Power batteries are a critical component of electric vehicles. Currently, most automakers rely on external procurement for their power batteries and BMS systems. This presents automakers with a significant challenge: managing their suppliers. The core issue is ensuring consistency across battery-related products from different suppliers, including hardware consolidation and modularization, as well as software algorithms and data analysis. This management directly impacts battery safety, durability, and performance, thus affecting the safe and stable operation of electric vehicles and significantly influencing after-sales maintenance. This article explores automakers' management of power battery systems from the perspective of multi-supplier product management, particularly examining the importance and impact of this issue throughout the entire vehicle lifecycle.
Part 1: Battery Supply Cases for Two Types of Automakers
Let's look at two typical cases: foreign companies choose General Motors, and domestic companies choose BAIC.
1) General Motors
General Motors has conducted numerous mass production trials of lithium-ion battery systems, exploring various technological approaches. As shown in Figure 1, GM's electric vehicles utilize different battery systems paired with various battery cells, as shown in Figure 2.
In fact, managing these battery systems with different specifications and configurations is quite a troublesome thing for GM, because the differences between various battery cells are very large. Fortunately, each model under GM is made by a fixed supplier.
Figure 2 shows different suppliers and different types of batteries to meet different needs.
A closer look at the battery management system (BMS) configuration reveals an even more complex picture, encompassing both a fully integrated BMS controller and distributed BMS systems. GM's entire electrification team utilizes the company's electrical engineering (EE) hardware resources for battery electronics hardware development, then outsources production to external suppliers. GM focuses its main efforts on the core algorithms of the BMS. We can see that the basic functions of the power battery system are well-defined, while GM takes the lead in configuring certain functions, especially the core ones, as shown in Table 2. In this process, the control algorithm thresholds adjusted based on battery life estimation are crucial for ensuring the after-sales performance of the entire powertrain system.
Overall, GM previously considered issues more in terms of individual models, with each model having its own relatively personalized power battery system. As a result, various systems were configured based on its various models. The entire electrification business did not consider merging and modularizing the hardware, but took many measures in terms of software to ensure the safety performance and lifespan of the batteries.
2) BAIC New Energy
There's a reason why domestic companies use BAIC as an example.
BAIC's battery systems are all designed for pure electric systems.
The battery cell specifications vary greatly among BAIC's various models, and the suppliers are also completely different.
BAIC's battery management system is also developed and supplied by different manufacturers.
Of course, the assembly process of the power battery system in BAIC New Energy vehicles is also quite complex. To meet the requirements of different battery modules, as shown in Figure 4, BAIC specifically designed a single mounting plate to fix the sub-modules and main module of the BMS. By purchasing hardware designs and then transferring them, BAIC overlays its own configurations for different battery systems on top of the underlying software to achieve multi-supplier, multi-system management. We do not know how BAIC, through the design of the thermal management system and the algorithm design of the BMS management system, successfully achieved the switching and management of multiple suppliers for a single vehicle series/model, thereby meeting the various personalized needs of different models. Whether the power battery system can be scientifically and stably managed, especially how to achieve consistent management when there are many suppliers, is related to the performance of the electric vehicles under the automaker's brand, and also involves after-sales and maintenance costs.
Figure 3 Supplier Breakdown of BAIC New Energy Battery Systems
Figure 4 Schematic diagram of BAIC's distributed battery management system
Figure 5 shows that the initial accumulation of the entire software and hardware was achieved through external licensing.
Part Two: After-sales Service and Failure Rate
1) Battery life estimation
From a purely power perspective, our ultimate goal is to ensure the entire battery system safely survives the warranty period. Battery system design needs to consider the durability of each component under various usage conditions and environments, including operating time, mileage, and different usage scenarios. There are two key indicators for ensuring the safety and durability of a battery system:
Test data of individual battery cells/systems in the laboratory
Battery system performance in real-world scenarios under set cycle conditions
For these two major data sources, a series of models need to be built to continuously correct the standard lifespan data, and then the entire data needs to be verified against deviations under various conditions. Although this is an offline estimation process, it also requires differentiated configuration of battery lifespan within the BMS. From this perspective, configuring different performance parameter controls for different suppliers is extremely difficult, and considering lifespan and durability, this is essentially not a practical approach.
Figure 6 Battery life estimation
2) The lifespan design and failure rate of the BMS (Battery Management System) itself.
From the perspective of the battery management system, its actual operating time is relatively long:
1) Battery management unit operating time, mainly the time the vehicle spends while in motion.
2) Battery management unit charging time: Divided into fast charging and slow charging, with slow charging taking longer.
3) Battery Management System Standby Time: The time the vehicle spends on the bus, or the time it spends operating in a special mode.
4) Non-running time: hibernation state
Therefore, the overall operating time of BMS system hardware is quite long. If we look at a car manufacturer's database, various quality issues related to the BMS management system are among the top after-sales problems. Therefore, it is crucial to carefully evaluate the failure rate of the entire hardware design to assess the resulting after-sales costs. For car manufacturers, this is not just about controlling the powertrain software algorithm; it's also about how and to what extent they will provide spare parts if the BMS malfunctions at the end of the product's lifespan. Furthermore, the software control characteristics of the BMS directly affect the lifespan and failure rate of relays and other related electrical components.
Summary of the whole text
1) From both hardware and software perspectives, the battery management system is a core component of the after-sales cost of electric vehicles. It not only involves a large number of modifications to the vehicle's power system and the setting of DTC and safety features, but also affects the after-sales issues in large quantities later on.
2) The technology of the battery management system needs to be interpreted from various aspects, not only the accuracy and the advancement of the algorithm, but also the quality level, durability and rationality of the component itself.
