Swollen Lithium Battery? How to Spot It, Handle It and Recycle It

Robot vacuums, drones, RC cars, desktop robots, phones and power banks almost all run on lithium batteries. They're safe most of the time, but after long use, a drop, prolonged heat or improper charging, they can swell.

Swelling isn't just “the battery is old and runs out a bit faster.” In its overview of lithium-ion safety, Battery University lists hissing, bulging and electrolyte leakage among the signs of a failing battery. The US Federal Aviation Administration (FAA) also warns that lithium-ion batteries can go into thermal runaway when damaged, overheated, wet or overcharged — possibly with no warning at all.

How to tell a battery is swollen

You don't always have to open the device. Watch for these signs:

• A deformed case: the back cover lifts, seams widen, or the screen or a panel is pushed up
• A removable battery pack rocks on a table instead of sitting flat
• The battery won't slide in, or the latch won't close once it's in
• It gets noticeably hot while charging or in use, or smells odd
• Leaking, smoke or hissing — these are already dangerous; follow the warning above

Shorter runtime or fast drain alone doesn't necessarily mean swelling, but as soon as you see any change in shape, treat it as a swollen battery.

Found a swollen battery? Do these 4 things first

1. Stop using it and don't charge it again. Don't try to “make do for now.”
2. Disconnect power and switch it off. If it's charging, unplug the charger first. But note: Battery University points out that simply disconnecting the charger won't necessarily stop a failure that's already under way, so do the next step too.
3. Move it somewhere safe. Battery University advises that if a battery overheats, hisses or bulges, you should immediately move the device away from flammable materials and place it on a non-combustible surface, such as a tiled floor or a metal tray. Not on a bed, a sofa or in a cardboard box.
4. Then remove it, if it's designed to be removable. Batteries meant to come out — robot vacuum packs, drone batteries — can be removed per the manual after switching off. Don't pry out built-in batteries yourself (phones, tablets and many robot vacuums): pry tools and screwdrivers can easily puncture an already swollen cell.

Things you must never do

• Don't puncture or squeeze it, or try to “let the air out.” Swelling usually means gas has built up inside the cell; breaching the casing can cause a short circuit and fire immediately.
• Don't keep charging it, and don't try to “revive” or “repair” it.
• Don't leave it somewhere hot. Sunny windowsills, next to heaters and cars in summer are all out.
• Don't throw it in household trash or the recycling bin. The EPA notes that batteries mixed into trash or recyclables can be crushed during transport and sorting and start fires.
• Don't casually mail it or take it on a plane. The FAA prohibits damaged or recalled batteries on aircraft, in both carry-on and checked bags. If you must ship one, tell the carrier honestly and follow their requirements.

Temporary storage and recycling

Before taking it to be recycled, follow the EPA's advice:

• Put each battery in its own plastic bag
• Cover the terminals with non-conductive tape such as electrical tape to prevent shorts
• Keep it somewhere cool and away from flammables, not mixed with keys, coins, screws or other metal bits

Then get it recycled soon: contact the device brand's after-sales service, or use a battery drop-off point according to local waste rules. The EPA also reminds us that even a worn-out battery may hold enough energy to injure people or start a fire, so don't keep it at home indefinitely.

Flying with batteries

Taking the FAA's rules as an example:

• Spare lithium batteries (including power banks) must be in carry-on bags, never checked
• Protect the terminals from short circuits: keep the original packaging, tape them, or use a battery pouch
• A single lithium-ion battery is generally limited to 100 Wh. The watt-hour rating is usually printed on the battery; if not, estimate it by multiplying voltage (V) by capacity (Ah). For example, a 14.4 V, 2.6 Ah battery is about 37 Wh
• Damaged or recalled batteries aren't allowed on planes

The FAA also notes that many airlines have stricter rules. For domestic flights in China or flights in other countries, follow the latest rules of the local aviation authority and your airline.

Reducing risk day to day

Battery University has some very practical advice:

• Avoid heat. Heat combined with a full charge stresses lithium batteries more than normal cycling. Store them somewhere cool and partially charged when not in use.
• Don't leave them fully drained for long. Charging a lithium battery after a long deep discharge can make it unstable.
• Don't charge below 0°C.
• Don't exceed the recommended charging current. Fast charging beyond spec harms the battery.
• Use batteries and chargers from reputable brands. Cells of unknown origin often come with no guarantee of quality or safety.

Also keep a close eye on batteries that have been dropped or got wet — both are on the FAA's list of factors that can trigger thermal runaway.

If it actually catches fire

Get out and call for help first; people's safety always comes first. Battery University notes that lithium-ion battery fires can be fought with water or a regular extinguisher, but ventilate well: burning batteries release toxic gases and smoke.

About our repair service

Our repair service is still being prepared. Once it opens, if your device needs a mail-in repair and its battery is swollen, please contact us first and explain — don't ship it straight away, and we'll advise based on the situation.

References

• Battery University: BU-304a: Safety Concerns with Li-ion
• US Federal Aviation Administration (FAA): PackSafe – Lithium Batteries
• US Environmental Protection Agency (EPA): Used Lithium-Ion Batteries