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Ask HN: How do you store devices with Lithium-Ion batteries for long-term?

76 points by fouc ↗ HN
I'm curious about how everyone stores old smartphones and other lithium-ion battery-dependent devices while preserving battery life. Especially when they might want the device to keep working over several years.

I've tried charging my backup devices to 50% and storing them in a cool, dry place, but I often forget to do so, resulting in a drained battery by the time I recharge them. I am worried this might be affecting the battery's longevity.

Does anyone have a better method, such as an automated charging system, for managing this?

47 comments

[ 2.6 ms ] story [ 354 ms ] thread
simcop2387
No idea about anything automated for it but my understanding is that you really can't prevent the problems. I think I read that 70% is more ideal thoguh, because it will keep a charge longer in the better range for the chemistry. The real problem is that the chemistry itaelf of the batteries will slowly and irreversibly break down over time whixh is why once it discharges past a certain point it may not be safe ever again to charge the battery without reprocessing the materials into a new battery. The safest way is really to remove the battery entirely and replace it once you're wanting to use it again. This might also make it easier to keep the battery at a safe charge level if you can find something else to handle it.
jrockway
I don't think you want an automated charging system. Maybe make a calendar invite for yourself on the first Saturday of every month to check them. Probably takes at most 10 minutes of your weekend.
crazygringo
Yup, calendar events are the way to go. I recharge certain backup electronics every six months. I've probably got 20 different home/life calendar maintenance tasks like that, recurring somewhere between every 3 months and every 2 years.
ruined
in a dedicated concrete structure at least fifty feet from neighboring structures
mgarfias
A friend of mine just lost her house to a lipo in an rc car that decided to combust
liminalsunset
The types of batteries used in this type of equipment tend to be less robust and more prone to this type of problem than other common equipment with lithium cells in them.

Cells/packs used in these hobby applications typically lack an outer protective shell, and are of the pouch cell type. This makes them more susceptible to damage, but is done for primarily weight considerations likely. Typical notebook or phone batteries will be encased in some form of structure that protects them, and for smaller batteries, like in phones, can prevent the fire from exiting the enclosure to some extent.

Furthermore, these cells/packs are designed for shockingly high instantaneous discharge rates, which means that any accidental release in energy will be correspondingly fast and violent. It seems that protection of the battery is the charger/device's responsibility, so it's also easy to accidentally use batteries which have been overtemped/overdischarged/underdischarged/overcharged. (they also have much lower design cycle counts than typical electronics batteries). Typical electronics batteries have a chip in them that will disconnect the battery, sometimes permanently, should any of these conditions occur at some point in the battery's lifespan.

I would personally recommend against the storage or charging of such batteries indoors without measures to contain any potential fire. For what it's worth, discharging (and maintaining) the batteries at a low state of charge will also decrease the amount of energy available for combustion.

exmadscientist
Our experience strongly agrees with you that unprotected, high-discharge-rate, pouch cells are the most dangerous things around. Remove any of those three factors and I'm comfortable leaving them outside of our Bat-Safe. But the scary RC batteries get to live in there permanently.
andersa
Wow, that's scary. Did this happen while it was charging, or completely at random?
rawbert
I just started RC cars with my kids and made first contact with LiPos and find it quite scary. A lipo counts already as damaged when the voltage drops below 3V so you have to use equipment permanently checking the voltage. In RC cars you mostly use some kind of buzzer that fires when a certain threshold value was reached. A "damaged" LiPo might catch fire randomly.

Also you have to store them in fire-proof LiPo bags and recharge them regularly to prevent voltage drops below 3V.

RecycledEle
I hear these rumors about lithium batteries, and I see videos online.

My experience is different.

My students absolutely abuse the cheapest lithium cells I can find - from eBay and salvaged from dead laptops.

They did some art on pieces of metal through EDM using dozens of 18650 cells. No problems.

They tested what would really happen to old devices subjected to a massive USB over-voltage by building the "Over-Volter 9000." No problems for the lithium cells.

They ran lithium cells in dead shorts, just to see what would happen. Maybe a touch of smoke.

The only 2 times I have ever seen lithium batteries melt down was:

(1) when I pulled an early lithium pack from a Sharp 486 laptop and ran my RC car off it. (Associated TQ-10) That melt down resembled a bubbling mud pit at Yellowstone National Park. That was the first lithium battery I had ever seen, and it was useless when the laptop died and early death.

