A technique for fast impedance measurement in the time domain is presented. It is based on the Fourier transformation and includes various improvements compared to previous work in the literature. Namely, it minimizes the influence of spectral leakage and aliasing and reduces noise. This is proved by the theoretical error estimate for different model systems. The technique is independent of the excitation signal and is demonstrated by a voltage step. Measurement results for a commercial Li-ion cell are presented and compared with results obtained by electrochemical impedance spectroscopy. Finally, a combination of the two techniques is proposed to cover a wide frequency range in minimum measurement time for the characterization of electrochemical systems.