Charger and charging method

A charger for charging a battery, comprising:

• a charging module for charging the battery with a constant charging power;
• a detecting module for detecting a battery voltage;
• and
• a control module for receiving signals from the detecting module and controlling the charging module, the control module comprising:
• a timing unit for timing;
• and
• a computing unit for computing data,
• wherein the control module is operable to control the charging module to charge the battery with the constant charging power until the battery voltage reaches a predetermined voltage, to charge the battery with a charging current for a predetermined charging time, wherein the charging current is less than a charging current used during the charging with the constant charging power, wherein the charging time for the first time is a predetermined first value, and the charging time after the first time is a changing value determined by a battery capacity, and wherein the charging is ended if the charging time is less than a predetermined second value;
• and
• wherein the control module is operable to control the charging module to determine if the battery voltage of less than the predetermined voltage:
• if yes, returning to the previous step;
• if no, charging the battery until the battery voltage reaches an actual voltage threshold that exceeds the predetermined voltage, and returning to the previous step.