Lithium-ion batteries power many of the products people use every day, including smartphones, laptops, cordless vacuums, power tools, toys, e-bikes, e-scooters and portable chargers.
Most of these devices operate safely. However, fire departments and product-safety agencies are reporting a growing number of incidents in which damaged, modified, defective or improperly charged batteries overheat and ignite inside homes.
Charging is one of the most dangerous stages because electrical and chemical activity inside the battery increases as energy is being stored. A damaged cell, incompatible charger or faulty battery-management system can allow temperatures to rise rapidly and trigger a chain reaction known as thermal runaway.
Once this process begins, a battery can release smoke, toxic gases, intense heat and flames within seconds.
Battery Fires Are Increasing
A 2026 analysis published through the National Institute of Standards and Technology estimated that fires involving consumer lithium-ion batteries have been increasing by around 10 percent annually. The researchers also concluded that existing incident-reporting systems probably underestimate the true scale of the problem.
Local fire-service statistics show similar trends.
Toronto Fire Services attended 76 lithium-ion battery fires during 2024. That represented a 38 percent increase from 2023 and a 162 percent increase compared with 2022. By July 2025, firefighters had already responded to another 43 incidents.
Fire and Rescue NSW describes lithium-ion batteries as the fastest-growing fire risk in New South Wales. The service recorded 272 battery-related fires during 2023, averaging more than five incidents each week.
The growing number of batteries inside homes partly explains the increase. A household may now contain dozens of rechargeable devices, including several that use large and powerful battery packs.
Why Charging Can Trigger a Fire
A lithium-ion battery contains cells that store a large amount of energy in a compact space. During normal charging, the charger, battery-management system and internal safety components control voltage, current and temperature.
A fire can occur when this protection fails or when the battery is placed under electrical, thermal or physical stress.
Using the wrong charger can send an unsuitable voltage or current into the battery. A cheap or counterfeit replacement may not communicate correctly with the device’s battery-management system. Continuing to charge an already damaged battery can also increase internal pressure and temperature.
Charging on a bed, sofa or carpet creates another danger. Soft materials can trap heat around the device and provide fuel if the battery ignites.
The risk becomes more serious when charging continues unattended or overnight. A person may not notice early warning signs, and a fire can develop while occupants are asleep.
Health Canada states that failures can result from poor manufacturing, unsuitable designs or excessive electrical, mechanical and thermal stress during charging, use or storage. The agency warns that progression from overheating to fire or explosion can occur in a matter of seconds.
What Is Thermal Runaway?
Thermal runaway occurs when rising temperature inside a battery begins a self-sustaining chemical reaction.
The hotter the cell becomes, the faster its internal materials break down. That breakdown releases more heat, causing the reaction to accelerate further. A single failing cell can then heat neighboring cells and spread the reaction through the entire battery pack.
The battery may hiss, crack, swell, release gas, produce smoke or burst into flames. In larger packs, individual cells can rupture or shoot burning material into the surrounding area.
Lithium-ion battery fires can burn extremely hot and release toxic and flammable gases. They may also appear to be extinguished and then reignite because damaged cells continue producing heat. Health Canada describes these fires as difficult to extinguish and prone to reignition.
E-Bikes and E-Scooters Create Particular Risks
Large micromobility batteries contain more stored energy than batteries used in phones or earbuds. A failure can therefore create a more intense fire with faster flame growth.
The risk is higher when an e-bike or e-scooter uses an uncertified battery, a modified battery pack or a charger not approved by the manufacturer. Products purchased from unknown online sellers may lack proper safety testing or contain low-quality cells and electrical components.
Some users also replace batteries with higher-capacity versions, repair damaged packs themselves or use universal chargers. These modifications can bypass the protections built into the original product.
An e-bike charging near the front door of an apartment creates an additional life-safety hazard. If it catches fire, flames and smoke can block the main escape route before occupants have time to leave.
Toronto officials reported that many recent battery fires involved attempts to modify batteries or extend their usable life.
Everyday Household Products Can Also Catch Fire
The danger is not limited to electric bikes and scooters.
Cordless vacuums, power tools, lawn equipment, remote-control toys, laptops, phones, vapes and portable power banks can all contain lithium-ion batteries.
A recent US recall involving more than 500,000 battery-powered lawn tools followed 34 reports of batteries smoking, sparking or catching fire while they were being charged inside the affected tools.
