INDUCTIVE CELL BALANCING
An energy storage cell arrangement has a shared inductor ( 60 ). A switching arrangement ( 62 ) is controllable such that it is able to couple one side of the inductor to any one of a first set of cell terminals, and to couple the other side of the inductor to any one of a second set of cell terminals, wherein the first and second sets of cell terminals together comprise all cell terminals of the series arrangement. In this way, energy can be transferred between cells in a configurable way, using a shared inductor.
1 . An energy storage cell arrangement comprising:
a series arrangement of cells, comprising at least two cells;
an inductor; and
a switching arrangement,
wherein the switching arrangement is controllable such that it is able to couple one side of the inductor to any one of a first set of cell terminals, and to couple the other side of the inductor to any one of a second set of cell terminals, wherein the first and second sets of cell terminals together comprise all cell terminals of the series arrangement.
2 . An arrangement as claimed in claim 1 , wherein the cell terminals of the first set are all different to those of the second set.
3 . An arrangement as claimed in claim 2 , wherein the switching arrangement comprises a respective switch between each cell terminal and one of the inductor terminals, and a respective diode in parallel with each switch.
4 . An arrangement as claimed in claim 2 , wherein the switching arrangement comprises a respective switch between each cell terminal and one of the inductor terminals, a respective diode between each inductor terminal and the top cell terminal and a respective diode between each inductor terminal and the bottom cell terminal.
5 . An arrangement as claimed in claim 2 , wherein the switching arrangement comprises a first three-way switch at the input to one of the inductor terminals, a second three-way switch at the input to the other of the inductor terminals, and a respective switch between each cell terminal and both of the three-way switches, wherein the three way switches are controlled such that each respective switch is connected to one or other of the inductor terminals.
6 . An arrangement as claimed in claim 5 , wherein the switching arrangement comprises a first diode between the one inductor terminal and the top cell terminal and a second diode between the other inductor terminal and the bottom cell terminal.
7 . An arrangement as claimed in claim 1 , wherein the cell terminals of the first set include all cell terminals and the cell terminals of the second set include all cell terminals.
8 . An arrangement as claimed in claim 7 , wherein the switching arrangement comprises a respective switch between each cell terminal and one of the inductor terminals, and a respective switch between each cell terminal and the other of the inductor terminals, and a respective diode between the one inductor terminal and the top cell terminal and a respective diode between the other inductor terminal and the bottom cell terminal.
9 . An arrangement as claimed in claim 8 , wherein the switching arrangement comprises a respective diode between each inductor terminal and the top cell terminal and a respective diode between each inductor terminal and the bottom cell terminal.
10 . An arrangement as claimed in claim 1 , further comprising a controller adapted to:
identify a cell or cells from which charge is to be removed;
control the switching arrangement to transfer energy from the identified cell or cells to the inductor; and
control the switching arrangement to transfer energy from the inductor to another cell or cells.
11 . An electric vehicle battery cell pack comprising one or more battery cell arrangements as claimed in claim 1 .
12 . A method of performing cell balancing within an energy storage cell arrangement which comprises a series arrangement of cells, comprising at least two cells and an inductor shared between all cells, the method comprising
identifying a cell or cells from which charge is to be removed;
controlling a switching arrangement to transfer energy from the identified cell or cells to the shared inductor; and
controlling the switching arrangement to transfer energy from the inductor to another cell or cells.
13 . The method of claim 12 , wherein controlling the switching arrangement comprises coupling one side of the inductor to a selected one of a first set of cell terminals, and coupling the other side of the inductor to a selected one of a second set of cell terminals.
14 . The method of claim 12 , wherein controlling the switching arrangement to transfer energy from the identified cell or cells to the shared inductor comprises passing a current through the switches and the inductor, and controlling the switching arrangement to transfer energy from the inductor to another cell or cells comprises passing current through a diode arrangement.