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AOPA battery article

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nuckollsr(at)cox.net
Guest

Posted: Wed Sep 06, 2006 6:31 pm Post subject: AOPA battery article

At 09:04 AM 9/6/2006 -0700, you wrote:

 	  Quote: 	
		  ---- "Robert L. Nuckolls wrote:

 > 

 <nuckollsr(at)cox.net>

 >

 > At 12:44 AM 9/6/2006 -0400, you wrote:

 >

 > >The article is in the AOPA pilot magazine Aug or Sept issue, on aircraft

 > >batteries.

 > >Bobs name is mentioned right in the introduction of the article and later

 > >near the end with a reference to the connection. I have a rotax 912 

 with a

 > >20Amp generater, was setting up

 > >for an RG battery from B&C, but took out the vented battery box I got 

 with

 > >my kit and dusted it off wondering if this article is correct.

 >

 >     I don't subscribe to AOPA Pilot any more so I missed

 >     the article. It would be interesting/useful to review

 >     it. If someone could scan it and email it to me, I'd

 >     appreciate it.

 >

 >     Bob . . .



Listers,

  The relevent article is on page 133 of the September issue

Charlie Kuss


	


   Dave sent me a copy. It's an innocuous piece and relatively

   accurate. If I were to expand beyond where it stopped short

   would be to explain the value in KNOWING what your endurance

   loads are and KNOWING if your battery is likely to support

   this load for whatever endurance YOU decide.



   There was one rather glaring error on the top of page

   138 where it's stated that a 1C rated battery is discharged

   at 2C, it will deliver energy for 1/2 hour. Twice the

   load is ALWAYS less than half the previous capacity. By

   the same token, 0.1C load is always more than 10X the

   1C label capacity.



   Exemplar capacity vs. discharge rates are illustrated

   in . . .



http://www.aeroelectric.com/Pictures/Curves/37AH_Capacity_vs_Load.gif



   and



http://www.aeroelectric.com/Pictures/Curves/17AH_Capcity_vs_Load.gif



   These graphs from manufacturer's data show that increasing

   loads increases internal losses and that apparent

   capacity drops as load increases.



   Our perpetual parents on the TC side have decided that

   "30 minutes" is the magic number for endurance and

   "85% of label capacity" is end of life for the battery.

   This makes the certification effort easy and makes FBOs

   task of selling batteries easier. This is an excellent example of

   standardization that benefits the manufacturers and

   regulators while limiting the owner's ability to tailor

   realistic targets to match his/her own mission requirements.



   Neither one of the 30-minute/85% assertions suggest that

   the owner/operator of an airplane might possess tools and

   be willing to acquire skills needed increase personal endurance

   target to say 1 hour. Or, take the time to monitor a battery

   with an eye toward meeting the endurance level such that

   70% of label capacity is the TRUE end of life for the battery

   in that particular airplane.



   Aren't you guys glad you don't have to salute those

   flags?  I still like "duration of fuel aboard" for

   endurance and "pitch it when e-bus loads cannot be

   supported for duration of fuel aboard." Of course,

   on the OBAM side of the house we're free to select

   and operate to our personal design goals.

        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       >

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

cleone(at)rr1.net
Guest

Posted: Thu Sep 07, 2006 7:31 am Post subject: AOPA battery article

Bob,  What does OBAM mean?



At 09:29 PM 9/6/2006, you wrote:

 	  Quote: 	
		  

<nuckollsr(at)cox.net>



At 09:04 AM 9/6/2006 -0700, you wrote:

>---- "Robert L. Nuckolls wrote:

> > 

> III" <nuckollsr(at)cox.net>

> >

> > At 12:44 AM 9/6/2006 -0400, you wrote:

> >

> > >The article is in the AOPA pilot magazine Aug or Sept issue, on aircraft

> > >batteries.

> > >Bobs name is mentioned right in the introduction of the article and later

> > >near the end with a reference to the connection. I have a rotax 

> 912 with a

> > >20Amp generater, was setting up

> > >for an RG battery from B&C, but took out the vented battery box 

> I got with

> > >my kit and dusted it off wondering if this article is correct.

> >

> >     I don't subscribe to AOPA Pilot any more so I missed

> >     the article. It would be interesting/useful to review

> >     it. If someone could scan it and email it to me, I'd

> >     appreciate it.

> >

> >     Bob . . .

