How is the battery full-package thermal out of control? Take the experiment to see the conduction mechanism inside

著者：Iflowpower – Fornitur Portable Power Station

Researching the whole package thermal out-of control experiment is a cost-effective, the cost of the whole package, the detection voltage, temperature experimental equipment is a lot of expenses, especially large-capacity battery and module sample (Taobao Some) are not very good, so many researchers are important as the case of 1865021700. Recently, there is a very interesting case. SHANGGAO, Tsinghua University Automotive Safety and Energy Saving National Key Laboratory, which discloses an experimental package and some experimental data in the article "ExperimentalstudyonModule-propagationinabatteryPack", today we come to see Look at this data and phenomenon.

Remarks: I took out the temperature and event parameters of the article, and I can see the original text. 1) The parameters of the experiment object and the construction of this battery pack are a joint study, supplied by car companies, the entire configuration 13KWH, group 96s1p, using 8 VDA's PHEV2 module, two-layer structure, 4 modules in the upper and lower layers. The purpose of this test is to choose a layer of excitation single-battery thermal out-of control module under the bottom, then carefully analyze the process of evaluating the heat out of control of the whole package.

As shown in the figure below, the temperature sensor is added, and the pressure of the module is smaller, only the external simple fixture is used. The pressure and constraints of the actual battery module will have a small impact on the expansion of the battery, and there will be a difference in experimental construction. In this PHEV battery system, the selected module is marked as DUT, and the object we observe is the left module and upper module of the module, and the right side has some physical partitions, the whole The spread of spreads is relatively slow.

The entire experiment process of the battery system can be divided into, the beginning is important to perform thermal spread in the selected DUT module, the duration is about 40 minutes, then at the next 10 minutes, the left side adjacent and the upper module begins. A very fast thermal spread, finally expanded into the burning of the entire battery system. 2) A researchers have made a lot of work in a single module, and the process has established a more detailed model and mechanism of this process.

Here is just further describing some phenomena. DUT module, heat loss of control, I re-finish: Yellow line is the temperature of the module adjacent to the excitation battery, the gray line is the temperature before the heat loss, the blue line is the battery Time of thermal out-of control. That is, after the valve is actually opened during the thermal out-of-control process, the surface temperature of the battery is between 400 ° C and 550 ° C, and the average temperature is 495 ° C; the surface temperature of the die is between 100 ° C to 200 ° C.

The average temperature is 144 ° C, which occurs heat out of control. In the module here, the heat insulating material is added, as shown below, the overall result is transmitted to the second module after 60 minutes. Remarks: This surface temperature is actually inaccurate, and it will be analyzed later.

3) The second module above the thermal displacement propagation of adjacent modules is a thermal displacement of chain after 66 minutes. The third module has problems after 68 minutes, and this time is baked at high temperatures. The thermal out of control of the module is completed in 10 minutes.

As shown in the figure below, the process of the entire thermal out of control under certain conditions is disorderly, and the spray valve flame is directly baked above the water cooled plate above. Remarks: We can see that the ambient temperature is actually influential to the thermal failure of the electrical cell in the module, and the direct flame and smoke are inherent, even if there is a water-cooled board, the final result will also make the battery heat out of control. If you are interested, we can see this temperature difference is there, especially some of the following considerations: ● Adjacent modules: the speed of adjacent modules, because there is a bus bar connected directly between the modules, make When the temperature of this group is very low, it will open the valve, even the temperature has not yet arrived in our expected temperature; Hot design, the temperature of this one of the core valve directly directly towards the metal support structure and the water-cooled plate, the final result is to absorb a lot of heat, which is very uniform, so that in the case where the surface temperature is not high, it will also I have opened the valve very early; this is the temperature mutation point of grabbing, that is, the temperature of the surface of the surface of the battery is out of control.

In general, NCM111 is still very good, 523 is going to be discounted, 811 is more discount. So actually, if we want to use the temperature sensor of the module to grasp the temperature changes, there are some difficulties, the design of NTC is due to the cause of flue gas during this process, or if it should be not in time, it is already damaged, it is necessary to carefully Considering how NTC is handled under this destructive condition, I feel a feasible approach, it may be a special type of NTC such as a similar sensing line to deal with this special temperature collection. I also mentioned before this.

Summary: We are completely controlled by reasonable layout in such 37ah (164WH / kg and limited capacity, and 1P), which can completely control the process of the entire thermal out-of-control spread, but our development is pursuit Energy density, pursue volume utilization, which causes sufficient gap, lose sufficient buffer space, is still a balance, how to make the battery not spread within a range. .