What is an extended-range electric vehicle? Introduction to three extended-range electrical architecture diagrams

In recent years, we often hear about a new type of new energy vehicle - extended-range electric vehicles. The most representative car company is Ideal Auto, one of the "new forces". With the increase in extended-range sales, many domestic car companies have begun to launch related models, but the sales are not satisfactory. So, what is an extended-range electric vehicle? What is the architecture of the extended-range model? What are the differences between the systems of each company? What is the application prospect of extended-range? Many media have reported and analyzed these questions, but the answers seem to be different.

1. What is an extended-range electric vehicle?

In my country, according to GB∕T 19596-2017 Electric Vehicle Terminology, the definition of extended-range electric vehicles (the definition of the word extended range in Chinese and English is range extended, the abbreviation is RE, and some car companies use "ER") is as follows:

According to the standard, extended-range vehicles should have at least two modes, namely pure electric mode and "extended-range energy replenishment mode", and the "auxiliary power supply device" is independent of the drive system (i.e., it does not participate in any direct drive of the vehicle, that is, it is only used to charge the battery, which can be simply understood as a "power bank"). The requirements of CARB in the United States for such vehicles are as follows:

The main requirements are in terms of range and emissions. Many people confuse extended-range electric vehicles with plug-in hybrid electric vehicles. Let's use a simple picture to compare them:

As can be seen from the schematic diagram in the middle, the range extender has no mechanical connection to the vehicle's transmission, only an electrical connection, while the engine of a plug-in hybrid vehicle is directly connected to the transmission.

2. Range Extender and Electrical Architecture

2.1 Range Extender

We have already understood the concept of extended-range electric vehicles, so what is a range extender? In fact, it is very simple. The range extender is an "engine + generator", but the engine is somewhat different from the traditional engine (because the working conditions of the range extender do not need to cover all the working conditions on the traditional car, for example, the start of the engine on the traditional car requires a starter, and the start of the range extender engine is completed by a generator (or an integrated starter generator), so the engine does not need a starter). In order to improve the efficiency of the system, it is often necessary to optimize the design of the traditional engine, such as using an Atkinson cycle engine, increasing the compression ratio and other optimization methods. Some companies will still directly use traditional engines to develop range extenders in the early stage of development, and the efficiency of such products is often extremely low. The generator has an inner rotor motor, an outer rotor motor, a parallel shaft integrated motor, etc., all of which are developed to improve efficiency. The assembly after the motor and the engine are connected through a dual-mass flywheel (the old-fashioned one also has a single-mass flywheel + clutch) is the range extender.

Even if a dual-mass flywheel is used, the engine speed and motor speed are basically the same when the range extender is working. We know a formula for power - power = (speed * torque) / 9550 - in order to achieve the same power, either by increasing the speed or increasing the output torque, and most of the cost of the motor is in the coil, so some companies use a differential device to connect the engine and the motor in a heterogeneous manner. Assuming the speed ratio is 5:1, when the engine is 1000r, the motor speed can reach 5000r, which can reduce the output of torque and thus reduce the cost of the motor, but at the same time increase the requirements for the machinery.

2.2 Electrical architecture

There are three types of extended-range electrical architectures on the market (the diagram only reflects the CAN topology). Let's draw a simple diagram:

Architecture 1: REMS (range extender management system) is connected to the public CAN of the vehicle, receives information from the battery and the vehicle, and then controls and coordinates EMS (engine management system) and GCU (generator controller) to generate electricity for the range extender to charge the battery. This type of architecture is relatively distributed, and the original parts supplier has a small workload. They only need to develop REMS. EMS and GCU are not directly connected to the public CAN, but are forwarded through REMS.

Architecture 2, cancel REMS and integrate the extended-range control function into EMS, GCU or VCU. It depends on the degree of coordination and development costs of each automaker for each component (I have privately developed two of them for customers). There is no particular advantage or disadvantage. The manufacturing cost is reduced (one less node), but at the same time, the software/hardware requirements are increased, and a considerable development fee is often required.

