E-Bike Battery Fires - Should You Be Worried?
The biggest risk appears to be for modified e-bikes or DIY conversions.
Battery fires involving e-bikes are on the rise and often in the news. We've reported on electric bikes catching fire on this site. But how common are they? If you own an ebike, how likely is it to catch fire, and what can be done about it?
Source: Electrical Safety First
How do e-bike batteries catch fire?
The lithium-ion batteries used in e-bikes, e-scooters and other Light Electric Vehicles (LEVs) can catch fire due to something called thermal runaway. Put simply, this happens when a fault within the battery - usually caused by a manufacturing defect, misuse or external damage - creates a short circuit that releases a lot of heat within a battery cell. This heat can initiate a chemical reaction that generates more heat, which causes the structure of the cell to collapse, which in turn creates more heat. This chain reaction can spread to other cells, releasing a large amount of energy and toxic gases over a few minutes. The fire can burn very hot, and because the chemical reaction doesn't rely on oxygen from the outside air, it can be difficult to put out.
Fortunately, thermal runaway is quite rare and largely preventable.
How common are e-bike battery fires?
It's hard to know exactly how many e-bike battery fires occur globally. However, a recent report from Electrical Safety First, the UK’s leading charity on electrical safety, shares what we do know about the UK figures. It says data obtained by Zurich Insurance UK revealed that e-bikes and e-scooters combined were responsible for 167 fires in the UK as a whole in 2021. In 2022, the London Fire Brigade reported attending 87 e-bike and 29 e-scooter fires in Greater London alone.
It's difficult to translate these numbers into the percentage of e-bikes catching fire because we don't know exactly how many e-bikes were in operation in greater London in 2022, or in the UK in 2021. However, according to Cycling Industry News, 160,000 e-bikes were sold in the UK in 2021, along with 175,000 e-scooters. And since sales grew steadily over the previous years, and e-bikes typically last for several years, we can be confident that there were several hundred thousand e-bikes and e-scooters in the UK in 2021, which could be compared to the 167 fires reported in that year.
Additionally, those sales figures don't count ebike conversion kits, whereas the fire report data counts converted bikes as e-bikes.
Helpfully, this study from Sweden called "Fires in electric vehicles in 2022" (translated), from the Swedish Civil Contingencies Agency, MSB, provides information on both the number of e-bike fires and the number of e-bikes sold in Sweden. It states that in 2022 there were 20 fires reported involving electric bikes and 38 for electric scooters. The main report reveals that there were a total of 608,000 electric bikes sold in Sweden between 2014 and 2022. This still doesn't tell us how many e-bikes were in existence in Sweden in 2022 because some may have been disposed of/ recycled, and some e-bikes sold before 2014 could still be in use. But if we use this number as a rough guide, the 20 electric bicycle fires in that year correspond to 0.003% or 1 in 30,000 e-bikes "on the road" catching fire in that year. If only half of those e-bikes were still in use in 2022, the odds would increase to 1 in 15,000. For comparison, the same report states that around 1 in 1,300 cars catch fire each year in Sweden, including from crashes and arson, although electric car fires are much rarer (around 1 in 30,000).
To be clear, the study doesn't say exactly how many e-bikes were in use in Sweden in 2022 so we can't give an accurate figure for the proportion that caught fire, but I think it's reasonable to conclude that the number is in the ballpark of one in 10,000 - it's certainly not 1 in 1,000 or 1 in 100,000.
Reported EV and LEV fires worldwide in the first half of 2023. Source: EVFireSafe
How dangerous are e-bike battery fires?
Although battery fires are relatively rare, several people have been killed as a result of e-bikes and e-scooters catching fire in their homes. Media analysis from Electrical Safety First recorded 36 instances where an e-bike or e-scooter battery fire led to a property fire in the UK over the 12 months between April 2022 and March 2023. Of these, 81% occurred in domestic accommodation and half were at night. In the first three months of 2023 alone, four people died due to e-bike and e-scooter fires in the UK. In New York City, fire officials reported six such deaths in 2022 and five in the first four months of 2023.
Emma Sutcliffe of EV FireSafe discusses EV and LEV fire safety on the Fully Charged Podcast.
But to get a sense of how dangerous e-bike fires are, we need to zoom out to the global level. Worldwide data on battery fires is collected by EV FireSafe, a firefighter-led organisation funded by the Australian Government to research electric vehicle battery fires and how to deal with them. Their research is referenced by national fire agencies around the world. While they were unable to put a figure on the total number of Light Electric Vehicle fires globally, they recorded 138 injuries and 36 fatalities due to LEV fires in the first half of 2023.
