Quality Risks In Energy Storage Manufacturing

Key takeaways:

• Intertek CEA’s energy storage manufacturing quality report identified system-level integration as the largest source of manufacturing findings

• Battery and thermal management systems, fire suppression, and water ingress were among the most safety-critical issues observed

• Cell manufacturing defects during electrode slitting can create burrs that increase the risk of thermal runaway

Quality assurance is equally important in energy storage manufacturing as it is in solar manufacturing, especially when GW-scale energy storage systems (ESS) projects are deployed. Large-scale deployments are expected to increase over time, alongside other standalone and small-scale applications.

Intertek CEA recently released a quality report on energy storage manufacturing for 2025. The company conducted QA audits on a total of 70 GWh of lithium-ion ESS projects since 2018, including over 880 inspections. It identified a total of 3,370 issues during these quality audits.

An issue or finding during an inspection is categorized as minor, major, or critical based on the severity of the risk or damage it can cause. A minor finding does not pose a high risk and falls outside quality requirements. A major finding can impact safety in the short or long term and may reduce the battery’s functionality. A critical issue would be one that violates mandatory regulations, resulting in severe safety risks and hazardous conditions. Quality assurance companies, in general, flag risks and provide corrective actions, ensuring that a product with a risk of failure is not delivered or installed.

Intertek CEA’s energy storage manufacturing audits covered cell-, module-, and system-level inspections. About 75% of the total findings in 2025 were attributed to system-level issues, which occur mainly for 3 reasons. First, rapid product iteration, which focuses on reducing product development time through continuous, smaller updates, and preventing process maturity. Second, ESS integration involves labor-intensive manual processes that often have weak quality control systems to ensure long-term performance. Finally, these complex systems are vulnerable to problems that originate in upstream processes or components that may have passed those inspections.

In 2025, system-level inspections resulted in 47% of findings related to the balance of system (BoS), 42% related to the enclosure, and 11% related to performance testing. Common examples in BoS include malfunctions of temperature, gas, and smoke sensors due to miswiring, battery management system (BMS) failures under certain conditions, and liquid coolant leakages. Enclosure-related issues include poor strength and deformation of the door or rain shield, wiring and cable arrangement, failure of the grounding insulation test, water ingress, and other appearance defects. Control defects such as charging/discharging failures, cell overheating, PCS power control malfunctions, and underachieving round-trip efficiency account for performance issues. Of all these issues, most were safety-related and occurred in battery and thermal management systems, fire suppression systems, and water ingress, with each of these accounting for over 4% of total findings at the system level.

Cell-level findings accounted for 15% and module-level findings accounted for 10% of the total findings in 2025. Battery cell manufacturing, however, despite high automation, requires greater precision and involves longer processes compared to battery assembly. Therefore, there are more findings at this level. The highest and riskiest defects at the cell level occurred during slitting, in which electrode cutting was inconsistent with the required specifications. This results in a risk of burrs on electrodes, which can pierce the separator and trigger thermal runaway.

At the module level, the highest number of issues was found at the cell sorting and installation step, which relies heavily on manual inspection and handling, including checks of appearance, cleanliness, gluing, fixture, and electrical parameters.

The complete report, titled Global Energy Storage Manufacturing Quality Report 2026, is available for free download here.