on cars with IR alternators for 30+ years, including a repair shop where most customers had Toyotas and Denso alternators. Never seen a OV failure in all that time in a car. Tens of thousands of hours.

I don't know what the cause is but I'm skeptical of these theories.
 
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I think what is killing the alternators are the two things that are different between cars and planes. First is the RPM, I think the RPM is too high on airplanes. Second, most cars have the battery really close to the alternator. This keeps the inductance down from the alternator to the battery. Put these two together, and the electrical noise imposed on the rectifiers and solid state regulators in an airplane is probably much more severe. I would bet the internal electrical transients on the alternator parts are much higher on an airplane.

The talk of heat, vibration, etc are all mechanical things, but what we seem to be dealing with is electrical death.

We all need data. I would be curious if there is a correlation between alternator death, distance of battery away from alternator, and alt speed.

I've been watching folk's reports of alternator failures here on VAF (and on other forums) for a dozen years, and for internally regulated automotive alternatOrs, the two biggest killers seem to be lack of blast cooling to the regulator, and cycling the alternator with the rotor turning. Both seem to kill the regulator. Use a blast tube, and keep the field energized, and most problems seem to go away for a thousand hours or so (when a bearing gives up due to poor alignment....).
 
One thing to consider if purchasing a "remanufactured" alternator is the possibility of having some planned failures built in. I know of some such alternators showing up in the box without the inner dust seal on the front bearing. As in, someone pried the seal off one side of the bearing for some reason. Makes sense if you consider that the remanufacturing process is little more than new brushes and a coat of paint. Early failure for a simple bearing change means money in the pocket for the "rebuild shop".
 
To address the 'cycling' issue: Breaking the feed to the field winding while operating shouldn't be an issue. But there was a time when guys running IR alternators were actually turning off the master while in flight, which is a total load dump, unlike a car, where even a major consumer is still only part of the load. Theory is that because the regulator isn't a perfectly instantaneous device, the suddenly unloaded B lead output would rise so fast and far that voltage would get above the 'breakdown voltage' of the semiconductors (transistors, diodes, ICs, etc) in the regulator. That kills the semiconductors, killing the regulator. Been there, done that, got the T shirt: Old RV-4 (not my build) with a switchable CB in the B-lead output. Bump that CB switch: load dump; dead alternator.

Newer alternators that are advertised as having load dump immunity are likely being built with much faster semiconductors with much higher breakdown voltage.
 
The only time I shut off the field is when I am playing with the EFIS in the hangar...... the field has a noticeable draw and will heat a standing alternator.
 
As I said, I've switched my ND field on after start up and off before shutdown on every flight- hundreds of times. No reg or OV failure.

As I also said, most car alternators live in a 160 to 180F+ environment their whole lives exposed the air coming off the rad yet last thousands of hours and almost never have regulator or OV failures. Don't see how they would get that hot in an airplane since they are not in the hot, cooling air stream.

As part of our testing for years, we've done numerous load dump tests with our ECUs pulling off the battery cable with the engine running at 1000-2500 rpm, never killed an alternator or ECU yet.

RPM, heat and field switching theories don't add up to me causing the failures. Seems like engine vibration is the remaining variable. Lycomings are paint shakers compared to modern auto engines, you don't feel it so badly in the cockpit due to the thick, soft engine mount rubbers.

There are likely many variables in the design and components used within the ND family of alternators, perhaps I've been lucky with the ones I've owned. driven and flown for 3 decades. The ones I've used most are 1985-87 vintage 70 amps models usually fitted to Corollas.
 
As I said, I've switched my ND field on after start up and off before shutdown on every flight- hundreds of times. No reg or OV failure.

As I also said, most car alternators live in a 160 to 180F+ environment their whole lives exposed the air coming off the rad yet last thousands of hours and almost never have regulator or OV failures. Don't see how they would get that hot in an airplane since they are not in the hot, cooling air stream.

As part of our testing for years, we've done numerous load dump tests with our ECUs pulling off the battery cable with the engine running at 1000-2500 rpm, never killed an alternator or ECU yet.

RPM, heat and field switching theories don't add up to me causing the failures. Seems like engine vibration is the remaining variable. Lycomings are paint shakers compared to modern auto engines, you don't feel it so badly in the cockpit due to the thick, soft engine mount rubbers.

