A recent teardown of the Xiaomi SU7 Standard Edition’s battery has provided a detailed look at the differences between CATL and BYD FinDreams cells. Conducted by independent technician Aichi New Energy, the analysis highlights variations in energy density, construction, and abuse test outcomes between the two leading battery suppliers.
Inside the Teardown: CATL vs BYD FinDreams Cells
The teardown, published on Bilibili on August 7, 2026, examined a 186.7 Ah CATL Shenxing LFP cell from the Xiaomi SU7 Standard Edition and compared it to a same-capacity FinDreams cell from BYD. Both cells share the same rated capacity, but their physical characteristics and internal designs differ significantly.
The CATL cell measures 213 mm (~8.39 inches) long, 80 mm (~3.15 inches) wide, and 95 mm (~3.74 inches) high, with a mass of 3.4 kg (~7.5 lbs). In contrast, the BYD FinDreams cell is 620 mm (~24.4 inches) long, 24 mm (~0.94 inches) wide, and 103 mm (~4.06 inches) high, weighing 3.2 kg (~7.1 lbs).
Energy Density and Internal Construction
The CATL cell’s gravimetric energy density was calculated at 175.7 Wh/kg, while the BYD FinDreams cell achieved 186.7 Wh/kg—a 6.3% advantage for BYD. Volumetric energy density also favored BYD, with 389.8 Wh/L compared to CATL’s 369.0 Wh/L.
Internally, the CATL cell uses four winding cores (jelly rolls) inside a hard aluminium casing, with thicker-than-20-micrometre aluminium foil for the positive current collector and an 11-micrometre copper foil for the negative. The separator is about 12 micrometres thick, featuring a double-sided ceramic/polymer composite coating. The BYD cell, by contrast, employs a laminated stacking process, resulting in a long, blade-shaped form factor.
Abuse Testing and Observations
During abuse testing, more than 20 steel nails were driven into the fully charged CATL cell, which recorded a voltage of 3.392 V. The cell discharged and produced smoke, but no open flame or explosion was observed. However, when the internal winding layers were forcibly separated after removing the casing, the exposed material ignited.
These tests were conducted in a workshop setting and do not meet certified laboratory standards such as GB 38031-2025. As such, the results cannot be used to determine pack-level safety or regulatory compliance.
Competitor Comparison
CATL and BYD are two of the most prominent battery suppliers in the global EV market. CATL, founded in 2011, held a 39.2% global battery market share in 2025 and has a production capacity of 772 GWh. The Xiaomi SU7’s use of both CATL and BYD cells highlights the competitive landscape, with each supplier offering distinct technical approaches to cell design and energy density.
Historical Context
The global battery market has seen a 17% year-on-year increase, reflecting the rapid growth in EV adoption. CATL remains the world’s largest lithium-ion battery supplier, while BYD continues to innovate with its blade cell architecture. These developments are shaping the performance and safety standards of next-generation electric vehicles.
Why this matters
The teardown provides rare insight into the construction and performance differences between two leading battery technologies. As automakers like Xiaomi source cells from both CATL and BYD, understanding these differences is crucial for evaluating vehicle range, safety, and overall battery performance.
With battery safety and energy density under increasing scrutiny, especially in China’s rapidly evolving EV market, such independent analyses help inform both industry stakeholders and consumers.
What this means for buyers
For prospective EV buyers, the choice of battery supplier can impact real-world range, safety, and long-term reliability. While both CATL and BYD cells meet the rated capacity, their differences in energy density and internal design may influence vehicle performance. Buyers should consider these factors, along with regional availability and after-sales support, when evaluating new EV models like the Xiaomi SU7.
Key Specs
- CATL Cell Rated Capacity: 186.7 Ah
- BYD FinDreams Cell Rated Capacity: 186.7 Ah
- CATL Cell Dimensions: 213 mm (~8.39 inches) x 80 mm (~3.15 inches) x 95 mm (~3.74 inches)
- BYD FinDreams Cell Dimensions: 620 mm (~24.4 inches) x 24 mm (~0.94 inches) x 103 mm (~4.06 inches)
- CATL Cell Mass: 3.4 kg (~7.5 lbs)
- BYD FinDreams Cell Mass: 3.2 kg (~7.1 lbs)
- CATL Gravimetric Energy Density: 175.7 Wh/kg
- BYD Gravimetric Energy Density: 186.7 Wh/kg
Source
Images sourced from: arenaev.com, captainelectro.com, supercarblondie.com
