Electronics > Beginners

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

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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:

--- Quote from: epigramx on February 03, 2020, 09:15:35 am ---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.

--- End quote ---

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.

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