More and more attention has been paid to the issue of e-bike safety in Toronto as various city bodies put e-bike and e-scooter restrictions on their radars.
The TTC is looking into a seasonal winter ban on such vehicles. At the same time, the Toronto Police Service (TPS) is currently engaged in a campaign to step up enforcement of unsafe e-bike and e-scooter use on the city’s streets.
TorontoToday found the there’s more than meets the eye behind TPS’ e-bike crackdown, but questions remain regarding the safety of e-bikes in winter conditions, particularly the lithium-ion batteries that power them.
The TTC board voted to put a hold on its proposed winter ban on e-bikes after it was revealed the transit agency’s Racial Equity Office was not formally consulted on how the ban might impact vulnerable groups — namely food delivery workers. The issue will be put to a vote again come Dec. 10 after additional analysis is completed.
What sparked the e-bike safety debate?
E-bike battery safety landed on the TTC’s agenda after an e-bike caught fire inside a Line 1 subway car on New Years’ Eve last year, sending three people to the hospital.
This is the only known e-bike battery fire in Toronto’s transit system. Interim Fire Chief Larry Cocco told the TTC board in October the incident could have been a lot worse if the subway car hadn’t pulled up to the next station moments after the fire broke out.
If TTC riders hadn’t been able to quickly exit onto the platform, “there would have been critical injuries and or possible death,” he warned.
Cocco said there is a “low probability” of e-bike fires. That said, the fire chief noted there is an “extremely high risk” to people when e-bikes do go up in flames, as fire extinguishers are not effective when suppressing fires caused by lithium-ion batteries.
But is the risk of fire great enough to justify banning e-bikes and e-scooters on the TTC and potentially disrupting riders who bring their e-bikes on transit as a “last mile” mode of transport?
Three battery experts who spoke to TorontoToday were split on the issue. Two experts agreed restrictions were needed for e-bikes in the winter, with one going as far to say he wouldn’t want to ride a subway at any time of the year if an e-bike was present.
A third expert argued the risk has been blown out of proportion, given how rare e-bike fires are despite their increasing popularity.
The argument against e-bikes on the TTC
TTC staff recently argued in support of a seasonal ban on e-bikes — writing in a report that winter conditions can increase the risk of a lithium-ion battery catching fire due to temperature fluctuations and contact with road salt.
Ravi Kempaiah, a mechanical engineer and CEO of the electric battery company Zen Energy, said the TTC’s reasoning is sound. His main concern with e-bikes in Canada is the lack of federal regulation. He would like to see all e-bikes in the country go through safety testing and achieve certification.
Currently, there are no restrictions on importing or selling uncertified e-bikes in Canada. Manufacturers can choose to get their e-bike products “CE” or “UL” certified, referring to the Conformité Européenne and Underwriters Laboratories Of Canada certifications, respectively.
“Most [e-bikes] are imported from Asia with very little regulation or safety considerations,” Kempaiah said. “It’s like the wild west.”
Most of these cheaply made e-bikes don’t have sufficient ingress protection, Kempaiah warned, which protects the battery from outside conditions like road salt and humidity.
Kempaiah said if road salt, mixed with water, enters a lithium-ion battery it can cause corrosion. This can lead to short-circuiting and “very dangerous situations.”
This danger was demonstrated in Florida this September when Hurricane Helene flooded the state with salty water. Florida Fire Marshal Jimmy Patronis said there were 48 lithium-ion battery fires related to the storm surge.
Cold temperatures also pose a danger to lithium-ion batteries, Kempaiah said, due to a phenomenon called lithium plating.
When it's cold, lithium ions have a harder time flowing through the battery and can start to pile up on top of each other. In serious cases, these accumulations of ions can form microscopic needles that can damage the inside of the battery cell.
This can lead to a dangerous, out-of-control chemical reaction that causes the battery to heat up, triggering further chemical reactions, which in turn creates more heat and energy. This vicious cycle is called thermal runaway.
Thermal runaway in one battery cell can then spread to other cells if the battery doesn’t have the proper safety mechanisms. Kempaiah said cheap e-bikes have very simple battery structures, meaning each cell is welded very close to each other. When one cell goes into meltdown, it can quickly cause its neighbours to fail as well — a recipe for fire.
Kempaiah warned if an e-bike battery was damaged one winter, it might not catch fire until much later.
