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Starter contactors

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user9253

Joined: 28 Mar 2008
Posts: 1925
Location: Riley TWP Michigan

Posted: Sat Dec 17, 2011 12:47 pm Post subject: Starter contactors

My aircraft has a Rotax 912ULS engine with an 18 amp alternator.  I am considering adding lighting and additional avionics that would load the alternator to near maximum.  In an effort to conserve electricity, I am thinking about eliminating the main battery contactor similar to Z-17 or Z-20.  I am not familiar with the internal workings of the starter motor, but do not believe there is an internal solenoid that could be used to open the circuit.  My options are:

1.  Leave the circuit as is with a battery contactor.

2.  Remove the battery contactor and add a second starter contactor in series with the 	existing one.  The starter contactors would be energized by two side by side 	momentary push button switches.

3.  Remove the battery contactor and connect the starter contactor directly to the battery.



Option 3 is the simplest and lightest weight and least expensive.  But I am concerned about the starter contacts welding themselves shut with no way to shut off the power.

  Is the likelihood of the starter contactor failing closed, great enough to warrant the use of two contactors in series with the starter motor?

Joe

_________________
Joe Gores

jan_de_jong(at)casema.nl
Guest

Posted: Sat Dec 17, 2011 2:05 pm Post subject: Starter contactors

Joe,



There may be an option 4.

You might investigate using Tyco BDS-A as the battery contactor (attached).



Buy at Allied.

Plug and contacts at http://www.newunitedracetech.com

Somewhat expensive.

Search "AMP 184046".

Altogether say $60.



Regards,

Jan de Jong

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user9253

Joined: 28 Mar 2008
Posts: 1925
Location: Riley TWP Michigan

Posted: Sat Dec 17, 2011 3:12 pm Post subject: Re: Starter contactors

Jan de Jong,

Thanks for that information.  A latching relay has another failure mode to consider: failure to unlatch.  However a latching relay may be suitable for use in some situations.  I will keep it in mind.

Thanks for the link.

Joe

_________________
Joe Gores

klehman(at)albedo.net
Guest

Posted: Sat Dec 17, 2011 4:13 pm Post subject: Starter contactors

There is also the option of a manual battery switch. Could be used as a 

battery contactor substitute or just in series with the starter. Saw one 

the other day that only weighed a couple of oz. It was under $10. and 

rated for 200 amps.

Ken



On 17/12/2011 5:01 PM, Jan de Jong wrote:

 	  Quote: 	
		   Joe,



 There may be an option 4.

 You might investigate using Tyco BDS-A as the battery contactor (attached).



 Buy at Allied.

 Plug and contacts at http://www.newunitedracetech.com

 Somewhat expensive.

 Search "AMP 184046".

 Altogether say $60.



 Regards,

 Jan de Jong



 *Truncated!*

wtmills

Joined: 05 Feb 2007
Posts: 32

Posted: Sat Dec 17, 2011 7:09 pm Post subject: Starter contactors

I've considered the "Little Switch" on this page: http://www.flamingriver.com/batterydisconnect



Bill

SF bay area 

 Thinking Onex



On Sat, Dec 17, 2011 at 12:47 PM, user9253 <fran4sew(at)banyanol.com (fran4sew(at)banyanol.com)> wrote:

[quote] --> AeroElectric-List message posted by: "user9253" <fran4sew(at)banyanol.com (fran4sew(at)banyanol.com)>

 

 My aircraft has a Rotax 912ULS engine with an 18 amp alternator.  I am considering adding lighting and additional avionics that would load the alternator to near maximum.  In an effort to conserve electricity, I am thinking about eliminating the main battery contactor similar to Z-17 or Z-20.  I am not familiar with the internal workings of the starter motor, but do not believe there is an internal solenoid that could be used to open the circuit.  My options are:

  1.  Leave the circuit as is with a battery contactor.

 2.  Remove the battery contactor and add a second starter contactor in series with the  existing one.  The starter contactors would be energized by two side by side    momentary push button switches.

 3.  Remove the battery contactor and connect the starter contactor directly to the battery.

 

 Option 3 is the simplest and lightest weight and least expensive.  But I am concerned about the starter contacts welding themselves shut with no way to shut off the power.

   Is the likelihood of the starter contactor failing closed, great enough to warrant the use of two contactors in series with the starter motor?

 Joe

 

 --------

 Joe Gores

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=361107#361107[b]

jan_de_jong(at)casema.nl
Guest

Posted: Sun Dec 18, 2011 5:20 am Post subject: Starter contactors

A solid state loadswitch as starter contactor could also be an option 

(attached).

