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Hypothetical Battery Contactor Failure

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user9253

Joined: 28 Mar 2008
Posts: 1926
Location: Riley TWP Michigan

Posted: Wed Jun 29, 2016 6:14 am Post subject: Hypothetical Battery Contactor Failure

While flying, suppose that there is failure in the battery contactor coil circuit and that the alternator continues to function.  Will the pilot notice any symptoms prior to engine shutdown?  If so, what are they?  Thanks.

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Joe Gores

skywagon

Joined: 11 Feb 2006
Posts: 184

Posted: Wed Jun 29, 2016 8:56 am Post subject: Hypothetical Battery Contactor Failure

Hmmm. . . . Interesting scenario. . . .



First thought is. . . if one is good at watching steam gauge detail, the 

amp/current meter should drop 1-2 amps because the support charge going to 

the battery is cut off.  Maybe some audio noise may increase in headsets, 

etc., since the battery, acting as a huge filter capacitor, is not able to 

do its secondary job being cut off via the open contactor. . . .

Dave



---

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racerjerry

Joined: 15 Dec 2009
Posts: 202
Location: Deer Park, NY

Posted: Thu Jun 30, 2016 3:42 am Post subject: Re: Hypothetical Battery Contactor Failure

On a simple aircraft such as my Cessna 172K, the voltage regulator "S" terminal is supplied with power through the battery contactor.  If no power is present at the voltage regulator, the alternator field SHOULD not be energized rendering the alternator inoperative.  The first noticeable indication after battery voltage bleeds down is that my VHF radio display (KX-155) goes blank.



In order to alert me to take necessary steps to conserve battery power after an alternator failure, I installed a "13V Idiot Light" from Perihelion Design, which I highly recommend.  Only $50 and legally installed without paperwork using Velcro and powered through cigar lighter.  In addition, I added a Westach 6-16 VDC voltmeter to give  me a REAL indication instead of the near worthless ammeter.

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Jerry King

user9253

Joined: 28 Mar 2008
Posts: 1926
Location: Riley TWP Michigan

Posted: Thu Jun 30, 2016 5:13 am Post subject: Re: Hypothetical Battery Contactor Failure

Once an engine is running above idle, the battery no longer supplies electrical power to the aircraft.  The alternator does.  Many alternators will continue to operate if the battery is then disconnected.  The electrical current needed to power the alternator field comes from the alternator output, whether the battery is connected or not.  There may be some alternators that will not continue to run without a battery connected.  Even for alternators that do continue to operate without a battery, the alternator could stop working if a very large electrical load is turned on which causes the system voltage to momentarily drop.

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Joe Gores

ceengland7(at)gmail.com
Guest

Posted: Thu Jun 30, 2016 5:26 pm Post subject: Hypothetical Battery Contactor Failure

On 6/30/2016 4:20 PM, user9253 wrote:

 	  Quote: 	
		   



 Thanks for the knowledgeable answer.  Once your new test bench is up and running, it would be interesting to verify or disprove this statement quoted from the Rotax 912 Installation Manual,



> Never sever connection between terminal C and B of regulator (e.g. by removal of a fuse) while the engine is running. Overvoltage and regulator damage can occur.

 I find that statement hard to believe.  When voltage is removed from Rotax regulator terminal C, its DC output should shut off, not increase.  Of course the AC voltage would increase due to lack of load, but not anymore than if all electrical loads were shut off.



 --------

 Joe Gores



I don't know squat about Rotax stuff or their manual, but...
	




If it's a PM style alternator, and the regulator is a shunt style 

regulator, and breaking that C-B connection removes the shunt load, then 

I can see how the regulator might be damaged. If the regulator 

sensing/control semiconductors are still connected to the alternator 

output but the shunt *isn't*, then the alternator could well be able to 

create a high enough voltage to exceed the max voltage ratings of the 

devices.



Having the shunt *in* the circuit would ensure that the voltage never 

got that high.



Charlie

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user9253

Joined: 28 Mar 2008
Posts: 1926
Location: Riley TWP Michigan

Posted: Thu Jun 30, 2016 7:36 pm Post subject: Re: Hypothetical Battery Contactor Failure

The Rotax (Ducati) rectifier/regulator is a switching-power-supply type of regulator that turns on for part of the dynamo AC cycle.  There is no shunt.

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Joe Gores

ceengland7(at)gmail.com
Guest

Posted: Fri Jul 01, 2016 5:08 am Post subject: Hypothetical Battery Contactor Failure

No argument on those points, but if the contents of the document are artifacts from 'the bad old days'.....



On Thu, Jun 30, 2016 at 9:11 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 	  Quote: 	
		     	  Quote: 	
		  If it's a PM style alternator, and the regulator is a shunt style regulator, and breaking that C-B connection removes the shunt load, then I can see how the regulator might be damaged. If the regulator sensing/control semiconductors are still connected to the alternator output but the shunt *isn't*, then the alternator could well be able to create a high enough voltage to exceed the max voltage ratings of the devices. 	


