Blast Your Battery’s Sulphates, Is It Worth It?

When a friend finds her caravan’s deep-cycle battery manager has expired over the summer, and her holiday home on wheels is without its lighting and water pump, what can you do? Faced with a dead battery with a low terminal voltage in your workshop, check its electrolyte level, hook it up to a constant current supply set at a few hundred mA, and leave it for a few days to slowly bring it up before giving it a proper charge. It probably won’t help her much beyond the outing immediately in hand, but it’s better than nothing.

A lot of us will own a lead-acid battery in our cars without ever giving it much thought. The alternator keeps it topped up, and every few years it needs replacing. Just another consumable, like tyres or brake pads. But there’s a bit more to these cells than that, and a bit of care and reading around the subject can both extend their lives in use and help bring back some of them after they have to all intents and purposes expired.

One problem in particular is sulphation of the lead plates, the build-up of insoluble lead sulphate on them which increases the internal resistance and efficiency of the cell to the point at which it becomes unusable. The sulphate can be removed with a high voltage, but at the expense of a dangerous time with a boiling battery spewing sulphuric acid and lead salts. The solution therefore proposed is to pulse it with higher voltage spikes over and above charging at its healthy voltage, thus providing the extra kick required to shift the sulphation build up without boiling the electrolyte.

If you read around the web, there are numerous miracle cures for lead-acid batteries to be found. Some suggest adding epsom salts, others alum, and there are even people who talk about reversing the charge polarity for a while (but not in a Star Trek sense, sadly). You can even buy commercial products, little tablets that you drop in the top of each cell. The problem is, they all have the air of those YouTube videos promising miracle free energy from magnets about them, long on promise and short on credible demonstrations. Our skeptic radar pings when people bring resonances into discussions like these.

So so these pulse desulphators work? Have you built one, and did it bring back your battery from the dead? Or are they snake oil? We’ve featured one before here, but sadly the web link it points to is now only available via the Wayback Machine.

55 thoughts on “Blast Your Battery’s Sulphates, Is It Worth It?

    1. Yes, came on here to say this. I’ve had experience with Da Pimp, I own one, have used it on many batteries. Not all come back to life of course, and the length you get is variable. But, it has easily paid for itself in extending batteries. Also, with UPS and emergency lighting batteries getting recycled all the time, your local e-waste center is a gold mine when you’ve got da pimp in yo pocket…

  1. I am interested in this topic, so commenting. My initial response is that a ‘desulphater’ should be a commercial proposition; I already use a trickle charger on boat and RV batteries, and a desulphater would be a possible annual treatment.

    1. There was a commercial desulphater available in Germany. It simply connected permanently across the terminals. When the battery was charging a charge pump supplied the voltage spikes from the charging current.

    1. Depends, if your battery failed due to misuse, than you win. If your battery failed within warranty by normal use then it’s pretty shitty battery and you should consider your battery choice.

    2. I bought a cheap battery with a three year warranty. Two years into it it failed. I took it back and they prorated it so i got a few bucks toward a new battery. After two years that one failed. Next time I went to Sears and had a Diehard battery installed. It cost 3 times as much as the cheap battery. When I got rid of the car I was going through the old receipts and I realize that the Diehard had been in my car for 12 years and it was still fine. Lesson learned: don’t buy cheap batteries.

  2. My boss showed me a trick many moons ago, for SLAs that have been dead and uncharged for years: Remove the top cover, remove the butt plugs, top up the cells with distilled water, set your lab PSU to 60v @ 500mA constant current, let the battery charge until it self-limits the voltage down to ~24.0v, drop the voltage down to 14.4v and leave it overnight. Works like a treat almost every time.

    1. Short answer, no.

      Did that for a few time. It just prolongs the agony.
      It might work, but not always, and not for long, and do not expect a full recover.
      Sooner or later, the faulty battery needs to be replaced with a new one no matter what.

  3. Been doing this for years on motorcycle batteries two ways. One by pulsing with a fast charger for car batteries. It works but results are variable, never results in full rejuvenation, good in a pinch though. A little bit better results are obtained by modding a slow charger to put out a higher maximum voltage and let the battery soak at a trickle to de-sulfate, but it’s still not resulting in a reliable battery. Same results with sealed lead-acid but the cost is higher. Have found best $$$ value is still with wet cell lead acid.

  4. When they went to car batteries without removable caps that required maintenance and checking, they gave us a different chemistry that has a poor life and dies easily. Do not let one of those so called maintenance free batteries run down. Maintenance consists of replacing it. I was hip to this desulphating 40 years ago from a grade school friend who started a major local business then in repairing the DC world that sits on 4 or more wheels. I think it is more suited to these old school cells than the newer stuff.