(2) Another time I melted an 18650 cell by accidentally leaving it in a dead short as I wired a large battery pack.

In both cases, the combustion was mostly smoke and sparks, with little to no visible flame.

fsmv
18650 cells are lithium ion not lithium polymer
RetroTechie
Sorry to hear that.. Can you please provide whatever info you have concerning the exact conditions this happened in?

There's maaany stories & videos about Li-ions bursting into flames, but with very few exceptions they come down to:

* While being charged. Or even under extreme stress, like driving a nail through it, or hooking up to a car battery to watch it explode.

* In series configuration, with 1 of the cells being defective / much lower capacity than the others. Or using a mix of different cells / cells in different state of charge.

* Cheap / poor quality / fake cells.

* Physical damage.

* Connected to monitoring / protection circuitry, with that circuitry failing. Not to mention ridiculously cheap chargers that are basically constant voltage source without any kind of safety feature.

* Some history of abuse (under / overcharging , dropping from a height etc).

Loose, quality Li-ions just sitting on a shelf, bursting spontaneously into flames, is very very rare.

rawbert
Yes, but Li-Ion is not the topic here. RC-cars usually use LiPo / Lithium-Polymer batteries which are quite more "dangerous".
SoftTalker
If you're using the device that infrequently, recycle it and stop worrying about it.
binarymax
It’s a great question for power tools. I don’t use my circular saw very often, but I do use it every month or two.
ocdtrekkie
This is where the "system" approach for cordless power tools really pays dividends. I have several tools that I use with varying degrees of frequency, but only two batteries to worry about. I also know the power tools will likely last decades, but the batteries should be discarded every few years.
crazygringo
That is not a helpful comment.

People have equipment that they only use on a type of vacation they take every 18 months, for example, and which is more cost-effective to own than rent (or it's not available for rental). They have equipment for emergencies. And so forth.

Comments that try to invalidate the entire premise of somebody's problem just aren't useful, and can actually come across as pretty rude.

smartbit
In a freezer I’ve been storing detachable batteries of a laptop that was mainly used at a desktop. They came out fine after some five years, didn’t do tests before and after though.
liminalsunset
It might be helpful to store them in the fridge as opposed to the freezer in some cases. Last time I checked, the highest inflection point in lithium ion degradation with storage seems to be at temperatures at or above 30 C or so [1], so the 5 C typical environment in a fridge would appear to give sufficient margin.

One problem with storing them really cold is that should the device drain the battery, a cold battery can more easily fall under the "minimum cell voltage" threshold due to the changed voltage curve, which can cause laptop batteries to totally fail permanently due to the monitoring chip inside.

Lithium batteries don't like being charged under 0 degrees Celsius (let them warm up first!), and attempting to do so can lead to the lithium being unable to intercalate into the electrode, causing plating of lithium. The batteries should probably be wrapped in a sealed plastic bag with dessicant in it, to prevent condensation from getting to the internal protection electronics. The device should be allowed to warm up before being removed from the bag to prevent condensation.

[1] https://www.nature.com/articles/srep12967

makeitdouble
I was going to ask if it was even safe to keep those batteries in device long term, but the answer is already out: https://news.ycombinator.com/item?id=37684415

Those warning stickers asking you to remove the batteries when the device won't be used for a long time were not just decorative.

Fire-Dragon-DoL
Isn't it impossible to do on various smartphones?
saurik
It was a while ago that I watched this video--and I don't want to watch it again right now--but I think this issue was more of a defect in the manufacturing of these batteries; but, since it didn't seem to matter until the phones were being stored for long periods of time--this person maintains a giant collection for some kind of testing purpose--it seems relevant here as these weren't uncommon phones or anything.

https://youtu.be/OfM0GqsIB6c

makeitdouble
Anecdotally I've had batteries expanded in two Apple devices (disclaimer: I don't keep many other devices around).

The video makes a case for Samsung devices being prone to it in near ideal conditions, but normal people tend to take a lot less care, use them in rougher environments as well and stressing things a lot more, especially as these devices are not used 3 weeks for testing and stored away as reviewers would do.

I think we should expect most of our devices to potentially have the issue at some point, whatever the maker. Even on the safer devices, there must be a point where it just happens.

makeitdouble
Overwhelmingly Yes, and perhaps no.

Yes it's crazy hard to do it non-destructively for many smartphones as a normal user. The same way it's just hell to replace the batteries sometimes (still remember the 52 steps process for the previous gen iPad pros).