   Nobody has built a shunt style regulator in

   a very long time. A few small systems on motor

   bikes and snowmobiles popularized the simple

   design but the B&C regulators have never been

   shunt . . . the alleged schematic of the Ducatti

   R/R is also a series regulator.



   They are manufactured as a spares item but better

   regulators are so easy to design, there's no reason

   to stay with shunt style.



  	  Quote: 	
		  Having the shunt *in* the circuit would ensure that the voltage never got that high. 	


   but it WOULD drive internal energy dissipation

   to the max and, give the demonstrably poor

   thermal management of many designs, could

   toast the device.  But I'm pretty sure

   nobody builds/offers that control philosophy to

   on the product we're using.



 

 

   Bob . . .

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yellowduckduo(at)gmail.co
Guest

Posted: Fri Jul 01, 2016 8:44 am Post subject: Hypothetical Battery Contactor Failure

I refrained from commenting on interpretation but I was also stunned to 

see Bob (my guru of "get the numbers so we can understand it") use the 

word "immeasurably"  

just poking fun...

Ken

do not archive



On 01/07/2016 11:48 AM, erich weaver wrote:

 	  Quote: 	
		   



 [quote="nuckolls.bob(at)aeroelect"]At 08:13 AM 6/30/2016, you wrote:

   

> 

>

>    In the mean time, as long

>     as you don't hit the alternator with a really BIG load

>     (which few system are capable of doing anyhow), the

>     modern alternator runs self-excited and benefits immeasurably

>     from battery presence with respect to noise.



 Just to clarify, did you really mean "benefits immeasurably"?  I think maybe the opposite.



 Immeasurable:  Too large, extensive or extreme to measure.



 regards,

 Erich





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=457589#457589

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raymondj(at)frontiernet.n
Guest

Posted: Sun Jul 03, 2016 3:26 pm Post subject: Hypothetical Battery Contactor Failure

Bob,



Don't tuck that piece of knowledge away just yet.  I believe you usage 

was correct.



The following is from my correspondence with my sister.  Her 

qualifications include a B.A. in English, an M.A. in Library Science and 

a career as a technical writer, copy writer, college instructor teaching 

creative writing.

-----------------------------------------------------------------------



First off, "immeasurably" is the adverbial form of the adjective 

"immeasurable," so the difference is how they are used in relation to 

the other parts of the sentence rather than in their fundamental meanings.



Cutting to the chase, we begin with the OED definition of "immeasurable" 

(adjective) which is given as "Not measurable; that cannot be measured; 

immense."



This takes us to the definition of "immeasurably" (adverb) which is 

given as "To an immeasurable extent or degree; beyond measure; 

immensely, vastly."



----------------------------------------------------------------------------

The essence of the terms in question is to describe things that can't be 

measured.  This includes things which are too small to be measured as 

well as too large to be measured.  The terms are also used to describe 

things which are too large to be measured.



 From a usage stand point I again refer to my sister's correspondence.

----------------------------------------------------------------------------



.. the phrase "benefits immeasurably" (which indeed uses the correct 

form, an adverb modifying the verb 'benefits')...



------------------------------------------------------------------------------

Bottom line the words "benefits immeasurably" convey the idea correctly 

and are used properly from a sentence construction stand point.



Hope this information is useful.



Raymond Julian

Kettle River, MN



The things we admire in men, kindness and generosity, openness, honesty, 

understanding and feeling are the concomitants of failure in our system. 

And those traits we detest, sharpness, greed, acquisitiveness, meanness, 

egotism and self-interest are the traits of success. And while men 

admire the quality of the first they love the produce of the second. 

-John Steinbeck, novelist, Nobel laureate (1902-1968)



On 07/02/2016 08:31 AM, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   At 10:48 AM 7/1/2016, you wrote:

> 

> <erich.weaver(at)aecom.com>

>

> [quote="nuckolls.bob(at)aeroelect"]At 08:13 AM 6/30/2016, you wrote:

>

> > 

> >

> >   In the mean time, as long

> >    as you don't hit the alternator with a really BIG load

> >    (which few system are capable of doing anyhow), the

> >    modern alternator runs self-excited and benefits immeasurably

> >    from battery presence with respect to noise.

> Just to clarify, did you really mean "benefits immeasurably"?  I think

> maybe the opposite.

>

> Immeasurable:  Too large, extensive or extreme to measure.



    I've been thinking that word described an unquantifiable

    entity; impossible to express in terms of quantity for any reason.

    In fact, I've learned that it refers not to generally unknowable

    numbers but only to nebulously large numbers.



    I can go to bed tonight knowing something I did not

    know this morning . . . it's a good day. Thanks for

    the heads-up!

    Bob . . .

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