In the first eight months of 2025, 13.82 million new energy vehicles were sold globally, with the Chinese market contributing approximately 9.35 million, accounting for 67.6%, and a penetration rate climbing to 48.2%. In other words, nearly 5 out of every 10 new cars are electric vehicles.
In this energy revolution, the power battery is both the engine and the sword of Damocles hanging over our heads.
As a crucial link in quality infrastructure, metrology technology is playing the role of the “golden yardstick of industrial precision,” building a technological defense line for the entire life cycle of new energy batteries.
01 Battery Quality Control: A Core Challenge for Industry Development
1. Quality Control Considerations Behind Recalls
On October 23, 2025, a Li Auto MEGA vehicle experienced a sudden fire. Eight days later, Li Auto voluntarily recalled 11,411 vehicles from the same batch.
The recall is attributed to insufficient anti-corrosion performance of the coolant, which may lead to corrosion and leakage of the cooling aluminum plates of the power battery and front motor controller. This can cause the vehicle’s malfunction indicator lamp to illuminate, power to be limited, and the vehicle to fail to power on. In extreme cases, it may even trigger thermal runaway of the power battery.
An even more noteworthy detail is that the Li Auto cloud system issued a warning more than four hours before the vehicle caught fire.
Behind this detail lies the role of precise measurement and real-time monitoring technology—but even though the sensors captured abnormal data and the system issued timely alarms, why did the accident still occur?
The answer to this question precisely points to a key aspect of quality control in the manufacturing process of new energy vehicles. For batteries, end-point data monitoring alone is insufficient; a comprehensive manufacturing quality assurance system must be established at the source.
Battery quality control is a battle across the entire chain, from design and production to use and recycling.
2. The Precision Pressure Brought by Complex Systems
Many people are unaware that a power battery accounts for 30% to 50% of the total cost of a vehicle. It is not only expensive but also technologically intensive and structurally complex. Its performance and reliability directly determine the electric vehicle’s range, lifespan, and safety level.
However, battery quality is never determined by a single factor.
From the accuracy of sensor readings to geometric tolerances during assembly; from the selection of coolant materials to the control of welding precision; from the uniformity of the coating inside the cell to the fit clearance between modules… any small deviation could become a ticking time bomb after thousands of charges and tens of thousands of kilometers of driving.
The quality pressure brought about by this complexity is constantly increasing. China will implement stricter battery safety regulations in July 2026, adding extreme tests such as collision and fast-charging durability, requiring batteries not to spontaneously combust or explode under conditions such as thermal runaway. The new regulations set higher standards for the accuracy and traceability of measurement data.
However, the industry still faces the challenges of “inability to measure, incomplete measurement, and inaccurate measurement,” problems that permeate almost every stage from R&D to recycling.
To break through the measurement impasse, metrology technology must be truly utilized.
02 Metrology Permeates the Entire Battery Life Cycle
From production to disposal, every stage of a power battery requires the precise intervention of metrology technology. This is not a simple measurement act, but rather the construction of a complete quality assurance system with traceable data and predictable status.
1. R&D and Production: A Precision Game in Millimeters
The production process demands extensive metrological capabilities. From electrode manufacturing to cell molding and module assembly, every step requires precision metrology equipment.
For example, to control the geometric tolerances of cells and modules, manufacturers use high-precision coordinate measuring machines (CMMs) combined with non-contact optical scanning to measure parameters such as shell flatness, end-face parallelism, outer diameter runout, and terminal position.
For hidden defects caused by internal structures or electrolyte injection, high-resolution X-rays, CT scans, or optical imaging combined with AI interpretation are used for non-destructive testing, providing traceable data for assembly fit and welding quality.
Even more refined control is evident in the welding process.
A battery module contains hundreds or even thousands of weld points. Each weld point directly affects conductivity and safety.
Laser welding, with its high energy density and controllability, has become the mainstream method for connecting power batteries, but it requires extremely high precision in detecting weld morphology, roughness, and internal defects.
In practical applications, Mahr surface roughness meters are often used to quantitatively evaluate the surface morphology and roughness of laser welds, verifying the stability and consistency of welding parameters. Studies show that weld surface roughness is closely related to the formation of internal porosity and cracks; controlling the Ra value can effectively improve the mechanical strength and electrical conductivity of the weld joint.
Simultaneously, combined with Zeiss X-ray or industrial CT non-destructive testing, it is possible to accurately identify micro-porosity and fusion defects within the weld.
Defect identification and detection in finished battery cell production using Zeiss industrial CT technology.
This “surface + internal” dual metrology system has been adopted by leading companies such as BYD and CATL on their production lines.
2. Use and Recycling: Dynamic Monitoring Protects Battery Value. During vehicle operation, voltage, temperature, and current data are the “vital signs” of battery health.
Dynamic monitoring during battery use allows for the construction of an early risk warning system through real-time data streams. During the charging and discharging process, real-time status monitoring ensures the battery is always in optimal working condition, extending its lifespan and optimizing range.
Next comes the recycling stage. Where do batteries go after they’re retired?