I would be inclined to make my own though by parallelling some BTS555.



Jan de Jong

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Dec 18, 2011 7:48 am Post subject: Starter contactors

At 09:05 PM 12/17/2011, you wrote:

  	  Quote: 	
		  I've considered the "Little Switch" on this page:  http://www.flamingriver.com/batterydisconnect 	


   This appears to be the same switch offered by Harbor Feight

   at a fraction of the cost . . .



  http://www.harborfreight.com/heavy-duty-battery-cutoff-switch-66789.html

 

 

 

   Bob . . .    [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Dec 18, 2011 7:53 am Post subject: Starter contactors

At 02:47 PM 12/17/2011, you wrote:

 	  Quote: 	
		  



My aircraft has a Rotax 912ULS engine with an 18 amp alternator.  I 

am considering adding lighting and additional avionics that would 

load the alternator to near maximum.


	


    Can you share your load analysis with us?



 	  Quote: 	
		  Option 3 is the simplest and lightest weight and least 

expensive.  But I am concerned about the starter contacts welding 

themselves shut with no way to shut off the power.

   Is the likelihood of the starter contactor failing closed, great 

 enough to warrant the use of two contactors in series with the starter motor?


	


    Not if you can climb out quickly and disconnect the battery

    without undue hazard. But the incidences of sticking starter

    contactors of the S704 variety are exceedingly rare.



    How about a battery switch and S704-1 style starter

    contactor.



    When you say your alternator is loaded to "near max" . . .

    under what conditions and for how long? Keep in mind

    that legacy design goals for engine driven power sources

    is to keep 20-25% of alternator capacity in reserve

    for battery replenishment.



    A load analysis of ENERGY requirements for various

    phases of flight might yield some less stressing

    facts about your night flight capabilities . . .

    ESPECIALLY with LED nav lights. Landing lights are

    a toss up . . . their current demand is high but

    the duty cycle can be exceedingly low. You don't

    really NEED light until you're in the flare.

   Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1925
Location: Riley TWP Michigan

Posted: Sun Dec 18, 2011 1:24 pm Post subject: Re: Starter contactors

 	  Quote: 	
		  Can you share your load analysis with us? 	


Aircraft load at present time



0.3A SL 40 com

1.6A GTX 327 X-PNDR

0.2A 496 GPS

1.5A Dynon D-180 EFIS

2.6A Autopilot w/ 2 servos

0.1A Intercom

0.5A Misc

0.7A Battery Contactor

1.5A Fuel Pump (continuous)

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

9A Total



3.5A  Proposed Dynon SkyView (additional 1.5A during backup battery charging)

3.2A Proposed 35W HID Landing light (continuous for collision avoidance)

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

15.7A New Total



The voltage regulator requires dedicated cooling at higher loads.

The Rotax 912ULS starts so quickly that main battery charging load is negligible.  The autopilot will not be turned on until after climbing to cruise altitude.  The battery will be charged by then.

I never fly at night, thus no position lights.

The electric fuel pump runs continuously per Van's RV-12 design.



 	  Quote: 	
		  How about a battery switch and S704-1 style starter contactor. 	


I assume that you meant to type S702-1 starter contactor.  I am reluctant to use a manual battery disconnect switch.  It would add another failure point to the electrical system.  In the event of a failed closed contactor, it would take me a minute or more to exit the plane and operate the battery switch.  The cost to buy a second starter contactor is not much more than a quality manual battery switch.

 	  Quote: 	
		  But the incidences of sticking starter contactors . . . are exceedingly rare. 	


That answers my question.

If it is not a safety of flight issue, I am inclined to keep the electrical system simple with one starter contactor connected directly to the battery and add an indicator light showing starter energized.

Thanks Bob, for the reply.

Joe

_________________
Joe Gores

jan_de_jong(at)casema.nl
Guest

Posted: Mon Dec 19, 2011 7:01 am Post subject: Starter contactors

Just a point of information.

According to Rotax 914 installation manual:

starter relay, 75 A, 300 A for 1 s, weighs 145 g (that is 5 ounces) and 

requires a fuse of 2 A.

Having 2, if required, would not be so bad.



Jan de Jong

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Dec 19, 2011 9:28 am Post subject: Starter contactors

I assume that you meant to type S702-1 starter contactor.



    Yes



I am reluctant to use a manual battery disconnect switch.  It would 

add another failure point to the electrical system.



