Battery overcharing

[PlainName]

We all know by now that charging a Li-xxx battery to full every time, and especially keeping it on charge, is not good for it. My new phone says not to leave it on charge, and especially it could have Bad Things happen if it's on charge for 12 hours or more. That's kind of problematic why the best time to charge the thing is overnight and you're not going to be awake to unplug it when it's full.

So why don't they just turn off the charging circuit on a full battery? They know when it is full, or nearly full, and surely it's simple enough to just flip off a MOSFET or something in that circumstance. But, no, it takes a fully working external human being to achieve that.

What have I missed? I looked for USB cables, or chargers, that could detect a reduced current and just turn off at that point, but there are very few. Amazingly few, actually. With USB PD didn't anyone think to enable the phone to say "Full now, thank, check back in a bit"?

Also kind of surprised there is no phone app that can monitor charge state and, when it thinks it's gone on enough, trigger an IoT socket to turn off the charger.

Seems to me either overcharging isn't actually a problem or fixing it is so complicated no-one tries.

[Andy Chee]

My old iPhone 7 (released in 2016 and still going strong) definitely has charge management i.e. it can disconnect the charger.  So I'm surprised your new phone lacks that capability.

[PlainName]

Me too! But it seems to be common and not just this phone - I mention this one simply because it's the thing that bugs me at the moment

[elektryk]

On rooted Android device you can set charging limit for eg. 80% with app. Also my old Latitude notebook has such option in manufacturer's software to extend battery lifetime while it is mainly used on AC.

[themadhippy]

What have I missed?

The profit from selling you a new battery/phone because the old one no longer holds a charge

[Siwastaja]

What have I missed?

Probably two three things:
1) Leaving the charging circuit "connected" i.e. floating the battery is not significantly worse than disconnecting it. Sources that claim this are wrong. There is a lot of wrong information out there. Especially if you try to deduct technical details out of manuals written for ordinary people, you are prone to making wrong conclusions. Consumer manuals are usually shit. For example, many Ni-Cd/Ni-MH era instructions (like "you have to charge the phone overnight before first turning it on") stayed in manuals for over a decade after li-ion became a thing.

2) Microcycling (stop charging - voltage drops because of use - start charging again - stop charging...) the cell near full charge probably isn't any better, and is likely worse than just floating it.

3) Many charging circuits stop charging anyway, you just don't know it's happening, so your assumption of them not doing this is likely wrong.

Note that the 5V wall plug is not the charger. It's a power supply which supplies power for the charger, which is inside the phone/whatever device.


+ holding the cell at full charge voltage is not "overcharging". Overcharging is going beyond the full charge voltage. (If we are pedantic, then the equivalent holding voltage would be a tiny bit less than stopping voltage, but the difference is small, e.g. 4.15V instead of 4.20V; in such pedantic analysis, then holding at 4.20V is technically overcharging, but still within the tolerances of the battery specification, so maybe not "overcharging" after all.)

[Buriedcode]

AFAIAW all phones will manage charging, including sometimes preventing charge to "full" based on age and battery health.  Even my old cheap Huawei with generic/vanilla Android does this.  There is no need for any kind of technical solution on the part of the consumer - I'm sure there are "special charging cables" that can claim to maintain battery health, but that would be marketing wank.

Also, as noted, there is a lot of vague (and wrong) information regarding battery life, care, charging technology that is often perpetuated by those with poor understanding ("tech journalists") and cheeky marketing tricks - like claming faster charging times simply by not charging to full capacity, or making odd comparisons to old NiCd tech.

I suspect your new phone has that warning - not because there is a real need for human intervention to prevent abttery damage, more as a safety precaution since phone manufactureres really dont' know if you're going to leave your phone on charge, plugged into a really dodgy USB supply, next to a radiator.  Even then its internal sensors will stop the charging, but charging creates heat which may or may not reduce the phones life in situations where there are other sources of heat.  I think its more a safety message to cover themselves.

Note the old idea that you should let your phone run down to 0% then charge it fully when you first use it is to train the battery supervisors culomb counter for accurate battery level estimates - not for actual battery health.  I'm not sure thats really needed these days.

Edit: typo.

[BrokenYugo]

Sounds like the generic copypasta warnings you find in cheap device manuals to me, pay it no mind.

What you shouldn't charge more than 12 hours are NiCd batteries on really basic dumb chargers with no cutoff feature that just dump endless energy into the battery. Crappy cordless drills a decade plus ago.

[PlainName]

Thanks all for your comments, where y'all seem to be agreed that worries about battery wear are unfounded. However, I use an app called Accubattery which keeps track of charge and usage history to determine the battery health and likely time to running out. Of course, the first thing that springs to mind is that they have a vested interest, but they also publish the research which goes towards the app development.

For instance: Charging - research and methodology.

So I am not sure it is as clear cut as might be first thought. And, hence my question (which, thanks Siwastaja for clarifying, may be confusing!).

[SiliconWizard]

What is your new phone?
Of course any phone with a li-ion battery has a charging management IC that won't allow "overcharging", that's just not even possible. Even the 10-cent (or less) Li-ion charger IC does that.
What it looks like is some copy-pasting, not from any existing end-user device, for which it's not an issue, but from battery datasheets themselves, which makes no sense for the end user.

[PlainName]

For reference, I would think that big name manufacturers would know about the product they are shipping. Here's a sample:

Xiaomi (my emphasis)

Avoid full charges

Li-ion batteries work best when the charge span is between 20%-80%. Going from 80% to 100% actually causes it to age faster. Consider the last 20% as extra in case you are not free to put your phone into charge but do top it off by charging as long as you can. Li-ion batteries works best in the middles.

This is not to say you should never fully charge your device of course, because we do need it at times like for battery calibration or whatever reasons you may have however you should always keep in mind to avoid it. It goes without saying that charging over night is not a great idea unless you are controlling the charge flow like stopping it at a certain battery level.

Nothing Tech

6. Avoid excessive charging
If the mobile phone is fully charged, the charger will be maintained in a full power state. This may cause battery deformation and the leakage of the fluid. The performance of the battery will also be significantly reduced and damaged.
Do not exceed 12 hours continuous charging time. When the phone prompts are full, you should unplug the charger.

Samsung

Unplug the charger after the device has reached a 100% charge to avoid a swollen battery

OnePlus

You should not charge the battery for more than 12 hours. After the phone is fully charged, unplug the charger.

[PlainName]

What is your new phone?

