A method for managing electric quantity of a battery is disclosed. The method includes charging a battery normally with a 4.2V voltage when a temperature of the battery is lower than a first threshold temperature; charging the battery continuously when the temperature of the battery is higher than the first threshold temperature and lower than a second threshold temperature and the electric quantity of the battery is lower than a first threshold voltage. On the contrary, the battery is not charged any more when the temperature of the battery is between the first threshold temperature and the second threshold temperature and the electric quantity of the battery is higher than the first threshold voltage or a first capacity. If the temperature of the battery is higher than a second threshold temperature, the battery is not charged any more regardless of the battery voltage.