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**YALE** · 04-06-2015, 02:26 PM

Don't the plates become lead sulfate over time?

**Strychnine** · 04-06-2015, 02:38 PM

Originally posted by YALE View Post

Don't the plates become lead sulfate over time?

Written by some nerd somewhere

During use, small sulfate crystals form, but these are normal and are not harmful. During prolonged charge deprivation, however, the amorphous lead sulfate converts to a stable crystalline that deposits on the negative plates. This leads to the development of large crystals, which reduce the battery’s active material that is responsible for high capacity and low resistance. Sulfation also lowers charge acceptance. Sulfation charging will take longer because of elevated internal resistance.

There are two types of sulfation: reversible (or soft sulfation), and permanent (or hard sulfation). If a battery is serviced early, reversible sulfation can often be corrected by applying an overcharge to a fully charged battery in the form of a regulated current of about 200mA. The battery terminal voltage is allowed to rise to between 2.50 and 2.66V/cell (15 and 16V on a 12V mono block) for about 24 hours. Increasing the battery temperature to 50–60°C (122–140°F) further helps in dissolving the crystals. Permanent sulfation sets in when the battery has been in a low state-of-charge for weeks or months. At this stage, no form of restoration is possible.

There is a fine line between reversible and non-reversible sulfation, and most batteries have a little bit of both. Good results are achievable if the sulfation is only a few weeks old; restoration becomes more difficult the longer the battery is allowed to stay in a low SoC. A sulfated battery may improve marginally when applying a de-sulfation service. A subtle indication of whether a lead acid can be recovered is visible on the voltage discharge curve. If a fully charged battery retains a stable voltage profile on discharge, chances of reactivation are better than if the voltage drops rapidly with load.

Several companies offer anti-sulfation devices that apply pulses to the battery terminals to prevent and reverse sulfation. Such technologies tend to lower sulfation on a healthy battery but they cannot effectively reverse the condition once present. Manufacturers offering these devices take the “one size fits all” approach and the method is unscientific. A random service of pulsing or blindly applying an overcharge can harm the battery in promoting grid corrosion. Technologies are being developed that measure the level of sulfation and apply a calculated overcharge to dissolve the crystals. Chargers featuring this technique only apply de-sulfation if sulfation is present and only for the time needed.

Chemical additives have been used ever since the lead-acid battery became a commercial item, to reduce lead sulfate build up on plates and improve battery condition when added to the electrolyte of a vented lead–acid battery. Such treatments are rarely, if ever, effective.

Two compounds used for such purposes are Epsom salts and EDTA. Epsom salts reduces the internal resistance in a weak or damaged battery and may allow a small amount of extended life. EDTA can be used to dissolve the sulfate deposits of heavily discharged plates. However, the dissolved material is then no longer available to participate in the normal charge/discharge cycle, so a battery temporarily revived with EDTA will have a reduced life expectancy. Residual EDTA in the lead–acid cell forms organic acids which will accelerate corrosion of the lead plates and internal connectors.

The active materials change physical form during charge/discharge, resulting in growth and distortion of the electrodes, and shedding of electrode into the electrolyte. Once the active material has fallen out of the plates, it cannot be restored into position by any chemical treatment. Similarly, internal physical problems such as cracked plates, corroded connectors, or damaged separators cannot be restored chemically.

**homealone** · 04-06-2015, 03:39 PM

It's Epsom salts and distilled water. I have done it. Heat the water and disolve a 50/50 solution. If you have a battery with a build up on the plates, it helps. It will give you a bit more life. If it is actually shorted, it doesn't do a thing.

Edit* I should read the entire thread before I type.

**YALE** · 04-06-2015, 04:06 PM

EDTA is a chelant, so whatever it takes away is gone for good. Sounds like snake oil, really.

**yellowstang** · 04-06-2015, 04:39 PM

CraigsList, nuff said...

**Frank** · 04-06-2015, 10:06 PM

Yeah, kinda about what I figured. I do appreciate the article though Matt. Good info. I know I have kept a battery going for nearly 10 years in a project car just by keeping a trickle charger on it.

**mikeb** · 04-07-2015, 12:18 PM

Renew your lead acid batteries? Snake oil or real?

My understanding of why batteries fail is because of internal shorts, buildup of material at the bottom of the plates that eventually causes a short, or sulfation. I have also heard that cheaper batteries are made on purpose with less room at the bottom to make them fail quicker. That goo that you put in a battery has been around for a long as I can remember.

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Renew your lead acid batteries? Snake oil or real?

Renew your lead acid batteries? Snake oil or real?

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