It's a Nothing(1). Current phone is a Xiaomi A1. Been trying to find a suitable replacement for some time, but nothing (not the phone!) ticks all the boxes yet.

[Kim Christensen]

For reference, I would think that big name manufacturers would know about the product they are shipping. Here's a sample:

Interesting. I wonder how much of this is just them covering their asses in case something goes wrong and things catch on fire.
Like the OP said, it seems pretty stupid that a "smart" phone can't manage it's battery properly.

[PlainName]

My guess is that a simple battery charging chip is used, which basically allows charging at some maximum rate and reduces to a trickle, or keeping topped up, when they battery is up to some specified voltage. As such, it's 'safe' in that it's a controlled charge, but it's not controllable by the phone per se. It's hardwired.

Some devices - Apple, presumably - add the necessary stuff to allow the phone to affect the charging, perhaps the rate and certainly the termination. Obviously, that would cost more and not be as simple as just using a charge chip.

[Siwastaja]

If you want true, real lifetime increase, you:
* Keep the battery significantly less than fully charged. 95% or 90% does not cut it. Go for 60-70% and below.
* During charging, avoid the combination of high state-of-charge, high charging current and cold temperature. You can pick one pretty safely. Pick two, and lifetime decreases significantly. Pick three and it's a disaster. Products of course do manage these things automagically and prevent very bad conditions (e.g., limit charging current at cold temperature; slow down charging near full), but they are not too aggressive to limit your use. If you want to optimize the lifetime, it's good to know these relationships so that you can manage more strictly than the product firmware does.
* Avoid storage at high temperature and high state of charge.

[Siwastaja]

For reference, I would think that big name manufacturers would know about the product they are shipping.

This is almost always wrong assumption, go figure. Of course their engineers know the product very well, but the manual is almost never correct at all, they are full of totally made-up bullshit to the point of making us engineer-minded lose hope in humanity. There always are managers who think that giving correct information is "too complicated" for "regular people", and solve the problem by lying, similar to "santa claus exists and gives you presents". The result is something that benefits no one, but laws require to have manuals no one reads, so then you have lies.

Specialized laboratory equipment etc. is in much better situation because the engineers can write the manuals.

[Halcyon]

There is absolutely no issues with leaving a phone plugged in for extended periods. You won't over-charge the battery doing this. The charge controller will simply stop charging when it's complete.

[PlainName]

I just charged my phone until it said full, and then left it. It was constantly sinking 4W. Should it not have been taking 0W?

[Kim Christensen]

Should it not have been taking 0W?

No. The phone itself will be using power even though the battery is finished charging and not taking any current.

[Dacian]

A battery phone keep at 100% SOC will get damaged fairly fast.
In average on my last phone I was replacing the battery every 2 years because it was mostly plugged in as phone is used as a WiFi hotspot.
Recently I got a CAT S22 Flip and likely due to newer OS (Android 11 Go) there is now an option for the battery to be kept in the 50 to 70% SOC range while plugged in and this should improve drastically the battery life. So hopefully I will need to battery replacement for this phone at least for the next 5 years.

The other phone I have is BLU with older Android 9 and that is missing this future and on top of that it keeps the battery at 4.3V so not sure how much it will last (I think is about 6 months since I started to use it in same way always plugged in) so far it seems fine.
I will be able to see the battery bulge as all my phones have removable batteries. The old one was also  BLU I think android 4 and after the third battery died I decided to upgrade.

[PlainName]

Should it not have been taking 0W?

No. The phone itself will be using power even though the battery is finished charging and not taking any current.

Yes, I realise the phone will be taking power, but it is asleep and if that state takes 4Wh then the battery would last less than a day with the phone doing nothing.

[Kim Christensen]

Yes, I realise the phone will be taking power, but it is asleep and if that state takes 4Wh then the battery would last less than a day with the phone doing nothing.

It may not go fully to sleep while it is plugged in.

[nctnico]

There is absolutely no issues with leaving a phone plugged in for extended periods. You won't over-charge the battery doing this. The charge controller will simply stop charging when it's complete.

But still, it is better for battery life if the battery is not charged to 100% but to a significantly lower level. Also, many phone chargers, charge at the maximum current. Some phones even claim to fast charge to 100% in 10 minutes or so. This is something you don't need when your phone is charging overnight.

[Halcyon]

There is absolutely no issues with leaving a phone plugged in for extended periods. You won't over-charge the battery doing this. The charge controller will simply stop charging when it's complete.

But still, it is better for battery life if the battery is not charged to 100% but to a significantly lower level. Also, many phone chargers, charge at the maximum current. Some phones even claim to fast charge to 100% in 10 minutes or so. This is something you don't need when your phone is charging overnight.

Yes, absolutely. But I bet you 99% of people out there don't bother with things like SoC (or even know what it means in any kind of meaningful way). Hardware and software manufacturer's know this.

Phones have been designed to be charged to 100% for decades and left plugged in common scenarios (in a car, while sleeping, on the kitchen bench, in an office until it's ready to be used etc...). Modern phones and laptops also tend to adjust their charging based on your habits. For example, I mostly keep my phone docked when I'm working from home, so my Google phone knows to just charge it using low current. Likewise, my Macbook will only charge to 80% as I mostly use it docked as well.

I'm the kind of person who generally keeps their phone for 3-4 years before replacement, and I've never had a battery prematurely fail or suffer significant degradation.

What we're discussing here has already been thought of and solved (at least by the reputable manufacturers). Your mileage may vary if you're buying Huawei, Nokia, OPPO, Xiaomi, ZTE, or those in the budget categories.

[Siwastaja]

I just charged my phone until it said full, and then left it. It was constantly sinking 4W. Should it not have been taking 0W?

It should not take 0W, but whatever the phone itself is using. 4W sounds very high unless you are playing games with it, though; for a typical let's say 16Wh battery capacity you would fully drain the battery in 4 hours! 4W should feel like significant amount of heat. I see two possibilities:

1) You simply measured wrong. How did you measure?
2) The battery was not fully charged yet and that power was flowing into the battery.

[PlainName]

Measured with a charging cable with power display.
The battery may not have been completely charged but the phone said it was. Regardless of the actual battery state, if the phone is saying it is done in order for me to remove power, it comes to the same thing.

[PlainName]

so my Google phone knows to just charge it using low current.

My Nothing will kind of do that. If the alarm is set then it will use low power, when wireless charging, so it is full just at the time the alarm goes off. Which suggests it is capable of adjusting the charge rate, at least for wireless charging. But this phone also has the warning about not leaving it on charge.

