Completion determination method and discharge end determination method for lithium ion secondary battery, charge control circuit, discharge control circuit, and power supply

摘要

A method for determining completion of charging of a lithium ion secondary battery that can withstand long-term use is provided. In the charging of a lithium ion secondary battery including one type of lithium compound having an olivine crystal structure as the positive electrode active material and including a graphite material as the negative electrode active material, the S1 step of charging the amount of electricity Xc at time Ti1, and the S1 step After the end, the charging is stopped for a time Yc and the battery voltage Vi1 is measured after the elapse of Yc, the S3 step for charging the electric quantity Xc at the time Ti1 after the end of the S2 step, and the end of the S3 step After that, the charging is stopped for the time Yc and the battery voltage Vi2 is measured after the elapse of the time Yc, and Vi2-Vi1 is compared with the predetermined voltage difference Vi3. If Vi2-Vi1 Vi3, the charging is completed. And a step of determining completion of charging including a step of determining that charging is incomplete if Vi2−Vi1 ≦ Vi3.