the two measuring paths 140 150 of the measuring device 130 as soon as at least one second voltage is applicable to the measuring device 130 via the further relays 71 72 i e as soon as a second voltage is respectively applicable via the further relays 71 72 between at least one high voltage terminal 21 22 of the two high voltage terminals 21 22 of the battery 20 and the housing potential 25 which second voltage lies outside a provided measuring range of the measuring device 130 and consequently has a magnitude which exceeds a maximum magnitude the two relays 140 150 on the measuring paths 140 150 are automatically opened by the monitoring circuit 230 to this end in the conduct of a dielectric withstand test via the further relays 71 72 a test voltage u00b1 vt 1 which is applicable between at least one high voltage terminal 21 22 of the two high voltage terminals 21 22 of the battery 20 and the housing potential 25 and defined by a ramp function is varied until a desired high voltage is achieved such that the measuring device 130 even in consideration of a respective time lag on the two relays 145 155 of the two measuring paths 140 150 can be promptly galvanically separated from the battery 20 or from the high voltage network 70 by means of the monitoring circuit 230 to this end the monitoring circuit 230 is configured for the detection of test voltages u00b1 vt 1 applicable in either direction of polarity and for the comparison.