Method of testing an electrochemical device
Methods and associated apparatus for testing an electrochemical device, such as a fuel cell. A first method involves charging the fuel cell during a charge period; discharging the fuel cell during a discharge period; and monitoring the response of the fuel cell during at least part of the discharge period or the open-circuit response of the fuel cell. Another method involves testing the fuel cell when the fuel cell is in a passive state in which substantially no electrochemical reactions are taking place in the fuel cell. simultaneously applying a stimulus to all of the devices, and independently monitoring the response of each of the devices to the stimulus. Further methods involve obtaining test data from a device being tested; obtaining equivalent circuit values; calculating sets of simulation data for each equivalent circuit value; comparing sets of simulation data with the test data; and selecting one of the equivalent circuit values based on the comparison. This method allows all circuit parameters of each cell in a stack to be obtained from only one quick test.
1. A method of testing a fuel cell, the method including charging the fuel cell during a charge period; discharging the fuel cell during a discharge period; monitoring the response of the fuel cell during at least part of the discharge period; and calculating one or more equivalent circuit values in accordance with the monitored response of the passive fuel cell, wherein the one or more equivalent circuit values include a first resistance value as a first component in an equivalent circuit model that represents electrical resistance between each fuel cell and fixed first capacitance value representing a capacitance across terminals of the fuel cell.
2. A method according to claim 1 wherein the response of the fuel cell is monitored by monitoring a step change in the voltage across the fuel cell during the at least part of the discharge period.
3. A method according to claim 1 further including making the fuel cell open-circuit after the charge period, and monitoring the open-circuit response of the fuel cell.
4. A method according to claim 1 wherein the fuel cell is discharged during the at least part of the discharge period through one or more passive test components.
5. A method according to claim 3 wherein the open-circuit response of the fuel cell is monitored by monitoring the rate of change of voltage across the fuel cell.
6. Apparatus for testing an electrochemical device, the apparatus being programmed to perform a method according to claim 1 .
7. An apparatus configured to perform the method of claim 1 .
8. A method according to claim 1 wherein the one or more equivalent circuit values further include a second resistance value that represents a resistance of a membrane of the fuel cell, a third resistance value that represents a resistance to the movement of ions in the membrane, and a second capacitance value representing a dielectric effect of the membrane.
9. A method according to claim 1 wherein the equivalent circuit values further include a second resistance value that represents a resistance of a membrane of the fuel cell and the first capacitance value is in parallel with the second resistance value.
10. A method according to claim 1 wherein the equivalent circuit values further include a third resistance value in series with a second capacitance value, where the third resistance value represents a resistance to the movement of ions in the membrane and the second capacitance value represents the dielectric effect of the membrane, wherein the first capacitance value is in parallel with a series arrangement of the third resistance value and second capacitance value.