Self-Equalization of Cell Voltages to Prolong the Life of VRLA Batteries in Standby Applications

The valve-regulated lead-acid battery has been the work horse of standby applications for several decades. Float charging is normally implemented in these systems. However, float charging tends to overcharge the battery, causing water loss and grid corrosion which shorten the service life of the battery. This limitation may be avoided by using cell voltage equalization and temperature-compensated interrupted charge control (TCICC). Cell voltage equalization reduces the voltage distribution range over many cells, which, in turn, means that there are fewer cells with either overvoltage or undervoltage, both of which shorten the life of the battery. TCICC can increase the service life of the battery by avoiding overvoltage. Experimental evidence is presented to validate the new approach by comparing float charging and TCICC in terms of battery voltage equalization and temperature response.