Thirty-six fatalities in 6 months may sound alarming, but it's worth keeping in mind that there were an estimated 300 million LEVs globally in 2023. By comparison, in the UK alone there were 1,633 road collision fatalities in 2023, plus an estimated 10,000 early deaths due to air pollution, spread among just 41 million road vehicles (cars, vans, buses etc.).
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So while the fatalities from LEV fires are tragic and growing in frequency, the danger to life from other modes of transport is orders of magnitude higher on a per-vehicle basis*. This is relevant because a significant percentage of e-bikes are used as a direct replacement for cars.
*Sidenote: of course, cycling or e-biking for transport also carries a risk of being involved in a road traffic accident, but according to this Danish study the risk is greatly outweighed by the life-extending benefits of the exercise. Besides, I would argue the danger to cyclists from being hit by a car is an externalised risk of driving, not a risk created by cycling.
Another sidenote: according to the International Energy Agency, e-bikes, electric scooters and other light electric vehicles are already reducing oil demand by 100,000 barrels per day by replacing cars and motorcycles.
Which e-bikes are highest risk?
Electrical Safety First warns against e-bikes, conversion kits and batteries purchased from third-party sellers on online marketplaces, "which may not meet the correct safety standards," as well as "DIY modifications to the electrical systems (to prolong battery life and increase speed)." Another risk is from "universal" chargers which can sometimes over-charge the battery above the maximum voltage, leading to thermal runaway. ESF found almost 60 listings of substandard e-bike and e-scooter chargers for sale through third-party online sellers. This point was also emphasised by EV FireSafe.
According to Electrical Safety First, the biggest risk is for DIY e-bike conversions and modifications. Source: Electrical Safety First.
 | Many conversion kits available online do not include the battery, an essential component of any e-bike. The selection of a suitable battery and charger is left to the consumer to source and ensure compatibility. When a consumer converts a standard bicycle to an e-bike, in the eyes of the law, they take on the role of a manufacturer (perhaps unknowingly), so, take full responsibility for safety and conformity to applicable legislation. |
It's not clear how many of the LEV fires mentioned above were due to sub-standard batteries, dodgy chargers or DIY modifications, but it stands to reason that e-bikes from reputable manufacturers with the correct charger should have a lower risk of failure than average.
To be clear, this is not to say that everyone should avoid conversion kits or entry-level e-bikes (these are the most accessible, sustainable and affordable modes of transport available to many people) but beware of homemade hacks or dodgy deals on eBay or Amazon.
It's also worth bearing in mind that some bike shops are refusing to service low-quality e-bikes. According to EV FireSafe, "This is leading to ‘Backyard’ servicing, with horrific results."
ESF recommends buying only from reputable retailers, using the correct charger and compatible batteries. If possible, it's a good idea to charge your e-bike outside of the home, in a shed or communal bike store. If charging indoors, avoid charging overnight, do it somewhere away from the exit, and unplug the battery once it's charged. For the full list of safety recommendations, click here.
Risk profile of different battery-powered devices. Source: EVFireSafe
Why do electric bikes catch fire more often than electric cars?
When talking about e-bikes and e-scooters, EV FireSafe has started using the term Personal Mobility Devices (PMDs) instead of Light Electric Vehicles (LEVs), to prevent confusion with road-registered electric vehicles, such as electric cars. This is because the batteries in electric cars are much less likely to catch fire than PMDs like e-bikes. In fact, EV FireSafe estimates a probability of 0.0012% for electric cars, which they say is considerably lower than the risk for PMDs or internal combustion cars. This is echoed by the Swedish study mentioned earlier.
Differences between LEVs (such as e-bikes) and roadgoing EVs. Source: EVFireSafe
According to EV FireSafe, this difference in safety between e-bikes and electric cars is due to a range of factors, "but primarily the quality of the lithium-ion battery cells & battery management system; in EVs they're high quality and subject to stringent regulation, in PMDs, they're often very low quality and unregulated."
Key Points
• The batteries in e-bikes (and other Light Electric Vehicles such as e-scooters), can catch fire while charging, which can cause a particularly intense and dangerous fire especially if charged indoors.
• Such fires are getting more common and have caused fatalities, but they remain very rare compared to the number of e-bikes and other LEVs in existence. Car accidents and air pollution cause hundreds of times more deaths on a per-vehicle basis, so fire risk shouldn't put you off getting an e-bike, especially if you plan to use it instead of a car.
