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Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Sun Oct 27, 2013 7:52 am Post subject: Contactors

The requirement for a main battery contactor comes from the FAA's requirement to have the main battery disconnected "by one hand" in the event of a forced landing. Cutting off the main source of electrical energy should reduce the chance of ignition one supposes. 



NASCAR and various racing groups have the same problem but they usually have decided that a contactor failure is to be avoided by the elimination of electrical coil-type contactors, instead choosing rugged mechanical switches like "Flaming River Battery Switches".



So keep in mind: 



1) A contactor won't fail if you don't have one.

2) A contactor by regulations only has to open, not close. Sort of like a parachute.

3) Really big switches can be used instead of small switches and contactors. My Grandfather's Chevy had a starter footswitch. Still seems like a good idea.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

Bill Allen

Joined: 24 Aug 2009
Posts: 42
Location: UK

Posted: Mon Oct 28, 2013 12:44 pm Post subject: Contactors

Erics suggestion that a mechanical master switch be considered over a "solenoid" contactor seems to have merit.

On small OBAM aircraft one is always looking for ways to introduce a weight saving synergy.

  I am reworking the panel on my LongEz with a Dynon Skyview and can see that my current consumption will reduce using modern avionics.

  This then opens up the possibility of removing the 40amp alternator from the aft of my Lycoming (worst place for weight on a pusher) and replacing it with a 20amp unit in place of one magneto, and with a (B&C SD20) 20amp unit, one scrutinises all consumers to reduce appetites where possible.

 



While populating my electrical load schedule, I was taken aback to see that the master contactor takes a constant 2amps. That would make it the most hungry consumer of watts in my aircraft, 10% of my alternators output going to keep the master latched.

 



Thus I'm struggling to see why I should not use a mechanical master along the lines of that suggested by Eric; (http://www.flamingriver.com/index.php/products/c0015/s0001/FR1013) particularly as I'm at the "clean sheet" stage. And I've had an electrical master fail on a certified aircraft (PA30).

 



Am I missing something here?

Bill Allen

LongEz160

N99BA





On 27 October 2013 17:52, Eric M. Jones <emjones(at)charter.net (emjones(at)charter.net)> wrote:

 [quote]--> AeroElectric-List message posted by: "Eric M. Jones" <emjones(at)charter.net (emjones(at)charter.net)>

  

 The requirement for a main battery contactor comes from the FAA's requirement to have the main battery disconnected "by one hand" in the event of a forced landing. Cutting off the main source of electrical energy should reduce the chance of ignition one supposes.

  

 NASCAR and various racing groups have the same problem but they usually have decided that a contactor failure is to be avoided by the elimination of electrical coil-type contactors, instead choosing rugged mechanical switches like "Flaming River Battery Switches".

  

 So keep in mind:

 

 1) A contactor won't fail if you don't have one.

 2) A contactor by regulations only has to open, not close. Sort of like a parachute.

 3) Really big switches can be used instead of small switches and contactors. My Grandfather's Chevy had a starter footswitch. Still seems like a good idea.

 

 --------

 Eric M. Jones

 www.PerihelionDesign.com

 113 Brentwood Drive

 Southbridge, MA 01550

 (508) 764-2072

 emjones(at)charter.net

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=411531#411531

 

 

 

 

 

 

 

 ===========

 -List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

 ="_blank">http://www.matronics.com/contribution

 ===========

 

 

 

 [b]

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Mon Oct 28, 2013 1:01 pm Post subject: Re: Contactors

Bill,



Be aware that the main contactor is best replaced by a big switch in the same location. That is, a remote actuator (like a long actuator rod) is best. Flaming River sells these, but you can make one. Since flaps and ailerons and rudders, etc. use remote mechanical actuators, most builders can do something like this. 



Remember you only have to have the ability to turn OFF the battery.



Harbor Freight sells the big switches too. Roll your own actuator.



There comes a time in designing a big airplane when contactors are necessary, but small single engine homebuilts probably don't need them.



Since FAA regulations are to turn OFF the battery in an emergency, one might add some contacts to turn ON the ELT, turn off the fuel, etc. when one emergency T-handle is pulled.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Oct 29, 2013 1:19 am Post subject: Contactors

This then opens up the possibility of removing the 40amp alternator 

from the aft of my Lycoming (worst place for weight on a pusher) and 

replacing it with a 20amp unit in place of one magneto, and with a 

(B&C SD20) 20amp unit, one scrutinises all consumers to reduce 

appetites where possible.



    The B&C 20A machine drives from a vacuum

    pump pad. I don't think you want to replace

    any magnetos with other than an electronic

    ignition.

While populating my electrical load schedule, I was taken aback to 

see that the master contactor takes a constant 2amps. That would make 

it the most hungry consumer of watts in my aircraft, 10% of my 

alternators output going to keep the master latched.



  Actually, it's more like 1 amp cold and drops to about

  .6 amps warm for a Cole-Hersee contactor. See



http://tinyurl.com/k6bwdqo

http://tinyurl.com/mpcgp3t

Thus I'm struggling to see why I should not use a mechanical master 

along the lines of that suggested by Eric; 

(http://www.flamingriver.com/index.php/products/c0015/s0001/FR1013) 

particularly as I'm at the "clean sheet" stage. And I've had an 

electrical master fail on a certified aircraft (PA30).