Likewise, my Macbook will only charge to 80% as I mostly use it docked as well.

Which suggests that limiting the charge is beneficial enough that Apple have the gubbins to achieve that. I'm sure they wouldn't do so if it didn't matter!

[Andy Chee]

This article might be useful reading:

https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries

Lithium-ion suffers from stress when exposed to heat, so does keeping a cell at a high charge voltage. A battery dwelling above 30°C (86°F) is considered elevated temperature and for most Li-ion a voltage above 4.10V/cell is deemed as high voltage. Exposing the battery to high temperature and dwelling in a full state-of-charge for an extended time can be more stressful than cycling.

Most Li-ions charge to 4.20V/cell, and every reduction in peak charge voltage of 0.10V/cell is said to double the cycle life. For example, a lithium-ion cell charged to 4.20V/cell typically delivers 300–500 cycles. If charged to only 4.10V/cell, the life can be prolonged to 600–1,000 cycles; 4.0V/cell should deliver 1,200–2,000 and 3.90V/cell should provide 2,400–4,000 cycles.

In terms of longevity, the optimal charge voltage is 3.92V/cell. Battery experts believe that this threshold eliminates all voltage-related stresses; going lower may not gain further benefits but induce other symptoms

[Siwastaja]

Measured with a charging cable with power display.

So some no-name Ebay thing? I would not trust it.

This article might be useful reading:

Never trust anything from batteryuniversity.com:

Lithium-ion suffers from stress when exposed to heat, so does keeping a cell at a high charge voltage. A battery dwelling above 30°C (86°F) is considered elevated temperature and for most Li-ion a voltage above 4.10V/cell is deemed as high voltage. Exposing the battery to high temperature and dwelling in a full state-of-charge for an extended time can be more stressful than cycling.

Most Li-ions charge to 4.20V/cell, and every reduction in peak charge voltage of 0.10V/cell is said to double the cycle life. For example, a lithium-ion cell charged to 4.20V/cell typically delivers 300–500 cycles. If charged to only 4.10V/cell, the life can be prolonged to 600–1,000 cycles; 4.0V/cell should deliver 1,200–2,000 and 3.90V/cell should provide 2,400–4,000 cycles.

Emphasis mine; this oversimplification has some truth in it, but take it with a grain of salt.

[Siwastaja]

But this phone also has the warning about not leaving it on charge.

There are multitude of reasons why such warnings would appear on manuals, and none of us knows all of them. Assuming they must be related to li-ion battery characteristics is likely to go wrong. I would place my bets that this clause is added to reduce risk of fire and electric shock when products are repaired with counterfeit batteries, or when manufacturer has quality control issues with their own batteries (happens rarely), or when the user has bought a crappy non-compliant power supply, which is pretty common. Limiting the time the device is plugged in to bare minimum does not remove these risks, but reduces them. Adding arbitrary limitations is always good for manufacturer from liability viewpoint, so it does not hurt them much. People just normally ignore them, so they are not a nuisance to most; no one buys a different brand of phone because manual said to stop charging.

[IanB]

There is absolutely no issues with leaving a phone plugged in for extended periods. You won't over-charge the battery doing this. The charge controller will simply stop charging when it's complete.

I strongly disagree with this.

I had an old phone that I was no longer actively using, but it had an app I wanted to keep running, so I left the phone on a desk plugged into a charger for a few months. Whereas before the battery would hold a charge for a week, it now will hold a charge for a minute or two before switching off.

I had the same situation with a laptop that was kept in the docking station 24 h/day. Its battery is now useless.

So in my case, there were definitely issues with leaving something plugged in all the time.

[Halcyon]

There is absolutely no issues with leaving a phone plugged in for extended periods. You won't over-charge the battery doing this. The charge controller will simply stop charging when it's complete.

I strongly disagree with this.

I had an old phone that I was no longer actively using, but it had an app I wanted to keep running, so I left the phone on a desk plugged into a charger for a few months. Whereas before the battery would hold a charge for a week, it now will hold a charge for a minute or two before switching off.

I had the same situation with a laptop that was kept in the docking station 24 h/day. Its battery is now useless.

So in my case, there were definitely issues with leaving something plugged in all the time.

It depends on the device. I've had a Samsung Galaxy S7 plugged in almost 24/7 for years, nil issues. Same with my Google Pixel phones. My old Lenovo ThinkPad, different story. It depends on the device, manufacturer, software and your individual configuration. What's the golden combination? Buggered if I know. I think it's a combination of "You get what you pay for" versus wisdom.

[IanB]

It depends on the device. I've had a Samsung Galaxy S7 plugged in almost 24/7 for years, nil issues. Same with my Google Pixel phones. My old Lenovo ThinkPad, different story. It depends on the device, manufacturer, software and your individual configuration. What's the golden combination? Buggered if I know. I think it's a combination of "You get what you pay for" versus wisdom.

If some devices have issues, we cannot say "absolutely no issues". We have to say, "there may be issues in some cases".

[Siwastaja]

I had an old phone that I was no longer actively using, but it had an app I wanted to keep running, so I left the phone on a desk plugged into a charger for a few months. Whereas before the battery would hold a charge for a week, it now will hold a charge for a minute or two before switching off.

So the battery just completely died. It is not a normal situation. You assume that because B happened after A, B must have been caused by A. In other words, you performed a rain dance ritual, and because it's now raining, it worked.

My guess is, the battery had just died on its own due to the age of the phone. It might have been overdischarged while in storage, for example.

Normally, holding the cell voltage near 100% voltage is still something that a battery can take for years. If not, the thing is broken, and holding at 4.2V is not the cause of the failure. Probably not even the trigger or a contributing factor, although that is possible.

You can disagree, but you are wrong, because facts do not care about agreement.

[IanB]

You can disagree, but you are wrong, because facts do not care about agreement.

You have the theory about lithium ion cell chemistry, I have a fact about a dead battery.

I know that I am going to be cautious about leaving things plugged in continuously, since lithium cell chemistry tells me that leaving a cell at a 100% state of charge for a long time will tend to shorten the lifetime of the cell compared to leaving it in the 50% range.

[Andy Chee]

Normally, holding the cell voltage near 100% voltage is still something that a battery can take for years.

Does Tesla still recommend charge termination at 80%?

I don't own a Tesla or any EV, so I don't know how charge management differs from mobile phones & laptops (if any).

