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Solid State Master Relay

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jmjones2000(at)mindspring
Guest

Posted: Wed Nov 19, 2014 2:05 pm Post subject: Solid State Master Relay

I purchased the following solid state master relay to use in my project.  It is designed to be used as an ambulance master relay.

http://www.waytekwire.com/item/44407/300-AMP-SOLID-STATE-BATTERY/



I am wondering what the typical inrush and cranking amperage is to the Skytec starters for the Lycoming IO-360.  I am contemplating wiring the starter from the battery, through the relay and to the starter rather than connecting it thru the Battery Master Switch.  It would seem that limiting the high amounts of current that the starter draws would prolong the already long life of these solid state devices.  The maximum rating for this relay is 500A for one second.  Over the years, I have experienced numerous master relay failures, and I am anxious to try this out.  The link to the data sheet is below.

http://www.waytekwire.com/datasheet/44407.pdf



One other option I considered is to wire the starter from the battery, to a manual disconnect (such as one in the links below), then through the starter relay, thence the starter.  One could attach a push-pull cable or rod to the armature of this switch, and easily disconnect the battery from the starter while sitting in the cockpit in the unlikely event of the starter contacts getting welded together, or the starter relay fails closed.  This switch should probably be located as close to the battery as possible.



http://www.jegs.com/i/Flaming+River/898/FR1006/10002/-1

http://www.jegs.com/i/Flaming+River/898/FR1003-1/10002/-1

http://www.jegs.com/i/Moroso/710/74105/10002/-1

http://www.jegs.com/i/Unisteer/668/8070030/10002/-1

http://www.jegs.com/i/Unisteer/668/8070040/10002/-1



Thoughts are welcome



Justin 

 [quote][b]

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jluckey(at)pacbell.net
Guest

Posted: Wed Nov 19, 2014 5:02 pm Post subject: Solid State Master Relay

Justin,



I'm curious about the decision process that lead to selecting the solid-state relay.  I see some down side:

 

1. Cost - that relay is 4 or 5 times the price of an equivalent mechanical device

2. Power dissipation - That's a pretty hefty heat-sink.  How much power does it need to dissipate

3. I wonder if it is heavier that a mechanical - I didn't see a weight spec.

4. "Proven technology" - How much track record is there for this device?  (I compare this against the standard Master relays with a 50+ year history.)



This is the Master Relay I'm using (I like it because it's lightweight, small, low coil current, & reasonable cost): http://tinyurl.com/nb72gal



Re wiring starter directly:

That's what I'm doing in my RV-7.  Battery to start-assist solenoid to starter.  BobN just made a post in the last couple of days re this topic and I concur w/ his thoughts.  Basically a hung start-assist solenoid is such a rare event that I don't worry about it.



A couple of questions:1. Which airplane are you building?

2. Tell us about your master relay failures.  What aircraft? which relay/contactor?

Please  understand that my intent is not to be critical but rather to  understand how you reached your conclusions. (I might learn something.)

-Jeff



 

     On Wednesday, November 19, 2014 2:16 PM, Justin Jones <jmjones2000(at)mindspring.com> wrote:  

   I purchased the following solid state master relay to use in my project.  It is designed to be used as an ambulance master relay.

http://www.waytekwire.com/item/44407/300-AMP-SOLID-STATE-BATTERY/



I am wondering what the typical inrush and cranking amperage is to the Skytec starters for the Lycoming IO-360.  I am contemplating wiring the starter from the battery, through the relay and to the starter rather than connecting it thru the Battery Master Switch.  It would seem that limiting the high amounts of current that the starter draws would prolong the already long life of these solid state devices.  The maximum rating for this relay is 500A for one second.  Over the years, I have experienced numerous master relay failures, and I am anxious to try this out.  The link to the data sheet is below.

http://www.waytekwire.com/datasheet/44407.pdf



One other option I considered is to wire the starter from the battery, to a manual disconnect (such as one in the links below), then through the starter relay, thence the starter.  One could attach a push-pull cable or rod to the armature of this switch, and easily disconnect the battery from the starter while sitting in the cockpit in the unlikely event of the starter contacts getting welded together, or the starter relay fails closed.  This switch should probably be located as close to the battery as possible.



http://www.jegs.com/i/Flaming+River/898/FR1006/10002/-1

http://www.jegs.com/i/Flaming+River/898/FR1003-1/10002/-1

http://www.jegs.com/i/Moroso/710/74105/10002/-1

http://www.jegs.com/i/Unisteer/668/8070030/10002/-1

http://www.jegs.com/i/Unisteer/668/8070040/10002/-1



Thoughts are welcome



Justin 

  	  Quote: 	
		  

	


  

 

  

 

 [quote][b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Nov 19, 2014 8:13 pm Post subject: Solid State Master Relay

At 10:20 2014-11-19, you wrote:

I purchased the following solid state master relay to use in my 

project.  It is designed to be used as an ambulance master relay.



http://www.waytekwire.com/item/44407/300-AMP-SOLID-STATE-BATTERY/



I am wondering what the typical inrush and cranking amperage is to 

the Skytec starters for the Lycoming IO-360.



