Alternator Failure

[erich weaver]

Originally Posted by Low Pass

Or an overvoltage annunciator. Second most critical to a low oil pressure annunciator. Looks like that battery cooked for a long time.

Overvoltage events, though rare, can happen almost instantaneuously. You would not be able to manually shut your alternator down in time to save your avionics in such cases. You need automated overvoltage protection to save the day.

[SHIPCHIEF]

I tried a cool little permanent magnet alternator from a John Deere garden tractor, but the high RPM caused by the Lycoming pulley size caused an over voltage condition before I ever flew it. I noticed the regulator driven idiot light flashing during Static RPM testing, and the volt meter just starting to break out of the 14.4 previous volts.
Now I have a DENSO Mini 2 ear alternator. It's a sweet little one wire unit with internal regulator. I'm sure these are very popular with the RV crowd, as they are light and put out a generous current. They are also very inexpensive.
What they don't have is overvoltage protection.
Lynn French (comments by 'Lectric Bob) went thru the bother to open a DENSO up, and add external regulation and posted the results online:
http://www.aeroelectric.com/articles...Conversion.pdf
I would be interested in retaining the internal regulation and simply adding the field shutdown circuit. Does anyone recall a DIY post on this? Or have anything to add?

[Low Pass]

Originally Posted by erich weaver

Overvoltage events, though rare, can happen almost instantaneuously. You would not be able to manually shut your alternator down in time to save your avionics in such cases. You need automated overvoltage protection to save the day.

Didn't say over voltage devices weren't good. But an alarm (if noticed) would have allowed him to protect the battery because this event occurred over many minutes.

But further, what avionics would be harmed by 15, 20 volts? My Dynon info says it's good from 12-30 volts, King radio, xpdr - 12-24. Garmin G3X, 10-32 vdc. (These are the specs, didn't say I would try it! )

I did have an over voltage condition some 12, 13 yrs ago. I lost a couple of LED elements on my trim pos indicator (nothing else). No annunciator or protective devices. I spotted the volt meter at 17, 18 volts and shut off the alt field.

[erich weaver]

I don't consider myself an expert in such matters, but to my knowledge, over voltage events are not limited to the 15-30 volt range.
Erich

[cfiidon]

Originally Posted by DennisRhodes

Does anyone know of a supplier for a "free Standing" 14 v system over voltage protection module aside from the built in models usually included with the Alt or external regulator?

I would recommend this one:

http://www.periheliondesign.com/lovm.htm

It has a trip level of 16.2 volts. It is not a "crowbar", which forces a circuit breaker pop or fuse blow, but a device which senses the overvoltage and then interrupts the field supply gracefully.

Don

[DanH]

Be aware the common Plane Power alternator has a crowbar built into its internal regulator.

[John Tierney]

Will this do?
http://www.bandc.biz/over-voltageprotectionmodule.aspx

[Camillo]

Not to highjack the thread, but if you install a B&C regulator (which has an O/V protection) take care to cover it in a way so no water could enter in it. I experienced a recurrent electric system fail, included continuous alternator field braker trip which almost made me abort a travel in Greece, untill I discovered it was dued to water inside the regulator. Regulator is installed in the upper portion of the firewall (engine side) and of course is covered by the cowl. However, I suspect that when parked outside during rain, water enters between the cowl and the upper fuse skin and then in the regulator. See my RV9 site, FLIGHT! page for details.
Camillo

[Low Pass]

Originally Posted by DanH

Be aware the common Plane Power alternator has a crowbar built into its internal regulator.

Very good to know! Might look that way at next replacement opportunity.

[krw5927]

Originally Posted by Camillo

Not to highjack the thread, but if you install a B&C regulator (which has an O/V protection) take care to cover it in a way so no water could enter in it. I experienced a recurrent electric system fail, included continuous alternator field braker trip which almost made me abort a travel in Greece, untill I discovered it was dued to water inside the regulator. Regulator is installed in the upper portion of the firewall (engine side) and of course is covered by the cowl. However, I suspect that when parked outside during rain, water enters between the cowl and the upper fuse skin and then in the regulator. See my RV9 site, FLIGHT! page for details.
Camillo

Perhaps the B&C regulator manual has been updated since you purchased yours. It now contains this rather stern warning: "NOTE - take care to choose a mounting location that will protect the LR3C from heat, vibration, and water".

Additionally, mounting on the cabin side of the firewall is encouraged in the manual.