Some FCV's employ a battery to store electricity produced from regenerative braking or from the fuel cell stack. The stored electricity can be uses to help power the electric motor or other electicial devices.
The Power Controller Unit (PCU) contains sophisticated electrons that manage the production and storage of electricity.
An FCV can be powered by one or several electric motors, some use a separate electric motor for each wheel. These motors produce enough power to propel FCV's at speeds comparable to those of conventional vehicles.
FCVs like the one above use pure hydrogen as fuel, stored onboard the vehicle in highly pressurized tanks. Other FCVs are designed to use a liquid fuel such as gasoline or methanol, which is stored in a conventional, non-pressurized tank. FCVs using these fuels also need a reformer-a fuel processor that breaks down the fuel into hydrogen for the fuel cell, carbon dioxide, and water. Although this process generates carbon dioxide, it produces much less than the amount generated by gasoline-powered vehicles.
Fuel cell vehicles can also be equipped with regenerative braking systems that capture the energy usually lost during braking and store it in an up-sized battery.
Dept. of Energy