Electric vehicles (EVs) are the future of the automotive industry, but they’re nothing new. The first electric cars were introduced in the 1880s. Eventually, EV technology was replaced by what became more affordable gasoline-powered cars and the internal combustion (IC) engine.
Today, EVs are recognized as a critical means of “greener” transportation, given the challenges of climate change. As crude oil is a finite resource, EVs have become one fundamental way the automotive industry can guarantee a future.
The U.S. expects half of its vehicles on the road to be electric by 2030. Europe is ahead of the game and planning to go all-green by 2030, which includes the full electrification of its vehicles. In fact, fossil-fuel vehicles are expected to be fully banned in Europe from 2035 onwards. India has already tabled a bill to scrap diesel cars in 15 years and petrol cars in 20 years.
EVs are wholly or partially propelled by electric motors driven by the energy stored in rechargeable batteries. There are five main variants of electric vehicles that are loosely grouped under the term EV.
Electric vehicles can be broadly classified into five variants.
1. Battery electric vehicle (BEV)
2. Fuel-cell electric vehicle (FCEV)
3. Plug-in hybrid electric vehicle (PHEV)
4. Hybrid electric vehicle (HEV)
5. Range extender hybrid electric vehicle (RE-HEV)
In another scheme of classification, HEV and PHEV vehicles are considered sub-classes of hybrid vehicles. They can be classified as follows.
1. Battery electric vehicle (BEV)
2. Fuel-cell electric vehicle (FCEV)
3. Hybrid electric vehicle (HEV and PHEV)
In many countries, REHEVs are considered a sub-class of PHEVs.
Battery electric vehicles (BEVs)
BEVs are all-electric vehicles that rely on no direct fossil fuel for power. It’s entirely run on a battery-powered electric drivetrain. One or two electric motors may propel the vehicle or an integrated hub of four electric motors.
An electronic motor controller controls all of the motors and is responsible for speed change, torque, braking, slip differential, and more. The transmission is fully automatic as no internal combustion (IC) horsepower is used in BEVs. BEVs are one ofthe most efficient electric vehicles that are 100% green.
The main components used in BEV are electric motors, electronic motor controllers, drive trains, inverters, and batteries. These vehicles are capable of fast charging and L2 charging. L2 chargers operate at 208 to 240 V and output between 3 to 19 kW of AC power. For comparison, a Level 1 charger will typically get four miles of driving range per hour of charge and a Level 2 charger will get an average of 32 miles of range per hour of charge.
BEVs are charged by plugging the vehicle into a home or public charger directly connected to a grid or battery energy storage system (BESS). The electrical energy stored in the DC battery is converted to AC via an inverter. The electronic motor controller senses the accelerometer’s acceleration and adjusts the AC power frequency accordingly. The AC power (with a frequency based on the acceleration) is transferred to the motors or integrated hub.
The motors are attached to wheels via the gear assembly. When brakes are applied, the motors perform as alternators, redirecting power to the battery pack and decelerating the vehicle. The driving range of BEVs ranges from 240 to 600km.
Fuel-cell electric vehicles (FCEVs)
Unlike BEVs that require charging from a grid or BESS, fuel-cell electric vehicles carry their own electricity generator. These vehicles are powered by a hydrogen fuel cell, creating zero emissions. They emit no tailpipe pollution but water.
FCEVs have a hydrogen tank and fuel cells. The electricity is generated by a chemical reaction between hydrogen from the tank and oxygen from the air, which leaves water as the by-product. The hydrogen tank must be refilled once exhausted.
The main components of an FCEV are:
- Electric motors
- An electronic motor controller
- An electric converter
- A hydrogen storage tank
- A fuel cell stack
- A battery management system (BMS)
The electricity produced by the fuel cell is stored in the battery pack, which is used to drive the electric motors. A BMS stores, converts, regulates, and transmits the electric power.
FCEVs have an advantage over BEVs, offering a continuous current delivery to the battery pack as the electricity is produced onboard. FCEVs also require no frequent charging cycles.
However, they are less popular than BEVs because FCEVs have a complex design that demands regular maintenance. One con is the compressor noise, which may vary from model to model.
FCEVs offer a range of 600 to 640km. The current models of FCEVs available in the USA and Europe are Hyundai Nexo and Toyota Mirai. The FCEVs available in India include Hyundai Tucson FCEV, Hyundai Nexo, Toyota Mirai, and Honda Clarity.
Plug-in hybrid electric vehicles (PHEVs)
PHEVs are hybrid cars, typically powered by an IC engine and an electric motor system. These vehicles have a smaller, low-voltage battery pack compared to all-electric cars.
The battery pack in PHEVs is charged by a home or public charger connected to the grid or BESS, just like BEVs. The vehicle starts in all-electric mode and runs on electricity until the battery is depleted. Once drained, the IC engine kicks in and takes over. The vehicle’s electric mode has a short range, between 20 and 50km.
The primary components of a PHEV are the IC engine, fuel tank, electric motors, battery pack, inverter, and electronic motor controller. The transmission system is connected to both auxiliary electric motors and the conventional IC engine. However, it’s never drive by both simultaneously.
The conventional IC engine could be petrol gasoline, diesel, or bio-diesel. In many PHEV models, the electric motors are used to power the rear wheels, while the IC engine is used to power the front wheels.
Whenever the brakes are applied, the electric motors act as alternators, redirecting power to the battery pack and decelerating the car.
PHEVs do not rely on charging, so these vehicles can run all-electric for daily commuting over a shorter range with a regular charging cycle. They can also be used for longer distances and automatically switch to engine mode when the battery is depleted. But this means that PHEVs are not emission-free.
Of course, when running on the battery, they produce zero emissions. But this changes when the engine is activated, producing pollution like any other gas-driven car.
Nearly every major automotive brand offers a PHEV, including Ford, Toyota, Kia, Chrysler, Hyundai, Subaru, Mini Cooper, Jeep, and others.
Hybrid electric vehicles (HEV)
The HEVs are also referred to as parallel or standard hybrids. The electric motors and battery packs in these vehicles are only used to assist the IC engine. The car is mainly driven by an engine that could be gasoline, petrol, or diesel.
The auxiliary electric motors are linked to the main transmission so electric motors and engines drive the car simultaneously. The battery pack is not charged externally, so there’s no need to charge the vehicle. Instead, the batteries are charged by the IC engine, the wheels’ motion, and regenerative braking. The battery pack provides a boost and between 10 to 35km of additional mileage. These vehicles produce emissions because there’s no sole mode of electric operation.
As the battery pack is much smaller in HEVs compared to PHEVs and BEVs, these vehicles only run a few kilometers in electric mode. Most of today’s top automotive brands offer HEV options.
In mild-hybrid HEVs, the electric motors are typically used to power the transmission where the engine is inefficient — such as when the vehicle accelerates from a stop.
Otherwise, the IC engine powers the tires and is required to run the vehicle. The battery pack is recharged from the engine, and regenerative braking only assists the engine, acting simultaneously on the transmission to tip up some mileage. A mild-hybrid electric vehicle cannot propel the vehicle solely through the battery.
Range-extender hybrid electric vehicles (RE-HEV)
These are BEVs but with a gasoline-powered generator on board as an additional assurance. The generator is only used to recharge the battery pack. For that, the range extender mode has to be selected. In range extender mode, unlike typical BEVs, these cars produce emissions.
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Filed Under: EV, FCEV, HEV, PHEV