• The e-bikes most at risk of catching fire are those that have been modified or charged incorrectly, or those from third-party online sellers which do not meet safety regulations.
• If charging an e-bike inside the home, it's best practice to avoid charging overnight and keep it away from the exit.
• For well-made and properly used e-bikes, the fire risk is extremely low.
Acknowledgements
I'd like to thank Sara Mills of EV FireSafe for her feedback on this article.
I'd like to thank Sara Mills of EV FireSafe for her feedback on this article.
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Serious side note, imagine taking a tumble, you bike stars a fire and you burn down your local riding area. Won't be very popular with your biking buddies.
They account for 1:8 fires attended to by the fire department and over 10% of fire related deaths.
TLDR: Always buy LifePO4
no one on the planet is 100% clear in this regard, but not driving a Tesla is the first thing you can do to mitigate your involvment....
We are all consumers and the best thing we can do is vote with our dollars, voices, and votes - and demand adherence to environmental, social, and humanitarian standards from the companies we buy from, and the governments we elect.
Only if their shovels and pick axes are carbon neutral
Uhh...burn???
So they just pulling entire batteries outta this mine that doesn't exist yet?
That's not to say that legit batteries don't have their issues, I've had a MacBook battery swell and get very hot. But it's rare.
Me too, but apparently both terms are correct:
www.merriam-webster.com/dictionary/jerry-rigged
www.merriam-webster.com/dictionary/jury-rigged
Jerry rigged wins for me
"Have you been in a conversation lately and heard any rendition of jury-rigged? I was in a conversation the other day when I heard “jimmy rigged” for the first time, so I decided to figure out which one is right …
and discovered the saying has quite the storied history. Turns out “jury rigged” was a sailing term that most likely originated near or before the 17th century. When a mast was damaged, due to a storm, battle, or wear-and-tear, it would need to be “jury-rigged” back into working condition. The connection between the word and sailing itself is unclear, but perhaps “injury” combined with “rigged” has some credence. Hmmm, I always thought it derived from a rigged jury. “The jury was rigged and so is this contraption.”
The alternative term “jerry rigged” found its footing in World War II. To keep equipment functional toward the end of the war, the axis would oftentimes resort to scavenging for parts. British troops referred to a German as a Jerry. Thus, the term “jerry rigged” was embraced to refer to patchwork jobs.
The new-age version of this reference would be “jimmy rigged.” This term, according to Urban Dictionary, is a cast off of “jury rigged” and denotes that the fixed-up contraption will most likely not work."
(www.raisingjane.org/journal/17945)
Not mountain bikes.
There is a dramatic range of risks depending on the design and execution of a vehicle battery pack. At Alta, despite having the highest energy densities (at the time) of any vehicle pack ever commercialized, our packs were inherently propagation resistant - tested to a P5 standard (5 simultaneous cell failures), which is a statistical impossibility outside of something like being crushed under a car or run through by a street post. It was an explicit conversation with everyone who joined our company that we held ourselves to that safety standard and would never except a customer death that was due to choices we made. However, I can say from conversations with engineers and executives at other manufacturers during our operating period (2010-2018 ), even large and "credible" ones that many did not even have the understanding of functional safety necessary to hold themselves to a meaningful standard. As noted in Seb's article, unlike combustion engines, charging is an activity that creates increased risk of a thermal event - this happens in people's homes, often at night while sleeping, so such ignorance was an unforgiveable sin in my opinion.
In the e-bike space, UL 2271 was created in 2018, and you should not buy a battery or bike that does not meet this standard. However, even this standard still doesn't cover thermal propagation. I hope someday that UL includes propagation testing in e-bike scale battery as they do in large format packs. Until then, I would only buy batteries from the largest manufacturers, no matter how tempting the value or claimed performance is from smaller or garage suppliers. The risk factors are 3-fold:
1) the quality of the cells - cheap (typically chinese) cells can have failure rates that are a multiple of those from MFGs like Panasonic, LG, Molicell. A multiple failure rate means a multiple fire risk.
2) the design of the pack - as noted above, our pack design was inherently propagation resistant, which meant even with shit cells a fire was nearly impossible (*the be clear, we used panasonic and sony/murata cells... not shit)
3) the manufacturing control, quality, and traceability - our packs were assembled with electric torque guns and we recorded the final torques of every fastener in the pack. many manufacturers still use calibrated pneumatic tools which are not as precise and cannot record final torques, and small shops may not use torque wrenches/guns at all. A loose fastener can increase the shocks experienced by a cell 10X, and a free floating fastener is an instant short path.
