Why introduce SWIR sensors into Electric Vehicle Battery Production Monitoring and Quality Control Testing?

As electric vehicles become more popular, battery quality control testing is critical to ensure that batteries meet stringent safety and performance requirements. Unfortunately, leak detection techniques are slow and inaccurate. Even tiny leaks could reduce the battery’s lifespan, decrease performance, or increase warranty costs. Even worse, leaking can shortcircuit electrical systems, set fires, or cause damage to battery components.

Non-destructive testing of batteries can identify any defects before they leave the production facility. Automated radiographic inspection (X-ray inspection) can be used to examine hidden inner structures and identify defects before the cells leave the factory. This prevents defective cells from being built into battery modules. The cell structure can also impact quality control methods. Rolled cells are easy to inspect in 2D. But stacked cells require 3D computer imaging. This makes it difficult to interpret a transmissive-X-ray image.

During manufacturing, engineers evaluate a battery’s state of health by measuring its state of charge and discharge. They also evaluate the condition of the battery’s busbar, which is a long conductor isolated from ground and is responsible for distributing current throughout the battery pack. Testing the busbar is an important part of the process because the weld impedance of batteries is an important metric. A weld with a low resistance can result in excessive heat and early failures. Engineers can determine the resistance of a battery before it is fully operational to remove defective modules as quickly as possible.

The SoC information, in addition to performing testing, is essential to estimate a battery’s usable lifetime. The usable life of a battery pack may be drastically reduced by overcharging it or undercharging it. The battery management software (BMS) also uses this information to ensure that the cells operate within safe limits. BMS must also include a precise charge estimator to calculate SoC.

SoC can’t be measured directly, unlike voltage and temperature. It must therefore be calculated using proprietary parameters.

SWIR can be used to adapt the Lithium-Ion Battery Testing Process

In terms of testing equipment suitable for adaptation to existing production systems, high resolution, wide field-of-view, and extended SWIR cameras can be utilized to overcome important lithium-ion battery inspection challenges, therefore enabling lithium and lithium-ion battery producers to meet increasingly demanding performance and quality specifications.

SWIR Vision’s Acuros SWIR cameras, for example, can provide imaging through the Li:Ion separator using SWIR wavelengths. These cameras – or sensors – provide the necessary alignment accuracy of inter-layer electrodes leading directly to more available energy storage capacity and longer battery lifetimes.

Because of the ability to see through objects and feed back high-resolution imaging at a rapid-fire rate, these sensors can be adapted as a quality control feature throughout the production process. We expect rapid adoption of SWIR cameras for battery testing.