A chargeable device, comprising: a charging interface; a first charging circuit, coupled to the charging interface and configured to receive voltage and current outputted by an adapter through the charging interface, and to apply the voltage and current outputted by the adapter between a positive terminal and a negative terminal of multiple cells coupled in series and built in the chargeable device to charge the multiple cells directly, when the voltage outputted by the adapter is greater than the total voltage of the multiple cells, wherein the multiple cells comprise a first cell and a second cell; a second charging circuit, comprising a voltage boost circuit coupled between the charging interface and the multiple cells, wherein the voltage boost circuit is configured to convert the voltage outputted from the adapter into a second voltage, the second voltage is applied between the positive terminal and the negative terminal of the multiple cells to charge the multiple cells, when the voltage value outputted from the adapter is less than a total voltage of the multiple cells, and the second voltage value is greater than the total voltage of the multiple cells, characterized in that when the first charging circuit is used, the multiple cells are configured to be charged as fast as a single cell having a capacity C, a charging current I and a voltage V, by using a charging current I/N for the multiple cells, the capacity of each cell of the multiple cells being C/N and the voltage of each cell of the multiple cells being V, where N indicates the number of cells of the multiple cells; and in that the chargeable device further comprises a balance circuit coupled to the multiple cells and configured to balance voltage between the multiple cells by transferring electricity between the first cell and the second cell by capacitive coupling. a charging interface; a first charging circuit, coupled to the charging interface and configured to receive voltage and current outputted by an adapter through the charging interface, and to apply the voltage and current outputted by the adapter between a positive terminal and a negative terminal of multiple cells coupled in series and built in the chargeable device to charge the multiple cells directly, when the voltage outputted by the adapter is greater than the total voltage of the multiple cells, wherein the multiple cells comprise a first cell and a second cell; a second charging circuit, comprising a voltage boost circuit coupled between the charging interface and the multiple cells, wherein the voltage boost circuit is configured to convert the voltage outputted from the adapter into a second voltage, the second voltage is applied between the positive terminal and the negative terminal of the multiple cells to charge the multiple cells, when the voltage value outputted from the adapter is less than a total voltage of the multiple cells, and the second voltage value is greater than the total voltage of the multiple cells, characterized in that when the first charging circuit is used, the multiple cells are configured to be charged as fast as a single cell having a capacity C, a charging current I and a voltage V, by using a charging current I/N for the multiple cells, the capacity of each cell of the multiple cells being C/N and the voltage of each cell of the multiple cells being V, where N indicates the number of cells of the multiple cells; and in that the chargeable device further comprises a balance circuit coupled to the multiple cells and configured to balance voltage between the multiple cells by transferring electricity between the first cell and the second cell by capacitive coupling.