Alternator Fooled Me

[jimgreen]

Mystery solved with the flickering light on my PlanePower alternator.
That darned light has been flickering faintly for at least 100hrs, even though it has always produced good power. The alternator has been bench tested but not disassembled
The alternator finally quit at 261 hrs, so it went to our local shop and $120+tax later it is back in service.
The fix was a new stator. Turns out the stator is not keyed into position, but merely clamped by the case screws. In this case there was slight rotational movement as evident from the chafing marks, and over time this broke the connections to the stator. Needless to say the new stator is fixed, I believe with a Loctite product.
No more flicker.

[KRviator]

Following on from Dan's issues - and rather than start a new thread - I thought I'd seek the collective help of the VAF Brains Trust on a nearly identical issue.

For the last 20 or so hours, I have been trying to work out what is causing my alternator to be constantly hunting in output. The alternator is a single PlanePower FS-14B, one of those internally-regulated ones that mounts on the vacuum pad.

From my "Running a tank dry" video, it also shows the problem I'm having, with the voltage and amperage fluctuating between 14.5-14.8V and 8-16 amps.
https://www.youtube.com/watch?v=PSexkSe8gl8

I flew again today after running a series of resistance checks on the B-lead connections, the master contactor connections and amp shunt fittings, all were secure and no variation to the resistance was shown during the tug tests. I'd previously removed the 3-pin plug and noted a small amount of corrosion on one of the female pins, though nothing I'd class as troubling. Today, I removed the 3-pin plug and also removed the 2 female pins from the housing, and squeezed them down slightly before reinstalling it. Next step is to replace the plug and pins in their entirety.

Of note, when the battery is low, ie for the first 10-20 minutes of flight, there are no problems, it charges normally and indications are rock-steady. When the problem manifests itself, turning the alternator OFF drops the indicated amperage to 0 and battery volts to around 13.5-14.0 as you'd expect. Reselecting the alternator several minutes later shows normal charging until the current drops, then the problem recurs.

From what I've done so far, I figure:

• I don't have any loose fittings (the only one left to check is the Alt Field pin onthe VPX-end socket)
• The problem is 'actual', not an 'instrumentation' problem.
• The problem is internal to the PP alternator
• The problem is not vibration-related as it is too regular in its' cycling.

I can't see a problem doing so, but rather than replacing the alternator, is there any reason I can't install a separate external voltage-regulator in addition to the internal one in the PP unit?

So...Does anyone have any ideas?

[n18pf]

Sounds like you checked all of the positive connections. Did you also check the ground connections from the alternator all the way back to the battery and instrument panel?. I suggest you disconnect all of them, clean them and reinstall.

[lr172]

Originally Posted by KRviator

Following on from Dan's issues - and rather than start a new thread - I thought I'd seek the collective help of the VAF Brains Trust on a nearly identical issue.

For the last 20 or so hours, I have been trying to work out what is causing my alternator to be constantly hunting in output. The alternator is a single PlanePower FS-14B, one of those internally-regulated ones that mounts on the vacuum pad.

From my "Running a tank dry" video, it also shows the problem I'm having, with the voltage and amperage fluctuating between 14.5-14.8V and 8-16 amps.
https://www.youtube.com/watch?v=PSexkSe8gl8

I flew again today after running a series of resistance checks on the B-lead connections, the master contactor connections and amp shunt fittings, all were secure and no variation to the resistance was shown during the tug tests. I'd previously removed the 3-pin plug and noted a small amount of corrosion on one of the female pins, though nothing I'd class as troubling. Today, I removed the 3-pin plug and also removed the 2 female pins from the housing, and squeezed them down slightly before reinstalling it. Next step is to replace the plug and pins in their entirety.

Of note, when the battery is low, ie for the first 10-20 minutes of flight, there are no problems, it charges normally and indications are rock-steady. When the problem manifests itself, turning the alternator OFF drops the indicated amperage to 0 and battery volts to around 13.5-14.0 as you'd expect. Reselecting the alternator several minutes later shows normal charging until the current drops, then the problem recurs.

