Measuring device (5, 6) configured to be connected to first and second terminals (11, 12) of an electric device, such as a battery cell (10, C), and to determine at least one electrical property of the electric device (10, C), wherein the measuring device (5, 6) comprises an impedance measuring arrangement (20, 21) configured to, when the electric device is connected to the first and second terminals (11, 12), connect the electric device (10, C) to a measurement circuit (30, 31), wherein the impedance measuring arrangement (20, 21) is further configured to: - provide a time-varying test current (I test) through the measurement circuit (30, 31); - measure a voltage (U cell) over the electric device (10, C) while the time-varying test current (I test) is provided; and - determine a phase shift and a magnitude ratio between the measured voltage (U cell) and the time-varying test current (I test) in the measurement circuit (30, 31), wherein the time-varying test current (I test) comprises a plurality of superimposed discrete frequencies, wherein said discrete frequencies are distributed over a frequency range and separated from each other so as to avoid frequency overlap due to spread spectrum between adjacent frequencies, characterized in that adjacent frequencies are separated by a minimum frequency separation, f d,min, wherein f d,min ≥ 4*f L =4/T, preferably f d,min ≥ 8*f L =8/T, and more preferably f d,min ≥ 10*f L =10/T, wherein f L =1/T and wherein T is the total time during which the time-varying test current (I test) is provided. wherein the measuring device (5, 6) comprises an impedance measuring arrangement (20, 21) configured to, when the electric device is connected to the first and second terminals (11, 12), connect the electric device (10, C) to a measurement circuit (30, 31), wherein the impedance measuring arrangement (20, 21) is further configured to: - provide a time-varying test current (I test) through the measurement circuit (30, 31); - measure a voltage (U cell) over the electric device (10, C) while the time-varying test current (I test) is provided; and - determine a phase shift and a magnitude ratio between the measured voltage (U cell) and the time-varying test current (I test) in the measurement circuit (30, 31), - provide a time-varying test current (I test) through the measurement circuit (30, 31); - measure a voltage (U cell) over the electric device (10, C) while the time-varying test current (I test) is provided; and - determine a phase shift and a magnitude ratio between the measured voltage (U cell) and the time-varying test current (I test) in the measurement circuit (30, 31), wherein the time-varying test current (I test) comprises a plurality of superimposed discrete frequencies, wherein said discrete frequencies are distributed over a frequency range and separated from each other so as to avoid frequency overlap due to spread spectrum between adjacent frequencies, characterized in that adjacent frequencies are separated by a minimum frequency separation, f d,min, wherein f d,min ≥ 4*f L =4/T, preferably f d,min ≥ 8*f L =8/T, and more preferably f d,min ≥ 10*f L =10/T, wherein f L =1/T and wherein T is the total time during which the time-varying test current (I test) is provided.