Is "surface charge" the proper term?

Discussion in 'General Electronics Chat' started by #12, Jan 19, 2016.

  1. #12

    Thread Starter Expert

    Nov 30, 2010
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    A recent post contained the phrase, "surface charge" (on a car battery). I instinctively understood this term when I first heard it, but I don't know if it is a, "shade tree mechanic" term, or is it proper usage among the well educated (EE's)?
     
  2. Lestraveled

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    May 19, 2014
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    It is a valid term used in the battery industry. It is used to describe the voltage of an unloaded battery just after being charged, that is deceptively high. A batteries state is often determined by the "resting" voltage, which is the unloaded battery voltage after it has been loaded.
     
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  3. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    I think it would be considered "gas recombination". A charging of a battery that is overcharging because there is no additional lead sulfate .


    Gas recombination deals with electolysis of water (hydrogen and oxygen) and the oxygen (or lead oxide) playing a role in the subsequent lead acid electrochemical reaction. There are sealed batteries that take advantage of this reaction but I don't know the details ( if it is for durability or efficiency, or other).
     
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  4. #12

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    I don't think, "gas recombination" is going to result in effective communication, but if that's what Engineers call it, I'll just have to use the wrong term at the local car repair shop.:(
     
  5. GopherT

    AAC Fanatic!

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    Correction, scientists/chemists call it gas recombination (what happens). The engineers have their own language - and may well call it surface charge (what is observed).
     
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  6. Lestraveled

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    May 19, 2014
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    This is from a USA Battery website:
    Surface charge is the uneven mixture of sulfuric acid and water within the surface of the plates as a result of charging or discharging. It will make a weak battery appear good or a good battery appear bad. You need to eliminate the surface charge by one of the following methods:

    3.1. Allow the battery to sit for four to twelve hours to allow for the surface charge to dissipate.

    3.2. Apply a load that is 33% of the ampere-hour capacity for five minutes and wait five to ten minutes.

    3.3. With a battery load tester, apply a load of at least one half the battery's CCA rating for 15 seconds and wait five to ten minutes.
     
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