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Rear Mounted Batteries - more questions

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lamphere(at)earthlink.net
Guest

Posted: Wed Mar 28, 2007 4:20 am Post subject: Rear Mounted Batteries - more questions

Bob,



Now you are confusing me..



Yes, I did look at the link you provided. 



Using the generic aircraft - single battery schematic for schematic on metal tube frame.

Battery (Odyssey 680) and contactor will be located under baggage compartment floor behind seat backs.

 

I thought we were supposed to run a ground wire from the battery to the brass ground bus plate (with all the quick connect tabs on it) which was to be mounted on the firewall. Isn't using the airframe for ground now generating two paths for ground - hence possible problems?



I'm about ready to wire in my rear mounted battery (before covering). I will use flexible wire for the battery terminal connections (and to the local ground if that's what I am supposed to do). No problem attaching ground leads to the frame if a good idea. It would eliminate an extra wire to top and bottom strobes and tail position light... but I was already resolved to run + and gnd to each (using a small local-next to battery version of the brass ground bus with quick disconnects like in the front)



I'd appreciate your input.



Thanks,

Dave



---

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nuckollsr(at)cox.net
Guest

Posted: Wed Mar 28, 2007 5:28 am Post subject: Rear Mounted Batteries - more questions

At 08:19 AM 3/28/2007 -0500, you wrote:



 	  Quote: 	
		  

<lamphere(at)earthlink.net>



Bob,



Now you are confusing me..



Yes, I did look at the link you provided.



Using the generic aircraft - single battery schematic for schematic on 

metal tube frame.

Battery (Odyssey 680) and contactor will be located under baggage 

compartment floor behind seat backs.



I thought we were supposed to run a ground wire from the battery to the 

brass ground bus plate (with all the quick connect tabs on it) which was 

to be mounted on the firewall. Isn't using the airframe for ground now 

generating two paths for ground - hence possible problems?


	


     Local grounds in all metal airplanes can practically

     depart from "ideal" for the following:



     Batteries, strobe supplies, landing/taxi lights,

     pitot heaters, position lights, hydraulic pumps

     for landing gear (because they're intermittent)

     but not for air-conditioning compressors (because

     they're continuous).

 	  Quote: 	
		  I'm about ready to wire in my rear mounted battery (before covering). I 

will use flexible wire for the battery terminal connections (and to the 

local ground if that's what I am supposed to do). No problem attaching 

ground leads to the frame if a good idea. It would eliminate an extra wire 

to top and bottom strobes and tail position light... but I was already 

resolved to run + and gnd to each (using a small local-next to battery 

version of the brass ground bus with quick disconnects like in the front)



I'd appreciate your input.


	


     It's never 'bad' to run all electro-whizzies to a

     single point ground but if one wishes to take advantage

     of the ground-friendly, all-metal airplane with the

     cited compromises, there's no risk of having an unhappy

     noise moment.



     It's most important to pay attention to grounding

     potential victims such as avionics and instrumentation.

     These should return to the firewall ground point per

     Z-15.



     I'll add some notes to Z-15 next revision to clarify

     this point.



     Bob . . .

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longg(at)pjm.com
Guest

Posted: Wed Mar 28, 2007 5:52 am Post subject: Rear Mounted Batteries - more questions

Wednesday battery installation tip. 



I am relatively new to this wiring stuff, but I have had the experience

of replacing all of the battery, starter etc cables in a Piper 67'

PA140. Believe it or not, they had a pretty good setup for a rear

mounted battery. They had a really silly set of jumpers wires

connected/welded to the battery box and routed through grommets on the

box to the battery (eliminated by Aircraft Spruce upgrade kit), but the

layout will provide anyone hoping to install rear mounted batteries with

a very clear picture of how things are done. Visit your FBO and ask

someone to let you look under the rear seat (there's always a 140

around). Take a picture of the layout. One note about their setup is

that they installed the starter contactor on firewall and run a #6? from

the rear up the left side, through the firewall to the contactor and

then to the starter which is up front on the Lycoming. I was very proud

of my first wiring job and gladly threw that old stuff in the trash. The

engine turned over 3x faster with the new cables etc. I am installing

dual batteries rear of the rear bulkhead in my new Legacy and will use

the pictures I took to help with the layout.