There are likely many variables in the design and components used within the ND family of alternators, perhaps I've been lucky with the ones I've owned. driven and flown for 3 decades. The ones I've used most are 1985-87 vintage 70 amps models usually fitted to Corollas.

All I can say Ross is that you and I have had different experiences - but when I went to blast tubes on the internal regulators (which costs nothing but a short piece of hose) and stopped switching them while the engine is running (and there is no real reason to switch them (and it removes a couple of checklist steps), my ND alternator failure rate went to essentially zero.

Folks can choose what they want to do.
 
Seems to me like many people are using auto alternator models with no external field terminal which just isn't smart in my view.

Both PP and B&C advertise their models have OV protection so those users theoretically shouldn't have to worry with Lithium batteries on board.

PP says that the direction of rotation is different on auto and aircraft engines and that the auto fans may not move enough air as a consequence. Maybe, but in cars, they are just moving hot air around. It is something I had not considered before though.

Seems like the only way to know if temperature is higher in aircraft would be to stick some thermistors or thermocouples on the alternators and test in real life. I'd be willing to test some of mine.

Has anyone here experienced an OV condition with a PP or B&C alternator?
 
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All I can say Ross is that you and I have had different experiences - but when I went to blast tubes on the internal regulators (which costs nothing but a short piece of hose) and stopped switching them while the engine is running (and there is no real reason to switch them (and it removes a couple of checklist steps), my ND alternator failure rate went to essentially zero.

Folks can choose what they want to do.

Agreed, blast tube can't hurt as long as you're VFR.
 
Why?

Agreed, blast tube can't hurt as long as you're VFR.

Interesting statement considering Bonanza’s and presumably some other Continental powered aircraft have their alternators mounted in the right cowl air inlet...

Skylor
 
Heat is the bane of all electronics. Adding a blast tube can't hurt and as mentioned, some have seen better results by doing so. In the early days many of us experimented with automotive alternators, without a lot of success. That being said, automotive alternators have come a long ways and have made many improvements. Usually a product that is designed for the particular application has a tendency to work better and last longer. Not always true, for sure, but typically if good engineering is used and the environmental conditions are understood, the results are better.

I specifically asked B&C if turning off the alternator field into flight would cause any harm, and I was told no. I even got the "look" when I asked the question. Think about this---- the only way to test if your backup alternator is working is to fail the primary alternator. I peform this test about twice per month when flying, and have done so for a couple of thousand hours, with no harm.

Vic
 
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Interesting statement considering Bonanza?s and presumably some other Continental powered aircraft have their alternators mounted in the right cowl air inlet...

Skylor

I don't think those have the brush area open to the breeze.
 
Micheal just for comparison, the less common 7.5? Lycoming pulley size with 3? alternator gives a 2.5:1 ratio. Compare that to your 2.15 ratio.
My only concern reading these post is fan speed needed to flow enough ?coolant? thru the alternator. It may be you?ll get the amps needed, but at higher temps than with the 3? pulley, defeating your original reliability objective. This is just speculation though.
Tim Andres
 
Ok, I slapped a thermistor on the case of my BMW alternator, after about an hour of driving it reached 158F with the ambient temp around 50F.

I hope to go flying tomorrow morning and measure the temps on my Denso alternator but this is on a Subaru, not a Lycoming so not really valid, just another data point.
 
What temperature exactly?

Ok, I slapped a thermistor on the case of my BMW alternator, after about an hour of driving it reached 158F with the ambient temp around 50F.

I hope to go flying tomorrow morning and measure the temps on my Denso alternator but this is on a Subaru, not a Lycoming so not really valid, just another data point.

I am not flying yet and just today made a list of FWF temperatures to be measured. I can add to the database if you like during phase I. I have a PP 60A. Where would you like the thermocouple mounted? Buried in the end turns? On the housing at a bearing? On the stator laminations?

Most OEMs leave the development to the alternator supplier, but acquire data from OEM testing. Maybe we should work with ND?
 
I am not flying yet and just today made a list of FWF temperatures to be measured. I can add to the database if you like during phase I. I have a PP 60A. Where would you like the thermocouple mounted? Buried in the end turns? On the housing at a bearing? On the stator laminations?

