Patent ID: 8482262

Claim:
A method, comprising: charging a battery module comprising at least two nonaqueous electrolyte secondary batteries wherein the charging is carried out at a temperature of the battery module of from 45 to 90° C. and until a maximum end-of-charge voltage V 1 (V) for the at least two nonaqueous electrolyte secondary batteries is a value represented by formula (1): 0.85× V 0 ≦V 1 ≦0.96× V 0 (1) where V 0 denotes a maximum end-of-charge voltage (V) of the nonaqueous electrolyte secondary batteries when the battery module is charged fully at 25° C., wherein each of the nonaqueous electrolyte secondary batteries comprises a negative electrode, a positive electrode and a nonaqueous electrolyte, the negative electrode comprising a negative electrode layer and a current collector having the negative electrode layer present thereon, and the negative electrode layer comprises lithium-titanium composite oxide particles, wherein the current collector is an aluminum foil or an aluminum alloy foil and the crystal grain size of the aluminum or aluminum alloy is no larger than 50 μm.