Abstract: A digital system or device includes a battery pack as an exemplary functional subunit. In a warranty case determined by an electrical load test for determining its actual charge capacity, a battery check program initializes, via the operating system and an underlying printer, a printout of a warranty certificate. This certificate form, in particular, contains a UID of the underlying battery pack gathered from a ROM implemented in the battery pack. Before generating the printout of the certificate, the UID gathered from the ROM is coded e.g. by the battery check program and only the coded UID is printed. The printout of the warranty certificate thereafter will be delivered to the warranty service provider by the user. After having received the delivered warranty certificate and having checked validity of the user's warranty claim by means of the coded UID the warranty service provider sends a replacement battery pack back to the user.