A brief analysis of the design trend of power battery modules in 2021

In recent days, the 1,000km range and fast charging have become the focus of industry debate, but in fact, according to the current situation, this type of 100kWh-150kWh battery system will not be widely promoted in the market in the short term. The main trend in 2021 is to move from the original 148mm width battery cell to the 220mm width battery cell, and the 60-62kWh LFP battery is a low-end configuration based on the 590 module design Pack at home and abroad. This can be used as a low-end solution to compete with Volkswagen's 62kWh and deserves our attention.

62kWh LFP solution

LFP cells currently have several specifications. One is the original 173mm width system, which is mainly used in electric buses. The other is based on 148mm cells. This type of cell and the current 148mm 177Ah cell are made into a 130Ah specification. The new 220mm 157Ah cell is indeed very interesting as a new system solution. The corresponding high-voltage 5-series cell capacity is about 242Ah.

The capacity of ternary battery is about 95kWh, which is about 100kWh at 1C based on 1/3C. LFP is 62.7kWh at 1C, and about 65kWh at 1/3C. Currently, a model has been formed that uses LFP batteries to focus on the low-end market, and adopts battery cells of the same size and specifications to make large modules to meet the pack size of different car companies.

Table 1 Main existing specifications:

From the perspective of the Pack, as shown in the figure below, the filling area can support up to 6 dual-module + 2 single-module solutions, and can support the integration of more than 120 battery cells.

Figure 1 Comparison between LFP scheme and ternary scheme

It should be noted that there are two variants here - 590 dual module and 590 long module. The difference between the two is mainly based on the number of cells in the module:

1) FPC collection, 16 cells use two FPCs; while 32 cells are different and use 4 FPCs;

2) Both modules are connected by aluminum bars, as shown in the figure below;

3) The 16-cell battery has no side panels, while the long module retains the side panels for connection.

Figure 2 Improved 590 design (double spelling)

Figure 3 Long module based on double-row cells, the number can reach 32

After the module-embedded water cooling plate adopted in Tesla Model 3, the module-integrated water cooling plate mode was also adopted in this design, as shown in the figure below. This design is applied to all types of battery cells.

Figure 4 Embedded water cooling plate design for large module design

Penetration of platform-based low-end LFP

Since Tesla started to introduce LFP on a large scale, the introduction of LFP in the entry-level passenger car platform is bound to be a trend. The only difference is that the battery volume is limited, which limits the maximum cell energy supported by LFP. As the size of the battery system provided by the vehicle itself is sufficient, this energy will be further increased to 65kWh. So based on the current situation:

1) For enterprises that introduce platforms, LFP batteries will be gradually introduced in June 2021. This low-cost solution is for electric vehicles without subsidies. Due to the large battery shell, it is difficult to meet the energy density requirements under the current solution. However, the cost advantage makes this solution not much different from the subsidy-based ternary solution;

2) Based on the ternary solution, a mode of 16 single rows and 32 double rows can be adopted to further increase the integration. From the current integration situation, under this design, CTP does not have a clear advantage. I believe that this design has strong vitality.

3) The current large module solution basically interrupts the automation of the previous module line and pack line. The 32S module has a voltage of 117V and a power of 28.4kWh, which is basically a small module. Based on this branch, a design that can seal this module into a universal small pack can be derived.

Summary: The current LFP solution is based on mainstream sizes. Therefore, BYD's proposal to add a needle puncture test and increase the heat diffusion time to 30 minutes actually makes no difference to the current LFP solution. The strict requirements of the standard may further accelerate the deployment of LFP.