[Test-Equipment] "Conductance" battery checker

[rbethman]

You've got it John!

All this little "conductance" tester is performing an ESR test, using AC.

Personally, I'd rather have a "load tester" to tell me what the 
remaining charge is.  I've been doing that since 1989 or so.  Primarily 
in the use of NiCads in the use of R/C flying.  I'd like to ensure the 
NEXT flight will have adequate charge to make a complete and successful 
flight.

Losing control of 25 to 40 pounds moving around 90 to 100 MPH is HIGHLY 
undesirable!

If my flashlight starts to loose capacity, I can usually tell by the 
loss of light intensity.  Its use IS a load test.  I simply change the 
batteries.

Bob - N0DGN

On 3/16/2011 1:45 PM, J. Forster wrote:
> 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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>>>> |               AM Amateur Radio Operator    NØDGN                 |
>>>> +------------------------------------------------------------------+
>>>> |               http://home.comcast.net/~rbethman/                 |
>>>> +------------------------------------------------------------------+
>>>> | Bob Bethman                \\\|///     " The absence of a danger |
>>>> |                           \\ ~ ~ //      signal does *NOT* mean  |
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>>>>
>>>>
>>>
>> --
>> +------------------------------------------------------------------+
>> |               AM Amateur Radio Operator    NØDGN                 |
>> +------------------------------------------------------------------+
>> |               http://home.comcast.net/~rbethman/                 |
>> +------------------------------------------------------------------+
>> | Bob Bethman                \\\|///     " The absence of a danger |
>> |                           \\ ~ ~ //      signal does *NOT* mean  |
>> | rbethman at comcast.net      (/ @ @ /)      that everything is OK " |
>> +----------------------o00o---°(_)°---o00o-------------------------+
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>
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+------------------------------------------------------------------+
|               AM Amateur Radio Operator    NØDGN                 |
+------------------------------------------------------------------+
|               http://home.comcast.net/~rbethman/                 |
+------------------------------------------------------------------+
| Bob Bethman                \\\|///     " The absence of a danger |
|                           \\ ~ ~ //      signal does *NOT* mean  |
| rbethman at comcast.net      (/ @ @ /)      that everything is OK " |
+----------------------o00o---°(_)°---o00o-------------------------+