Introduction
Recently, controversy has arisen regarding the 1000-kilometer range and fast-charging capabilities of electric vehicles. However, based on the current situation, battery systems with 100kWh-150kWh capacity will not be widely promoted in the short term. The primary focus in 2021 will be on upgrading the existing 148mm-wide battery cells to the new 220mm-wide cells. In addition, the 60-62kWh LFP battery will serve as the entry-level configuration for both domestic and foreign manufacturers using the 590 module design pack. This can be seen as a low-end solution for PK Volkswagen’s 62kWh battery.
62kWh LFP Solution
Currently, there are several specifications for LFP battery cells, including the original 173mm-wide cells primarily used on buses, cells based on the 148mm-wide format with a capacity of around 130Ah (down from the 177Ah previously available), and the new 220mm-wide cells with a capacity of 157Ah, which are particularly interesting as a new system solution.
Based on high-voltage 5-series cells, the largest capacity for ternary cells is approximately 95kWh at 1C, equivalent to approximately 100kWh at 1/3C. Meanwhile, LFP cells have a capacity of about 62.7kWh at 1C, or 65kWh at 1/3C. By using LFP battery cells for the lower-end market, manufacturers can utilize larger module sizes while maintaining the same cell-size specification to meet the various pack sizes of different automakers.
In terms of pack design, the maximum capacity can support up to 6 double-module and 2 single-module solutions, with over 120+ cells integrated, as shown below.
It should be noted that there are two variations – the 590 double-module and the 590 long-module – the difference between the two being the number of cells within each module. Specifically:
1) For FPC collection, 16 cells use two FPCs, while 32 cells use four FPCs;
2) Both modules use aluminum columns for connection, as shown below;
3) The 16-cell module removes the side plate, while the long module maintains it to support connection.
After adopting the embedded water-cooled plate in the Module l3, a module-integrated water-cooled plate mode is also adopted in this design, as shown in the figure below. This design is applied to all types of battery cells.
Penetration of Platform-based Low-end LFP
With Tesla’s large-scale introduction of LFP, it is inevitable that the Entry Level LFP will be imported into passenger car platforms, but the limited volume of the previously used batteries has restricted the maximum battery energy that LFP can support. As the size of the vehicle’s own battery system is sufficient, this energy will be further increased towards 65 kWh. Therefore, based on the current situation, it can be judged that:
1) LFP batteries will be gradually introduced into platform-based companies starting from June 2021. This low-cost solution is for the purpose of coping with the non-subsidy policy. Due to the relatively large size of the battery shell, it is difficult to meet the energy density requirements under the current plan. However, the cost advantage makes this solution almost as competitive as the three-element subsidy-based solution.
2) Based on the three-element scheme, a 16-single-row and 32-dual-row pattern can be adopted to further increase integration. From the current integration situation, there is no obvious advantage of CTP in this design. I believe that the viability of this design is relatively strong.
3) Currently, the large module solution basically interrupts the automation of the previous module line and pack line. The 32S module has 117 V and 28.4 kWh, which is basically a small module. This branch can derive a design that packages this module into a small pack that is widely applicable.
Conclusion
The current LFP solution is based on mainstream sizes. Therefore, the addition of nail penetration tests and the increase of heat diffusion time to 30 minutes proposed by BYD actually have no difference for the current LFP solution. For strict standards, this may further accelerate the deployment of LFP.
This article is a translation by ChatGPT of a Chinese report from 42HOW. If you have any questions about it, please email bd@42how.com.