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testing of backup alternator

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Erich_Weaver(at)urscorp.c
Guest

Posted: Mon Aug 23, 2010 10:49 am Post subject: testing of backup alternator

Bob, your recently responded to a couple of posts from Jared Yates, who was asking (in part) about testing of the backup alternator in a Z-13/8 system.  Cant speak for Jared, but Im not sure his real question was effectively answered and I am interested in this as well,, so thought I would follow up.  How do I go about assuring myself that my SD-8 will work as advertised when called upon?  Can I just turn off the master, flip on the switches for the SD-8 and the  e-bus alternate feed, and wait to see if I get a low voltage warning light on my engine monitor?  Can I do this on the ground at idle, or do I need to have the RPM  elevated?  Feeling a bit boneheaded about this, but would be more boneheaded to not ask, and find out later my SD-8 was providing no backup at all.

 

 thanks for your service   

 

 Erich Weaver

   [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Aug 23, 2010 8:56 pm Post subject: testing of backup alternator

At 01:46 PM 8/23/2010, you wrote:



  	  Quote: 	
		  Bob, your recently responded to a couple of posts from Jared Yates, who was asking (in part) about testing of the backup alternator in a Z-13/8 system. Cant speak for Jared, but Im not sure his real question was effectively answered and I am interested in this as well,, so thought I would follow up. How do I go about assuring myself that my SD-8 will work as advertised when called upon? Can I just turn off the master, flip on the switches for the SD-8 and the e-bus alternate feed, and wait to see if I get a low voltage warning light on my engine monitor? Can I do this on the ground at idle, or do I need to have the RPM elevated? Feeling a bit boneheaded about this, but would be more boneheaded to not ask, and find out later my SD-8 was providing no backup at all. 	


   You can turn alternators on/off at any time under

   any conditions without regard to system safety

   or hazard to other components.



   The SD-8 does need a lot of RPM to produce full

   output. I doubt that you want to run a full-throttle

   preflight. During mag test you can turn the main

   alternator off and the SD-8 on. If the loadmeter

   shows ANY significant output, the alternator is

   probably fine even if low voltage warnings continue

   and the SD-8 output is less than 8-10 amps that you

   can expect at cruise.



   You can also wait until airborne and go to the SD-8 supported

   E-bus mode to test the system under more realistic conditions

   before you get too far from home.



 

 

        Bob . . .

                    //// 

                   (o o) 

    ===========o00o=(_)=o00o========= 

    < Go ahead, make my day . . .   > 

    < show me where I'm wrong.      > 

    =================================



     [quote][b]

longg(at)pjm.com
Guest

Posted: Thu Aug 26, 2010 11:25 am Post subject: testing of backup alternator

Erich,



I didn't catch how many replies you had on this one. On my system I have

a Dynon which monitors voltage internally and externally. Since I have

the internal battery option, I can sit there with the SD-8 running (no

interruption to the Dynon) and monitor the voltage activity on the

master/essential bus via the Dynon. The key here is having something to

monitor your system voltage that is not tied to switches and other

things you've just lost when the alternator blows. That can come in many

forms. I've seen some inexpensive LED panel voltage monitors that would

do nicely.



They're a nice feature to have when your world changes from inside the

cockpit. A continued downward trend is warning enough to get down

immediately. On the other hand you may feel you have enough output from

the SD-8 to continue on to the next best/safest alternator shop (Pep

Boys). 



Hopefully if you've reached that mode you've begun shutting off the

air-conditioning, portable fridge, DVD etc. and are just running the

minimums.



On my ship the minimums take about 3-4 amps, Dynon, 1-radio, portable

gps. 



Yes, the SD-8 seems to takes about a 1000 rpm to produce any sort of

useable output. That may vary on your installation. If it's a sunny day

I also have a solar charger to setup on the panel. That will at least

power the GPS. And we're fly'n.



Maybe the real question is whether it is worth real world testing - in

my mind, absolutely. It's a great idea to test it in the air (better

than on the ramp while your CHT's go through the roof) to see how much

endurance you ultimately have. I would like to do the full test one day

soon. Perhaps on a closed course over friendly terrain.



I think most folks will wait for an emergency to perform the real test.

In most cases that will be too late. It takes a bit of stomach to shut

things down and really stretch the limit. I'm ok with that. You will

want to land and re-start the main alternator after the test. From what

I understand it's not recommended to re-start some of these alternators

in flight. It may blow off the cowling and your firewall may melt.



Best,



Glenn E. Long



--

deej(at)deej.net
Guest

Posted: Thu Aug 26, 2010 12:22 pm Post subject: testing of backup alternator

On 08/26/2010 03:17 PM, longg(at)pjm.com wrote:

 	  Quote: 	
		   From what

 I understand it's not recommended to re-start some of these alternators

 in flight. It may blow off the cowling and your firewall may melt.


	




	Would absolutely love to see some real data to back up this claim...

Can you point us to any references?