[tooki]

I think the problem is this: confounding two related, but distinct, things.

One thing is “leaving plugged in”.
The other is “storing at 100% SoC”.

Lithium ion batteries do not like long-term storage at 100% SoC. Self-discharge and current draw from the device will lower the SoC, so the only way to maintain a 100% SoC is to regularly top it up. Many phones (though more and more are doing it differently) will do this if left plugged in. I once replaced the degraded battery in an iPhone 6 (my obsolete backup phone) with a new battery (replaced at an Apple Store, so zero chance of counterfeit battery) and after a year of being left plugged in, the battery swelled.

But I say that leaving plugged in is separate because it’s also possible to be plugged in permanently but not strive for 100% SoC, which is exactly what newer iPhones and countless other devices (phones, laptops, etc) do: they let you set a different SoC target, and/or use intelligence to modify the charging strategy themselves. (iPhones now, by default, learn your usage habits and charge up to 80% only when you go to bed, and then top up to 100% just before you wake up.) Thus, saying that a device shouldn’t be left plugged in all the time isn’t really correct advice, either.

What is categorically untrue is that leaving a device plugged in means it’s charging 24/7: doing that to a LiIon cell would kill it very quickly, be it with or without unscheduled rapid disassembly. Every LiIon charger chip uses proper CC/CV charging with defined termination voltage and current — in some configurable on the fly (e.g. via I2C), in others via config jumpers or resistors, and in others preset at the semiconductor factory. Only death-trap garbage from aliexpress ever uses “dumb” charging on LiIon, like the lantern bigclive found that used a capacitive dropper (!) to put unregulated DC directly onto the lithium cells and USB ports (including exposed metal)…

[Siwastaja]

You can disagree, but you are wrong, because facts do not care about agreement.

You have the theory about lithium ion cell chemistry, I have a fact about a dead battery.

Death of which was very unlikely caused by the normal use you described. But keep believing.

[Siwastaja]

Lithium ion batteries do not like long-term storage at 100%

Yeah, true. But remember the two-fold relativity of this: first, it might be a good compromise. Battery stored at 100% might still last longer than the desired lifetime of the device, especially if charge rates are small, temperature is never very high, and cells are of good quality (e.g. Panasonic and Sony cells I tested performed very well when stored at full charge).

Another relatively interesting feature is that storage at, say, 80-90% might not increase the life expectancy at all, it depends on the small details of cell chemistry; I have seen data where a cell stored at 80% loses capacity faster than at 100%, although my own measurements show a small improvement on nearly every specimen. The large and reliable improvements, however, only start significantly below 80%. Note this calendar fading is different from cycling damage: by limiting maximum SoC to 80%, cycling damage done on each cycle is significantly reduced.

[electronium]

According to my experience in the field of batteries, lithium batteries should not be overcharged and the battery will blow up, which is dangerous. As soon as the charging current reaches 10%, the current should be cut off.

[IanB]

Death of which was very unlikely caused by the normal use you described. But keep believing.

I don't have to believe. I simply can be cautious. It is completely harmless for me to act cautiously, and it might not be harmless for me to act otherwise. Therefore belief is not required to eliminate possible risks, it is does not matter how material those risks might be.

To give you a parallel: parachuting is a perfectly safe activity. On the other hand, if I never go parachuting, I am never going to get killed in a parachute accident.

[AVGresponding]

Death of which was very unlikely caused by the normal use you described. But keep believing.

I don't have to believe. I simply can be cautious. It is completely harmless for me to act cautiously, and it might not be harmless for me to act otherwise. Therefore belief is not required to eliminate possible risks, it is does not matter how material those risks might be.

To give you a parallel: parachuting is a perfectly safe activity. On the other hand, if I never go parachuting, I am never going to get killed in a parachute accident.

Technically, you could, if, say, a parachutist landed on you...

[Halcyon]

It depends on the device. I've had a Samsung Galaxy S7 plugged in almost 24/7 for years, nil issues. Same with my Google Pixel phones. My old Lenovo ThinkPad, different story. It depends on the device, manufacturer, software and your individual configuration. What's the golden combination? Buggered if I know. I think it's a combination of "You get what you pay for" versus wisdom.

If some devices have issues, we cannot say "absolutely no issues". We have to say, "there may be issues in some cases".

I think it's safe to say that the mere act of leaving a phone plugged in for extended periods will not damage the battery due to overcharging, however, it may shorten the battery life due to other factors, whether that be elevated temperatures, charging too quickly over its life, high number of charge/discharge cycles, poor product design etc...

I once replaced the degraded battery in an iPhone 6 (my obsolete backup phone) with a new battery (replaced at an Apple Store, so zero chance of counterfeit battery) and after a year of being left plugged in, the battery swelled.

I think there needs to be further explaination here. The iPhone 6 series were riddled with problems. Premature failure of the LCD/digitiser, to battery issues (as you have found out). The iPhone 6 were just a garbage phone with a very high failure rate. Not sure why, but when I was doing digital forensics examinations on an iPhone 6 that wouldn't boot, first thing that got removed was the battery and we powered them up using external power.

[PlainName]

I think it's safe to say that 'shorten the battery life' is what is included in 'damage the battery'.

[Siwastaja]

I have seen dozens of swollen batteries and they all swelled while stored at optimum state-of-charge and not plugged in. Still, I don't make a conclusion that storing at 30-60% SoC and unplugged causes swelling. My conclusion instead was, these cells were not of very high quality and just reached their end-of-life. Many other cells did not swell. Now, if I had some of those "plugged in" all the time, I guess they would have still swelled. I can totally see how easy it is then to reach a conclusion how the swelling must have been caused by them being "plugged in", especially when I can go to the echo chamber called the Internet and amplify this bias.

And yes, even good brands like Apple or Samsung have had battery issues, varying from faster-than-expected wear to outright battery fires and "explosions" (not actual explosions, but something which looks quite explosive to laymen).

[Halcyon]

I think it's safe to say that 'shorten the battery life' is what is included in 'damage the battery'.

The "may" in my response is very important, because it's not always the case. In fact, with many devices, they save themselves from users who know no better.

My point is, use the device as it has been designed and don't sweat the small stuff.

[Siwastaja]

use the device as it has been designed

... which is sometimes a bit difficult if you make the mistake of RTFM, making you even more confused about how the device has been actually designed to be used. For example, with instructions requiring you to unplug after charge, are you supposed to wake up in the middle of the night to see if the phone has been charged, just to unplug it? This then prompts for ideas that sound good in isolation, like a separate device which monitors the current and automagically disconnect the device after it is "apparently" fully charged; until you realize this obviously is a feature of the phone itself, it has to be; and the manual was just bullshit.

