Abstract: To express the influence upon the service life of battery packs coming from cell inconsistency,the sources leading to cell inconsistency are analyzed,i.e.those coming from the manufacture and application of the battery.Based on the data of battery service life tests,a mathematical model of the battery pack under the influences on cell inconsistency is established.At the same time a loss coefficient in battery capacity is defined.Through theoretical analysis and vehicular operation the importance of improving cell consistency and refinements in packing technology are verified.Maintenance safeguards during the application and maintenance of battery packs are put forward so as to prolong the service life.