   That works too. The Piper Pacer and Tri-Pacers

   were originally fitted with manual battery switches

   and starter push-buttons.



   How did the contactor fail . . . and how did

   you become aware of the failiure? If your

   system is architectured for failure tolerance,

   a contactor failure is not an emergency; only

   a maintenance event.

   Bob . . .

jan(at)CLAVER.DEMON.CO.UK
Guest

Posted: Tue Oct 29, 2013 1:35 pm Post subject: Contactors

What about using a Kilovac EV200 with a circuit saver ? Any experience with them ??  They pull in under high A.. then the circuit saver lowers the current to hold the relay closed… (but I am told the circuit saver is ‘noisy’ … i.e. lots of EMC …)  

   

Anyone have any comments ??  

         

  

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Bill Allen

 Sent: 29 October 2013 13:28

 To: aeroelectric-list(at)matronics.com

 Subject: Re: AeroElectric-List: Contactors  

  

     

Hi Bob,    

   

    

Thanks for the reply.  

    

   

    

1. Yes, well caught, the B&C SD20 fits on the vacpad not the mag location. My mis-type. - trying to colour in one point (the draw of the master relay) and not paying attention to the details.    I'm using a Pmag-E and an LSE as ignition systems.  

    

   

    

2. Your tests showing the real draw on the master solenoid are very revealing, presuming that the master solenoid I have from Aircraft Spruce (http://www.aircraftspruce.com/catalog/elpages/masterrelay.php?clickkey=10293 ) is a Cole-Hersee - I'm unfamiliar with the term but gather from googling that they are to solenoids what Hoover is to vacuum cleaners.  

    

However, 0.8amps is still almost the equivalent of a Garmin 430 (0.2a stby), Funkwerk Com (0.1a stby),DynonXPDR-262 (0.15a stby) and AeroLED Navlights (0.4a). All are "brochure figures" unless I've misread them.  

    

   

    

3. The failure I experienced on my PA30 was on the ground. I found a totally dead system with a good battery, and traced it quickly to the master relay not activating. A new unit fixed it, and upon stripping the old one, I found moisture penetration of the internals to be the cause. Cleaning it up got it working again, but not to the point that I wanted to risk the disruption it could cause if it failed again.  

    

Had it failed in flight I would not have lost engine power, but would have lost all ships power, unless there is an e-bus on a 1966 PA30 that I'm not aware of, which is possible.  

    

If you'd like me to mail it to you for dissection, I can do that.  

    

   

    

4. What I've learnt from this (ie, point 2 above) is to actually measure the current used by each of the consumers one plans to use. If the acceptance of 2amps for the master relay (but actually 0.8amps) is read across in this way for all other units, it's easily possible to end up with an alternator, wires, switches, fuses etc all way oversize and overweight.  

    

   

    

regards,  

    

   

    

Bill Allen  

  

    

     

On 29 October 2013 11:18, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:  

--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>    



 

 

  This then opens up the possibility of removing the 40amp alternator from the aft of my Lycoming (worst place for weight on a pusher) and replacing it with a 20amp unit in place of one magneto, and with a (B&C SD20) 20amp unit, one scrutinises all consumers to reduce appetites where possible.  

  

   The B&C 20A machine drives from a vacuum

    pump pad. I don't think you want to replace

    any magnetos with other than an electronic

    ignition.    



 

 

 While populating my electrical load schedule, I was taken aback to see that the master contactor takes a constant 2amps. That would make it the most hungry consumer of watts in my aircraft, 10% of my alternators output going to keep the master latched.  

  

 Actually, it's more like 1 amp cold and drops to about

  .6 amps warm for a Cole-Hersee contactor. See

 

 http://tinyurl.com/k6bwdqo

 http://tinyurl.com/mpcgp3t    



 

 

 Thus I'm struggling to see why I should not use a mechanical master along the lines of that suggested by Eric; (http://www.flamingriver.com/index.php/products/c0015/s0001/FR1013) particularly as I'm at the "clean sheet" stage. And I've had an electrical master fail on a certified aircraft (PA30).  

  

  That works too. The Piper Pacer and Tri-Pacers

   were originally fitted with manual battery switches

   and starter push-buttons.

 

   How did the contactor fail . . . and how did

   you become aware of the failiure? If your

   system is architectured for failure tolerance,

   a contactor failure is not an emergency; only

   a maintenance event.

 

 

   Bob . . .       



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

 -List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

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

 http://forums.matronics.com

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

 le, List Admin.

 ="_blank">http://www.matronics.com/contribution

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

 

 

   

  

  

  

   

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Oct 29, 2013 4:23 pm Post subject: Contactors

At 08:28 AM 10/29/2013, you wrote:

  	  Quote: 	
		  Hi Bob,



 Thanks for the reply.



 1. Yes, well caught, the B&C SD20 fits on the vacpad not the mag location. My mis-type. - trying to colour in one point (the draw of the master relay) and not paying attention to the details.    I'm using a Pmag-E and an LSE as ignition systems.