[gf]

Has anyone really evidence that a smart phone battery will last longer than roughly 500 charge/discharge cycles (or say 1-2 years of daily discharge/recharge) if it is not kept plugged-in after the battery has reached 100% SOC? I guess that a good charge controller is supposed to switch off after the saturation phase anyway.

[PlainName]

My current phone has been charged using the Accubattery app, since 7/5/20, to indicate when it should be terminated. According to that it is losing 0.7% per year. It's been my daily phone since 2018 and battery life is subjectively OK.

But... don't know how an equivalent one would be now with less care taken about charging. My partner has an A3 (the next but one model to mine) and I note that the phone is more often on charge than not when I see it - it runs flat a LOT faster than mine. However, there are excuses for that which wouldn't involve charging so they can't really be compared.

[PlainName]

I guess that a good charge controller is supposed to switch off after the saturation phase anyway.

Well that's the issue here - we are guessing, and no-one seems to know why some manufacturers (who, after all, would probably prefer not to make out that their product might be a bit iffy) state that the phone shouldn't be left on extended charge. If the charge controller, however that's implemented, could just consider the battery done and turn it all off, there would be no need for such warnings, would there? Indeed, does Apple have similar warnings despite apparently being able to control the charge from software?

[Buriedcode]

With all these anedotes flying about its worth remembering that each scenario has a lot of factors that aren't mentioned: 

1) Device current draw - we really don't know what your phone/tablet/laptop is doing.  Often phones will update and perform scans whilst idle but on charge, raising their temperature and power consumption. Simply leaving a device on charge doesn't mean its sleeping, or that its charging for that matter.  And it may charge to 100%, then update, using up a fair chunk of battery life and start charging again quite quickly once the charge level has dropped below 80%. Or... it may do none of those things.

2) Enviromental - ambient temp? humidity?

3) The obvious one - usage.  It's very easy to say things like "heavy use" or "constant use" but both terms are subjective.  I've sometimes used my phone for frantically googling for part availability, on site, with poor converage and drained my battery down within an hour.   Other times doing the same thing next to a WiFi hotspot and barely dropped 10% in an hour.  Actual usage correlates with power consuption but its not an easy comparison, so judging battery life vs usage has so many variables you can't really be certain.

I'm fairly sure the takeaway for PlainName is:  Don't worry.  Even the cheapest modern devices handle the charging just fine, and any gains to be made by micromanaging the SoC and charge terminations will most likely be marginal.  Unless you're living somewhere with an ambient temp constantly above 30C, or you're using a wireless charging pad (that heat up a fair bit) in high ambient temps, your battery will be fine.

[Buriedcode]

I guess that a good charge controller is supposed to switch off after the saturation phase anyway.

Well that's the issue here - we are guessing, and no-one seems to know why some manufacturers (who, after all, would probably prefer not to make out that their product might be a bit iffy) state that the phone shouldn't be left on extended charge. If the charge controller, however that's implemented, could just consider the battery done and turn it all off, there would be no need for such warnings, would there? Indeed, does Apple have similar warnings despite apparently being able to control the charge from software?

As has been pointed out a few times - documentation meant for consumers is often boilerplate, generic, and has parts left over from previous documentation that may or may not be applicable to your device.
The leaflet that came with my phone mentions not to leave it on charge in four places.  And I am sure Apple, Samsung, Google will have similar statements in their manuals to cover themselves. 

It is far easier to use up extra ink and printing space on documentation than the tiny risk of potential future law suits from not explicitly and repeatedly stating instructions to minimise the small possibility of failure-leading-to-injury. 

A random example: Some snow cleats I have for boots, on the instructions mention "The use of this product does not prevent injury from falling in snowy/icey conditions, take extra care when walking in such conditions as this product does not prevent injury" - see the repetition?

On the off-chance I'm wrong: I would have thought that the review from your device would mention battery issues - if the device mismanaged the charging it would be obvious fairly early on in the devices life.

[tooki]

I once replaced the degraded battery in an iPhone 6 (my obsolete backup phone) with a new battery (replaced at an Apple Store, so zero chance of counterfeit battery) and after a year of being left plugged in, the battery swelled.

I think there needs to be further explaination here. The iPhone 6 series were riddled with problems. Premature failure of the LCD/digitiser, to battery issues (as you have found out). The iPhone 6 were just a garbage phone with a very high failure rate. Not sure why, but when I was doing digital forensics examinations on an iPhone 6 that wouldn't boot, first thing that got removed was the battery and we powered them up using external power.

I don’t think that this “further explanation” is either reasonable or relevant.

For one, the other issues you mention are unrelated and thus totally irrelevant, and I don’t actually believe it had a significantly high failure rate in the long run*. Second, the same device (not another unit of the same model, the same exact unit) had no trouble with its battery when used “normally”, i.e. plugged in overnight but unplugged during the day.

If you don’t even know why you were removing the battery and powering it externally, I hardly consider that a useful anecdote (never mind a data point).

The point was this: the same phone, with the battery used normally, did not result in swelling. But leaving it plugged in 24/7 did, with a brand-new, first-party battery.


*There are few public statistics on failure rates on iPhone models before and after the 6, and what statistics do exist are incomplete and aren’t adjusted for life cycle. (E.g. they compare the iPhone 6 two years in vs the iPhone 7 shortly after launch. So the iPhone 6 looks bad, but it’s unclear whether it actually was that much worse over its lifetime.) IMHO what matters is the failure rate after 3-4 years of use, excluding consumables and accidental damage. Also, I’m not sure if the stats include battery replacements or not: for sure, the iPhone 6 (and all other models in the same basic enclosure design, i.e. 6S, 7, 8, SE (2nd), and SE (3rd)) all have IMHO undersized batteries that get absolutely hammered in normal use, but it’s still arguable to call this wear and tear of a consumable item, not failure in the context of reliability stats.

[Siwastaja]

if the device mismanaged the charging it would be obvious fairly early on in the devices life.

Which is also the practical, common sense message to those who don't believe in "theoretical" knowledge - if it was normal for a phone battery to completely die by sitting two months plugged in, we would be seeing a lot of complaints, and N would be in millions, not 1.

