An electrical device, comprising: a battery cell; a voltage sensor operatively coupled to the battery cell in order to measure a voltage level of the battery cell; a current sensor operatively coupled to the battery cell in order to measure an amount of current drawn from the battery cell; and a battery management system including a controller in electrical communication with the voltage sensor and the current sensor, the controller being configured to execute a program stored in the controller to: (i) receive a plurality of voltage values from the voltage sensor, (ii) receive a plurality of current values from the current sensor, wherein each current value is associated with one of the voltage values, (iii) calculate a plurality of total discharge values, wherein each total discharge value is associated with one of the current values, (iv) calculate a differential voltage curve using the voltage values and the total discharge values, (v) determine a first differential voltage point and a second differential voltage point on the differential voltage curve wherein each of the first differential voltage point and second differential voltage point is at a local peak, and (vi) calculate a state of health of the battery cell using the first differential voltage point, the second differential voltage point, and a characteristic curve of a reference battery electrode of a reference battery cell, wherein the reference battery cell includes a second reference battery electrode not exhibiting distinct phase transitions during a charge - discharge cycle. a battery cell; a voltage sensor operatively coupled to the battery cell in order to measure a voltage level of the battery cell; a current sensor operatively coupled to the battery cell in order to measure an amount of current drawn from the battery cell; and a battery management system including a controller in electrical communication with the voltage sensor and the current sensor, the controller being configured to execute a program stored in the controller to: (i) receive a plurality of voltage values from the voltage sensor, (ii) receive a plurality of current values from the current sensor, (i) receive a plurality of voltage values from the voltage sensor, (ii) receive a plurality of current values from the current sensor, wherein each current value is associated with one of the voltage values, (iii) calculate a plurality of total discharge values, wherein each total discharge value is associated with one of the current values, (iv) calculate a differential voltage curve using the voltage values and the total discharge values, (v) determine a first differential voltage point and a second differential voltage point on the differential voltage curve wherein each of the first differential voltage point and second differential voltage point is at a local peak, and (vi) calculate a state of health of the battery cell using the first differential voltage point, the second differential voltage point, and a characteristic curve of a reference battery electrode of a reference battery cell, wherein the reference battery cell includes a second reference battery electrode not exhibiting distinct phase transitions during a charge - discharge cycle. (iii) calculate a plurality of total discharge values, wherein each total discharge value is associated with one of the current values, (iv) calculate a differential voltage curve using the voltage values and the total discharge values, (v) determine a first differential voltage point and a second differential voltage point on the differential voltage curve wherein each of the first differential voltage point and second differential voltage point is at a local peak, and (vi) calculate a state of health of the battery cell using the first differential voltage point, the second differential voltage point, and a characteristic curve of a reference battery electrode of a reference battery cell, wherein the reference battery cell includes a second reference battery electrode not exhibiting distinct phase transitions during a charge - discharge cycle.