 	


   Okay, you've got a 15a current budget . . . 5A of

   rated output should be 'walled off' for battery

   recharging in flight . . . and remember, the SD-20

   doesn't give you any useful output until you're airborne.



  	  Quote: 	
		  2. Your tests showing the real draw on the master solenoid are very revealing, presuming that the master solenoid I have from Aircraft Spruce ( http://www.aircraftspruce.com/catalog/elpages/masterrelay.php?clickkey=10293  ) is a Cole-Hersee - I'm unfamiliar with the term but gather from googling that they are to solenoids what Hoover is to vacuum cleaners.

 However, 0.8amps is still almost the equivalent of a Garmin 430 (0.2a stby), Funkwerk Com (0.1a stby),DynonXPDR-262 (0.15a stby) and AeroLED Navlights (0.4a). All are "brochure figures" unless I've misread them. 	


   So do all the math. Get this form 



  http://tinyurl.com/7jqypwj



   and do an inventory of every electrical

   load . . . including the battery contactor.

   Don't fuss with bus-decisions yet, just

   get a read on total loads under various

   flight conditions.



 



  	  Quote: 	
		   

 3. The failure I experienced on my PA30 was on the ground. I found a totally dead system with a good battery, and traced it quickly to the master relay not activating. A new unit fixed it, and upon stripping the old one, I found moisture penetration of the internals to be the cause. Cleaning it up got it working again, but not to the point that I wanted to risk the disruption it could cause if it failed again.to 	


   Surely your anticipated system can function

   with the battery contactor open . . . whether

   it opens from failure or the fact that you

   shut it off, getting to an airport of intended

   destination shouldn't be a foreboding task.



  	  Quote: 	
		  Had it failed in flight I would not have lost engine power, but would have lost all ships power, unless there is an e-bus on a 1966 PA30 that I'm not aware of, which is possible. 	


   No, they don't have that feature . . . but if

   it were my airplane . . . it would.



   Do you have a flight-bag back-up?



  http://tinyurl.com/lg3n4gh



 



  	  Quote: 	
		  If you'd like me to mail it to you for dissection, I can do that. 	


   Not useful at this stage. The major point is that

   it failed on the ground.  I won't say that failures

   in fight never happen . . . but they are exceedingly

   rare. If one has failed in flight, I'd give pretty

   good odds that the pilot was 'warned' . . . probably

   conducted more than one flight where the contactor

   had to be 'jiggered' in some way before the panel lit

   up . . . and he doesn't even know what an e-bus is.



   I'd also give pretty good odds that the contactor

   you replaced had been in service for a considerable

   period of time.



   I'm supposed to get a networked computer at Cessna

   on Monday. I'd should be able to search the archives

   for history on part numbers used for both production

   and spares on the single engine line going back a

   very long way.



 

  	  Quote: 	
		  4. What I've learnt from this (ie, point 2 above) is to actually measure the current used by each of the consumers one plans to use. 	


   That's never wrong. When you get all the numbers, give

   us a list of your findings.



 

  	  Quote: 	
		   If the acceptance of 2amps for the master relay (but actually 0.8amps) is read across in this way for all other units, it's easily possible to end up with an alternator, wires, switches, fuses etc all way oversize and overweight. 	


   That's not typical. I've never seen a value greater

   than 1.0A assigned to battery contactors on single

   engine airplanes. Further, the numbers from installation

   manuals on items used in TC aircraft should be golden.

   Updating load analysis and weight and balance for

   any changes to an airplane is pretty much a given for

   which the manufacturer is obligated to support with

   good numbers.



   Add 'em all up and see if you've busted your 15A

   bubble. Running loads only, intermittent loads like

   flap motors, trim motors, transmitters, etc are

   not significant energy consumers.



 

   Bob . . .    [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Oct 29, 2013 4:30 pm Post subject: Contactors

At 04:44 PM 10/29/2013, you wrote:

  	  Quote: 	
		   What about using a Kilovac EV200 with a circuit saver ? Any experience with them ??  They pull in under high A.. then the circuit saver lowers the current to hold the relay closed… (but I am told the circuit saver is ‘noisy’ … i.e. lots of EMC …)

  

 Anyone have any comments ?? 	


   A fine contactor with a price to match . . .

   and yes . . . pwm management of holding

   current is not noise free. Most users

   have not found the noise to be a problem.

   I think I've got an EV200 in the skunk-werks

   box of goodies somewhere . . . if I can put

   my hands on it, I'll see if I can get the

   EMC lab gurus to do a quick conducted survey

   on it.



   We'll have a contactor-cooler product available

   pretty soon. The 9024 4-function module will

   include that capability. I'll it checked for

   conducted emissions too. The goal would be

   to offer a low cost alternative to lowering

   operating current (and temperature rise) on

   the generic contactors.  Reduced operating

   temp should improve on what has already been

   a good service life.



   But aside from weight and cost, the EV200 is

   a fine opportunity for increased service life

   assuming you find $value$ in the exchange.



