1. A method wherein at least one act of the method is performed by a processor, the method comprising: developing a mechanistic level model of an electrochemical cell to determine performance fade characteristics of the electrochemical cell using: first constant-current pulses applied to the electrochemical cell at a first aging period and at three or more current values bracketing a first exchange current density; and second constant-current pulses applied to the electrochemical cell at a second aging period and at three or more current values bracketing the second exchange current density; and analyzing the mechanistic level model to estimate performance fade characteristics over aging of a similar electrochemical cell.