    SLA’s are right up there with the symbionese liberation army, a flash in the pan. Butt plugs, ugh. I thought sealed meant… Millions of UPS’s go to the toilet in 3 years even though they’re on 99.9999 percent grid electricity. If you have business IT you have UPS’s, oh do they collect as boat anchors.

    1. yes they are boat anchors and if you play your card right you can make a few bucks. Locally there is a shop that pays right now about 75cents per ups battery working or dead he does not care. So i take them literally by the truckloads off clients. the batteries go to him and i get some cash the metal gets me a little cash normally not much and the other local recyclers takes all the pcb boards. Yeah a days work but at least it is not going into a land fill

      oh and a plus if there appears to be any neat/fun/interesting/needed parts in the guts I keep that.

    2. yeah those unvented cells are god awful, after about 2 years at least one cell will be horribly swollen up.

      good news for me though, is the other cells are usually fine. client pays to replace the whole unit, I take the junker, and strip a bunch of gell cell packs out of it for hacking!

  5. All I’m going to say is, forget any ideas you have about prolonging the life of a vehicle battery,
    as the cranking voltage falls so the current and cranking time increases thus damaging the starter motor eventually, starter motors tend to cost way more than batteries.
    once a vehicle battery shows signs of degradation I give it a lighter duty, some go into a machine with a smaller engine, others end up as a UPS battery, the long ones with both terminals at one end spend their final years on a wooden tray next to one of two generators.
    in a nut shell the important vehicles get new batteries evey 5 years, everything else gets a hand me down, then they’re sold as scrap for about £5 each.
    charging batteries gives off hydrogen gas, don’t put them in a container with or without a lid, do it in the open raised off the ground.
    I’ve been told by many people that charging or storing batteries on concrete floors shortens their lives. has anyone else heard this or even know if it’s true?

    1. I have heard the concrete charging/storing bit as well. No one has been able to tell me why though. An up until now, never cared enough to research / find out. I never really have a reason to set them on concrete until I’m pulling a dead one, and stocking up for the scrapper run.

      1. There’s no problem leaving them charging on concrete/steel floor as the slight gassing ‘stirs’ the electrolyte. The problem occurs when the lower face of the battery is at a substantially lower temperature for long periods than the rest of it’s surface. The electrolyte then stratifies owing to differences in density between charged and depleted acid, made worse if the battery is slowly discharging.
        Basically, it grows sodding great insoluble sulphur crystals at the bottom of the plates.

      1. Thanks, it’s funny how we’re equipped with the basic knowledge(I remember rubber batteries) but fail to connect the dots, it also explains why really old cars rotted away so quickly around the battery.

    2. When I worked at the local battery factory (Chloride Electrical Storage Company – known as the Exide battery company) here in East London, South Africa back in the 1960’s, it was the practice to keep all batteries OFF the concrete while charging and after and there was apparently a leakage of current to earth, even if there was no dampness or moisture on the casing or between the poles, apparently the humidity in the air was the bugbear. Our experts apparently proved this to be true. Tommy Jackson and Karl Stein were their names.

    3. They were originally encased in wood which was coated and ‘sealed’ with a tar-like substance. Wood is obviously porous, so acid seeped out, and concrete can wick liquids quite well. Trades water for acid. No longer a problem with polymers

  6. No, the main reason this doesn’t work as sulphation mechanically wrecks the plates. The active material is not physically touching the charge collector grid so it does not conduct electrons. De sulfation will only help the parts of the paste that maintains physical contact to the bulk lead charge collector grid. Often times its large lead sulphate crystals that expand the paste making it non conductive, other times the grid corrodes so much that only part of it remains.

    Trust me on this one, I have thoroughly tested and then dissected dead batteries, there is no way to fix them except for remanufacturing.

    1. This is a really informative comment that gets at the heart of the problem: not the “chemical” problem of sulfates really, but the degradation of the battery plates themselves and the internal physical damage to the battery structure. Metal isn’t indestructible after all – just think of how many solder tips you’ve replaced because of pitting, or how you have to swap out the spark plugs every so often and there’s no way to “magically recondition” those.

      Tricks with using special electrical impulses to rejuvenate a battery by knocking sulfates off… well, it just seems like an indirect means at solving the problem, which gains favor primarily because you don’t have to open the battery up. Like solving a clogged sink with drain cleaner, rather than just running a drain snake. The second method is guaranteed effective solution to your problems, the first is more convenient but not 100%.

      I imagine you could completely tear down a battery and rebuild from scratch with new consumables, or just scrub the plates or whatever, but at that point are you really saving any more than just going to the store for a replacement?

  7. My experience with reviving any type of battery is that it simple doesn’t work. You will not regain internal resistance of overdischarged or old battery, that makes it pretty unreliable for any high current use (starting a vehicle for example). You can regain some capacity by desulfating but you will end up with other problems. For example low charge/discharge efficiency or overheating. Adding anything in sealed battery … no. When battery performance falls below reliable level you should take it to disposal facility and buy a new one, on the long run it’s the most efficient and safe thing you can do.

