Introduction of pure electric motor/battery/electric control

Pure electric trucks, the name inadvertently entered our world, from the simple replacement of the motor to the current pure electric power chain pure electric trucks are no longer the era of simple electric motors instead of diesel engines.

Pure electric is not equal to changing the engine. There are also three major pieces of electric vehicles.

Compared with ordinary diesel and gasoline engine trucks, the most direct and simple difference between pure electric motors is that the engine is different. Pure electric motors use electric motors instead of traditional diesel/gasoline engines, replacing the fuel with battery packs to power the electric motors. One of the most important components is the electronic control system, which consists of a battery management system and a control system that manages the output of the battery pack and controls the energy of the battery and regulates the speed of the motor.

At present, the simplest electric electric truck in China is to replace the diesel engine with a motor. It is the most primitive and simple to solder a bracket to mount the motor at the original engine position. Without any control system, such a pure electric truck even retains a manual gearbox.

Through the continuous development of technology, pure electric trucks have been developed from simple and rough replacement motors to complete control systems, battery management systems, electric motors and so on. For a mature pure electric truck, the mature three-piece (motor, battery, electronic control system) can be called a true pure electric truck.

Pure electric truck requires high motor is the focus

1. The electric vehicle motor should have a large starting torque, good starting performance and good acceleration performance to meet the requirements of frequent start/stop, acceleration/deceleration and climbing of electric vehicles;

2. The electric vehicle motor should have a wide constant power range to meet the needs of electric vehicles at high speeds;

3. The electric vehicle motor should have a large range of speed regulation capability, have large torque at low speed, high power at high speed, and can adjust the driving speed and corresponding driving force of the electric vehicle at any time according to driving needs;

4. Electric car motor should have good efficiency characteristics, in the wide range of speed / torque, to obtain the best efficiency, improve the continuous mileage after a charge, generally required in the typical driving cycle area, get 85% ～93% efficiency;

5. The outer dimensions of electric motor motors are as small as possible and the quality is as light as possible;

6. Electric motor motor should have good reliability, strong temperature and moisture resistance, long-term work in harsh environment, low noise during operation and convenient maintenance;

7. Combine whether the controller can effectively recover the energy generated by the brake.

Motor type multi-permanent magnet synchronous motor is the majority

The electric motor is divided into DC electric motor, asynchronous motor, permanent magnet synchronous motor, switched reluctance motor, etc. These motors have their own characteristics. The similarities and differences between several motors can be visually seen through the following table.

At present, most of the pure electric trucks are permanent magnet synchronous motors. Compared with other types of motors, permanent magnet synchronous motors have the characteristics of high efficiency and large specific power, but the control system of permanent magnet synchronous motors is relatively complicated. The cost is relatively high, and some small pure electric truck companies do not currently have their own permanent magnet synchronous motor technology.

Battery technology continues to develop Lithium battery has become the protagonist

Another important component on pure electric trucks is the battery. For pure electric trucks, the battery is the source of continuous power. Therefore, the basic requirements of pure electric trucks can be summarized as follows:

1. The reliability of the battery reaches the demand for the vehicle;

2. The battery has a long service life and the number of cycles during deep discharge reaches the requirements of the vehicle;

3. Short charging time, small battery size and quality, and strong environmental adaptability;

4. The battery health status changes consistently during use, and does not affect the overall performance;

5. High power density and energy density, no environmental pollution problems, and low cost.

Through the above requirements, we can see that the pure electric truck has higher requirements on the battery itself, especially the weight and size of the battery are required to be as light and small as possible then how to measure the quality of a battery, you can judge the quality of a battery through the following technical indicators.

Capacity: The amount of electricity that a fully charged battery can provide under specified conditions, usually expressed in ampere-hours (A.h).

Charging rate: the current expressed in amps when the battery is charging

.Fully charged state: When all available actives in the battery have been converted to a fully charged state.

Overcharge: Charging that continues after full charge.

Urgent charging: Usually a partial charging at a high rate for a short period of time.

Trickle charge: To compensate for self-discharge, keep the battery in a continuous low current charge that is approximately fully charged.

Thermal runaway: A critical state that occurs during constant voltage charging. At this time, the current and temperature of the battery undergo a cumulative mutual reinforcement effect and gradually increase to cause damage to the battery.

Open circuit voltage: The potential difference between the positive and negative terminals of the battery when the circuit is open.

Load voltage: The voltage between the terminals when the battery outputs current.