 

   Bob . . .    [quote][b]

jan(at)CLAVER.DEMON.CO.UK
Guest

Posted: Thu Oct 31, 2013 10:41 am Post subject: Contactors

Hi Bob,  

   

It will be very interesting to hear what you find out about EMC if you get the chance to do it …  

   

I will be very interesting to hear more about your contactor cooler circuit / module when you have it available … will be ideal for a generic contactor   

   

All the best  

   

Jan  

         

  

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III

 Sent: 30 October 2013 00:30

 To: aeroelectric-list(at)matronics.com

 Subject: RE: AeroElectric-List: Contactors  

  

   

At 04:44 PM 10/29/2013, you wrote:

 

   

What about using a Kilovac EV200 with a circuit saver ? Any experience with them ??  They pull in under high A.. then the circuit saver lowers the current to hold the relay closed… (but I am told the circuit saver is ‘noisy’ … i.e. lots of EMC …)

  

 Anyone have any comments ??  



   A fine contactor with a price to match . . .

   and yes . . . pwm management of holding

   current is not noise free. Most users

   have not found the noise to be a problem.

   I think I've got an EV200 in the skunk-werks

   box of goodies somewhere . . . if I can put

   my hands on it, I'll see if I can get the

   EMC lab gurus to do a quick conducted survey

   on it.

 

   We'll have a contactor-cooler product available

   pretty soon. The 9024 4-function module will

   include that capability. I'll it checked for

   conducted emissions too. The goal would be

   to offer a low cost alternative to lowering

   operating current (and temperature rise) on

   the generic contactors.  Reduced operating

   temp should improve on what has already been

   a good service life.

 

   But aside from weight and cost, the EV200 is

   a fine opportunity for increased service life

   assuming you find $value$ in the exchange.

 

 

     

  Bob . . .    	  Quote: 	
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Bill Allen

Joined: 24 Aug 2009
Posts: 42
Location: UK

Posted: Thu Oct 31, 2013 1:27 pm Post subject: Contactors

Hi Bob,

You wrote;



 

  <<Okay, you've got a 15a current budget . . . 5A of   rated output should be 'walled off' for battery  recharging in flight . . . and remember, the SD-20   doesn't give you any useful output until you're airborne.>>

Noted. 

  << So do all the math. Get this form http://tinyurl.com/7jqypwj and do an inventory of every electrical load . . . including the battery contactor.Don't fuss with bus-decisions yet, just get a read on total loads under various flight conditions.>>

 



Got the form. Willdo.<<Surely your anticipated system can function with the battery contactor open . . . whether   it opens from failure or the fact that you shut it off, getting to an airport of intended destination shouldn't be a foreboding task.>>

 



Presumably that's what the e-bus is there for in your designs, if not the architecture of Mr.Piper in 1966, when my PA30 was built.

 



  << Do you have a flight-bag back-up? http://tinyurl.com/lg3n4gh >>  Yes I do.

 



 << I'd also give pretty good odds that the contactor you replaced had been in service for a considerable period of time >>

 



I have no reason to doubt it was new with the aircraft, in 1966.    What I've learnt from this is to actually measure the current used by each of the consumers one plans to use. 



  <<That's never wrong. When you get all the numbers, give   us a list of your findings. Add 'em all up and see if you've busted your 15A

   bubble. Running loads only, intermittent loads like  flap motors, trim motors, transmitters, etc are   not significant energy consumers.>>

 



Will do.



 

Thanks.

 Bill Allen



 	  Quote: 	
		   

	




  





On 30 October 2013 02:22, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 [quote]  At 08:28 AM 10/29/2013, you wrote:

  	  Quote: 	
		  Hi Bob,



 Thanks for the reply.



 1. Yes, well caught, the B&C SD20 fits on the vacpad not the mag location. My mis-type. - trying to colour in one point (the draw of the master relay) and not paying attention to the details.    I'm using a Pmag-E and an LSE as ignition systems.

 	




   Okay, you've got a 15a current budget . . . 5A of

   rated output should be 'walled off' for battery

   recharging in flight . . . and remember, the SD-20

   doesn't give you any useful output until you're airborne.



  	  Quote: 	
		  2. Your tests showing the real draw on the master solenoid are very revealing, presuming that the master solenoid I have from Aircraft Spruce ( http://www.aircraftspruce.com/catalog/elpages/masterrelay.php?clickkey=10293  ) is a Cole-Hersee - I'm unfamiliar with the term but gather from googling that they are to solenoids what Hoover is to vacuum cleaners.

 However, 0.8amps is still almost the equivalent of a Garmin 430 (0.2a stby), Funkwerk Com (0.1a stby),DynonXPDR-262 (0.15a stby) and AeroLED Navlights (0.4a). All are "brochure figures" unless I've misread them.

	


   So do all the math. Get this form 



  http://tinyurl.com/7jqypwj



   and do an inventory of every electrical

   load . . . including the battery contactor.

   Don't fuss with bus-decisions yet, just

   get a read on total loads under various

   flight conditions.