[tooki]

Has anyone really evidence that a smart phone battery will last longer than roughly 500 charge/discharge cycles (or say 1-2 years of daily discharge/recharge) if it is not kept plugged-in after the battery has reached 100% SOC? I guess that a good charge controller is supposed to switch off after the saturation phase anyway.

Only tangentially relevant, but some LiIon batteries do give multiple cycle life specs depending on usage (for example, the Samsung INR18650-32E datasheet gives a cycle life of 500 cycles when discharged at 3.2A, but just 300 cycles when discharged at 6.4A). But of course we don’t have access to the raw battery specs in a smartphone, just the sanitized/dumbed-down specs given with the phone itself. :/

[tooki]

I guess that a good charge controller is supposed to switch off after the saturation phase anyway.

Well that's the issue here - we are guessing, and no-one seems to know why some manufacturers (who, after all, would probably prefer not to make out that their product might be a bit iffy) state that the phone shouldn't be left on extended charge. If the charge controller, however that's implemented, could just consider the battery done and turn it all off, there would be no need for such warnings, would there? Indeed, does Apple have similar warnings despite apparently being able to control the charge from software?

Here’s what Apple says right now:
https://support.apple.com/en-us/105105] [url]https://support.apple.com/en-us/105105[/url]

Charge and maintain your iPhone battery
Learn about charging the battery in your iPhone and how you can prolong your battery's lifespan.

About your battery's lifespan
A battery’s lifespan is related to its chemical age, which is more than just the length of time since the battery was assembled. A battery’s chemical age results from a complex combination of several factors, including temperature history and charging pattern. All rechargeable batteries are consumable components that become less effective as they chemically age. As lithium-ion batteries chemically age, the amount of charge they can hold diminishes, resulting in reduced battery life and reduced peak performance.
Learn more about iPhone battery and performance
Learn how to maximize battery performance and lifespan

How charging affects your battery
For most customers, the battery in your iPhone should last the whole day. You can charge your iPhone every night even if the battery isn't fully depleted.
iPhone automatically stops charging when the battery is fully charged, so it's safe to keep your iPhone connected to a charger overnight. Charging resumes automatically if your battery level drops below 95 percent.
When possible, unplug your iPhone after it has fully charged. By default, your iPhone uses Optimized Battery Charging. To improve your battery's lifespan, Optimized Battery Charging reduces the time that your iPhone spends fully charged. It fully charges your iPhone just in time for you to use it.
A battery warms up as it charges, which can reduce its lifespan. To reduce the effect of heat and prevent overheating, iPhone gradually reduces the charging current as the battery approaches full charge.
Learn more about Optimized Battery Charging

How temperature affects your battery
iPhone is designed to perform well in a wide range of ambient temperatures, with 62° to 72° F (16° to 22° C) being the ideal comfort zone.
Avoid using or charging your device in ambient temperatures higher than 95° F (35° C), which can permanently reduce battery lifespan.
When using your device in a very cold environment, you might notice a decrease in battery life. This condition is temporary; when the battery’s temperature returns to its normal operating range, its performance will return to normal.
Software might limit charging above 80 percent when the recommended battery temperatures are exceeded.
Learn more about how temperature can affect your iPhone

How Wi-Fi and Bluetooth affect your battery
Wi-Fi and Bluetooth are designed to draw minimal power from the battery when they aren't connected to a network or accessory. For the best experience on your iPhone, keep Wi-Fi and Bluetooth turned on.
Some features might not work if you turn off Wi-Fi or Bluetooth
Learn how to check our your battery health and other information about your battery

Published Date: November 15, 2023

Interestingly, on the page about optimized charging (link above), it says this:

About 80% Limit with iPhone 15 models
With iPhone 15 models, you can choose between Optimized Battery Charging, 80% Limit, and None.
When you choose 80% Limit, your iPhone will charge up to about 80 percent and then stop charging. If the battery charge level gets down to 75 percent, charging will resume until your battery charge level reaches about 80 percent again.
With 80% Limit enabled, your iPhone will occasionally charge to 100 percent to maintain accurate battery state-of-charge estimates.

The fixed 80% is new, and I’m not sure why they wouldn’t enable that software option for older devices, too.

[PlainName]

And I am sure Apple, Samsung, Google will have similar statements in their manuals to cover themselves.

You are guessing, and doing worse than the rest of us. I've already posted a quote from Samsung on this so clumping that in with Apple and Google is a bit disingenuous. Maybe you could quote from the Apple manual where it says the same?

[PlainName]

On the off-chance I'm wrong: I would have thought that the review from your device would mention battery issues - if the device mismanaged the charging it would be obvious fairly early on in the devices life.

How long do you think it would take to notice lack of  battery capacity? A week? Two? Come on - you are making stuff up again. My current phone has lasted 5.5 years and I would like the new one to last that long, not least because the battery is no replaceable and it's a bloody expensive phone to bin just because someone said it won't burst into flames if you leave it on charge.

[PlainName]

The fixed 80% is new, and I’m not sure why they wouldn’t enable that software option for older devices, too.

Because they'd get reamed for it. Recall what happened why they slowed phones down to make the batteries last a bit longer.

Which leads me to...

Suppose you (as a manufacturer) can control the battery charge in an on/off fashion. Once it gets up to whatever you consider fully charged you can flip the switch and the charge is turned off. Being clever, you can arrange that the battery is just fully charged when the user wakes up in the morning, either from monitoring their usual wake time or by looking at the set alarm. You can put off charging until the exact time before wakeup that it will take to charge, or you can wait until it's at 100% (or the preferred level), turn it off and then just before wake give it a couple of minutes to make up for what's since drained.

Magic. But what if the user has irregular hours and/or doesn't use the phone alarm? You could wait until full charge and then turn it off, but you wouldn't know when to do the last moment top up. The user could be taking it away in the next minute or they might've gone off on holiday, and you won't know until the cable is pulled. Is the top up important? I think it is, because if the user puts it on charge and then goes to use it and finds it at only 95% they will get a bit annoyed. Especially if it's habitual.

OK, so you can't afford (reputation-wise) to take it off charge unless you know how long it will be on charge (cf. alarm, etc). You could fake the charge - if the actual charge is 95% when the user pulls the cable you could say it's 100% and they'd never know, but then you'd have to fake the fall in charge during use because the user would notice an unaccountable step. I think Apple have tried something like this in the past and got roundly told off.