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john_rv10(at)yahoo.com
Guest

Posted: Sat Mar 31, 2007 3:19 pm Post subject: Rear Mounted Batteries - more questions

Hello 'Lectric Bob,



Thank you for all the fantastic effort you put into this group. It is

extremely helpful to those of us with zero earlier experience in this area.



I have read the Connection a couple of times and I have been pondering the

whole issue of batteries and locations and fat wires etc. 



Attached is a schematic of a Z-14, architecture for rear batteries. This is

not your current Z-14, and I don't know now where I got this from, but it

very specifically states that the Aft Ground Buss is NOT Grounded to the

airframe.



My wife and I are building an RV-10. We are planning an all electric IFR

panel and a two PC625 battery, two alternator electrical system. Would you

please make your comments specific to this setup?



Am I correct in assuming that there is an ideal setup for a two rear

battery, two alternator system, which is the Z-14 attached, and then there

is a more practical setup, which has the batteries grounded at the rear. Is

this correct? 



Would you please comment on the relative merits of these two different

approaches, and especially comment on any downside of both approaches? 



If you ground both rear batteries as suggested down the back to the

airframe, do you then set up your avionics ground bus at the panel simply by

connecting it to the firewall Ground? Are there any issues or concerns with

doing this?



 	  Quote: 	
		  From a purely electrical perspective, would it be preferable in our

situation (ignoring weight and balance questions for the moment) to have
	


either battery situated up the front somewhere? If yes, which would be

preferable to put up the front, and why?

I also have a couple of other questions on the attached Figure Z-14. Does

the single ground lead from both batteries to the front provide a single

source of total failure? And lastly, why have you specified the copper/brass

strap on the power side of the main battery in the attached Z-14?

Thank you once again for all your very generous input.



John Cleary





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nuckollsr(at)cox.net
Guest

Posted: Mon Apr 02, 2007 5:33 am Post subject: Rear Mounted Batteries - more questions

At 09:12 AM 4/1/2007 +1000, you wrote:



 	  Quote: 	
		  Hello 'Lectric Bob,



Thank you for all the fantastic effort you put into this group. It is

extremely helpful to those of us with zero earlier experience in this area.



I have read the Connection a couple of times and I have been pondering the

whole issue of batteries and locations and fat wires etc.



Attached is a schematic of a Z-14, architecture for rear batteries. This is

not your current Z-14, and I don't know now where I got this from, but it

very specifically states that the Aft Ground Buss is NOT Grounded to the

airframe.



My wife and I are building an RV-10. We are planning an all electric IFR

panel and a two PC625 battery, two alternator electrical system. Would you

please make your comments specific to this setup?



Am I correct in assuming that there is an ideal setup for a two rear

battery, two alternator system, which is the Z-14 attached, and then there

is a more practical setup, which has the batteries grounded at the rear. Is

this correct?


	


   Essentially yes. If one were building a composite aircraft, then a

   fat feeder for battery(-) leads to the firewall is REQUIRED. But in

   a metal airplane, one has the option of crafting a pristine system

   depicted in the sketch -or- taking advantage of the airframe as

   a power return for devices that are NOT potential victims to ground

   loop conducted noises.

 	  Quote: 	
		  Would you please comment on the relative merits of these two different

approaches, and especially comment on any downside of both approaches?



If you ground both rear batteries as suggested down the back to the

airframe, do you then set up your avionics ground bus at the panel simply by

connecting it to the firewall Ground? Are there any issues or concerns with

doing this?


	


     Nope. Your engine straps to the bolt at this ground also.

 	  Quote: 	
		   >From a purely electrical perspective, would it be preferable in our

situation (ignoring weight and balance questions for the moment) to have

either battery situated up the front somewhere? If yes, which would be

preferable to put up the front, and why?


	


    Batteries are the ultimate mitigator of CG problems. From

    the electrical perspective, we'd like to have all the starters,

    alternators and batteries be grouped together in something under

    2 cubic feet of common volume.  As a practical matter, batteries

    are placed where they need to go to accommodate other airframe design

    goals. As a major component of weight and volume, batteries are

    among the very few items where performance is not seriously

    compromised by moving them around.



 	  Quote: 	
		  I also have a couple of other questions on the attached Figure Z-14. Does

the single ground lead from both batteries to the front provide a single

source of total failure? And lastly, why have you specified the copper/brass

strap on the power side of the main battery in the attached Z-14?


