Epsom Salts Restores Lead Acid Battery

Despite a lot of advances in battery technology, lead acid batteries are still used in many applications due to cost and their ability to provide a lot of surge current. But they don’t last forever. However, [AvE] shows that in some cases a failed battery can be restored with — of all things — epsom salts. If it makes you feel funny to use the stuff grandpa soaks in when he has a backache, you can call it magnesium sulfate.

You can find a complete explanation in the video below (which includes [AvE’s] very colorful language), but fundamentally, the magnesium sulfate dissolves lead sulfate build-up on the battery plates. The fix is usually temporary because this build-up occurs with other failure mechanisms like plate material shedding and collecting at the bottom of the battery. Obviously, epsom salt can’t repair damaged plates or do any other magic cure.

We really enjoyed that [AvE] tore open a battery to show the plates and what was really happening inside. He also explains why the epsom salt might help.

We were surprised that he poured the salt directly into the battery. We were always taught to heat up some distilled water and saturate it with the epsom salt. Then you’d filter out any solid left and pour the water/salt mixture in until it couldn’t take any more.

Not only does this not always work, but it also doesn’t work instantly. We’ve heard of batteries treated with epsom salt or caustic soda reviving after several weeks. However, even if you don’t want to restore a battery with salt, there’s plenty of interesting battery facts and lore in the video that you’ll find interesting.

Everyone loves to point out how just about any project could have used a 555. That chip can charge your battery after you repair it. This isn’t the first time we’ve contemplated salting a battery, by the way. On the other hand, you can make a peculiar battery out of molten salt.

21 thoughts on “Epsom Salts Restores Lead Acid Battery

    1. You do not need your chemistry explanation to be correct if you reverse your statements frequently enough. The viewer will be inspired to open that dusty chem textbook (or look on Wikipedia) to figure out what you should have said. Additionally, if you get some of the facts completely wrong, that won’t matter either, because the bumbling explanation provides deep and foreboding hints, so that the viewer’s mind will be primed towards doing actual research (in books or on the lab bench) instead of accepting your errors as truth.

      Dwight Wayne Batteau once said (I quote from memory), “Every experiment turns out right. It may not be what you expected, and you may not even understand it, but it’s RIGHT.”

  1. while it may recover the chemistry of the battery it will not repair the plastic shell so once a battery has been broken open by dropping it or freezing it the battery is done for.

    the salt maybe able to recover batteries that have died of old age or cooked by over charging

  2. I have heard from a transmission rebuilder, that if your chassis and body grounds are not perfect, hooking to chassis ground for a jumpstart is a great way to fry the bearings in your engine and transmission. Would recommend not having your head right over the battery when making connections, but beyond that, do whichever at your own risk.

    1. When jump starting, after the jumped vehicle is running, disconnect the vehicle used to provide the starting power first. Then the cables can be disconnected from the other vehicle.

      If the alternator is working and the battery accepting charge, it will potentially be gassing off a lot more hydrogen than under normal conditions. I’ve seen one battery partially explode when someone disconnected the cable from the jumped car’s negative battery terminal first. Blasted that post and the corner of the case off.

      1. Well thats’ plain FUD from the OP.

        You certainly should be hooking up negative lead from engine to engine when jump starting.
        Which stops the second problem.

        Putting jump leads on the neg batt terminal; find me a set of jump lead instructions which say to do this.
        And you found a crappy product.

  3. I’ve done similar, completely swapping the acid electrolyte for Aluminium Sulfate. The chemistry change caused around 1V drop in voltage but the capacity was good and deep cycling tolerance was improved. The only issue was dealing with the modified voltages during the charge cycle – existing chargers tended to overcharge and and boil off electrolyte.

  4. There’s a hole in your logic where the Canadian electron sits…. not to undermine your persnickety comment entirely, Mr Scott’s repeated frickin’ reversals in his explanation did make me ask myself if he shoulda maybe kinda possibly tried a bit of editing…. KYSOTI

  5. Okay, after the salt treatment and charge, residue sinks to the bottom where it can shortcut the plates. How about flushing and refilling it after the treatment, removing the residue? (Fill with distilled water or some acid?)

    1. How about flushing and refilling it after the treatment, removing the residue?
      Yes flush it many times and with distill water last time then refill it with battery Acid (H2SO4..diluted) available from Lead Acid battery Shops

    2. Lead Sulphate is nonconductive. That’s why the battery is unable to recharge and discharge properly. As an insulator, it can never cause short circuits. The loose sulphate around the bottom of the battery will eventually dissolve away when the battery is recharged and used for some time. It will be converted back into a conductive Lead Sulphide layer on the battery plates when the cells are recharged.

  6. Just did my 18 month 5 year warranty but not on the replacement battery, walmart neverstart. First the battery must be flushed 2 to 5 times with a mixture of baking soda and water, shaking, draining and refilling to get all the dirt out. The mix up you epsom salt aka:magnesium sulphate mixture with 12 oz to 1 gal of distilled water, then charge and discharge the shiite out of it a few times with a 10 amp charger to full charge, set you charger on maintenance and trickle for a while, then finish it off with a float charger to keep it at full charge. I’ve been running my guitar amp, 12 volt lamp, fan, etc for hours and still can’t get the battery to get below 11.5 volts.

    1. Gary, I have this tall tubular lead acid battery. Bought it 3 years ago. The service person came and checked the gravity of the cells. One of the cell gravity seems very low. He said battery needs replacement. The battery runs ok with lights and tubes but when I rub computer and refrigerator inverter trips saying low battery. Shall I just did as what you did? Or do I just need to add Epson salt water into the low gravity cell by draining it?

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