There are many different types and sizes of electric vehicle. However, in nearly all cases the battery is a key compment. In the classic electrical vehicle the battery is the only energy store, and the component with the highest cost, weight and volume. In hibrid vehicles thebattery, which must continually accept and give out electrical energy, is also a key component of the highest importance. Some fuel cell vehicles have been made which have batteries that 2are no larger than those normally fitted to internal combustion engine cars, but it is probable that most early FC powered vehicles will have quite large batteries and work in hybrid fuel cell/battery mode. In short, a good understanding of battery technology and performance is vital to anyone involved with electric vehicles.