CHARGING METHOD FOR NONAQUEOUS ELECTROLYTE SECONDARY CELL AND CHARGING SYSTEM FOR NONAQUEOUS ELECTROLYTE SECONDARY CELL

A method for charging a nonaqueous electrolyte secondary battery includes a first charging step of charging a first capacity Qat a first constant current value I, the first capacity Qincluding a capacity range in which dQ/dQ is more than or equal to a predetermined threshold value, a second charging step of charging a second capacity at a second constant current value more than the first constant current value, a detection step of acquiring at least one of dV/dQ and dQ/dQ, and a changing step of changing at least one of the timing of switching between the first charging step and the second charging step and the first constant current value Ion the basis of a change in time of dV/dQ or dQ/dQ.