Keeping up the pressure — strategies to maintain plate-group pressure and extend the cycle life of VRLA batteries

For valve regulated lead acid (VRLA) applications involving deep cycling, significant cycle life improvement can be achieved by applying pressure to the plates via the compressible recombinant battery separator mat (RBSM). However, the latest work is showing that the plate-group pressure needs to be much higher than previously assumed, in order to inhibit positive active material expansion and capacity loss. This will require changes not only to the separator, but also to the battery design and assembly techniques. Techniques to apply very high pressures to the cell group during battery assembly need to be developed. Changes to the container design and materials may also be needed, and the overall battery design may need to include an internal or external means to maintain the applied pressure throughout battery life. Less compressible separators may also enable higher plate-group pressures to be maintained.