“Recently, Mercedes-Benz officially released the EQA model. On its power battery, this is the first Mercedes-Benz design based on a square-shell battery cell, which is more interesting. Electrek also recently announced a battery photo of Tesla based on CTC (Cell to Chassis, vehicle battery integration). Although it is not very clear, it also updates the progress of the next-generation integrated design. This article does some discussion on these two designs.
Recently, Mercedes-Benz officially released the EQA model. On its power battery, this is the first Mercedes-Benz design based on a square-shell battery cell, which is more interesting. Electrek also recently announced a battery photo of Tesla based on CTC (Cell to Chassis, vehicle battery integration). Although it is not very clear, it also updates the progress of the next-generation integrated design. This article does some discussion on these two designs.
The battery design of Mercedes-Benz EQA
In the original Mercedes-Benz route, the power battery is based on a soft pack. We have also seen the design of the previous generation EQC, and in the new EQA design, the following picture shows it more clearly. The battery system has an energy of 66.5kWh and is divided into five modules, two horizontally, two vertically, and one is placed in the back row. From the perspective of the whole package, the weird waterway design continues, from the pipeline outside the package to the inside of the battery system, and the cooling pipeline input and output for each module.
Figure 1 Module and package design of Mercedes-Benz EQA battery system
Compared with the EQC shown in the figure below, the design ideas of the two are completely the same. The two square shell cells are arranged in two rows, and the arrangement is expanded in one direction. The water-cooling plate and the soft pack are on the upper part. Here, a recessed structure is designed above the pressure relief valve of the battery to perform exhaust treatment.
Remarks: From this point of view, EQC’s soft pack batteries are provided by LG for the European market and CATL for the domestic market; EQA uses square-shell batteries, provided by CATL, and may also be compatible with the design of soft packs in the future, Funeng and CATL The distribution of the amount may change over time, and the EQS is also a square shell. Mercedes-Benz’s 2021 square shell and soft case proportion is worthy of statistics.
Figure 2 The original EQC module
The three German OEMs, Volkswagen, Audi and Porsche, will almost all focus on soft cases in 2020. The Volkswagen brand will introduce square shell batteries in China on a large scale in 2021. As mentioned above, Mercedes-Benz has also started to import square shells from purely using soft cases; while BMW still maintains square shell batteries, and can import more suppliers in the future, the overall pattern is like this. It is said that the follow-up technical direction may also try large cylindrical batteries.
Tesla’s CTC progress
At present, this photo is from Electrek’s exclusive. It shows a CTP solution based on 4680 cylindrical batteries. The photo is a bit vague. The inside of this battery system is somewhat similar to a honeycomb design-first pits are arranged below, and then the batteries are put in. It seems that the water-cooling board and the glue filling process of Model 3 are used here, and roughly the number of cells is about 960 (24 in each row, 40 rows).
Remarks: Let’s roughly calculate it like this. The 21700 cell is 5Ah 1/3C, and the 4680 is 5 times the 21700, corresponding to 25Ah, and the roughly estimated energy is 87.6kWh.
On the side of the battery system, there are many water pipes, which are divided by 20 water-cooled plates, and the whole battery is fixed on the overall structure through the plastic side plate. From the structural point of view, water-cooled plates and glue are used here to achieve structural fixation and heat transfer of nearly 1,000 cells.
Figure 3 Tesla battery CTC
Summary: This evolution of the large module design and CTC design basically broke the direction of the standard modules currently used.