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RG Batteries: I learned something last night

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nuckolls.bob(at)aeroelect
Guest

Posted: Sat Oct 29, 2011 7:28 am Post subject: RG Batteries: I learned something last night

That bench test battery I featured in a posting

a few days ago had not be cap-checked in several years.

The thing is over ten years old and has yielded a

great return on investment.



I did a load test on this battery about a week ago.

It dumped about 300A for 15 seconds at the 70F mark

on the load meter. A value that is less than 1/2 the

as-new capability.



Just for grins, I pulled out the CBAII battery tester.

The bench battery had been on a maintainer for a couple days.



I did a 6A discharge test. The value I use as exemplary

of most of my instrumentation experiments. The battery

delivered 24+ a.h. of useful energy! Going to the

factory data on this battery we see:



http://www.aeroelectric.com/Pictures/Curves/33AH_12V_Capacity_vs_Load.gif

The factory says a 6.6A load will deplete this battery

in about 4 hours . . . or 24+ a.h.



In years past, my teachers modeled the battery as a large

array of cells connected in a series-parallel configuration

with EACH cell offering some finite energy value combined

with it's own source impedance. If you loose 1/2 the cell

in the full-up array, energy drops by 1/2 but source impedance

doubles.



This experiment last night showed that while the source

impedance for the battery had doubled (1/2 the cranking

snort), the total energy available was still almost as-new!

This means that the gazillion itty-bitty cell analogy is not

quite accurate. Those cells can experience a rise in

source impedance while still offering their original

energy capability.



This battery as-new will deliver 9V at over 800A for

15 seconds. This suggests a source impedance of

(12-9)/800 = .004 ohms. It now produces about 300A

so the new source impedance is (12-9)/300 = .010

ohms.



So while the impedance has doubled, the available

energy at 6A loading has been barely affected . . . if

at all. A rise from .004 to .010 ohms source impedance

has little influence on a test load of (12/6)= 2 Ohms.



This argues with any analogy that suggests a "dead"

micro-cell in a battery becomes totally disconnected

from the array. It suggests that individual cells

can demonstrate an ability to store and regurgitate

energy while experiencing an independent and unrelated

rise in source impedance.



This discovery suggests that it is possible for a

battery to meet battery-only-ops requirements while

demonstrating reduced cranking performance. This ol'

dog is still learning . . . and my grey haired bench

test battery is still in service.



   Bob . . .

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klehman(at)albedo.net
Guest

Posted: Sun Oct 30, 2011 7:21 am Post subject: RG Batteries: I learned something last night

I can report results that seem similar. For a new 9AH dekka vrla battery 

discharged at 6 amps (2 ohm resistance) I measure 56 minutes to 11.00 

volts or 5.6 AH.



For a 6+ year old but 5 years in service identical battery (420 flight 

hours) that has never been deep discharged or been on a maintainer, I 

measure 52 minutes to 11.00 volts or 5.2 AH again at 6 amps discharge 

rate. All tests were done with the battery stabilized at a 66*F basement 

room temperature for several days after top up with a Schumaker 1162.



I don't have an easy way to compare the cranking capabilities other than 

last winter the two paralleled batts in my Z-14 system seemed to crank a 

bit slower than normal. It cranked fine all summer but I have just 

replaced the oldest battery anyway. Hasn't been much colder than 

freezing yet to compare this winter. I too am surprised that the old 

battery delivered 93% of the capacity of the newer one at a 6 amp 

discharge rate.



I'll attempt to compare the current flow from each battery while 

cranking (clamp on dc ammeter) the next time I fly. (I have the 

automatic parallel option during cranking). Should give an indication of 

how another 4 year in service batt compares to the new one for cranking.



Ken



On 29/10/2011 11:25 AM, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckolls.bob(at)aeroelectric.com>



 That bench test battery I featured in a posting

 a few days ago had not be cap-checked in several years.

 The thing is over ten years old and has yielded a

 great return on investment.



 I did a load test on this battery about a week ago.

 It dumped about 300A for 15 seconds at the 70F mark

 on the load meter. A value that is less than 1/2 the

 as-new capability.



 Just for grins, I pulled out the CBAII battery tester.

 The bench battery had been on a maintainer for a couple days.



 I did a 6A discharge test. The value I use as exemplary

 of most of my instrumentation experiments. The battery

 delivered 24+ a.h. of useful energy! Going to the

 factory data on this battery we see:



 http://www.aeroelectric.com/Pictures/Curves/33AH_12V_Capacity_vs_Load.gif

 The factory says a 6.6A load will deplete this battery

 in about 4 hours . . . or 24+ a.h.



 In years past, my teachers modeled the battery as a large

 array of cells connected in a series-parallel configuration

 with EACH cell offering some finite energy value combined

 with it's own source impedance. If you loose 1/2 the cell

 in the full-up array, energy drops by 1/2 but source impedance

 doubles.



