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Battery Disconnect Switch...

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steve(at)tomasara.com
Guest

Posted: Mon Dec 09, 2013 8:06 am Post subject: Battery Disconnect Switch...

Greetings,



I'm working on the wiring for a Solitare and it uses a small engine (KFM 

Maxi 107) with only a 300W starter.  I'm shopping for an appropriate 

disconnect switch  (in lieu of a master relay) that is capable of 

disconnecting the starter current should the starter relay get stuck.



I don't know much about the starter motor other than the 300W listed in 

the engine manual (PM?  series wound?) but given the 300W it seems like 

100A disconnect capable switch should be more than enough when taking 

into account battery sag and motor inefficiency. However, if anyone has 

a defensible way to come up with a better number, I'd love to hear it.  

I'm looking for the physically smallest switch that is up to the task.



Does anyone have an suggestions an appropriate switch?  The usual 

race-car style battery disconnects are way over-kill and physically 

quite large as a result.



All thoughts appreciated,



Steve Stearns

Boulder/Longmont, Colorado

Restoring (since 1/07) and flying again (8/11!): N45FC O235 Longeze 

Cothern/Friling CF1 (~1000 Hrs)

Flying (since 9/86): N43732 A65 Taylorcraft BC12D

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steve(at)tomasara.com
Guest

Posted: Mon Dec 09, 2013 8:28 am Post subject: Battery Disconnect Switch...

Related question:  How much do you have to de-rate the combined current 

handling if you wire a DPST with the poles in parallel?  I'm assuming if 

you have a 30A DPST toggle switch (which I've found. Big, but not as big 

as a battery disconnect switch) and you wire the poles in parallel, the 

appropriate rating is something less than 60A.  Anyone know?



Thanks,



Steve.



On 12/9/2013 9:05 AM, Steve Stearns wrote:

 	  Quote: 	
		   Greetings,



 I'm working on the wiring for a Solitare and it uses a small engine 

 (KFM Maxi 107) with only a 300W starter.  I'm shopping for an 

 appropriate disconnect switch  (in lieu of a master relay) that is 

 capable of disconnecting the starter current should the starter relay 

 get stuck.



 I don't know much about the starter motor other than the 300W listed 

 in the engine manual (PM?  series wound?) but given the 300W it seems 

 like 100A disconnect capable switch should be more than enough when 

 taking into account battery sag and motor inefficiency. However, if 

 anyone has a defensible way to come up with a better number, I'd love 

 to hear it.  I'm looking for the physically smallest switch that is up 

 to the task.



 Does anyone have an suggestions an appropriate switch?  The usual 

 race-car style battery disconnects are way over-kill and physically 

 quite large as a result.



 All thoughts appreciated,



 Steve Stearns

 Boulder/Longmont, Colorado

 Restoring (since 1/07) and flying again (8/11!): N45FC O235 Longeze 

 Cothern/Friling CF1 (~1000 Hrs)

 Flying (since 9/86): N43732 A65 Taylorcraft BC12D

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon Dec 09, 2013 9:05 am Post subject: Battery Disconnect Switch...

At 10:05 AM 12/9/2013, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Steve Stearns <steve(at)tomasara.com>



 Greetings,



 I'm working on the wiring for a Solitare and it uses a small engine (KFM Maxi 107) with only a 300W starter.  I'm shopping for an appropriate disconnect switch  (in lieu of a master relay) that is capable of disconnecting the starter current should the starter relay get stuck.



 I don't know much about the starter motor other than the 300W listed in the engine manual (PM?  series wound?) but given the 300W it seems like 100A disconnect capable switch should be more than enough when taking into account battery sag and motor inefficiency. However, if anyone has a defensible way to come up with a better number, I'd love to hear it.  

 I'm looking for the physically smallest switch that is up to the task.



 Does anyone have an suggestions an appropriate switch?  The usual race-car style battery disconnects are way over-kill and physically quite large as a result.



 All thoughts appreciated, 	


   Hi Steve,



   It's been a long time since we've chatted.



   Consider this item from Summit Racing



 [img]cid:7.1.0.9.0.20131209105836.012a10e8(at)aeroelectric.com.0[/img] 



   It's their SUM-G1432 



   It's 'rated' with some pretty sedate currents

   as a switch . . . but your switching requirements

   are benign also. I'd bet this switch will CARRY

   the starter currents just fine.



   In any case, the price is right (about $20) and

   the size is attractive too. There's also a Moroso

   74101 that is about the same size and RATED for

   much greater currents. A tad more expensive too

   at $45 but almost certain to be suited to

   the task. See:



  http://tinyurl.com/kj5jwba



 



 

 

   Bob . . .

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