Battery charging system and method

A battery charging system for charging a rechargeable battery, comprising:

• a temperature sensor configured to be positioned on an outer surface of the rechargeable battery and configured for continuously sensing a current temperature T of the rechargeable battery;
• a voltage measuring device configured to be electrically connected to both a positive electrode and a negative electrode of the rechargeable battery and configured for continuously measuring a current voltage U of the rechargeable battery;
• a processor storing a first temperature threshold T1 and a second temperature threshold T2, and a first cut-off voltage U1 and a second cut-off voltage U2, wherein T1<T2, and U1>U2, the processor configured for:
• comparing the current temperature T with the first and second temperature thresholds T1 and T2, and comparing the current voltage U with the first and second cut-off voltages U1 and U2;
• and
• generating a PWM control signal according to the results of the temperature comparisons and the results of the voltage comparisons;
• and
• a power supply for providing electrical power;
• and
• a charger electrically connected to the processor and the power supply, and configured for providing a charging current to the rechargeable battery according the PWM control signal of the processor;
• wherein when the current temperature T falls into the range T1˜T2, the charger is configured for charging the rechargeable battery using a first average current I1;
• if the current voltage U reaches the first cut-off voltage U1 while the current temperature T remains in the range T1˜T2, the charger is configured for stopping charging the rechargeable battery;
• if the current temperature T exceeds the range T1˜T2 before the current voltage U reaches the first cut-off voltage U1, the charger is configured for charging the rechargeable battery using a second average current I2, wherein I1>I2;
• if the current voltage U reaches the second cut-off voltage U2 before the current temperature T exceeds the range T1˜T2, the charger is configured for stopping charging the rechargeable battery.

A battery charging method for a rechargeable battery, the method comprising:

• sensing a current temperature T of the rechargeable battery and measuring a current voltage U of the rechargeable battery;
• comparing the current temperature T of the rechargeable battery with a predetermined first temperature threshold T1 and a predetermined second temperature threshold T2, and comparing the current voltage U of the rechargeable battery with a predetermined first cut-off voltage U1 and a predetermined second cut-off voltage U2, wherein T1<T2 and U1>U2, and then sending a pulse-width modulation (PWM) control signal according to the temperature comparison results and the voltage comparison results;
• and
• charging the rechargeable battery using a first average current I1 when the current temperature T falls into the range T1˜T2;
• and if the current voltage U reaches the first cut-off voltage U1 while the current temperature T remains in the range T1˜T2, stopping charging the rechargeable battery;
• if the current temperature T exceeds the range T1˜T2 before the current voltage U reaches the first cut-off voltage U1, charging the rechargeable battery using a second average current I2, wherein I1>I2;
• and if the current voltage U reaches the second cut-off voltage U2 before the current temperature T exceeds the range T1˜T2, stopping charging the rechargeable battery.