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RG batteries with 35A generators

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N6030X(at)DaveMorris.com
Guest

Posted: Sun Sep 03, 2006 10:58 am Post subject: RG batteries with 35A generators

Bob,



I have been doing a lot of reading lately, and somewhere I was 

reading an article on RG batteries - now I cannot find it anywhere - 

that said if your aircraft system is a generator instead of an 

alternator, and if it is a 35A or less system, you should not use an 

RG battery.  I believe I remember the statement came from a Concorde 

spokesperson.



Do you know anything about such a limitation?



Thanks

Dave Morris

Mooney M20A

N6030X

nuckollsr(at)cox.net
Guest

Posted: Sun Sep 03, 2006 2:08 pm Post subject: RG batteries with 35A generators

At 01:54 PM 9/3/2006 -0500, you wrote:



 	  Quote: 	
		  



Bob,



I have been doing a lot of reading lately, and somewhere I was reading an 

article on RG batteries - now I cannot find it anywhere - that said if 

your aircraft system is a generator instead of an alternator, and if it is 

a 35A or less system, you should not use an RG battery.  I believe I 

remember the statement came from a Concorde spokesperson.



Do you know anything about such a limitation?


	


   I cannot imagine why . . . I'll be talking with Skip

   next week on other matters, I'll ask him if this is a

   bit of wisdom from Concorde. But as far as I can deduce,

   the technology of the engine driven power source is not

   linked to the suitability of RG vs. any other battery.



   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       >

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

jm(at)10squaredcorp.com
Guest

Posted: Sun Sep 03, 2006 7:07 pm Post subject: RG batteries with 35A generators

Data point - There is an SB for Stinsons that provides a list of 

current batteries that should be used in the 108 series which have 

generators. RG batteries are on the list, but not the extra capacity 

versions with stated reason being the charging system cannot handle 

the extra capacity.



On Sunday 03 September 2006 22:04, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckollsr(at)cox.net>



 At 01:54 PM 9/3/2006 -0500, you wrote:

 >

 > <N6030X(at)DaveMorris.com>

 >

 >Bob,

 >

 >I have been doing a lot of reading lately, and somewhere I was

 > reading an article on RG batteries - now I cannot find it

 > anywhere - that said if your aircraft system is a generator

 > instead of an alternator, and if it is a 35A or less system, you

 > should not use an RG battery.  I believe I remember the statement

 > came from a Concorde spokesperson.

 >

 >Do you know anything about such a limitation?



    I cannot imagine why . . . I'll be talking with Skip

    next week on other matters, I'll ask him if this is a

    bit of wisdom from Concorde. But as far as I can deduce,

    the technology of the engine driven power source is not

    linked to the suitability of RG vs. any other battery.



    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: Tue Sep 05, 2006 3:54 am Post subject: RG batteries with 35A generators

At 11:10 PM 9/3/2006 +0000, you wrote:



 	  Quote: 	
		  



Data point - There is an SB for Stinsons that provides a list of

current batteries that should be used in the 108 series which have

generators. RG batteries are on the list, but not the extra capacity

versions with stated reason being the charging system cannot handle

the extra capacity.


	




   This is a WAG but I'd bet that the assertion developed from

   a lack of understanding of a long standing "rule of thumb"

   in battery/generator sizing.



   While not explicit in the FARS, AC43-13 suggests that you

   reserve 20% of generator/alternator capacity for the recharging

   of a dead battery. Another notation in AC43-13 suggests that

   a battery should be recharged in 60-90 minutes of flight. Both

   of these numbers were pulled from where the sun don't shine.



   Now, suppose you have a nice ol' C-140 with a 20A generator

   and 24 AH battery. If you run that battery down, there's no

   way that you can load the generator to 16A and recharge the

   battery in 90 minutes with the 4A left over. Of course, that

   airplane left the factory only with lights installed and

   anyone who chose to launch with a dead battery could run

   essentially 'dark' for an hour or so and get the battery back

   up.



   Suppose your airplane came from the factory with a 40A alternator

   then according to one rule-of-thumb, we can fit the machine with

   a 32A running load leaving 8A for charging. Hmmm . . . this means

   we should only install a 12 a.h. battery so that 8A will get it

   topped off in 90 minutes.



   How about we upgrade to a 60A alternator. If the airplane left

   the factory certified with 8A of headroom, logic suggests that

   we could now carry a 52A running load and still meet the original

   intent of recharging our 12 a.h. battery in 90 minutes. But no,

   somebody will latch onto the 20% headroom statement and say

   that you need to reserve 12A of headroom. Okay, now we can

   recharge our tiny 12 a.h. battery in one hour. Good deal.



   But suppose you want to upgrade to a 24 a.h. battery. Now

   with 12A of headroom, we'll need 2 hours to recharge the 24 a.h.

   battery. My bad.



