Testing of a vehicle battery in a state removed from a vehicle, using a testing device that is fashioned for testing the vehicle battery installed in the vehicle using an on-board diagnostic interface of the vehicle. The device has: an interface to which a plug of the testing device can be connected, the plug being for connection to the on-board diagnostic interface of the vehicle; an electrical connecting device via which at least one electrical vehicle battery terminal of the vehicle battery is connectable to the device; and an adapter device by which signals receivable from the electrical vehicle battery terminal of the vehicle battery via the connecting device are conductible to the interface in such a way that the signals at the interface for the testing device are capable of being tested via the plug corresponding to a configuration of the on-board diagnostic interface of the vehicle.