Most OEMs leave the development to the alternator supplier, but acquire data from OEM testing. Maybe we should work with ND?

I did a quick and dirty and just tied the thermistor to the rear casing. I'd guess that most heating on cars is coming from being bathed in rad air although at high amps, internally, things could get even hotter than that inside.

If you're adding data lines, would be interesting to place some more probes inside the alternator a bit deeper.

I'm not sure ND would approve of us using their products in aircraft...
 
Are there any statistics (data) out there indicating a belt driven alternator is any more or less reliable than its gear driven counter part?

For example, take a B&C gear driven 40 amp alternator compared to the reliability of a B&C belt driven 40 amp alternator. What factor(s) makes one more or less reliable than the other.

1. Vibration
2. Temperature
3. Bearing stress/wear
4. Time under load

I know of one electrically dependent RV-4 out there running only one, gear driven alternator.

In speaking with B&C about the idea of going to only one gear driven alternator, I was told that belt driven alternators tend to be more reliable. This stopped me from going down this path.
 
Just going through the posts in the big alternator thread. Interesting one case, stock small auto ND IR, 2300 hours, no blast tube, no failures. That's a LOT longer than most of the PP and B&C users. I doubt if there is anything systemically wrong with the proper ND IR alternator if this example lasted that long.

I think reliability may have more to do with WHICH ND alternator you run. One shouldn't assume they're all alike inside. I think many people have simply jumped on the bandwagon and used the same one as others which has not turned out to be a good choice.

On the fan direction thing, most Hondas up to MY2000 turn counterclockwise so opposite to a Toyota.

After driving the BMW around more, I found the highest alternator temps occurred at low speeds to stopped. Once going, temps dropped down to below 130F.
 
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Let's be brutally honest. :)

My money is on it being more about which person installs it than which model they use; much like the alternative engine question. Many more ways to get it wrong if you don't have a single set of detailed instructions on how to do it right.
 
Let's be brutally honest. :)

My money is on it being more about which person installs it than which model they use; much like the alternative engine question. Many more ways to get it wrong if you don't have a single set of detailed instructions on how to do it right.

The wires and belts are hooked up. More to do with the hardware IMO. Are people hooking them up wrong, mounting them wrong?

We should be finding out which alternator models don't break and which do. Build from that point if there is a concencus from the data.

A successful alternative engine installation is a far more complex task than an alternator installation. Many more things to go wrong. I don't see the parallel there really.
 
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The wires and belts are hooked up. More to do with the hardware IMO. Are people hooking them up wrong, mounting them wrong?

We should be finding out which alternator models don't break and which do. Build from that point if there is a concencus from the data.

A successful alternative engine installation is a far more complex task than an alternator installation. Many more things to go wrong. I don't see the parallel there really.

I have seen many bad installations Ross - poor, butchered "let's make it fit" brackets that have poor alignment have been the biggest problem. I've see folks use incorrect hardware, which leads to loose mechanical installation. Wiring is less often a problem. And I know from previous posts that you think blast tubes are inconsequential, but I have seen many installations go from problematic to perfect with the simple addition of a blast tube pointed directly at the regulator. Even airplane's flown regularly in the rain.

Back when I spent a lot of years in the Grumman world, people reported lots of electrical failures when they got their external regulators wet in the rain. The internal refs seem to be much more waterproof.
 
I have seen many bad installations Ross - poor, butchered "let's make it fit" brackets that have poor alignment have been the biggest problem. I've see folks use incorrect hardware, which leads to loose mechanical installation. Wiring is less often a problem. And I know from previous posts that you think blast tubes are inconsequential, but I have seen many installations go from problematic to perfect with the simple addition of a blast tube pointed directly at the regulator. Even airplane's flown regularly in the rain.

Back when I spent a lot of years in the Grumman world, people reported lots of electrical failures when they got their external regulators wet in the rain. The internal refs seem to be much more waterproof.

I can't see how a misaligned belt can cause a regulator failure. We're talking internal electrical failures here. Now if a bracket does not hold the alternator tightly and it's vibrating its guts out, that's different and hardly the fault of the alternator. That's like forgetting to tighten the rod bolts on a Lycoming, having the rods come out through the case and saying the Lycoming is a poor design. Blast tubes won't solve installation errors like that anyway. Blast tubes may indeed help regulator life if design temps are being exceeded so let's find out if that's the case.

