A counterfeit battery is unlikely to have undergone the same standardized testing as original equipment manufacturer (OEM) batteries, meaning standard safety measures may not be present. In the case of lithium-ion batteries, thermal runaway can result in uncontrolled heating up to extreme temperatures, causing electrolyte leakage, smoke, fire, and potentially damaging the device and igniting larger fires that may injure people too. Most properly tested batteries from the best brands have controls that prevent the battery’s internal temperature from breaching this threshold and leading to thermal runaway, but counterfeiters aren’t deeply concerned about doing that much work before producing them.
So, what do you look out for? As the FBI notes, it’s best to avoid third-party purchases of batteries and get them from authorized dealers or distributors that test with nationally recognized testing laboratories. Many manufacturers sell directly and/or will provide a list of trusted vendors. Any battery that seems too cheap, ships too fast, or makes out-of-the-ordinary endurance promises is probably not the upstanding battery it claims to be. If the batteries are already in your hands, you’ll want to look out for poor packaging, misprinted or misspelled labels, and make sure the batteries have a “UL” in a circle symbol to comply with certification requirements, not that these symbols can’t be faked. A few of the above precautions can help ensure that when your battery dies, your device isn’t taken with it.