Energy storage cell impedance measuring apparatus, methods and related systems

A method of measuring impedance of an energy storage cell, the method comprising:

• applying, with a sum-of-sinusoids (SOS) current excitation circuit of an impedance measuring device including differential current sources configured to isolate a ground terminal of the differential current sources from a positive terminal and a negative terminal of an energy storage cell, an SOS signal to the energy storage cell, the SOS signal comprising a sum of sinusoidal current signals, each of the sinusoidal current signals oscillating at a different one of a plurality of different frequencies;
• measuring an electrical signal at the positive terminal and the negative terminal of the energy storage cell with at least one signal measuring module of the impedance measuring device coupled to the positive terminal and the negative terminal;
• and
• computing, with an impedance computation module of the impedance measuring device, an impedance of the energy storage cell at each of the plurality of different frequencies using the measured electrical signal.

An energy storage cell impedance measuring circuit, comprising:

• differential current sources, including:
• a push current source configured to operably couple to a positive terminal of an energy storage cell;
• a pull current source configured to operably couple to a negative terminal of the energy storage cell;
• and
• a ground terminal of the differential current sources operably coupled between the push current source and the pull current source;
• and
• a high voltage buffer operably coupled to at least one of the push current source and the pull current source and configured to isolate the at least one of the push current source and the pull current source from a direct current voltage provided by the energy storage cell;
• wherein the differential current source is configured to apply a sum-of-sinusoids (SOS) signal through the positive terminal and the negative terminal of the energy storage cell.

An impedance measuring system, comprising:

• one or more energy storage cells;
• and
• an energy storage cell impedance measuring system operably coupled to the one or more energy storage cells, the energy storage cell impedance measuring system including:
• sum-of-sinusoids (SOS) current excitation circuitry including differential current sources, the SOS current excitation circuitry configured to apply SOS signals to the one or more energy storage cells, the SOS signals including sums of a plurality of sinusoidal current signals, each of the plurality of sinusoidal current signals including a different one of a plurality of different frequencies;
• and
• control circuitry operably coupled to the SOS current excitation circuit and the one or more energy storage cells, the control circuitry configured to:
• control the SOS current excitation circuitry;
• measure electrical signals at terminals of the one or more energy storage cells responsive to the SOS signals;
• and
• compute impedances of the energy storage cells.