LiPos › Swollen or damaged LiPo batteries and fire safety
Swollen or damaged LiPo batteries and fire safety
A puffed, dented or punctured LiPo is a warning. Here is how to spot trouble, what to do with a bad pack and what the fire service says about battery fires.
Warning signs
- Swelling or puffing. The pack looks fat or the wrapper bulges.
- Dents, cuts or punctures after a crash.
- Heat while charging or when idle, or a pack that is much hotter than the others after use.
- Damaged leads or connectors, exposed copper, melted plastic.
- Smell, hissing or smoke.
BYU's guide says never to use or charge a LiPo that is swollen, damaged or punctured. West Yorkshire Fire and Rescue says not to use batteries with damaged or possibly damaged casings, or ones that look swollen or deformed, and not to crush, puncture or submerge batteries.
What to do with a bad pack
- Stop using it and do not charge it.
- If it is not hot or smoking, move it carefully outside or to a safe, non-flammable place such as a stone or metal surface, away from the house, and not on the sofa or in a drawer.
- Do not puncture it to discharge it.
- Get advice on safe disposal from your council or recycling centre: see disposal and recycling.
The CAA's advice for flying is the same in spirit: batteries that are damaged, overheating or swelling should not be used or carried on a plane.
After a crash
A drone or car crash is the most common way a LiPo is damaged. Even if it looks fine, inspect the pack closely before the next flight and watch it for a while after: a damaged cell can fail later. Many pilots retire any pack that has taken a hard hit. See RC, drone and FPV use.
Reducing the fire risk at home
- Never leave batteries charging unattended, including overnight.
- Charge away from escape routes, hallways and combustible materials, ideally where you can see them.
- Unplug chargers when batteries are full and do not leave them on continuous charge.
- Do not cover chargers or batteries with bedding.
- Avoid overloaded sockets and extension leads.
- Use the correct charger from a reputable source. See charging.
- Have working smoke alarms where you charge.
These points come from West Yorkshire Fire and Rescue's lithium-ion safety messages.
If a battery catches fire
West Yorkshire Fire and Rescue says battery fires spread quickly, are hard to put out and produce highly toxic smoke. Its message: get out, stay out, call 999. Do not try to be a hero with a small pack in the house. A LiPo bag or a fire-resistant surface can help prevent spread, but they do not make a fire safe to ignore.
Prevention beats cure
Most failures follow a pattern: a crash, a wrong setting or a pack left in a hot place. Build checks into your routine: look at the pack before charging, at the field before flying and again after landing. A minute of looking costs nothing compared with a fire.
For longer term storage, see storage voltage.
This is general information, not a substitute for the instructions that came with your battery and charger. If your manufacturer's advice differs, follow the manufacturer.
Frequently asked questions
Why do LiPo batteries swell?
Swelling shows gas inside, usually from damage, over-discharge, overcharge or age. Whatever the cause, stop using the pack.
Can I use a slightly puffy LiPo?
No. BYU says never to use or charge a swollen pack.
What do I do if a LiPo catches fire?
Fire services say get out, stay out and call 999. Battery fires spread quickly and the smoke is toxic.
Does a LiPo bag make charging safe?
It helps contain a fire but you must still never leave a battery charging unattended.