Majority of BESS defects at system level, according to CEA factory audits

Clean Energy Associates (CEA) conducted quality audits at 70+ battery energy storage factories worldwide and reported its findings in a new Battery Energy Storage System (BESS) Quality Risks report.

The majority (72%) of discovered defects were at the system level, rather than the cells or modules, indicating that these problems generally arose during the systems integration process. That number is up from 48% last year, according to the CEA report.

Importantly, no audited systems were shipped or installed with unresolved safety-critical issues.

Common BESS defects at the factory

CEA identified these as the the most common defects found during 2024 factory audits:

• 28% of systems had fire detection & suppression defects — critical for preventing runaway fires
• 19% had faulty auxiliary circuit panels — risking control system failure
• 15% had thermal management defects — increasing the risk of overheating
• 6% failed capacity tests — meaning they couldn’t deliver the energy they were designed for

These findings underscore the importance of proactive detection and timely resolution to maintain safety and reliability.

CEA Battery Cell Findings

Here is an excerpt from the report regarding the battery cell defects found (15 percent of total risks found)

Although battery cell factories have the highest level of automation, they make up a larger number of findings (compared to battery modules) due to their lengthy production processes and higher precision requirements, leading to more room for error.

Audit findings on cells typically have a higher severity rating as cells are the building blocks of the energy storage system, and defects can be detrimental to system performance and safety.

Slitting carries a high risk of burrs on electrodes, which can pierce the separator and trigger thermal runaway. Even minor deviations from SOPs or limitations in detection equipment are recorded as findings, contributing to the high frequency.

You can access the full report here.