Fuel cells convert fuel directly into electricity and will do so as long as fuel and air are supplied. This eliminates the need for "recharging" but necessitates the carrying of replacement fuel cartridges. These small replaceable and disposable fuel cartridges are installed into the fuel cell of the consumer device on an as needed basis.

In general, these fuel cartridges are comprised of an internal fuel chamber, coupled with an internal valve, control unit, front cover and outer jacket. This is not merely a methanol container since it has a control mechanism. Fuel cartridges incorporate a valve that will open to allow the methanol out only when mated with the consumer electronic equipment. Fuel cartridge valves and connectors will normally be closed and will self-latch if removed from the fuel cell system. This will prevent a partially used cartridge from leaking.

Using fuel supplied by a cartridge, the MFC produces electricity to power the consumer product by reacting oxygen and methanol inside the fuel cell. The fuel is not burned, but rather is converted into electricity through an electrochemical process that splits methanol into protons, electrons, and carbon dioxide at the anode and then combines these protons and electrons with oxygen at the cathode to produce water. MFCs are more accurately referred to as micro generators, not batteries.

In practice, a consumer will insert a small, safe methanol fuel cartridge into a fuel cell power system to provide power, as illustrated in Figure 1. The consumer may choose to carry multiple fuel cartridges or buy additional units when needed, but there will be no need to carry electrical cords or adapters. Additionally, the consumer may remove and replace cartridges while the equipment's system is running.