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An Account of Lead Acid Battery Restoration Using EDTA Tetrasodium

Jon Kenneke

©1996 Jon Kenneke

After reading the several stories in Home Power describing how to "restore" lead-acid batteries, it was time to try it. Most lead acid batteries are disabled by a build-up of sulfur on the lead plates (sulfation). There are two methods to break sulfation: chemical (using EDTA tetrasodium), and electronic using a pulsed device that electrically breaks the bond. For this first try, chemical chelating agents are used. Refer to the article in Home Power #20 & #21 for details.

EDTA tetrasodium is a chelating compound. This means that it has the ability to break crystal bonds. In this case, it is breaking the bond between the lead and the sulfate crystals.

I collected six old lead-acid batteries as my test subjects. Two of these batteries are Exide, two are Sears Die Hard, one Les Schwab, and one Fred Meyer brand. They vary in age and usage. Five of the batteries were deep-cycle (Exide, Die Hard, Fred Meyer), and one was a standard car battery. I decided to use a car battery for comparison. After the test, four batteries came out usable.

The Exide batteries were used in a bass fishing boat to run a 24 volt trolling motor. They were used in series. One of the Sears Die Hard batteries was used in a 12 volt trolling motor. The other Die Hard was used as an electric fence charger, drained to about 60 percent before charging. The Fred Meyer battery was used in an RV. Of course, the car battery was used in a standard automotive application.

These batteries are not industrial quality units, like many renewable energy people use. But, they provide a good comparison for EDTA effectiveness. And, many folks do use "consumer" quality cells in their power systems. These batteries are cheap, and easy to get. Enough said.

The three batteries used to drive trolling motors were deeply (80 percent or more) cycled, and cycled twice every weekend during the bass fishing season. They would sit in the off season, self-discharging. Some fisherman use trickle chargers, but the sources of these batteries did not. Hardly an ideal situation. The other batteries were charged on a consistent basis.

I checked the specific gravity and voltages on all the batteries before applying EDTA tetrasodium and charging. The EDTA was obtained through Fisher Scientific, to guarantee purity. A 500 gram bottle was purchased for around 20 dollars. This bottle came factory sealed, and fully warranted to be pure. I obtained this through a local distributor. (See access section).

The specific gravities of all the batteries indicated that they needed recharging—around 1.225 (less than the ideal specific gravity of 1.260). This was a good indicator of sulfation.

As specified, 1 tablespoon of EDTA tetrasodium was added to every quart of electrolyte. The EDTA dissolved readily in distilled water. It was interesting to note that the battery cells fizzed after adding the EDTA. This was alarming. This happened in all the batteries, but did not seem to be an indicator of trouble.

It is important to avoid contact with the electrolyte in batteries. I highly recommend using rubber gloves, and eye protection. I used eye protection, but no rubber gloves. I have acid burns as proof that avoiding contact with skin is VERY important. Please take heed to my advice. This can be a very safe procedure if you are prepared. Use your brain.

After adding the EDTA, the batteries were gently shaken to thoroughly mix the EDTA with the electrolyte. This is an important step, as I have learned from previous experience. Be careful not to shake to batteries too hard and spill the acid electrolyte. Remember, acid can be neutralized with baking soda. Just make sure that none enters the battery cell.

After the EDTA was added, all the batteries were charged at the C/10 rate. The EDTA treatment works best (according to literature) if the cells are put in an equalizing charge for 8 hours. At the end of this charge, the batteries could be heard "boiling".

After the equalization charge, the batteries were put on a standard charge for 12 hours. After this, cell voltage and specific gravity were measured again.

The measured values are in the chart, below:




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