- Selection and power matching of driving motor
The motor shall have good torque speed characteristics, generally with a speed of 6000r / min-15000r / min. According to the driving conditions of the vehicle, the driving motor can operate in the constant torque area and constant power area. The drive motor shall always operate within the high efficiency range. The efficiency is 0.75 ~ 0.85 in the low-speed high torque (constant torque area) operation range and 0.8 ~ 0.9 in the constant power operation range.
- Selection and characteristics of power battery pack
The power battery system is the energy source of the whole vehicle and provides driving electric energy for the whole vehicle. The volume, shape and technical parameters of battery system affect the driving performance of electric vehicle. It is one of the most important subsystems of electric vehicle. The parameter matching of electric vehicle power battery system mainly includes the selection of battery type, battery pack voltage and energy. Electric vehicles require the power battery system to have high specific energy and specific power to meet the requirements of vehicle driving range and power performance. At the same time, it also hopes that the power battery system has the charge discharge cycle life equivalent to the service life of the vehicle, with high efficiency, good performance price ratio and maintenance free characteristics.
- Determination of transmission ratio of reducer
Due to the high speed of the motor, it can not directly drive the wheels of the vehicle. Usually, the reducer with large speed ratio or 2-speed transmission is adopted in the driving system. Function: reduce speed and increase torque. The reverse gear is not set in the reducer or transmission. The reverse is realized by the reverse rotation of the motor.
- Design of battery management system and vehicle control system
The function of the battery management system is to monitor the working state of the battery in real time. Improper use in the actual use process will have a great impact on the battery life, and the biggest influencing factor is the large difference between the excessive discharge of the battery and the single battery, resulting in the early scrapping of the whole battery pack. The battery capacity in use is closely related to different service conditions, and it is not a fixed value. The capacity value marked on the battery commonly used by people is only a specific value of a battery in a specific environment, specific load and specific time period. The capacity value of the battery is not consistent with the original value of the factory under different loads, different environments and different times. The development of real-time battery monitoring and control system for electric vehicle can monitor the voltage, current and temperature of the battery in real time, record various parameters affecting the working state of the battery, such as the number of charge and discharge of the battery, and accurately estimate the state of the battery and the best working parameters. According to these real-time information, on the one hand, users can understand the real situation of the battery at any time, use the electric vehicle more reasonably, do a good job of maintenance in advance and prolong the service life of the electric vehicle; On the other hand, the built-in MCU control program can actively manage and protect unreasonable use, which can not only meet the requirements of users to the greatest extent, but also actively avoid the impact on main components such as batteries due to improper use.
The main purpose of the whole vehicle control system is to extend the driving range. The driving range refers to the mileage of the electric vehicle from the full charge state of the power battery to the end of the test specified in the standard. It is the basic method for ev to measure the driving range by using the working condition method to drive repeatedly according to a certain working condition. GB / t18386-2001 test method for energy consumption rate and driving range of electric vehicles issued by China is applicable to EV with maximum total mass ≤ 3500kg and maximum speed ≥ 70km / h.