As an auditor of battery manufacturers around the world, University of Maryland mechanical engineer Michael Pecht frequently finds himself touring spotless production floors. They’re akin to “the cleanest hospital that you could imagine–it’s semiconductor-type cleanliness,” he says. But he’s also seen the opposite, and plenty of it. Pecht estimates he’s audited dozens of battery factories where he found employees watering plants next to a production line or smoking cigarettes where particulates and contaminants can get into battery components and compromise their performance and safety.

Unfortunately, those kinds of scenes are just the tip of the iceberg. Pecht says he’s seen poorly assembled lithium-ion cells with little or no safety features and, worse, outright counterfeits. These phonies may be home-built or factory-built and masquerade as those from well-known global brands. They’ve been found in scooters, vape pens, e-bikes, and other devices, and have caused fires and explosions with lethal consequences.

The prevalence of fakes is on the rise, causing growing concern in the global battery market. In fact, after a rash of fires in New York City over the past few years caused by faulty batteries, including many powering e-bikes used by the city’s delivery cyclists, New York banned the sale of uncertified batteries. The city is currently setting up what will be its first e-bike battery-swapping stations as an alternative to home charging, in an effort to coax delivery riders to swap their depleted batteries for a fresh one rather than charging at home, where a bad battery could be a fire hazard.

Compared with certified batteries, whose public safety risks may be overblown, the dangers of counterfeit batteries may be underrated. “It is probably an order of magnitude worse with these counterfeits,” Pecht says.

There are a few ways to build a counterfeit battery. Scammers often relabel old or scrap batteries built by legitimate manufacturers like LG, Panasonic, or Samsung and sell them as new. “It’s so simple to make a new label and put it on,” Pecht says. To fetch a higher price, they sometimes rebadge real batteries with labels that claim more capability than the cells actually have.

But the most prevalent fake batteries, Pecht says, are homemade creations. Counterfeiters can do this in make-shift environments because building a lithium-ion cell is fairly straightforward. With an anode, cathode, separator, electrolyte, and other electrical elements, even fly-by-night battery makers can get the cells to work.

What they don’t do is make them as safe and reliable as tested, certified batteries. Counterfeiters skimp on safety mechanisms that prevent issues that lead to fire. For example, certified batteries are built to stop thermal runaway, the chain reaction that can start because of an electrical short or mechanical damage to the battery and lead to the temperature increasing out of control.

Judy Jeevarajan, the vice president and executive director of Houston-based Electrochemical Safety Research Institute, which is part of Underwriters Laboratories (UL) Research Institutes, led a study of fake batteries in 2023. In the study, Jeevarajan and her colleagues gathered both real and fake lithium batteries from three manufacturers (whose names were withheld), and pushed them to their limits to demonstrate the differences.

One test, called a destructive physical analysis, involved dismantling small cylindrical batteries. This immediately revealed differences in quality. The legitimate, higher quality examples contained thick plastic insulators at the top and bottom of the cylinders, as well as axially and radially placed tape to hold the “jelly roll” core of the battery. But illegitimate examples had thinner insulators or none at all, and little or no safety tape.

“This is a major concern from a safety perspective as the original products are made with certain features to reduce the risk associated with the high energy density that li-ion cells offer,” Jeevarajan says.

Jeevarajan’s team also subjected batteries to overcharging and to electrical shorts. A legitimately tested and certified battery, like the iconic 18650 lithium-ion cylinder, counters these threats with internal safety features such as positive temperature coefficient, where a material gains electrical resistance as it gets hotter, and a current interrupt device (CID), which automatically disconnects the battery’s electrical circuit if the internal pressure rises too high. The legit lithium battery in Jeevarajan’s test had the best insulators and internal construction. It also had a high-quality CID that prevented overcharging, reducing risk a fire. Neither of the other cells had one.

Despite the gross lack of safety parts in the batteries, great care had clearly gone into making sure the counterfeit labels had the exact same shade and markings as the original manufacturer’s, Jeevarajan says.

How to Spot a Counterfeit Battery

Because counterfeiters are so skilled at duplicating manufacturers’ labels, it can be hard to know for sure whether the lithium batteries that come with a consumer electronics device, or the replacements that can be purchased on sites like eBay or Amazon, are in fact the genuine article. It’s not just individual consumers who struggle with this. Pecht says he knows of instances where device makers have bought what they thought were LG or Samsung batteries for their machines but failed to verify that the batteries were the real thing.

“One cannot tell from visually inspecting it,” Jeevarajan says. But companies don’t have to dismantle the cells to do their due diligence. “The lack of safety devices internal to the cell can be determined by carrying out tests that verify their presence,” she says. A simple way, Pecht says, is to have a comparison standard on hand – a known, legitimate battery whose labeling, performance, or other characteristics can be compared to a questionable cell. His team will even go as far as doing a CT scan to see inside a battery and find out whether it is built correctly.

Of course, most consumers don’t have the equipment on hand to test the veracity of all the rechargeable batteries in their homes. To shop smart, then, Pecht advises people to think about what kind of batteries and devices they’re using. The units in our smartphones and the large, high-capacity batteries found in electric vehicles aren’t the problem; they are subject to strict quality control and very unlikely to be fake. By far, he says, the more likely places to find counterfeits are the cylindrical batteries found in small, inexpensive devices.

“They are mostly found as energy and power sources for portable applications that can vary from your cameras, camcorders, cell phones, power banks, power tools, e-bikes and e-scooters,” adds Jeevarajan. “For most of these products, they are sold with part numbers that show an equivalency to a manufacturer’s part number. Electric vehicles are a very high-tech market and they would not accept low-quality or cells and batteries of questionable origin.”

The trouble with battling the counterfeit battery scourge, Pecht says, is that new rules tend to focus on consumer behavior, such as trying to prevent people from improperly storing or charging e-bike batteries in their apartments. Safe handling and charging are indeed crucial, but what’s even more important is trying to keep counterfeits out of the supply chain. “They want to blame the user, like you overcharged it or you did this wrong,” he says. “But in my view, it’s the cells themselves” that are the problem.