Float voltage characteristics of valve regulated lead-acid batteries

The float voltage of a cell, in comparison to the average float voltages of the cells within a battery string, is conventionally used as an indication of the ´state of the health´ of a particular cell. There is merit in this approach with respect to conventional cells with flooded electrolyte, but the concept appears to be inappropriate to valve regulated recombination type cells. Evidence to support this view is given. The authors also hold that there is no relation between the top of charge voltage value (TCV) of a valve regulated recombination (VRR) cell and its subsequent discharge capacity. Selection of VRR cells on a capacity basis is not appropriate to achieve a narrow band of cell TCVs. A method is proposed where by using narrow range regulation of the float voltages applied to VRR cells the recommended float voltage for powersafe cells could be reduced from 2.27 to 2.25 V per cell.<>