Alternator Plane Power 99-1012

[Sebastian]

I just had a failure of my Plane Power alternator with only a hundred hours of service. When it failed I thought it was just the voltage regulator since it had no output. This failure left me stranded in Farmington, MO and I live outside Houston, TX. I was able to find a starter/alternator rebuild place that didn't freak out that it was off an experimental aircraft and would work on it. Turns out it wasn't the voltage regulator at all, it was the wiring field the stator rotates in. Four of the connection wires were broken, most likely due to the initial build of the alternator or the modification made to it by Plane Power.
These alternators are Denso products that are then modified by Plane Power. They also modify the voltage regulator for the over-voltage protection which means if your regulator goes out you can't just go to the local auto parts and get a new one. A/S does sell the regulator and the number is 07-17968. I found this on the Van's RV forum.

I'm going to try to attach some pictures of the damage. GPKS6442.jpgIMG_1812.jpgIMG_1811.jpg The 1st is the voltage regulator w/modification, the last two are the winding.

[jaredyates]

I got around 200 hours out of mine, as I recall. Back when they were $300 alternators this was one thing, but with the post-Hartzell prices these days I'd go for a B and C.

[Sebastian]

I still think that there has to be an automotive alternator the same physical size that would last even longer. Anybody know of one?

[TrueAirSpeed]

Like Jared, I use B&C on my RV-7 and the BH. 350 hours on the one in my -7 and no problems. Same with the BH with 75 hours. Bill and hi crew at B&C are good to work with.

[Sebastian]

Is the B&C a direct replacement for the Plane Power 99-1012? What kind of price? What part number?

[jaredyates]

The B&C is externally regulated, so it will require some installation. I'd figure on half a day's work if you don't have to take the prop off to change a belt.

[zkelley2]

I still think that there has to be an automotive alternator the same physical size that would last even longer. Anybody know of one?

1980 Honda civic. It has the 3/8 belt pulley, a fan on it that spins the correct direction for a Lycoming, which is opposite most cars and uses an external voltage regulator. Get the ND one with a lifetime warranty for $80. Get 2, in case it fails you have one ready to go and one to do the warranty exchange with.
It also bolts directly to the Lycoming mounts.
I'd say you can get one at your local auto parts store, or any parts store near any random airport around the country, but I've found most don't have 1980 civic parts in stock, but they can get them in a day or two.

Two downsides, it weighs more than the b+c because the case isn't lightened. I guess you could do that if you had a mill.
And the pulley is a bit smaller than the airplane one so it spins faster.

[Sebastian]

Sounds like you have experience with this alternator. When you say buy two makes me wonder how well they hold up? Also can you please explain the down side to the alternator spinning faster. Is it that it is charging harder?

[zkelley2]

Ya, it's what I run as my primary. I use a B&C on the vacuum pad as a backup, since I'm electrically dependent. I also use the B&C external voltage regulator, one for each alternator. No issues in 300 hours. The reason I said buy 2 is, I find you have to wait forever for parts for anything anymore, and I hate down time. My flying season is somewhat limited, so every week I wait for a part is a week of flying lost. No alternator lasts forever, and on the list of things that break pretty often on airplanes, alternators is pretty high up there. Right after magnetos.

As far as spinning faster, I figure it might wear out a bit faster, but then again probably not because it's spinning a LOT faster on a car. For the total cost and hassle of putting a bigger pulley on, it wasn't worth it to me, but you can do it. It does charge at very low rpms, which is nice.

If you have a constant speed prop, I'd also recommend always putting 2 alternator belts on. One on the pulleys and one zip tied to the cylinders in a way that it can't come lose. That way when the 1st one breaks or is due for replacement you don't have the pull the prop. Really helpful if a belt breaks on you well away from home base and tools. You can have the spare on with nothing but a single socket.

Also of note, if you don't mind getting a refurbed one from rock auto they're like $20.

[rodsmith]

Seems with B&C the most likely failure is the regulator. I plan on having a spare available.

[jaredyates]

I think of an alternator kind of like a constant speed prop. When an alternator is spinning, the voltage regulator determines how much charge the alternator puts out by regulating the field voltage. To relate that to props, it's like the field voltage is the pitch of the prop, and the output voltage is like the prop RPM. You can make more or less thrust at the same RPM by adjusting the prop pitch, just as you can make more or less alternator output by adjusting the field voltage.

That's the cool thing about an alternator vs a generator- with a generator, the more you spin it, the more energy it puts out, like a fixed pitch prop. But the alternator can put out anything from zero to maximum rated output (above a certain engine rpm, say 1500 or so), regardless of engine RPM. If the RPM is too low, then there just isn't enough energy to make it happen, but once you are in the regulating range, it just does its thing.

