Method for charging battery

A method for charging a battery, the method comprising:

• performing a first-constant-current charging the battery with a constant current having a first intensity;
• determining a voltage of the battery rises above a first voltage level;
• ending the first-constant-current charging;
• performing a second-constant-current charging of the battery with a constant current having a second intensity that is less than the first intensity;
• determining a voltage of the battery rises above a second voltage level that is higher than the first voltage level;
• ending the second-constant-current charging;
• performing a third-constant-current charging the battery with a constant current having a third intensity that is less than the second intensity;
• determining a voltage of the battery rises above a third voltage level that is higher than the second voltage level;
• ending the third-constant-current charging;
• performing a constant voltage charging the battery with a constant voltage having the third voltage level;
• determining a charging current of the battery falls to a fourth intensity that is less than the third intensity;
• and
• ending the constant voltage charging.