  8. I am a big fan of battery tender brand battery tenders. I have had a lawn tractor battery on one of them with a solar cell for what must be going on 10 years now and it still cranks right over. They combine proper 3 stage charging with pulsing to break the sulphates up on the plates. If you use one of these from the get go the battery will last a very long time.

    1. Exactly… and the previous comment… don’t let the battery sit discharged! Buy a good battery in the first place and keep it fully charged. I have been using “tested good” UPS batteries removed from service after 5 years on my lawn tractor for 4 years now. Still turns over. But AGM. The battery on the lawn tractor and the travel trailer is fully charged when removed, and topped up again in March.. All chemical processes sloooowww down in the winter, including battery self-discharge, so leaving them sit for a few months is OK… as long as they were put away fully charged. Sulfation process never sleeps… just needs a partially discharged chemical state to allow it.

  9. I dont have experience with desulfators but i did replace the sulfuric acid electrolyte with alum on a dead otherwise lead acid battery. Worked like a charm afterward. Ran fine in my truck for two more years till i sold the truck. It still may be fine afaik.

  10. I did try recharging 9 V alkalines, with half-wave rectification (1 diode) with some AC component added via resistor (several hundred Ohms) parallel to diode.The best I did is to get the battery to maybe 20% original amp-hour capacity. Good for desperate times only.

  11. I recently bought a smart car battery charger that is controlled by a mcu from Lidl:

    Besides several charging modes, it has a rejuvenating mode for dead batteries. I think it’s basically about de sulphation. I didn’t use it yet with a dead battery but I read numerous reports from trusted people on local messaging boards, and all of them state how effective it is. I remember one saying that he recovered a 4 year old Varta battery which was returned to him as unserviceable from a battery repair shop and that it cranks two years after that. Btw, the recovery process is very long, it usually takes around 40 days! Just do a search on “Lidl car charger”, you’ll find plenty of information. And it’s really cheap, too.

    1. Huh, I’ve actually impulse bought that charger for occasional charging duty because my pricey Ctek was being used to float charge a battery for a car I was currently doing a long term restoration of.

      Now I’m curious to find out if it’s actually better

  12. I worked on this back in the early 2000s. You can reverse sulphated cells without boiling the electrolyte, and without creating dendrites if you are careful and are constantly monitoring the process. When the battery cell plates shed active material, or a dendrite punches through the separator and shorts the cell, there is no externally-applied fix-it solution … you either recycle the battery, or you tear it apart and rebuild with pieces-parts from other batteries.

    Shedding active material means the cell(s) have less material to convert … and that means less available storage. It also means some of the electrolyte is tied up in that shed material as lead sulphate at the bottom of the jar (the quaint term battery folks used to use to describe a lead-acid battery cell container, as they used to be actual glass “jars”).

    Dendrites are created by high current points between the negative and positive plates, AND high charging voltages. You are removing elemental lead from one plate and depositing it on the other. The high energy potential creates a little peak (the dendrite) that will pierce the separator (either woven glass wool in AGM batteries, or polyethylene in flooded cells … though newer materials may now be used). When the dendrite grows into the opposite plate, it can start as a high resistance short … gently discharging the cell until all active material has sulphated. That’s the good way to short a cell. The other is a sudden low-resistance short that can, given the right location, ignite the hydrogen accumulated in the head space (top of the battery above the electrolyte level) … that is typically announced by your battery rapidly disassembling itself and flinging acid, lead, and plastic everywhere while releasing some serious stored noise (think a 10-gauge shotgun going off inside a phone booth). Not good. Don’t apply high voltage to a lead-acid battery.

    Sadly, this work is still under an NDA, otherwise there WOULD be working products on the market.

  13. I built a desulohator a few years ago to revive SLAs in backup unite, most of the time it worked great! Always topped up the fluids first. The times it didn’t there were shorts in the pack that I couldn’t overcome with my setup. It was just a MOSFET on a variable PWM from a 24V source

  14. I keep all of mine topped off and monitor them. While this is a bit extreme, it was a fun project and I don replace batteries very often. This system is powered by a 24v Battery bank powered by the sun. It has 4 Isolated chargers that do the work. Look at the shed systems tab.

  15. Most of the modern multistage smart chargers have a desulphtion stage at the beginning, I have vehicle that is only used once a year and unfortunately is not garaged or near a power point. I regularly go through batteries with this car as you can well imagine however this year I purchased one of these multistage smart chargers and removed the battery from the car, brand new 12 months ago and only used once, dead flat and sitting dormant over the Australian winter, not been charged, I initially tried with a standard charger no surprise but reported the battery faulty. New smart charger revived it and currently running no problems.

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