No in that normal users should also not store a trove of past smartphones (or any electronic device) if they can't remove the battery, so the only people that should have this problem are iFixit grade tinkerers, for whom 50+ steps of disassembly should be fine.

That could be another angle on "why should I care about battery accessibility in my phone" ?

1letterunixname
NMC chemistries: 70-80% charge, minimal humidity (corrosion of electronics is always a concern), very cold, and in a fire-proof container.

Pb chemistries (automotive, boat, etc.): trickle charge with periodic desulphation.

zingerlio
Whenever I go on vacation for more than 2 weeks, I have this irrational fear that one of those neglected devices in a drawer somewhere would become a spicy pillow and self combust and burn my house down. Sometimes I keep them in those thin metal cookie boxes with a lid, so it could have some level of isolation. Never validated though.
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mirekrusin
Drain them before for peace of mind.

Which makes you think, maybe all electronics above certain capacity should have controlled drain option?

dzek69
I do nothing and surprisingly nothing is broken. I.e. I found 6 years not used Xperia phone, I charged it and it just works, without any visible battery degradation issues. I have few other battery powered devices and none is giving me any issues after years of storage.

Last time I've seen swollen battery was in the Nokia dumbphones era.

So while it might not be the best idea - I will keep doing nothing special.

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mid-kid
I just make sure to never store them fully charged, or fully discharged. Some neutral state of charge tends to work fine.
olalonde
Modern smartphones have sophisticated battery management systems that could theoretically be programmed to optimize for this scenario but unfortunately those systems tend to be off limits to third party developers.
exmadscientist
These systems are, alas, not usually programmed very well at all. I have heard some stories (and they are credible -- I'm typing on one of the products concerned!), but they're not the sort of thing I can repeat publicly without burning a few bridges.

Suffice it to say you should assume your device's BMS is programmed to optimize charging speed (and maybe fresh-out-of-the-box capacity, not that the BMS can affect that much) and absolutely nothing else.

That said, around here we charge stuff to about one-third of its capacity and leave it sitting around for years on end, and that seems to work out OK. There's only been one incident so far, and that was during active work with a soldering iron on an unprotected battery contact. (Which is, yes, insanely risky with a 30C-rated discharge cell!)

layer8
There are inexpensive timers you can plug into an outlet and attach one or more devices to (power-strip style). Just choose some cycle (half an hour once per week, for example) and attach all your devices you want to keep the batteries from draining to zero.

I don’t know the best timing approach to maximize battery longevity, but draining to zero for a longer time can definitely kill a battery.

eimrine
If you are going to need that device in not nearest future (1 year+), probably you should buy an original spare battery. There are maybe a million of Lithium battery designs on the Earth, do not expect you can easily buy a battery to your device. Especially if this is a Blackberry/GoPro/proprietary device with a sophisticated battery connection which refuses to just use 4.2V from any source.
yjftsjthsd-h
So you should replace the battery, but also getting a replacement battery is impossible?
eimrine
I don't understand your question. I mean that if you going to use the device in future you might need the battery. And a supply of replacement batteries may just stop. Especially I mean original replacement batteries. For example, the legendary BL-4C is available in my country only as non-original version having half of capacity or less.
acyou
Fireplaces or outside away from flammable objects are great places to charge lithium ion betteries. You're also best off supervising charging in person, watching for melting plastic, smoke, bulging/swelling.
avidiax
Store at about 50-70% charge, in a metal box, in the refrigerator.

That will allow the cells to last the maximum amount of time.

You might need to periodically recharge them, but this could be months at least for electronics that can be turned off.

If the device doesn't have a charge meter, draining it and then charging for 30 minutes will often work, since many devices are designed to charge at 1C, i.e. 0->100% in one hour.

Saris
Store at 30-50%. I can't say I've ever had a device turn out completely discharged, but I imagine some do not properly shut off entirely.
fouc
from Apple[1] the advice is:

  * Do not fully charge or fully discharge your device’s battery — charge it to around 50%. 
  * Power down the device to avoid additional battery use.
  * Place your device in a cool, moisture-free environment that’s less than 90° F (32° C).
  * If you plan to store your device for longer than six months, charge it to 50% every six months.
So it seems to me that I should just use a calendar reminder after all.

[0] https://www.apple.com/batteries/maximizing-performance/