So the end result is that although you have the ability to limit excess charge, it's more than your job's worth to actually do that except for specific circumstance. Just put a warning in the manual to not leave it on charge overnight (unless the alarm is set) and job's a good 'un. But the  battery charging is suboptimal and will wear the battery prematurely. But that's 2-3 years away and you can just flog them a new phone then.

I'm surprised Apple doesn't allow the 80% to be flexible according to user preference. Perhaps there is some hardware setting involved which can't be software controlled.

[PlainName]

if it was normal for a phone battery to completely die by sitting two months plugged in, we would be seeing a lot of complaints, and N would be in millions, not 1.

Absolutely! But that's a straw man and you know it - no-one has suggested anything like that timescale.

[Halcyon]

I guess that a good charge controller is supposed to switch off after the saturation phase anyway.

Well that's the issue here - we are guessing, and no-one seems to know why some manufacturers (who, after all, would probably prefer not to make out that their product might be a bit iffy) state that the phone shouldn't be left on extended charge. If the charge controller, however that's implemented, could just consider the battery done and turn it all off, there would be no need for such warnings, would there? Indeed, does Apple have similar warnings despite apparently being able to control the charge from software?

I would suggest that it's likely the manufacturer (or whoever wrote the manual) don't actually know any better or, they know full well their product is crap, the battery is going to swell and the user isn't going to follow their instructions, therefore they can turn around to the user and say "you didn't follow instructions" while denying any warranty claims. They would probably get away with the latter in many countries without strong consumer protections.

[Halcyon]

If you don’t even know why you were removing the battery and powering it externally, I hardly consider that a useful anecdote (never mind a data point).

Because some models of iPhones will refuse to boot properly if the battery has failed, even if you connect it to external power via the data port. The iPhone 6, 6S and 6 Plus are among them.

To get it to boot, you need to physically dismantle the handset, remove the failed battery and either replace it with a known good one, or power it externally via the pins which would ordinarily connect the battery to the mainboard. There are purpose built jigs to do this which are easily available online.

This is based on my own personal experience after examining and extracting data from hundreds and hundreds of iPhones. Whenever I get an iPhone 6 and it's stuck in a boot loop, it's usually the battery causing it.

[Siwastaja]

if it was normal for a phone battery to completely die by sitting two months plugged in, we would be seeing a lot of complaints, and N would be in millions, not 1.

Absolutely! But that's a straw man and you know it - no-one has suggested anything like that timescale.

I mean, it was literally* here: https://www.eevblog.com/forum/chat/battery-overcharing/msg5241633/#msg5241633

*) not two, but "a few", sorry.

[PlainName]

they know full well their product is crap, the battery is going to swell and the user isn't going to follow their instructions, therefore they can turn around to the user and say "you didn't follow instructions" while denying any warranty claims.

OK, so you now agree that there may be a battery issue (not necessarily swelling - reduced life is sufficient) if the device is left on charge past when it is fully charged?

[PlainName]

I mean, it was literally* here: https://www.eevblog.com/forum/chat/battery-overcharing/msg5241633/#msg5241633

*) not two, but "a few", sorry.

OK.

[Halcyon]

they know full well their product is crap, the battery is going to swell and the user isn't going to follow their instructions, therefore they can turn around to the user and say "you didn't follow instructions" while denying any warranty claims.

OK, so you now agree that there may be a battery issue (not necessarily swelling - reduced life is sufficient) if the device is left on charge past when it is fully charged?

It's not a matter of "now" agreeing with something, my stance and advice hasn't changed.

Suffice to say, that billions of phones are plugged in to charge overnight, every night and we aren't seeing a huge failure rate even after a few years. It would be misleading to say that leaving it plugged in like this will cause problems, or even premature failure.

With or without those "battery saving" technologies, all batteries degrade. How fast that happens largely depends on the device, your settings and your habits. As I said earlier 99% of consumers are not going to care (or even understand the science behind this) and will charge their phone so it's ready to go when they need it to be, and there is nothing wrong with doing that. As someone who does know, I still charge my phone every night*, even sometimes several times a day and I still use quick charge when I know I'm about to go out and I need extra charge in my phone.

*Something I have done since my first mobile phone in 1997.

[IanB]

No-one has ever suggested that plugging a phone in every evening to charge overnight would cause a problem. Millions of people do that, and it evidently is a normal and expected way to use a phone.

What is being suggested is that if you take a phone, plug it into the charger, and leave it like that without unplugging it for several months, then that might cause a problem.

This is obviously hard to gather data for, since very few people do that with a phone. The whole point of a phone is that you carry it with you.

Siwastaja says that in theory that shouldn't cause a problem. What I say is that we don't know if every sample of a battery, and every embodiment of a battery and charging system out there, is without flaw in design or manufacture.

Enough people have reported problems with leaving a device plugged in and on charge for days, weeks, months continuously that it might be a problem. I think there is enough doubt in this area that it is not worth taking the risk.

[Halcyon]

No-one has ever suggested that plugging a phone in every evening to charge overnight would cause a problem. Millions of people do that, and it evidently is a normal and expected way to use a phone.

What is being suggested is that if you take a phone, plug it into the charger, and leave it like that without unplugging it for several months, then that might cause a problem.

This is obviously hard to gather data for, since very few people do that with a phone. The whole point of a phone is that you carry it with you.

Siwastaja says that in theory that shouldn't cause a problem. What I say is that we don't know if every sample of a battery, and every embodiment of a battery and charging system out there, is without flaw in design or manufacture.

Enough people have reported problems with leaving a device plugged in and on charge for days, weeks, months continuously that it might be a problem. I think there is enough doubt in this area that it is not worth taking the risk.

Indeed. However one interesting piece of anecdotal evidence I can share is this: In my previous job, we did have a mobile phone which spent 90-95% of its life plugged into the charger. It was an old Samsung Galaxy S7 I think from memory, but in any case, it was used as an on-call phone. Most people when they were on-call simply diverted the number to their private phones so they didn't have to carry two phones around.

That original battery was still going strong mid last year. My only thoughts on this was that it had very low charge/discharge cycles and when it was off charge, it would only be for a few hours or half a day at most.

Despite how "bad" it may be to keep these types of batteries always at 100%, perhaps any damage was offset due to its low use and relatively easy life?

And before anyone has a dig at me saying that this doesn't prove anything: I realise this is a sample size of 1, so take it as you will.

[Siwastaja]

No-one has ever suggested that plugging a phone in every evening to charge overnight would cause a problem. Millions of people do that, and it evidently is a normal and expected way to use a phone.

