The possibility of the use of impedance spectroscopy using an impulse method of step current change and recording voltage change in during time at the terminals of a cell with subsequent Fourier transform of the input signal and the response to it to assess the current state of Li-cell. It is proposed use of current pre-impulse in order to minimize the influence of passive film. It is substantiated an algorithm based on the measurements of impedance phase for determining of residual capacity.
