DaimlerChrysler engineers first succeeded in making the fuel-cell drive so compact that it would fit into the sandwich-construction floor of the A-Class in 1999, when the 70-kW NECAR 4 came out. Powered by liquid hydrogen, this latest model had a top speed of 145 km/h and could drive for 450 kilometres on a single tank of fuel, while it also had enough room for five people plus luggage. The NECAR 4a was specially built to be used in the fleet test carried out by the "California Fuel Cell Partnership". The drive technology was basically the same as that seen in the NECAR 4 but it had been redeveloped to run on compressed hydrogen, making it much more compact.

source: Mercedes-Benz