In this article, we explore the basics of electric vehicle powertrain. For a video explanation visit our YouTube channel
What is Powertrain?
As the name suggests, the powertrain provides power to the vehicle. Powertrain refers to the set of components that generate the power required to move the vehicle and deliver it to the wheels.
Difference between Powertrains of EVs and ICE vehicles
The powertrain of an electric vehicle is a simpler system, comprising of far fewer components than a vehicle powered by an internal combustion engine.
Main Components of an ICE vehicle powertrain – An ICE vehicle has hundreds of moving parts. Main components of its powertrain are Engine, Transmission and Driveshaft. Power is generated by the engine and transmitted to the driveshaft. Other internal parts and components of the engine, differentials, axles, emissions control, exhaust, engine cooling system etc are also included in the powertrain.
Main Components of an EV Powertrain
An EV powertrain has 60% fewer components than the powertrain of an ICE vehicle. The components are described below.
Battery Pack – The battery pack is made up of multiple Lithium-ion cells and stores the energy needed to run the vehicle. Battery packs provide direct current (DC) output.
DC-AC Converter – The DC supplied by battery pack is converted to AC and supplied to the electric motor. This power transfer is managed by a sophisticated motor control mechanism (also referred to as Powertrain Electronic Control Unit) that controls the frequency and magnitude of the voltage supplied to the electric motor in order to manage the speed and acceleration as per driver’s instructions communicated via acceleration/brakes.
Electric Motor – Converts electrical energy to mechanical energy, that is delivered to the wheels via single ratio transmission. Many EVs use motor generators that can perform regeneration as well.
On-board Charger – Converts AC received through charge port to DC and controls the amount of current flowing into the battery pack.
Apart from the above core parts, there are multiple hardware and software components in an EV powertrain. Electronic Control Units (ECUs) are basically software programs integrated with the powertrain components to help data exchange and processing, e.g. Powertrain ECU mentioned above. There are several small ECUs in an EV that perform specific functions. The communication between different ECUs in a vehicle is commonly carried over CAN protocol. More examples of core ECUs are:
Battery Management System (BMS): A BMS continuously monitors the state of the battery and is responsible for taking necessary measures in case of a malfunction. BMS performs cell balancing to deliver maximum efficiency from the battery pack. It is responsible for communication with other ECUs and sensors, as well as EVSEs to control the charging input, check the current state of charge and share data about battery specifications.
DC-DC Converter – A battery pack delivers a fixed voltage, but the requirement of different accessory systems (e.g. wipers, lights, infotainment system, mirror control) in the EV would vary. The DC-DC converter helps distribute power to different systems by converting the output power from battery pack to the expected level. After conversion, power is delivered to respective smaller ECUs via wiring harness.
Thermal Management System: Responsible for maintaining optimum operating temperature range for powertrain components.
Body Control Module (BCM): The BCM is responsible for supervising and controlling the functions of electronic accessories such as power windows, mirrors, security and vehicle access control.
Related Read – Top EV powertrain component manufacturers in India.
Last Updated: 16 Jan 2020
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