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  • Desulfating of batteries

    Can someone shed me some light on desulfation.. I have a herd of lead-calcium batteries here with issues, perhaps I can revive them? Maybe desulfating is only good to make good batteries last longer?

  • #2
    Sulphation is hard crystal growth stuck to the cell plates, blocking access to the electrolyte. There are some products that claim to use high frequency electrical pulses to either knock the crystals loose, or dissolve them back into the electrolyte. But for all the hype about them, it's not really known if they work. Reports seem to indicate they sometimes work, for some folks. If it's cheap, I'd try it.
    Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister

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    • #3
      Desulfating lead acid batteries

      Some new chargers have the "battery conditioning" setting which desulfates and some charge controllers have a desulfating pulse setting. The most common is adjusting the charger on inverter/chargers to desulfate and using a generator to over-charge for a period to boil off the sulfate crystals and return them to acid solution. My tow trace charge controllers have a button, pressed for 15 seconds, which switches to a red flashing light and goes to over-charge for a period of several hours. On the 12VDC banks the normal charge is at 13.4 VDC for an hour or so to fill, and 15VDC for desulfating once a month.
      The DR2424 Inverter/charger has an adjustable setting for desulfating at 30 VDC for a half hour or so a month, but they regulate to a 29.2 and pulse up and down a volt when full, which keeps sulfating to a minimum. Other charge controllers do it automatically once a month. It is all in the specs and manuals.

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      • #4
        Originally posted by Johnny Electriglide View Post
        Some new chargers have the "battery conditioning" setting which desulfates and some charge controllers have a desulfating pulse setting. The most common is adjusting the charger on inverter/chargers to desulfate and using a generator to over-charge for a period to boil off the sulfate crystals and return them to acid solution. My tow trace charge controllers have a button, pressed for 15 seconds, which switches to a red flashing light and goes to over-charge for a period of several hours. On the 12VDC banks the normal charge is at 13.4 VDC for an hour or so to fill, and 15VDC for desulfating once a month.
        The DR2424 Inverter/charger has an adjustable setting for desulfating at 30 VDC for a half hour or so a month, but they regulate to a 29.2 and pulse up and down a volt when full, which keeps sulfating to a minimum. Other charge controllers do it automatically once a month. It is all in the specs and manuals.
        I think you are speaking of the EQUALIZATION stage of charging, and not desulphating. Flooded batteries need a monthly EQ cycle. Desulphating uses low current, and magical frequencies to remove the sulphate crystals. Most desulphaters, you have to remove the loads from the batteries, as the wiring absorbs and dissipates the high frequency pulses.
        Desulphate is not the same as Equalization Charging.

        When batteries are below 75% of full, the sulphate crystals start to form, and are difficult to remove.
        Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
        || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
        || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

        solar: http://tinyurl.com/LMR-Solar
        gen: http://tinyurl.com/LMR-Lister

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        • #5
          Equalization desulfating action

          The equalization also desulfates, unless the deposits are really stuck on from continued over-draw of the batteries. The pulse desufators are more effective in removing that thick of lead sulfate crystals.
          The heating up of the electrolyte by equalization charging helps dissolve light formation of lead sulfate, along with the gassing action which appears to be boiling. Battery level should be checked before equalization, so that the lead sulfate can return to sulfuric acid solution. Length of time depends on temperature.
          The thing to do is keep the battery bank discharge, as much as possible, to 20% and not 50%, and to never let the fluid get too low, and equalize/ mild desulfate once a month. A friend has had his l-16s last over 25 years this way.
          My original system used the old 350Ah L-16s, and before I had my other system. It was used to 50% often, and not equalized much, plus the fluid level allowed to drop too far. The entire two banks were replaced at their advertised 8 year life. The 410Ah L16S batteries are equalized at intervals, kept up on fluid, and rarely drawn down past 20%.
          In my garage system, I tried a new hi-tech pulse desulfator charge controller that was supposed to bring in more power(and didn't!). I sent it back and got a Xantrec C35 instead(from having an overheating 30 amp before, with push tabs for adjusting voltage). I increased the battery bank size to 4-L16S from 6-golf cart 220 Ah batteries, then used the best 4 golf cart batteries out in the Earthship to double the bank size out there, and changed to a Xantrec C12. The C12 and C35 both have the buttons for easy monthly equalization/mild desulfating.
          I do have a 10/20/40/100 amp 12VDC charger with battery recondition mode. It has been unnecessary, and over sulfation has ceased to be a problem because of over-sizing the banks and monthly overcharge to equalize cells and redissolve the light lead sulfate film.
          If you let the lead sulfate become more than just a film, then the pulse battery reconditioner has to run for a whole 8 hour day. If it is thicker than about 1/16", it is too late and the battery is just a trade in core. In my experience.
          Last edited by Johnny Electriglide; 07-16-2009, 04:04 PM.

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          • #6
            Originally posted by Johnny Electriglide View Post
            The thing to do is keep the battery bank discharge, as much as possible, to 20% and not 50%, and to never let the fluid get too low, and equalize/ mild desulfate once a month.
            I think you meant charged.
            Ken
            Telford,Pa
            Homepage: [url]http://home.comcast.net/~n3qik[/url]
            [B]Updated 6-7-2009[/B]

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            • #7
              We have an equalization setting on our inverter and this works wonderfully as a desulphator as Johnny attests. The pulsators don't do much of anything. But a generator cranking up the volts, heat, and molecular vibration knocks that sulphate off quicker and better than anything.
              [URL="http://www.spheralsolar.com/"]Solar Panels for Homes[/URL]

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              • #8
                I built a desulphator from a circuit I found on the web. I let it run for about 2 weeks on a partially dead motorcycle battery. My oscilloscope showed the circuit was pinging the battery pretty hard with fairly high freq pulses. Results were inconclusive... maybe I didn't leave it on for long enough.

                But when I read Johnny Electriglide's comment about returning the sulphur to the acid solution, something occured to me. If a battery is sulphated, that sulphur on the plate left the acid and the acid was weaker. H2SO4 minus the S leaves hydrogen and oxygen which happily form water. If you then go and attempt an equalization charge, you will boil some of that water out. If you replace that water with water, you are okay. But you might be tempted, myself included, to replace that water with new acid in an attempt to revive the battery. If you do that, then you won't be able to remove the sulphur from the plates and get it to go back into the acid because the acid is already acid and not water waiting for sulphur. Did that make sense?

                Oh well, just a thought.

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