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Second battery in a TC aircraft

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nuckollsr(at)cox.net
Guest

Posted: Sat Jun 03, 2006 9:05 am Post subject: Second battery in a TC aircraft

At 10:36 AM 6/1/2006 -1000, you wrote:

 >Bob,

 >

 >Please note the two attached drawings (and also please excuse my style).

 >

 >I have a Republic Seabee, and I want a dual battery system with the 

second battery being always hot, feeding the Hot Battery Bus through a 

circuit breaker.  The purpose of this battery is to provide power for 

things like bilge pumps, anchor light, clocks, and occasionally a GPS 

(which has an anchor dragging alarm) without creating the possibility of 

discharging the main starting battery.

 >

 >I have a single alternator (B&S) that I would like to use to charge both 

batteries through a battery charging isolator.

 >

 >I might also add a battery parallel switch to allow the hot battery to 

serve as a backup battery, but since it is the one that is most likely to 

run down, I may eliminate that concept, at least until I gain some experience.

 >

 >My question for you is:  Do you see any regulatory, operational, or 

electrical problems with this arrangement?  I think it should work well, 

though I don't know if the FAA has any opinions on battery isolator diodes.

 >

 >Both batteries are Odyssey PC 1200s of about 40 AH rating.

    Don't make this any more complicated than it needs to be. You'll have

    to get a 337 approval for the installation of the second battery. FAA

    will have no heartburn about the second battery but you'll want your

    337 to touch on structural, and crash safety issues.



    I don't recommend diodes. Just add a second battery to the system

    with it's own battery contactor. You can use either or both batteries

    for cranking. The battery bus for the second battery can run gizmos

    cited in your note as long as each gizmo is under 5A. This is the

    largest always-hot wire the FAA blesses under their rule-of-thumb

    for max size of protected wire for crash safety. If you can get

    a fuse-block blessed . . . so much the better. Fuses are MUCH faster

    and therefore safer than breakers.



    Battery bus for second battery needs to be mounted right at the

    battery . . . so fuse-blocks work out well.



    Here's a Shop Note on dual battery installation in all metal

    airplanes.



http://aeroelectric.com/articles/Battery_Grounds/Battery_Grounds.html



    Second battery is wired per Z-30 of



http://aeroelectric.com/articles/Rev11/AppZ_R11G.pdf



    I've helped a half dozen or so folks install this same system in

    things like C-206 on floats. We put the second battery right on

    the aircraft CG inside one of the floats. Kept the battery from

    using up fuselage volume and simplified crash safety issues.



    I wish I could point you to a completed 337 for guidance

    but all the installations I worked were for missionaries

    and other bush operations in S. America. One pretty much

    accomplishes what's necessary to their airplane without

    government impediments.



             Bob . . .



             -----------------------------------------

             ( Experience and common sense cannot be )

             ( replaced with policy and procedures.  )

             (                  R. L. Nuckolls III   )

             -----------------------------------------

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markacarey(at)msn.com
Guest

Posted: Fri Jun 09, 2006 12:14 pm Post subject: Second battery in a TC aircraft

Bob:



I installed a single No. 2 positive wire from the firewall to the tail in my 

RV10.  I have dual alternators (40 and 20 A B&C) and dual batteries.  The 

alternators both feed to the firewall connection with 40 amp in-line fuses.  

I am using the No. 2 to charge both batteries and have installed a diode to 

allow the standby battery to charge while not allowing it to discharge 

unless the standby contactor is closed.  You said you don't recommend diodes 

but it appears you have one shown in Z-14.  Your diode appears to allow the 

standby alt. to charge the main battery whereas the diode I have in mind 

charges the standby battery.  Any thoughts??

 	  Quote: 	
		  From: "Robert L. Nuckolls, III" <nuckollsr(at)cox.net>

Reply-To: aeroelectric-list(at)matronics.com

To: aeroelectric-list(at)matronics.com

Subject: Second battery in a TC aircraft

Date: Sat, 03 Jun 2006 12:02:03 -0500




<nuckollsr(at)cox.net>



At 10:36 AM 6/1/2006 -1000, you wrote:

  >Bob,

  >

  >Please note the two attached drawings (and also please excuse my style).

  >

  >I have a Republic Seabee, and I want a dual battery system with the

second battery being always hot, feeding the Hot Battery Bus through a

circuit breaker.  The purpose of this battery is to provide power for

things like bilge pumps, anchor light, clocks, and occasionally a GPS

(which has an anchor dragging alarm) without creating the possibility of

discharging the main starting battery.

  >

  >I have a single alternator (B&S) that I would like to use to charge both

batteries through a battery charging isolator.

  >

  >I might also add a battery parallel switch to allow the hot battery to

serve as a backup battery, but since it is the one that is most likely to

run down, I may eliminate that concept, at least until I gain some 

experience.

  >

  >My question for you is:  Do you see any regulatory, operational, or

electrical problems with this arrangement?  I think it should work well,

though I don't know if the FAA has any opinions on battery isolator diodes.

  >

  >Both batteries are Odyssey PC 1200s of about 40 AH rating.

     Don't make this any more complicated than it needs to be. You'll have

     to get a 337 approval for the installation of the second battery. FAA

     will have no heartburn about the second battery but you'll want your

     337 to touch on structural, and crash safety issues.



     I don't recommend diodes. Just add a second battery to the system

     with it's own battery contactor. You can use either or both batteries

     for cranking. The battery bus for the second battery can run gizmos

     cited in your note as long as each gizmo is under 5A. This is the

     largest always-hot wire the FAA blesses under their rule-of-thumb

     for max size of protected wire for crash safety. If you can get

     a fuse-block blessed . . . so much the better. Fuses are MUCH faster

     and therefore safer than breakers.



     Battery bus for second battery needs to be mounted right at the

     battery . . . so fuse-blocks work out well.



     Here's a Shop Note on dual battery installation in all metal

     airplanes.



http://aeroelectric.com/articles/Battery_Grounds/Battery_Grounds.html



     Second battery is wired per Z-30 of



http://aeroelectric.com/articles/Rev11/AppZ_R11G.pdf



     I've helped a half dozen or so folks install this same system in

     things like C-206 on floats. We put the second battery right on

     the aircraft CG inside one of the floats. Kept the battery from

     using up fuselage volume and simplified crash safety issues.



     I wish I could point you to a completed 337 for guidance

     but all the installations I worked were for missionaries

     and other bush operations in S. America. One pretty much

     accomplishes what's necessary to their airplane without

     government impediments.



              Bob . . .



              -----------------------------------------

              ( Experience and common sense cannot be )

              ( replaced with policy and procedures.  )

              (                  R. L. Nuckolls III   )

              -----------------------------------------

- The Matronics AeroElectric-List Email Forum -

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:

http://www.matronics.com/Navigator?AeroElectric-List

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