What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Charging System Health

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

Using that explicit term, I seriously doubt you will find one. You will find some that have a terminal that tells the regulator to turn on (and hopefully, off). You may find some with a terminal that supplies the only source of power to the regulator (what you want, for true control). But an alternator with an internal regulator and an external field terminal? Why would automotive mfgr build such an animal?
 
Using that explicit term, I seriously doubt you will find one. You will find some that have a terminal that tells the regulator to turn on (and hopefully, off). You may find some with a terminal that supplies the only source of power to the regulator (what you want, for true control). But an alternator with an internal regulator and an external field terminal? Why would automotive mfgr build such an animal?

Huh? I published photos on this thread of two such animals. ND built millions of these in the mid '80s to early '90s. As I said before, I've been flying one on my 6A for 14 years and when you cut field power, it stops charging.
 
Huh? I published photos on this thread of two such animals. ND built millions of these in the mid '80s to early '90s. As I said before, I've been flying one on my 6A for 14 years and when you cut field power, it stops charging.

Open it up and follow the lead from that terminal. A control signal to the regulator is not the same thing as a field terminal (which implies a direct connection to the field brushes).
 
Bottom one is the 70A one I'm flying with. Fits Toyota Corolla GTS '85-'87 as far as I know maybe others.

Top one is from East Coast Electric 2026. http://www.ecae.com/alt1.html

Ross, the 2026 "mini" is likely the ND with a 100mm OD stator, same as the PP 60A. This 2026 is listed at 55 A. I have seen some 70A "mini" alternators in the ND form factor, but have not been able to link it to a ND part number. Appreciate if you could supply a number - no rush.

On another note - Denso has a parts locator website. They list retail sellers of their factory reman alternators. They say they use all OE parts, bearings, brushes, etc. Using the ND part number, one can find them on eBay stating they are from Denso/ND reman factory. Only mentioned to confirm availability of a quality part.
 
Ross, the 2026 "mini" is likely the ND with a 100mm OD stator, same as the PP 60A. This 2026 is listed at 55 A. I have seen some 70A "mini" alternators in the ND form factor, but have not been able to link it to a ND part number. Appreciate if you could supply a number - no rush.

On another note - Denso has a parts locator website. They list retail sellers of their factory reman alternators. They say they use all OE parts, bearings, brushes, etc. Using the ND part number, one can find them on eBay stating they are from Denso/ND reman factory. Only mentioned to confirm availability of a quality part.

I have not personally used the 2026 but I think most Eggenfellner conversions were fitted with this one. I haven't heard of failure of one yet but I'll poll that group for interests sake.

I don't have a PN for the AE86 unit but could probably be found somewhere in a ND listing.

Interesting data on the Denso rebuilds. If true, I think that's where I'd be headed if I ever had a failure (but I never have on a genuine ND).
 
Last edited:
Ross,

To be clear, I love ND brand IR alternators, & I've used them for a couple of decades.

But my earlier post was intended to deal with 'positive control' of the alternator *when the regulator has actually failed causing an overvoltage event*.

If you follow the wires in the diagram you posted, you'll see that one end of the field winding is connected to the alternator's DC output, and the other (ground) end is controlled by the regulator. So the field always has DC available to power it. As long as the regulator's field control circuitry is intact and functioning properly, all is good and removing control voltage from the control terminal will shut down the alternator.

But what happens if the regulator actually fails & takes the alternator into runaway? If the transistors that supply a ground path for the field are shorted (not open; shorted), how will the control terminal shut down the alternator?
 
This alternator uses a ground type regulator setup so even if the reg transistors shorted, I believe pulling power from the field terminal would have to shut down the field and thus all alternator output. It would go OV until you intervened manually, but you could shut it down at least.
 
Last edited:
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.

Ross;
I had an engine conversion business until about 10 years ago. I put Subarus into VW's.

When I started reading this thread, I kind of knew why the auto alternators were failing. I have probably bought 20 starters, and another 20 alternators from NAPA, Pep Boys etc. Of the starters, maybe 15 or 20% were good. The rest I took back. The alternators maybe half were good, in the beginning. Usually the regulator died, or never worked. I think I had 3 over voltage, and the rest under voltage until they just died. I also had an SVX alternator rebuilt locally a couple of years ago. It lasted a couple of hours. The shop that rebuilt it covered it under warranty as it happened 2 days after I got it. They told me the regulators they get are junk, but that is all that is available.

For my business, I quickly stopped buying rebuilt, and just bought used ones from junkyards. I never got a bad used OEM alternator. Not one.

Most other charging issues were dirty/corroded/loose/all of the above/ connections, usually the grounds.
 
Ross;
I had an engine conversion business until about 10 years ago. I put Subarus into VW's.

