Battery module with active cell balancing using energy storage element and two tiers of switches

A method for actively balancing a state of charge of a string of battery cells in a battery module having a first end and a second end, each respective battery cell of the string having diametrically-opposed positive and negative cell tabs, the method comprising:

• respectively positioning a cell sense board (CSB) of an active cell balancing circuit at each of the first end and the second end of the battery module, the active cell balancing circuit including energy storage elements and a plurality of voltage sensors, each respective one of the voltage sensors being respectively located between a different pair of adjacent battery cells of the string, the active cell balancing circuit further including a first tier of switches and a second tier of switches located at each of the first end and the second end of the battery module, wherein the switches of the first tier of switches are single-pole switches and the switches of the second tier of switches are double-pole switches;
• receiving measured voltages from the voltage sensors, via a battery controller, wherein the measured voltages are indicative of an electric potential between each of the different pairs of adjacent battery cells;
• responsive to the measured voltages, using the battery controller to command the first tier of switches of the first end or the second end to close or open and thereby respectively connect or disconnect designated pairs of the battery cells to a corresponding one of the second tier of switches;
• and
• commanding the second tier of switches to selectively connect or disconnect the designated pairs of battery cells to one of the energy storage elements, via the battery controller, such that energy is shuttled between the designated pairs of battery cells and balance a state of charge of the string of battery cells.

An active cell balancing circuit for use with a battery module, the battery module having a first end and a second end and a string of battery cells, each respective battery cell of the string of battery cells having diametrically-opposed positive and negative cell tabs, the active cell balancing circuit comprising:

• a first energy storage element and a second energy storage element positioned at the first end and the second end, respectively, wherein the first energy storage element and second energy storage elements are first and second inductors, respectively;
• a plurality of voltage sensors, each respective voltage sensor being respectively located between a different pair of adjacent battery cells of the string;
• a first tier of switches and a second tier of switches located at the first end of the battery module, the first tier of switches of the first end and the second end selectively connecting or disconnecting designated pairs of the battery cells to a corresponding one of the second tier of switches, and the second tier of switches selectively connecting or disconnecting the respective pairs of battery cells, via a corresponding one of the first tier of switches, to one of the first energy storage element or the second energy storage element to shuttle energy between the designated pairs of battery cells and thereby balance a state of charge of the string of battery cells.