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Dual Battery Setup

 
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robert(at)theschmids.org
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PostPosted: Mon Oct 10, 2022 3:59 pm    Post subject: Dual Battery Setup Reply with quote
I am new to this list, but was told to come here for advice on my electrical design for a fuel injected, electronic ignition single engine plane. I have looked at AeroElectric design recommendations but wanted to hear feedback on the following changes ...
  • Have 2 identical, redundant, in parallel batteries instead of one full and one backup ... I need to weight anyhow
  • Have 2 identical, redundant, in parallel high pressure fuel pumps
  • I run an electronic circuit breaker system called VP-X for all components except ignition coils and injectors per SDS EFI manufacturer recommendation
  • With the VPX, I can switch all components individually in my EFIS, measure amp usage and I have therefore very few switches on the panel
My engine start procedure is designed as follows ...
  • MAIN on
  • FUEL PUMP(S) on
  • Fuel pressure CHECK
  • Starting engine
  • Oil pressure CHECK
My runup procedure is designed as follows ...

  • Battery CHECK for 1, 2, both by using DPDT battery switch ... leave on both for takeoff, 1 or 2 in cruise
  • Fuel pumps CHECK for 1, 2, both by using DPDT fuel pump switch ... leave on both for takeoff, 1 or 2 in cruise
  • Coils CHECK for 1, 2, both by pulling push button circuit breakers ... leave on both for entire flight

  Duckie Wiring.pdf



I have attached my electrical drawing, a draft so be gentle 😉. Please take a look but focus on my battery setup as it's different from Bob's design.

Thanks Robert
[img]https://cdn.gifo.wisestamp.com/im/sh/aHR0cHM6Ly9zMy5hbWF6b25hd3MuY29tL3Vjd2ViYXBwLndpc2VzdGFtcC5jb20vM2E5NDljZjQtMDcwMy00YjRmLWFkNGUtNzBiZTI3OWQ2OGM2LzEzNDY2MjU5XzEwMTU0MTU5NTYzOTY2NTQ0XzQyNzgwNTk1MzA0NjE0OTU2OTNfbi5mb3JtYXRfcG5nLnJlc2l6ZV8yMDB4LnBuZw==/rounded.png[/img]Robert Schmid
robert(at)theschmids.org (robert(at)theschmids.org)
theschmids.org
"Age is something that doesn't matter, unless you are a cheese." - Luis Bunuel.



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nuckolls.bob(at)aeroelect
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PostPosted: Tue Oct 11, 2022 9:05 am    Post subject: Dual Battery Setup Reply with quote
At 06:58 PM 10/10/2022, you wrote:
Quote:
I am new to this list, but was told to come here for advice on my electrical design for a fuel injected, electronic ignition single engine plane. I have looked at AeroElectric design recommendations but wanted to hear feedback on the following changes ...

Your battery and fuel pump controls argue with
'redundant'. Both switch arrays offer single
points of failure for both systems.

'Redundant' generally implies TOTAL separation.




Bob . . .

Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"

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johnbright



Joined: 14 Dec 2011
Posts: 165
Location: Newport News, VA
PostPosted: Sat Oct 22, 2022 4:28 pm    Post subject: Re: Dual Battery Setup Reply with quote
Re schematic Batteries, Alternator, Starter & Power Distribution rev v1.1

    I imagine panel switches are more convenient than getting into the EFIS menu to control feeds from the VP-X.

    You don't want to run starter current thru an ammeter shunt.

    VP-X is an SPOF for both pumps... in addition to your chosen switch wiring as mentioned in the previous post.

    Your battery contactor and fuel pump switches are not DPDT but 2-10 style. The terminal numbers are correct so I guess you simply don't have the correct symbol in your CAD library. You have four switches... two for battery contactors and two for fuel pumps... to me it would be less confusing to have four on-off switches and it would also solve your SPOF problem... two on-off for battery contactors and two on-off for fuel pumps.

    There's a culture war between the single-alternator-dual-battery and dual-alternator-single-battery camps.
      Have you seen Z101... the latest from Bob Nuckolls... dual-alternator-single-battery... it's not in the Aeroelectric Connection book at this time. It's my choice... I'm planning SDS EFI+I also... my schematics and supporting documents are linked in my signature FWIW. All engine-related items on the engine bus.
      With two alternators your one-alternator-offline endurance is limited to fuel rather than battery capacity.
      There's Z102 (pending - not released) single-alternator-dual-battery in case of an automotive engine that will not accomodate two alternators. Like Z101, Z102 has an engine bus. You'll want to do initial and periodic battery capacity checks.


    There's also a culture war between breakers and fuses. Your are in the breaker camp... the Aeroelectric guys are in the fuse camp except for the 5A field breaker on wound-field alternators.

    If you replace the fuel injector breakers with fuses you will save panel space.

    My calculations indicate four cylinder SDS EFI+I will draw 9A at cruise... this can be reduced to 7.9 by turning off one coilpack in what I call Endurance Mode in case you are running off battery capacity. Ref Load Analysis in my folder 3.

    Beware unintended consequences of straying from published Z templates.

    Subscribe to the Aeroelectric List and you'll learn an lot... slowly.


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_________________
John Bright, RV-6A, at FWF, O-360
Z-101 single batt dual alt SDS EM-5-F.
john_s_bright@yahoo.com, Newport News, Va
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