Do phones nowadays disconnect the battery when it's charged(with a charger on)?

[epigramx]

I know this isn't exactly a DIY question but since Google gives the CLEAR answer that "you must always disconnect it from the charger when it's charged" and that sounds potentially bs and misleading to millions of people I had to ask people that are more interested in actually looking into the reality of it. So do modern phones nowadays just disconnect the battery from charging(or even from being a power source) so it's safe (AND BETTER!) to actually keep them plugged in when at home(and if yes what other devices do that (laptops etc.) and how can we determine it for sure)?

[Howardlong]

The charging circuit will stop charging the battery once it's full by design.

The reason to disconnect is probably butt covering nonsense around (a) failure of the charging circuit and (b) saving the planet.

(a) Can be real as the typical failure mode of Mosfets is Drain-Source short, and even a PTC resettable fuse will allow some current to flow. Overcharging LiIon cells is never a good idea. Either way, one would hope the charging circuit has a reasonable amount of defensive design.

(b) Leaving an unused charger plugged in does indeed waste power, however you need to put it into perspective. "All the energy saved in switching off your charger for one day is used up in one second of car-driving" - https://www.withouthotair.com/c11/page_68.shtml

[epigramx]

I wonder if the phones (or laptops and of course tablets) typically keep drawing power from the battery itself so it would make it less safe - for the battery - (potentially) to keep it plugged in. Though judging by my phone which doesn't seem to turn on and off charging just by leaving it plugged I guess it draws from the DC in and the battery is left untouched unless I guess it discharges due to time alone (and perhaps with a deadzone of not being charged unless at least a good percentage is gone). Then again all that might depend on the specific phone but if someone has experience in a various modern phones and all of them have identical behavior at that then it would be safe to assume it's most probably the same on others.

[Howardlong]

In general, the aim for LiIon is to stop charging once the battery is full. If it's plugged in, the device is powered from the charger, not the battery, and the battery remains full.

By habit I tend to leave my phone plugged in next to me throughout the day on my desk/bench whether it's full or not. Following a regime like this means I never find myself with an exhausted battery.

As I suggested earlier, it would be a design failure if leaving it plugged in was likely to cause a problem.

[BravoV]

I wonder if the phones (or laptops and of course tablets) typically keep drawing power from the battery itself so it would make it less safe - for the battery - (potentially) to keep it plugged in. Though judging by my phone which doesn't seem to turn on and off charging just by leaving it plugged I guess it draws from the DC in and the battery is left untouched unless I guess it discharges due to time alone (and perhaps with a deadzone of not being charged unless at least a good percentage is gone). Then again all that might depend on the specific phone but if someone has experience in a various modern phones and all of them have identical behavior at that then it would be safe to assume it's most probably the same on others.

Most modern ones are basically were designed in mind to cut off totally the charging to the Li-Ion once its full, hence constantly plugging is not an issue.

Although only at a particular product or brand, for example my tablet has a feature, from factory to enable an option for NOT to fully charge the batteries, hence longer life.

Attached below the example, look at the bottom item at the "Protect battery" explanation.

[amyk]

See here for some more discussion... https://www.eevblog.com/forum/projects/samsung-phones-are-charging-batteries-with-an-ugly-pattern/

[epigramx]

See here for some more discussion... https://www.eevblog.com/forum/projects/samsung-phones-are-charging-batteries-with-an-ugly-pattern/

Not sure about the reliability of this (other than the fact the OP is lecturing a conspiracy theory). I didn't know Android exposes a battery current draw for apps so that's interesting. But I don't know if it can be trusted for this question or if it even distinguishes between battery draw and AC draw properly.

[bob21]

I think I may actually be able to offer some valuable input on this.

In an ideal world, the battery would charge to 100%, then stop and just power the phone from the charger. But, if the phone design is poor, what tends to happen is that the battery charges to 100%, charging stops, the phone then switches to the battery, it drops slightly and then constantly trickle charges. Since most damage to lithium cells happens in the last 10% of charging, this is generally considered a bad idea. This is all according to battery university though, and I don’t pretend to know a great deal about lithium cells.

https://batteryuniversity.com/index.php/learn/article/charging_lithium_ion_batteries

You can also prolong the life of your lithium cells by charging at a slower rate, as less heat is generated - the bane of lithium cells. Ie. Charging at 1A will cause less damage than at 2A, but will obviously take longer. If you have time, use a 1amp plug.

There’s probably a massive difference of opinion on this subject, but I treat my phones as battery university suggests and find that my battery lasts longer than friends who do the opposite. YMMV.

[BravoV]

Not an expert, its just I remember this video so well and learnt a lot.

The sweet spot for Li-Ion, according to Jeff Dahn at below video is at 4.03 volt ... approx. about 80%, and gets worst above 4.1 volt.

I marked the time at 1h07m, in this Youtube video where its discussed this particular issue ...

-> https://youtu.be/pxP0Cu00sZs?t=1h7m5s

Even though its a 1 hour 14 mins video length, recommending to watch this Prof. Jeff Dahn video from the beginning, its very informative, imo.

[bob21]

Yeah that would also tie in with the battery university guys.

I think in an ideal world you’d never want to charge past 80%, definitely not 90%. There are android apps that monitor then scream at you when it’s time to unplug.

At the end of the day though, you’ve got to weigh it up. The stress of worrying about a replaceable unit vs just doing the easy stuff (1A charger, don’t charge overnight, unplug when full, let it die completely, don’t plug/unplug/plug/unplug (cars!)).

These are the things I do and my iPhone 8 from September 2017 is still at 88% of max capacity. :-)

[epigramx]

Point of the thread though is that the "~80%" methods are a drop in the bucket if a phone completely disconnects the battery when it's plugged in. A lot of people spend 80% of their life on the same spots. Having a phone plugged in would be effectively like not using a battery at all (in that case).