From what I've done so far, I figure:

• I don't have any loose fittings (the only one left to check is the Alt Field pin onthe VPX-end socket)
• The problem is 'actual', not an 'instrumentation' problem.
• The problem is internal to the PP alternator
• The problem is not vibration-related as it is too regular in its' cycling.

I can't see a problem doing so, but rather than replacing the alternator, is there any reason I can't install a separate external voltage-regulator in addition to the internal one in the PP unit?

So...Does anyone have any ideas?

Sounds like the voltage regulator or it's connections/wire inside the alt case. The VR inside the alternator is replaceable and would suggest starting there. The fact that everything works well under high load would indicate there are no wiring issues. Lots fo these PP's have stator failures. I am not an expert on alternators, but would investigate if the early stages of stator failure could cause the fluctuations. Doesn't seem likely, but don't know.

You can also check for problems with certain loads. I see current fluctuations routinely, due to devices like strobe power supplies and wig wag lights, etc. However, typically a good VR will keep the voltage swings to about .1 volts during these current swings.

Larry

[BMW_X6M]

My voltage would go high, over 15 volts intermittently. I found my negative battery cable was not tight at the battery. I torqued it to 80 inch pounds which solved the problem. Also A/S has the PP regulator in stock. It is a drop in assembly and includes the brushes. I purchased one as a spare.

[rv7charlie]

You can't install an external 'in addition to' the internal regulator. You could mod the alternator to use an external, but there's no way to use two at once; the regulator controls field voltage, and whichever regulator sends the most voltage will be the one controlling alt output. (And it's a total unknown whether one reg would destroy the other, or possibly have mutual destruction.)

It's worthy of consideration that current varying by 100% while voltage varies by <4% is pretty unlikely, unless you have a *load* that's intermittent. It's also noteworthy that voltage seems to rise as current is going up, by a *lot* more than a half volt could drive, and voltage falls as current is falling.
DC circuits are pretty much a straight power formula: V=I*R. So with round numbers:
14V*8A=112 Watts
If voltage goes to 14.5 & the load isn't changing,
112/14.5=7.73A
Or viewed another way,
14.5V*15A=217.5 Watts

If the numbers are real, your power is varying by almost 100% while your voltage is varying by <4%.

What leads you to conclude that the changes are real and not instrument error?

What kind of battery, a lithium? Any lead-acid battery would not show anywhere near 14V with the alt off line.

Long distance troubleshooting is pretty hard, but I'd suspect instrument error, and the previous post about negative side issues would be the 1st place I'd look. Not just tightening connections, but opening them, cleaning mating surfaces, and reinstalling. Then I'd get the VPX out of the circuit, at least for testing purposes. (process of elimination)

Charlie

[KRviator]

Originally Posted by lr172

Sounds like the voltage regulator or it's connections/wire inside the alt case. The VR inside the alternator is replaceable and would suggest starting there.

That's my initial thought as well. BMW_X6M mentions Spruce as a source, but I'm struggling to find the page for it.

Originally Posted by lr72

You can also check for problems with certain loads. I see current fluctuations routinely, due to devices like strobe power supplies and wig wag lights, etc. However, typically a good VR will keep the voltage swings to about .1 volts during these current swings.

(Un)Fortunately, my RV is minimally equipped, I have the electric fuel pump, VP-X, Xcom VHF, 1x Dynon SkyView with their transponder and a pair of servos. No lights at all, and the only relatively high-current device is the flap motor.

Originally Posted by BMW_X6M

My voltage would go high, over 15 volts intermittently. I found my negative battery cable was not tight at the battery. I torqued it to 80 inch pounds which solved the problem. Also A/S has the PP regulator in stock. It is a drop in assembly and includes the brushes. I purchased one as a spare.

I didn't think to check the negative cables you know...I will do that next week on my RDO's, though of course it makes sense, a high resistance connection = low volts, VR attempts to compensate, yadda yadda. The regularity of the fluctuations is what's got me beat. And as above, could you point me to the Spruce spare VR? I'm struggling with my Google-fu...

