Study on an active voltage equalization charge system of a series battery pack

Because of the advantages of fully sealed, without leakage, without pollution and without maintained in its used period, valve regulated sealed lead-acid battery can ensure the safety of human body and all sorts of electrical equipments. Now valve regulated sealed lead-acid battery has widely used as stand-by power in power industry, communication industry and other industries which need stand-by power. The voltage of single battery is limited, its range usually only has 2V to 2.2V, So battery packs are usually used in a lot of stand-by power systems. Battery pack is composed of many single battery which is in series. Because of the differences of battery's manufacturing techniques, chemical compositions, used environment and operated history, the characteristics of each battery which is in series battery pack has unconsistency. With the battery pack's cyclic charged and discharged, unconsistency of single battery in the same battery pack will be expanded. This will cause differences of final discharge voltage of each single battery in one battery pack, although they are run in the same condition of charged or discharged. This kind of unconsistency will also cause Domino's chain reactions among single batteries in the same battery pack. In such a way, the actual service life of one battery pack will be shorten greatly. For a battery pack, if it is not managed and maintained in time, the capacity, service life, and performance of the entire battery pack are affacted, at the same time, the system's reliability whose stand-by power is such a battery pack will be reduced greatly. In order to prolong the service life, the same depth of discharge of each single battery must be kept consistency. This problem can be solved by active equalization charge to a battery pack. In this paper, a practical method of active equalization charge to a battery pack is put forward. Tested and verified by practical application in worksite, the voltage of each single battery tends to consistency basically in the same one battery pack, the effect of active equalization charge to a battery pack is satisfied.