An electric bus is a bus that is propelled using electric motors as opposed to an internal combustion engine. Electric buses can store the needed electricity on-board, or be fed continuously from an external source. The majority of buses storing electricity are battery electric buses (which this article mostly deals with), where the electric motor obtains energy from an onboard battery pack, although examples of other storage modes do exist, such as the gyrobus which uses flywheel energy storage. When electricity is not stored on board, it is supplied by contact with outside power sources. For example, overhead wires as in the trolleybus, or with a ground-level power supply, or through inductive charging. As of 2019, 99% of all battery electric buses in the world have been deployed in Mainland China, with more than 421,000 buses on the road, which is 17% of China's total bus fleet. For comparison, the United States had 300, and Europe had 2,250. By 2021, Europe had reached 8,500 electric buses, and China's share of electric buses remained at 98%. History Principles Battery One of the most popular types of electric buses nowadays are battery electric buses. Battery electric buses have the electricity stored on board the vehicle in a battery. , battery electric buses could have a range of over 280 km with just one charge, although extreme temperatures and hills can reduce range. The buses are usually used in cities due to their limited range. City driving involves a great deal of accelerating and braking. Due to that, the battery electric bus is superior to diesel bus as it can recharge most of the kinetic energy back into batteries during braking, which reduces brake wear. The use of electric over diesel propulsion reduces noise and pollution in cities. When operating within a city, it is important to minimize the unloaded and rolling weight of the bus. This can be accomplished by using aluminium as the main construction material. Composite paneling and other lightweight materials can also be used. According to Finnish bus manufacturer Linkker, its fully aluminium bus construction is about 3000 kg lighter than comparably sized modern steel buses, which have a curb weight of 9500 kg. Reducing weight allows for a greater payload and reduces wear to components such as brakes, tires, and joints, achieving cost savings for the operator. Charging Buses may be charged at plug in stations, or on