Originally Posted by rv7charlie

You can't install an external 'in addition to' the internal regulator. You could mod the alternator to use an external, but there's no way to use two at once; the regulator controls field voltage, and whichever regulator sends the most voltage will be the one controlling alt output. (And it's a total unknown whether one reg would destroy the other, or possibly have mutual destruction.)

That eliminates a simple fix then, unfortunately...

Originally Posted by rv7charlie

It's worthy of consideration that current varying by 100% while voltage varies by <4% is pretty unlikely, unless you have a *load* that's intermittent. It's also noteworthy that voltage seems to rise as current is going up, by a *lot* more than a half volt could drive, and voltage falls as current is falling.
DC circuits are pretty much a straight power formula: V=I*R. So with round numbers:
14V*8A=112 Watts
If voltage goes to 14.5 & the load isn't changing,
112/14.5=7.73A
Or viewed another way,
14.5V*15A=217.5 Watts

If the numbers are real, your power is varying by almost 100% while your voltage is varying by <4%.

What leads you to conclude that the changes are real and not instrument error?

My conclusion came about based on nothing more than the fact the readings are stable at high-current draws, and as current flow tapers off the fault appears. I was thinking at times of low current demand, a small variation in resistance (sensed voltage really) would cause a relatively big change in voltage output. Thinking about this a bit more, I should pull up the AltField current on the VP-X screen to see what it is doing, while this is going on.

Originally Posted by charlie rv7

What kind of battery, a lithium?

Yes, a Shorai lithium, though it is around 4 years old now.

Originally Posted by rv7 charlie

Long distance troubleshooting is pretty hard, but I'd suspect instrument error, and the previous post about negative side issues would be the 1st place I'd look. Not just tightening connections, but opening them, cleaning mating surfaces, and reinstalling. Then I'd get the VPX out of the circuit, at least for testing purposes. (process of elimination)

Charlie

I will do that, and report back next week. Hopefully the weather cooperates!

[acwrench]

Reading through the thread and catching a hint that the PP alternator is somewhat of a copy of popular auto alternator. Brought in my alt to an auto part supplier and asked if he could check it out and he wanted to know what kind of auto it was out of before he could attempt to put on the test stand. Thought it should be easy to test generically, but guess not! Any ideas out there on the PP AL 12E160/C and how to identify it's roots. Originally bought from Van's. Shows 13.7 volts when it's working but had it as low as 10 volts when I started to shut things down to get home. 10 minutes of running on the battery only I decided to try it and there it is charging at 35A. Checked connections at both ends but haven't dug into the field connector ( bought another one in case ) the Alt has 100 hrs on it!!

Thanks

[rv7charlie]

Skip the retail auto supply, and take it to an auto-electric shop (rebuilder). There should be at least one nearby, if you're in a major metro area.

They will likely be able to ID it without the auto source.

[RV7 To Go]

Originally Posted by acwrench

Reading through the thread and catching a hint that the PP alternator is somewhat of a copy of popular auto alternator. Brought in my alt to an auto part supplier and asked if he could check it out and he wanted to know what kind of auto it was out of before he could attempt to put on the test stand. Thought it should be easy to test generically, but guess not! Any ideas out there on the PP AL 12E160/C and how to identify it's roots. Originally bought from Van's. Shows 13.7 volts when it's working but had it as low as 10 volts when I started to shut things down to get home. 10 minutes of running on the battery only I decided to try it and there it is charging at 35A. Checked connections at both ends but haven't dug into the field connector ( bought another one in case ) the Alt has 100 hrs on it!!

Thanks

I took my Vans supplied PP 60 A alternator to a local alternator/starter repair shop. They tested it and told me they suspected a rectifier failure which took out the built in regulator (I had a runaway alternator issue taking out the field fuse).This happened after 4 hrs of operation. Cost $100 and had it back in a week. They said the parts were common auto parts. Been running fine for the last year and half and 230 hrs.