What is being suggested is that if you take a phone, plug it into the charger, and leave it like that without unplugging it for several months, then that might cause a problem.

It would need to be a very weird "feature", I'd say bug, because overnight charging already is a significant %, nearly 50% for some people, so upping that to 100% is not going to be a massive difference. But of course, anything can happen, faulty products and weird corner cases pop up every now and then, especially for something which does not see much testing. Although I think you might underestimate the number of people who use the phone plugged in for nearly 24/7. Think about those who drive for a living (bus, taxi, truck drivers etc.) who plug the phone in the car, and also for the night. It might be plugged in for 22 hours a day.

But of course, there might be a plain old bug which triggers when the phone has been continuously plugged in for, let's say 24.855 days, after which a signed 32-bit integer counting milliseconds wraps around, and maybe triggers increase of charge voltage from 4.20V to 4.40V. Or something like that. It is just way more likely that your battery was already in bad condition and not specifically killed by what you did, but without forensics, we are guessing.

[IanB]

It is just way more likely that your battery was already in bad condition and not specifically killed by what you did, but without forensics, we are guessing.

Yes, and I have read and absorbed what you have said, and I agree that this may be the case. I assume from the tone of your replies that you have some expertise in the matter, and expert opinions are always worth listening to.

[tooki]

The fixed 80% is new, and I’m not sure why they wouldn’t enable that software option for older devices, too.

Because they'd get reamed for it. Recall what happened why they slowed phones down to make the batteries last a bit longer.

That is not at all what happened.

They got reamed, above all, for not explaining what it was doing (and why) from the start. They absolutely should have been transparent about the feature and how it operates, but people felt it got snuck in silently, and because of the lack of transparency, people didn’t see it as a “feature”, only as a limitation.

That function was not, and is not, to make the batteries last longer (cycle life (number of cycles)) or run longer (runtime of a charge). Its purpose is to limit maximum current consumption to a level that a degraded battery (=higher internal resistance) is still capable of reliably delivering, with the goal of preventing random shutdowns due to brownouts. This is why it doesn’t do it when a battery is in “healthy” condition, and why only heavy loads see a throttling effect.

Apple has often added new features and options to old hardware via software updates. That’s not controversial as such.

Which leads me to...

Suppose you (as a manufacturer) can control the battery charge in an on/off fashion. Once it gets up to whatever you consider fully charged you can flip the switch and the charge is turned off. Being clever, you can arrange that the battery is just fully charged when the user wakes up in the morning, either from monitoring their usual wake time or by looking at the set alarm. You can put off charging until the exact time before wakeup that it will take to charge, or you can wait until it's at 100% (or the preferred level), turn it off and then just before wake give it a couple of minutes to make up for what's since drained.

Magic. But what if the user has irregular hours and/or doesn't use the phone alarm? You could wait until full charge and then turn it off, but you wouldn't know when to do the last moment top up. The user could be taking it away in the next minute or they might've gone off on holiday, and you won't know until the cable is pulled. Is the top up important? I think it is, because if the user puts it on charge and then goes to use it and finds it at only 95% they will get a bit annoyed. Especially if it's habitual.

OK, so you can't afford (reputation-wise) to take it off charge unless you know how long it will be on charge (cf. alarm, etc). You could fake the charge - if the actual charge is 95% when the user pulls the cable you could say it's 100% and they'd never know, but then you'd have to fake the fall in charge during use because the user would notice an unaccountable step. I think Apple have tried something like this in the past and got roundly told off.

What are you talking about?

What practically all mobile devices do is to recalibrate the SoC meter regularly, so that 100% full means “100% of the battery’s current capacity” and not “100% of the battery’s original capacity”. My 3 year old iPhone SE (2020)’s battery, for example, shows its maximum capacity as 80% (meaning that the battery is now only capable of holding 80% as much energy as when it was new), but the SoC meter still shows 100% when it has reached that, because it’s 100% of what the battery can hold today. Any device that uses rechargeable batteries and aims to have an accurate battery SoC indicator will use a so-called “fuel gauge” IC, which uses a coulomb counter to track current going into and out of the battery, combined with complex characterization of the load, to give predictions about remaining run time, etc. (Even if your phone doesn’t display a countdown timer like laptops used to do, it’s still using it internally to know when it must begin an emergency shutdown of the OS.) Fuel gauge ICs use sophisticated algorithms to not only predict runtime, but also to track battery degradation so that the percentage and runtime estimates can remain accurate.

[tooki]

No-one has ever suggested that plugging a phone in every evening to charge overnight would cause a problem. Millions of people do that, and it evidently is a normal and expected way to use a phone.

What is being suggested is that if you take a phone, plug it into the charger, and leave it like that without unplugging it for several months, then that might cause a problem.

This is obviously hard to gather data for, since very few people do that with a phone. The whole point of a phone is that you carry it with you.

It is, however, the fate of many a laptop battery: plugged in for months at a time and only occasionally run away from AC power. So I’d think that laptop manufacturers would have ample data to pass onto battery (and charger IC) suppliers.

[tooki]

No-one has ever suggested that plugging a phone in every evening to charge overnight would cause a problem. Millions of people do that, and it evidently is a normal and expected way to use a phone.

What is being suggested is that if you take a phone, plug it into the charger, and leave it like that without unplugging it for several months, then that might cause a problem.

It would need to be a very weird "feature", I'd say bug, because overnight charging already is a significant %, nearly 50% for some people, so upping that to 100% is not going to be a massive difference. But of course, anything can happen, faulty products and weird corner cases pop up every now and then, especially for something which does not see much testing. Although I think you might underestimate the number of people who use the phone plugged in for nearly 24/7. Think about those who drive for a living (bus, taxi, truck drivers etc.) who plug the phone in the car, and also for the night. It might be plugged in for 22 hours a day.

But of course, there might be a plain old bug which triggers when the phone has been continuously plugged in for, let's say 24.855 days, after which a signed 32-bit integer counting milliseconds wraps around, and maybe triggers increase of charge voltage from 4.20V to 4.40V. Or something like that. It is just way more likely that your battery was already in bad condition and not specifically killed by what you did, but without forensics, we are guessing.

Well that’s reeeeeallly grasping at straws if you ask me.

Laptops, mobile phones, and cordless power tools have been in wide use for decades now, and even electric cars are now a reasonably mature technology, so there’s a deep base of real-world data to fall back on. Not to mention that manufacturers can do artificial tests additionally.