   It has more to do with wiring and the state of

   your battery than on the engine/starter combination.



I am contemplating wiring the starter from the battery, through the 

relay and to the starter rather than connecting it thru the Battery 

Master Switch.  It would seem that limiting the high amounts of 

current that the starter draws would prolong the already long life of 

these solid state devices.  The maximum rating for this relay is 500A 

for one second.  Over the years, I have experienced numerous master 

relay failures, and I am anxious to try this out.  The link to the 

data sheet is below.



http://www.waytekwire.com/datasheet/44407.pdf



   I notice an IN/OUT nomenclature on the device.

   Are you SURE this is a bi-directional device

   capable of carrying both DISCHARGE and CHARGE

   current?



   What kinds of battery master relays? In 30+ years,

   850 hrs of flying, I've never experienced a master

   relay failure. While operating a fleet of rental

   airplanes on an airport for 6 months, I experienced

   one battery relay failure . . . on a relay that

   was over 20 years old.



   As a spares item compared against the numbers of

   airplanes in service, even the least expensive battery

   relays are a low-volume commodity.



   To have experienced 'numerous' failures gives

   rise to the   question as to what kind of relays

   were involved.



One other option I considered is to wire the starter from the 

battery, to a manual disconnect (such as one in the links below), 

then through the starter relay, thence the starter.  One could attach 

a push-pull cable or rod to the armature of this switch, and easily 

disconnect the battery from the starter while sitting in the cockpit 

in the unlikely event of the starter contacts getting welded 

together, or the starter relay fails closed.  This switch should 

probably be located as close to the battery as possible.



http://www.jegs.com/i/Flaming+River/898/FR1006/10002/-1

http://www.jegs.com/i/Flaming+River/898/FR1003-1/10002/-1

http://www.jegs.com/i/Moroso/710/74105/10002/-1

http://www.jegs.com/i/Unisteer/668/8070030/10002/-1

http://www.jegs.com/i/Unisteer/668/8070040/10002/-1



   There are as many ways to wire an airplane as there

   are creative installers of wires. What you describe

   is, perhaps, unnecessarily complicated; motivated by

   reasons that are not clear to me.



   The solid state switch will be an interesting experiment

   but I'm more interested in understanding your

   displeasure with the legacy parts and architectures.

   Bob . . .

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user9253

Joined: 28 Mar 2008
Posts: 1908
Location: Riley TWP Michigan

Posted: Thu Nov 20, 2014 6:24 am Post subject: Re: Solid State Master Relay

The specs for the solid state relay state,

 	  Quote: 	
		  Internal diode protection for inductive load 

switching 	


I am curious as to how this protection works.  Any inductive induced current will flow in the SAME direction as normal current.

Joe

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_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Nov 20, 2014 7:10 am Post subject: Solid State Master Relay

At 08:24 2014-11-20, you wrote:

 	  Quote: 	
		  



The specs for the solid state relay state,



 > Internal diode protection for inductive load

 > switching



I am curious as to how this protection works.  Any inductive induced 

current will flow in the SAME direction as normal current.


	




http://aeroelectric.com/Pictures/Curves/Relay-Contactor_Performance/Cole-Hersee_without_Diode.gif



They're talking about limiting any potential effects

for having SWITCHED an inductive load to an OFF

state. Here they're speaking to protection of the

contactor as a switch and assuming that unlike

legacy practice for protecting battery master

and starter contactor switches, the installer

would use the device to manage an inductive

load that is not also surrounded with coil

suppression.





   Bob . . .

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jmjones2000(at)mindspring
Guest

Posted: Thu Nov 20, 2014 4:35 pm Post subject: Solid State Master Relay

Apologies for not responding sooner. I am currently deployed.

The relay failures that I have experienced were on Cessna aircraft and both were the factory installed part numbers.  One was a rental aircraft (172) and one was my own aircraft (182).  The 182 relay failed after 500 hours of use. The failures can and do happen, although they are rare.  I have over 3,300 hours of flight time in everything from small aircraft to C-130s.  I have had numerous electrical emergencies on certified aircraft and 3 of them were due to failed relays (not master relays).  The C-130 has a set of “K” relays that switch the AC busses and they are notorious for giving crews issues.  There has been some talk of testing zero switching SSRs to see if some of the failure rates can be reduced.



