Study Reveals 1 in 13 Low-Cost Lithium-Ion Battery Cells Could Have Dangerous Defect

Report on the most widely used lithium-ion batteries reveals hidden risks and underscores the importance of quality controls in the global supply chain to protect brands and consumers

CAMBRIDGE, Mass., Sept. 24, 2025 /PRNewswire/ -- Lumafield, a leader in industrial X-ray CT technology, today released the results of a study evaluating the safety and quality of lithium-ion batteries. The research evaluates more than one thousand 18650 lithium-ion battery cells from ten brands and reveals an enormous gap in quality between brand-name batteries and low-cost cells that are widely available through online marketplaces. The study found that nearly 8% of low-cost or counterfeit batteries could have a dangerous defect known as negative anode overhang. Furthermore, key indicators of quality in low-end batteries are seven times worse compared to those of name-brand manufacturers, introducing further risk.

Lithium-ion batteries have grown in popularity as they enable dense, portable, rechargeable power, and the 18650 form factor is ubiquitous, with these cells powering everything from vapes and electronic toothbrushes to medical devices and even some electric vehicles. However, the quality of these battery cells varies significantly between brand-name original equipment manufacturer (OEM) cells, re-wrap cells that have had their plastic wrapper removed and replaced (often with inflated specs) and low-cost or counterfeit cells that are increasingly flooding online marketplaces like Temu and Amazon.

Battery defects like negative anode overhang and alignment misregistration significantly increase the risk of failure, impeding performance of the devices they power or, in some cases, causing catastrophic fires. The risk is not theoretical. In 2024, the Consumer Product Safety Commission (CPSC) issued 26 recalls and 9 product safety warnings related to fire and burn hazards posed by battery overheating.

To study the quality of 18650 cells, Lumafield used Ultra-Fast CT scanning on a sample of more than 100 cells from each of ten different brands, ranging from high-quality OEMs to outright counterfeits. The results show clear, measurable indicators of risk in non-OEM 18650 cells. Key findings include:

• Of the 1,054 battery cells scanned, 33 had negative anode overhang, a manufacturing defect that accelerates aging and significantly increases the risk of internal short-circuiting and battery fires.
  
  
• All 33 of the defective cells came from low-cost or counterfeit brands, meaning one in 13 (nearly 8%) low-cost/counterfeit batteries could have this dangerous defect.
  
  
• One low-cost brand acquired through Temu had a 15% rate of negative anode overhang defects—a serious risk to consumers who may be tempted to acquire inexpensive batteries through the marketplace.
  
  
• On other measures of cell quality, low-cost/counterfeit batteries are seven times worse than their OEM counterparts.
  
  
• Low-cost/counterfeit 18650 cells had 50% worse edge alignment—referring to the winding of the internal layers of the cylindrical battery—compared to OEM cells. This represents yet another quality concern that can cause performance degradation and internal short circuits.
  
  
• None of the 300 brand-name OEM cells from Murata, Samsung and Panasonic suffered from negative anode overhang, suggesting that batteries from these high-quality manufacturers sourced through legitimate retail channels are the safest and most reliable cells.
  
  
• The risks in individual cells are compounded by the fact that many products include multiple 18650 cells—from 5 in a typical cordless drill to 39 in an e-bike battery pack that Lumafield CT scanned for the study.

"Non-OEM batteries are a minefield," said Eduardo Torrealba, Co-Founder and CEO of Lumafield. "We're seeing dangerous defects at a scale that should alarm every manufacturing leader. If you're not policing your supply chain, you're gambling with your brand and your customers' safety. With trade barriers shifting weekly, risk compounds. Rapid industrial CT isn't optional; it's the best way to enforce safety and stop bad parts before they reach people."

Industrial X-ray CT is a powerful technology for verifying product quality, but until recently it has been a slow and expensive tool accessible only to the largest manufacturers. Lumafield has made industrial X-ray CT accessible and fast, with automated solutions that can scan more than 12 parts per minute and instantly flag defects.

"Many of us have become desensitized to warnings about the dangers of lithium-ion batteries, but our research underscores why consumers must be vigilant," said Alex Hao, author of the Lumafield Battery Quality Report. "It can be inconvenient to properly use, store, and dispose of batteries, but there's no room for complacency. Furthermore, consumers should be mindful of where they buy their batteries. If a deal looks too good to be true, it probably is."

The Lumafield Battery Quality Report provides the study's complete findings and is available as a free download.

Research Methodology

To develop this study, Lumafield used Ultra-Fast CT technology to scan more than 1,000 batteries, sampling at least 100 cells from 10 different brands that ranged from high-quality OEM to low-cost counterfeit. After scanning, Lumafield used its Battery Analysis Module to automatically capture quality metrics for each battery. The evaluation focused on the two main indicators of cell safety and quality—anode overhang and edge alignment—evaluating these metrics within and across each of the brands.

The full report is available at https://www.lumafield.com/battery-report.

About Lumafield

Lumafield gives engineers the power to see inside their work in unprecedented detail, at every stage of the product development process. Lumafield's industrial X-ray CT scanners are ideal for both lab-scale and in-line inspection, and its cloud-based analysis software delivers actionable insights immediately. Lumafield's technology has transformed both product development and high-volume manufacturing in industries as diverse as medical devices, athletic equipment, electronics, and consumer packaging.

Founded in 2019 and headquartered in Cambridge, Mass., with additional offices in San Francisco and Los Angeles, Lumafield has received funding from investors including IVP, Spark Capital, DCVC, Kleiner Perkins, Lux Capital, Tony Fadell's Build Collective, and Figma founder Dylan Field.

Learn more at Lumafield.com.

Media Contact

Email press@lumafield.com for interviews or additional assets.

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SOURCE Lumafield