AC, noise and migration in the battery installations

In this paper AC current ripple during float, charge, and discharge of a battery string are presented and analyzed. The effect of AC power dissipation on battery temperature and the simple method of its calculation is discussed. Laboratory experimentation was conducted in order to establish the AC power loss characteristics and its variation with frequency. The typical AC common mode waveforms for various installations as well as the load supplied by the batteries is also presented and discussed. The source of such signals and its propagation is explained. The results of individual cells monitoring in a large battery installation with high precision battery monitoring equipment is presented. It was discovered that the voltages of the individual cells do not remain steady, but change their value with time