When I started reading this thread, I kind of knew why the auto alternators were failing. I have probably bought 20 starters, and another 20 alternators from NAPA, Pep Boys etc. Of the starters, maybe 15 or 20% were good. The rest I took back. The alternators maybe half were good, in the beginning. Usually the regulator died, or never worked. I think I had 3 over voltage, and the rest under voltage until they just died. I also had an SVX alternator rebuilt locally a couple of years ago. It lasted a couple of hours. The shop that rebuilt it covered it under warranty as it happened 2 days after I got it. They told me the regulators they get are junk, but that is all that is available.

For my business, I quickly stopped buying rebuilt, and just bought used ones from junkyards. I never got a bad used OEM alternator. Not one.

Most other charging issues were dirty/corroded/loose/all of the above/ connections, usually the grounds.

Thanks for posting. That essentially mirrors my experiences over 3 decades of using these.
 
What can I expect from a $40 ND alternator that uses an external regulator? Mine is a Zeftronics with a built-in OVP.
 
The alternators were store brand rebuilds for Subarus. The starters were "Genuine Bosche Factory Rebuilds". Both were complete junk.
 
I found the Denso and Toyota OEM PNs for the GTS alternator:

210-0310 27060-16090
210-0312 27060-16050
 
Up flying today with the temp sensor probe installed inside the alternator case. Ambient was around 0C. Max alternator temp in flight was 41C. Temps climbed after landing with 52C seen, max was 63C about 7 minutes after shutdown. On a +35C day, it's doubtful my setup would see anything close to 100C in flight which is well short of the typical 125C temps auto electrics are designed for.

My alternator is at the rear of the engine, no blast tubes but sitting aft of the oil cooler. Max oil temp today was around 75C.

I invite others to post data from their Lycoming installations.
 
So now that we've established you can indeed shut down charging via the IG wire on the ND IR alternator in question, here's a little more info to answer Dan's questions:

In my RV6A, I have the IG terminal attached to my alternator "field" switch and the sense wire attached to the B terminal with about a 4 inch lead, just like the Toyota schematic. The light terminal is not connected.

From the test card on my alternator, the turn on point where the alternator starts charging is 531 rotor rpm. My pulley ratio is 1.57. Current output at 1400 engine rpm/ 2200 rotor rpm is 50 amps.

I have not tested shutdown at the typical 4500 rpm cruise rpms I fly at but clearly there is more than enough current being produced to keep the field energized at the rpm I did the test and video at. My thought, and I could be wrong, is that the stator outputs cannot be connected to the field windings in this alternator as the schematic I posted depicts. I await someone posting info confirming or denying that conclusion.

My Haynes manual specifies a 7.5 amp fuse on the IG wire. My notes show I have the same 7.5A fuse on my aircraft installation.

With regards to what's inside the alternator and where the terminals are attached and component layout, I'll leave it up to someone else here to get one and cut it open. Same goes on measuring some temps on a Lycoming installation. My testing so far shows the highest temps occur at idle and after hot shutdown where there is little or no cooling air circulating.

You can buy genuine Denso alternators here: https://www.densoproducts.com/Automotive-Alternators-c245.aspx

These are rebuilds using only OE Denso parts. I think the prices are quite reasonable.

Official Denso parts site here: http://densoautoparts.com/why-denso.aspx

A few more thoughts: The auto OEMs today generally have far stricter standards for component validation than general aviation. The ND IR alternator has been around for over 30 years and no auto OEMs have used external regulators for at least 25 years to my knowledge. If they thought external regs were more reliable, they'd still be using them. You simply don't see many alternator OV failures on GENUINE ND units in cars and the auto manufacturers cannot accept failures on the huge scale they produce at. I'll trust Denso's design, engineering and validation on tens of millions of alternators long before I'll trust the likes of some small aftermarket firms producing hundreds per year, especially those which show a 25% failure rate in less than a couple hundred hours in some cases.

Continue the analysis on this topic but please stop the useless conjecture.

I've gone to some trouble to produce what info I can track down, pulled my plane out into a snow drift to start it up and shoot the video and pulled my cowling to verify the wiring connections. Time for someone else to step up and produce some useful information which will enlighten us further about the possibilities of being able to shut down one of these units with a shorted regulator if you think that's a likely scenario.

In the meantime, I'm going to keep flying my IR ND alternator and lead acid AGM batteries with the conviction that the IR is never going to have an OV event in my flying career, based on my long experience with these units. I'd be a lot more concerned about other things in the airplane giving me a bad day.
 
Last edited:
I placed a temp probe on the back top of my Plane power alternator, The temp never got over 100 deg. F. during my flight. I do have a small blast port (3/4") pointed at the alternator under the left ramp.

My battery has a temp probe also. Mounted on the firewall lower left, it sees about 175 deg. F.
 
I placed a temp probe on the back top of my Plane power alternator, The temp never got over 100 deg. F. during my flight. I do have a small blast port (3/4") pointed at the alternator under the left ramp.

My battery has a temp probe also. Mounted on the firewall lower left, it sees about 175 deg. F.

Thanks for posting. This is the kind of real world data I'm interested in and will help us get a better picture of the whole topic.
 
Last edited:
So now that we've established you can indeed shut down charging via the IG wire on the ND IR alternator in question, here's a little more info to answer Dan's questions:

....from the other thread.

