A power battery system includes a number of parallel groups that being connected in series and a number of improved electrode boards. Each of the parallel groups comprising a number of single batteries connected in parallel. Each of the improved electrode boards being connected between two neighbored parallel groups. Each of the improved electrode boards includes a number of electrode contact plate, a conductive substrate, and a number of security devices. Each electrode contact plate connects two neighbored single batteries of two neighbored parallel groups in series. Each of the security devices corresponds to an electrode connection plate and electrically connects an electrode connection plate to the conductive substrate. Each of the security devices fuses when one of the single batteries of a parallel group occurs short circuit.