Method of charging battery and system using the same

A system of charging a battery, comprising:

• a charging circuit, configured to comprise a switching unit, wherein the switching unit is coupled to the battery;
• a detecting circuit, configured to be coupled to the battery, to detect a terminal voltage of the battery and output a sampling signal reflecting the terminal voltage;
• and
• a control circuit, configured to receive the sampling signal to output a control signal to the charging circuit, so as to control the switching unit to charge the battery, wherein,
• under a control of the control signal, the switching unit performs a step of quick charging when the terminal voltage is less than a voltage threshold, wherein the step of quick charging includes:
• calculating a rising rate of the terminal voltage, comparing the rising rate with a rising rate reference value and producing a comparison result, and controlling conduction time of the switching unit according to the comparison result, thereby controlling the terminal voltage, and
• the switching unit further performs a step of low current floating charging when the terminal voltage is not less than the voltage threshold, wherein the step of low current floating charging includes:
• intermittently charging the battery by a predetermined floating charging period, calculating a falling rate of the terminal voltage, comparing the falling rate with a falling rate reference value and producing a comparison result, and controlling the conduction time of the switching unit according to the comparison result, thereby controlling the terminal voltage, in a first time duration of the floating charging period, and keeping the switching unit being turned off, thereby suspending charging, in a second time duration of the floating charging period.