The cost is higher, but SSRs have rated cycles of 100,000 to 500,000 cycles.  This outlasts legacy mechanical relays by far.  They haven’t been proven for 50+ years, but if we don’t start testing them, they will never be proven.  I don’t expect to put 100,000 cycles on my system, but if it works as advertised, I should never have to replace the relay.  



The relay heat sink has to be able to dissipate the heat that 300A of continuous usage would generate.  I can’t think of a situation where the battery would last long enough for heat to be an issue with this relay.  If it is, the aluminum heat sink should be able to handle it.  Living and operating the aircraft in Alaska will help with this as well.  I can weigh it when I get home, but I do remember thinking that this is much lighter that I initially thought.  I believe it is on par with other 12V master relays.



I am building a Bushcaddy L164 for off airport operations in Alaska.



One reason I would like to use the SSR master relay is to experiment with it and test it.  I am interested to see if it is a viable option to replace the legacy relays.  If so, failed relays may become a thing of the past.

The reason for the installation of the remotely operated battery disconnect switch would be to stop a running battery in the unlikely event that the relay sticks and starter contacts weld together.  Skytec has a webpage about this and has explained it.  The gentleman in the article installed a starter run-on light modification that simply lights an LED when the starter is receiving power.  This will tell you if the starter relay has stuck closed.  The gentleman in the article has installed an Eaton starter relay.  It should be noted that he has a 28V system.



http://www.skytecair.com/Cessna_Solenoids.htm

Justin



 	  Quote: 	
		  On Nov 19, 2014, at 4:01 PM, Jeff Luckey <jluckey(at)pacbell.net (jluckey(at)pacbell.net)> wrote:

Justin,



I'm curious about the decision process that lead to selecting the solid-state relay.  I see some down side:

 

1. Cost - that relay is 4 or 5 times the price of an equivalent mechanical device

2. Power dissipation - That's a pretty hefty heat-sink.  How much power does it need to dissipate

3. I wonder if it is heavier that a mechanical - I didn't see a weight spec.

4. "Proven technology" - How much track record is there for this device?  (I compare this against the standard Master relays with a 50+ year history.)



This is the Master Relay I'm using (I like it because it's lightweight, small, low coil current, & reasonable cost): http://tinyurl.com/nb72gal



Re wiring starter directly:

That's what I'm doing in my RV-7.  Battery to start-assist solenoid to starter.  BobN just made a post in the last couple of days re this topic and I concur w/ his thoughts.  Basically a hung start-assist solenoid is such a rare event that I don't worry about it.



A couple of questions:1. Which airplane are you building?

2. Tell us about your master relay failures.  What aircraft? which relay/contactor?

Please  understand that my intent is not to be critical but rather to  understand how you reached your conclusions. (I might learn something.)

-Jeff



 

     On Wednesday, November 19, 2014 2:16 PM, Justin Jones <jmjones2000(at)mindspring.com (jmjones2000(at)mindspring.com)> wrote:  

   I purchased the following solid state master relay to use in my project.  It is designed to be used as an ambulance master relay.

http://www.waytekwire.com/item/44407/300-AMP-SOLID-STATE-BATTERY/



I am wondering what the typical inrush and cranking amperage is to the Skytec starters for the Lycoming IO-360.  I am contemplating wiring the starter from the battery, through the relay and to the starter rather than connecting it thru the Battery Master Switch.  It would seem that limiting the high amounts of current that the starter draws would prolong the already long life of these solid state devices.  The maximum rating for this relay is 500A for one second.  Over the years, I have experienced numerous master relay failures, and I am anxious to try this out.  The link to the data sheet is below.

http://www.waytekwire.com/datasheet/44407.pdf



One other option I considered is to wire the starter from the battery, to a manual disconnect (such as one in the links below), then through the starter relay, thence the starter.  One could attach a push-pull cable or rod to the armature of this switch, and easily disconnect the battery from the starter while sitting in the cockpit in the unlikely event of the starter contacts getting welded together, or the starter relay fails closed.  This switch should probably be located as close to the battery as possible.



http://www.jegs.com/i/Flaming+River/898/FR1006/10002/-1

http://www.jegs.com/i/Flaming+River/898/FR1003-1/10002/-1

http://www.jegs.com/i/Moroso/710/74105/10002/-1

http://www.jegs.com/i/Unisteer/668/8070030/10002/-1

http://www.jegs.com/i/Unisteer/668/8070040/10002/-1



Thoughts are welcome



Justin 

  	  Quote: 	
		  

	


  

 

  

 

  	  Quote: 	
		  



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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Nov 20, 2014 7:29 pm Post subject: Solid State Master Relay

At 18:33 2014-11-20, you wrote:

 Apologies for not responding sooner. I am currently deployed.



