Universal charging device and universal charging method thereof

A universal charging device comprising:

• a charger coupled to at least one battery and configured to receive an alternating-current (AC) voltage and convert the AC voltage into a direct-current (DC) charging voltage, wherein the at least one battery has a terminal voltage less than a rated voltage of the at least one battery;
• and
• a power control detector coupled to the at least one battery and the charger, wherein after the charger and the power control detector determines that the at least one battery is a battery to be charged, the charger and the power control detector sequentially perform at least two first charging processes;
• wherein in each of the at least two first charging processes, the power control detector detects the terminal voltage, controls the charger to adjust the DC charging voltage to be larger than the terminal voltage based on the terminal voltage, and controls the charger to generate at least one pulse voltage based on the DC charging voltage, the charger cooperates with the DC charging voltage to charge the at least one battery and respectively generates a direct-current (DC) charging current and at least one pulse current based on the DC charging voltage and the at least one pulse voltage, the charger transmits the DC charging current and the at least one pulse current to the power control detector through the at least one battery until the power control detector determines that the terminal voltage is equal to the DC charging voltage based on the DC charging current, the at least one pulse current flows through the at least one battery to establish a first detected voltage across the at least one battery, when the power control detector determines that the first detected voltage satisfies a charged condition and the terminal voltage is equal to the DC charging voltage, the power control detector controls the charger to convert the DC charging current into a decreasing trickle current until a value of the trickle current is decreased to a triggered current value, and the triggered current value divided by a value of a corresponding the DC charging current is equal to a fixed ratio less than 1 and larger than 0.