Strange 1% battery issue

[Mark582]

So today my battery drained down to 1% and got stuck at 1% for about 2 hours. This has happened a few times now where the last 1% lasts a lot longer than it should based on the battery life.

I have a feeling this is something to do with the brightness.

When I am out in the sun I need to have my brightness turned up to maximum to compete with the sun to be able to see my screen outdoors, however when it hits 1% the autobrightness seems to go into emergency power saving or something similar?

It means I can hardly see the display unless I go indoors or go into shade, which isn't a huge issue but just wondering if this is a common issue or rare and if anyone has any idea what to do?

It's on an S8 Plus - EE (Verizon?) - Android 8

 

[TFBisquit]

Below 5% the s8 goes into emergency mode, many things won't work anymore but you're still able to make a call. Brightness or Auto brightness goes down too.

Btw Auto brightness works wonders and remembers the values you adjust in various light conditions. You can still change it in Auto mode to your liking.

 

[Rukbat]

It can also be an issue of exactly what 1% means. The only way to directly measure the State of Charge of the battery is disassembling it and measuring the chemical state, so we can't do that. (It's a destructive test - do it once, then dispose of what's left of what used to be a battery.) So we measure the voltage of the battery under load (in other words, when the phone is turned on). That's kind of close, but not exact, and different manufacturers do it (converting voltage to State of Charge) better than others. When the battery reaches 0%, there's still enough charge left in it that if you short it, it can explode. And some batteries have a "dead battery switch", that disconnects the battery itself from the terminals if it gets discharged too low - and it has to be disassembled and repaired to use it after that, which costs a lot more than a new battery. Most lithium batteries, even if they don't reach the"disconnect" state, if they're brought down too low have to be precharged before they'll accept a charge, and 1% is almost always below that point. (And most cellphones don't do precharging.) Discharging the battery that much also shortens its life very appreciably. Discharging to 1% regularly may give you a year, and for the second half of that time you'll be getting to 1% a lot faster.

If you want your batteries to last, charge at 40%, stop charging at 80%. If you get a new phone every 6 months, don't worry about it - someone buying your phone as a "refurb" will be returning it very quickly because the battery won't be lasting very long between charges.

(Why can we only get 40% of the battery capacity? Two reasons. Lithium is the lightest metal, so they can make batteries that don't weigh more than the phone [and a lead acid deep-cycle battery for the average phone would weigh a few pounds] and a lithium polymer battery can be made almost any shape, so it can be fit into any design phone - long and narrow, very thin, even curved. A deep-cycle lead acid battery, even as a gel-cel, can't be. They'd have to design the phone around the battery. But we want light and thin phones. So we're stuck with 4-6 hour "between charge" times.)

As for your battery, who knows how close it is to end of life? If you keep abusing it like that long enough (and the phone's been out almost 14 months) it can be exhibiting all sorts of strange behavior. Maybe that initial drop to 1% means 10% until the battery shuts off. Or maybe the calibration curve stops at 5%, because even that is terribly abusing a lithium battery.

 

[Mark582]

Oh I mean I don't intentionally allow it to drop to 1% just sometimes runs down quick when out and about. It's on those odd occasions where I go out spur of the moment or I forget to bring my charger with me (or don't want it in my pocket).

Ideally I charge before it gets low, but 40% sounds a good target figure.

However I did get the battery replaced in the shop (only 1 month ago). However it seems that the battery life is just as slow as before (I did check with the guy that this was an official battery and saw that it was).

I do believe it is the brightness being higher that is causing it to drain faster the most (but I have needed it pretty high when outdoors in direct sunlight, I've had situations where I can't see the screen at all to unlock it unless I put it close to max brightness outdoors, however indoors I have it a reasonable setting but have put auto brightness back on for now).

Although I think the sun being this bright is causing it to drain faster as once I go outside and use it that's when the brightness is high and hence it drains faster.

The question was more about the 1% - but yes it does seem like a false reading.

 

[Rukbat]

Yes, some phones act like that, others get to 2% or 1%, then die quickly - quicker than you'd expect for a 1% change. But that "I go out spur of the moment or I forget to bring my charger with me (or don't want it in my pocket)" is something you should break yourself of. Even if I don't think I'll need it (like a visit to a doctor who's normally quick), the power bank going into the pocket is as important as the car keys going into the pocket. I normally don't need it, but even a few 1% drops are enough to drastically shorten the battery life - it costs me nothing to bring the power bank and, now that batteries aren't removable (on any phone I want to own), replacing batteries do cost. (And cost a week to send the phone in and wait for it to come back). I just won't leave home without it, except for a food shopping trip.