In short, do not buy any pack that doesn't meet UL 2271 (and can provide the paperwork, not just a fake sticker), and you probably shouldn't buy a pack from a manufacturer that hasn't been doing this for a long time, at a large scale OR provides receipts (transparent published approach or test results) on the above 3 factors.
1. Statistics are scarce, so actual fire rates per 100,000 eBikes, not just raw numbers, are not available, which makes a lot of comparisons to other battery-powered vehicles moot, or misleading at best.
2. Tucked in at the end is "For well-made and properly used e-bikes, the fire risk is extremely low." Cheap eBikes are being sold in insane volumes, because they're less expensive. How many cheap EVs do you see catching fire? You don't, because there are so many safety hoops and regulations around selling a motor vehicle that cheap shit can't pass. I don't want regulaton on bikes more than anyone else, but in the world of "you get what you pay for" I'm not all that surprised to see fires on cheap eBikes. Show me how many Pivots, Ibis, Specialized, etc have caught fire and then we'll talk.
www.emtbforums.com/attachments/d58795f7-993c-43ae-b287-3adf43fda75a-jpeg.62823
@hohmskullkrishten: "Here, take my n=1"
Why those wankers buy e-bikes if it's to do this?
More importantly, whilst you're riding fewer laps, you're also upset and angered by us on our e-mtbs. On the rare occasion I come across "wankers" like you, it simply increases my satisfaction. Win for me. Lose for you.
The problem mostly comes from cheap battery with inconsistent cells and cheap controlers that allow the unconsistent cells to overcharge.
For model cars/planes batteries, we use chargers that equalize the charge of each cell and the packs are fitted inside a fire resistant bag during charge. But its not usable for a bike or a car.
Other causes of cells deterioration to avoid are overdischarge and storing at full charge.
To avoid these problems, batteries should be charged between around 30 to 70% if left unused for a week or more. This applies to any Lithium batteries including lights.
The UL label on your electronics unbelievably important, it means having an independent lab testing to to high standards. Cheap Chinese e bikes scare the sh!t out of me as a mechanic where they could cause a runaway fire from poorly or untested safety standards could destroy the whole shop and my means of making a living. Every e bike from a non supported motor brand in our shop has the battery removed before being left for repairs. Also we will only service motor systems we are trained and certified for.
Properly teaching our customers about charging and storage of e bikes is something we practice as well.
Life is not without risk, something the mtb community should know well. The level of risk with a well known and supported brand ( Shimano, brose, Bosch, Fazua, TQ) is very low if stored, charged and used properly. The cheaper bikes/systems are the ones I've seen in the media causing fires and such.
But I do have battery operated phones, computers, yard equipment and snow blower. So maybe???
The amount of unreported EV fires in places like Russia or China, Etc, is bound to be higher ....
Infact most studies on various subjects are based on what's reported, but are often NOT based on the real number because it's hard to get the true reported figured on anything in today's modern world of inaccuracies. Also places like China are not in the business of reporting on battery fires when they aiming to be a battery superpower.
youtu.be/j92Gt4VviSQ?si=EMGqgV42gi8xT9Ty
Haven't seen a single original Surron catch fire.
(Clicks send on a spartphone that lives in my pocket all day.)
I understand eMTBs and eMotos are not for everyone but my guess is the top e-Moto platforms SurRon, Talaria, E-ride Pro, Stark Varg are just as safe and well made as the best eMTBs - My best guess is the fire danger comes from low quality mass produced bikes out of China and the people trying to modify the batteries and controllers for more power
\m/
Also Pinkbike : tests Aliexpress knockoff brakes
This is a ridiculous statement.
Batteries have no place in things meant to be thrown around. Period.yoy crash your Tesla you get it checked out you crash your kenevo? You ride it home put it in your garage to charge... Comparing the two, like the author did above, is absurd and shortsighted.
Don't want to piss off those advertisers though right? And you will definitely keep advertising the shit out of these death traps
Put the suspect on an eBike: if they live, they are a witch. Burn them. Problem solved.
Put the suspect on an eBike: if they burn to death in a battery fire, they are a witch. Problem solved.
What say we start with Elon?
When they burn doesn't send CO2 to the atmosphère but rainbows and strawberry smoothies..
Batteries catching fire typically belong in Fox News anti-electric hitjob articles.