This is a hardware circuit that acts like a fuel cell to support testing needs. Fuel cells are similar to batteries but with two major differences: (a) they tend to have higher series impedance than batteries, so the voltage source is "softer," and (b) they do not respond instantly when the external circuit demands more power. The circuit should be able to simulate a variety of fuel cell connections and power levels, either through programming or easy-to-swap hardware equivalents. Both static and dynamic behavior should be included. One specific example: a hardware circuit that acts like a proton-exchange-membrane fuel cell, and has a nominal output voltage of 48 V and current of up to 10 A. The circuit would produce the same static V-I curve as an actual fuel cell stack, and would also show similar time delays during power increases.