 



  	  Quote: 	
		   

 3. The failure I experienced on my PA30 was on the ground. I found a totally dead system with a good battery, and traced it quickly to the master relay not activating. A new unit fixed it, and upon stripping the old one, I found moisture penetration of the internals to be the cause. Cleaning it up got it working again, but not to the point that I wanted to risk the disruption it could cause if it failed again.to 	


   Surely your anticipated system can function

   with the battery contactor open . . . whether

   it opens from failure or the fact that you

   shut it off, getting to an airport of intended

   destination shouldn't be a foreboding task.



  	  Quote: 	
		  Had it failed in flight I would not have lost engine power, but would have lost all ships power, unless there is an e-bus on a 1966 PA30 that I'm not aware of, which is possible. 	




   No, they don't have that feature . . . but if

   it were my airplane . . . it would.



   Do you have a flight-bag back-up?



  http://tinyurl.com/lg3n4gh



 



  	  Quote: 	
		  If you'd like me to mail it to you for dissection, I can do that. 	




   Not useful at this stage. The major point is that

   it failed on the ground.  I won't say that failures

   in fight never happen . . . but they are exceedingly

   rare. If one has failed in flight, I'd give pretty

   good odds that the pilot was 'warned' . . . probably

   conducted more than one flight where the contactor

   had to be 'jiggered' in some way before the panel lit

   up . . . and he doesn't even know what an e-bus is.



   I'd also give pretty good odds that the contactor

   you replaced had been in service for a considerable

   period of time.



   I'm supposed to get a networked computer at Cessna

   on Monday. I'd should be able to search the archives

   for history on part numbers used for both production

   and spares on the single engine line going back a

   very long way.



 

  	  Quote: 	
		  4. What I've learnt from this (ie, point 2 above) is to actually measure the current used by each of the consumers one plans to use. 	




   That's never wrong. When you get all the numbers, give

   us a list of your findings.



 

  	  Quote: 	
		   If the acceptance of 2amps for the master relay (but actually 0.8amps) is read across in this way for all other units, it's easily possible to end up with an alternator, wires, switches, fuses etc all way oversize and overweight. 	




   That's not typical. I've never seen a value greater

   than 1.0A assigned to battery contactors on single

   engine airplanes. Further, the numbers from installation

   manuals on items used in TC aircraft should be golden.

   Updating load analysis and weight and balance for

   any changes to an airplane is pretty much a given for

   which the manufacturer is obligated to support with

   good numbers.



   Add 'em all up and see if you've busted your 15A

   bubble. Running loads only, intermittent loads like

   flap motors, trim motors, transmitters, etc are

   not significant energy consumers.



 

   Bob . . .     	  Quote: 	
		  



ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

tp://forums.matronics.com

_blank">http://www.matronics.com/contribution



	


[b]

mapratherid(at)gmail.com
Guest

Posted: Thu Oct 31, 2013 3:16 pm Post subject: Contactors

Seems like the relay (contactor) that draws 0.8-2A (depending on how it's measured) is one that is sized to be capable of carrying starter currents (though not necessarily capable of switching them reliably).  An architecture that uses such a contactor for all devices is probably fine when you have 40A+ to play with.  But, in an application where you're on a tight energy budget, maybe it would make sense to have parallel contactors/relays.   A smaller relay might be able to handle everything but starting current, and only consume 100-200mA to do it. The heavy one would only be energized when starting the engine.  It may break the architecture goal of running the B-lead current through the heavy starter wire, but that may still be a good deal. 



Regards,

Matt-



On Thu, Oct 31, 2013 at 3:26 PM, Bill Allen <billallensworld(at)gmail.com (billallensworld(at)gmail.com)> wrote:

 [quote]Hi Bob,

You wrote;

 

 

  <<Okay, you've got a 15a current budget . . . 5A of    rated output should be 'walled off' for battery  recharging in flight . . . and remember, the SD-20    doesn't give you any useful output until you're airborne.>>

Noted.  

  << So do all the math. Get this form http://tinyurl.com/7jqypwj and do an inventory of every electrical load . . . including the battery contactor.Don't fuss with bus-decisions yet, just get a read on total loads under various flight conditions.>>

  



Got the form. Willdo.<<Surely your anticipated system can function with the battery contactor open . . . whether    it opens from failure or the fact that you shut it off, getting to an airport of intended destination shouldn't be a foreboding task.>>

  



Presumably that's what the e-bus is there for in your designs, if not the architecture of Mr.Piper in 1966, when my PA30 was built.

  



  << Do you have a flight-bag back-up? http://tinyurl.com/lg3n4gh >>  Yes I do.

  



 << I'd also give pretty good odds that the contactor you replaced had been in service for a considerable period of time >>

  



I have no reason to doubt it was new with the aircraft, in 1966.     What I've learnt from this is to actually measure the current used by each of the consumers one plans to use.  



  <<That's never wrong. When you get all the numbers, give    us a list of your findings. Add 'em all up and see if you've busted your 15A

    bubble. Running loads only, intermittent loads like  flap motors, trim motors, transmitters, etc are    not significant energy consumers.>>

  



Will do.

 

 

Thanks.

