Battery monitoring system

A battery monitoring system, comprising:

• a current sensor electrically coupled in series with a battery cell;
• a voltage sensor electrically coupled in parallel to the battery cell;
• a microcontroller obtaining cell current values of a cell current flowing through the battery cell from the current sensor at a first update frequency of M times per second;
• the microcontroller obtaining cell voltage values of the battery cell from the voltage sensor, in parallel to the obtaining of the cell current values, with respect to electrical ground, at a second update frequency of N times per second, wherein M>=N;
• at a third update frequency of R times per second, where R<M and R<N,
• the microcontroller determining a rate of change of cell current utilizing two cell current values of the cell current values;
• the microcontroller determining a rate of change of cell voltage utilizing two cell voltage values of the cell voltage values;
• and
• the microcontroller determining a filtered ohmic resistance value based on the rate of change of cell voltage, the rate of change of cell current, and a prior filtered ohmic resistance value, if a numerical sign of the rate of change of cell voltage being identical to a numerical sign of the rate of change of cell current, and the rate of change of cell voltage being less than or equal to an upper threshold of allowable rates of cell voltage change, and the rate of change of cell voltage being greater than or equal to a lower threshold of allowable rates of cell voltage change.