Responsibly fill in the hole that was buried when I wrote the skateboard chassis today:
In view of the current form of battery pack, that is, what is CTP, CTC, CTB, CTM, I hope to answer your questions. **Colleagues and car bosses, if there are mistakes, omissions or doubts in the article, we can communicate in the comment area friendly.
Related review: New technology at the Guangzhou Auto Show: an article to understand the "skateboard chassis" Mo Gong popular science.
Before we talk about the structure, we must first figure out what the full name of these English abbreviations is
"c" is the abbreviation of the English "cell", which is commonly known as "battery".
t”—“to”。
p"—"pack", which is generally the whole pack of the battery pack.
c”—“chassis”。
b”—“body”。
m”—“module”。
Together, they are "cell to body", "cell to pack", and so on. So through the above names, you can find that its purpose is to revolve around the battery cell - in the three-electric system of electric vehicles, the battery pack that provides power to the vehicle is the battery pack, and after splitting it layer by layer, the final energy source is the battery cell.
From the structural point of view of electric vehicles, the most efficient and space-saving is undoubtedly to install the battery cells directly inside the body, and the ultimate solution, that is, the mini four-wheel drive car that we all played with boys when we were children, is tightly fitted and does not waste space at all.
Although electric vehicles are similar to mini four-wheel drive vehicles in principle, vehicles and toys are not the product of one dimension, and cars have extremely demanding requirements in terms of use scenarios, speed, performance, safety protection, etc., and the current technical conditions are obviously not simple and rude like mini four-wheel drive cars to stuff two batteries to finish.
Compared with fuel vehicles, although electric vehicles are more flexible in structural space and have better space utilization, they cannot be as quickly replenished as fuel vehicles under existing conditions.
But unfortunately, so far there is still not too much qualitative leap in the battery cell end, that is, there are not too many breakthroughs in energy density, so how to optimize the internal space of the battery package, as much as possible to plug more cells to improve the power, and then increase the mileage, has become the main means of improving the battery life of electric vehicles, so there is a topic we want to talk about today.
Cell-to-module that has been phased out
First of all, looking at the first CTM structure, the basic logic is to combine a certain number of cells into a single module, and then use the series and parallel method through several such modules, and finally output a total positive and negative electrodes, and then become a battery pack.
The parts including but not limited to include: battery cells, modules, end plates, water cooling plates, high-voltage copper bars, battery pack bottom shells, battery pack covers, sealing gaskets, insulation boards, etc. In order to use the full space stack battery as much as possible, and there was no corresponding space and location for high and low voltage components at that time, the battery pack at that time looked strange, and BMS and high and low voltage relays were also piled up in the battery pack, which was quite complex and messy, which was completely inconsistent with the logic of industrial design and commercial mass production.
Contemptible talent, once worked as a battery pack structure design engineer for 1 year, now look at the drawing at that time can not bear to look at the picture, Party A will generally send a 3D scanning of the bottom of the car envelope, we are based on the needs of customers in the limited space design, and the vehicle can be regarded as no communication at all.
To be honest, the CTM structure does not have many advantages, and the only advantage may be that the battery cells can be replaced separately, assuming that there is an abnormality in a certain cell in a module, it can be disassembled and replaced separately, of course, this process is relatively cumbersome - in addition, in today's view, it is almost all disadvantages.
In terms of manufacturing process, the early oil-to-electricity CTM will not use the "high-end" product of cast aluminum, and the steel plate folding stamping will never use too complicated process, and the module is fixed by the stamping beam welded on the screw and the bottom shell, and the rest is basically the assembly line to manually install the module and various connectors, and finally put on the "plastic wrap" on the new factory.
Rest assured, this kind of CTM battery pack is almost extinct in new energy vehicles in 2023, especially in the domestic electric vehicle market, if there is still a similar structure used by any manufacturer, it is likely to be judged to be either a cheap car or a cost-saving.
Ningwang" as the representative of the cell to pack
In 2019, CATL released a new generation of battery technology, also known as CTP. Literally, the core point of CTP technology is that the module design is canceled, and the battery cell is directly combined with the shell, which reduces the use of end plates and separators, and further squeezes the space in the battery pack, making it more integrated.
From the beginning of CATL to the present, the mainstream method is to use steel tape or tape to fix the relatively simple structure of the square battery, and then glue a large piece of battery to the liquid cold plate through the thermal conductive structure glue, at the same time, the process of the bottom shell also abandons the previous folding and welding method of large steel plates, and instead adopts the cast aluminum or aluminum extruded bottom shell that is more in line with mass production and forward design, and limits the battery cell by adding positioning pins or card slots by design.
In the past, due to the existence of modules and the simple process structure and low cost, it was simple and rude to place a separate water cooling plate under each or every 2-4 adjacent modules, and then transfer the water inlet and outlet from the inside to the outside. There is a risk of coolant leakage in the battery pack, which can be completely solved by the current manufacturing process, which is also more efficient than the former.
In fact, "Ning Wang" uses CTP10 is not a pure module-free design, as can be seen from the figure, it is a design that merges the original small module into 3 large modules and 2 medium modules, and there are also aluminum end plates at both ends, so it is still CTM in theory, but in terms of structure, it is indeed much better than the original technology.
And to CTP3After 0 Kirin battery technology, CATL has given a more advanced manufacturing method, which can be said to have become a real module-free design, the battery cell has also been changed from the original upright to the side, and a new cooling scheme has also been adopted between the attached cells, and this set of cold plates also assumes the role of heat insulation, temperature control, buffering and support, and the section is a bit similar to the structure of honeycomb aluminum, and from the structural drawing, the bottom shell also has a corresponding limit to fix the battery, and then become a whole through bonding, which can be said to be 30 vs. 10 is the real CTP, and the visual perception should be more neat and unified.
