I have a Samsung laptop that I bought in August of '22. Since a couple weeks ago the battery has only been charging up to 79%. Anybody know why? And does thismean I need to buy a new battery?
Everything I’ve read says that you don’t want your battery to have more that an 80% charge.
It may be Samsung’s Battery Life Extender feature:
As crowmanyclouds said, batteries last longer when they aren’t charged completely to 100%. So some devices (electric cars, laptops, phones, etc.) have features to limit the max charge.
The link above says 85% but other sources say that it may be 80% on some models.
I’d leave the feature on unless you really need the extra juice for some reason (you’re traveling, etc.).
I’ve read some (all?) cell phone manufacturers limit the charge on the battery in an effort to extend battery life, e.g. it will stop charging at 80% instead of 100%. But they also know that users would be unhappy if the phone shows the charging has stopped at 80%. So they apply an offset in the firmware: when the battery is being charged and the actual charge reaches 80%, it will display 100%, and stop charging.
There is no true 100% level for any battery. It’s at the manufacturer’s discretion, and there is a tradeoff between lifetime (cycle count) and max charge.
So one manufacturer’s 80% might well be another’s 100%, if cycle count is more important to them for whatever reason (marketing, expected usage, warranty, etc.).
But manufacturers want the best of both worlds. So in some cases they’ve added features to limit the charge limit most of the time while still allowing the user to override it under special circumstances. Many EVs allow this (recommending to charge to 80% for daily use but allowing 100% if they’re going on a road trip), and now laptop and cell phone makers are doing the same thing, often calling it a “battery saver” or the like.
There is the tradeoff that some people won’t understand what’s going on due to inadequate communication. But overall it’s a good thing as it gives people a choice in how they want to use the battery.
I leave my laptop plugged in all the time. Essentially I am using it as though it was a desktop. It is always 95% charged. Am I damaging the battery? Also, I sometimes leave my phone charging over night. Is this wrong?
If you replace/upgrade your devices every few years, you won’t notice the difference. But if you really want to maximize the lifetime, yes, you’re (slowly) damaging the battery by keeping it fully charged all the time.
My phone (a Pixel 9) has scheduled charging that doesn’t start charging until it needs to so that it’ll be ready when my alarm goes off. I suspect lots of phones have similar features now. You might not even notice that they’re enabled.
Laptops were later to the game when it comes to these features. I had a friend that (a few years ago) set up a wifi power switch that turned off the charger when it was over 80% or so. A good idea but a lot of work for a typical person.
There’s really no great solution unless the device already has a battery limiter feature. Either you do it manually (annoying) or hack together some system (out of range for most people). Personally, I don’t worry about it but I will be looking for the feature on future purchases.
I believe it was you that said in some other thread that whether or not a battery is charged to whatever the manufacturer designates as full capacity is less important than how long it remains at full capacity. It seems to be common wisdom from multiple sources that for long-term storage a battery should be at around 40-50% charge.
I have a tablet that I use constantly (my standard bedtime movie-watching and internet surfing device). It’s usually charged to 100% daily or no less than every two days, and used for many hours on end. It’s at least eight years old, probably more, and the battery is still going strong. If I want to watch movies literally all night, it’s good for it. It must have been through at least a couple of thousand charge cycles.
Interesting aside – the battery charge indicator on the display doesn’t agree with “% charge” indicator on the Properties panel when it’s plugged into a computer. The latter is always a few percent less than the former, but does eventually reach 100%.
That’s right, though with the caveat that degradation is worst when the manufacturer has chosen a high charge level (basically, a high battery voltage) and you keep it there for a long time.
Simply charging to 100% is not that bad if you use it right away, thereby bringing down the charge. Hence why charging to 100% on an EV just before a trip is fine–you’ll be driving immediately, so the time spent at 100% is relatively short.
As you said, somewhere in the 40-50% range is best. It’s not worth going crazy about this (batteries are meant to be used), but if you need to store a device unplugged for a while, it’s not a bad idea to discharge it to ~50% first.
Your strategy for using the tablet is the right one. There’s no need to plug it in if it’s still at 80%. Just wait until it’s <50% of whatever’s convenient.
But also, not all charge cycles are equivalent. The range between start point and end point is important. Charging from 80% to 100% puts much less stress on the battery than charging from 10% to 100%, or even 10% to 80%.
The latter question is easy to answer – the phone has battery management software and will certainly not overcharge. I routinely leave my phone to charge overnight, and sometimes even forget about it for a couple of days. (And it’s a Samsung – the brand famous for catching fire – though I think that was just a particular defective model.)
As for the question about the laptop, all I can say is that this is a very common way of using most laptops and I’m not aware of it ever having been harmful. It may be sub-optimal from the standpoint of maximizing battery life, but speaking as someone who owns three laptops representing three major generations from Windows XP to Windows 11, the laptop is likely to be obsolete before the battery is.
Yes–you should basically think of a charge cycle in percentage terms. 20-80% is 60% of a charge cycle. 80-100% is 20% of a charge cycle. Etc.
Still, if you find yourself needing 50% of the battery to do your usual tasks, it’s better to go from 20-70% instead of 50-100% due to the aforementioned issues with high charge levels.
Just wanted to add, in case some folks aren’t aware, that many modern laptops come with integrated batteries. Which is a fancy way of saying that the battery isn’t meant to be replaceable. It can, in fact, be replaced, but it involves opening up the laptop and performing some electronic surgery.
Now some of this is just computer manufacturers trying to save money, but it does tell you something about the likelihood of having to replace the laptop battery before you have to replace the laptop itself.
Interesting. Like Hari Seldon, I left my computer plugged in and used it like a desktop. Occasionally (at intervals of several weeks) I’d get a pop-up that said I should unplug it for a while; I’d do so, then plug it back in several hours later. But up until a couple weeks ago, it always charged up until it said 100% – now it’s only doing 80%. Could the battery life extender have been off since I bought the computer, and then somehow gotten turned on?
My phone goes through cycles – I take it off the charger and put it in my pocket; a few days later I pull it out to check the time and discover that the battery is dead; I put it back on the charger; and then a few days later I remember it and put it back in my pocket so the battery can start discharging again. 
Yes. Companies pull this kind of shit all the time. The downside of always-connected OSes and apps, and an ecosystem that encourages companies to be constantly updating their software.
Thank you.
Based on my experience, a great deal of battery longevity is simply based on luck. Following best practices will probably improve the odds of your battery surviving, but given a set of “identical” batteries, some will last a long time, and some won’t.
I bought 60 identical Dell laptops in October 2019. Of those, a nice round 10% have had the battery completely fail. None failed during the warranty period.
42 of the batteries are made by BYD, and the 18 remaining by LG. 1 of the failed ones is from LG, and the rest from BYD. My eye ball \chi^2 test says neither manufacturer is more likely to fail.
Due to the nature of their use, the batteries all have a low cycle count, but otherwise are generally abused. For a month or two the computers are plugged in constantly, and for the rest of the year they are unplugged and turned off.
They are set to only charge to 80%, which always shows as an indicated 79% when they stop charging.
So typical use is, charge to 80%, hold there, turn off and unplug for 9 months. The very odd thing is that about half of them will be completely drained 9 months later when I take them out of storage, and about half will have 20-50% battery remaining.
That almost suggests to me that some are put away truly turned off-off and others are put away in a sleeping or hibernating state. Or some have slightly different firmware or accessories that do a periodic partial wakeup for whatever reason, resulting in stone dead batteries. While the others that don’t do the wake-ups end up with 50% charge left over.
Or, as you say, it’s just individual manufacturing variation in how much internal leakage current or whatever sloshes around in there in the dark.