Battery overcharing

[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?