Abstract: The present invention provides a method for determining voltage loss in an electrical device. The method includes the steps of obtaining an array A of voltage values corresponding to at least one current interrupt measurement at current In, wherein In corresponds to current values I1, I2, . . . , In, wherein subscript n is at least 3; forming an array D of difference values using a difference of the array A over an elapsed time; processing the difference values of the array D to obtain Vn; determining Vn for each In to form an array V of Vn; and calculating a resistance, R, using the array V, thereby determining voltage loss in the electrical device.