Abstract: A cell monitoring device is provided for use with an electric battery cell while the cell is electrically coupled to the device and undergoing maturation in a controlled environment, after being initially charged. The device repeatedly obtains voltage measurements of the electric battery cell at a sampling rate, calculates a rate of change for voltage based on the voltage measurements relative to the sampling rate, and evaluates the obtained voltage measurements and the calculated rate of change, using a model comprising at least one voltage-dependent function and defined for the cell according to that cell's manufacturing specification, to determine whether the cell deviated from the manufacturing specification or reached a predetermined stage of maturation for removing the cell from the controlled environment. Upon determining that the electric battery cell deviated from the manufacturing specification or reached the predetermined stage of maturation, the device generates a corresponding alert.