So far, basically all new energy vehicles have adopted a similar CTP manufacturing method, and the way of cell bonding also leads to the inability to replace a single battery cell in the later stage - if a battery cell in the battery pack fails, the entire battery pack can only be replaced together, and finally violently disassembled and scrapped. This is the answer I got from consulting an engineer from a leading battery manufacturer.
But it is also this structural design that proves that the stability of the current cell performance has long been the same as in the past, and there is basically no problem of a single failure, so there is no need to disassemble and replace it individually, and at the same time, because the stability of the battery cell is improved, it gives the premise that CTP technology can be realized.
A sleek and advanced cell-to-body and a beautiful-looking cell-to-chassis
First of all, the most essential difference between CTB and CTC lies in the word "chassis". In order to avoid being misled, let's start with the conclusion: CTC has not yet had a mature commercial model in the passenger car field.
As for the CTC claimed by some manufacturers, I understand that it is just to create differentiation, memory points and word-making gimmicks in commercial operations. Because the inevitable condition of a true CTC is the "chassis" – that is, the battery cells are directly combined with the chassis to form a whole.
But the problem is that the vast majority of passenger cars are currently "load-bearing bodies", and there is no so-called "chassis" at all. Because only the non-load-bearing body, that is, the upper body can still be driven even if the upper body is removed, can it be called a real "chassis".
Of course, as a car media, we often use the word "chassis" to evaluate the handling and stability of the vehicle when evaluating the passenger car with a load-bearing body, mainly to facilitate everyone's understanding. But in fact, what you need to understand is that the "load-bearing body", that is, the body structure of most passenger models on the market, has no real "chassis".
Therefore, in the load-bearing body, the most correct statement should be CTB, so you can also understand that the CTC and CTB that can be seen now are actually the same thing. And if the "skateboard chassis" of the non-load-bearing body is really made, it can be regarded as CTC.
The biggest difference between the CTB and the CTP mentioned above is also the integrity of the battery and compartment seal. The CTP needs to keep the upper and lower shells of the battery pack intact, and the compartment and battery are each responsible for sealing independentlyThe CTB is to combine the battery cover and the underbody into one, so one of the batteries and the underbody must be incomplete.
There is nothing to explain about the separate complete compartment and battery sealing separately, everyone understands. I've tried to describe the difference between the "incomplete" seals: either the battery is sealed through the underbody (BYD seal), or everyone sits on the battery pack and drives (Tesla Model Y).
The advantage of CTB is that the battery pack system is incorporated into the vehicle development process, and the general layout, body, suspension and power battery departments need to work together to consider the impact of battery design on other parts at the early stage of platform and model development, unlike the previous CTP and CTM, which can be changed later.
In this way, the battery pack system has officially entered the strategic layout of the whole vehicle, which has improved the unity, rationality, structural design, ergonomics and other aspects of the vehicle to a considerable extent. At the same time, the design of the upper cover or body floor is canceled, which can also release the Z-direction space of the whole vehicle, which can increase the height by more than 10mm.
This also explains why when I drove the BYD seal, I felt that the ergonomics of that car were very close to the traditional fuel car - the proximity to the traditional fuel car here is definitely a compliment, because of the battery structure, the comfort of the electric car in the past few years was significantly worse than that of the fuel car - at the same time, coupled with BYD's blade battery technology, the thickness of the battery package was further reduced, and finally a fairly excellent front and rear ergonomic experience was obtained.
Again, if you don't use CTB technology, you may not have much perception on an SUV, but if you put it on a sedan, you can immediately notice the difference (refer to the difference in the ergonomic comfort of the rear row of similar fuel models in NIO ET5 and ET7).
In addition, compared with CTM, CTP and CTB also provide considerable advantages in the structural strength of the whole vehicle, especially in torsional rigidity. The CTM is fixed by mechanical screws between the module and the bottom shell, and the mold components do not participate in the force conduction, so they cannot provide more help in the torsion process of the vehicleBoth CTP and CTB are bonded between the battery cell and the bottom shell.
Tesla's CTB is even more exaggerated, the whole bag is filled with pink material for insulation and bonding, and the strength is quite reliable, which can be understood as a large iron plate stuffed under the car, and the torsional rigidity does not take offSo you can find that the current electric vehicles, but all using CTB and CTP technology, the torsional rigidity is casually more than 40,000 N·m deg, which is the performance that has only been achieved in many high-performance cars and ultra-luxury models in the past.
For example, when the seal was in the propaganda before, it was said that the torsional stiffness was comparable to that of Rolls-Royce, and from this point of view, this is not an exaggeration.
In addition, there is also a so-called "MTB", that is, "module to body", which adopts the method of fixing the battery cell module, and then cancels the battery cover and then installs it on the vehicle, which is currently the solution adopted by Leapmotor.
Mo Gong concluded. All in all, each design has its own characteristics, but it's all about squeezing as much space as possible and cramming more batteries. Considering the battery pack and the body in the design and manufacturing can also reduce the use of parts, improve the efficiency of mass production, reduce costs, and improve vehicle performance.
When ordinary users buy a car, it is actually easy to be misled by the official rhetoric, especially for those untraceable percentage data (similar to the body frame to increase the torsional rigidity by xx%, the capacity to increase by xx%, etc., the percentage comparison objects are unknown, equivalent to only one empty data), I don't think there is too much importance to these number games, because in the end, we still have to use feelings to speak.
After all, no matter how fancy it is, if it doesn't work to drive, it's uncomfortable to sit up, and it's troublesome to maintain, then what should be eliminated by the times will naturally be eliminated.
Text: Mo Yilong.
Figure Network.