 The relay failures that I have experienced were on Cessna aircraft and both were the factory installed part numbers.  One was a rental aircraft (172) and one was my own aircraft (182).  The 182 relay failed after 500 hours of use. The failures can and do happen, although they are rare.  I have over 3,300 hours of flight time in everything from small aircraft to C-130s.  I have had numerous electrical emergencies on certified aircraft and 3 of them were due to failed relays (not master relays).  The C-130 has a set of “K” relays that switch the AC busses and they are notorious for giving crews issues.  There has been some talk of testing zero switching SSRs to see if some of the failure rates can be reduced.



   Certainly, alternative parts with higher

   degrees of robustness can improve the

   MTBF numbers in any system. But quite

   often, it's less expensive, simpler and

   lighter to design for failure tolerance.



   For example, all of the Z-figures featuring

   and Endurance Bus combined with well maintained

   batteries can make the loss of the battery

   relay no more than a maintenance event.



 The cost is higher, but SSRs have rated cycles of 100,000 to 500,000 cycles.  This outlasts legacy mechanical relays by far.  They haven’t been proven for 50+ years, but if we don’t start testing them, they will never be proven.  I don’t expect to put 100,000 cycles on my system, but if it works as advertised, I should never have to replace the relay.



   If that is the design goal, by all means.

   Suggest you verify that it's not just a battery

   isolation relay but truly capable of

   bidirectional conduction (charge and discharge).

  



 The relay heat sink has to be able to dissipate the heat that 300A of continuous usage would generate.  I can’t think of a situation where the battery would last long enough for heat to be an issue with this relay.  If it is, the aluminum heat sink should be able to handle it.  Living and operating the aircraft in Alaska will help with this as well.  I can weigh it when I get home, but I do remember thinking that this is much lighter that I initially thought.  I believe it is on par with other 12V master relays.



   Good . . .



 

 I am building a Bushcaddy L164 for off airport operations in Alaska.



   Wheeled or floats?



 

 One reason I would like to use the SSR master relay is to experiment with it and test it.  I am interested to see if it is a viable option to replace the legacy relays.  If so, failed relays may become a thing of the past.



   It may well be. Suggest you use it in conjunction

   with an architecture that includes a Plan-B that

   tolerates loss of battery contactor . . . contactors

   can fail to close for reasons other than failure

   of contactor itself.



 The reason for the installation of the remotely operated battery disconnect switch would be to stop a running battery in the unlikely event that the relay sticks and starter contacts weld together.  Skytec has a webpage about this and has explained it.  The gentleman in the article installed a starter run-on light modification that simply lights an LED when the starter is receiving power.  This will tell you if the starter relay has stuck closed.  The gentleman in the article has installed an Eaton starter relay.  It should be noted that he has a 28V system.



  http://www.skytecair.com/Cessna_Solenoids.htm



   Quoting from the article:



 Why pick on Cessna?  Can't this happen to any similarly configured aircraft?



 This absolutely could (and occasionally does) happen to any/all brands of aircraft.  However, we see this occur far more often with Cessna aircraft because of the type (architecture) of relay Cessna specified for use as a starter contactor in production of their aircraft.



   The RBM/Stancore/Cole-Hersee 'beer barrel' contactors have

   often been cited for an elevated failure rate. But one mechanic

   I talked with some years ago admitted that numbers of

   Cessnas  running through his shop were about as great as all

   the other brands combined. He wasn't sure that Cessna was

   experiencing a FAILURE RATE significantly higher than other brands.



   A data point he offered was the fact that poorly

   maintained batteries were the greatest threat to the

   health of any contactor . . . with the 'beer barrel'

   style being the most vulnerable. Tentative and or

   chattering closures when a soggy battery is loaded

   by the starter places all contactors a higher risk

   for sticking.



 Wrong Part - By Design?



 Observing the parts manual for most Cessna aircraft, you will note the same part number used to describe both the starter contactor as well as the master switch relay (master contactor).  



   Really? I'll have to check on that tomorrow. I've

   got some work to do in the EMC lab at Cessna in the morning

   I'll get into a computer and dig through some service manuals.



   I recall writing about the DIFFERENCES

   between intermittent duty and continuous duty

   contactors for service as battery and starter

   control . . . but don't recall the specific

   models. I'll check the drawings.



 

 For instance, one of our customers, Willie Zeiger who flies a beautiful Cessna 185 out of Anchorage Alaska, notes in a letter to the factory, "Both relays are rated for continuous duty and are good for both the master relay and starter relay."



 However, the duty of each of these functions (starter contactor vs. master relay) are quite different and, as such, should (and in other makes of aircraft DO) require different types of relays.  



   I cannot dispute anyone's observations for having

   found a battery contactor installed in place of

   a starter contactor but I'm skeptical that the

   parts catalog calls it out. The difference between

   them is well understood. Further, they're the same price

   to the OEM. Any notion that such a condition exists

   by design is suspect.  I'll check.



 

   Bob . . .    [quote][b]

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