Management system for Lithium iron phosphate(LiFePO4) power batteries group is built，based on car battery series charge features. Series charge experiment of power batteries group is carried out using battery charger. Single cell voltage and state of charge(SOC) is analyzed in series charge for batteries group. Dispersivity influence of single cell is studied on charge performance of the battery packs，small current supplementary charge equalization is proposed，to make single cell battery state of charge is basically almost the same. Theoretical analysis and experimental results show that single cell voltage difference is very large，but SOC difference is very small in the end of battery series charge. A novel battery packs charge equalization method is presented，which avoids the problem of some batteries overcharge and other batteries less chargedproblem.