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Cause of corrosion/salts on battery terminal? Battery charger modules?

Discussion in 'Misc Electronics' started by Dave Baker, May 5, 2005.

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  1. Dave Baker

    Dave Baker Guest

    Does anyone know what would cause corrosion at the negative battery terminal
    of a 7 amp/hour sealed lead acid battery?

    There is a picture at
    http://www.jodael.com/images/Corrosion.jpg
    showing the damage.

    This unit is in a protected place - maybe too protected as the box may be
    getting too hot.

    Is this caused by overcharging?

    On a related note, I'm looking for some sort of modular battery charger that
    can charge these batteries. It should be able to take 24V DC input, and
    output whatever is needed to trickle charge the above battery. Anyone have
    any sources for this kind of product? I'm going to need at least 10 of them.
    Ideally they will be quite small (matchbox size or smaller) and rugged.

    Dave

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    All replies to the group please.
     
  2. CWatters

    CWatters Guest

    No I believe it's caused by damp. I read somewhere that it's an electrolytic
    effect that produces acid and/or white lead oxide. Prevention usually
    involves covering the exposed terminal/wire with a layer of thick grease
    after connecting the leads.

    Disconnect the lead and clean the terminal and contacts with a wire brush
    or file to remove any oxide, replace connection, tighten, test battery and
    then smear on some grease.
     
  3. Dave Baker

    Dave Baker Guest

    Well, the equipment is on a boat (although on an air-conditioned bridge of
    that boat, and in an IP67 box with goretex gland), but:

    a) It's a sealed lead-acid battery so acid shouldn't be able to get out.
    Maybe not a good quality one?

    b) The terminals on these small batteries (same as in UPS units or PABX
    units) aren't lead I don't think. And I'm just using normal spade connectors.

    Dave

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  4. Michael

    Michael Guest


    SLAs that leak aren't unknown (which is not to say that yours definitely leak).
    Yours do live in a humid environment though; bare terminals is asking for
    trouble. I would carefully clean all connectors with fine abrasive (and a base
    solution, just in case), dry everything, reassemble, smear on Vaseline.
     
  5. CWatters

    CWatters Guest

    We've also seen this problem with NiCad cells used in model aircraft where
    it's known as the "black wire blues" because it frequently effects the
    negative lead but leaves the positive like new.
     
  6. Guest

    You asked:

    "Does anyone know what would cause corrosion at the negative battery
    terminal
    of a 7 amp/hour sealed lead acid battery?"

    It's often caused by the fumes being vented from the battery during
    charging. These consist of hydrogen and sulfate/sulfite compounds.
    Since the hydrogen is normally attracted to the negative terminal and
    the sulfate/sulfite (being negatively charged ions) to the positive
    terminal, your description of the problems is somewhat of an enigma so
    I would rule out this as a cause.

    On the other hand, if you are in a very wet or damp environment, you
    could have what is essentially electroplating taking place with metalic
    ions migrating from the positive terminal to the negative terminal.
    This is rather unusual, but in a salt air marine environment is
    entirely plausable.

    The solution to either cause is the same. Clean the connections and
    coat them with a heavy layer of ordinary grease. Ain't pretty, but it
    works.

    Harry Conover
     
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