Analysis of BYD's battery integration solution: pursuit of maximum value

We have previously introduced BYD's latest blade battery, and today we will take a look at BYD's battery integration solution. First, let's sort out the use of BYD batteries in 2019. According to the current situation, we can see that there are three stages - single-row modules under the e-platform, cost optimization solutions after the e-platform, and blade battery grouping. These three types of modules are still BYD's current main forms.

1) BYD's battery cell situation

From 2018 to 2019, BYD spent a lot of effort on ternary cells, using 173*120*20mm cells for PHEV, 173*122.5*50mm cells for passenger cars, and LFP cells (415*148*60mm) for special vehicles and commercial vehicles. The latter is the prototype and reference benchmark of the blade-type cell in terms of length and width, and the main number of vehicles is based on the BEV ternary cell in the middle.

Note: BYD's total installed capacity is approximately 12.323GWh

Figure 1 Overview of BYD battery cell installations in 2019

In BYD's previously planned technology route, this 173-width battery cell was produced in the form of a standard module, which was intended for both external supply and larger quantities. BYD adjusted the chemical system and increased the capacity to form different products under the same battery cell size.

Figure 2 Standard module solution, capacity evolution

2) Design based on module simplification

Since the ternary battery cell will continue to advance, the next step in the evolution of the standard module is to improve the integration efficiency of the battery pack and simplify the structure of the battery system tray. There are two comparisons. The main one is that the previous tray design required the setting of several crossbeams and longitudinal beams, and the existence of the beams limited the volume utilization of the module layout; the fixation of the battery module to the bottom tray requires the use of many fasteners; the structure of this tray also limits the manufacturing process; and there is also the process of dividing into multiple modules during the module assembly process. Therefore, the trend of this part of the evolution is to arrange the battery cells and trays continuously, as shown below. This method is more idealized through the reinforcement between them. In fact, a lot of reinforcement design and bottom thermal conductive glue are required for fixation.

Note: Some of the measures we can see here include: the tray is made into a downwardly concave cavity, a thermally conductive insulation layer is provided between the single battery and the upper cover, and a thermally conductive structural adhesive is used on the bottom surface. We will basically cover all of these later. 

Figure 3 Existing battery cell grouping method

3) Blade-type battery module design

The prototype of the blade module can be traced back to the bus with wound battery cells. It has a size of 415*148*60mm and a double-layer layout. We can buy it on Taobao.

Figure 4 Module design of the original bus battery cell

The latest blade cell design is likely to be a square disc technology, similar to the previous honeycomb method, with tabs on both ends of the soft pack and a square aluminum shell rigidity design to simplify the structure. The advantage of the horizontal design is that the soft pack is very thin, the heat dissipation effect is good, and the structural strength relies on itself to achieve support.

Figure 5 Module design of blade battery

Different from the grouped design of battery cells for buses, this time a single row of batteries is directly laid on the pallet. The two ends of the battery cell are fixed on the end plates, and the battery cell is supported by the frame at both ends. Support blocks and buffer side panels are designed on the pallet to provide pre-tightening force for the battery cell.

summary:

According to the information currently known, if BYD really adopts the soft-pack lamination process to make thin square shell batteries, the process requirements will be very high if it uses very long lamination technology. Next, it will force soft-pack companies to consider whether they can bypass the aluminum-plastic film issue and use a rectangular shell to make it slightly thicker. If this path works, after the iX3 is released, we can expect a laminated square shell with a length of more than 300, which is more valuable than thickening in the thickness direction.