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Back-Up Battery ground

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trigo(at)mail.telepac.pt
Guest

Posted: Sun Dec 24, 2006 1:14 pm Post subject: Back-Up Battery ground

Since I will have to put some wheight in the tail of my RV-9A because of W&B 

issues, I am planning to install a small battery (probably around 4.5Ah, 

depending on its own wheight) to act as a back-up battery for some avionics 

(EFIS and Auto-pilot).

For the (+) terminal of that future battery, I already passed a AWG#14 

tefzel wire all the way from the tail to the back of instrument pannel, but 

for the (-) wire, I am thinking that I could attach it to a ground lug that 

I already have in the tail, which is directly connected to the "Main" 

battery (-) terminal, and where are also connected the ground wires from the 

tail light, the tail strobe beacon and the elevator trim motor.



Can I connect that battery's (-) terminal to the tail ground lug ?

Is there a possibility for ground loop ?



Carlos

tompkinsl(at)integra.net
Guest

Posted: Tue Dec 26, 2006 11:05 am Post subject: Back-Up Battery ground

Why not just carry a small amount of ballast in the  baggage compartment that you can trade for cargo when the need arises?  I  think it's the simplest solution and gives you the oppportunity to maximize  cargo capacity.

  

 Larry

   [quote][b]

bicyclop(at)pacbell.net
Guest

Posted: Tue Dec 26, 2006 11:47 am Post subject: Back-Up Battery ground

Toolkit for instance. Survival supplies good too.  

   

Pax,  

   

Ed   

   

--

nuckollsr(at)cox.net
Guest

Posted: Tue Dec 26, 2006 12:01 pm Post subject: Back-Up Battery ground

At 11:04 AM 12/26/2006 -0800, you wrote:



 	  Quote: 	
		  Why not just carry a small amount of ballast in the baggage compartment 

that you can trade for cargo when the need arises?  I think it's the 

simplest solution and gives you the oppportunity to maximize cargo capacity.



Larry


	


   An astute question sir.  A Bonanza I used to rent had 6 plastic jugs

   in the baggage compartment with a tiedown net. If one anticipated

   lightly loaded flights, the jugs are filled with water to keep

   the balance in range. If one were going to use the baggage compartment

   both ways, then the net was used to wrap up jugs and hang them on

   the hangar wall before departure. If you needed the weight only

   one way, the jugs could be filled/emptied as needed for up to 50

   pounds of aft ballast adjustment.



   If I wanted to have adjustable balance while minimizing weight,

   how about a plastic tank as far aft as possible with external

   filler/drain access. Fill or empty as needed. Obviously, changes

   could be accomplished only at temperatures above 32 degrees!



   Sailplanes use water as a dynamic ballasting medium, don't

   see why Haulplanes couldn't do it too.



   Bob . . .





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

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

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

trigo(at)mail.telepac.pt
Guest

Posted: Tue Dec 26, 2006 12:25 pm Post subject: Back-Up Battery ground

Bob, Larry et all



Please forget the reason why I may want to put the Avionics Back-Up battery 

in the tail, and please answer the electric questions:

  - Can I connect the (-) terminal of that battery to the tail's ground lug,

which is isolated from the fuselage and is directly connected to the (-)

terminal of the "Main" battery ?

  - Can I continue to use that same ground lug to connect the other grounds

( from the tail light, the strobe beacon, and the elevator trim motor)

there?

   - Isn't there any possibility of "ground loop"?



Carlos

---

BobsV35B(at)aol.com
Guest

Posted: Tue Dec 26, 2006 12:27 pm Post subject: Back-Up Battery ground

In a message dated 12/26/2006 2:03:20 P.M. Central Standard Time,  nuckollsr(at)cox.net writes:

  	  Quote: 	
		  An    astute question sir.  A Bonanza I used to rent had 6 plastic    jugs

   in the baggage compartment with a tie down net. If one    anticipated

   lightly loaded flights, the jugs are filled with    water to keep

   the balance in range. If one were going to use    the baggage compartment

   both ways, then the net was used to    wrap up jugs and hang them on

   the hangar wall before    departure. If you needed the weight only

   one way, the jugs    could be filled/emptied as needed for up to 50

   pounds of aft    ballast adjustment.



   If I wanted to have adjustable balance    while minimizing weight,

   how about a plastic tank as far aft    as possible with external

   filler/drain access. Fill or empty    as needed. Obviously, changes

   could be accomplished only at    temperatures above 32 degrees!



   Sailplanes use water as a    dynamic ballasting medium, don't

   see why Haulplanes couldn't    do it too.



   Bob . . .

	


 

Good Afternoon Bob,

  

 Just for a statistical data point, in the days of the DC-3, all airlines  used canvas bags with lead shot as ballast. They had canvas handles and each  weighed fifty pounds. 

  

 A baggage a cart full of ballast bags was maintained at each station. The  bags would be thrown in the aft baggage compartment of the DC-3 so as to  maintain a reasonable CG. If any one station got a little low on bags or a  little heavy on bags, a message would be sent and bags would be moved from the  'Heavy' stations to the 'Light' stations.

