PRINCIPAL OPERATION OF
VRLA BATTERY
Positive Plate.......... PbO2+SO4+4H++2e-=PbSO4+H20
Negative Plate..........PB+SO4-= PbSO4+2e-
Net.........................PbO2+2SO4-+4H++Pb=2PbSO4+2H2O
The gassing and water loss reactions are as follows:
Positive Plate..........H2O+2H+=1/2O2+2e
Negative Plate.........2H++2e-=H2
Net........................H2O=H2+1/2O2
It is noted that the gassing reaction only generally occurs to any extent when the battery is almost totally charged.
In the valve regulated battery it is obvious that water loss must be avoided. This is done by limiting the escape of hydrogen and oxygen from the battery. The design therefore accomplishes the recombination of the oxygen formed at the positive plate with the hydrogen formed at the negative plate. The reaction is as follows.
Positive Plate..........Pb+1/2O2+H2SO4=PbSO4+H2O
Negative Plate.........PbSO4+2H++2e-=Pb+H2SO4
Net........................1/2O2+2H++2e-=H2O
This virtually eliminates the production of free hydrogen at the negative plate to the action of recombination.
However it is necessary to ensure that correct charging voltages are used.
Valve Regulated Lead acid batteries are sometimes called recombinant cells because the construction provides a means of recombining the internally generated hydrogen and oxygen and the suppression of the evolution of hydrogen gas to limit the consumption of water from the electrolyte. Therefore the battery requires No addition of water during its normal life time.
Deutsche Power valve regulated batteries are of the Absorbed Electrolyte type. The cells are designed so that a highly controlled amount of electrolyte is contained within a highly absorbent non-woven separator material that separates the battery plates. This type of separator construction allows the full wetting of the plates with the available electrolyte and also allows the passage of oxygen generated during charging, this method of construction is generally referred to as Absorbed Glass Mat (AGM) type of construction.
Valve regulated batteries are sealed with the exception of a valve that opens when excess pressure builds up inside the battery. The valve automatically reseals itself. The recombination of charge gases is accomplished by allowing oxygen produced at the positive plate to pass through the separator material to the negative plate where the recombination reaction occurs. The valve controls the internal of the battery to optimize this efficiency of the recombination reaction and minimize the possible escape of electrolyte.