Termination voltage: The specified voltage at which the discharge is considered to be terminated.

At present, the battery technology continues to develop. The battery for vehicles has evolved from ordinary lead-acid batteries to fuel cells. However, the most used batteries in pure electric trucks are lithium batteries. Lithium-ion batteries are a kind of rechargeable batteries. Lithium ions move between the positive and negative electrodes to work. A battery that uses a lithium-containing material as an electrode is generally representative of modern high-performance batteries. Lithium batteries are currently the most widely used in the automotive industry, with broad development prospects. In the future, battery development may break through on lithium batteries; mainly lithium cobaltate, lithium manganate, lithium iron phosphate and ternary materials.

The main advantages of lithium batteries are as follows:

The operating voltage of the single cell is up to 3.7V, which is three times that of nickel-cadmium batteries and nickel-hydrogen batteries, and nearly twice that of lead-acid batteries.

Light weight, larger than energy, up to 150Wh/Kg, twice that of nickel-metal hydride batteries and four times that of lead-acid batteries.

The volume is small, the height reaches 400Wh/L, and the volume is one-half to one-third of the lead-acid battery.

The cycle life is long, the number of cycles can reach 1000 times, the service life can reach 3-5 years, and the service life is about two to three times that of lead-acid batteries.

The self-discharge rate is low, less than 5% per month, no memory effect, and can be charged anytime, anywhere.

No pollution, there is no toxic substance in the lithium battery, so it is called green battery.

Guarantee the normal operation control system of the vehicle is the key

Another component in the pure electric truck is also quite important, that is, the battery management control system, the electric vehicle battery management system BMS is mainly used for real-time monitoring, fault diagnosis, SOC estimation, mileage estimation, and power mileage parameters of the electric vehicle. Short-circuit protection, leakage monitoring, display alarm, charge and discharge mode selection, etc., and information exchange with the vehicle integrated controller or charger through the CAN bus to ensure efficient, reliable and safe operation of the electric vehicle.

The electronic control system can be divided into BMS system and display system. In simple terms, the BMS system mainly collects battery data, battery charge and discharge status, total battery voltage, total battery current, battery temperature and battery temperature in each battery box, body module battery voltage, etc. Since the power batteries are used in series, real-time, fast, and accurate measurements of these parameters are the basis for the proper operation of the battery management system.

Estimated remaining battery: The remaining energy of the battery is equivalent to the fuel of the traditional car. The state of charge (SOC) is estimated to allow drivers to keep abreast of system health. The parameters such as charge and discharge current and voltage are collected in real time, and the remaining power is estimated by the corresponding algorithm.

Charge and discharge control: Charge and discharge the battery according to the state of charge of the battery. When a parameter exceeds the standard, if the voltage of the battery is too high or too low, the system will cut off the relay to ensure the normal use and performance of the battery pack. Stop the energy supply and release of the battery.

Thermal management: Collect the temperature of the battery measuring point in each battery box in real time, and prevent the battery temperature from being too high by controlling the cooling fan.

Equilibrium control: Due to the difference in battery individual and the different use status, the inconsistency of the battery during use will become more and more serious, and the system should be able to judge and automatically perform equalization processing.

Fault diagnosis: The working voltage of electric vehicle battery is generally high (90V-700V). The system should monitor the short circuit of power supply, leakage and other conditions that may cause harm to people and equipment.

Battery Condition Prediction and Alarm: By collecting battery parameters, the system has the function of predicting battery performance, fault diagnosis and early warning in the battery pack to maintain and replace the battery to ensure safety.

Information monitoring: The main information of the battery is displayed in real time on the vehicle display terminal.

Parameter calibration: Due to the type and quantity of batteries used in different models, the capacity and quantity of each battery box are different, so the system should have the function of calibrating information such as vehicle type, vehicle number, battery type and battery mode.

Editor

Pure electric trucks have become the representative of new energy. The three major parts of pure electric trucks are mainly electric motors, batteries and electronic control systems. These three are important components of pure electric trucks. At present, the new energy technology based on BYD in China has become increasingly mature, and it is ahead of other countries in terms of passenger cars.

The bottleneck of pure electric trucks is still battery technology, although lithium batteries have been used on large electric trucks on a large scale. However, due to technical problems, the cost endurance, charging time and other issues have always been short-board of the battery, becoming a roadblock for the development of pure electric trucks.

The page contains the contents of the machine translation.