What is an EV?

We’ve used BMW’s great little electric car, the i3, to illustrate the usual elements you might expect to find in an electric vehicle.

Due to the flexible positioning of electric car components, locations can vary wildly.

In the BMW i3 example, it is a rear-wheel-drive electric car and as such has a rearward bias of components.

A front-wheel-drive electric car, such as the Nissan Leaf, houses many components under the bonnet, giving greater rear luggage space.

Battery Pack & Battery Cells

The Battery Pack is the electric storage centre for any EV. As the system is more flexible than liquid fuel, battery packs containing hundreds of cells are often spread around the vehicle to distribute weight more evenly. They usually include a Battery Monitoring System (BMS) which manages the temperature and state of charge of each individual cell.

Motor Controller & Inverter

The motor controllers monitor the motor’s position, speed, power, consumption and temperature. Using this information and the throttle command by the driver, the motor controller and inverter convert the DC voltage supplied by the battery to three precisely timed AC waveforms, used to drive the motor.

Electric Motor & Gearbox

The electric motor converts electrical power to mechanical power.

Electric motors are up to three times more efficient than a standard petrol engine.

Using near instant torque to their advantage, gearboxes are often single-speed, but with different design considerations to a conventional ICE. The emphasis is usually on silent operation and a need to cope with higher RPM due to the electric motor.

Chassis Design

As components are more flexibly moved around the design, chassis designers are able to make better use of the space.

The i3 shown here has an aluminium chassis with a carbon fibre superstructure for the occupants.

Electric Power Steering

The power steering mechanism is usually unchanged in an electric car when compared to an ICE vehicle, using both electric and hydraulic power to assist the driver.

Brakes

More or less unchanged from a conventional vehicle. An electric vacuum pump is used to give power assistance to the driver.

Wheels & Tyres

Many electric vehicles have specially developed low-rolling-resistance tyres, meaning the vehicle is able to roll freely with lower drag, therefore increasing range. The tyres shown here offer great grip despite their narrow (155mm) profile.

Electric Coolant Heater & Control

Heating systems are specially designed for electric vehicle applications as there is no heat generated from an engine which was traditionally used to provide warmth to occupants.

Instead, the system works in a similar way to a kettle, with a submerged element that heats a liquid. This is passed through a matrix which has the interior blower fans waft air over them and into the cabin.

High Voltage Electric A/C Compressor

With no engine warmth to provide heating to occupants, electric power is used instead. With no engine drivebelt to drive the compressor, electricity is used instead.

The plus side is that it is more efficient and can usually be programmed in advance so that the vehicle may be cooled or heated using a remote application, or a smartphone.

Charging and Electronics

Converting mains AC voltage to DC for the batteries is usually done on-board the vehicle. To obtain a 12V system for the lighting, infotainment, etc, a DC-DC converter is used (together with a small 12V battery).