---
title: "10 billion cells a year, 1,500 fires in Canada: how lithium batteries actually fail"
description: "Thermal runaway starts weeks or 20 minutes before the fire; the earliest warning sign is a battery that stays warm"
author: "Luis Goa"
published: 2026-10-31T08:00:00Z
modified: 2026-10-31T14:02:51Z
url: https://rews.cc/a/10-billion-cells-a-year-1-500-fires-in-canada-how-lithium-ba-4277a2
language: en
tags: ["batteries", "safety", "e-bikes", "fire", "regulation", "tech"]
publisher: "Rews (https://rews.cc)"
---

# 10 billion cells a year, 1,500 fires in Canada: how lithium batteries actually fail

*Thermal runaway starts weeks or 20 minutes before the fire; the earliest warning sign is a battery that stays warm*

By Luis Goa · October 31, 2026 · https://rews.cc/a/10-billion-cells-a-year-1-500-fires-in-canada-how-lithium-ba-4277a2

## In brief

- Canada saw more than 1,500 lithium battery fires last year, against more than 10 billion cells manufactured annually worldwide
- Failure usually builds through self-heating; a battery feeling hot while charging is the earliest sign, and the timeline ranges from weeks to 20 minutes
- LFP cells enter thermal runaway around 235 C versus 200 C for NMC, but eject more toxic and flammable gas — experts call it a trade-off
- A mismatched charger can push 80–90 volts into a battery designed for 40; certification marks CSA, cUL and cETL indicate tested chargers
- A battery that smells, swells, or vents gas or smoke means leave and call the fire department; cooled suspect batteries go to hazardous waste, never the trash

The base rate for lithium battery failure is low, and the failure mode is why it keeps making news. More than 10 billion battery cells are manufactured each year, and, as University of Waterloo fire safety engineering professor Vinny Gupta told [CBC in an explainer on battery fire risk](https://cbc.ca/news/science/lithium-battery-fires-consumer-safety-9.7401515), “we typically only hear about safety issues in just a few of them.” Canada recorded more than 1,500 lithium battery fires last year. Against even a conservative count of cells in circulation, the per-cell annual failure probability is tiny — but when a cell does fail, the result is a hot, fast fire that is hard to put out.

## How a battery fails

The mechanism is thermal runaway: a cell begins to self-heat, the heat accelerates the chemistry, the chemistry makes more heat, and the feedback loop ends in fire. Gupta describes the self-heating as exponential once underway, which is why the fire, when it comes, is “quite dramatic.” Consumer batteries ship with countermeasures — temperature sensors, pressure relief valves to vent flammable gases, and circuits that cut off overcharging — which is why the base rate is what it is.

![A stylized cutaway battery contains swirling red and pink flames that burst from its open end against a textured teal background.](https://rews.cc/img/073d6b6f83a368fea6808e541d13d718dec2deaa.webp)

The critical fact for owners is that a battery that has been safe can become unsafe, and the usual causes are mundane: a manufacturing defect, an e-bike or e-scooter collision, a dropped phone whose cracked screen is visible while internal battery damage is not, heat from charging in the sun, or simply wear from repeated charge cycles. Overcharging is one of the most common triggers, and it usually arrives via the charger. David Giles, CEO of Halifax-based TempAlert, points out that connectors fit many devices while voltages do not: the wrong charger “could be ramming, you know, 80, 90 volts into a battery only designed for 40. That’s when you start having a major problem.”

Failure is almost never instant. “Batteries don’t just go into thermal runaway instantly,” Giles said. “It progressively gets worse and worse.” The earliest indication, Gupta says, is a battery that feels hot to the touch while charging; unplug it and a failing cell will usually cool at first. Over repeated cycles, it stops cooling. How long you then have is genuinely unknown — both experts said so — because it depends on the damage inside. Giles put the range at days or weeks of continued use, down to as little as 20 minutes.

![A hand reaches toward a cracked smartphone connected to a charging cable, surrounded by a red glow and rising heat waves on a textured teal surface.](https://rews.cc/img/800a9a563b09b98bd05cf1f5ba615f9f50ad43b7.webp)

## NMC versus LFP

The two dominant chemistries differ in cathode material, and the safety comparison is a trade-off, not a ranking. LFP (lithium iron phosphate) is less energy dense and enters thermal runaway at about 235 C, versus about 200 C for NMC (nickel manganese cobalt), and it ejects fewer solid fragments when it fails. But it vents more gas, and Gupta notes that gas “is often laden with both toxic and flammable products.” His verdict: “It’s hard to really say if one chemistry is safer than \[the\] other … there are trade-offs.” Buying LFP is not a fire-safety fix.

## What to do about it

The interventions are cheap because the failure is signposted. Buy chargers bearing Canadian safety certification marks — CSA, cUL or cETL — and use the correct charger for each battery even when a wrong one fits the port. Charge on a hard, non-flammable surface, not a couch or bed, in sight, and Gupta adds one placement rule: do not put the charging device in the path you would need to escape a fire.

![Sunlight streams through an open coral door onto a tiled floor beside a table holding a potted plant and connected electronic devices.](https://rews.cc/img/7ab4a510b121ceda4a0568702ae16fa237aea1fa.webp)

Detection is a solved, low-cost problem. TempAlert’s heat-sensitive stickers turn from black to yellow at 60 C; one reader, Adrian Hill of Crystal Beach, Ont., installed a heat detector above the spot where he charges his e-bike; and a standard carbon monoxide detector adds a layer, because many lithium cells release CO when overheated. The warning signs themselves are: too hot, swelling, bad smells, gas or smoke.

If a battery overheats, unplug it and, if possible, move it outdoors or into a sink or bucket of sand. Do not charge it again even if it cools, Giles says; a cooled suspect battery goes to a technician or a hazardous waste site — Call2Recycle publishes procedures for damaged, defective and recalled cells — and never into the trash, where it becomes the waste facility’s fire instead of yours.

The line between watchful waiting and emergency is smell. “If you smell anything, that’s bad,” Gupta said. “You should leave and call the fire department.” Given 10 billion cells a year and counting, none of this moves the aggregate numbers much; it moves which side of the 1,500 your house is on.