Method for Monitoring Battery Cells of a Primary On-Board Electrical System Battery, On-Board Electrical System and Motor Vehicle

A method for monitoring battery cells of a primary on-board electrical system battery of a motor vehicle by galvanostatic impedance spectroscopy is provided. An AC signal having alternating currents of different frequencies is impressed onto the battery cells as an excitation signal, cell voltage signals of the battery cells are detected as frequency-dependent response signals to the excitation signal, impedance spectra of the battery cells are determined depending on the excitation signal and the response signals, and the primary on-board electrical system battery is divided into at least two subsections each having at least one battery cell in order to provide the excitation signal. The primary on-board electrical system battery is electrically connected to a secondary on-board electrical system battery of the motor vehicle.