CAPACITY ESTIMATING METHOD AND DETERIORATION DIAGNOSTIC DEVICE FOR BATTERY PACK

PROBLEM TO BE SOLVED: To provide a capacity estimating method and a deterioration diagnosing device for a battery pack, capable of conveniently and accurately estimating the capabity. SOLUTION: Since a linear equation is decided by using cells B1 and B2 composing the battery pack 8 of the capacity to be estimated, the linear equation accurately reflects usage histories of cells B1-B5 composing the battery set 8. Accordingly, by introducing internal resistances R3-R5 of the cells B3-B5 to the linear equation, capacities C3-C5 can be estimated accurately. Consequently, the capacity C of the battery pack 8 can be estimated accurately. The linear equation can be determined merely by measuring internal resistances R1 and R2 and capacities C1 and C2 concerning a part of the cells B1 and B2, and the capacities C3-C5 can be estimated just by measuring the internal resistances R3-R5 in regard to the rest of the cells B3-B5. Consequently, the capacity of the battery pack 8 can be estimated easily.