The fact that two posters had stock IR ND alternators with no blast tubes running longer (in the one case, 2300 hours) than the PP and B&C posters shows that those alternators have no systemic design problems operating on a Lycoming engine. We need to find out what models they are running and any other details which might be significant. I've PM'd them for more info.

Let's not speculate on causes or solutions. Let's measure the temperatures on our installations, vibration levels if possible, document the exact models used, build a database and see if we can draw some valid conclusions based on science. I started the ball rolling and I invite others to participate and post their results. I unfortunately don't personally have a Lycoming installation to test on but I will get a temp sensor on my alternator and try to get a flight in here if the wind ever subsides. We will have access to a Lycoming RV on our field with SDS on it soon for testing. I'll try to get a temp probe on that alternator and gather some data.

Most automotive electronics are designed with components having at least a 125C continuous temperature rating (257F). Are we exceeding that in a typical Lycoming installation without blast tubes? That should be the first step in any analysis IMO. Too many people point to the IR as bad design feature in genuine ND alternators yet they have proven virtually bulletproof in the automotive world. The solution by PP and B&C was to take another regulator (sometimes of questionable reliability) and mount it externally. I'm not sure this is progress and it seems from the Reliability Poll here on VAF that in the case of PP especially, this has had the opposite effect on reliability.

Are people fitting genuine ND units? There are some lookalikes which certainly aren't, floating around out there. I know, I had one and it failed (no charge situation).

The "modern" IR ND alternator in the automotive environment almost never experiences a regulator or OV failure and these collectively have trillions of hours of operation and typically go 4000+ hours with no failures, so the question remains- what's different in the EXP aviation environment? Speculation won't answer that question. Seems like this would make for a great KP article. How about proposing that to Dan Horton?
 
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Actually Ross, the thread title is "Charging System Health", and it has included thoughts on electrical as well as mechanical issues. What kills electronics? Usually heat and vibration. Moisture if the electronics aren't sealed properly. And, of course, bad design. Since you have already said these regs work forever in automotive applications, its probably not bad design. Vibration can definitely come from poor mounting, loose mounts, worn bolts that allow vibration - coupled with poor alignment (which also kills bearings - I know, that's not the reg, but if your alternator dies, your alternator dies....). I know that while you don't fly behind a Lycoming, you still do a lot of testing with them, and have a lot of knowledge. The good thing is that you are very talented, and probably have outstanding installations - mechanically and electrically.

The truth is - as a Tech Counselor, I have seen many horrible installations. You might not have, but they are out there. And they can and do cause problems.

I agree with you that building a database of actual failures is a great idea. Without data, its all just guesses...right? So we can assume that since neither of us has hard data (I have decades of anecdotal instances, you admit that you don't have the data), its all just speculation. Fair enough.

Hope some folks have the time and equipment to collect some actual data - I don't right now - and we need it collected on real world installations. Otherwise, it simply isn't going to be very valid.
 
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My recollection may be foggy

...but I believe Bob N has documented in the 'Connection book that almost all replaement alternators are rebuilt in one of a few (maybe just one) facility in Mexico and then a brand slapped on the box. Unless one is buying new alternators out of the automotive supply chain, I suspect a Denso is nowadays the same as a NAPA or MOPAR or any other brand. Am I right?

Ross wrote, "Are people fitting genuine ND units?"
 
What worked for me

The Doll started life with a Van's automotive alternator and switching type regulator. That set up didn't last to the first conditional. The alternator stopped charging with less than 100 hours. Some very wise man told me about B&C alternators. I purchased their L-40 alternator, but did not purchase their LRC3-14 regulator. At the time it cost $228 dollars. (now $180) I thought I'd save that money. Then on a very cold morning I flew to Hicks airport to visit Jay Pratt and notice an over voltage of 18 volts. I shut off the field switch. That cheap switching regulator failed in the cold conditions. I was lucky that the only damage was a blown regulator in my RC Allen electric DG. That cost $400 dollars to repair. Some savings! I purchased the B&C LRC3-14 regulator and have had flawless performance ever since. That was 2001.... 16 years ago! My alternator is not even a concern for me!