    That's one of the risks mitigated by the dual

    feed endurance bus.



I assume that you meant to type S702-1 starter contactor.



    Yes



   I am reluctant to use a manual battery disconnect switch.  It 

would add another failure point to the electrical system.



    That's one of the risks mitigated by the dual

    feed endurance bus. Having a manually operated

    battery switch adds no new risks beyond those offere

    by the legacy battery master contactor.



In the event of a failed closed contactor, it would take me a minute 

or more to exit the plane and operate the battery switch.  The cost 

to buy a second starter contactor is not much more than a quality 

manual battery switch.



    Where is your battery located with respect to pilot

    access to a battery switch. What are your thoughts

    about battery disconnect before unplanned arrival

    with the earth?



    Here's another thought. If all of your electro-whizzies

    could be operated through a 7.5A or less fuse, then

    you could consider dispensing with the main bus entirely

    in favor of a 'super battery bus'. This would require that

    every device have it's own ON/OFF switch . . . with

    appropriate attention to shut-down-by-checklist to make

    sure the battery is available the next time you go

    flying. The starter contactor could be located next

    to the battery also.



    Bob . . .





   Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1925
Location: Riley TWP Michigan

Posted: Mon Dec 19, 2011 2:09 pm Post subject: Re: Starter contactors

The battery is located on the engine side of the firewall.  It can be reached through the oil-check door.

  I plan to use an automotive 20 or 30 amp relay in place of the master battery contactor.  However, starting current would not go through the relay.

  The starter contactor is located close to the battery.  My only concern is a failed closed starter contactor.  But that seems to be a remote possibility.  And if it ever happened, it would occur while on the ground.

  Thanks for all of the ideas and suggestions.

Joe

_________________
Joe Gores

user9253

Joined: 28 Mar 2008
Posts: 1925
Location: Riley TWP Michigan

Posted: Mon Dec 19, 2011 6:12 pm Post subject: Re: Starter contactors

I had a great idea.  Wire two starter contactors in series.  They will be energized by two momentary push button switches, one labeled and in plain sight on the panel, the other switch hidden.  When the barefoot bandit attempts to steal my plane, he will turn on the master and push the start button.  He will hear one contactor pull in and assume there is an electrical problem because the engine does not crank.  So he will go find another plane that someone left the key in.

  I will not need a key or an expensive key switch because only I will know how to start the engine (along with everyone else on Aeroelectric).  And I will not have to worry about losing the key or forgetting it.  Has anyone ever driven all of the way to the airport, only to realize the aircraft key was still at home?

Joe

_________________
Joe Gores

jan_de_jong(at)casema.nl
Guest

Posted: Tue Dec 20, 2011 2:04 am Post subject: Starter contactors

Hi Joe,

 	  Quote: 	
		   I had a great idea.  Wire two starter contactors in series.  They will be energized by two momentary push button switches, one labeled and in plain sight on the panel, the other switch hidden.  When the barefoot bandit attempts to steal my plane, he will turn on the master and push the start button.  He will hear one contactor pull in and assume there is an electrical problem because the engine does not crank.  So he will go find another plane that someone left the key in.

   I will not need a key or an expensive key switch because only I will know how to start the engine (along with everyone else on Aeroelectric).  And I will not have to worry about losing the key or forgetting it.  Has anyone ever driven all of the way to the airport, only to realize the aircraft key was still at home?

 Joe

   

Interesting.
	


1. You may need three pushbuttons (or more hands): two switches that 

individually should not work (test) and a third that operates both relays.

2. Light weight Rotax relays (if procured from Rotax) may not be cheap.

Regards,

Jan de Jong

trigo(at)mail.telepac.pt
Guest

Posted: Tue Dec 20, 2011 9:18 am Post subject: Starter contactors

Joe  

   

I hope no aircraft thief reads this, or he will look out for your other switch...  

Coudn’t resist..    

   

Good idea!  

   

Carlos  

   

DO NOT ARCHIVE  

   

[quote] --

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Tue Dec 20, 2011 5:34 pm Post subject: Starter contactors

Many aircraft do not have any keys.  Even aircraft down to the size of the

venerable DHC beaver.  Of course if you steal one of those you better know

what you are doing.



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

JLuckey(at)pacbell.net
Guest

Posted: Tue Dec 20, 2011 6:12 pm Post subject: Starter contactors

Save your money for the second solenoid - Just wire your 2 pushbuttons in

series for the solenoid coil.



--

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