Battery Electric Vehicle (BEV)
There are different types of electric vehicles, as shown in the diagram below. This article will focus on Battery Electric Vehicle (BEV) and provide a simple overview of its key internal components.
A typical BEV would look like the diagram shown below. Powertrain consists of all the components involved in generating power and moving the car. On the other hand, drivetrain is everything of powertrain without the electric motor. PEU consists of an inverter or a converter.
We can have AC charging at home. AC charging goes through the OBC, BJB, and then to the battery pack. We can have DC charging outside the home at the charging station. DC charging goes through the BJB, and then to the battery pack.
OBC is to convert AC to DC. BJB is to connect battery pack to other system units, acting like a ‘train interchange station’. Take a look at the white arrow shown below. See how BJB connects the battery pack to the MCU and DC-DC converter.
There are 2 levels of voltage in BEV: high voltage (HV) and low voltage (LV). HV is 100 ~ 800V. See the ‘white’ dots below. LV is 12V or 48V. Traditional 12V take care of start-up motor, lighting, infotainment …etc. The future trend is 48V as more applications are added (turbo charger, PTC heater, air condition … etc.).
Battery Pack (电池组/电池包) is made up of several Modules (电池模块). Modules is made up of several Cells (电池). BMS is the ‘brain’ of Battery Pack.
MCU is a DC-AC inverter. It converts DC to AC. MCU draws power from battery pack via BJB. MCU supplies power to the electric motor. DC-DC converter converts DC to DC (Step up/down). In this case, it is step down to 12 / 48 VDC. DC-DC converter draws power from Battery Pack via BJB. DC-DC converter supplies power to 12V/48V Battery. Sometimes, MCU and DC-DC converter are integrated together to become PCU (Power Control Unit).
Electric Motor can be AC/DC. In this case it is AC. It turns the gear inside the transmission box. Transmission box is also known as gearbox. Most BEV has 1 gear only, because the power output from electric motor is strong enough to cover all road conditions.
On-board ‘computers’ were introduced to the automotive industry (in 1970) even before the presence of BEV. These computers control & regulate various functions inside a car, eg: engine, transmission. A generic term is used to describe these computers: Electronic Control Unit (ECU).
This is not to confuse with ‘Engine Control Unit’, where both of them share the same abbreviation ‘ECU’. Please note that Engine Control Unit is also an Electronic Control Unit itself. Sometimes you see terms ‘PCM’ (Powertrain Control Module). PCM is actually Engine Control Unit + TCM. Engine Control Unit has nothing to do with BEV. Engine Control Unit manages the actuators of the traditional Internal Combustion Engine (ICE).
Luxury cars like BMW 7-series models have as many as 150 ECUs.
Vehicle Control Unit (VCU) (also an ECU itself) manages all the Electronic Control Units inside BEV as shown in the diagram below.
Traditional headlight is controlled by an ECU called Body Control Unit (BCU). Now with higher functionality of LED, additional ECU called Light Control Unit (LCU) is needed.
One of the future trends we can see for BEV is integration:
· 2-in-1: DC-DC converter + MCU
· 3-in-1: DC-DC converter + OBC + BJB
· 4-in-1: DC-DC converter + MCU + electric motor + transmission box
· 6-in-1: DC-DC converter + OBC + BJB + MCU + electric motor + transmission box
As integration involves more and more components, the design will become more complicated. This will also imply that there will be less interconnection (such as connectors, cables) between the components. The level of interconnection will be kept to a minimum to accommodate the integration. Any interconnection solution provided will have to be small and compact in size (for connectors) and highly flexible & high-temperature (for cables).
Another future trend for BEV is automotive IoT (V2X). IoT (Internet of Things) is a network of devices that connect, interact and exchange data with each other. Automotive IoT is smart car with V2X capability. Why bother with V2X? The answer is road safety.
V2X is Vehicle to Everything. It includes:
· V2V (Vehicle to Vehicle)
· V2I (Vehicle to Infrastructure)
· V2N (Vehicle to Network)
· V2P (Vehicle to Pedestrian)
One of the key automotive associations that focuses on V2X technology is the 5G Automotive Association (5GAA). You may want to visit their web site at https://www.5gaa.org for the latest developments on V2X.
I hope you’ve enjoyed reading this and wish you’ve learned a few things about Battery Electric Vehicle.
