CALB Technology Overhaul Focuses on Battery Quality and Safety After Aion Cell Swelling Incident

CALB has launched a comprehensive internal technology overhaul focused on improving battery quality and safety after battery cells installed in GAC Aion vehicles experienced widespread swelling. The initiative includes major upgrades to manufacturing controls, quality validation, product traceability, organizational management and customer response systems. The company is implementing stricter production requirements while reinforcing oversight across its battery development and manufacturing processes to reduce quality risks and improve long-term product reliability.

CALB Tightens Manufacturing Standards Following Battery Investigation

CALB has significantly strengthened its manufacturing processes by introducing tighter tolerance requirements. Electrode coating thickness measurement and areal-density controls are now being aligned with specifications used by CATL. Previously, lithium iron phosphate (LFP) cathode areal-density deviations ranged between 2.3 and 2.5 g/cm³, which matched common industry standards. Following the overhaul, allowable deviation has been reduced to within ±1.5%, reflecting a more stringent quality control approach.

Key Manufacturing and Quality Improvements Introduced by CALB

• Stricter electrode coating tolerance standards.
• Enhanced online monitoring of dew points and moisture during electrolyte filling.
• Traceability improved from daily retained samples to individual production rolls.
• Retrospective audits covering production materials used during 2022 and 2023.
• Discontinuation of additive formulations with lower safety margins.
• Updated design standards for cell casings, explosion-proof valves and terminal welding.

Major Process Changes Implemented Across Battery Production

Quality Department Receives Greater Production Authority

CALB has also strengthened its internal governance by establishing a rapid-response customer quality team under its passenger vehicle division. The company is jointly monitoring battery management system (BMS) data with major customers to identify potential issues more quickly. Most notably, the quality department has been granted full authority to block batch releases that fail review standards, eliminating previous practices where production approvals could be accelerated to satisfy urgent automaker demand.

A person familiar with the matter stated that any production batch failing quality review standards cannot be released, even if research and development teams are working under tight project deadlines. This change is intended to reinforce independent quality oversight throughout the manufacturing process.

Battery Swelling Incident Prompted Technology Overhaul

The overhaul follows the battery swelling controversy involving GAC Aion Aion S vehicles equipped with CALB's 177-Ah LFP battery cells. After accumulating between 150,000 and 300,000 kilometers, numerous vehicles reportedly experienced battery cell swelling, electrolyte leakage and sudden power loss while driving. The issue became widely known as the "banana battery" controversy because affected battery cells bent into a banana-like shape.

The affected vehicle models recorded sales of approximately 220,900 units during 2023, with around 72% entering ride-hailing and taxi fleets. On July 18, GAC Aion announced an extended battery warranty of eight years or 300,000 kilometers for affected models while offering free battery inspections and replacements. CALB simultaneously established a direct maintenance channel and committed to taking ultimate responsibility for battery cell quality.

Financial Impact and Market Position

Although the company expects higher costs from customer compensation, upgraded production standards and manufacturing restructuring, CALB continues to expand its business. First-quarter revenue increased 71.2% year over year to 11.8 billion yuan, while domestic battery installations reached 7.31 GWh, representing a 5.86% market share. In June, CALB installed 5.2 GWh of batteries in China, achieving a 6.82% market share and ranking behind only CATL and BYD.

China's Top EV Battery Makers by Market Share (June 2026)

Frequently Asked Questions

Why is CALB carrying out a technology overhaul?
CALB launched the technology overhaul after battery cells installed in certain GAC Aion vehicles experienced swelling, electrolyte leakage and power loss following high-mileage operation. The company is strengthening manufacturing standards, product traceability, quality validation systems and customer response mechanisms while giving its quality department greater authority over production approvals. These measures are intended to improve battery safety, enhance durability and reduce the likelihood of similar issues occurring in future battery production.

What manufacturing improvements has CALB introduced?
CALB has tightened electrode coating tolerance standards, enhanced moisture monitoring during electrolyte filling, improved production traceability to individual rolls and audited historical production materials used in 2022 and 2023. It has also updated battery design standards covering cell casings, explosion-proof valves and welding margins while discontinuing certain additive formulations with lower safety margins. These initiatives collectively strengthen manufacturing quality, process control and overall battery reliability.