Lead acid, recombining, maintenance free

Starved electrolyte battery — A -> battery with minimum amount of -> electrolyte. The electrolyte in starved electrolyte cells or batteries exists in the porous structure of the - electrodes and absorbed in the separator, so it contains little or no free fluid electrolytic solution. This type of batteries is used in certain constructions of sealed - lead-acid and -> nickel-cadmium batteries that rely on gas diffusion and recombination on the electrodes during charging or overcharging in order to maintain maintenance-free conditions, and to suppress pressure buildup. Starved electrolyte batteries benefit from larger - energy density due to the reduced amount of electrolyte. This design may suffer from poor heat dissipation compared with -> flooded batteries, thus for high power applications this point has to be taken into account. 

In recent years there has been a tendency to prefer Pb cells instead of NiCd cells. This has been due to the development of what has become known as maintenance free or sealed type lead-acid batteries. The basic concept is one of retaining the gases evolved during the charging process and to allow the oxygen to recombine as float charging takes place, see Reference 4. If the operating and ambient conditions are not subject to excessive variation then the concept is satisfactory in practice and the life expectancy of the battery can be as much as 10 years. 

Since the 1970s also maintenance-free valve-regulated lead-acid batteries have been in widespread use in the field of stationary applications. Sometimes they are called recombination cells or "sealed lead-acid cells". Their correct designation, however, is in accordance to DIN 40 729 valve-regulated lead-acid batteries ( VRLA batteries). 

Besides the usage of clean materials and antimony-free lead alloys for the construction of batteries, the so-called oxygen recombination is the basis for the function of valve-regulated maintenance-free lead-acid batteries. Because of the thermodynamic locations of hydrogen and lead, a complete prevention of decomposition of small amounts of water generally is not possible. But the oxygen... 

The sealed gel technology was developed a number of years ago by the Sonnenschein Company in West Germany. Simply stated, a gel cell is a lead-acid battery that uses a thick chemotropic gelled electrolyte that is the consistency of candle wax once it sets up and is pressurized and sealed using special valves. It uses a recombination technique to replace the oxygen and hydrogen normally lost in a wet-cell battery, and it is maintenance free and nonspillable [7,28]. 

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