  Bill Allen



 	  Quote: 	
		   

	




   





On 30 October 2013 02:22, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

   	  Quote: 	
		    At 08:28 AM 10/29/2013, you wrote:

  	  Quote: 	
		  Hi Bob,



 Thanks for the reply.



 1. Yes, well caught, the B&C SD20 fits on the vacpad not the mag location. My mis-type. - trying to colour in one point (the draw of the master relay) and not paying attention to the details.    I'm using a Pmag-E and an LSE as ignition systems.

 	


   Okay, you've got a 15a current budget . . . 5A of

   rated output should be 'walled off' for battery

   recharging in flight . . . and remember, the SD-20

   doesn't give you any useful output until you're airborne.



  	  Quote: 	
		  2. Your tests showing the real draw on the master solenoid are very revealing, presuming that the master solenoid I have from Aircraft Spruce ( http://www.aircraftspruce.com/catalog/elpages/masterrelay.php?clickkey=10293  ) is a Cole-Hersee - I'm unfamiliar with the term but gather from googling that they are to solenoids what Hoover is to vacuum cleaners.

 However, 0.8amps is still almost the equivalent of a Garmin 430 (0.2a stby), Funkwerk Com (0.1a stby),DynonXPDR-262 (0.15a stby) and AeroLED Navlights (0.4a). All are "brochure figures" unless I've misread them.



	


   So do all the math. Get this form 



  http://tinyurl.com/7jqypwj



   and do an inventory of every electrical

   load . . . including the battery contactor.

   Don't fuss with bus-decisions yet, just

   get a read on total loads under various

   flight conditions.



 



  	  Quote: 	
		   

 3. The failure I experienced on my PA30 was on the ground. I found a totally dead system with a good battery, and traced it quickly to the master relay not activating. A new unit fixed it, and upon stripping the old one, I found moisture penetration of the internals to be the cause. Cleaning it up got it working again, but not to the point that I wanted to risk the disruption it could cause if it failed again.to 	


   Surely your anticipated system can function

   with the battery contactor open . . . whether

   it opens from failure or the fact that you

   shut it off, getting to an airport of intended

   destination shouldn't be a foreboding task.



  	  Quote: 	
		  Had it failed in flight I would not have lost engine power, but would have lost all ships power, unless there is an e-bus on a 1966 PA30 that I'm not aware of, which is possible. 	


   No, they don't have that feature . . . but if

   it were my airplane . . . it would.



   Do you have a flight-bag back-up?



  http://tinyurl.com/lg3n4gh



 



  	  Quote: 	
		  If you'd like me to mail it to you for dissection, I can do that. 	


   Not useful at this stage. The major point is that

   it failed on the ground.  I won't say that failures

   in fight never happen . . . but they are exceedingly

   rare. If one has failed in flight, I'd give pretty

   good odds that the pilot was 'warned' . . . probably

   conducted more than one flight where the contactor

   had to be 'jiggered' in some way before the panel lit

   up . . . and he doesn't even know what an e-bus is.



   I'd also give pretty good odds that the contactor

   you replaced had been in service for a considerable

   period of time.



   I'm supposed to get a networked computer at Cessna

   on Monday. I'd should be able to search the archives

   for history on part numbers used for both production

   and spares on the single engine line going back a

   very long way.



 

  	  Quote: 	
		  4. What I've learnt from this (ie, point 2 above) is to actually measure the current used by each of the consumers one plans to use. 	


   That's never wrong. When you get all the numbers, give

   us a list of your findings.



 

  	  Quote: 	
		   If the acceptance of 2amps for the master relay (but actually 0.8amps) is read across in this way for all other units, it's easily possible to end up with an alternator, wires, switches, fuses etc all way oversize and overweight. 	


   That's not typical. I've never seen a value greater

   than 1.0A assigned to battery contactors on single

   engine airplanes. Further, the numbers from installation

   manuals on items used in TC aircraft should be golden.

   Updating load analysis and weight and balance for

   any changes to an airplane is pretty much a given for

   which the manufacturer is obligated to support with

   good numbers.



   Add 'em all up and see if you've busted your 15A

   bubble. Running loads only, intermittent loads like

   flap motors, trim motors, transmitters, etc are

   not significant energy consumers.



 

   Bob . . .     	  Quote: 	
		  



ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

tp://forums.matronics.com

_blank">http://www.matronics.com/contribution



	


	


   	  Quote: 	
		  



ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

tp://forums.matronics.com

_blank">http://www.matronics.com/contribution



	




[b]

uuccio(at)gmail.com
Guest

Posted: Thu Oct 31, 2013 9:12 pm Post subject: Contactors

I use automotive "cube" relays (one for the master relay, one for alternator) rated at 70A. They are light and consume less than 300mA each. Is there a reason not to use them?  The only potential drawback I'm aware of is that they can break the contact if subject to violent shocks. But loosing panel power for a few milliseconds doesn't seem such a big issue (the autopilot does reset but then in such violent turbulence you might be hand flying the thing in any case, and the GNS430 doesn't even notice any absence of power that lasts that little). 



Are there other risks I am not considering here? This is a VFR only machine and I'm a low time PPL so not the most experienced in these matters. 