With both alternators and generators, the electricity is created by passing a magnet by a coil, but with an alternator the strength of the magnet is determined by the amount of voltage supplied to the field. Spinning the alternator faster doesn't make more electric energy output, it just causes the regulator to supply less field voltage to create the same output. Relating it to the prop, you can increase prop RPM from 2000 to 2500 rpm, but you (or the governor) can also reduce the blade pitch if you want, to maintain the same thrust.

If you take an automotive alternator off of the shelf, it has an internal regulator. That regulator is pretty good but doesn't have absolute control in the event of an overvoltage situation. There is one rare but particular way that it can fail, such that it will destroy all of your avionics before you have a chance to do anything about it, and then you still won't be able to shut it off. If the field voltage becomes connected to the output voltage, then more output voltage means more field voltage, which means more output voltage, etc. It's basically a runaway event with ever-increasing voltage. In a car, this is an acceptable risk, because you can shut if off before things get hot enough to burn, but for me in a plane, it's not an acceptable risk. Plane Power alternators have modified regulators, which allow for total control of the field voltage at the pilot's switch, and automatic overvoltage protection. Externally-regulated alternators like the B&C have this as well. These alternators should be installed per their instructions, which include automatic overvoltage protection with a "crowbar" overvoltage system that automatically trips the field CB in an overvoltage event. This is why even on a fuse-equipped airplane, the alternator field should still have a thermal circuit breaker and not a fuse. I also use CBs for the electric ignition for a different reason, but everything else is fused.

It is possible to modify a standard automotive regulator in your home shop, and there are articles out there about how to do it. Personally, I would never install a standard automotive alternator into an airplane without first modifying its internal alternator to allow for automatic overvoltage protection, and absolute pilot control of the field voltage. I wouldn't have a problem with flying comfortably behind a self-modified alternator, but personally the cost of even a single out-of-town AOG event is too big compared to the cost savings of a modified auto parts store system vs a B&C. And these days my time tends to be worth enough to me that spending half a day modifying a $20 alternator is going to increase the cost of the cheap alternator by a factor of 30. It just isn't worth it to have a failure like the one you had, and the one I had, in some inadequately produced windings or other parts. So far the B&Cs seem to be more reliable in these ways, though I don't have real data to back that up, just stories on forums.

Also note that EarthX considers automatic overvoltage protection an absolute requirement for installing their battery, because if the BMS encounters an overvoltage alternator, it will disconnect the battery from the circuit, which will cause a major voltage spike. The battery is the one buffer to help limit the overvoltage event, up until the point that the battery (lead-acid, lithium, or otherwise) can't take the energy input and overheats. In a traditional lead acid battery, if there is an uncorrected overvoltage event, the pilot may have a few seconds to react while the battery gets abused, and may be able to "save the day" and just end up with a dark airplane, instead of a dark airplane with smoke coming from something. If the pilot doesn't do anything in a sustained overvoltage event, the battery (or something else) will fail before long, making smoke and perhaps fire. The EarthX BMS sees overvoltage and disconnects, but with no battery restraint, the alternator can now go totally nuts, and once the overvoltage gets high enough (I want to say 40v?), the BMS fails, and the battery can be brought back into the circuit. Once that happens it overheats, and boils the internal dielectric and puts out a bunch of smoke. The end result of a sustained overvoltage event is the same regardless of battery chemistry, but the path can be a little different when the battery has a BMS.

I'm getting a little off topic with the battery discussion but just want to point out how these electric architecture choices are very important. Losing electricity production in flight can be a problem, having an airplane stuck away from home can be a problem, but my primary goals are avoiding inflight "cook to the point of failure" events and damaging the expensive parts.

[zkelley2]

If you read my post you'd notice that I mentioned the automotive alternator I posted about does not have an internal regulator. It requires no modification, has the correct direction fan(which is backwards) and bolts directly to the lycoming brackets. In fact I wouldn't be surprised if it's the same core b&c uses, which is also ND.
I did use the B&C voltage regulator because unlike the john deere or ford one you can get at any auto parts store for $10, it has the over voltage protection.

There's a few other makes and models that you can get that don't either, but you'd have to do the research to figure out which ones.

[Sebastian]

zkelley2: That's good information to know.

[jaredyates]

Having it already external and the right direction is a nice plus, I missed that in your post.

[Battson]

At the risk of tempting fate, my Plane Power alternator has run flawlessly for almost 1000hrs now.
Just another data point.

[Sebastian]

That's awesome. I'm betting I now have a better one than it was when it was new after the rebuilder finding what he did.

I think you have gotten the kind of service we should all expect when we pay that amount of good money for a product that is represented as quality.