Trust but Verify: Important Lessons from Evaluating Battery Cells

In recent years, because of ongoing challenges in the battery cell supply chain, it has become more important than ever for manufacturers of battery-powered products to verify the quality of the battery cells they source before they are incorporated into a product. Battery failures during product testing can happen for a variety of reasons and are a valuable source of information, but a preemptive analysis of cell quality and continuous reviews of new batches of cells can eliminate many common sources of failure, ensure consistency, and save time and money later in testing.

Cell Manufacturing & Supply Chain Challenges

In general, as demand for batteries has increased, electronics manufacturers have found that high-quality cells are much more difficult to source. Many established cell manufacturers are narrowing their focus, producing only the most lucrative products like EV cells, which makes other kinds of cell harder for electronics manufacturers to source. Cell prices, in general, are increasing, minimum orders are increasing, and lead times are much longer, but the quality of cells is staying the same or, in some cases, declining.

Because of these challenges, battery product manufacturers sometimes turn to unfamiliar suppliers for battery cells, especially when they first begin prototyping a new product and need a small quantity. The easiest way to get a small quantity of cells is to order them online, but as we have learned firsthand in the lab, the internet is rife with low-quality and counterfeit battery cells.

Identifying Low-Quality Cells

Manufacturers purchasing cells generally know to look for IEC, UL, and UN certifications. These are important safeguards against gross defects, but they do not necessarily catch latent defects, and they have no bearing on inaccurate claims that sellers may make. A cell may be authentically IEC, UN, and UL certified, but the seller may claim in the product listing that it is made by a specific manufacturer or has a certain capacity when it does not. This may be deliberately deceptive on the part of the seller, or it may be the result of an unclear or unstable supply chain that leads to cells that are meant to be identical having significantly different quality.

As an experiment, the team at the Element Gainesville lab ordered a pack of batteries from an online supplier that were allegedly manufactured by Panasonic and compared them with one from another source that we knew was authentic. The batteries from the online supplier proved to be not only counterfeit and of lower quality overall, but different individual cells in the same package had discrepancies in design and construction, suggesting that they were made in different factories with different quality standards. This cross-section demonstrates just a few of the differences you can see at a glance.

There are several red flags that you can look for yourself to identify potentially subpar or counterfeit cells without expert help:

• Different fonts on the wrapping
• Inconsistent wrapping color
• Repetition of serial numbers
• Variation of insulation
• Different electrode measurements
• Jellyroll or stack sizing not matched to the can or pouch
• Circuit board components or layout is not consistent

Risks & Solutions

Buying batteries from a newer or smaller supplier is not inherently a problem, and in some applications, a battery with lower capacity or a shorter lifespan is appropriate for the product, but poorly made or inconsistent cells are one of the most common sources of failure for battery-powered products. Poor-quality cells affect not only product performance and longevity, but they can also be a serious safety risk. Thermal runaways that lead to fires and injury are fortunately rare, but they can do a great deal of harm, and they can cause a permanent break in public trust.

Even established suppliers occasionally change their manufacturing processes or the materials used in their batteries. Although the overall quality of these batteries may still be good, using a different type of cells in the same product can produce unexpected failures.

Because of these risks, more manufacturers are choosing to have a third-party battery testing expert assess the quality of each batch of battery cells before they are used in a product. In many cases, testing professionals can pinpoint what conditions will cause a cell to eventually fail based on flaws in its construction, or identify a specific step in the manufacturing process that is not up to par. This can help buyers find a more appropriate manufacturer or give them the information they need hold their manufacturer accountable for process improvements.

Although sourcing high-quality cells is harder than it used to be, these challenges are not insurmountable, as long as electronics manufacturers remain diligent and consistent about ensuring the quality of their cells. If you have questions about battery evaluation, contact our experts today.