Battery management system and method for extending battery lifetime

A battery management system for extending battery lifetime, comprising:

• a battery monitoring circuit connected to a battery cell;
• a control circuit connected to the battery monitoring circuit;
• and
• a balancing circuit connected to the battery cell and the control circuit;
• wherein, in a test mode, the control circuit is configured to output a plurality of pulse wave modulation signals to the balancing circuit respectively within a plurality of time intervals, and the balancing circuit is configured to control a charging frequency of the battery cell according to a plurality of frequencies of the plurality of pulse wave modulation signals respectively within the plurality of time intervals;
• wherein, in the test mode, the battery monitoring circuit is configured to monitor and output a plurality of alternating current (AC) impedances of the battery cell respectively within the plurality of time intervals;
• wherein, in the test mode, the control circuit is configured to compare the plurality of AC impedances with each other to select one of the plurality of AC impedances, and set the frequency of the pulse wave modulation signal that is outputted for controlling the charging frequency of the battery cell such that the battery cell is charged to have the one of the plurality of AC impedances as a practical frequency;
• wherein, in a practical use mode, the control circuit is configured to output the pulse wave modulation signal having the practical frequency, and the balancing circuit controls the charging frequency of the battery cell according to the practical frequency of the pulse wave modulation signal for reducing a reversible impedance of the battery cell.