Sacha

bob.verwey(at)gmail.com
Guest

Posted: Thu Oct 31, 2013 9:21 pm Post subject: Contactors

Sacha,I have used one of these Bosch 70amp relays for the master in my experimental Bonanza for the past 8 years - rock solid! I still use the caveman relay for the starter.

Bob Verwey

 A35 ZU-DLW



On 1 November 2013 07:10, Sacha <uuccio(at)gmail.com (uuccio(at)gmail.com)> wrote:

 [quote]--> AeroElectric-List message posted by: Sacha <uuccio(at)gmail.com (uuccio(at)gmail.com)>

 

 I use automotive "cube" relays (one for the master relay, one for alternator) rated at 70A. They are light and consume less than 300mA each. Is there a reason not to use them?  The only potential drawback I'm aware of is that they can break the contact if subject to violent shocks. But loosing panel power for a few milliseconds doesn't seem such a big issue (the autopilot does reset but then in such violent turbulence you might be hand flying the thing in any case, and the GNS430 doesn't even notice any absence of power that lasts that little).

  

 Are there other risks I am not considering here? This is a VFR only machine and I'm a low time PPL so not the most experienced in these matters.

 

 Sacha

 

 ===========

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 le, List Admin.

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 http://forums.matronics.com

 

 

 

 [b]

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Nov 01, 2013 4:38 am Post subject: Contactors

At 12:10 AM 11/1/2013, you wrote:

 	  Quote: 	
		  



I use automotive "cube" relays (one for the master relay, one for 

alternator) rated at 70A. They are light and consume less than 300mA 

each. Is there a reason not to use them?  The only potential 

drawback I'm aware of is that they can break the contact if subject 

to violent shocks. But loosing panel power for a few milliseconds 

doesn't seem such a big issue (the autopilot does reset but then in 

such violent turbulence you might be hand flying the thing in any 

case, and the GNS430 doesn't even notice any absence of power that 

lasts that little).



Are there other risks I am not considering here? This is a VFR only 

machine and I'm a low time PPL so not the most experienced in these matters.


	


   The legacy battery contactor is tasked with

   carrying normal operating loads usually in

   the tens of amps but predicated on getting an

   engine started . . . loads of perhaps 200A.



   Hence the selection of contactors that seem

   unnecessarily oversized to the task. But the

   one device can do it all. Some of the designs

   we're considering DO add smaller relays which

   function as a mini-contactor to handle loads

   other than starting and/or battery recharging.



   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Nov 01, 2013 4:38 am Post subject: Contactors

At 12:21 AM 11/1/2013, you wrote:

 	  Quote: 	
		  Sacha,

I have used one of these Bosch 70amp relays for the master in my 

experimental Bonanza for the past 8 years - rock solid! I still use 

the caveman relay for the starter.



Bob Verwey

A35 ZU-DLW


	


   But you don't crank the engine through it do you?



   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Nov 01, 2013 4:55 am Post subject: Contactors

From my newly acquired perch within the halls

of Cessna Engineering I've discovered that the

battery and starter contactors used on the single

engine fleet have pretty much always been in the

same style and ratings as the Cole-Hersee, RBM,

Stancore, White-Rogers devices we've been discussing

here on the List.



Before the Great Shut-Down, Cessna purchased individual

contactors for installation on the line. After the

Great Resurrection, the contactors came to Cessna as

part of a power distribution box mounting up to

4 such contactors. Battery, starter, alternator, ground-

power. Of course, they're all 24 volt devices.



During my earlier tenure at Cessna (64-69) the starter

contactors were a low-duty cycle version of the battery

contactor. They left something to be desired as SWITCHING

devices for starter currents. I suspect that the

modern starter contactors have exploited discoveries

common to contemporary automotive starter contactors

for small area, very high pressure contacts.



http://tinyurl.com/96wy5mq



Yes, there have been some serviceability issues managed

by some modifications to the contact materials, springs,

etc. etc. But the general configuration of the modern

contactor has changed little since 1948. But in particular,

there's no reason to believe that the modern encarnation

of the 70 series device is any less suited to task

as a battery contactor than it has been for many years.



I dug up a 1960 copy of an Allied Electronics catalog

hoping to discover the price of these devices back then.

They don't appear in that catalog.



   Bob . . .

uuccio(at)gmail.com
Guest

Posted: Fri Nov 01, 2013 9:34 am Post subject: Contactors

 	  Quote: 	
		  >> Sacha,

>> I have used one of these Bosch 70amp relays for the master in my experimental Bonanza for the past 8 years - rock solid! I still use the caveman relay for the starter.

>> 

>> Bob Verwey

>> A35 ZU-DLW

> 

Thanks Bob V for the validation.
	




 	  Quote: 	
		  >  But you don't crank the engine through it do you?


