Abstract: An exciter unit, a battery system including the exciter unit, and a method for determining a battery state of at least one battery cell. The method includes: a. applying a current-exciting signal; b. recording an impedance spectrum of the battery cell; c. determining an evaluation variable on the basis of a measured impedance spectrum. At least one of the amplitude, frequency and relative phase difference of at least one component of the current-exciting signal is modified as a function of the first measured response signal such that a measuring error is minimized, a further measured response signal is determined and evaluated, the value evaluated is used as an evaluation variable, and the battery state variables of the battery cell are determined on the basis of a comparison of at least one diagnostic variable with at least one reference value and/or with at least one further diagnostic variable.

Abstract: An exciter unit, a battery system including the exciter unit, and a method for determining a battery state of at least one battery cell. The method includes: a. applying a current-exciting signal; b. recording an impedance spectrum of the battery cell; c. determining an evaluation variable on the basis of a measured impedance spectrum. At least one of the amplitude, frequency and relative phase difference of at least one component of the current-exciting signal is modified as a function of the first measured response signal such that a measuring error is minimized, a further measured response signal is determined and evaluated, the value evaluated is used as an evaluation variable, and the battery state variables of the battery cell are determined on the basis of a comparison of at least one diagnostic variable with at least one reference value and/or with at least one further diagnostic variable.

Abstract: A diagnostic device for critical changes in batteries having multi-layered structures, a battery system including the diagnostic device, and a method of use thereof. The device determines critical changes relative to a target state in battery cells having a plurality of layers frictionally connected to each other, at least one receiver and, optionally, a transmitter. The receiver receives acoustic plate waves and/or acoustic torsion waves and transmits a corresponding signal to an evaluating unit that evaluates parameters characteristic for an actual state of the battery cell, and compares them to at least one previously defined threshold. Exceeding or falling short of the threshold is evaluated as identification of battery cells having a critical change to the physical properties thereof. A transmitter of the diagnostic device is suitable for exciting the acoustic plate waves or torsion waves in the battery cell having a propagation direction along the layers.