The invention relates to a battery charging device with dynamic capacity-display and charge countdown functions and an application thereof, wherein the device comprises a main controller, a charge control circuit, a voltage collecting module, a current collecting module, a temperature detecting module, a protective circuit module, a working state indicating module, a display module and a power supply converting module used for supplying power to other modules. The main controller is respectively connected with the charge control circuit, the voltage collecting module, the current collecting module, the temperature detecting module, the protective circuit module, the working state indicating module and the display module. The application of the battery charging device is as follows: after being powered and initialized, the main controller dynamically collects parameters of a battery via the voltage collecting module, the current collecting module and the temperature detecting module, calculates the actual capacity of the battery and displays the actual capacity via the display module, and the like. Compared with the prior art, the invention has the advantage of capability of displaying the actual capacity of the battery and the electric quantity charged in the battery, the function of charge countdown estimation, and the like.