Lead Acid Battery Desulfation

[Joseph]

I have a 12 year old battery with about 1/10 its new amp-hour capacity. Would it be worth while to spend the money or effort to try to desulfate it?

[MrAl]

Hi Joe,

How much did it cost when it was new?

[Joseph]

Hi Al,
it was about $70, almost real money back then. If I knew desulfation could restore it to 2/3 capacity or more with low risk of deposits breaking loose and shorting a cell, that could be a useful project.

[jollyrgr]

A lead acid battery has a life span of about five years. I'd say you got your money's worth.

What size (physical and electrical), design (Sealed gel cell, automotive, marine, etc.), and use is this battery for? Is there a part number?

[Joseph]

It is a car battery. It was about 60ah. I took it out of a car that was junked and reused it as a power back-up to run a little vent fan. A credit to the power company is that in all those years, it never got used.

[Smoke_Maker]

Joseph, the battery is kaput but if your into storage batteries this would make a great project if you have the time and curiosity. I wonder just how far you can bring back this battery.

If the battery is not damaged internally (cell inter connectors corroded away) or completely shorted cells from swelling, you can increase the capacity some.

To show improvement in capacity you need to measure before and after repair results, start by fully charging the battery and measure the time it takes to discharge the battery to 1.75 volts per cell at two or three different loads. Then try some different tricks to repair the damage father time has given it.

Batteries are like your dog, you can’t pin up your dog for a year or two and then expect it to run a marathon. But you can put your dog/battery in training to run a good race, 12 years is a long time for a battery or a dog, there old.

[Joseph]

Thanks for those thoughts. I loosely estimated its capacity by observing how long it took to come up from 11.8v to 12.6v under the output of a half ampere wall wart supply.

If it survives 'till spring, I also think that would be an interesting project.

[jollyrgr]

A 12 year old car battery is likely too far gone to be saved. My understanding is sediment collects at the bottom of these wet cells and shorts them out.

Since it is a car battery you have at least the possibility to try and recover it; but it is doubtful. Everything I've ever heard about car batteries is if your battery is five years or older you are on borrowed time.

[Joseph]

I think I see why that is true. As the lead sulfate breaks off of the plates, it is no longer available for energy outside the battery. Even if were converted back to separate lead and sulfuric acid, the lead would not be part of the plates where voltage is developed to force current through an external circuit. Thanks.