Abstract: An electrochemical flow type battery may include at least one electrode and a separator. The electrode may include carbon fibers and/or carbon particles, and has an internal surface area density of at least 1 m2/g. The separator may separate an anode side and a cathode side of the battery. A flat surface of the electrode directly contacts a surface of the separator.

Abstract: Species detection techniques are described based on measurement of a dynamic response to an external stimulus. One embodiment includes a voltage stimulus applied to a polymer electrolyte fuel cell (PEFC), with the response to said stimulus used to measure CO concentration on the anode catalyst. The principles of symbolic dynamics, finite state machines or a simplified peak response-to-asymptotic value measurement can be used to achieve a high degree of precision for measuring CO concentrations. Using the techniques of the present invention, CO poisoning of a fuel cell can be monitored and diagnosed before reaching a critical condition, thereby allowing early implementation of mitigation or graceful degradation strategies.