The power battery system is a system that combines the hardware body and the control system very closely. The test can be roughly divided into two parts: battery pack body (Pack) test, battery management system (BMS) test, the following describes the test conditions of these two parts. .
1, battery pack body (Pack) test
The battery pack body test is generally performed during the DV/PV (design verification/production verification) phase to verify that the design/production of the battery pack meets the design requirements. It includes temperature test, mechanical test, external environmental simulation test, low voltage electrical test. , EMC test, electrical safety test, battery performance test, abuse test test, etc. Because everyone is concerned about battery safety issues, here is a test method for battery pack abuse test:
1) Acupuncture test
The scene when the analog battery is pierced by a sharp object, because the foreign matter penetrates may cause an internal short circuit, and the test requires no fire and no explosion.
2) Salt water soaking
5% salt water immersion test for a long time, the battery function is normal.
At present, the waterproof and dustproof rating of the new energy vehicle battery pack is recommended to be IP67 (ie, 1 meter deep water soak for half an hour without damage, SAIC, Weilai's battery pack are IP67). The car's use environment is bad, how to do waterproof and dustproof Protection can't be overestimated (one year of heavy rain in Shanghai caused water in the garage, the traditional cars were flooded, and the electric cars were intact).
3) External fire
590 degrees Celsius fire for 130 seconds without explosion, fire, burning and no flame residue.
4) Drop
1m height free fall on the steel plate, the battery shell is fully functional.
5) Vibration test
The high-frequency vibration simulation test requires the battery pack to function normally. Colleagues who do the battery pack should know that this is also difficult to pass.
2, battery management system (BMS) test
The battery management system test is more focused on software testing, generally in the process of software function development.
Unlike the autopilot system that has not yet been mass-produced, the software design is different in C language. Today's mature electric vehicle control systems (such as vehicle controllers, motor controllers, battery management systems) are model-based software development. (Model-Based-Design). The advantage of MBD development over C is that it can express complex logic in a graphical way. The code readability, portability, development and debugging convenience are greatly enhanced, and mature code generation is utilized. The toolchain also avoids low-level errors that are easily generated by manual code.
Several tests such as MIL/SIL/HIL are specified in the model-based software development process:
1) MIL (Model-In-Loops) is model-in-the-loop testing, which is to verify whether the software model can implement software functions. The test basis is the software requirements decomposed from the system requirements.
2) SIL (Software-In-Loops) software is tested in the ring. The C code automatically generated by the comparison model is consistent with the function implemented by the model itself. The Sil test can be performed using Simulink's own tool.
3) PIL (Processer-In-Loops) processor in the loop test, the purpose is to test whether the automatically generated code is written to the controller, whether the function implementation is deviated from the model. PIL does not seem to matter, but does not pay attention to it. Cause some bad consequences (such as scheduling problems, CPULoad, stack overflow, etc.).
4) HIL (Hardware-In-Loops) hardware-in-the-loop test, test controller complete system function, generally build the test bench of the system where the controller is located, use electrical components to simulate sensors (such as temperature) and actuators (such as fan load) The electrical characteristics of the system verify the complete system function.
The use cases of these test links are derived from system requirements. In the automotive software development process, development and testing into V-shaped, commonly known as software development V model, interested students can view the automotive software development process ASPICE.
Test conditions of parts in the extreme environment of the vehicle: The durability test of the whole vehicle is generally the responsibility of the test & calibration engineer of the OEM. The cost of the endurance test of the whole vehicle is very large, and the engineering prototype is built (1 million per vehicle) Left and right), renting the test site, the engineering team spends money, it is a test of the financial strength of the manufacturer. There is no strong fund pool that can't run at all. But the more tests are carried out under extreme conditions such as extreme cold, high temperature and high humidity. The more you can fully verify the function, performance and endurance performance of the parts, the sooner you find the problem, the lower the cost of repairing the repair.
1. Low temperature endurance test, mainly test cold start performance, generally carried out in Heihe / Yakeshi. The low temperature charge and discharge capacity of the battery pack, low temperature protection strategy, battery pack heating function will be evaluated in this test.
2. High temperature endurance test, generally carried out in Golmud. Mainly test battery pack charging and discharging capacity at high temperature, battery pack cooling function and overheat protection strategy. The following picture shows Weilai's high temperature test in Melbourne, Australia, for the whole vehicle development vehicle factory All at all costs.
3. High-temperature + high-humidity environment durability test, generally carried out in Hainan, the seawater environment will accelerate the corrosion of components, and the durability of the components will withstand the rigorous test. (Ps: There are also important plateau tests for traditional cars, mainly testing engines under low pressure. Performance. Electric vehicles generally do not need to perform this test.)
The better battery pack will promise battery decay during the service life. For example, Weilai ES8 promises to reduce battery capacity by no more than 20% in 300 years and 300,000 kilometers. It is very difficult to do this battery development. Dare to publicly promise that their battery pack endurance test has done a very good level.
