Device for measuring isolation resistance (Riso_pos, Riso_neg) of a battery powered system, the device comprising: a positive high-voltage bus connectable to a positive pole of a battery, and additionally connectable to a load, a negative high-voltage bus connectable to a negative pole of the battery, and additionally connectable to the load, a low-voltage ground connection, a first measurement resistance (Rbottom) having a first terminal connected with the low-voltage ground connection, a second measurement resistance (Rtop1) and a third switch connected in series between the positive high-voltage bus, and the second terminal of the first measurement resistance (Rbottom), a third measurement resistance (Rtop2) and a fourth switch connected in series between the negative high-voltage bus, and the second terminal of the first measurement resistance (Rbottom), characterised in that the device further comprises: a first reference resistance and a first switch connected in series between the positive high-voltage bus and the low-voltage ground connection, a second reference resistance and a second switch connected in series between the negative high-voltage bus and the a low-voltage ground connection, a control module adapted for opening and closing the first to the fourth switches (S1, S2, S3, S4) in accordance with a pre-established sequence, and a calculating module adapted for calculating an isolation resistance between the positive high-voltage bus and the low-voltage ground, and an isolation resistance between the negative high-voltage bus and the low-voltage ground, based on voltage measurements at the first measurement resistance (Rbottom), and voltage measurements of the high-voltage battery. a positive high-voltage bus connectable to a positive pole of a battery, and additionally connectable to a load, a negative high-voltage bus connectable to a negative pole of the battery, and additionally connectable to the load, a low-voltage ground connection, a first measurement resistance (Rbottom) having a first terminal connected with the low-voltage ground connection, a second measurement resistance (Rtop1) and a third switch connected in series between the positive high-voltage bus, and the second terminal of the first measurement resistance (Rbottom), a third measurement resistance (Rtop2) and a fourth switch connected in series between the negative high-voltage bus, and the second terminal of the first measurement resistance (Rbottom), characterised in that the device further comprises: a first reference resistance and a first switch connected in series between the positive high-voltage bus and the low-voltage ground connection, a second reference resistance and a second switch connected in series between the negative high-voltage bus and the a low-voltage ground connection, a control module adapted for opening and closing the first to the fourth switches (S1, S2, S3, S4) in accordance with a pre-established sequence, and a calculating module adapted for calculating an isolation resistance between the positive high-voltage bus and the low-voltage ground, and an isolation resistance between the negative high-voltage bus and the low-voltage ground, based on voltage measurements at the first measurement resistance (Rbottom), and voltage measurements of the high-voltage battery. a first reference resistance and a first switch connected in series between the positive high-voltage bus and the low-voltage ground connection, a second reference resistance and a second switch connected in series between the negative high-voltage bus and the a low-voltage ground connection, a control module adapted for opening and closing the first to the fourth switches (S1, S2, S3, S4) in accordance with a pre-established sequence, and a calculating module adapted for calculating an isolation resistance between the positive high-voltage bus and the low-voltage ground, and an isolation resistance between the negative high-voltage bus and the low-voltage ground, based on voltage measurements at the first measurement resistance (Rbottom), and voltage measurements of the high-voltage battery.