Lithium Battery Safety: Warning Signs, Risks and Prevention Tips

Most lithium batteries are safe. The failures are hard to ignore.

Lithium batteries power phones, power banks, e-bikes, vacuums, drills and plenty of other devices we charge at home. Fires are serious and increasingly reported: more than 1,500 lithium battery fires occurred in communities across Canada last year, according to a CBC report on lithium battery fires. That number deserves attention, but it doesn’t mean every battery is a hazard. The scale helps put the risk in perspective. Vinny Gupta, an assistant professor of fire safety engineering at the University of Waterloo, says manufacturers now produce more than 10 billion battery cells each year, while safety problems involve only a small share. The trouble is that when a battery does fail, the fire can be dramatic. Gupta studies those failures by deliberately triggering them. Consumer batteries typically include safeguards such as temperature sensors, pressure relief valves that vent potentially flammable gases, and systems to prevent overcharging. Batteries are designed to stop charging automatically, but that protection doesn’t make them immune to damage or wear. Here’s the thing: a battery that has worked safely for years can still become risky.

Damage can be hidden

A manufacturing defect can create a problem, as can an accident. David Giles, CEO of Halifax-based battery monitoring company TempAlert, says a collision involving an e-bike or e-scooter can damage a battery. Even dropping a phone may cause internal damage that isn’t visible: a cracked screen is obvious; a compromised battery may not be.

Heat can contribute to damage, including from charging a battery in the sun. Overcharging is another common route to failure. Batteries are generally designed to guard against it, but design quality varies, and tampering or using the wrong charger can raise the risk. The fit of a connector doesn’t guarantee a charger is right for a device. Giles warns that chargers may supply different voltages: one could send 80 or 90 volts into a battery designed for 40. Repeated charge and discharge cycles also wear batteries down over time.

Watch for heat, but don’t expect a precise countdown

A failing battery usually doesn’t burst into flames without warning. It can begin to heat up during charging, then cool after it’s unplugged. Gupta calls unusual warmth the earliest indication of a problem. Giles says the pattern may recur before the battery stays hot even when disconnected. How long that progression takes is unclear. Gupta says it depends on what’s happening inside the battery, and that self-heating can accelerate exponentially once it begins. Giles says the window could stretch across days or weeks of charging and use—or shrink to 20 minutes. That uncertainty makes warning signs useful, but they can’t tell you exactly how much time remains.

Battery chemistry doesn’t offer a simple safety ranking

The two most common lithium battery chemistries are NMC, or nickel manganese cobalt, and LFP, or lithium iron phosphate. Some readers suggested that LFP is less combustible and less prone to overheating. Gupta says it’s difficult to call either chemistry safer overall; each comes with trade-offs. LFP is less energy-dense and reaches thermal runaway at a higher temperature—about 235 C, compared with about 200 C for NMC. It also releases fewer solid battery fragments when overheated. But it releases more gas, which can contain toxic and flammable substances. A chemistry’s advantages don’t erase its hazards.

Watch: Regina fire chief offers tips on avoiding battery fires

Lithium-ion batteries power devices from phones and tablets to e-bikes and e-scooters. Regina Fire Chief Layne Jackson advises keeping an eye on devices while they charge. The reminder is part of Regina Fire & Protective Services’ fire-prevention campaign. (Video: 2:11; October 5)

Watch: How do you put out a lithium battery fire?

Firefighters say these fires burn hotter, spread faster and are harder to extinguish than other fires. The video considers what it takes to put one out, including whether copious amounts of water are the answer. (Video: 1:36; October 16)

This article by Emily Chung was published by CBC News on Oct. 31, 2026, at 4 a.m. EDT and updated 11 hours ago. It includes an AI-generated audio version, estimated at seven minutes; the publisher warns that mispronunciations can occur.

Simple precautions matter most

Buy batteries and chargers bearing Canadian safety marks such as CSA, cUL or cETL. Match each battery with its proper charger; a plug that fits doesn’t mean the charger is safe for that battery.

Charge batteries on a hard, non-flammable surface where you can keep an eye on them. A couch or bed is a poor choice. Gupta also advises keeping a charging device away from the route you’d use to get out during a fire. Watch for warning signs: unusual heat, swelling, a bad smell, gas or smoke. Temperature-sensitive stickers such as TempAlert can help flag rising heat. Heat detectors or alarms offer another layer of warning; reader Adrian Hill, of Crystal Beach, Ont., installed one above his e-bike charging area. Gupta says a carbon monoxide detector may also help, since many lithium batteries release carbon monoxide when overheated.

If a battery overheats

Unplug it. If you can do so safely, move it to a non-flammable place such as outdoors, a sink or a bucket of sand. Giles says not to use it or charge it again, even after it cools.

Once it has cooled, take the battery to a technician or hazardous waste disposal site. Never put it in household garbage. Call2Recycle has more guidance on handling damaged, defective and recalled batteries. If the battery keeps heating up, or starts releasing gas or smoke, leave the area and call the fire department. “If you smell anything, that's bad,” Gupta said. “You should leave and call the fire department.” Lithium batteries power devices we rely on, and that won’t change soon. They’re generally safe, but failures happen. The practical point is simple: the right charger, a safer charging spot and a quick response to warning signs can reduce the danger.

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