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Old 02-09-2010
Chasedan Chasedan is offline
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Join Date: Apr 2007
Location: Grand Rapids, MN
Posts: 37
Cool Has Anyone Tried Reviving a Lead Acid Battery with Epsom Salt Solution?

Hello All,
Its been a while since I posted here. Quick question, has anyone tried to revive an old, failing lead-acid car battery with an Epsom Salt (magnesium sulfate) solution? If so how well did it work?

Thanks for any input

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Old 02-09-2010
twospeed's Avatar
twospeed twospeed is offline
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Join Date: Mar 2008
Location: chicago Il
Posts: 400

I have used a 50/50 mix of baking soda and water with good results. Be careful as when you fill the battery it will shoot up at you. let it sit for a day and then flush out with water , add new acid and you should be good to go.
Perfection thro simplicity
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Old 02-09-2010
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Nickodell Nickodell is offline
Join Date: Jan 2007
Location: Phoenixville, in S.E. Pennsylvania
Posts: 2,571

It's a trick the few of us in college who could afford to run any kind of car used to use when the battery quit. The 6v battery in my old 1939 Austin 8 (8 hp, not cylinders!) quit, and by experimenting I found that one cell had completely shorted internally. At first I bypassed this cell, and for a while ran it as a 4v battery, but the generator, receiving little back-emf, cooked this. I then got one in similar condition from a fellow student who had persuaded his parents to buy him a new one, and I was going to use a product called "Renewbat," being sold by the equivalent (in 1955) of Pep Boys in the UK. Being chemistry geeks, we investigated and found that this magic substance was simple Epson salts (magnesium sulfate) costing pennies. It gave another 6 months of useful life.

How to do it. Dissolve about 8 ounces of Epsom salts in a pint of hot distilled water. Take the battery out of the car and place it on a large trash bag liner on a concrete floot. Wearing goggles, take off the cell caps and, using a syringe (the large plastic ones you can buy from petfood stores, intended for giving cats and dogs liquid medicine), carefully remove about 40ml of acid from each cell. Carefully dispose of this by slowly decanting it into the toilet and flushing. When the Epson salts mixture is cool, use the syringe to decant the same amount into each cell, replace the plugs, and [this is the most risky part] lay the battery on its side and back vertical half a dozen times to mix the contents.

Then put it on a long, slow (1 to 2a) charge. There's no guarantee that it will work in every case, and if you have a sealed battery you're S O L, as there's no way to safely get the solution into it.

As they age, batteries lose the capacity to hold a charge because the lead in the plates eventually becomes sulfated (quickly if left discharged). The MgSO4 appears to remove at least part of this coating, although the lead that has been converted to the sulfate is lost, so you will never get the original capacity back. Maybe 70%.

A note on battery life. My wife's Nissan Sentra is 12 years old, and the original battery lasted 11 years. It might have gone on longer, but was cranking more slowly and I didn't want her to get stranded with the winter of 2008 approaching. I was so impressed that I removed the battery to see what make this remarkable model was (it was fitted with the label facing where you couldn't see it), and found that it was a Panasonic. I didn't even know they made car batteries. Try as I might, I couldn't obtain one through any of the usual outlets, or even my garage. They are apparently, only OEM. Seems to be a conspiracy there, to sell us an endless series of 6-7 year batteries.
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