 This experiment last night showed that while the source

 impedance for the battery had doubled (1/2 the cranking

 snort), the total energy available was still almost as-new!

 This means that the gazillion itty-bitty cell analogy is not

 quite accurate. Those cells can experience a rise in

 source impedance while still offering their original

 energy capability.



 This battery as-new will deliver 9V at over 800A for

 15 seconds. This suggests a source impedance of

 (12-9)/800 = .004 ohms. It now produces about 300A

 so the new source impedance is (12-9)/300 = .010

 ohms.



 So while the impedance has doubled, the available

 energy at 6A loading has been barely affected . . . if

 at all. A rise from .004 to .010 ohms source impedance

 has little influence on a test load of (12/6)= 2 Ohms.



 This argues with any analogy that suggests a "dead"

 micro-cell in a battery becomes totally disconnected

 from the array. It suggests that individual cells

 can demonstrate an ability to store and regurgitate

 energy while experiencing an independent and unrelated

 rise in source impedance.



 This discovery suggests that it is possible for a

 battery to meet battery-only-ops requirements while

 demonstrating reduced cranking performance. This ol'

 dog is still learning . . . and my grey haired bench

 test battery is still in service.

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bicyclop(at)pacbell.net
Guest

Posted: Sun Oct 30, 2011 9:05 pm Post subject: RG Batteries: I learned something last night

A few years back, we had a dead short on the battery       cable before the contactor that drained the battery dead, dead,       dead. I arrived and removed the short after about 2 hours. The       battery read ~ 5v at that time. Charged it overnight and put it       back in service. Several weeks later I replaced it when it failed       to start the engine, charged it and did a CBA II capacity test on       it at 4 amps. It delivered just under 24 ah - not bad for a       severely abused 24 ah battery. I'm still using it as a shop       battery.

       

       Pax,

       

       Ed Holyoke

     

     On 10/29/2011 8:25 AM, Robert L. Nuckolls, III wrote:     [quote]--> AeroElectric-List message posted by: "Robert L.       Nuckolls, III" <nuckolls.bob(at)aeroelectric.com> (nuckolls.bob(at)aeroelectric.com)       

       

       That bench test battery I featured in a posting       

       a few days ago had not be cap-checked in several years.       

       The thing is over ten years old and has yielded a       

       great return on investment.       

       

       I did a load test on this battery about a week ago.       

       It dumped about 300A for 15 seconds at the 70F mark       

       on the load meter. A value that is less than 1/2 the       

       as-new capability.       

       

       Just for grins, I pulled out the CBAII battery tester.       

       The bench battery had been on a maintainer for a couple days.       

       

       I did a 6A discharge test. The value I use as exemplary       

       of most of my instrumentation experiments. The battery       

       delivered 24+ a.h. of useful energy! Going to the       

       factory data on this battery we see:       

       

 http://www.aeroelectric.com/Pictures/Curves/33AH_12V_Capacity_vs_Load.gif       

       

       

       The factory says a 6.6A load will deplete this battery       

       in about 4 hours . . . or 24+ a.h.       

       

       In years past, my teachers modeled the battery as a large       

       array of cells connected in a series-parallel configuration       

       with EACH cell offering some finite energy value combined       

       with it's own source impedance. If you loose 1/2 the cell       

       in the full-up array, energy drops by 1/2 but source impedance       

       doubles.       

       

       This experiment last night showed that while the source       

       impedance for the battery had doubled (1/2 the cranking       

       snort), the total energy available was still almost as-new!       

       This means that the gazillion itty-bitty cell analogy is not       

       quite accurate. Those cells can experience a rise in       

       source impedance while still offering their original       

       energy capability.       

       

       This battery as-new will deliver 9V at over 800A for       

       15 seconds. This suggests a source impedance of       

       (12-9)/800 = .004 ohms. It now produces about 300A       

       so the new source impedance is (12-9)/300 = .010       

       ohms.       

       

       So while the impedance has doubled, the available       

       energy at 6A loading has been barely affected . . . if       

       at all. A rise from .004 to .010 ohms source impedance       

       has little influence on a test load of (12/6)= 2 Ohms.       

       

       This argues with any analogy that suggests a "dead"       

       micro-cell in a battery becomes totally disconnected       

       from the array. It suggests that individual cells       

       can demonstrate an ability to store and regurgitate       

       energy while experiencing an independent and unrelated       

       rise in source impedance.       

       

       This discovery suggests that it is possible for a       

       battery to meet battery-only-ops requirements while       

       demonstrating reduced cranking performance. This ol'       

       dog is still learning . . . and my grey haired bench       

       test battery is still in service.       

       

       

       

         Bob . . . 

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

     [b]

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