>

>Listers,

>  The relevent article is on page 133 of the September issue

>Charlie Kuss



   Dave sent me a copy. It's an innocuous piece and relatively

   accurate. If I were to expand beyond where it stopped short

   would be to explain the value in KNOWING what your endurance

   loads are and KNOWING if your battery is likely to support

   this load for whatever endurance YOU decide.



   There was one rather glaring error on the top of page

   138 where it's stated that a 1C rated battery is discharged

   at 2C, it will deliver energy for 1/2 hour. Twice the

   load is ALWAYS less than half the previous capacity. By

   the same token, 0.1C load is always more than 10X the

   1C label capacity.



   Exemplar capacity vs. discharge rates are illustrated

   in . . .



http://www.aeroelectric.com/Pictures/Curves/37AH_Capacity_vs_Load.gif



   and



http://www.aeroelectric.com/Pictures/Curves/17AH_Capcity_vs_Load.gif



   These graphs from manufacturer's data show that increasing

   loads increases internal losses and that apparent

   capacity drops as load increases.



   Our perpetual parents on the TC side have decided that

   "30 minutes" is the magic number for endurance and

   "85% of label capacity" is end of life for the battery.

   This makes the certification effort easy and makes FBOs

   task of selling batteries easier. This is an excellent example of

   standardization that benefits the manufacturers and

   regulators while limiting the owner's ability to tailor

   realistic targets to match his/her own mission requirements.



   Neither one of the 30-minute/85% assertions suggest that

   the owner/operator of an airplane might possess tools and

   be willing to acquire skills needed increase personal endurance

   target to say 1 hour. Or, take the time to monitor a battery

   with an eye toward meeting the endurance level such that

   70% of label capacity is the TRUE end of life for the battery

   in that particular airplane.



   Aren't you guys glad you don't have to salute those

   flags?  I still like "duration of fuel aboard" for

   endurance and "pitch it when e-bus loads cannot be

   supported for duration of fuel aboard." Of course,

   on the OBAM side of the house we're free to select

   and operate to our personal design goals.

        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       >

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

nuckollsr(at)cox.net
Guest

Posted: Thu Sep 07, 2006 7:57 am Post subject: AOPA battery article

At 10:31 AM 9/7/2006 -0500, you wrote:



 	  Quote: 	
		  



Bob,  What does OBAM mean?


	


  "Owner Built and Maintained" as opposed to "Amateur Built" or "Experimental"



  See archives at:



http://www.matronics.com/searching/search.html



  Search the AeroElectric List for the phrase

  "ABEA"



  Bob . . .

trigo(at)mail.telepac.pt
Guest

Posted: Thu Sep 07, 2006 8:27 am Post subject: AOPA battery article

OBAM stands for Owner Built and Maintained, which the designation that Bob 

prefers to call Experimental / Amateur Built aircraft.



Carlos

---

Kellym

Joined: 10 Jan 2006
Posts: 1700
Location: Sun Lakes AZ

Posted: Thu Sep 07, 2006 8:43 am Post subject: AOPA battery article

Bob,

Would you care to comment with regard to the article's assertion that  

generators under 50 amps are adversely affected by the high capacity  

RG35 batteries, in particular, as opposed to small alternators? Or  

have you heard from the gentleman at Concorde?

I know alternators are a little more self limiting, but it seems like  

the larger charging demand from the low resistance of that battery  

would have adverse effects on both generators and alternators.



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



 	  Quote: 	
		   

 <nuckollsr(at)cox.net>



 At 10:31 AM 9/7/2006 -0500, you wrote:



>

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

brian-av(at)lloyd.com
Guest

Posted: Thu Sep 07, 2006 8:49 am Post subject: AOPA battery article

On Wed, 2006-09-06 at 19:29, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		      These graphs from manufacturer's data show that increasing

    loads increases internal losses and that apparent

    capacity drops as load increases.


	


Bob:



I am going to pick a nit here. At least twice I have seen you mention

losses in a battery in relationship to the change in battery capacity

with change in discharge rate. The interesting thing is, this

relationship occurs even when losses are not at issue, i.e. in batteries

intended for high-reliability stationary applications where they can

afford to construct massive plate structures where I*R losses are

virtually nonexistent. The relationship is still an exponential one and

was discovered by a gentleman named Peukert, hence it is named Peukert's

law.



