Detecting internal short circuits in batteries

A computing system, comprising:

• at least one computer processor;
• and
• a memory storing a program, wherein, when executed by the computer processor, the program is configured to perform an operation comprising:
• identify a flagged cell of a plurality of cells that has a charge imbalance relative to another cell of the plurality of cells, wherein the plurality of cells are coupled in series to power a load;
• selectively coupling a spare cell, initially disconnected from the plurality of cells and the load, to the plurality of cells to compensate for the charge imbalance on the flagged cell during a charge cycle or discharge cycle;
• determining total energy stored in, or drained from, the spare cell during the charge cycle or discharge cycle;
• determining an internal resistance of the flagged cell using the total energy;
• and
• in response to determining that the internal resistance of the flagged cell is below a predefined threshold, discharging the flagged cell and disconnecting the flagged cell from the load.

A method, comprising:

• identify a flagged cell of a plurality of cells that has a charge imbalance relative to another cell of the plurality of cells, wherein the plurality of cells are coupled in series to power a load;
• selectively coupling a spare cell, initially disconnected from the plurality of cells and the load, to the plurality of cells to compensate for the charge imbalance on the flagged cell during a charge cycle or discharge cycle;
• determining total energy stored in, or drained from, the spare cell during the charge cycle or discharge cycle;
• determining an internal resistance of the flagged cell using the total energy;
• and
• in response to determining that the internal resistance of the flagged cell is below a predefined threshold, discharging the flagged cell and disconnecting the flagged cell from the load.