Every rechargeable fan eventually becomes a battery disposal problem. Most people handle it the same way they handle a dead flashlight, which is to say they throw it in the trash. That is the one option that is both illegal in many states and genuinely dangerous, because lithium cells start fires in garbage trucks and sorting facilities every week.
The five warning signs
A case that rocks instead of sitting flat, a seam that has opened, a soft or spongy spot, heat while the fan sits idle, or a sweet chemical smell. Any one of these means retire the unit. It does not matter how new it is or what the warranty page on a listing such as https://socoolfan.net/ says about coverage.
Why swelling happens
Gas builds up inside the cell as the electrolyte breaks down, usually after heat exposure, overcharging or physical damage. The pouch expands because it has nowhere to vent. A swollen pack is a cell that has already failed internally and is now sitting closer to the point of thermal runaway.
What not to do with it
- Do not press, puncture, pry or fold a swollen pack to make it fit.
- Do not put it back on a charger to see if it still works.
- Do not toss it in household trash or a curbside recycling bin.
- Do not store it in a drawer with loose metal or other batteries.
- Do not leave it charging while you are asleep or out of the house.
How to hold it until drop off
Put tape over any exposed contacts, place the unit in a nonflammable container such as a metal can or a sand filled bucket, and keep it outside, away from the house and the car. A garage attached to a bedroom wall is not outside.
Where it actually goes
Most metropolitan areas have a household hazardous waste day, a permanent county drop off, or a retail battery collection bin at a hardware or electronics store. Call ahead and say the words rechargeable lithium, because collection rules differ from the ones for alkaline batteries.
If it starts venting
A cell in runaway produces a hissing sound, thick acrid smoke and sometimes flame, and it will keep reigniting. Get people away, close the door, and call 911. Do not carry a burning pack through your house looking for the sink.
Preventing the whole situation
Heat is the main accelerant, so a fan that lives in a hot vehicle will show these signs years earlier than one kept indoors. Store at partial charge over the winter, use the supplied charger, and stop charging a hot unit until it cools.
Buying with disposal in mind
A sealed unit with a glued case is landfill on the day the cell fails. A model with a removable pack, or one that runs on a standard cell you can replace, gives you a repair path and a much simpler recycling trip.