From a current measurement circuit, digital samples are received of a current signal that flows through a battery cell within a measurement period. From a voltage measurement circuit, digital samples are received of a voltage signal across the battery cell within the measurement period. First voltage spectral components are generated based on performing a first transform operation on the digital samples of the voltage signal. A current spectrum is generated based on performing a second transform operation on the digital samples of the current signal. Second voltage spectral components are generated based on a first condition of the battery cell before the measurement period and a second condition of the battery cell after the measurement period. A voltage spectrum is including the first voltage spectrum and the second voltage spectrum is generated. An impedance spectrum of the battery cell is generated based on the voltage spectrum and the current spectrum.