Thanks. You've covered the details. Good work!

...I'm going to keep flying my IR ND alternator and lead acid AGM batteries with the conviction that the IR is never going to have an OV event in my flying career,

It could be worthwhile to check some of the ND's for built-in OV protection.
 
It could be worthwhile to check some of the ND's for built-in OV protection.

That's an answer I don't know but wouldn't it be cool if the ND engineers thought of that and incorporated some hardware to make it happen.

Sorry I'm way too busy at the moment to do any more investigation on this for a while...
 
I'm glad to see we have our best man on the case now. Dan Horton will be looking into the internals of these alternators and give us the real information in his usual thorough manner. :)
 
Revisiting this thread with a new approach to OV protection. There was plenty of confusion in that epic EarthX thread, and I think I have distilled some knowledge into an inexpensive, workable solution to protect my electrically dependent airplane equipped with an internally regulated, “car” alternator.

First up is this neat little device that DanH introduced a while back:

https://www.tomtop.com/p-e1021.html...MIsqCTmrvu2AIVC4B-Ch3zUACUEAkYDSABEgKZ4fD_BwE

My plan is to install one of these to monitor my primary buss and if the voltage exceeds a set limit – say 16 volts – it will crowbar the alternator field wire to ground and pop the breaker. That should end the OV event with my particular alternator. I know there is some speculation that a rouge alternator regulator will not shut down the output in some failure modes, so in that case, I also have a second little voltage monitor riding on my ECU buss which will open a relay, and cut the ECU free from the ship’s alternator. Think of a glider pilot on tow, pulling the rope release if the towplane’s engine quits.

These two devices should be my “belt and suspenders” to keeping the ECU alive.

But what about the expensive avionics being fried by the rouge alternator? Well, TVS diodes are available in a plethora of voltage ranges, and at less than .50 cents each, they are an affordable means to crowbar the B lead on the alternator.

https://www.digikey.com/products/en?keywords=sa10alfct-nd

If I understand it correctly, the above activate at 17 V and will short the B lead to ground, popping a breaker. You will need a few of them in parallel to handle the full output of the alternator for a few milliseconds, but again, they’re cheap.

Now I should have the belt, suspenders, and another belt.

Anyone have any experience or comments with these TVS diodes in this application?
 
If I understand it correctly, the above activate at 17 V and will short the B lead to ground, popping a breaker. You will need a few of them in parallel to handle the full output of the alternator for a few milliseconds, but again, they?re cheap.

Now I should have the belt, suspenders, and another belt.

Anyone have any experience or comments with these TVS diodes in this application?

Uh I think putting TVS in parallel may not be the best. Depending on the exact voltages the diode trip, they may not share the current. They could burn out in a zipper fashion instead of sharing the load.
 
Uh I think putting TVS in parallel may not be the best. Depending on the exact voltages the diode trip, they may not share the current. They could burn out in a zipper fashion instead of sharing the load.

Same part number, should behave the same. You're not suggesting having them in series, are you?
 
It's not a matter of 'same part number'. Semiconductors are almost never perfectly matched. One will tend to hog most of the load until it fails and then the next, and so on. If you know what to look for, you can see compensation for that issue in all sorts of devices. It even applies to terminals and switch contacts; see the Aeroelectric articles on paralleling subD pins for extra current handling. It can be done, but requires 'ballasting' leads 6-8 inches long before joining them to the single supply lead.

A 60 amp alternator B-lead should be protected by at least an 80 amp fuse, or equivalent CB. If you use a CB, it can take quite a while (relatively speaking) for it to trip. It's almost certain those transorbs will all blow before the breaker.

If you keep adding layers, you'll eventually make it less reliable through complication. :)

FWIW, my approach in my electron-dependent engine/airframe is to use the Aeroelectric OV protection design for dynamo style alternators (contactor in series with the B-lead) and the engine controller fed directly from the battery: battery>fusible link>wire>high current switch>controller. Dan's little module would work fine to drive the AEC protection circuit....
 
Fair enough. Whether the transorbs are used as the physical means to crowbar the b lead or the logic to control a b lead contactor, dumping the alternator off line can be accomplished pretty easily. This makes the discussion over internally vs. externally regulated alternators redundant. For me, that's really the only remaining issue I have with an electrically dependent engine: To be absolutely certain I can kick the OV event off the buss.

Here's one good for 70 amps:

https://www.digikey.com/product-det...sion/1N6376-E3-54/1N6376-E3-54GICT-ND/3847534
 
Last edited:
I agree on the internal/external regulator and internal OV protection issues. Once I had OV licked, I could see no good reason to spend $500-$700 per alternator when an off the shelf IR alt from the nearest auto parts store @ $60-$100 would get the job done. And with an auto engine, I have the luxury of running two identical alts; no need to load shed if one dies.

I've run auto alts as the only alt on Lycs for a couple of decades; I'm happy with their reliability for my purposes.

Charlie
 
Back
Top