Battery Fires & Certification

Why packs fail

Thermal Runaway Starts in One Cell and Spreads Through the Pack

A lithium-ion cell that overheats past its stable range starts reactions that make more heat than it can shed. The cell vents flammable gas, ignites, and heats its neighbors until the whole pack burns.

An e-bike pack holds 40 to 70 cylindrical cells, and a 52 V pack can hold more than 1,000 Wh. Once one cell fails, the fire spreads cell to cell faster than a household extinguisher can stop it, and the vented gas can flash across a room. Nickel-rich NMC and NCA cells release more heat in runaway than LFP cells. A battery management system cuts off charging and discharging at set voltage, current and temperature limits, but it cannot stop a cell that has an internal short from damage or a manufacturing defect.

Fire data

New York City Fires Kept Rising While Deaths Fell

The FDNY counts every structural and non-structural fire caused by lithium-ion batteries, nearly all from e-bikes and e-scooters.

New York City deaths peaked at 18 in 2023, a year that included the April fire at an e-bike repair shop in Chinatown that killed four people. Fires kept climbing to 277 in 2024 while deaths fell to six. By July 22, 2026, the FDNY had recorded 235 lithium-ion fires, up from 138 at the same point in 2025, with most of the increase in non-structural fires: 137 against 48. A June 26, 2026, fire in Queens caused the city's first lithium-ion battery death of 2026.

The London Fire Brigade recorded 206 e-bike and e-scooter fires in 2025, its highest count, against 171 in 2024 and 12 in 2019. E-bikes caused 171 of the 2025 fires. Two people died in 2025 and five since 2023; none of the five owned the e-bike involved.

Across the United States, the CPSC identified 227 fire, explosion, overheating and smoke incidents with micromobility lithium-ion batteries from 2019 through 2023. Fires made up 195 of them and caused all 39 deaths; 181 people were injured.

China has the largest fleet, more than 350 million e-bikes. The National Fire and Rescue Administration under the Ministry of Emergency Management received reports of 21,000 e-bike fires in 2023, up 17.4% from 2022. A February 23, 2024, fire that began with an e-bike in a residential building in Nanjing killed 15 people. In 2024, after a national safety campaign and the new battery standard, e-bike fires fell 42.2%, from 5.6 to three fires per million e-bikes, and deaths and injuries together fell by more than 90%. The ministry has not published a national e-bike death total.

In Australia, Fire and Rescue NSW counted 23 lithium-ion fires involving e-micromobility devices in 2022, 67 in 2023 and 93 in 2024.

Standards

UL 2849 Tests the Whole E-Bike System, UN 38.3 Only Covers Shipping

Some standards test a complete vehicle's electrical system, some test the pack alone, and some test only the cell. A pack can pass UN 38.3 for shipping and still fail UL 2271.

UL 2849 tests the battery, charger, motor, controller and wiring of an e-bike as one system: overcharge, forced discharge, short circuit, imbalanced charging, temperature, crush, impact, drop and water exposure, plus insulation and overcurrent protection. UL 2272 runs a similar set for stand-up e-scooters, hoverboards, e-skateboards and e-unicycles, including vibration, shock, motor overload and water exposure. UL 2271 covers the battery pack alone, including replacement packs. The CPSC proposal would add a reverse-polarity test to all three, and a tamper-resistant enclosure requirement and a post-discharge charge test, which requires the BMS to block charging when cells are too hot, to UL 2849 and UL 2271.

China's GB 43854-2024, issued by the Standardization Administration of China, sets six cell tests and 22 pack requirements. A fire in one cell must not spread quickly through the pack, overcharge and short-circuit tests run with one protective part disabled, the pack must exchange a handshake with its matched charger before charging, and each pack carries a unique code marked to stay legible after a 950°C fire. The standard covers e-bikes only; e-scooters, e-motorcycles and e-tricycles fall outside it.

