Development Of An Online Testing Device For Insulation Resistance Of Pure Electric Vehicles

Pure electric vehicle insulation resistance detection system is to detect the insulation resistance of the car body by the positive and negative poles of the pure electric vehicle power lithium battery,and then determine the insulation damage condition of the vehicle power battery according to the detected insulation resistance value.When the positive and negative poles of an electric vehicle’s power battery have a small insulation resistance or a short-circuit fault,the device can cooperate with a battery management system and other devices to perform alarms,battery protection,and other tasks.In recent years,with the country’s vigorous advocacy of “green travel” activities and the active promotion of new energy strategies,people’s awareness of environmental protection has also gradually increased.Nowadays,new energy electric vehicles are developing rapidly,and their green energy-saving features are favored by consumers.,Has become one of the main directions of the current automobile development.Pure electric vehicles refer to vehicles that use power lithium batteries as the only power source.Compared with mature and stable conventional cars that use gasoline and diesel as their power sources,the safety and status characteristics of batteries are directly related to the stability of vehicle operations.The safety of the personnel on board the car,especially the detection of the insulation status of the power battery,is directly related to the personal safety of the passengers.Therefore,the real-time detection of the insulation status of the lithium battery of the electric vehicle is the most basic and most necessary for the battery of the electric vehicle.This paper compares several traditional battery insulation detection schemes,and then proposes an improved non-equilibrium bridge insulation resistance measurement scheme.This program adopts STM32F105 as the core controller of the system,designs the hardware circuit according to the improved unbalanced bridge detection scheme,uses the external AD acquisition chip ADS8028 to collect the voltage of the collection points of the unbalanced bridge,and then collects The voltage of the electric vehicle is used to calculate the insulation resistance of the lithium battery of the electric vehicle,and finally the detection of the insulation characteristics of the electric vehicle is realized.This paper first introduces the significance of the measurement of insulation resistance of electric vehicles and the current status of the development of insulation resistance measurement systems for electric vehicles at home and abroad.Then it introduces several commonly used electric vehicle insulation resistance measurement programs and analyzes their advantages and disadvantages.Based on this,it proposes Based on unbalanced bridges to measure the insulation resistance of the program.According to the proposed measurement scheme,the hardware circuit diagram and the software flow chart are designed.The insulation resistance measurement system based on the improved unbalanced bridge is designed and the insulation resistance of the automotive lithium battery is simulated and the data is measured in real time under the laboratory conditions.Error Analysis.Test results in a laboratory environment show that when the insulation resistance of an electric vehicle is between 1kΩ and 120kΩ,the system detection error is within 5%,and when the insulation resistance of the electric vehicle is near the critical area(10kΩ),the detection error of the system can be The control is within 3%,so the detection accuracy of the system can meet the relevant requirements of the national EV insulation detection system;this system can send the insulation resistance detection data and data detection time to the battery management system through the CAN bus in real time.Later reading of the data to model the battery insulation damage analysis,at the same time,when the electric vehicle power battery insulation serious damage sound and light alarm and send the alarm data frame through the CAN bus,in order to ensure the normal operation of the electric vehicle normal insulation and Personal safety.