Many people assume they’re recycled and dismantled to extract raw materials. That’s only part of it. Another part is “secondary use”—giving batteries a second life.
What does this mean?
A battery used in a car for several years may have its capacity decayed to below 80%, making it unsuitable for continued use.
However, when its capacity is between 50% and 80%, it’s more than sufficient for an energy storage system. Therefore, retired batteries can be “downgraded” and continue to function.
This sounds appealing, but in practice, it faces a challenge: how to determine which batteries are still usable?
At this point, the focus of measurement shifts to residual value assessment and the feasibility of secondary use. Capacity, internal resistance, voltage, and current—every parameter must be precisely measured to determine the remaining value of the battery.
Researchers at Xi’an City Investment Group pointed out: “We reintegrate ‘retired’ power batteries, conduct full-performance measurement and testing on the cells, and through measurement data analysis, accurately select high-performance cell units for use in energy storage systems.”
What does this mean? A battery’s second life can be as valuable as its first. Advances in new technologies, including metering, enable battery recycling to create even higher value and generate substantial economic benefits.
Zhou Xiaohang, Senior Director of the Clean Power Project at the Natural Resources Defense Council, explained that the amount of retired power batteries in China is expected to reach 6 million tons by 2030. Based on an energy density of 100Wh/kg, this could support the construction of at least 10,000 medium-sized energy storage power stations through tiered utilization.
This is no small number.
However, all of this hinges on accurate measurement. Inaccurate measurement leads to the disposal of good batteries and the entry of defective batteries into energy storage systems, resulting in resource waste and safety hazards.
Therefore, accuracy determines value.
03 Building a New Digital Metering Ecosystem
1. Data-Driven Predictive Metering
Future battery quality management will rely more heavily on predictive analysis of full lifecycle data. Each battery should have a unique “digital ID card,” recording the complete metering data chain from production to disposal.
NIO’s BaaS (Battery as a Service) battery rental model provides a model.
You buy a car, you can rent the battery. In this way, the battery doesn’t belong to you, it belongs to NIO. NIO is responsible for these batteries. Therefore, they’ve equipped them with a “digital steward.”
Key parameters such as temperature, voltage, and current during battery operation are collected in real time by the battery management system. This data is transmitted to the cloud, where AI analyzes battery performance and health. The system can predict potential risks and issue early warnings.
This is a shift from “firefighting” to “fire prevention.”
Even more impressively, NIO uses digital twin technology. This creates a “digital clone” of the battery; while the physical battery runs in the car, the digital battery can be simulated in the cloud. Through real-world testing and simulation data, the system can predict the battery’s future degradation curve, potential failure points, and remaining lifespan.
Shu Dailong, head of battery asset management at NIO, said that this system significantly improves battery safety and reliability, reducing accidents caused by malfunctions.
Because you know when and what problems the battery will encounter, you can replace it in advance.
NIO’s practice embodies a shift from “passive detection” to “proactive prediction,” demonstrating the core value of the integration of metrology technology and digitalization in battery safety management.
2. Metrological Support for Traceability Systems
The EU’s new Battery Law requires all electric vehicle batteries sold in Europe to have a “battery passport” recording their carbon footprint, raw material origin, performance parameters, and other information.
This is essentially a mandatory requirement for metrological data throughout the battery’s entire lifecycle. Achieving this goal requires establishing a cross-border, cross-enterprise metrological data sharing platform and ensuring the data’s authenticity and immutability.
Blockchain technology combined with a metrological system offers a feasible solution.
Guoxuan High-Tech has proposed a blockchain-based information management system for the entire lifecycle of power lithium batteries, aiming to put measurement and verification data such as cell capacity, module assembly data, and post-retirement recycling status on the blockchain to build a “real, transparent, and comprehensive” traceability system.
Beyond Guoxuan High-Tech and the aforementioned companies, automotive giants including BMW, Porsche, Mercedes-Benz, Volvo, Volkswagen, and Hyundai have already ventured into blockchain.
It is foreseeable that with the advancement of global automotive electrification strategies and the intensification of competition in the power battery market, more and more OEMs, battery manufacturers, and material suppliers will join blockchain supply chain initiatives.
This not only improves battery safety and quality traceability but also provides a solution for overcoming technical barriers in cross-border trade.
04 Entrusting “Quality” to Metrology, Making “Trust” Evidence-Based
Returning to the initial question: How should metrology support battery quality management?
The answer is clear—metrology is not an isolated technology, but an infrastructure that runs through the entire battery lifecycle; it’s not simply numerical measurement, but a data link connecting design, manufacturing, use, and recycling.
With the iterative upgrades of charging and battery technologies, supercharging is gradually becoming the main driver, and the trillion-dollar charging infrastructure industry is ushering in a golden age of development.
And the foundation of all this is precision.
When we sit in an electric vehicle and press the accelerator, countless precise measurement data are safeguarding safety.
Only when every participant in the industry recognizes that accurate metrology is the first line of defense for battery safety can we truly usher in a safe, reliable, and sustainable era of new energy vehicles!
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