   Bottom line is that the best way to size an alternator/battery

   combination is to know what your operating requirements are,

   what the limitations are for getting the battery recharged under

   the rare condition that you should decide to launch with a dead

   battery. Then adjust operating conditions for the flight

   meet the battery's needs in a whatever you decide is a reasonable

   period of time while meeting minimum needs for operating equipment.



   The prohibition for the higher capacity battery in the Stinson

   is probably based on the 20% rule hat-dance and not upon any

   understanding of performance by those who would prohibit or

   individuals who can understand the new limitations for recharging

   and adjust their operations accordingly.



   It's the blind leading the deaf to follow rules by the ignorant

   so that pilots are not required to understand. Grand recipe for

   success, no? Sounds like groundwork for a juicy dark-n-stormy

   night story.



   Bob . . .

RURUNY(at)aol.com
Guest

Posted: Tue Sep 05, 2006 8:44 pm Post subject: RG batteries with 35A generators

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.

  

 Brian

  

  

  

 Bob,



I have been doing a lot of reading lately, and somewhere I was  

reading an article on RG batteries ....

  

 Thanks

Dave Morris

Mooney  M20A

N6030X



  [quote][b]

N6030X(at)DaveMorris.com
Guest

Posted: Wed Sep 06, 2006 5:25 am Post subject: RG batteries with 35A generators

Ah, yes, there it is in AOPA Pilot, September issue, page 136:



"The low internal resistance of RG batteries is the second reason 

(more plate area is the first) they deliver more power and why they 

accept a charge faster.  Accepting more charge can cause small 

generators to overheat.  Skip Koss of Concorde Battery said any 

airplane with a generator with an output of less than 50 amps should 

use flooded-cell batteries for this reason."



Presumably that would apply only if the battery were needing a large 

charge and Charge + Other Load was greater than the rating of the generator?



I have a 1960 Mooney M20A with a 35A generator, and I would think 

that as long as I'm not taking off at night into the ice with a fully 

discharged battery, needing my landing lights and pitot heat and a 

heavy battery charge, this battery should be OK.



Dave Morris

N6030X



At 11:44 PM 9/5/2006, you wrote:

 	  Quote: 	
		  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.



Brian



Bob,



I have been doing a lot of reading lately, and somewhere I was

reading an article on RG batteries ....



Thanks

Dave Morris

Mooney M20A

N6030X

nuckollsr(at)cox.net
Guest

Posted: Wed Sep 06, 2006 5:26 am Post subject: RG batteries with 35A generators

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



 	  Quote: 	
		  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 . . .

nuckollsr(at)cox.net
Guest

Posted: Wed Sep 06, 2006 6:39 am Post subject: RG batteries with 35A generators

At 08:23 AM 9/6/2006 -0500, you wrote:



I'm mystified by this. Alternators are inherently current limited.

A 'cold' alternator will put out only a handful of amps over and above

the nameplate rating. Generators have no such inherent protection and

require current sensing and control feature as part of the regulator.

This is accomplished with the center of three relay-looking thingys

in . . .



http://www.aeroelectric.com/Pictures/Regulators/GenReg_2A.jpg



As a systems integrator looking over the specs of a generator/regulator

combination, I'd be disappointed if the data said something like, "Caution,

do not operate this system in the current limited mode for extended

periods of time." Obviously, current limiting is there to protect the

generator from it's willingness to self-destruct . . . but I'm mystified

as to why we should take special notice of current limited operations

to run systems aboard the airplane as opposed to charging a "too big"

battery.



If there are issues with respect to extended current limited operations

for generators, I'd expect these to be covered in the hot-day, max-load,

min-cooling tests customarily conducted at cert-time for the generator.



I've forwarded a copy of this note to Skip. I have no doubt that he

will come forward and enlighten us as to the underlying reasons for

Concorde's suggestion.



Bob . . .

 	  Quote: 	
		  



Ah, yes, there it is in AOPA Pilot, September issue, page 136:



"The low internal resistance of RG batteries is the second reason (more 

plate area is the first) they deliver more power and why they accept a 

charge faster.  Accepting more charge can cause small generators to 

overheat.  Skip Koss of Concorde Battery said any airplane with a 

generator with an output of less than 50 amps should use flooded-cell 

batteries for this reason."



Presumably that would apply only if the battery were needing a large 

charge and Charge + Other Load was greater than the rating of the generator?



I have a 1960 Mooney M20A with a 35A generator, and I would think that as 

long as I'm not taking off at night into the ice with a fully discharged 

battery, needing my landing lights and pitot heat and a heavy battery 

charge, this battery should be OK.



Dave Morris

N6030X



At 11:44 PM 9/5/2006, 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.