  

 If I Recall Correctly, for an empty airplane, we needed around five hundred  pounds of ballast in the aft compartment. I could be off by a couple of hundred  pounds on that though.

  

 Worked well for a stable airline.

  

 The idea of hauling ballast has a long history with sailing ships. They  would unload paying cargo in the New World and load up on rocks and stones to  get reasonable stability for the trip home. A major effort was made to load up  stones that may have some value when the ship reached a port that had better  paying cargo available.

  

 Nothing much new under the sun is there?

  

 Do Not Archive

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503

  [quote][b]

nuckollsr(at)cox.net
Guest

Posted: Tue Dec 26, 2006 6:11 pm Post subject: Back-Up Battery ground

At 08:24 PM 12/26/2006 +0000, you wrote:



 	  Quote: 	
		  

<trigo(at)mail.telepac.pt>



Bob, Larry et all



Please forget the reason why I may want to put the Avionics Back-Up 

battery in the tail, and please answer the electric questions:

  - Can I connect the (-) terminal of that battery to the tail's ground lug,

which is isolated from the fuselage and is directly connected to the (-)

terminal of the "Main" battery ?


	


   Can't imagine what you're describing here. Ground the

   battery to local structure.



 	  Quote: 	
		    - Can I continue to use that same ground lug to connect the other grounds

( from the tail light, the strobe beacon, and the elevator trim motor)

there?


	


    Ground these devices to local structure. You don't

    need a "tail ground" in a metal airplane for items

    located in the tail.



 	  Quote: 	
		     - Isn't there any possibility of "ground loop"?


	


    No.



    Do you plan a "mini battery contactor" for this "mini-battery"?



    Even thought it's a relatively small battery compared to

    the ship's battery, it is capable of significant fault currents

    and should be treated like any other battery with respect to

    positive disconnection via local contactor.



    It would be helpful if you could publish sketches of your

    proposed wiring.



    Bob . . .

nuckollsr(at)cox.net
Guest

Posted: Tue Dec 26, 2006 6:12 pm Post subject: Back-Up Battery ground

 	  Quote: 	
		  Good Afternoon Bob,



Just for a statistical data point, in the days of the DC-3, all airlines 

used canvas bags with lead shot as ballast. They had canvas handles and 

each weighed fifty pounds.



A baggage a cart full of ballast bags was maintained at each station. The 

bags would be thrown in the aft baggage compartment of the DC-3 so as to 

maintain a reasonable CG. If any one station got a little low on bags or a 

little heavy on bags, a message would be sent and bags would be moved from 

the 'Heavy' stations to the 'Light' stations.



If I Recall Correctly, for an empty airplane, we needed around five 

hundred pounds of ballast in the aft compartment. I could be off by a 

couple of hundred pounds on that though.



Worked well for a stable airline.



The idea of hauling ballast has a long history with sailing ships. They 

would unload paying cargo in the New World and load up on rocks and stones 

to get reasonable stability for the trip home. A major effort was made to 

load up stones that may have some value when the ship reached a port that 

had better paying cargo available.


	


   Puts a whole new twist on the term "dead heading" . . . nothing

   deader than a rock!



   Bob . . .

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

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

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

Speedy11(at)aol.com
Guest

Posted: Wed Dec 27, 2006 6:44 pm Post subject: Back-Up Battery ground

Carlos,

 Good luck getting a helpful answer on this list.  You can normally get little more than criticism and ridicule.

 It sounds as though you have a ground wire running from your main battery to the aft portion of the fuselage and you want to know if connecting your back-up battery in the aft fuselage to that same ground wire will cause any problems.  Is that correct?

 Stan Sutterfield

 Do not archive

  

  	  Quote: 	
		  Please forget the reason why I may want to put the Avionics Back-Up battery 

in the tail, and please answer the electric questions:

  - Can I connect the (-) terminal of that battery to the tail's ground lug,

which is isolated from the fuselage and is directly connected to the (-)

terminal of the "Main" battery ?

  - Can I continue to use that same ground lug to connect the other grounds

( from the tail light, the strobe beacon, and the elevator trim motor)

there?

   - Isn't there any possibility of "ground loop"?



Carlos 	


 

  [quote][b]

trigo(at)mail.telepac.pt
Guest

Posted: Thu Dec 28, 2006 3:05 am Post subject: Back-Up Battery ground

Yeah

  

 Some times on this list, if you ask apples you get an answer  in oranges 

 I also hate that particular facet of this group, and  I'm waiting for the time when someone asks if he can connect a red  ground wire to some device, and he will get the answer that he should not  use red on that wire! .

 Well, but most of the times, this forum is useful, so I keep  trying.

  

 Stan

 That's exactly what I was asking.

  

 Carlos

 [quote]   ---

mlas(at)cox.net
Guest

Posted: Thu Dec 28, 2006 7:30 am Post subject: Back-Up Battery ground

            Ask a better question (more complete), get a better answer.  Or you could just bring it over and will fix it.  

   

Just helping the sarcasm along!  

   

Mike Larkin  

   

--

pats4p(at)sbcglobal.net
Guest

Posted: Fri Dec 29, 2006 3:44 pm Post subject: Back-Up Battery ground

Touche' [quote][b]

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