Desulphators - Legit or Not?

Discussion in 'General Electronics Chat' started by tracecom, Apr 28, 2010.

  1. tracecom

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  2. retched

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    Yes, they work. But you have to realize:

    It takes a long time to sulfate plates. It takes a long time to desulfate them, too.

    This does work, and if you need to see something while its working, measure the specific gravity of the electrolyte every week. You will see it change with nothing more than the desulfinator attached.

    I have not used the one that you have, but it uses a technique that does work.
     
  3. tracecom

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    Right now, the only battery I have to use it on is a 17Ah gel cell. Should I try it on that? Some things I have read say that only wet cells can be reclaimed? (The gel cell measures 0 volts.)
     
  4. retched

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    0v...WOW.. thats awful low.

    Id give it a whirl. Gel cells can suffer sulfation, and can benefit from desulfination.
     
  5. SgtWookie

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    The first thing I noticed about the schematic in the PDF that you linked to has the MOSFET shown connected upside-down; the source and drain terminals are swapped. Had you connected it that way in the real circuit, the body diode of the MOSFET would have full battery voltage across it; and the fuse would immediately be blown.

    If your gel cell won't charge past 7v, you won't be able to use the desulpator on it, as the MOSFET won't get turned on enough.

    It is possible to use a trickle charger with this desulphator, if you connect the negative lead of the charger to the junction of L1/L2/C4/C5, and the positive lead to the positive rail (the wire running across the top of the schematic).

    This desulphator is nearly identical to the original Alastair Couper design that was published years ago.

    I've built a few N-channel MOSFET versions of that design with modifications. They do work on batteries that are sulphated, but it takes quite a while for the process to finish.

    The most reliable means of tracking progress is to observe your cell specific gravity readings. Those that are heavily sulphated will have a very low specific gravity. Over time, you should see the specific gravity readings increase so that they are nearly identical from cell to cell; providing that you maintain the electrolyte level properly, and ensure that the battery remains charged.

    Lead-acid batteries will last a good bit longer if they are occasionally charged to the point of gassing for a short period. This helps to remove sulphation, and stirs up the electrolyte without subjecting the battery to physical abuse.

    Don't put a high charge on a gel-cell battery, as when these types are subjected to rapid or over-charging, bubbles form in the gel, which permanently reduces their capacity. Divide their AH rating by 5, and charge them at that rate or less. For example, a 12AH gel cell should be charged at a maximum of 2.4 Amperes until it reaches around 14v.
     
  6. jpanhalt

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    I remain highly skeptical. Once the stable form of lead sulfate is formed to disrupt the function of a battery, it is not going to be converted back to lead and lead(IV)oxide and deposited back onto the plates as they were initially.

    I would like to see the current and specific gravity data obtained during desulfation of a dead, fully sulfated cell as described by the OP here. SgtWookie takes a more reasonable view, at least to me, of the role of desulfation and over-charging/gassing cells to prolong life, but not to resurrect a completely dead cell.

    John
     
  7. eblc1388

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    Nov 28, 2008
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    Agree to what jpanhalt has commented.

    Dead cell usually charged up to float charge voltage within seconds and does not take any significant charging current. Once the charging voltage is removed and load applied, the cell voltage will drop below 12V within minutes or seconds.

    Anyone has successful story in resurrection of cells in this condition?
     
  8. SgtWookie

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    Awhile back, I used a commercially available desulphator on a lawnmower battery. Three cells had specific gravity readings less than 1.1, and it did not have enough power to start the mower. It took nearly a month, but all of the cells were restored to a specific gravity of ~= 1.26.

    I also used it on a couple of large military-type 6TMF batteries that had been in storage for a couple of years. It took quite a while, but they did show definite improvement, and are currently in use.
     
  9. t06afre

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    Desulfation is not done overnight. It take weeks. I think many people forget that fact. So the get disappointed by the results
     
  10. SgtWookie

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    It took nearly a month to restore a SMALL lead-acid battery. The lawnmower battery is about the size of a motorcycle battery.

    Patience is a virtue that takes time to nurture. ;)

    If you want faster results, then use a high-output battery charger (say, 20A or more) and charge the battery up to the point of gassing, and let it gas for 20-30 minutes or so once every 24 hours.

    Watch the battery internal temp closely; it can be measured by the + terminal. A temp rise of 30°F will cut the battery life by 2/3 due to the increased chemical activity. If the cells are not gassing evenly (one cell is gassing much more than the others) it may be shorted internally. If a cell is shorted, there is not much you can do for it except recycle the battery.
     
  11. tracecom

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    I drug out one the batteries; it's a Portalac PE12V17 and is one of four that I have. It is identified as a sealed lead acid battery, so I don't really know if it is a gel cell or not. The voltage on this one measures 6.8v with no load.

    The battery charger that I have has four settings: 6v, 10a fast charge; 12v, 2a float charge, 12v, 10a fast charge, and 12v, 55a start. When I set it to anything other than 12v, 55a start and try to measure the no load voltage, the output is zero. (I assume that it has a sensor that is shutting it off if there is no load?) On the 12v, 55a start position, it measures about 15.5 v with no load.

    So, I set it to 12v, 2a float, connected it to the battery, and then measured the voltage; it is 11.5v. However the ammeter on the charger seems to be at zero current.

    All this is without even connecting the desulphator. Is the battery potentially salvageable or not? What should my steps be? Leave it on the charger a while and see if the no load voltage goes up? Attach the desulphator now? Or what?

    Thanks for the help.
     
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