Batteries & Safety

Pack basics

Packs Are Strings of Cylindrical Cells, Sized in Watt-Hours

A pack's energy in watt-hours is its nominal voltage times its amp-hour capacity. Energy, more than voltage, sets range.

Most e-bike and stand-up scooter packs use cylindrical cells. The 18650 cell is 18 mm across and 65 mm long; the 21700 is 21 mm by 70 mm and holds more energy per cell, and it has largely replaced the 18650 in new e-bike packs. Cells are wired in series to reach the pack voltage, about 3.6 V nominal per cell, so ten cells in series give a 36 V pack, 13 give 48 V and 14 give 52 V. Parallel groups add amp-hours. A battery management system watches each series group for overcharge, over-discharge, temperature and current.

The Bosch PowerTube line runs from 400 to 800 Wh at 36 V, and the Bosch DualBattery setup pairs two packs on cargo and touring bikes. The Segway Ninebot Max G30 scooter carries a 551 Wh pack. Range depends on watt-hours, assist level, rider and cargo weight, hills, tire pressure, wind and temperature; cold weather cuts usable capacity.

Chemistry and cell makers

Nickel Cells Dominate E-Bikes, LFP Is Common in Chinese Two-Wheelers

Western e-bike packs use nickel-rich cathodes, NMC (nickel manganese cobalt) or NCA (nickel cobalt aluminum), because they store the most energy per kilogram. LFP (lithium iron phosphate) cells store less energy by weight but resist thermal runaway better and last more charge cycles; they are common in Chinese electric two-wheelers, swap-network batteries and some seated scooters.

The large cylindrical-cell makers are Samsung SDI and LG Energy Solution in South Korea, Panasonic in Japan and Molicel (E-One Moli Energy, part of Taiwan Cement) in Taiwan, whose 4,500 mAh P45B is a 21700 high-power cell. Chinese makers including EVE Energy, Lishen and BAK sell 21700 cells that pack builders use in e-bike batteries. Large pack assemblers include Phylion in Jiangsu and Celxpert in Taiwan. Bike brands rarely publish which cells they use.

Integrated, removable, swappable

Packs Sit Inside the Frame, Clip On, or Swap at a Kiosk

Integrated packs sit inside the down tube and come out with a key or tool, as with the Bosch PowerTube. Removable packs mount on the down tube or rack and come off for charging indoors. Some lightweight e-bikes, such as those using the Mahle X20 system, use fixed internal batteries charged in place.

Swap networks remove home charging altogether. Gogoro in Taiwan reported about 677,000 battery-swap subscribers and more than 1.5 million batteries in service in the second quarter of 2026, and other scooter brands sell models built for its network. In China, swap operators serve mostly delivery riders: Zhizu, which filed for a Hong Kong listing in May 2026, reported about 22,400 swap cabinets in more than 90 cities at the end of 2025. Frost & Sullivan sized China's light-vehicle swap market at RMB 12.3 billion in 2025.

Fires

New York City Cut Battery Fire Deaths After Requiring Certified Packs

A lithium-ion cell in thermal runaway heats itself, vents flammable gas and can ignite neighboring cells in seconds. Uncertified packs, rebuilt or homemade packs, physical damage and mismatched chargers are the common causes. The FDNY counted 268 lithium-ion battery fires and 18 deaths in 2023, 277 fires and six deaths in 2024, and one death in 2025.

The CPSC identified 227 fire, explosion, overheating and smoke incidents with micromobility lithium-ion batteries from 2019 through 2023, with 39 deaths and 181 injuries; fires accounted for all 39 deaths.

Standards and law

Three UL Standards Anchor US Rules, Two EN Standards Anchor Europe

New York City Local Law 39 of 2023, in force since September 2023, bars the sale of e-bikes, e-scooters and their lithium-ion batteries unless certified to UL 2849, UL 2272 or UL 2271, with fines up to $1,000 per device. The CPSC published a proposed rule on June 24, 2026 (docket CPSC-2025-0012) that would make those three standards mandatory nationwide, add a reverse-polarity test and tamper-resistant enclosures, cover aftermarket chargers and conversion-kit parts, and require third-party testing for children's products. Comments closed August 24, 2026.

The EU Battery Regulation (Regulation (EU) 2023/1542) treats e-bike and scooter packs up to 25 kg as light means of transport (LMT) batteries. From February 18, 2027, each LMT battery needs a digital battery passport, and the pack and its cells must be removable and replaceable by an independent professional. China's mandatory GB 43854-2024 standard for e-bike lithium-ion batteries up to 60 V took effect November 1, 2024. Compliance detail for each regime is at BatteryComplianceGuide.com.

Charging

The Charger Must Match the Pack

A charger is set for one pack voltage and chemistry: 42 V full charge for a 36 V NMC pack, 54.6 V for 48 V. A mismatched or uncertified charger can overcharge cells past what the battery management system can stop. UL 2849 tests the charger as part of the e-bike system, and the CPSC proposal would cover chargers sold separately. FDNY guidance is to charge on a hard surface away from exits, unplug when full and never charge unattended overnight.

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