	


No, the starter contactor is not the automotive type.

uuccio(at)gmail.com
Guest

Posted: Fri Nov 01, 2013 9:45 am Post subject: Contactors

On Nov 1, 2013, at 13:37, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com> wrote:



 	  Quote: 	
		   

 

 At 12:10 AM 11/1/2013, you wrote:

> 

> 

> I use automotive "cube" relays (one for the master relay, one for alternator) rated at 70A. They are light and consume less than 300mA each. Is there a reason not to use them?  The only potential drawback I'm aware of is that they can break the contact if subject to violent shocks. But loosing panel power for a few milliseconds doesn't seem such a big issue (the autopilot does reset but then in such violent turbulence you might be hand flying the thing in any case, and the GNS430 doesn't even notice any absence of power that lasts that little).

> 

> Are there other risks I am not considering here? This is a VFR only machine and I'm a low time PPL so not the most experienced in these matters.

 

  The legacy battery contactor is tasked with

  carrying normal operating loads usually in

  the tens of amps but predicated on getting an

  engine started . . . loads of perhaps 200A.


	


Ah. Ok now I understand your previous question. In my case the fat wire to the starter contactor is always hot. The master just activates the coil circuit. 



I now know this is against conventional design where master OFF is supposed to correspond to max darkness. In my case the total length of fat (positive) wire is approx 50cm (20"): battery to starter contactor to starter motor.

peter(at)sportingaero.com
Guest

Posted: Sat Nov 02, 2013 1:17 am Post subject: Contactors

There is a potential problem in using only the starter contactor to 

switch the starter motor power - those contactors are known to 

occasionally weld themselves together. In that case, with only the 

starter contactor switching power to the starter, there is then no way 

of disengaging it from the running engine until the battery is flat (if 

that ever happens as the starter is now a generator). In the UK the 

authorities insist that a light is installed in the panel warning the 

pilot the starter remains energised, as there have been several 

accidents. The engaged starter saps a large amount of power from the 

engine and gets very hot, with unpleasant consequences.



If a modern starter with a piggy-back solenoid is fitted, to avoid the 

master relay handling the starting current, the jumper that normally 

energises the solenoid can be brought into a cockpit switch to disable 

the starter if the the starter contactor does weld on. A small 

additional parts count, but the switch never does any switching except 

in emergency.



Peter



On 01/11/2013 17:44, Sacha wrote:

 	  Quote: 	
		   



 On Nov 1, 2013, at 13:37, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com> wrote:



> 

>

> At 12:10 AM 11/1/2013, you wrote:

>> 

>>

>> I use automotive "cube" relays (one for the master relay, one for alternator) rated at 70A. They are light and consume less than 300mA each. Is there a reason not to use them?  The only potential drawback I'm aware of is that they can break the contact if subject to violent shocks. But loosing panel power for a few milliseconds doesn't seem such a big issue (the autopilot does reset but then in such violent turbulence you might be hand flying the thing in any case, and the GNS430 doesn't even notice any absence of power that lasts that little).

>>

>> Are there other risks I am not considering here? This is a VFR only machine and I'm a low time PPL so not the most experienced in these matters.

>   The legacy battery contactor is tasked with

>   carrying normal operating loads usually in

>   the tens of amps but predicated on getting an

>   engine started . . . loads of perhaps 200A.

 Ah. Ok now I understand your previous question. In my case the fat wire to the starter contactor is always hot. The master just activates the coil circuit.



 I now know this is against conventional design where master OFF is supposed to correspond to max darkness. In my case the total length of fat (positive) wire is approx 50cm (20"): battery to starter contactor to starter motor.

uuccio(at)gmail.com
Guest

Posted: Sat Nov 02, 2013 4:45 am Post subject: Contactors

 

There is a potential problem in using only the starter contactor to switch the starter motor power - those contactors are known to occasionally weld themselves together. In that case, with only the starter contactor switching power to the starter, there is then no way of disengaging it from the running engine until the battery is flat (if that ever happens as the starter is now a generator). In the UK the authorities insist that a light is installed in the panel warning the pilot the starter remains energised, as there have been several accidents. The engaged starter saps a large amount of power from the engine and gets very hot, with unpleasant consequences.  

  

Good point, I hadn’t thought of that failure mode.  

  

If a modern starter with a piggy-back solenoid is fitted, to avoid the master relay handling the starting current, the jumper that normally energises the solenoid can be brought into a cockpit switch to disable the starter if the the starter contactor does weld on. A small additional parts count, but the switch never does any switching except in emergency.  

  

You’re speaking about the solenoid on the starter motor?  I don’t recall seeing any external jumper there (the engine is a Rotax 912).  I'll have a check next time I’m down at the hangar.   

     [quote][b]

uuccio(at)gmail.com
Guest

Posted: Sat Nov 02, 2013 1:11 pm Post subject: Contactors

 	  Quote: 	
		  >        If a modern starter with a piggy-back solenoid is fitted,

> to avoid the master relay handling the starting current, the jumper that

> normally energises the solenoid can be brought into a cockpit switch to

> disable the starter if the the starter contactor does weld on. A small

> additional parts count, but the switch never does any switching except in

> emergency.

 

 You're speaking about the solenoid on the starter motor?  I don't recall

 seeing any external jumper there (the engine is a Rotax 912).  I'll have a

 check next time I'm down at the hangar.  


	


I couldn't find anything there unfortunately. The starter motor just has one terminal for the fat positive wire.

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