Zhiyi Auto Jasper
It's been a while since Xiaomi's technology conference,Su7The heat has gradually decreased a lot,After everyone almost came to their senses,Zhiyi Auto feels that it's time to talk to you about one of the most important technologies of Xiaomi's conference:Cell inversion technology。
The most important battery safety issue related to the tram should not be underestimated. Let's take a look at how Lei Jun expresses the "high-end" of this technology, Xiaomi's official ** gives a good summary of "in extreme cases, quickly release energy downward, to ensure the safety of the passenger compartment to the greatest extent", and Lei Jun called this "the first in the industry".
Zhiyi Automobile also told you before, generally speaking, the battery cells and pressure relief valves in the industry are upright, here the battery cells are actually upright The impact of the upside down is good, mainly the inversion of the pressure relief valve, we can simply understand the pressure relief valve as the "outlet", in the event of extreme situations, toxic gases and open flames will be sprayed directly from the pressure relief valve, and the inversion of the pressure relief valve will allow these to be sprayed directly to the bottom of the car, rather than the body passenger compartment after CTB integration.
Do you want to say that this works? Of course it works. Zhiyi Auto also saw that some bloggers gave an example of a lighter being lit upside down and still burning to the hand when popularizing this matter with everyone, but in fact, this is somewhat inappropriate. Although toxic gases and open flames will extend upwards in the environment, they are fundamentally different from "upright cells" when these directly enter the passenger compartment. When the battery cells are turned upside down, toxic gases and open flames will start to emit from the bottom of the car, and even if they will surround the body, it is much better than directly burning the passenger compartment.
It is useful", "it is stronger than directly burning the passenger compartment" and so on, but this does not mean that it is the embodiment of "safety", it can only be said that it reduces the "injury result" to a certain extent, and the danger that passengers should encounter when fleeing will still be encountered, but it has changed from "the soles of the feet **" to "a circle of fire on the soles of the feet behind the opening door". Moreover, in the event of an extremely dangerous situation, the bottom of the battery pack, that is, the other side of the pressure relief valve, will directly face a huge pressure, and the result of the inversion of the battery cell is to transfer this pressure to the passenger compartment of the body, which is also a safety threat to the passenger compartment, but it is a little better than an open flame directly burning the passenger compartment.
Taken together, it seems to be a little "safer", but it has not solved the fundamental problem of battery pack safety, and it is not Lei Jun's "false propaganda". But what Zhiyi Auto wants to tell everyone is that Lei Jun has a "cognitive gap" here.
Starting with BYD, people have gradually begun to understand CTB technology, which integrates battery packs into the chassis, and has gradually become an important selling point for many new energy vehicle companies. Xiaomi's cell inversion technology is just a little upgrade at the same time as CTB technology, and the main purpose of its cell inversion is not safety, but "space".
Electric vehicles to pursue space, the most important thing to solve is where to put the battery, after all, this is the largest in the whole car, the most occupied volume of the object, and the major brands are grabbing the electric vehicle market, the first war is bound to bring cost reduction, CTB said that the good point is the embodiment of technology, in fact, it is a weapon for car companies to reduce costs, in order to improve the degree of integration, increase the space in the car as much as possible and reduce the overall weight. These theories of security cannot be talked about at all, and what is more important is the pursuit of interests within the scope of national standards. The most important purpose of cell inversion is to reduce the design margin in terms of resistance to deformation and impact of the battery structure design, simply put, on the premise of ensuring "basic safety", take the greatest advantage from the space advantage, and stuff more cells in the same volume of the entire battery pack.
Lei Jun's "poor cognition" is here, saying that the plan to reduce costs is safer, which belongs to the sales method, but what Zhiyi Auto wants to say is "this is not safe". If it's just the problem of "soles of the feet" and "soles of the feet after opening the door" that we talked about earlier, then it's okay, but the battery cells are bound to face bigger problems after they are inverted.
As mentioned earlier, inverted cells are a way to compress the design margin to the limit, but in the field of absolute technology, this kind of "compression" is a more dangerous behavior. The margin of design is not only the margin of space, but also the margin of safety. Absolute technology is difficult to explain, but we can think about when we send express delivery, if we want to send a fragile item, is it after doing the basic anti-shattering measures, put it in the box and find that if there is still open space around, we will stuff some soft things to pad it, and the empty space of the box here is the design margin.
Secondly, the loss of control of the battery cell is a multi-stage process, and the emission of toxic gases is just the most extreme result, and after the cell is inverted, this is not the most extreme result. After the high-temperature flue gas of more than 1000 degrees Celsius is sprayed out from the pressure relief valve, it is not just gone, and there are many smoke will be reflected to the nearby battery cells, and at this time, the inversion of the battery cells will cause the electrolyte to accelerate the eruption, and the materials in the bag will burn more fully, simply put, it is equivalent to pouring a barrel of gasoline on the basis of the upright battery cell.
The above are all extreme cases, even if you don't encounter those, the inversion of the battery cell will also have a lot of reduction on the voltage difference, discharge rate and cell life of the battery in daily life.
In the end, the possible problems of the entire cell inversion technology are basically clear, or that sentence, everything related to the safety of the tram should not be underestimated, and the safety of the battery is still not completely solved, so a sufficiently perfect firewall, fire blanket, aerogel is the most important way to ensure the safety of the passenger compartment, at least on the Xiaomi su7 we have not seen more specific news. The so-called cell inversion is just a poor perception of marketing methods and Lei Jun's fighting, and the industry's first is true, but when it comes to "safer", don't mention it again.
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