The charge equalizer-a new system to extend battery lifetime in photovoltaic systems, UPS and electric vehicles

Investigations of battery banks in photovoltaic systems, UPS and electric vehicles show that individualization of single cells due to different properties leads to premature failures of the whole battery. Single cell monitoring is no way to overcome this problem. The new "charge equalizer" (CHEQ) introduced in this paper keeps all cells in the same state of charge at all times by transferring energy between the cells. For different applications, specially suited implementations of this fundamental principle are shown. The main advantages of the CHEQ will be: protection against overcharging and deep discharging of individual cells, extension of lifetime, decrease of maintenance costs, availability of the full nominal capacity.