Wiring a "dead drain" battery electrical system

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cluttonfred

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Eliminating the engine-driven aspect of an electrical system simplifies it greatly, but there are still a few things to consider. I'd love to hear from folks with more knowledge and experience on these notions and questions:


  1. What about using a mechanical battery disconnect switch as the "master" either within reach if the battery is located within reach? If key-operated it could be used to secure the system when not in use.
  2. Or, if the battery is farther away, how about one with operated by a push/pull rod or cable?
  3. Should there be a fuse or circuit-breaker right at the battery in case of a catastrophic short-circuit?
  4. Any strong opinions on integrated switches-circuit breakers vs. separate switches and breakers vs. separate switches and fuses?
  5. There are likely to be a few other items powered by the battery (12v gauges, maybe a radio or an anti-collision light), any special do and don't considerations when wiring those?
  6. In some designs including the VP-1 and VP-2 the fuel is very close at hand. Any special considerations for reducing fire danger with this kind of setup?

Cheers,

Matthew
 

BJC

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Eliminating the engine-driven aspect of an electrical system simplifies it greatly, but there are still a few things to consider. I'd love to hear from folks with more knowledge and experience on these notions and questions:

[*]What about using a mechanical battery disconnect switch as the "master" either within reach if the battery is located within reach? If key-operated it could be used to secure the system when not in use.

Cheers,

Matthew
My airplane has a battery behind the seat, with a mechanical disconnect switch mounted about 8 inches from the battery. It powers a light weight starter and a hand held radio. Works just fine. Remember to bring out a lead for the battery maintainer.


BJC
 

cluttonfred

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Thanks, BJC. Can you reach the disconnect in flight? And do you have any circuit breakers, fuses or switches in the system? Sounds like you have magneto ignition, where I was thinking of a battery-powered distributor or EI.
 

Turd Ferguson

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A total loss ignition is one thing......total loss electrical system I can't imagine. I'd want neither one on a flying machine. Oops, unrelated to threat, disregard.

Seriously, I can't imagine a reason to disconnect the battery in flight. That would kill the engine, compounding any previous abnormal/emergency.
 

cluttonfred

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The logic was that, if running a total loss/dead drain ignition, you may as well make the battery a little bigger and run a couple of gauges, an LED beacon and the radio. Presumably the only reason to shut off the battery in flight would be in the case of a fire or an impending crash such as an engine out away from a field, when you would shut of the fuel and power to reduce fire risk.
 

BJC

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Thanks, BJC. Can you reach the disconnect in flight? And do you have any circuit breakers, fuses or switches in the system? Sounds like you have magneto ignition, where I was thinking of a battery-powered distributor or EI.
Switch can be reached in flight with right hand behind the right side of the seat back.

No breakers. One PB starter switch.

Yes, two magnetos.

Photo looking aft in fuselage with the seat back removed:

Pitts Battery Switch.jpg


BJC

PS Anyone know how to stop the Uploader from rotating iPhone photos?
 

cluttonfred

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TFF

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I did not say I did not like them, but if Im going to steal it will have Lear or Pitts stenciled on the tail or something worth going to jail for. Not going to jail for a VP.
 

cluttonfred

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The removable key would be a hazard in my airplane - loose items in the control system is a big concern.
As TF pointed out, if it's powering the ignition and it falls out, you'll know it, as I believe that it is only removable in the off position. ;-)
 

Daleandee

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I am wounded, sir! Not all VPs are ugly, though they are generally, ummm, "rustic." ;-)
It's a tough crowd around here sometimes ...

http://www.homebuiltairplanes.com/forums/general-experimental-aviation-questions/24381-kit-planes-april-issue-thatcher-cx5.html#post312035

BTW ... if looking for a dependable cutoff switch I'd consider a blade type:

https://www.google.com/search?q=blade+type+battery+disconnect&rlz=1C1CHFX_enUS494US494&source=lnms&tbm=isch&sa=X&ved=0ahUKEwif88D448_MAhUBxSYKHToeA_oQ_AUIBygB&biw=1366&bih=643

Wire it to the negative side of the battery.

Dale Williams
N319WF @ 6J2
Myunn - "daughter of Cleanex"
120 HP - 3.0 Corvair
Tail Wheel - Center Stick
Signature Finish 2200 Paint Job
119.6 hours / Status - Flying
 

Toobuilder

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The master switch on my Mooney and Tri Pacer were simply toggle switches. In the case of the Mooney, it was mounted ahead of the firewall and actuated by a push/pull cable
 

goldrush

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I you use a relay instead of a mechanical system, ensure that it is rated for continuous use and rated for maximum current. The operating coil in any other type can overheat.
You may find this list of measured starter cranking currents etc from the aerolithium site, useful..

PISTON Battery needed
A good way to know what cranking amps your starter needs to start engine; use a clamp-on ammeter around a battery cable.

HKS 700E - 60Hpwr - 125amps ....... 220A

Rotax 582 - 65 Hp - 137A .................220A

Rotax 503 - 52 Hp - 153A ...................220A

Hirth 2704 - 55 Hp - 167A ..................220A

Cont. O-190 - 75Hp - 175A ..............330A

Lyc. I O - 360-200HP - 350A ............440A
Lyc. I O 540, Cont. 470 / 550 ..........440A
Cont. 550 - 24V .................................330A
V W engine .........................................330A

TURBINE
Solar T-62t - 32 ..................................550A
std T-62t ..............................................440A

I have recently used a "$10 cheapie" "charge changeover" such as this from Malaysia on my rotax 503 SSDR (similar to Part 103) machine.

12V 200A Relay 4 Pin Car Auto Heavy Duty Install Style Split Chargeover | eBay
 
J

JanHalsey

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Hi everyone...i am new here. I worked on some projects and as per my experience if running a total loss/dead drain ignition, you may as well make the battery a little bigger and run a couple of gauges, an LED beacon and the radio. Presumably the only reason to shut off the battery in flight would be in the case of a fire or an impending crash such as an engine out away from a field, when you would shut of the fuel and power to reduce fire risk.
 
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