	


    The crossfeed contactor, starter contactor and current limiter

    block can be mounted within inches of each other and "wired" with

    flat strap like the pictures found in this directory . . .



http://www.aeroelectric.com/Pictures/Wiring_Technique/



    The short straps are much easier to fabricate and install than

    very short hunks of fat wire with terminals.



    Bob . . .

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john_rv10(at)yahoo.com
Guest

Posted: Wed Apr 04, 2007 8:25 pm Post subject: Rear Mounted Batteries - more questions

Thanks Bob



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n277dl

Joined: 28 May 2007
Posts: 49
Location: Muscatine IA

Posted: Wed Apr 16, 2008 1:54 pm Post subject: Re: Rear Mounted Batteries - more questions - fat wires

Bob and list,

   Using the previously attached document as reference...



Assumptions... rear mounted batteries.  Main Bat Cntctr, Aux  Bat cntctr and Xfeed Cntctr all mounted in rear beside the batteries.  2awg ground wire to fwd central  gnd bus attached to the engine via stud through firewall. XFEED cnctr closed for starting.  2AWG wire from the same side of XFEED cntctr that the main bat cntctr is connected to starter cntctr.



Questions.... Can I then run appropriate sized wire (tbd) from the same side of the starter cntctr as the 2awg wire is attached to the main pwr bus?



If so, I also assume I would run appropriate sized wire ~8-10 awg (but not the heavy 2awg) from aux bat side of the XFEED to the Aux bus and use same wire to from the aux alt (prob 8 amp b&C alternator).  



Hope this makes sense.  Really just trying to understand if I can only run two fat wires from the batteries to the firewall if I want to ground at the firewall  or need to pull the extra "hot fat wire".  



thanks.  Doug

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_________________
Doug
"Fools" are always more creative than process people and will always find ways to ruin a perfectly good set of processes.

blackoaks(at)gmail.com
Guest

Posted: Tue Apr 22, 2008 9:46 am Post subject: Rear Mounted Batteries - more questions

Bob,  Very interesting discussion....   



We are (were) planning on using Z19RB architecture.  Granted, that requires 2 full size batteries (17- 20 AH) which we feel would provide sufficient backup power in the event of alternator failure, redundant power sources for the dual fuel pump and ignition required for the 20b Mazda rotory engine and avoids the added expense and complication of the extra alternator.  To insure good batteries one would be replaced each year.

 

Our thought was the two batteries would provide adequate power even during starts to prevent brownouts and a minimum of one and a half hours battery power (with load shedding of course) in the event of an alternator failure.  

 

We have not tested this battery endurance yet as the panel is not finished.

The brownout relay got me thinking about Z13/8 again....

Any thoughts????



On Tue, Apr 22, 2008 at 6:49 AM, Robert L. Nuckolls, III <nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)> wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)cox.net (nuckolls.bob(at)cox.net)>

  



 At 03:33 PM 4/18/2008 -0700, you wrote:

 



	




-- 

John McMahon

Lancair Super ES, S/N 170, N9637M (Reserved)  [quote][b]

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dennis.glaeser(at)eds.com
Guest

Posted: Tue Apr 22, 2008 11:14 am Post subject: Rear Mounted Batteries - more questions

I have essentially the Z19RB architecture on my Subaru powered RV-7A.

For starting, I leave the Aux Bat master OFF and turn on the E-Bus which

means the starter uses only the main battery and the aux battery powers

the electronics without brownout.  Once started, the Aux master comes on

and the E-bus switch goes off.  Works great.  



Dennis Glaeser



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

From:		John McMahon 



Bob,  Very interesting discussion....



We are (were) planning on using Z19RB architecture.  Granted, that

requires

2 full size batteries (17- 20 AH) which we feel would provide sufficient

backup power in the event of alternator failure, redundant power sources

for

the dual fuel pump and ignition required for the 20b Mazda rotory engine

and

avoids the added expense and complication of the extra alternator.  To

insure good batteries one would be replaced each year.



Our thought was the two batteries would provide adequate power even

during

starts to prevent brownouts and a minimum of one and a half hours

battery

power (with load shedding of course) in the event of an alternator

failure.

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