Electric vehicles (EV) have developed rapidly in recent years, and have been generally considered by the automotive industry to be a new direction for future automotive development. However, there are still some shortcomings in electric vehicles, which make them unable to replace traditional fuel vehicles. In this regard, the first thing that comes to mind must be the battery life of electric vehicles. In fact, to solve the battery life problem of electric vehicles, there are mainly two aspects to be improved: batteries with higher energy density and electrical loads with lower power consumption (higher efficiency). There is a long way to go for the development and application of batteries with higher energy density. Therefore, effective testing and evaluation of the power consumption and efficiency of electric vehicles and various systems is the main way to improve the battery life of electric vehicles. Thus, the concept of energy flow test was born.
1 EV energy flow path analysis
Energy flow is the transmission path of vehicle energy and the transmission efficiency and energy consumption during the transmission process. Professional energy flow testing helps to understand the energy consumption and energy conversion efficiency of the vehicle and each system, and can be targeted for improvement and design to improve energy efficiency.
Electric vehicles (EV) have a special energy recovery mechanism under braking conditions, so the main energy flow of the vehicle can be divided into charging-driving condition energy flow and braking condition energy flow. From external charging to driving, the main electric energy of electric vehicles flows through in sequence: external charging equipment → on-board charger OBC → battery pack → AC/DC inverter → electric motor control → wheels. See Figure 1 for details of the energy flow.
If energy is recovered during braking, the main electric energy flow is from the wheel to the battery pack: wheel→motor electronic control→AC/DC inverter→battery pack. See Figure 2 for details of the energy flow.
From the above content, we can see that there will be energy loss in every place (mostly dissipated as heat energy), and the energy consumption of each model in the same place is different, so the energy efficiency difference of the whole vehicle is produced.
2 Analysis of EV energy flow test
Electric vehicles (EV) are mainly divided into high-voltage systems and low-voltage systems from the perspective of vehicle electrical system categories. The high-voltage system mainly includes: electric drive system - drive motor/motor controller (MCU); power supply system - battery pack/on-board charger (OBC); other high-voltage loads - air conditioner (AC)/heater (PTC)/ High voltage power distribution box (PDU)/DCDC, etc. The low-voltage system mainly includes 12V power supply, fan, water pump, BMS and instrumentation.
According to the above analysis of the electrical structure of the electric vehicle, the main test requirements of the energy flow test can be sorted out, as shown in Figure 4.
Brief description of the test: During the operation of the vehicle, the vehicle speed, accelerator/brake pedal signal, battery current, battery voltage, battery temperature, motor output speed, and motor output torque are collected throughout the entire process; the main components of the vehicle (including the motor controller, air conditioning system) , DCDC, etc.) working current and voltage data.
Three professional testing equipment and solutions
Fengqiu Technology cooperates with IPETRONIK in Germany to provide professional energy flow testing equipment and solutions for electric vehicle customers . It includes voltage and current signal test of high and low voltage system, temperature signal test of high and low voltage system, professional charging equipment test, bus data acquisition and professional automotive measurement software and post-processing analysis software......
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