Swollen, overheating, or smelly scooter battery: what to do immediately
A scooter battery that is swollen, overheats for no reason, or emits an unusual odor is a damaged battery. It should no longer be charged or used. If it is smoking, hissing, or crackling, do not touch it. Evacuate the area and call the fire department (18 or 112). If it appears calm, isolate it away from anything that could catch fire, then have it inspected and repaired by a professional. Here are the correct procedures to follow, and the mistakes to avoid at all costs.
The essentials
- Smoke, hissing, crackling, or flames: do not touch anything, evacuate, close the door, call 18 or 112.
- If the battery is swollen or appears suspicious, but is not actively leaking or making noise, immediately stop charging it and never charge it again.
- Isolate it in a well-ventilated area, on a non-flammable surface, away from flammable materials and people.
- Do not open it, do not drill into it, and do not throw it away.
- Have it inspected and serviced by a professional.
Identifying a damaged battery
The French National Institute for Occupational Safety and Health (INRS), in its information sheet on damaged lithium batteries, considers a battery to be damaged if it is deformed, swollen, or punctured, with or without leakage. It also considers a battery to be damaged if it discharges too quickly, overheats excessively, or emits a suspicious odor. On an electric scooter, this translates to:
- A deck or battery enclosure that is bulging, screws that are stripping, a cover that no longer closes properly;
- A warm battery when the scooter hasn't been ridden and isn't charging;
- A sweet, chemical, or burnt smell
- A battery that has experienced a significant impact (e.g., a fall, impact to the underside of the deck) or has been exposed to water
- A drastically reduced range, or a battery that discharges on its own within a few days.
The swelling is caused by gases produced inside the cells as they degrade. This is a sign that the cell's chemical composition is no longer stable. A swollen battery will not "deflate" or repair itself.
If it starts smoking or overheating: stop and call for help
A battery that is smoking, hissing, crackling, or spitting sparks may be experiencing thermal runaway: a self-sustaining reaction that spreads from one cell to another. The fumes are toxic and corrosive.
- Do not touch the battery and do not attempt to move it.
- Get everyone out, and close the door behind you to contain the smoke.
- Call the fire department: 18, or 112 from a mobile phone.
- Inform emergency services that the battery is a lithium battery from an electric scooter.
The mechanism behind thermal runaway, and why such a fire is difficult to extinguish, is explained in our guide lithium battery fire prevention.
If it is inflated but stable: isolate
No smoke, no noise, no intense heat: you have time to react calmly.
- Stop the charging process if it was in progress, by first unplugging the wall outlet. Never charge this battery again.
- Turn off the scooter and, if it has one, disengage the circuit breaker.
- Isolate it: If possible and without risk, move the scooter outdoors or to a well-ventilated area, onto a non-flammable surface (concrete, tile, earth), away from buildings, vehicles, flammable materials, and pedestrian areas. Otherwise, leave it where it is and move anything that could burn away from its vicinity.
- Monitor its performance without constantly watching it. If it starts to overheat, smoke, or whistle, follow the procedure described above.
- Contact a professional to arrange the inspection and maintenance.
Here's what you absolutely should *not* do
- Do not open the battery, and do not puncture a cell "to release the gas": this is the best way to cause an internal short circuit and a fire.
- Do not attempt to recharge it "to see if it still works."
- Do not ride, even for short distances: the vibrations and discharge current will worsen the condition.
- Do not dispose of it in household waste, nor leave it in a cellar or common area.
- Do not ship it by post or with a regular carrier: the transportation of damaged lithium batteries is regulated and requires specific packaging.
- Do not bypass the BMS (Battery Management System) if the battery no longer turns on; it may have shut it off to protect it.
| What you see | Emergency Level | Action |
|---|---|---|
| Smoke, hissing, flames | Immediate | Evacuate, close the door, call 18 or 112 |
| Swelling, battery overheating at rest | Raised | More charging, insulation, and troubleshooting |
| Unusual odor, no heat | Raised | More charging, insulation, and professional inspection |
| Sudden impact or water exposure, without any noticeable symptoms | To be controlled | Do not charge before inspection |
Why does a battery swell?
The most common causes are well-known: low-quality cells, overcharging by an unsuitable charger, excessively deep discharges, repeated overheating, a shock that has deformed a cell, or moisture that has caused a current leak. A very old battery can also eventually swell at the end of its life. The best practices that prevent these situations are detailed in our guides on charging and on the lifespan of a battery.
Workshop tip
Do not take any risks to save a battery: it can be replaced, you cannot. Once the battery is isolated and safe, contact us before any transportation: we will tell you how to proceed. Diagnostics in our workshop are based on our 30-minute labor rate, and our replacement batteries are assembled in our workshop using branded cells.
Frequently Asked Questions
Can a battery that is slightly swollen still be used?
No. Swelling indicates that cells are degrading and producing gas. Even slight swelling necessitates permanently stopping both charging and use.
Can only the swollen cells be replaced?
This is not a DIY project. A battery with swollen cells must be inspected by a professional, who will determine whether the battery pack can be safely repaired. In most cases, it will need to be replaced.
Should you pour water on a battery that is smoking?
Your priority should be to get out of the area and call for help. Extinguishing a large lithium battery fire is a job for firefighters. It can reignite long after it appears to be extinguished, and the fumes are toxic.
Where can I dispose of a scooter battery that is no longer working?
Never throw it in the trash. A used but still functional battery should be deposited at a designated collection point or returned to the seller. A damaged battery must be handled by a professional: seek advice before moving it.