Battery Sulfation: What It Is and How to Stop It

Written by on November 15, 2012 in Technology - No comments | Print this page


An understanding of the concept of battery sulfation and desulfation requires some knowledge of the chemistry of a lead-acid battery. The lead-acid battery has been used to start our automobiles for nearly a century, and the chemistry and basic construction of these batteries remains unchanged.

The Lead-Acid Battery

Consisting of lead plates manufactured in two forms, the lead-acid battery is a a plain lead metal plate and a plate of lead dioxide. In the wet lead-acid battery, a sulfuric acid solution serves as the electrolyte between the plates. In the battery’s manufacture, these plates are attached to separate terminals and the two types of plates are in the fully charged state. As current flows from terminal to terminal during discharge, both plate surfaces in the battery are converted to lead sulfate, both electrodes are sulfated.

Recharging reverses the process, and the plates are desulfated with the sulfate returning to the solution of electrolyte. The automobile starter battery is not discharged greatly during use and is quickly recharged fully during engine use. The amount of sulfation that takes place is fresh and instant recharging desulfates the plates, in an ideal world, completely.

Unfortunately, neither sulfation nor desulfation is a perfect process. Some sulfate is not released into the electrolyte during each discharging-charging cycle. As the lead sulfate builds up it ages and slowly converts to a crystalline form. During normal recharging, this crystalline form is not reactive and fails to dissolve.

Deep-Cycle Batteries

The introduction of valve regulated lead acid and deep-cycle batteries have magnified the problem of sulfonation. The automobile battery will operate for long periods with little obvious loss in power unless it is discharged completely. However, deep-cycle lead acid batteries are designed to be discharged up to 50% to 80% of capacity, depending on the manufacturer and construction.

Deep-cycle batteries often serve as backup power systems for emergency lighting, sump pumps and medical equipment. They are also common in golf carts and serve as photovoltaic power storage systems. A similar situation involves VLRA (both AGM and Gel type) batteries. VLRA maintenance free batteries operate safely in any position and in closed spaces. They find use in marine applications, RVs, wheelchairs, forklifts, uninterrupted power supplies  for computers and remote instrumentation.

These batteries are designed to resist corrosion through extended charge and discharge cycles but the build up of lead sulfate and the time between recharges increases the potential for formation of crystalline lead sulfate.

Eventually, without effective desulfation, the plates become increasingly insulated by the sulfate coating and the battery develops such high internal resistance that only a small fraction of normal discharge current can be obtained.


Fortunately, methods for desulfation during charging have been developed for removal of deposits of crystalline lead sulfate. A constant high voltage, high current recharging would seem an approach; however, the net result is overheating and warping of the plates. Alternatively, pulse conditioning has been developed to breakup the sulfate crystals without overheating the battery. In pulse conditioning, short powerful current surges are repeatedly applied to the terminals to breakup the crystalline sulfate without overheating.

Electronic circuits control the widths and frequency of the high current pulses. These circuits also allow for automation of the process when a long desulfation time is required for a heavily sulfated battery. Battery chargers electronically configured for desulfating lead-acid and VLRA batteries, such as the Batteryminder, are commercially available. Batteryminder chargers are designed for a variety of installations and applications.

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This is a guest post.  Greg Wilkins contributed this post on behalf of Chemical Wire, a U.K. leader in providing research chemicals.


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