“You never know when they're going to [fail],” Kempaiah said, until “you're already on the verge of explosion.”
This is why Kempaiah agreed some restrictions for e-bikes on the TTC are necessary, though he stressed the danger is year-round, not just in the winter.
Michael Fowler, a University of Waterloo professor and Canada Research Chair in Zero-Emission Vehicles & Hydrogen Energy Systems, agreed the danger of e-bike batteries is a year-round concern but stressed that “quality matters.”
“Cheap batteries and cheap chargers” have a higher risk of going into thermal runaway, he said.
With a better quality battery, the risk of fire decreases, Fowler said.
There are a number of best practices people can follow to minimize stress on the battery, like always charging at room temperature and regularly checking for damage.
Fowler said ensuring all e-bike batteries in Canada are safety certified is the best way to prevent fires, but until then, the danger of cheaply-made batteries shouldn’t be ignored.
“I wouldn’t go on the subway myself with those batteries coming too,” he added.
The argument in favour of e-bikes
Oliver Trescases, a University of Toronto professor and Canada Research Chair in Power Electronic Converters, told TorontoToday the concerns raised by Fowler and Kempaiah are valid, but the risk of e-bike fires has been greatly overstated.
“It’s incredibly important to highlight that these fires are rare, especially given the growing number of e-bikes,” Trescases said.
When it comes to the danger of lithium ions piling up on top of each other within the battery, Trescases said there is “minimal risk” of this happening when the battery isn’t actively being charged. There is also an opposite force called lithium stripping that can help integrate those built up lithium ions back into the battery.
Trescases advised riders to allow their e-bikes to warm to room temperature after use in cold conditions in order to reduce risk.
He also noted most modern e-bike batteries are equipped with management systems that prevent batteries from being charged in unsafe conditions, such as extreme cold, further reducing risk.
In his view, lithium plating doesn’t pose a significant issue in the winter. Exposure to saltwater from winter roads however, is a larger problem.
“Salt from the roads, combined with wet conditions, creates a highly conductive mixture that can seep into damaged or low-quality enclosures, causing dangerous short circuits,” he said.
This is why battery experts advise regularly checking the exterior of batteries for damage.
Overall, Trescases said operating e-bikes in the summer is slightly riskier than in the winter, because “high temperatures can accelerate chemical reactions within the battery.”
This causes the battery to degrade faster and, “in rare cases, thermal events,” he said.
“In summer, especially on longer rides or uphill terrain, batteries under continuous load in hot weather can reach high temperatures faster,” he explained. “Unlike winter, where low temperatures mainly slow ion movement and reduce performance, summer heat poses a greater risk of gradual component wear and, in extreme conditions, overheating.”
When a battery overheats, it can lead to thermal runaway and fire.
Like the other experts TorontoToday spoke to, Trescases said the single most important step to ensuring e-bike battery safety is to promote certification and to get more e-bikes manufactured in Canada, specifically for the Canadian climate.
“Addressing climate change can be a win-win if we’re not stuck importing cleantech solutions from other countries,” he said.
During the TTC board meeting when the seasonal ban was put on hold, Coun. Dianne Saxe noted the e-bike that caught fire inside Line 1 was an uncertified bike.
While she acknowledged the Dec. 31, 2023, fire was “very frightening,” she argued the proposed ban is “an over-the-top response to a problem we haven't had yet.”
“There hasn't been a fire with a certified battery as far as I know in any transit system in Canada,” she claimed.
Instead of outright banning e-bikes during the winter, Saxe would like the TTC to adopt Metrolinx’s regulations.
Metrolinx, which operates GO Transit, updated its e-bike policy in April this year to ban uncertified e-bike batteries. Metrolinx staff have been directed to inspect passengers’ e-bikes before boarding and affix a tamper-proof seal to e-bikes that meet the requirement.
“We should have consistent, clear rules,” Saxe said during the board meeting. “Many, many people use the [TTC and Metrolinx systems] in an integrated fashion and we shouldn't have separate rules without a really good reason.”
She argued the proposed ban would leave gig workers, who may bring their e-bikes on the TTC to get downtown, out to dry.
“What are they supposed to do? Starve for six months of the year? Are they supposed to buy a car and then drive around downtown Toronto trying to deliver their sandwiches? It doesn't give them a way forward,” she said.
The TTC should be encouraging climate-friendly modes of transportation, not banning them, Saxe argued.
