How to tell if a SLA Battery is beyond repair

Discussion in 'General Electronics Chat' started by Gdrumm, Dec 27, 2011.

  1. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    I frequently come across old UPS and other devices that use SLA batteries, normally 12v.

    I've been able to salvage some of them by filling them with distilled water, but some times it doesn't work.

    Is there a quick way to tell if they are salvagable or not?

    For example, when I remove the small rubber caps and look inside, if I see rust, does that mean the battery is unsalvagable?

    Conversly, if it looks clean inside, with white cloth looking material and a lead colored metal sandwiched between, is that a good one?

  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    I dunno about filling them when they say maintenance free...

    I throw em if they seem to be bulging...

    And oh more thing, try googling De-Sulphating lead acids.
    It might help.

    If VDC is 0V u can tell it won't come back to the world of living.
    But hey if you can fill 'em up and charge and use it like for 2 days, who am I to argue.
  3. strantor

    AAC Fanatic!

    Oct 3, 2010
    if you try to charge them and the draw milliamps instead of amps, then no good.
  4. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    and u wonder why they even try it ?

    Sigh !~!!!!
  5. Smoke_Maker

    Active Member

    Sep 24, 2007
    Like R!f@@ said if swelling isn't good.

    If the build date is over 5 or 6 years old you chances are not good, save the newest ones.

    In a 12 volt lead acid battery the difference between full charge and empty is 0.6 volts. If the battery is closer to 12.0 volts than 12.6 volts put a charger on it and see if it will take 10 to 20 amps, if it dose you might have a good one.

    If the battery is close to full 12.6 volts put a 25 amp load on it and see how low it drops, if it go's below 10.5 volts recycle it.

    The only way to do this correctly is to build a battery cycler, I have a schematic around here somewhere if your interested. The cycler charges the battery then discharges it, and times the discharge so you can tell how many Ah the battery can hold.
    PackratKing likes this.
  6. Audioguru


    Dec 20, 2007
    My car battery was 4.5 years old when a mechanic tested it and said it must be replaced. He gave me a printed graph by the test machine to prove it showing its capacity and max current are less than half a new battery.

    That was last year. It has started my car fine for one more year and now in winter it gets very cold but it still works. It has never been over-discharged because the lights automatically turn off and it has never not started.
  7. Smoke_Maker

    Active Member

    Sep 24, 2007
    I have found this to be very true, they have tryed to take the brain work out of battery testing, it's easer and cheaper to build a tester to "guess" the condition of the battery than it is to teach mechanics how to test them correctly, I long for the old carbon pile days.