The incident report published last week on VAF about the runaway internally regulated automotive style alternator should have made a impact on everyone using one of those. I only fear two things when flying....Midair collision and inflight fire.

I consider my investment in the B&C alternator and regulator well worth it.
I posted this off thread reply because the fix is already out there, and I think my 16 year data point might be interesting to some builders dealing with this alternator/regulator problem.

OBTW I turn on the battery and field switch before engine start, and turn them off after engine shutdown. Always have.
 
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...but I believe Bob N has documented in the 'Connection book that almost all replaement alternators are rebuilt in one of a few (maybe just one) facility in Mexico and then a brand slapped on the box. Unless one is buying new alternators out of the automotive supply chain, I suspect a Denso is nowadays the same as a NAPA or MOPAR or any other brand. Am I right?

Ross wrote, "Are people fitting genuine ND units?"

I guess if this is true and most RV builders are fitting rebuilt ND alternators, we have no idea what non-ND parts may be fitted and the OEM auto track record may have no bearing on reliability in RVs. This complicates collecting data unless we start disassembling the units to see what's inside them. They can all look pretty much the same from outside which means basically nothing.

I had not considered this aspect before. If the rebuilders are tossing the OEM ND regulators and installing junk brand X stuff, this could certainly explain the high failure rate we see in RVs. Might not be temperature or vibration at all.
 
The Doll started life with a Van's automotive alternator and switching type regulator. That set up didn't last to the first conditional. The alternator stopped charging with less than 100 hours. Some very wise man told me about B&C alternators. I purchased their L-40 alternator, but did not purchase their LRC3-14 regulator. At the time it cost $228 dollars. (now $180) I thought I'd save that money. Then on a very cold morning I flew to Hick to visit Jay Pratt and notice an over voltage of 18 volts and shut off the field. That cheap switching regulator failed in the cold conditions. I was lucky that the only damage was a blown regulator in my RC Allen electric DG. That cost $400 dollars to repair. Some savings! I purchased the B&C LRC3-14 regulator and have had flawless performance ever since. That was 2001.... 16 years ago! My alternator is not even a concern for me!

The incident report published last week on VAF about the runaway internally regulated automotive style alternator should have made a impact on everyone using one of those. I only fear two things when flying....Midair collision and inflight fire.

I consider my investment in the B&C alternator and regulator well worth it.
I posted this off thread reply because the fix is already out there, and I think my 16 year data point might be interesting to some builders dealing with this alternator/regulator problem.

OBTW I turn on the battery and field switch before engine start, and turn them off after engine shutdown. Always have.

In the poll, the B&C stuff showed much higher reliability than PP. Your experience continues to support that trend and is certainly food for thought to those suffering problems with other alternators.
 
The Doll started life with a Van's automotive alternator and switching type regulator. That set up didn't last to the first conditional. The alternator stopped charging with less than 100 hours...

I believe you. But the point is why did it fail? It certainly cant be based upon it's heritage as an "automotive" part, can it? After all, no auto OEM would allow that level of MTBF... They would be ruined financially with warranty costs and lost sales due to bad press. Despite the fact that cars can "...simply pull over to the side..." The automotive world has a significant stake in MTBF. And I'd opine that even our best examples of reliability from the "aviation" alternators would be wholly unacceptable for any reasonable car company.

For my own experiences, I sourced a greasy ND from a junkyard for my Hiperbipe as a core used for mockup. Then I decided to run it for the first flights... And it was still going strong 250 hours later when I sold the airplane and as far as I know it's still hanging in there. Additionally, I added a 70 amp IR, ND straight from NAPA auto parts for the Rocket, and it has provided flawless service for 300 hours in a wide range of temperatures and precipitation.

I also have little reason to doubt the claims that the specialty aviation alternator suppliers spend a bit more time reworking their (automotive based) products, but I'm not about to believe that such action is the difference between "acceptable" and "unacceptable". I have too much time operating automotive based products without failure to buy that sales pitch.
 
If you are using an automotive IR Denso alternator, be sure you have a separate, external field terminal. Not being able to turn the thing off could lead to some expensive damage.

denso1


Ross,
Do you have make and model for an IR Denso alternator with external field terminal?
TIA,
 
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