You pull your smartphone out of your pocket and notice — uh oh — it seems puffed up. Or maybe you go to use your laptop and realize that the bottom doesn’t sit flush on the table anymore.
Chances are, you’re dealing with a swollen lithium battery.
While swelling batteries might seem like a minor nuisance, they can be quite dangerous. Lithium battery can catch fire and explode if charging continues after swelling has started.
So in this post, as a professional lithium battery packs manufacturer, I’ll cover everything you need to know about swollen phone and laptop batteries, including:
- What causes lithium batteries to swell up
- How to prevent battery swelling
- What to do when your battery expands
I’ll even explain what happens if you accidentally puncture a bloated battery.
What Is a Swollen Lithium Battery?
Swollen batteries, sometimes called “pillowing” or “puffing” batteries, have had some sort of internal failure that’s caused them to physically expand.
You’ll notice the swelling visually as a bulge in your device. Or the case around a replaceable battery may appear distended.
Laptops, phones, Bluetooth headphones… virtually any gadget with a lithium-ion battery inside can fall victim to swelling.
And these days, that’s most rechargeables. Lithium-ion has become the dominant battery chemistry for consumer electronics due to its high energy density, low self-discharge rate, and lack of memory effect.
But li-ion isn’t indestructible — keep reading to discover what exactly causes that unsightly bloated battery.
Why Lithium Battery Swell Up: 4 Root Causes
While battery failure can occur from manufacturing defects, much of the time swelling happens because of the way you use and charge your device.
Here are the four most common reasons lithium batteries expand over time:
1. Overcharging
Giving your phone, laptop, or Bluetooth headphones an electric shock by overcharging is asking for battery bloating.
And by overcharging, I mean keeping your device plugged in and charging even when the battery meter says it’s at 100%.
Li-ion batteries don’t like being held at their maximum charge for long periods. Doing so strains the anode and cathode, causing physical changes that manifest as swelling.
The lithium-cobalt chemistry used in many phone batteries seems particularly vulnerable.
However, overcharging alone may not cause battery puffing — it’s often the overcharging plus exposure to heat that speeds up deterioration.
Which brings us to root cause #2…
2. Heat Exposure
Lithium-ion batteries should not be exposed to temperatures exceeding 130°F or so.
The electrolyte fluid inside starts to break down at higher temps, producing gas that exerts outward pressure on the battery casing.
Where might your phone or laptop encounter temperatures that high?
A few examples:
- Left charging in a hot car in summer
- Used while baking under the sun
- Placed against a heating vent or other hot surface
Even normal environmental conditions can get hot enough to damage batteries over time, which is why manufacturers specify relatively tight operating ranges.
Using an inadequately designed case that traps heat can also cause portable lithium-ion batteries to swell.
And oddly enough, while extreme cold won’t make these batteries expand, it will severely reduce capacity and lifespan. So don’t toss them in the freezer either!
3. Physical Damage
Lithium-ion cells don’t handle physical abuse very well thanks to their layered construction and volatile chemistry.
Just one bad puncture can make the things go haywire.
Common causes of physical battery damage include:
- Dropping your device repeatedly
- Closing laptops with objects left over the keyboard
- Poor quality batteries with thin casing
- Improper battery installation (phones)
While impact shocks pose the most obvious threat, less noticeable scratches and dents can also create internal short circuits and hot spots.
4. Age-Related Breakdown
Even with responsible use, rechargeable li-ion batteries lose capacity over time as the cathode, anode, and separator degrade.
Hundreds of charge cycles spread out over a few years can trigger swelling by producing gases the battery wasn’t designed to contain long-term.
Age-related swelling won’t necessary happen suddenly — you’re more likely to notice gradual thickening before serious bloating.
At around ~80% of original full capacity, it’s a good idea to start shopping for a replacement to avoid being caught out with a puffy pack.
Signs Your Lithium Battery Is Swelling
Unless you routinely x-ray your electronics (please don’t!), the only way to detect a swelling battery is by looking for symptoms.
With smartphones and tablets, puffing will manifest visually as… weird bulging on the case.
The screen glass may also begin to lift away from the body due to pressure from behind.
Swollen battery inside phone
On laptops and hoverboards, you’ll notice the underside no longer sits flush. Attempting to use these devices on your actual lap will feel rather lumpy.
And if an external battery pack is the culprit, the casing will appear stretched or strained. Most cylindrical cells will also dome at the ends instead of lying perfectly flat.
Physical deformation is the most obvious swelling indicator. But there are also functional signs to watch out for:
Poor Battery Life
As the cell walls stretch thinner to accommodate gas pressure, the cathode and anode struggle to maintain optimal “squeeze” contact. The loss of pressure lowers current capability, translating to less runtime per charge.
