Adding chemicals to the electrolyte of flooded lead acid batteries can reduce the buildup of lead sulfate on the plates and improve the overall battery performance. This treatment has been in use since the 1950s (and perhaps longer) and provides a temporary performance boost for aging batteries. It’s a stopgap measure because in most cases the plates have already been worn out through shedding. Chemical additives cannot replace the active material, nor can cracked plates, corroded connectors or damaged separators be restored with an outside remedy.
Extending the service life of an aging battery is a noble desire. The additives are cheap, readily available and worth the experiment of a handyman. Suitable additives are magnesium sulfate (Epsom salt), caustic soda and EDTA. (EDTA is a crystalline acid used in industry.) These salts may reduce the internal resistance of a sulfated battery to give it a few months of extra life. Using Epsom salt, follow these easy steps:
Heat up the water to about 66°C (150°F), mix 10 heaping tablespoons of Epsom salt into the water and stir until dissolved. The consistency of the brew should vary according to the extent of the sulfation. Avoid using too much salt because a heavy concentration will increase corrosion of the lead plates and internal connectors. Pour the warm solution into the battery.
Be careful not to overfill. Do not place un-dissolved Epsom salt directly into the battery because the substance does not dissolve well. In place of Epsom salt, try adding a pinch of caustic soda. Charge or equalize the battery after service. The results are not instantaneous and it may take a month for the treatment to work. The outcome is not guaranteed.