Battery charging device and method capable of detecting battery access state

The application discloses a battery charging device and method capable of detecting a battery access state. The concrete implementation mode of the device comprises a voltage transformation circuit for transforming an inputted AC or DC into a DC voltage needed by the battery charging; a switch unit connected with the voltage transformation circuit and a battery; and a control unit for adjusting change of the DC voltage value outputted by the voltage transformation circuit, and detecting the relationship between the change of the voltage value outputted by the switch unit and the change of the DC voltage value outputted by the voltage transformation circuit and a current flowing through the switch unit. If the change of the voltage value outputted by the switch unit and the change of the DC voltage value outputted by the voltage transformation circuit are not same, and the current flowing through the switch unit is greater than zero, the control unit controls the switch unit to conduct to charge the battery. A