Electric vehicles use electric motors to drive their wheels. They derive some or all of their power from large, rechargeable batteries. All-electric EVs, where the battery is the only power source. Most current (non-luxury) models have a quoted range of 80-120 miles (130-190 km). In practice, range varies according to driving style, terrain and the use of auxiliary equipment such as heating/air conditioning. Electric Vehicle Component
Type of Electric Vehicle
Battery electric vehicles
Battery electric vehicles (BEVs) are powered by electricity stored in large batteries within the vehicles. These batteries are used to power an electric motor, which drives the vehicle. This system allows BEVs to operate with zero emissions at their point of use. Most new BEVs also use ‘regenerative braking’, which allows the electric motor to act as a generator in order to re-capture energy that would normally be lost through heat dissipation and frictional losses – this improves energy efficiency and reduces brake wear. Hybrid electric vehicles
Hybrid electric vehicles (HEVs) are powered by a combination of electricity and either petrol or diesel. The electricity is used only as an intermediate energy storage medium to improve the overall efficiency of the vehicle. They therefore DO NOT need to be plugged in to recharge the battery. This cuts down on the amount of fuel needed, producing fewer emissions and lowering overall fuel costs. As with BEVs, most hybrids also use ‘regenerative braking’, which captures energy from braking to be put back into the battery - this improves energy efficiency and reduces brake wear.
Plug in hybrid electric vehicles
Plug in hybrid electric vehicles (PHEVs) work similarly to conventional hybrid vehicles in that they can operate using their petrol or diesel engine as well as stored electricity for an electric motor. However, they have much larger batteries than conventional HEV and can also be charged from the mains when not in use in order to maximise the range available to the electric motor. As such, they act as a halfway ground between hybrid electric vehicles and battery electric vehicles. In addition, most PHEVs (like BEVs and HEVs) would run a regenerative braking system that puts power from braking back into the battery system. All of this allows PHEVs to be very efficient, and if driven for relatively short distances, they could have zero emissions at the point of use. The benefits of PHEVs are largely similar to those of electric vehicles in that they can, if kept at a high level of charge, operate the majority of the time on electric power, thus reducing their emissions to zero at the point of use. They also have the additional benefits related to electric motors of quiet operation and rapid acceleration. Because of the additional weight of the battery packs, PHEVs tend to be smaller vehicles, usually in the car and small van sector. There are two key types of PHEV. The first can run indefinitely with the petrol/diesel motor providing the car with the energy required for motion. The second is effectively a battery electric vehicle with a small onboard generator to allow the range of the vehicle to be extended.
Electric Vehicle Batteries
Lead acid (Pb-acid)
Lead-acid batteries are the oldest type of rechargeable battery and have a very low energy-to-weight and energy-to-volume ratio. These factors mean that lead acid batteries take up significant amounts of space within vehicles and add significant amounts of weight. However, they can maintain a relatively large power-to-weight ratio and are low cost making them ideal for use in road vehicles. Nickel Cadmium (NiCd)
Nickel Cadmium give the longest cycle life of any currently available battery (over 1,500 cycles) but has low energy density compared to some other battery types. Cadmium is also toxic – a hazard to both humans and animals, so its use (mainly in domestic applications), is being superseded by Li-ion and NiMH...
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