Recently Mercedes-Benz began to promote its next-generation electric drive and battery design in Europe, which is also a complete change from 400V to 800V. According to the time point we saw before in 2023-2024, it is necessary to have a great change in the entire three-electric system, so the endurance measurement in the first real road conditions in Europe is also vigorously promoted (100kWh battery has 15% of the remaining power after driving 1008km on a single charge, and it can run about 140km).
Note: The concept car can not consider the manufacturability, and go all out to sprint for the mileage performance
Inside this battery system we can see a lot of interesting things:
● Mercedes-Benz will start from the module design to CTP, so how to use mercedes-benz soft pack batteries in the end, how long, and the sub-block design seen before, 6 large battery block design compatibility may become an inevitable choice.
● In terms of material system, Mercedes-Benz is divided into prior art, EQXX technology (graphite changed to silicon carbon) and solid-state batteries, which are described in detail in ESG's conference materials.
● 400V switched to 900V, the capacity of the battery becomes smaller, and the width of the single battery cell also becomes smaller. All european car companies use batteries with a thickness of less than 40mm, and this time the switching capacity is mainly achieved from the width to smaller.
● Cooling design: Here from the independent water-cooled plate (and the entire housing thermal isolation) to the integration of the water-cooled plate and the housing, but the heating method may need to be solved by high-frequency mode, so this change may also revolve around the availability of SiC semiconductors, which is more suitable for high-frequency switching hooks than IGBTs.
● Of course, in terms of battery design, Mercedes-Benz has given the battery cell the most space, and the electrical components resemble a box lid on it.
Let's focus on the iteration of this battery system.
Figure 1. Mercedes-Benz is compared with the battery pack of EQS, mainly from the volume and energy to start the comparison
Part 1 Battery systems and drive systems
Vision EQXX power battery system, from the Pack level has a volume energy density of 400Wh/L (200Wh/kg energy density), and then we can calculate according to 100kWh, that is, corresponding to 250L. If you take it apart and decompose it according to length, width and height, it is estimated to be 2000x1260x110mm, which is similar to this capacity, and it is indeed seen that the size of this package has been greatly adjusted. Therefore, the volume is reduced by 50% compared with the previous EQS battery pack, and the weight is also reduced by 30%, which is 495kg. The operating voltage of the battery pack is above 900V.
Figure 2. Mercedes-Benz switched from EQS to EQXX
According to the above figure, I counted the cells in the module, which is equal to 2 18-string modules side by side. Then the beam of the entire pallet is cancelled here, and then the structural constraints are provided by the side plates and end plates of the 6 battery blocks, and the structural strength is achieved together with the entire pallet.
From a logical point of view, from the beginning of BYD's blade to the Kirin battery of the Ningde era, the compatibility of the entire tray will be very strong in the future, all of which are flat-bottomed and can lead to the direction of high-pressure cast aluminum.
Figure 3. Battery system battery configuration of Mercedes-Benz
Now in the era of electric vehicles, whether it is cooling or heating, it has become a science of manifestation, and the thermal management engineers of the whole vehicle need to achieve the needs of the whole vehicle system with minimal energy by coordinating different modes from the whole vehicle. Here it is necessary to abandon some of the needs of the original battery engineer and simplify the battery tray and cooling plate. Of course, the most important thing is that an active vent is set up here, which can be controlled by switching to adjust whether the air can enter the battery housing, which is particularly fun.
Figure 4. Thermal management iteration from EQS to EQXX for Mercedes-Benz
According to a predecessor of Eaton XJTLU, the electrical system of EQXX is likely to change the way there were multiple contactors before iteratively, and it may be that Mercedes-Benz engineers really can't stand the 400V two large modules and then parallel in the need to deal with the positive and negative poles, by using circuit breakers, you can completely simplify the design of the EQS below, all of a sudden the space is particularly small.
Figure 5. The high voltage electrical design of the EQS is indeed too complicated
In terms of power system, Mercedes-Benz also uses a very characteristic cooling method, of course, I understand that air cooling is a mode, compared to the efficiency of water cooling, this mode is more like trying on the basis of SiC's heat resistance, and non-limit mode, driving a speed of 60-80 kilometers per hour, air cooling is indeed OK.
Figure 6. Cooling of mercedes-benz powertrain
Part 2 Mercedes-Benz's next-generation battery
In ESG, some things are revealed, mainly the direction of Mercedes-Benz's research. The promotion of lithium iron phosphate currently led by CATL and BYD in Asia will begin to land globally in 2024, so the previous cobalt-free short-term realization is the use of this iron lithium.
Figure 7. Mercedes-Benz's chemical system iterations starting in 2024-2025
From the perspective of investment rhythm, 2026-2028 is probably the time when everyone is more serious about solid-state batteries, and these investments are still in the process of solving problems from laboratory cell development to manufacturing level.
Figure 8. Investment in solid-state batteries
Summary: In the past few years, the chemical system of batteries has not undergone major innovations; innovations in the field of engineering and manufacturing have brought about rapid cost reductions. But with the increase in global penetration, the price increase of raw materials may take 1-2 years to absorb, I feel that the battery engineering design in the past two years has reached a bottleneck, and it is getting simpler and simpler, the structural engineers of the battery, you are very dangerous ^_^.