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(old) batteries hitting a charging wall?

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  • (old) batteries hitting a charging wall?

    hi all...

    was wondering if this was normal, am having a problem with my charging batteries reaching a certain voltage and then not increasing any further, unfortunatly this is below 12v usually...

    i know i should be testing on new batteries, but only have acces to old batteries at the moment

    any feedback appreaciated, especially any guidelines on reconditioning old batteries, eg how many charges needed? and if resting voltage is still below 12v should another charge cycle be done straight away or discharge first?

    thanks in advance =)
    matt b

  • #2

    If your battery voltage is below 12v then something is not right. Your post is a bit vague - this is during charging or discharging? If charging, your battery has a bright future as a paperweight. If discharging, you are discharging too far(too low a voltage).
    There are ways to bring back some dead/worn out batteries, but I believe that is beyond the scope of this beginner SSG forum.
    I got two new 7AH batteries from NAPA for about $35.00 each.



    • #3
      A 12V battery consists of 6 cells (each around 2.1V) in series. If the battery has any internally-shorted cells, that limits the voltage it can achieve on charging. The shorted cell will always discharge. So for example if a 12V battery rests at around 10.5V, no matter what you do, you can be pretty sure that it has one shorted cell. If it rests at around 8V then 2 shorted cells, etc.

      Some people have reported protocols to disassemble the battery and drain out the crud. I personally have never done this and don't have a place or equipment where it could be attempted safely. (All that acid, lead compounds, etc.)

      If a battery has internal shorts, chances are that the plates are quite damaged, so even if you could remove the short by cleaning out the electrolyte well and starting over with strained electrolyte, the battery is still probably going to fail pretty soon. The plates get metal fatigue from heating and cooling, and can simply crumble. The first shorted cell is your early warning that the plates are warped or crumbling. From there, it is unlikely things will ever get better.

      These experiments are a lot more fun and more productive if you start with good batteries and treat them kindly.



      • #4

        I agree with your reports of people cleaning out these batteries. I've heard about it, but never done it. I've heard that the space between the bottom of the cell and the plates is not very high in automobile batteries. As the battery ages, junk and crud falls off the cells and collects in this shallow space. The buildup actually touches across the individual plates, thus shorting them out. Higher quality deep-cycle batteries have a larger space below the plates so this does not happen nearly as quickly. So yes, draining them can flush this out and perhaps make the battery useable again.
        I've had problems understanding why batteries short out, but this explanation has made it clear to me. I'm sure more can go wrong inside a battery.
        You seem very knowledgeable on just about every topic discussed on this forum. I just wanted to share, hopefully with others also, a bit of information that has made this easier for me to understand.



        • #5
          Hi and thankyou for your replys, (sorry for vague post)

          have plans to get some new batterys, was just keen to start experimenting with what i had available

          Sorry to repeat what has been said, but just to be clear -if a battery is not respondinding after a charge cycle or two and returning to a resting voltage above 12v, then it most likely has a shorted cell(or two) and is not likely to recover without a rebuild(which may not be worthwhile)?

          would a shorted cell drain any charge that had been replaced in the good cells?

          Thanks again
          Matt b


          • #6
            Hi Matt,

            I agree get the new batts... I also wasted countless hrs. if not days trying to get some life out of an otherwise a bad set of batteries. Frustrating effort, especially when getting started with these motors. Its easier to work with new batts and use that time elsewhere.

            Surprisingly later on i was able to get my HD AGM's revived; Took JK's advice; drilled out the top plate holes and re-hydrated the cells. Ran them through the rejuvenator charger and voila out of 32 batteries only one was bad, and that was more my fault... When drilling the top plate i ran my drill into the cells, scrapping the battery the batteries were ranging anywhere from 4-7 years old and their next stop was the scrap heap, or the more politically correct "recycle center"...

            btw i did keep the dead batt and sawed it in half, was curious to see the insides. All the plates were sandwiched, with some sort of fiber in-between. separate the fiber from the plate and it falls apart in checker-board fashion leaving only a grill mesh where the plates would normally be. I wonder how an Alum mix would work in an AGM battery?

            anyhow, thought i would share my experience with AGM's. Good Luck on your testing!