A method of developing an optimum a lithium battery charging algorithm is conducted by providing a salt dissolved in solvent permitting lithium ions to leave a cathode in large format battery cells. Charge and discharge are then measured under different C-rate conditions. Using the cathode material phase transformations to ascertain a differential curve, peaks in the differential curve are observed with all data plotted against dV/dt and V, where V represents voltage and t represents time. Areas in voltage ranges are then observed where the rate of increase is higher than in other areas. By varying the charging current, an optimum charging voltage can be ascertained and maintained.