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.

15 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. If you are going to make a regular thing of linking to AvE’s videos, you would do us a service and at least pick ones where he knows what he is talking about. This one was particularly egregious, for example he mentioned repeatedly that the anode is positive, but in a battery current (conventional, not electron) flows out of the positive terminal making the positive terminal the cathode…

    1. 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

  2. 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

  3. 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.

  4. 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.

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