A swollen battery is the one fault that is genuinely urgent
The short answer
A swelling battery is a lithium cell producing gas as it fails. It lifts the screen, bows the back and stops the phone sitting flat. Stop charging it, stop using it, do not press on it and do not try to lever the phone open. It is the one phone fault we treat as urgent.
How to tell
The table test is the reliable one and it takes five seconds. Put the phone face down on something genuinely flat and press diagonally opposite corners in turn. A healthy phone sits solid. A swelling one rocks.
A phone that has been dropped can also have a lifted screen, so the distinguishing question is whether anything happened to it. A screen lifting on a phone nobody dropped is a battery until proven otherwise.
- The phone rocks when you press one corner on a flat table
- A gap has opened between the screen and the frame, usually at one edge first
- The back panel is bowed, or the camera glass sits at an angle it did not
- On a laptop, the trackpad has stopped clicking properly or sits proud
- The screen has lifted with no drop and no impact to explain it
- The case no longer fits the way it did
What is actually happening inside
A lithium polymer cell is a stack of layers in a soft foil pouch. As the chemistry degrades, or after physical damage, or after long periods hot, the electrolyte breaks down and produces gas. The pouch has nowhere to vent, so it inflates.
Because the cell sits in a sealed metal frame with the display glued over it, the only direction the pressure can go is out through the screen or the back. That is why the first sign is almost always the display lifting rather than anything you would recognise as a battery problem.
The gas is flammable and the cell is under mechanical stress. Puncturing a swollen pouch, which is very easy to do while levering a phone open, can cause it to vent violently or ignite. That is not a theoretical risk and it is the entire reason this page exists.
What to do, in order
- Stop charging itImmediately, and do not put it back on. Charging a swelling cell adds heat and energy to something already failing.
- Power it offIf it will switch off, switch it off and leave it off.
- Do not press on itNot to test how bad it is, not to close the gap, not to see if it clicks back. Pressure on a swollen pouch is the thing to avoid.
- Do not try to open itLevering a phone with a swollen cell inside is how a pouch gets punctured. This one is worth leaving to somebody with the tools.
- Keep it somewhere safe and coolNot in a pocket, not in a bed, not in a car in the sun. A hard surface away from anything flammable until it can be dealt with.
- Bring it inWe will make it safe, and we will tell you honestly whether the screen it pushed out needs replacing too.
Why the screen matters here
A new screen fitted over a swelling battery breaks. The cell keeps expanding, it presses on the back of the new panel, and within weeks you have paid for a screen and have the same problem plus a lifted new display.
So on a phone with both symptoms the battery is the repair and the screen is the question. Sometimes the display survived being pushed out and goes back down perfectly once the cell is gone. Sometimes it did not, and we will show you which rather than assuming.
This is also why a phone whose glass lifted with no impact should have the battery checked before anybody quotes a screen. It is a cheaper diagnosis and it saves people from paying twice.
Laptops, tablets and controllers
The same chemistry and the same rules. On a laptop the giveaway is a trackpad that has stopped clicking or a lid that no longer closes flush, because the cell sits directly under the trackpad on most designs.
On a tablet the screen lifts at a corner, usually near the volume buttons. On a games controller the shell splits along the seam.
Older devices left in drawers for years are the most common source. A cell stored at full charge, warm, for a long time is exactly the recipe, which is why a laptop pulled out of a cupboard after three years sometimes cannot be closed.
Common questions.
Treat it as yes. The gas inside is flammable and the pouch is under stress, so puncturing it, which is easy when levering a phone open, can make it vent or ignite. Stop charging it, stop pressing on it, and bring it in.
Not safely, and every hour of use adds heat. Get the data off it if you can do that quickly, then power it off and leave it off until it can be dealt with.
Age and heat, usually together. A cell degrades chemically over years, and heat accelerates it. Physical damage from a drop, and long storage at full charge, both do it too.
Sometimes. A display pushed out by a swelling cell often goes back down perfectly once the battery is gone, and sometimes it does not. We check rather than assume, and we will not fit a new screen over a battery we have not replaced.
No. A damaged lithium cell in general waste is a genuine fire risk in the bin lorry, and it is illegal here anyway. Bring it in and we will dispose of it properly, whether or not you have the repair done with us.
Where this leads.
Next in batteries and charging.
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