Thanks,



-Dj



-- 

Dj Merrill - N1JOV

Glastar Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

Grumman Yankee Driver N9870L - http://deej.net/yankee/

Join us on the New England Aviation Forums - http://forum.deej.net/

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Aug 26, 2010 4:16 pm Post subject: testing of backup alternator

At 03:15 PM 8/26/2010, you wrote:

 	  Quote: 	

On 08/26/2010 03:17 PM, longg(at)pjm.com wrote:

 > From what

 > I understand it's not recommended to re-start some of these alternators

 > in flight. It may blow off the cowling and your firewall may melt.

         Would absolutely love to see some real data to back up this claim...

Can you point us to any references?

   I've been testing alternators and generators on airplanes,

   laboratory test stands and an odd assortment of vehicles

   for 40+ years. We turn them on, off, no-load, full-load,

   you name it. Whether or not there's a battery on line.

   See chapter on engine driven power sources in:

http://www.aeroelectric.com/Book/AEC12A_PDF.zip

   Having said that, there MAY be regulator characteristics

   (whether internal in or external) that present poor transient

   response without a battery on line. Indeed, this is one

   of the situations described by "load dump" in automotive

   parlance and "battery dump" in aviation parlance. Depending

   on how wildly the system behaves without a battery, SOME

   devices may be at risk if they're tied to the bus. This

   INCLUDES poorly designed regulators. This was the problem

   reported but not understood a few years back when some

   folks experienced alternator/regulator damage when switching

   a Z-24 system off with the alternator loaded. However,

   this is the exception.

   Bottom line is, as long as the battery stays tied to the

   alternator's b-lead, there's nothing you can do with

   switches on the panel that will hurt anything . . .

   In other words, transients generated by such activities

   do not exceed NORMAL operating transients as described

   in Mil-STD-704 and DO-160.  Even with Z-24 configuration,

   an internally regulated alternator worth your hard-earned

   dollars is not at-risk for inadvertent switch positioning.

   Bob . . .

klehman(at)albedo.net
Guest

Posted: Fri Aug 27, 2010 4:40 am Post subject: testing of backup alternator

I definitely failed a John Deere PM regulator just by starting the 

engine on the ground with a totally dead battery. An immediate over 

voltage caused the crowbar OV module to trip the AC relay off, and the 

regulator evermore put out max voltage after the battery was recharged. 

I never have had a large capacitor in that system which might have 

helped. It was a sealed battery and they don't accept current for some 

time (if ever) when totally discharged. Undoubtedly the same failure 

would occur with a disconnected battery.

Ken

Robert L. Nuckolls, III wrote:

 	  Quote: 	

 <nuckolls.bob(at)aeroelectric.com>

 At 03:15 PM 8/26/2010, you wrote:

> 

>

> On 08/26/2010 03:17 PM, longg(at)pjm.com wrote:

> > From what

> > I understand it's not recommended to re-start some of these alternators

> > in flight. It may blow off the cowling and your firewall may melt.

>         Would absolutely love to see some real data to back up this 

> claim...

> Can you point us to any references?

   I've been testing alternators and generators on airplanes,

   laboratory test stands and an odd assortment of vehicles

   for 40+ years. We turn them on, off, no-load, full-load,

   you name it. Whether or not there's a battery on line.

   See chapter on engine driven power sources in:

 http://www.aeroelectric.com/Book/AEC12A_PDF.zip

   Having said that, there MAY be regulator characteristics

   (whether internal in or external) that present poor transient

   response without a battery on line. Indeed, this is one

   of the situations described by "load dump" in automotive

   parlance and "battery dump" in aviation parlance. Depending

   on how wildly the system behaves without a battery, SOME

   devices may be at risk if they're tied to the bus. This

   INCLUDES poorly designed regulators. This was the problem

   reported but not understood a few years back when some

   folks experienced alternator/regulator damage when switching

   a Z-24 system off with the alternator loaded. However,

   this is the exception.

   Bottom line is, as long as the battery stays tied to the

   alternator's b-lead, there's nothing you can do with

   switches on the panel that will hurt anything . . .

   In other words, transients generated by such activities

   do not exceed NORMAL operating transients as described

   in Mil-STD-704 and DO-160.  Even with Z-24 configuration,

   an internally regulated alternator worth your hard-earned

   dollars is not at-risk for inadvertent switch positioning.

   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Aug 27, 2010 6:01 am Post subject: testing of backup alternator

At 07:28 AM 8/27/2010, you wrote:

 	  Quote: 	
		  



I definitely failed a John Deere PM regulator just by starting the 

engine on the ground with a totally dead battery.

An immediate over voltage caused the crowbar OV module to trip the 

AC relay off,


	


      Hmmm . . . It may be that the JD rectifier/regulator

      has some feature a bit short on robustness . . . but

      the scenario you describe is not one that immediately

      suggests this. It's a certainty that yard maintenance

      equipment is quite often jump-started into a dead battery.

 	  Quote: 	
		  and the regulator evermore put out max voltage after the battery was 

recharged.


	


     This my have been an isolated failure. Have you replaced

     the r/r and found that everything works as expected?



 	  Quote: 	
		  I never have had a large capacitor in that system which might have helped.


	


     This would not have made any difference.