Overheating
While heat contributes to swelling, runaway swelling also traps more heat. You may notice unexplained spikes in operating temperature before other symptoms appear.
Spotty Charging
Similar to the above, changes in internal dimensions hinder normal charge transfer. So your battery meter might bounce around instead of filling smoothly. Annoying!
Other Glitches
A swollen battery strains a phone’s or laptop’s internals. As it expands, pressure builds on the logic board, connectors and buttons, leading to erratic behavior right when you need your device most.
Power it off and do not attempt charging once you confirm your battery has started swelling. The next section explains why.
Dangers of a Puffed Lithium Battery
I hinted earlier that swollen li-ion packs are more than just an inconvenience. Let’s cover the exact risks:
1. Fire Hazard
Why do lithium batteries catch fire when other battery types rarely do? Two reasons.
One, the electrolyte fluid inside li-ion cells is actually flammable organic solvent… basically liquid fuel looking for an excuse to burn.
And two: by virtue of lithium’s natural reactivity, damaged cells can experience uncontrolled temperature increases. Reaching upwards of 700oF causes the electrolyte fluid to readily burst into flames.
It’s a nasty one-two combo!
As you can imagine, a swollen battery at risk of erupting into fire is about the worst thing you can leave lying around the house. Or have in your pocket.
2. Potential for Explosion
Extreme battery puffing weakens the outer casing to the point of rupture. Similar to an overfilled balloon, once stretching hits the cell walls’ physical limits, violent tearing occurs.
This triggers the usual fire show… except more suddenly, with plenty of flying debris to spread the heat.
Battery explosions are extremely rare, but swollen li-ion packs usually get that way from pushing limits already. Best remove before worst comes to worst.
3. Device Damage
Letting a swollen battery continue to expand puts neighboring components like displays and main boards at risk.
The amount of pressure inside the compartment builds quickly once minor swelling starts. Delicate electronics don’t mix well with force crushing them into other parts unexpectedly.
And should the battery eventually combust, of course your phone/laptop/hoverboard will probably call it quits. Melted plastic and fried silicon aren’t known for good functionality.
What To Do With a Swollen Lithium Battery
If you catch battery swelling in the early stages — excellent. But unlike kicking a bad habit, procrastination only makes the problem explode bigger.
Follow these steps when you notice first signs of expansion, or feel reasonably sure your battery is puffed:
Stop Using Immediately
Seriously. No checking Facebook just once more. Any further demand placed on an unstable battery can trigger cascading failure.
Power down and do not attempt to charge a swollen li-ion pack again. The risk of fire or rupture while gas pockets inside strain the casing is too great.
Disconnect Carefully
Batteries that are visibly bloated require EXTREME delicacy during handling. Forget the usual quick motions you make taking out a battery or charger cable.
Slow movements help avoid an accidental puncture, short circuit or static spark. All could result in dangerous overheating.
Practice battery extraction on a puffy phone? Better leave it to the repair pros…
If you must DIY, use plastic tools and avoid touching metal tabs or contacts.
Store Properly
Recently expanded, potentially damaged lithium batteries belong in a fireproof container if available. Or at least a spot away from other flammables.
Stick to non-conductive surfaces too, meaning no bare metal and definitely not on piles of spare change or other batteries! A lipo safety bag makes smart storage if you have some for RC models.
And make sure children or pets can’t access the area either. Last thing you need is an accidental choking or chemical ingestion…
Dispose Responsibly
Sad as it sounds, once swell has set in most lithium cells don’t recover well. Performance and safety drop too low for reuse even IF you manage to stop bloating from progressing somehow.
Instead, Google battery recycling centers near you. Call ahead to find facilities that accept puffy li-ion batteries from consumer electronics.
Many municipalities and retailers like Best Buy also collect batteries for proper recycling.
Absolutely never toss swollen cells in normal curbside trash (or even “e-waste”) bins — I cannot stress that enough! If a compacting truck doesn’t set them on fire first, toxic battery innards will make landfill groundwater rather unfriendly.
Puncturing Swollen Lithium Battery (WARNING: DO NOT!)
Given how spectacularly volatile lithium is as an active metal, you’d think folks would show more restraint before grabbing sharp objects around swollen cells.
Yet YouTube remains full of (questionable) DIYers gleefully exploiting puffy laptop and phone batteries for the viewing pleasure of our pyromania-loving species.
Please admire the pretty fireballs from a safe distance instead of punching holes into your swollen batteries, folks… that’s why God — err, I mean — creative video editors invented slow motion.
Stay safe and charge smart out there!
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