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Is a battery contactor really needed?

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rv8ch

Joined: 10 Jan 2006
Posts: 250
Location: Switzerland

Posted: Wed Apr 12, 2017 12:35 pm Post subject: Is a battery contactor really needed?

There seem to be a lot of advantages to not disconnecting the alternator from the battery, so I'm wondering if the battery contactor is really necessary?



The things I can see as advantages are that it provides an extra layer of protection from accidental starter engagement, and provides a big switch that can be used to disconnect the battery from everything.



I'm curious if there are other advantages that I'm not seeing.



Thanks!

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Mickey Coggins
http://www.rv8.ch/

user9253

Joined: 28 Mar 2008
Posts: 1922
Location: Riley TWP Michigan

Posted: Wed Apr 12, 2017 3:08 pm Post subject: Re: Is a battery contactor really needed?

In case of an immanent forced landing or smoke in the cockpit, it is advisable to shut off electrical power as close to the source as possible.

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Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Apr 13, 2017 12:43 pm Post subject: Is a battery contactor really needed?

At 03:35 PM 4/12/2017, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "rv8ch" <mick-matronics(at)rv8.ch>



 There seem to be a lot of advantages to not disconnecting the alternator from the battery, so I'm wondering if the battery contactor is really necessary?



 The things I can see as advantages are that it provides an extra layer of protection from accidental starter engagement, and provides a big switch that can be used to disconnect the battery from everything.



 I'm curious if there are other advantages that I'm not seeing. 	




   There is a legacy train of thought that goes

   back nearly 100 years . . . when on short final

   to the rocks, it's a good idea to suppress

   risk to the smallest values.



   Hence, the POH for most if not all TC aircraft

   calls for shutting off the fuel and killing

   the electrical system. Getting the electrical

   system stone-cold calls for independent, positive

   control over power sources like alternators, generators

   and . . . you guessed it . . . batteries.



   Of course, the contactor is also a hedge against

   a stuck starter contactor . . .



   Don't know what 'advantages' might be secured

   with permanent pathways between alternators

   and batteries.



 



 

   Bob . . .

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rv8ch

Joined: 10 Jan 2006
Posts: 250
Location: Switzerland

Posted: Thu Apr 13, 2017 8:26 pm Post subject: Re: Is a battery contactor really needed?

 	  nuckolls.bob(at)aeroelect wrote: 	
		  At 03:35 PM 4/12/2017, you wrote:

   Don't know what 'advantages' might be secured

   with permanent pathways between alternators

   and batteries. 	
Thanks for the feedback gents, looks like the off field landing scenario slipped my mind when thinking about this.  The "advantages" I was thinking of were one less component, and the possible avoidance of a load dump if the alternator is pumping hard and the battery is disconnected.  Avoiding issues with a load dump are pretty easy by following the recommended designs in the 'connection.  Thanks for the tips!

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Mickey Coggins
http://www.rv8.ch/

trigo(at)mail.telepac.pt
Guest

Posted: Fri Apr 14, 2017 5:51 am Post subject: Is a battery contactor really needed?

Hello Mickey

I suppose everything is ok with you and your family, and you are flying your RV-8 in beautiful Switzerland 

Cheers

Carlos

Enviado do meu iPhone

No dia 14/04/2017, às 05:26, rv8ch <mick-matronics(at)rv8.ch> escreveu:

 	  Quote: 	

 nuckolls.bob(at)aeroelect wrote:

> At 03:35 PM 4/12/2017, you wrote:

>   Don't know what 'advantages' might be secured

>   with permanent pathways between alternators

>   and batteries.

 Thanks for the feedback gents, looks like the off field landing scenario slipped my mind when thinking about this.  The "advantages" I was thinking of were one less component, and the possible avoidance of a load dump if the alternator is pumping hard and the battery is disconnected.  Avoiding issues with a load dump are pretty easy by following the recommended designs in the 'connection.  Thanks for the tips!

 --------

 Mickey Coggins

 http://www.rv8.ch/

 Read this topic online here:

 http://forums.matronics.com/viewtopic.php?p=468379#468379

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eschlanser

Joined: 08 Apr 2010
Posts: 60

Posted: Wed Apr 26, 2017 6:39 am Post subject: Re: Is a battery contactor really needed?

It's been a couple of years since I designed my plane's electrical system with no battery contactor.



What brand or style battery contactor is preferred/acceptable for a OBAM airplane with a Z - (x) wiring system? I installed the barrel style starter contactor but replaced it with the flat style when Bob recommended that change. Now I'm wondering if there's a new style of battery contactor that has superseded the barrel style.



One advantage to eliminating the battery contactor is keeping the voltage available for starting that would be lost to the battery contactor.



Eric - W10 with Z-8 inspired elec system.[/u]

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