Following the trail of CATL’s “Tesla Module” Solution (Part I)
Although there has not been any official statements, based on the available information, the following conclusions can be made on CATL’s battery pack solution for Tesla:
a) It will be installed in Model 3 (M3) base model
b) Cell will be LFP prismatic cell
c) Four big modules will be used
CATL has to provide Tesla with a sufficiently economic and functional product without adjusting size and form of the outer battery pack casing. Following are the most feasible module solutions (solution with output poles on both ends will not be discussed for now):
a) Similar to current M3 modules: 4 modules — 2 big, 2 small — which are placed on the existing positions on M3.
b) Similar to the potential future modules of the M3 base model: 4 modules of equal size, which are still placed along the car body axis.
As for cell type, “thick and fat” cells could be used. This solution might require for the cell to be placed on its side, so in this manner output pole of the cell is directed towards left or right. Another type of cell that could be used is “short and slim” cell, similar to the cells in BMW 5. In this solution, the cell is placed on its back, while output pole is directed upwards.
Based on CATL patents, general design of the module configuration of the latter solution is as follows: CCS of all electrical connection systems is made in z direction. Based on the integration method of battery pack, module might not have top cover, which smells a bit like CTP.
This type of pack design has fully exploited the structure of central longeron. Busbar connection on the front of the module does not have to be adjusted, while rear one needs to be adjusted.
Another solution is in the form of entire module, as shown below, where each module is separately affixed to the lower casing.
This solution is even more compact in space utilization as it abandons original longeron and instead re-uses beams on both sides for affixing. In reality, its feasibility is not high and the solution should have more variants.
As for short and fat cells, based on patents, the following solution appears:
Cell’s positive pole is placed facing inside (judging from the point of thermal runaway protection, it is more reasonable that it faces outside, which indicates that there are other considerations as to why this was done. perhaps it was for electrical connection integration).
The solution affixes two longerons, that might have originally been on two sides, onto module. There is a certain integration on the structure between the two modules. On this basis, the two modules on both sides can be made smaller.
If we compare the solutions, the first one has more advantages. No matter which design idea is used, we can see that, in cooperation with Tesla, CATL absorbed M3’s big module design strategy and constructed appropriate prismatic cell, vertically deployed big module or CTP solution that goes along the axis of the pack. This might be yet another big module product promoted for M3 after BMW JOB 355 module, VW MEB 590 module.
From this perspective, CATL seems to be the great assembler, that only needs to see in which direction are the Chinese auto companies headed.
Source: https://www.gg-lb.com/art-40365.html
Published by: GGII
Author: 知化汽车 Blog
Following the trail of CATL’s “Tesla Module” Solution (Part II)
There are talks in the industry of new developments in cooperation between CATL and Tesla.
This 130 Ah LFP cell is the most talked about. Some of the friends that I talked to speculate that this is one of the cells that CATL offered to Tesla (probably one of the products). Basic data is as follows:
Based on this, we can conclude that cell’s specific energy is 120 Ah x 3.2 V/2.3 kg=180.87 Wh/kg.
In the previous part, we have discussed solutions with two types of cells. We have not discussed the cell that has battery output tabs on both sides, and 130 Ah belongs to this type. Below we will look into that.
We already know that the size of Tesla Model 3 Long Range module and pack are respectively:
Voltage and power of Panasonic and LG pack for M3 base model are:
Panasonic version: ”355.2V/148.8Ah”, ca. 52.85kWh
LG version: ”355.2V/145.7Ah”, ca. 51.75kWh
The following problem is rather easy. Based on existing battery pack sizes and cells at our disposal, design the best solution.
First, we need to comply with voltage requirement. The voltage of Panasonic and LG version is 355.2 V. If we want to reach that category, 130 Ah cell needs 355.2/3.2=111 cells. And total power of 111 cells is 111 x 3.2 x 130 = 46.2 kWh. This power is a bit problematic as it trails around 6 kWh behind Panasonic’s M3 base model and its 52.85 kWh as well as LG’s M3 base model and its 51.75 kWh.
To reach equal power, voltage needs to be increased to 400 V, i.e. 400 x 130=52 kWh. Number of cells is then 400/3.2=125. This is voltage platform in Model S, and I do not know if it can be applied to M3.
First solution is in line with Tesla’s original deployment of big modules. Since 360 mm long cell is bigger than 323 mm wide original module. Arrangement of 360x4=1440 is almost as wide as M3 battery pack. Arrangement is a bit difficult, especially since electrical connection needs to be performed on both ends of cell.
This configuration, where each module can be similar — all of them with 31 cells, total of 124 cells) — can basically meet voltage and power requirements. But, as far as length goes, 31x33=1,023 mm is a lot shorter compared to the original module of close to 1.9 m. In this way, almost half of the space is wasted.
If this configuration is to use entire space, solution that combines two big modules and two small modules can be adopted. Small module would be 2P27S with length at 1,782 mm and big module would be 2P28S with length at 1,848 mm. Total voltage is 3.2x110=352 V and total power is 352x260=91.52 kWh. Now that is a top notch configuration.
The biggest issue is whether there is enough space horizontally. There is a chance that this solution might use CTP. Also, vertical reinforcements cannot be added, so how to guarantee vertical stiffness and strength of the chassis?
Second solution with vertical arrangement.
We have same limitations. Based on base model, if we use 352 V voltage, power is still below 52 kWh. If we use 400 V voltage platform and cells in 1 parallel, then width is 33x25/1,440=57.3%. This solution also wastes space. If we use top model and 352 V voltage, power is at ca. 90 kWh. The advantage of the solution is that it can pretty easily use Tesla’s existing high-voltage connection on the output position.
Based on this cell, I cannot see any convenient solutions. Also, we all believe CATL will supply base models, but this cell really looks like it is meant for top model. Another type of cell might be necessary, if we want to conveniently use original casing structure.
Judging from battery pack design, it looks like CATL is simultaneously offering Tesla with CTP and big module solutions, but CATL seems to want more than￥300 K models.
Source: https://www.gg-lb.com/art-40365.html
Published by: GGII
Author: 知化汽车 Blog