Architecture 3, cancel EMS and REMS, integrate engine control function and range extension control function into VCU, need to redevelop VCU (at this time VCU is already a power domain, which is being done privately), further improve hardware/software requirements, and reduce manufacturing costs. Personal opinion: GCU involves high voltage after all, high voltage devices are integrated into the high voltage "all-in-one", and low voltage parts such as EMS are more suitable to be integrated into low voltage nodes.

2.3 System Software

The software of the range-extending system is developed in the form of models (some companies also use code). Today, the emission indicators for light vehicles have reached the sixth stage, and in addition to the functions, the OBD system needs to be developed. All the nodes of the entire component that will affect the emissions of the entire vehicle when they fail need to develop this function (not just the engine management system). For example, the dashboard of the entire vehicle, if some functions of the node are abnormal, but it will not affect the emissions of the entire vehicle, then the node can be ignored. However, nodes like VCU and BMS, once the function is abnormal, it will affect the power of the entire vehicle, which will affect emissions, so this type of node needs to be planned. However, the emission regulations for heavy-duty vehicles have not been officially implemented (and there are no regulations for range extension), so there are some differences for commercial vehicles.

3. Extended-range electric vehicle market and applications

Before conducting a market analysis, let us first review the development of new energy vehicles in the next 15 years as mentioned in the "Energy-Saving and New Energy Vehicle Technology Roadmap 2.0" compiled by the China Society of Automotive Engineers.

By 2025, the annual production and sales scale of automobiles will reach 32 million units, by 2030, the annual production and sales scale of automobiles will reach 38 million units, and by 2030, the annual production and sales scale of automobiles will reach 40 million units.

By 2025, new energy vehicles will account for about 20% of total sales, 3200*0.2=6.4 million vehicles/year; by 2030, new energy vehicles will account for 40% of total sales, 3800*0.4=15.2 million vehicles/year; by 2035, new energy vehicles will account for 50% of total sales, 4000*0.5=20 million/year;

By 2025, pure electric vehicles account for 90%, and the remaining 10% are hybrid (including extended-range) + fuel cell vehicles, 640*0.1=640,000 vehicles/year; by 2030, pure electric vehicles account for 93%, and the remaining 7% are hybrid (including extended-range) + fuel cell vehicles, 1520*0.07=1.064 million vehicles/year; by 2035, pure electric vehicles account for 95%, and the remaining 5% are hybrid (including extended-range) + fuel cell vehicles, 2000*0.05=1 million vehicles/year;

The number of hydrogen fuel cell vehicles in 2025 (not sales) will be 100,000, and the number will be 1 million from 2030 to 2035. Subtracting the number of hydrogen fuel cell vehicles, can we get a rough idea of ​​hybrid power? Since the official data on new energy vehicles for the whole year of 2021 has not been released, let's take a look at the data up to November 2021 (the trend will not change significantly):

As of November 2021, a total of 3.022 million new energy vehicles have been produced, with plug-in hybrids accounting for 17.13%. The number of new energy passenger cars is 2.869 million (3.312 million new energy passenger cars were wholesaled from January to December 2021), and the proportion of plug-in hybrids is 17.95%. There are 154,000 new energy commercial vehicles, and the proportion of plug-in hybrids is 19.48%. The sales of extended-range electric vehicle manufacturers (Ideal's annual sales in 2021 were 90,491, and the sales of other car companies were far lower than Ideal) are not particularly outstanding except Ideal. Even if we say that extended-range will account for half of plug-in hybrids, then by 2035, according to the estimate of "Route 2.0", the annual production and sales of extended-range (passenger/commercial together) should be 100*0.5=500,000 vehicles. Ideal has already formed a brand effect, so how much share can other car companies that have launched extended-range vehicles have? With the continuous breakthroughs in battery technology (GAC Aion LX Plus is known as the world's longest-range pure electric vehicle, equipped with a 144.4kWh battery and a battery density of 205wh/kg), hybrid vehicles will face greater challenges (but the price of batteries will increase by about 20% in 2022, so there will still be a market for them in the next few years). Let's take a look at the forecast of the extended-range market by foreign analysis company IDTechEx: