12 Volt Lead Acid Battery Desulfator - New

Discussion in 'General Electronics Chat' started by Edenhope, Jan 1, 2016.

  1. Edenhope

    Thread Starter New Member

    Dec 13, 2015
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    0
    Can I use your desulfator, Lestraveled, on this thread to charge a single cell by using a separate power supply for the bit that pulses the MOSFET?
    I have a single sulfated cell in a 500Ah off-grid battery and urgently need to revive it.
    I've got the parts and have started building but realised it might not do what I need.

    Mod note:
    Please do not add to very old threads. Now you have your own new one.
    Old thread is here for reference if you need it.
     
    Last edited by a moderator: Jan 1, 2016
  2. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    The brute force method I occasionally use isn't allowed on this forum, because it uses a transformerless mains supply. But if a battery is that far gone, its only a stop gap measure to get me to the shop for a new battery.

    Yuasa published various pamphlets on battery care and maintenance, at least one had sample schematics in the back pages - these should still be on their website, there are a few random older editions floating about the net.

    Generally speaking; if you can't recover a 12V battery with 30V, it will never fully recover anyway - you have to use a current limited supply to avoid damage if/when the battery starts taking charge current. Yuasa suggest 1/3 of the Ah capacity rating.

    If you want to automate it; a voltage comparator should detect when the recovering charge current pulls the constant current down to 10.8V - then the charger should switch to constant voltage.

    A quick and dirty method I often use is a very old iron core transformer battery charger with a couple of 2.2uF capacitors across the bridge rectifier to make it a voltage doubler.

    The only part of my charger that's original is the metal case. The transformer is from a Philips black & white portable TV (requires a current limiting resistor). The rectifier came from a motorcycle and the moving iron current meter was replaced by a bulkhead mounting Admiralty instrument.

    The unloaded voltage is nearly 50V, so I can be reasonably confident, if a battery doesn't recover on that - its not worth any further effort.

    I also added a big fat electrolytic on the output so I can use it to blat whiskered nickel cells.
     
  3. recklessrog

    Member

    May 23, 2013
    338
    102
    Despite all the claims about different designs for electronic "de-sulphators" and in no way am I suggesting that they do not work, I have recovered/extended the life of many lead acid accumulators with a product called "BATAID" These are tablets that dissolve in the electrolyte and really do "restore" worn out, tired, and even dead cells. They work by neutralising the sulphate. The cost is so small compared to buying the required parts to build a restorer.
     
  4. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
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    My experience with Bataid has been somewhat different, but then some of the batteries I tried to revive were pretty far gone.

    Generally, I've been disinclined to risk putting them in a battery I could recover any other way.
     
  5. recklessrog

    Member

    May 23, 2013
    338
    102
    I think that if all else fails, there is not much to lose. Two winters ago, the battery on my car was failing to hold sufficient charge for more than a couple of days so I put two BatAid tablets in each cell and gave it a good trickle charge. Two years on and it's still going strong. win some, lose some I guess.
     
  6. Lestraveled

    Well-Known Member

    May 19, 2014
    1,957
    1,215
    A voltage doubler desulfator would not work well for a single cell 500 AH battery. This cell would have an extremely low internal resistance and a 500 AH cell requires a lot of pulse current for desulfation to be effective. This is beyond the capability of a voltage doubler. Look up the "Direct Drive" thread on the Lead Acid Battery Desulfator Forum. This is the one you should use.
     
  7. Edenhope

    Thread Starter New Member

    Dec 13, 2015
    2
    0
    Thanks. I've seen your Direct Drive desulfator postings and will give it a go.
     
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