New energy vehicle electric drive, battery and electronic control system

The core technology of new energy vehicles that distinguishes them from traditional cars is "three powers," including electric drives, batteries, and electronic controls.

The following is a detailed explanation of the basics of the three power:

First, the battery

Batteries are an industry related to chemistry, machinery industry, electronic control, and so on. The key of the battery is the battery core. The most important materials for the battery core are the positive and negative electrodes, the separator, and the electrolyte. Positive electrode materials are widely known as lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, ternary, and high nickel ternary.

The power battery is a very “young” product. In 1996, the EV-1 was introduced using a lead-acid battery. It is the prototype of modern electric vehicle architecture, from lead-acid batteries to Japanese hybrid nickel-metal hydride batteries, and is now popular. Lithium batteries are only 20 years old.

From the perspective of the fourth batch of “new energy vehicles recommended model catalog” new energy passenger car configuration batteries, 32 models using 17 companies' batteries, of which 16 are battery manufacturers, and the other is Changan New Energy, This shows that direct sales of other passenger car power batteries, including batteries, battery packs and battery management systems.

Most of the independent brand OEMs do not have their own battery and battery pack design capabilities

Although multinational car companies do not have their own batteries, they insist on designing and manufacturing their own battery components and management systems. This is to strengthen the core competitiveness of power batteries. The difference with most of the independent brands is that, even if they do not use this battery, they can change the battery brand to still be able to design the battery pack, and the core technology is still in their own hands.

However, we are more concerned about the power battery, which is also the source of energy in new energy vehicles. At present, nickel-metal hydride batteries are facing elimination, and lead-acid batteries are supported by the total amount of lithium-ion batteries. Therefore, lithium batteries are currently the most important. (As shown below)

First introduce some important concepts

In terms of energy density, the battery is certainly not as good as gasoline, but how much is the difference? A box of 50L of gasoline can run about 600km. How much battery is required for an electric vehicle with the same mileage? (As shown below)

The following table lists the differences in the main performance indicators of the four types of lithium batteries. As can be seen from the table, the four types of batteries have their own advantages and disadvantages. What kind of battery does the auto makers choose? Which type of battery will be the mainstream of the future?

Digital electronic products have low requirements for the safety of lithium batteries. Lithium cobaltate batteries are most suitable for the 3C field. Tesla's daring to use such batteries is also capable of obtaining strong endurance in the future, but at the same time its safety performance should be discounted.

Lithium manganate batteries have won the largest market share of power batteries because of their unbiased characteristics. Although their energy density is not as good as that of lithium cobaltate and ternary lithium, other comprehensive performances are excellent.

If it is not a lower energy density that limits the lithium iron phosphate battery, it may indeed become the dominant power battery. The two key indicators of safety performance and life are top-notch.

If the domestic lithium battery development focus on the lithium iron phosphate battery, the international power lithium battery industry non-ternary lithium battery is a new star, higher than the lithium cobalt oxide battery energy density, the cost is lower than lithium cobalt oxide battery Security is also quite reliable. Different car companies have their own considerations for the choice of power lithium battery (as shown below)

Power Battery Development Trend

to sum up:

Second, the electric drive

The electric drive consists of three parts: transmission mechanism, motor, and inverter. At present, the transmission mechanisms of electric vehicles at home and abroad are single-unit deceleration, that is, there is no clutch and no speed change. In the future, every electric vehicle company will add complexity to the transmission mechanism, and at the same time reduce the demand for motor and motor varistors, that is, improve performance and reduce costs.

The motor consists of three parts: stator, rotor, and housing. The key points of the motor technology are stator and rotor. The rotor is the main drive motor of the new energy vehicle and it bears all the functions related to the new energy vehicle movement. The motor of the new energy vehicle has forward rotation and reverse rotation. The forward rotation is the forward rotation and the reverse rotation is the reverse rotation.

New energy vehicles in the process of positive acceleration and acceleration, the motor is a negative torque, the accuracy of the torque means that the speed of new energy vehicles to accelerate the speed. When the torque generates an error, the new energy vehicle that needs the motor to complete the acceleration, the mileage is converted to need to consume the same amount of energy to complete the battery, and the cost of the battery is greater than the motor, so the efficiency and performance of the new energy vehicle motor to Important. At present, there are mainly three types of click-driven systems for automobiles: DC click drive systems, permanent magnet synchronous motor drive systems, and AC induction click drive systems.

DC

Induction motor

Permanent magnet motor

The inverter is a device that converts DC power into AC power. If an inverter of an electric vehicle can support a higher voltage, the corresponding voltage charge current is larger and the power is larger, which means that the same current is charged and the charging power is Can be scaled up, that is, charging time will be shortened. If the supporting voltage of the inverter is increased, the heat generated by the inverter during charging will increase, then the heat dissipation problem of the IGBT module in the inverter needs to be solved, which is a key issue for improving the charging efficiency. This research is more in-depth, such as its application of silicon-carbon technology.

Third, electronic control

New energy automotive motors and electronic control systems are used as a substitute for traditional engine (gearbox) functions, and their performance directly determines the main performance indicators such as climbing, acceleration, and maximum speed of electric vehicles. At the same time, the operating conditions faced by the electronic control system are relatively complex: they need to be able to start and stop frequently, accelerate and decelerate, require high torque at low speeds/climbs, require low torque at high speeds, and have a large transmission range; hybrid vehicles also need to handle Motor start, motor power generation, brake energy feedback and other special functions.

In terms of electronic control, for the general engine manufacturer, only the controller of the vehicle is really mastered. The difference between the vehicle controller of a new energy vehicle and the vehicle controller of a conventional vehicle is not so great, and its maturity is also relatively high.

In addition, the energy consumption of the motor directly determines the cruising range of the fixed battery capacity. Therefore, the electric vehicle drive system has special requirements on load requirements, technical performance and work environment:

1. The drive motor must have a higher energy density, achieve light weight, low cost, adapt to limited space in the vehicle, and must have energy feedback capability to reduce the energy consumption of the entire vehicle;

2. The drive motor has both high speed and wide speed control and low speed and high torque to provide high starting speed, climbing performance and high speed acceleration performance;

3, the electronic control system must have high control accuracy, high dynamic response rate, and at the same time provide high security and reliability.

The motor electronic control system is an important part of the new energy automotive industrial chain. Its technology and manufacturing level directly affect the performance and cost of the entire vehicle. At present, the degree of autonomy in the field of electrical and electronic control in China is still lagging far behind that of batteries. Some electronically controlled core components such as IGBT chips still do not have fully independent production capabilities, and they have complete intellectual property rights for vehicle companies and parts and components companies. Still a minority.

It can be seen from the above analysis that the vast majority of self-owned brands only mastered the vehicle controller and the three-electric integration technology, but they are still in the stage of no entry for the three-component technology. After all, it is not a field, and the technology is not accomplished overnight.

In terms of joint venture brands, there is no battery core is their only weakness, but through their own design of battery packs and battery management systems, and then master the power battery technology to make up for this shortcoming. This kind of technology needs to be accumulated.

Subsidies will gradually decline before 2020 or even withdraw afterwards. For OEMs, the most important task is how to reduce the cost of power batteries. This is also the key stage of the game between technology and the market. If technology is controlled by others, it will be difficult to reduce costs.