IEE: Impact of Microcycles on Batteries Microcycles and Batteries_publ-EVS18.DOC 1 / 12 The Impact of Microcycles on Batteries in Different Applications

In most applications batteries are subjected to a complex current profile which is determined by the charging unit and the loads. Microcycles, a frequent change of the direction of the battery current, are the norm in all applications where charging and use of the battery to supply loads take place simultaneously, or reactive power is needed. That is the case in many different applications, from autonomous PV Systems to vehicles with generators or with feed back of braking power. The effect is particularly strong in systems incorporating loads with varying power such as single phase AC loads or loads with simple on/off control algorithms. Current pulses are usually in the range of up to a few hundred Hertz. The impact on different types of batteries caused by this has not yet been thoroughly investigated. To investigate the impact of microcycles it was necessary to build at first a test unit. The test equipment had to fulfil as main requirements the generation of rectangular pulses for charging and discharging, frequencies in the range from 0.01 to 15.000 Hz and currents from 2 to 200A. In addition a special mode called “zero Ah control ” was realised. The results of laboratory tests on flooded lead acid batteries show that batteries lose capacity an