Portable chargers have also been recalled after consumers reported overheating, swelling, fires and burn injuries. These incidents show that even a relatively small battery can cause a serious fire when it fails close to furniture, bedding, clothing or other combustible materials.
Warning Signs a Battery May Be Failing
A battery should not become excessively hot during normal use or charging. Some warmth can be expected, but a device that is painful to touch, smells unusual or becomes hotter than normal should be disconnected when it is safe to do so.
Swelling is another important warning sign. A swollen phone, laptop, power bank or battery pack may have internal damage or gas buildup. The product should not be pressed, punctured or forced back into shape.
Other warning signs include leaking fluid, discoloration, cracking, hissing, popping, unusual noises, reduced charging performance or smoke.
Health Canada advises consumers to stop using batteries that show overheating, shape changes, leakage, unusual odors or strange sounds.
A damaged battery should not be placed in household trash, where it may ignite after being crushed in a garbage truck or waste facility.
How to Charge Lithium Batteries More Safely
Devices should be charged with the cable, adapter and battery supplied by the manufacturer. When a replacement is needed, it should be purchased directly from the manufacturer or from a trusted seller offering an approved compatible product.
Charging should take place on a hard, stable and non-combustible surface. Batteries should not be charged on beds, sofas, carpets or underneath pillows.
The device should remain visible and within reach whenever possible. Charging should stop before the user goes to sleep, leaves home or enters another area for a long period.
Fire and Rescue NSW found that 73 percent of surveyed consumers charged devices while unattended, while 64 percent left products plugged in after charging was complete. More than half reported using low-quality chargers or batteries.
A charging e-bike, scooter or large tool battery should be kept away from doors, hallways and stairs. These areas must remain available as escape routes during a fire.
People should also avoid plugging several high-power chargers into overloaded extension cords or power strips.
Why Cheap or Counterfeit Batteries Are Dangerous
Battery safety depends on much more than the cells themselves.
A properly designed product includes temperature sensors, current protection, voltage controls and circuitry that stops charging when unsafe conditions are detected. Counterfeit or poorly manufactured batteries may omit these components or use ineffective substitutes.
The cells may also contain manufacturing defects, inconsistent materials or internal contamination that increases the risk of short circuits.
Health Canada warns that unknown, low-quality and counterfeit batteries may not have undergone appropriate safety testing. The agency recommends purchasing replacement batteries from trusted suppliers and confirming that they are compatible with the product.
A very low price can be tempting, particularly when replacing an expensive e-bike or power-tool battery. However, using an uncertified replacement can place the device, home and occupants at risk.
What to Do if a Battery Begins Smoking
A smoking, hissing or burning lithium-ion battery should be treated as an emergency.
People should leave the area immediately, close doors behind them when possible and call the local emergency service from a safe location. Occupants should not delay their escape to retrieve the device or move it outside.
A small battery can quickly erupt into flames or eject hot material. Larger packs may release flammable gas before ignition, creating an explosion risk.
Attempting to carry a burning e-bike, scooter or power-tool battery through the home can cause serious burns and spread the fire along the escape route.
Smoke produced by battery fires can contain hazardous gases and fine particles. People should not re-enter the building until firefighters confirm that it is safe.
Safe Disposal Is Part of Fire Prevention
Lithium-ion batteries should never be placed in household waste or normal recycling bins.
Terminals on loose batteries should be covered with non-conductive tape to reduce the chance of a short circuit. The battery should then be taken to an approved battery-recycling or hazardous-waste collection point.
Damaged, swollen or recalled batteries may require special handling. Consumers should contact their local recycling authority, fire department or product manufacturer for disposal instructions rather than transporting a visibly unstable battery without guidance.
The US Fire Administration provides additional information about charging, storing and disposing of household batteries safely. The National Fire Protection Association also offers consumer guidance on preventing lithium-ion battery fires.
The Main Safety Message
Lithium-ion battery fires remain uncommon compared with the enormous number of rechargeable products used each day. However, the consequences of a failure can be severe because the fire may develop rapidly, spread quickly and produce intense heat and toxic smoke.
Charging is a particularly important risk period, especially when a product is damaged, modified, uncertified or connected to an incompatible charger.
Consumers can reduce the danger by buying certified products, using manufacturer-approved charging equipment, keeping charging devices in sight and away from combustible materials, and stopping use at the first sign of battery damage.
The simplest rule is also one of the most important: do not leave large lithium-ion batteries charging while sleeping or away from home.