Laws

Certification Became Law City by City in the US, Nationwide in China

US federal law still treats UL 2849, UL 2271 and UL 2272 as voluntary. Cities and states made them mandatory first.

New York City Local Law 39 of 2023 has barred the sale, lease or rental of e-bikes, e-scooters and their batteries without UL certification from an accredited laboratory since September 2023. Local Law 42 of 2023 bans assembling or reconditioning packs from cells taken out of used batteries and selling such packs. New York State followed in July 2024, when Governor Kathy Hochul signed S.154F, in force since October 9, 2024, with fines of $500 for a first violation and up to $1,000 for repeats. California SB 1271, signed September 27, 2024, has required accredited-lab certification and a permanent mark since January 1, 2026, and extends to rentals on January 1, 2028. Illinois Public Act 104-0414, the Micromobility Fire Safety Act, took effect January 1, 2026, and bans packs built from used cells.

The CPSC published its proposed rule on June 24, 2026, and comments closed August 24, 2026. It would cover complete e-bikes and e-scooters, replacement packs and conversion-kit components, give makers 180 days after a final rule to comply, limit stockpiling of noncompliant products in that window, and require third-party testing for children's products. No final rule had been published by mid-October 2026.

The EU Battery Regulation classes sealed packs up to 25 kg that power e-bikes and e-scooters as light means of transport (LMT) batteries. Its fire-safety article applies only to stationary storage; e-bike fire safety in the EU runs through EN 15194 and the Machinery Directive, and the Machinery Regulation (EU) 2023/1230 replaces that directive in January 2027. In China, e-bike lithium-ion packs and chargers need the CCC mark to be made, sold or imported since November 1, 2025, and the State Administration for Market Regulation requires a traceability QR code beside the mark on newly certified packs from March 1, 2026. The United Kingdom passed the Product Regulation and Metrology Act in 2025; the London Fire Brigade has asked the government to use it for e-bike battery rules. Compliance detail for each regime is at BatteryComplianceGuide.com.

Certification marks

A Real Mark Names the Lab, the Standard and a File Number

In the US, certification means a Nationally Recognized Testing Laboratory (NRTL) tested the product and keeps checking the factory. UL is one NRTL among several.

OSHA recognizes NRTLs, including UL Solutions (UL mark), Intertek (ETL mark), CSA Group (CSA mark), TUV SUD America, TUV Rheinland of North America and SGS North America. Any of them can certify to UL 2849, UL 2271 or UL 2272; the standard number is the same whichever lab does the testing. A genuine mark shows the lab's logo, the word "Listed" or "Certified," and a file or control number that appears in the lab's online directory: UL Product iQ, the Intertek Directory of Building Products and listed equipment, or the CSA certified product listing.

Phrases such as "meets UL standards," "UL compliant," "UL tested cells" or "UL pending" do not mean the bike or pack is certified. Certified cells inside an uncertified pack do not make the pack certified. In January 2026, Amazon and UL Solutions sued four Chinese and Hong Kong companies and one individual selling Aipas and A4 e-bikes and e-scooters with false UL marks; Judge Jamal N. Whitehead of the US District Court in Seattle signed a consent judgment and permanent injunction in July 2026.

Safe use

Charging Indoors Overnight Is the Highest-Risk Habit

Most fatal fires start at home, during or right after charging, near the only exit.

• Use the charger that came with the bike or scooter, or one the maker lists for that pack.
• Charge on a hard, non-flammable surface, away from doors, hallways and stairwells, and unplug when full.
• Do not charge while asleep or away, and keep a working smoke alarm in the room.
• Let a pack cool after riding before charging, and do not charge below freezing.
• Stop using a pack that is swollen, dented, leaking, hissing, smells sweet or chemical, or runs hot; take it to a battery recycler.
• Have a pack inspected after a crash or a soaking, even if it still works.
• Do not buy rebuilt packs, packs with cells from used batteries, or unbranded replacement packs.
• If a pack starts smoking or burning, leave, close the door behind you and call the fire department.