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Battery AND Starter Contactor?

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jdalton77(at)comcast.net
Guest

Posted: Wed Jan 03, 2007 5:07 pm Post subject: Battery AND Starter Contactor?

Hello,

  

 I'm new to the list, and just getting started on  the wings of an RV-10, having finished the tail kit last month.  I've read  Bob's book, but as I'm starting to design my electrical system I have (at least  for now) a question.

  

 The schematic in "the book" shows the main battery  pos wire connected to the battery contactor and then from there to the  starter contactor.  I just viewed the HomebuiltHelper Video on wiring a  homebuilt and they showed the battery connected directly to the "starter  solenoid" which I think is meant to be called the starter contactor (at least it  looks like one).

  

 So my newbie questions are:

  

 1. Are both of these approaches  correct?

 2. Is the "starter contactor" any different than  the "batter contactor?"

 3.  Am I correct in that the device in the  video is not called a "solenoid?"  From reading Bob's book, I'm guessing  this is the "close but no cigar" example.

  

 Thanks and please be gentle.

  

 Jeff Dalton

   [quote][b]

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mprather(at)spro.net
Guest

Posted: Wed Jan 03, 2007 5:47 pm Post subject: Battery AND Starter Contactor?

Whooo..  This is a recurring topic of questions on the list..  Much

discussion in the archives.



Answers:



1.  It depends on your design goals.  Probably both designs aren't correct

however.  Aircraft electrical systems need a high current battery switch -

either an electrically operated relay, or a big mechanical switch.  A

primary reason is so that the whole system can be de-energized by

isolating the battery from the rest of the airplane.  The high current

switch needs to be mounted as close as practicably possible to the

battery.  The longer the run from the battery to the battery contactor,

the more care in protecting the wire that forms this connection.



2.  Starter contactors are typically momentary switches, and can take

quite a bit of power to actuate 10Watts+.  This extra current helps make

the switching action more robust - good for controlling currents in the

hundreds of amps.   Battery contactors are continuous duty devices.  They

consume less power, and won't switch a 200A+ load as robustly as the

starter contactor.



3.  Your assessment seems correct.

Regards,



Matt-



 	  Quote: 	
		   Hello,



 I'm new to the list, and just getting started on the wings of an RV-10,

 having finished the tail kit last month.  I've read Bob's book, but as I'm

 starting to design my electrical system I have (at least for now) a

 question.



 The schematic in "the book" shows the main battery pos wire connected to

 the battery contactor and then from there to the starter contactor.  I

 just viewed the HomebuiltHelper Video on wiring a homebuilt and they

 showed the battery connected directly to the "starter solenoid" which I

 think is meant to be called the starter contactor (at least it looks like

 one).



 So my newbie questions are:



 1. Are both of these approaches correct?

 2. Is the "starter contactor" any different than the "batter contactor?"

 3.  Am I correct in that the device in the video is not called a

 "solenoid?"  From reading Bob's book, I'm guessing this is the "close but

 no cigar" example.



 Thanks and please be gentle.



 Jeff Dalton

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nuckollsr(at)cox.net
Guest

Posted: Thu Jan 04, 2007 7:43 am Post subject: Battery AND Starter Contactor?

At 07:59 PM 1/3/2007 -0500, you wrote:



Hello,



I'm new to the list, and just getting started on the wings of an RV-10, 

having finished the tail kit last month.  I've read Bob's book, but as I'm 

starting to design my electrical system I have (at least for now) a question.



The schematic in "the book" shows the main battery pos wire connected to 

the battery contactor and then from there to the starter contactor.  I just 

viewed the HomebuiltHelper Video on wiring a homebuilt and they showed the 

battery connected directly to the "starter solenoid" which I think is meant 

to be called the starter contactor (at least it looks like one).



So my newbie questions are:



1. Are both of these approaches correct?



   Both will "function" . . . but you won't find a type certified

   airplane wired as shown in the video. It is the function of the

   battery contactor to remove as much power from ship's wiring as

   possible when in the OFF condition.



2. Is the "starter contactor" any different than the "batter contactor?"



   In the book we talk about the differences between starter contactors

   and battery contactors. Starter contactors are intermittent duty devices

   that draw a lot of coil current (3-5 amps) to provide large closing

   forces on the contacts.  Battery contactors continuous duty devices

   that draw typically 1 amp or less.



3.  Am I correct in that the device in the video is not called a 

"solenoid?"  From reading Bob's book, I'm guessing this is the "close but 

no cigar" example.



   All contactors (hi-current relays) have solenoids (short stroke,

   linear-motion motors) but not all solenoids have contacts. This is

   a good example of how common vernacular can confuse the details about

   a part's functionality.



   Bob . . .

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

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

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

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jdalton77(at)comcast.net
Guest

Posted: Thu Jan 04, 2007 2:19 pm Post subject: Battery AND Starter Contactor?

Thanks Bob.  I just read that in your book.



Jeff

---

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aurbo(at)ak.net
Guest

Posted: Fri Jan 05, 2007 6:50 am Post subject: Battery AND Starter Contactor?

Bob,



Thanks for the explanation, I especially like your words, "This is a good 

example of how common vernacular can confuse the details about a parts 

functionality".



I am totally confused. I bought the Van's "Starter Solenoid" and "Master 

Relay" listed on page 82 of their accessories catalog and now I can't figure 

out if they are the same animals as what are required in the Z-11 drawing.



In the Z-11 drawing the required devices are listed as Battery Contactor and 

Starter Contactor.



Are these animals the same with just different names or should I throw away 

the units I have and order new ones from B&C with the proper names just to 

be sure?



 	  Quote: 	
		  From what I can glean so far it looks like they are the same, they are all 

"contactors" just that one is continuous and one is intermittent. Is that 
	


correct?



Thank you,

Mike



---

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nuckollsr(at)cox.net
Guest

Posted: Fri Jan 05, 2007 7:28 am Post subject: Battery AND Starter Contactor?

At 05:48 AM 1/5/2007 -0900, you wrote:



 	  Quote: 	
		  



Bob,



Thanks for the explanation, I especially like your words, "This is a good 

example of how common vernacular can confuse the details about a parts 

functionality".



I am totally confused. I bought the Van's "Starter Solenoid" and "Master 

Relay" listed on page 82 of their accessories catalog and now I can't 

figure out if they are the same animals as what are required in the Z-11 

drawing.



In the Z-11 drawing the required devices are listed as Battery Contactor 

and Starter Contactor.



Are these animals the same with just different names or should I throw 

away the units I have and order new ones from B&C with the proper names 

just to be sure?



 From what I can glean so far it looks like they are the same, they are 

 all "contactors" just that one is continuous and one is intermittent. Is 

 that correct?



Thank you,

Mike


	


    Yes. It's not uncommon for contactors to be referred to as

    "solenoids" and they do indeed contain a solenoid for operation.

    Starter solenoids mounted directly on starters have double duty -

    the solenoid extends the pinion gear to mechanically engage the

    starter. At the same time, it makes electrical connection between

    the battery and starter motor by means of contacts in the same

    assembly. Here, the proper term for the device is starter solenoid.



    As soon as you pull it off the starter it becomes a fat relay more

    properly called a contactor.



    Bob  . . .

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aurbo(at)ak.net
Guest

Posted: Fri Jan 05, 2007 9:36 am Post subject: Battery AND Starter Contactor?

Bob,



Thank you kind sir.



Mike



---

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