Evaluation of a DC power source can include communication with a voltmeter that is arranged to monitor electrical potential across positive and negative electrodes. The method includes determining a full-cell open-circuit voltage (“OCV”), an associated positive half-cell OCV, and an associated negative half-cell OCV at a start-of-life point of the DC power source. A lithium balance model is executed to determine a plurality of beginning states associated with an electrode alignment of the DC power source. An in-use state for the full-cell OCV is determined. An optimization routine is executed employing the lithium balance model to determine in-use states associated with the electrode alignment of the DC power source based upon the in-use state for the full-cell OCV and the beginning states associated with electrode alignment. A negative-to-positive (“N/P”) ratio is determined based upon the in-use states, and battery life is evaluated based upon the N/P ratio.