[Test-Equipment] "Conductance" battery checker

[Raymond LaRue]

Bob,
Of course you are correct in all you say.  

However going a little further and quoting an Alpha Power Technologies white paper on the subject:

"Conductance Testing: Conductance measurements, sometimes called acceptance measurements, are performed by applying an AC voltage of a known frequency and amplitude across a battery and observing the current that flows as a result.  Conductance is the ratio of the AC current that is in-phase with the AC voltage compared to the amplitude of the AC voltage producing the current.  Test results are expressed in Siemens or Mhos..."

"The conductance value of a battery reflects the integrity... and actual battery state of charge"...  

"Correlation of Conductance to capacity:  There is no direct correlation between conductance and the available capacity from a battery;..." (However)...

"Years of evaluating conductance test technologies and many attempts to establish a correlation between capacity and conductance has shown the least correlation exists when the battery is at 80% capacity and above.  As the battery deteriorates and approaches 80% capacity the correlation between capacity and conductance increases providing visibility to the approach of the end of the service life of the battery."

"When the battery is at EOL or 80% of rating (20% reduction) the conductance will be approximately 50% of initial value (50% reduction)."

(So) "As remaining battery life decreases, so does the conductance".
  

They then display a correlation chart showing good tracking (.9316) of conductance and capacity.

(So my challenge is figure out or find a circuit or two or three...to try out and then determine how to apply this technology to in-place and installed battery packs).

All helpful inputs are appreciated.

Ray, W4BYG



Raymond LaRue
Director, Broadcast Engineering
Skyangel US, LLC
4922 LaCollina Way
Ooltewah, TN 37363
423.396.8131 Ofc
423.310.5446 Cell
 
www.skyangel.com
 
"It is better to be divided by truth, than to be united in error"...  Adrian Rogers


-----Original Message-----
From: rbethman [mailto:rbethman at comcast.net] 
Sent: Wednesday, March 16, 2011 1:04 PM
To: Discussion of Electronic Test Equipment
Cc: jfor at quik.com; Raymond LaRue
Subject: Re: [Test-Equipment] "Conductance" battery checker

When you obtain a "cell", i.e., AA, AAA, C, or D, you have a "specified" 
voltage and maH charge.

Conductance is the *ability* to allow the flow of current at specified voltage.  Therefore, you "must" know the internal resistance to determine this.

Determination of the *remaining* charge, requires test "under load".

These are entirely *DIFFERENT* measurements, and provide different
*characteristics* of THE cell under test.

Bob - N0DGN

On 3/16/2011 12:44 PM, J. Forster wrote:
> The "reference" could be either charge or internal resistance. I'm 
> inclined to think the latter. Conductance is the inverse of Resistance.
>
> Think of it as like the ESR of a capacitor.
>
> -John
>
> ============
>
>
>> Bob,
>> Thanks for the response.
>>
>> You may be right, but the information on the Midtronics Power Secure 
>> 6/12 seems to indicate a "percentage" of charge remaining.
>>
>> I had one here from the local Interstate Batteries office last week.  
>> It displayed xx% of "reference".  The "reference" (therefore I assume 
>> full charge), is developed by testing several good batteries first.
>>
>> How they obtain and interpolate that is one of the major questions I have.
>> Ray
>>
>>
>>
>> -----Original Message-----
>> From: rbethman [mailto:rbethman at comcast.net]
>> Sent: Wednesday, March 16, 2011 12:25 PM
>> To: Discussion of Electronic Test Equipment
>> Cc: Raymond LaRue; jfor at quik.com
>> Subject: Re: [Test-Equipment] "Conductance" battery checker
>>
>> "Normally" battery conductance is a measurement of the battery's 
>> internal resistance.  NOT the remaining charge.
>>
>> Bob - N0DGN
>>
>> On 3/16/2011 12:06 PM, Raymond LaRue wrote:
>>> I believe the amount of "charge" left in the battery, is what is 
>>> measured.
>>>
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: test-equipment-bounces at mailman.qth.net
>>> [mailto:test-equipment-bounces at mailman.qth.net] On Behalf Of J.
>>> Forster
>>> Sent: Wednesday, March 16, 2011 11:52 AM
>>> To: Discussion of Electronic Test Equipment
>>> Subject: Re: [Test-Equipment] "Conductance" battery checker
>>>
>>> Do you mean they measure:
>>>
>>> The amount of charge left in a battery (A-H)?
>>> or
>>> The internal resistance of a battery?
>>>
>>> -John
>>>
>>>
>>>
>>>> Looking for information on designing and building a battery 
>>>> "conductance" tester.  In an extended web search, I see a couple 
>>>> companies that sell small 6 and 12 volt conductance testers.
>>>>
>>>> They apparently inject a small AC voltage into a battery on or off 
>>>> line, in a non-intrusive way.  Calibration data is developed by 
>>>> profiles from testing good batteries.  The resultant voltage and 
>>>> current phase differentials are processed and utilized to give an 
>>>> indication of remaining battery capacity.
>>>>
>>>> The commercial testers available are not very expensive, but those 
>>>> found on line give little detail about how they operate and they 
>>>> appear not to quite meet my needs, as I would like to try this 
>>>> technique by composite testing of a series of SLA batteries.
>>>>
>>>> I am prone to try building one if helpful info were available.
>>>>
>>>> Does anyone have any experience with such, or have design info for 
>>>> building a battery conductance tester?
>>>>
>>>> Thank you for your attention.
>>>> 73,
>>>> Ray, W4BYG
>>>> Cleveland, TN
>>>>
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+------------------------------------------------------------------+
|               AM Amateur Radio Operator    NØDGN                 |
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| Bob Bethman                \\\|///     " The absence of a danger |
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