 	  Quote: 	
		  It was a sealed battery and they don't accept current for some time 

(if ever) when totally discharged. Undoubtedly the same failure 

would occur with a disconnected battery.


	


    Maybe, but does the owner's manual for any item

    of JD equipment caution against operations with

    a completely discharged but otherwise good battery?

    I'm not sure you have enough data about the

    manufacturer's design goals to arrive at this

    conclusion. Certainly the scenario you describe

    happens many times on perhaps thousands of mowers

    and tractors every summer . . . if they were blowing

    up R/R like popcorn, I have to believe there would

    be some scrambling around in the JD engineering

    community to fix it.



    Obviously, my earlier comment to this thread

    pertained only to wound-field alternators. The

    permanent magnet devices with rectifier/regulators

    are another breed of cat.

   Bob . . .

longg(at)pjm.com
Guest

Posted: Fri Aug 27, 2010 6:35 am Post subject: testing of backup alternator

DJ,



I do not but, based on Bob's generally reliable response I don't have to

worry about pilot tales to complete my testing. As Bob indicated unless

the battery is completely dead (not gonna happen in my case -on purpose

- caus' the Lightspeed requires min 5 volts to run), I can safely switch

on and off. That gives me the added comfort of continuing my flight say

if the alt CB pops momentarily and I want to turn off the Alt to reset

it. Naturally I'll only do that once in unknown circumstances. 



In most cases I could run a very long distance with the SD-8. 



One easy way to provide proof for yourself is to go out and do the

tests. If so worried, turn off everything else first. If you don't know

the limits of your machine, you don't know your machine.



I'll be out testing.



Glenn E. Long



--

deej(at)deej.net
Guest

Posted: Fri Aug 27, 2010 6:53 am Post subject: testing of backup alternator

On 08/27/2010 10:31 AM, longg(at)pjm.com wrote:

 	  Quote: 	
		   


	


 	  Quote: 	
		   One easy way to provide proof for yourself is to go out and do the

 tests. If so worried, turn off everything else first. If you don't know

 the limits of your machine, you don't know your machine.


	




Hi Glenn,

	I've turned on and off the alternator with the engine running many

times without incident.  In particular, I was taking mild exception with

your statements:



 	  Quote: 	
		  > From what

> I understand it's not recommended to re-start some of these

 alternators

> in flight. It may blow off the cowling and your firewall may melt.


	




	which I do not believe are true, and was asking if there were any

references where this had actually happened.  I've certainly never heard

of a cowling blowing off nor a firewall melting due to someone turning

on their alternator...  



	Could be you were trying to be sarcastic, in which case I was hoping no

one was actually thinking you were serious, and wanted to attempt to

stop more Old Wives Tales on this topic...  



Thanks,



-Dj



-- 

Dj Merrill - N1JOV

Glastar Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

Grumman Yankee Driver N9870L - http://deej.net/yankee/

Join us on the New England Aviation Forums - http://forum.deej.net/

klehman(at)albedo.net
Guest

Posted: Fri Aug 27, 2010 7:32 am Post subject: testing of backup alternator

Yes a replacement regulator has worked perfectly for several hundred 

hours.  You make a good point about the lawn equipment and dead 

batteries so maybe it was a one off failure. From what I've seen over 

the years though I think a dead flooded cell battery (as found in all 

the lawn equipment that I've seen) might have absorbed enough current to 

prevent the failure.  So my theory is that the sealed AGM battery was 

the critical factor. It was a totally discharged battery. Anyway thought 

it might save someone a hundred dollars and some hassle to mention my 

experience.

Ken



Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckolls.bob(at)aeroelectric.com>

 

 At 07:28 AM 8/27/2010, you wrote:

> 

>

> I definitely failed a John Deere PM regulator just by starting the 

> engine on the ground with a totally dead battery.

> An immediate over voltage caused the crowbar OV module to trip the AC 

> relay off,

 

      Hmmm . . . It may be that the JD rectifier/regulator

      has some feature a bit short on robustness . . . but

      the scenario you describe is not one that immediately

      suggests this. It's a certainty that yard maintenance

      equipment is quite often jump-started into a dead battery.

 

 

> and the regulator evermore put out max voltage after the battery was 

> recharged.

 

     This my have been an isolated failure. Have you replaced

     the r/r and found that everything works as expected?

 

> I never have had a large capacitor in that system which might have 

> helped.

 

     This would not have made any difference.

 

> It was a sealed battery and they don't accept current for some time 

> (if ever) when totally discharged. Undoubtedly the same failure would 

> occur with a disconnected battery.

 

    Maybe, but does the owner's manual for any item

    of JD equipment caution against operations with

    a completely discharged but otherwise good battery?

    I'm not sure you have enough data about the

    manufacturer's design goals to arrive at this

    conclusion. Certainly the scenario you describe

    happens many times on perhaps thousands of mowers

    and tractors every summer . . . if they were blowing

    up R/R like popcorn, I have to believe there would

    be some scrambling around in the JD engineering

    community to fix it.

 

    Obviously, my earlier comment to this thread

    pertained only to wound-field alternators. The

    permanent magnet devices with rectifier/regulators

    are another breed of cat.

 

 

   Bob . . .

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