Abstract: The invention relates to a device, in particular a power bank (20), comprising: at least one port (24) for connecting the device to a terminal (10); at least one memory (22) for storing useful data; at least one rechargeable battery (26) for supplying a charging current to the terminal; at least one computer unit (21); wherein the computer unit (21) is configured, in particular programmed, a) to send an authentication request (Req1) to the terminal (10); and b) to receive a response (Res1) to the authentication request (Req1), wherein the charging current is interrupted within a charging interval (L1, L2, L3) or the charging interval (L1, L2, L3) is not initialized if successful authentication is not carried out by means of the authentication request and response.