[Test-Equipment] "Conductance" battery checker

J. Forster jfor at quik.com
Wed Mar 16 13:45:22 EDT 2011 

As I said, what you are suggesting is an ESR test on batteries. The ESR is
essentially the resistance in a Thevenin Equivalent for the battery.

Charge is in A-H  ( current * time = Charge [Coulombs])
1 A = 1 Coul/Sec.

Conductance is inverse Resistance;  Conductance = 1/ (Resistance)

-John

=================


> 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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>>
>>
>
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> |               http://home.comcast.net/~rbethman/                 |
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> | Bob Bethman                \\\|///     " The absence of a danger |
> |                           \\ ~ ~ //      signal does *NOT* mean  |
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