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Comment by newaccount74 | Hacker News Reader

I think they want to leave some space so that the battery can expand. Easiest way to do that is to glue it on one side and leave a bit of space on the other side.

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I love how they learned from their mistakes of the old macbook pro. Batteries need ability to expand ever so slightly. Same reason why cranes are able to move freely with the wind when not in use.

Huh. I had no idea cranes are allowed to freely rotate with the wind. Makes sense, just one of those things I'd never thought about.

Neat!

Why not add a valve? Every cylindrical cell has one, but manufacturers seem to be allergic to adding one on lipo packs. Apparently having them swell to 5x the size and break the device casing is preferable.

Pretty sure the airtight casing is here on purpose to trap flammables gas a dying cell create. Without it it would be very unsafe to use this type of batteries.

A container that traps flammable gasses is called a bomb

This is not usually a design goal

No, a container that contains flammable gasses and then destructively allows them to escape is a bomb, one that just inflates is arguably the equivalent of a self inflating pillow.

Gasses create pressure A phone casing is not a pressure vessel This isn’t going to work

I guess using cylindrical cells in power tools, laptops, electric bikes and cars, power banks, flashlights, etc. must be super unsafe then, since they all have valves that release gas instead of inflating.

Lipo battery gas contains flammable and poisonous chemicals - including Hydrogen fluoride. Swelling slightly in normal use and occasionally rupturing is safer over-all than off gassing all the time.

From wiki:

> Hydrogen fluoride is an extremely dangerous gas, forming corrosive and penetrating hydrofluoric acid upon contact with moisture. The gas can also cause blindness by rapid destruction of the corneas.

https://en.wikipedia.org/wiki/Hydrogen_fluoride

Okay I’m really going to prioritize throwing away my old android devices now.

Throwing away is a real hassle. You often buy a new phone because the old one is broken. So data is on there but you cant turn it on. Get a drill out? Not sure I want to breath in that dust.

Microwave? Might be easier to avoid the fumes than the dust from drilling. Probably easier to drill outside and wear an N95 mask and goggles though.

Just put a soldering iron over the epoxy on the ssd chips, get it really hot to ensure the sillicon gets heated to at least 100C and your data will be gone forever in a completely non-functional chip.

Buy an iPhone and don’t worry about recycling it because storage encryption means it doesn’t matter. You can never plan for when you might lose a device.

No! Take those devices to electronics recycling. They DO NOT go into your municipal trash. Lithium-ion batteries can start fires inside your garbage truck, forcing the truck to dump its flaming contents onto the street. Electronics contain hazardous materials. And electronics contain valuable materials worth recycling. Where I live, it is illegal to put electronics in your municipal trash.

Most laptops use cylindrical cells for their battery pack, each one with a valve. I really doubt this is any kind of actual problem, more like an excuse given to reduce costs at the expense of the consumer.

Standard lead acid batteries in every car and UPS also release H2S in vast quantities when old and charged, and nobody seems to care.

> accasionally rupturing

You know this is most likely results in a fire right? There is no case where even a slight chance of it happening is safer.

Can you name any current laptop model that uses cylindrical cells? I haven't encountered any cylindrical cells when opening a laptop in well over a decade.

My old G771 definitely has them, though that one is like 8 years old or so now? The Gigabyte A5 looks like it might have one, but it's hard to tell without tearing the battery apart. I'm sure lots of gamer laptops still run on 18650s.

But yeah they mostly do lipos these days for thinness and weight reduction despite the obvious drawbacks. I wouldn't really ever buy a laptop with a lipo myself, shit's just gonna inflate and split it in half.

It's not just laptops anyway, EVs, power tools, flashlights, power banks, li-ion drop in replacement car/ups batteries. Anything that has a lipo has at some point had a cylindrical model too.

I'm not questioning whether cylindrical cells used to be popular for laptops; they were an iconic part of old ThinkPads. But I've opened up plenty of chunky gaming laptops in recent years from Asus, Dell/Alienware, MSI, Razer and have seen nothing but LiPo batteries. I think cylindrical cells may have genuinely disappeared from the laptop market at this point, unless they're still around in some niche that's significantly more obscure than big heavy gaming laptops. Most laptops these days that opt for a thick enclosure are doing it for the sake of the cooling system, not for the sake of fitting in a thick battery.

Edit: I looked at the Gigabyte A5 and agree that it's probably using cylindrical cells. It appears to be a Clevo system, so there were probably other brands reselling as well. But it's not quite a current model (3 year old processor), and the reviews seem to agree that the battery is one of the worst things about the machine, because the capacity is way too small for that class of machine.

A valve is a one time only device to prevent an explosion in the event of thermal runaway. It’s not going to accommodate the slight expansion and contraction which are a normal part of the charge cycle for lithium batteries. If the battery is kept under mechanical pressure in order to avoid movement (without the use of an adhesive) then there is no place for the battery to expand to. That sounds like a recipe for disaster.

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