The real reason has to do with the rate at which the electrolyte

diffuses into the active area of the plate and how the active portion of

the plate changes with time at different rates of discharge.



Good information about this can be found at

"http://en.wikipedia.org/wiki/Peukert's_Law". The first external link is

to a PDF file with a good discussion (with pictures!) of the actual

chemical behavior of the plate of a battery and why Peukert's exponent

applies.



Yes, this is a small thing and probably not worth worrying about when

building aircraft electrical systems since you will always be

discharging the battery on you e-bus at the same rate every time. But

pedantic people (like me) care about such little things. 



Brian Lloyd

ainut(at)hiwaay.net
Guest

Posted: Thu Sep 07, 2006 10:15 am Post subject: AOPA battery article

Owner Built and Maintained.  Invented while searching for a politically 

correct term for homebuilt.

David M.

Cleone Markwell wrote:

 	  Quote: 	

 Bob,  What does OBAM mean?

 At 09:29 PM 9/6/2006, you wrote:

> 

> <nuckollsr(at)cox.net>

>

> At 09:04 AM 9/6/2006 -0700, you wrote:

>

<<<snip>>>

mprather(at)spro.net
Guest

Posted: Thu Sep 07, 2006 11:27 am Post subject: AOPA battery article

Picking nits here...  Maybe it's just me, but I think "politically

correct" has taken on a rather negative connotation.

I believe "OBAM," in some ways, more accurately reflects our aircraft. 

Very often (usually), the airplanes we build and operate are direct copies

of other aircraft.  They are built for entertainment and transportation. 

Little aerodynamic study or scientific endeavor is accomplished (and

that's okay).  Experimentation is minimal.

"OBAM," as you say, also may put a better spin on things with the

uninformed public than do other terms that describe what we are doing...

Regards,

Matt-

 	  Quote: 	

 Owner Built and Maintained.  Invented while searching for a politically

 correct term for homebuilt.

 David M.

 Cleone Markwell wrote:

> 

> <cleone(at)rr1.net>

>

> Bob,  What does OBAM mean?

>

> At 09:29 PM 9/6/2006, you wrote:

>

>> 

>> <nuckollsr(at)cox.net>

>>

>> At 09:04 AM 9/6/2006 -0700, you wrote:

>>

 <<<snip>>>

nuckollsr(at)cox.net
Guest

Posted: Fri Sep 08, 2006 4:56 am Post subject: AOPA battery article

At 09:42 AM 9/7/2006 -0700, you wrote:



 	  Quote: 	
		  



Bob,

Would you care to comment with regard to the article's assertion that

generators under 50 amps are adversely affected by the high capacity

RG35 batteries, in particular, as opposed to small alternators? Or

have you heard from the gentleman at Concorde?

I know alternators are a little more self limiting, but it seems like

the larger charging demand from the low resistance of that battery

would have adverse effects on both generators and alternators.


	


   Working on that. Received a clarification from Skip and guess what?

   Root cause for the recommendation has nothing to do with "overloading

   a generator." I'm editing the thing right now. Might have it done

   tomorrow.



   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       >

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

cleone(at)rr1.net
Guest

Posted: Sat Sep 09, 2006 7:00 pm Post subject: AOPA battery article

At 11:24 AM 9/7/2006, you wrote:

 [quote]--> AeroElectric-List message posted by: "Carlos Trigo" <trigo(at)mail.telepac.pt>



 OBAM stands for Owner Built and Maintained, which the designation that Bob prefers to call Experimental / Amateur Built aircraft.



 Carlos    Thanks Carlos, now I know.  Cleone



 

 ---

cleone(at)rr1.net
Guest

Posted: Sat Sep 09, 2006 7:12 pm Post subject: AOPA battery article

At 01:10 PM 9/7/2006, you wrote:

 [quote]--> AeroElectric-List message posted by: "David M." <ainut(at)hiwaay.net>



 Owner Built and Maintained.  Invented while searching for a politically correct term for homebuilt.



 David M.  Thanks David.  Cleone



 

 Cleone Markwell wrote:



  	  Quote: 	
		  --> AeroElectric-List message posted by: Cleone Markwell <cleone(at)rr1.net>



 Bob,  What does OBAM mean?



 



 At 09:29 PM 9/6/2006, you wrote:



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



 At 09:04 AM 9/6/2006 -0700, you wrote:

 	
	
<<<snip>>>



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