No matter how fast powerful laptops get, and no matter how ridiculously big and beefy a portable gaming rig might be, their batteries will never be any bigger than they are today. Why? You can thank the Federal Aviation Administration.
Lithium-ion batteries are a wonder of convenience. They can power computers for days, they charge quickly, and they don’t suffer from any weird “memory” effects, and lithium is the lightest of metals, which is good for portable devices. But they can also be dangerous when things go wrong.
A swollen or punctured battery can catch fire or explode, and you cannot simply douse it with water or throw a wet towel over the top. Last year, a Tesla’s batteries caught fire on a California freeway, and firefighters had to dump 6,000 gallons of water on it to quench the flames. Tesla itself estimates 3,000-8,000 gallons, and the number can go as high as 40,000 gallons, just for the batteries in a car. Now, imagine something similar happening on a plane, and you can see why airlines are wary of anything containing a big li-ion battery.
This is why planes have a hard limit—100 Watt hours—on rechargeable li-ion battery capacity, and a maximum of 2 grams of lithium in non-rechargeable batteries. Current FAA regulations allow an individual to carry “up to two spare larger lithium ion batteries (101–160Wh) or Lithium metal batteries (2-8 grams).” The FAA’s european equivalent, the EASA, also enforces a 100Wh maximum, with up to 160 Wh allowed with the permission of the airline. Devices can be packed in checked luggage “as long as you take measures to prevent unintentional activation,” says the EASA, but spare batteries and power banks must be carried in the cabin.
And that explains why even the biggest laptops don’t go above 100Wh for their built-in batteries. If they did, you couldn’t fly with them. That’s fine for smaller laptops. The latest 14-inch M4 MacBook Pro packs a 72.4Wh lithium-polymer battery, for example. But the 16-inch version is right up at that 100Wh limit.
Why Do They Burn So Long?
If you’ve ever seen a lithium battery fire, you’ll know that you never, ever want to see one on a plane. They burn hard and hot, and are very difficult to put out. Tesla recommends just letting the fire burn itself out then cool down, which can take up to 24 hours. The FAA’s statistics say that there have been 31 LI battery incidents this year so far, compared to 51 for last year.
These batteries are hazardous because they contain everything needed for a good, healthy blaze. The electrolyte is composed of flammable materials, one electrode contains a good bit of oxygen, and there’s plenty of stored energy.
When the battery is damaged, perhaps by piercing or crushing, or by improper charging, this energy is released in the form of heat. This can further break down the battery, releasing yet more heat in a chain reaction called thermal runaway. At the same time, the heat can vaporize the electrolyte, which can then catch fire. If there is free lithium in the battery, then it can react with water to produce hydrogen, which obviously doesn’t help matters.
This internal energy source is what keeps the fire burning. Even if you extinguish the flames, the heat from the thermal run away can ignite them again.
This is why we are so hot on battery safety here at iFixit. Swapping out a dying phone battery is a common repair, so you have to play by the rules. It might seem tempting to forgo the proper disassembly required to get to the battery, and to just lever it out instead, but that can end up triggering an explosive situation. Likewise, you should never use metal implements that could pierce the battery.
That said, as long as you’ve discharged your battery in full, it’s very unlikely to catch fire.
What To Do If Your Battery Starts To Swell, Smoke or Catch Fire
Staying safe depends on how you use batteries. If all you’re doing is swapping out a battery in your phone or laptop, just follow the instructions and take care not to damage the battery in any way. It’s also essential to discharge the battery before changing it, to reduce the amount of energy available if things do go wrong. The iPhone 16 has its battery encased in a steel skin to help with safety.
But it’s not always so straightforward. For example, remote control (RC) car and drone racers risk damage every time they crash. And while a laptop will have good charge-management, overcharging can be as hazardous as sticking a screwdriver into the battery. Take a look at this RC car, whose battery was intentionally overcharged.
If you’re working in an environment where battery fires are more likely—maybe you run a repair shop, or you’re an RC racer, or you operate a passenger airline—then extra precautions are necessary. The FAA’s training video for in-cabin battery fires on planes is also worth a watch for anyone using LI batteries in risky situations.
The easiest way to deal with a single battery fire is to throw it (very carefully) into a containment device. This is typically a bag or a box that can withstand very high temperatures, while remaining cool on the outside. It may also come with heat resistant gloves for getting the flaming device into the bag, and water for dousing to mitigate thermal runaway. But you can also make your own—as we do at iFixit—by pouring some sand into a metal bucket. Then, if a battery ignites, you can put it into the metal bucket and carry it outside until the fire burns itself out.
Shipping Batteries
We’ve seen that li-ion batteries are dangerous if damaged, and why the FAA doesn’t want you stuffing spares into your checked baggage, down in the hold where any fires cannot be spotted, and cannot be fought by the crew. It doesn’t help that hold luggage gets tossed around and abused, unlike your cabin baggage, which you probably won’t attempt to throw down a 20-foot ramp or crush under bigger, heavier cases.
This all explains the rules around shipping batteries. You’ve probably noticed the warning labels on the packaging of any battery-powered gadget you’ve bought in recent memory. These devices can be transported by air, whereas naked batteries, like the spares we sell at iFixit, can only be shipped by surface transport.
Here’s what the US DoT has to say in its Lithium Battery Guide For Shippers: “Unlike standard alkaline batteries, most lithium batteries manufactured today contain a flammable electrolyte and have an incredibly high energy density. They can overheat and ignite under certain conditions, such as a short circuit or improper design or assembly. Once ignited, lithium cell and battery fires can be difficult to extinguish.”
Batteries inside laptops, speakers, and so on are encased, which means that they are much harder to damage. In addition, that “casing,” and the packaging surrounding it, make it harder for thermal runaway to propagate to other batteries or conductive materials. Imagine a cargo plane’s hold stacked with boxes of bare laptop batteries and you can see how wrong things could go.
Lithium-based batteries are incredible, allowing us to use our phones, laptops, and other devices for hours, days, or even weeks away from a power outlet. But as we have seen, they also have downsides. In most cases, these downsides are worth the risk, and in general use, most of us will never have to deal with a raging li-ion battery fire. And knowing these risks — as you now do — reduces them substantially. It might be frustrating for some that laptops cannot pack even more battery power, but on the other hand, now we know the dangers, it’s actually pretty comforting to know that the video editor sitting next to you on the plane doesn’t have a 300 Wh time bomb on their lap, ready to fuel a flight-ending blaze.
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