>

>Brian

chaztuna(at)adelphia.net
Guest

Posted: Wed Sep 06, 2006 8:06 am Post subject: RG batteries with 35A generators

---- "Robert L. Nuckolls wrote: 

 	  Quote: 	
		   

 

 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

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Wed Sep 06, 2006 8:39 am Post subject: RG batteries with 35A generators

Unfortunately, AOPA hasn't chosen to put that article on line, yet. It was

written by Steven Ells. It apparently gives www.aeroelectric.com and the

two battery companies web links. Title is "Charge It" under their Airframe

and Power Plant column.



 	  Quote: 	
		   

>     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

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

brian-av(at)lloyd.com
Guest

Posted: Wed Sep 06, 2006 10:15 am Post subject: RG batteries with 35A generators

Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckollsr(at)cox.net>

 

 At 08:23 AM 9/6/2006 -0500, you wrote:

 

 I'm mystified by this. Alternators are inherently current limited.

 A 'cold' alternator will put out only a handful of amps over and above

 the nameplate rating. Generators have no such inherent protection and

 require current sensing and control feature as part of the regulator.

 This is accomplished with the center of three relay-looking thingys

 in . . .


	


Well, here is some speculation, worth every penny you are paying for it.



The actual generating part of a generator is the armature, not the

stator. Less surface area from which to rid itself of heat. Also, the

generator has the commutator and its brushes. These are pretty lossy and

they don't have a good way to get rid of heat either, hence another

bottle neck. You are also likely to have less wire in the armature so

you don't have as much I*R loss to limit current.



I also suspect that even though alternators and generators have output

ratings, what they spec as "continuous duty" is probably not really

continuous duty. I suspect that the real, "you can run it this hard

until the cows come home," value is something smaller.



If you just knew the temperature rise of the various components you

could probably figure out what the real ratings are.



And his is an interesting but probably not-to-useful observation on

limits. The Chinese actually put multiple maximum limits on their

engines. It is like, "you can run it this hard for 5 minutes, this hard

for 10 minutes, this hard for 15 minutes, this hard for one hour, and

this hard for ever and ever." This makes a LOT of sense to me.



Brian Lloyd

nuckollsr(at)cox.net
Guest

Posted: Wed Sep 06, 2006 4:13 pm Post subject: RG batteries with 35A generators

At 11:14 AM 9/6/2006 -0700, you wrote:



 	  Quote: 	
		  



Robert L. Nuckolls, III wrote:

 > 

 > <nuckollsr(at)cox.net>

 >

 > At 08:23 AM 9/6/2006 -0500, you wrote:

 >

 > I'm mystified by this. Alternators are inherently current limited.

 > A 'cold' alternator will put out only a handful of amps over and above

 > the nameplate rating. Generators have no such inherent protection and

 > require current sensing and control feature as part of the regulator.

 > This is accomplished with the center of three relay-looking thingys

 > in . . .



Well, here is some speculation, worth every penny you are paying for it.



The actual generating part of a generator is the armature, not the

stator. Less surface area from which to rid itself of heat. Also, the

generator has the commutator and its brushes. These are pretty lossy and

they don't have a good way to get rid of heat either, hence another

bottle neck. You are also likely to have less wire in the armature so

you don't have as much I*R loss to limit current.


	


    Understand  . . . and agree

 	  Quote: 	
		  I also suspect that even though alternators and generators have output

ratings, what they spec as "continuous duty" is probably not really

continuous duty. I suspect that the real, "you can run it this hard

until the cows come home," value is something smaller.



If you just knew the temperature rise of the various components you

could probably figure out what the real ratings are.


	


   That's where I get crosswise in the road. In TC aviation, one

   is generally expected to deliver to requirements and to fully

   explain ratings and limits for products.

 	  Quote: 	
		  And his is an interesting but probably not-to-useful observation on

limits. The Chinese actually put multiple maximum limits on their

engines. It is like, "you can run it this hard for 5 minutes, this hard

for 10 minutes, this hard for 15 minutes, this hard for one hour, and

this hard for ever and ever." This makes a LOT of sense to me.


	


    Yup, we do that too. Starter generators on some of our

    products are qualified for continuous duty performance

    (nameplate value) and then tested for short term overloads

    under certain conditions . . . like a 30-minute requirement

    for getting down from altitude with one generator dead and all

    the de-ice equipment turned on.



    I've been herding electrons in this venue for a long time

    and Skip's assertions about battery sizing due to some failure

    of the generator to meet nameplate performance continuously

    is a first.  Certification generally demands that you make

    ALL limits known to both system integrators and ultimately

    pilots . . . if the knowledge is necessary to prevent accidental

    damage to hardware.



    Now, it may well be that Skip reports some instances where

    folks have put fat RG batteries into 1946 C-140's with

    20A generators and the customer had "problems". I'm skeptical

    that any detailed failure analysis was conducted and I'll

    further confess to no knowledge of how generators were certified

    in 1946. I do have a copy of CAR3 somewhere, I'll go dig that

    out.



    Not a really big deal for us alternator drivers but I would

    like to understand more. Will let you know what I find out.



    Bob . . .

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