How does BMS design according to Musk's first principles?

The existing BMS systems primarily follow a centralized or second-level centralized architecture. In the single-string module state, the BMS and battery are completely separated, which makes technical support challenging. This results in a weakly coupled BMS, resembling a distributed architecture. In essence, it is a non-customized, multi-level standard component system. Musk’s first principles thinking became widely known with the birth of Tesla. Although Tesla’s vehicle design followed this principle and inspired domestic manufacturers, the BMS—once highly respected in the industry—did not adhere to the same logic. As a result, issues within battery packs plagued the entire industry. Currently, the main challenges for domestic new energy vehicles still revolve around the battery. These include: 1) degraded battery performance or inability to release power (some batteries have charge, while others do not), leading to reduced range; 2) inaccurate battery power measurement, making remaining mileage prediction unreliable; 3) high workload in battery pack production and maintenance; 4) difficulties in repurposing decommissioned batteries. The first two issues relate to battery/BMS performance, while the latter two stem from the BMS-battery integration architecture, essentially the circuit topology of the BMS. Some may wonder why Tesla’s battery packs seem to avoid these problems. One reason is the battery performance itself. Tesla’s batteries come from Panasonic as custom-made units, offering high consistency. Combined with large battery capacity, the Model S can drive at 45 mph on highways for up to 408 miles. While the chance of a typical customer running out of power is low, battery inconsistency has minimal impact, allowing Tesla to use passive balancing. This is partly due to its luxury positioning—cost is less of a concern, ensuring most users experience full range without issues. Domestically, cost constraints limit battery performance and capacity compared to Tesla. Additionally, many companies have learned from Tesla's past mistakes, trying to avoid similar pitfalls. From an industry perspective, Tesla is more than just an electric car company—it operates like Apple’s vertically integrated system. By using thousands of 18650 cells, Tesla had no reference model, forcing it to develop a fully customized BMS that was deeply integrated with the battery pack. Its unique thermal management system also contributed to superior reliability. Regarding battery ladder utilization, Tesla is not just an electric car company but also an energy company. After acquiring SolarCity in 2016, Tesla became the world’s only vertically integrated energy company, offering end-to-end clean energy solutions—from batteries and electric vehicles to Powerwall and solar roofs. This closed-loop system suggests Tesla is working on solving the issue of battery reuse within its ecosystem. Recently, the "Interim Measures for the Management of Recycling and Utilization of Power Batteries for New Energy Vehicles" were issued, officially addressing the problem of retired battery reuse. With large-scale decommissioning starting this year, it is estimated that by 2020, over 24 GWh will be retired. However, the industry lacks preparation, mainly due to insufficient technical capabilities and poor lifecycle management. The key lies in the BMS. When retired batteries are reorganized, the original BMS is separated, making previous data useless. This leads to time-consuming recalibration, which is impractical at scale. Even with a battery coding system, data transfer may lag behind ownership changes. Moreover, due to the strong coupling between BMS and battery packs, a new BMS must be customized after reorganization, which is costly and impractical for companies aiming to reuse batteries. Hence, it is often more economical to replace them with new modules. Since Musk has successfully applied first principles in multiple ventures—including Tesla, SpaceX, and even the recent Falcon rocket recovery—we should consider learning from his approach. How should BMS be designed according to first principles? First, the core of first principles is to find a positive solution by logically deducing from basic conditions, rather than relying on existing comparisons or experiences. For example, when lithium-ion battery prices were $600/kWh, Musk calculated that raw materials could be purchased for only $80/kWh, leading to the decision to build a battery factory in 2013. So, what are the fundamental conditions for BMS today? First, it must perform routine functions such as data detection and capacity balancing. Second, it must enable full lifecycle management, handling changes in battery shape and performance parameters. The first condition depends on the second, meaning that if full lifecycle management is achieved, the functional requirements are naturally satisfied. Thus, architectural design becomes the primary focus. Where should disassembly and reorganization occur? Ideally, at the cell level, but this is too costly. Disassembling to the single-string module (a large-capacity battery with parallel cells) seems more practical. Feasible conditions include: 1) local storage of SOC/SOH data for each module, requiring BMS components to be integrated; 2) modules with similar SOH and SOC can be quickly assembled into new packs without manual calibration. Current BMS systems are centralized or second-level centralized, making it impossible to meet these conditions. Only a weakly coupled, distributed architecture can work. A multi-level standard component system is possible. Inferentially, the ideal BMS resembles a distributed system, composed of different levels. A standard single-string module is essential, connected via a bus to a master controller. This forms a two-level distributed architecture. If the number of battery packs is large, a three-level system may be needed, dividing the system into multi-string modules. This architecture allows for local data storage and quick reassembly. However, it also requires functional support from each component. For example, the single-string module must support automatic reordering, passive equalization, and communication with the driver and controller. The bus must be simple, reliable, and support both communication and energy transfer. The driver must be a standard part, capable of managing different battery groups and knowing its position in the overall system. Active equalization adds complexity, requiring precise algorithms and energy transfer through the bus. The controller handles measurements, calculations, and communication. If this architecture is implemented, it could enable standardized battery module applications, supporting cross-enterprise power exchange and transforming the business model. It would resemble a software platform, with standardized underlying components and diverse upper-layer applications. However, all of this remains theoretical, with many challenges yet to be addressed. Achieving full lifecycle management of power batteries is a long and complex journey. I hope this discussion sparks further exploration and real-world progress.

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