Patent ID: 8773069

Claim:
A secondary battery charging method comprising the step of: determining whether to perform one of a first charging control method of performing constant current charging and constant voltage charging and a second charging control method of performing only the constant current charging according to information stored in a plurality of secondary batteries which includes a compound oxide particle with an olivine crystal structure as a positive electrode active material and are connected to each other in series, wherein the first charging control method includes the steps of performing the constant current charging of the secondary batteries until the voltages of the plurality of secondary batteries connected to each other in series become a predetermined battery voltage, performing the constant voltage charging after the voltages of the secondary batteries become the predetermined battery voltage, determining whether voltage variation amounts of the plurality of secondary batteries are a value equal to or greater than a first set value within a first predetermined time by measuring the voltage variation amounts of the plurality of secondary batteries after the constant voltage charging starts, and storing information used to select the second charging control method in the secondary battery and firstly terminating the charging when it is determined that the voltage variation amount of at least one of the plurality of secondary batteries is the value equal to or greater than the first set value within the first predetermined time in the step of determining whether the voltage variation amounts of the plurality of secondary batteries are the value equal to or greater than the first set value within the first predetermined time, and wherein the second charging control method includes the steps of starting the constant current charging of the plurality of secondary batteries connected to each other in series, and secondly terminating the constant current charging when the voltage variation amount of at least one of the plurality of secondary batteries is a value equal to or greater than a second set value within a second set time.