A measurement system for thermodynamically evaluating an electrochemical cell having electrodes; said system comprising: a means for measuring open circuit voltages of said electrochemical cell as a function of time; a composition controller electrically connected to said electrochemical cell for establishing selected electrochemical cell compositions, said composition controller capable of establishing a plurality of said selected compositions; a temperature controller in thermal contact with said electrochemical cell for establishing a plurality of selected electrochemical cell temperatures for each of said selected compositions, thereby establishing a plurality of selected electrochemical cell temperature and composition combinations; and an open circuit voltage analyzer for receiving open circuit voltage measurements as a function of time from said a means for measuring open circuit voltages and for identifying open circuit voltages for thermochemically stabilized conditions of said electrochemical cell for said selected electrochemical cell temperature and composition combinations, characterized in that said open circuit voltage analyzer is a processor capable of executing an algorithm which calculates observed rates of change in open circuit voltage per unit time for a selected electrochemical cell temperature and composition combination using said open circuit voltage measurements as a function of time received from said means of measuring open circuit voltage, wherein said algorithm compares absolute values of said observed rates of change in open circuit voltage per unit time for said selected electrochemical cell temperature and composition combination to a threshold rate of change in open circuit voltage per unit time, and wherein said algorithm identifies an open circuit voltage equal to said open circuit voltage of said electrochemical cell for thermochemically stabilized conditions for said selected electrochemical cell temperature and composition combination when the absolute value of the observed rate of change in open circuit voltage per unit time is equal to or less than said threshold rate of change in open circuit voltage per unit time; wherein said threshold rate of change in open circuit voltage as a function of time is equal to or less than 1 mV h -1. a means for measuring open circuit voltages of said electrochemical cell as a function of time; a composition controller electrically connected to said electrochemical cell for establishing selected electrochemical cell compositions, said composition controller capable of establishing a plurality of said selected compositions; a temperature controller in thermal contact with said electrochemical cell for establishing a plurality of selected electrochemical cell temperatures for each of said selected compositions, thereby establishing a plurality of selected electrochemical cell temperature and composition combinations; and an open circuit voltage analyzer for receiving open circuit voltage measurements as a function of time from said a means for measuring open circuit voltages and for identifying open circuit voltages for thermochemically stabilized conditions of said electrochemical cell for said selected electrochemical cell temperature and composition combinations, characterized in that said open circuit voltage analyzer is a processor capable of executing an algorithm which calculates observed rates of change in open circuit voltage per unit time for a selected electrochemical cell temperature and composition combination using said open circuit voltage measurements as a function of time received from said means of measuring open circuit voltage, wherein said algorithm compares absolute values of said observed rates of change in open circuit voltage per unit time for said selected electrochemical cell temperature and composition combination to a threshold rate of change in open circuit voltage per unit time, and wherein said algorithm identifies an open circuit voltage equal to said open circuit voltage of said electrochemical cell for thermochemically stabilized conditions for said selected electrochemical cell temperature and composition combination when the absolute value of the observed rate of change in open circuit voltage per unit time is equal to or less than said threshold rate of change in open circuit voltage per unit time; wherein said threshold rate of change in open circuit voltage as a function of time is equal to or less than 1 mV h -1.