It has been recommended by many that Li-Ion batteries be charged up to only 85% to extend battery life. Tesla suggests this for their cars. Galaxy S10 phone has this option available. What about also for the Galaxy Watch 6 Classic?
You may find the following copy & paste from an electrical engineer that addressed the charging issue for phones in detail based on actual knowledge. I've been following it for some time. Its applicability to watches is unknown but it's the same battery chemistry.
Power Electrical Engineer (1980–present)Updated Aug 3
The question of how to maximize a phone battery's life comes up so often here, and the stock answers from non-experts who Google up the topic and then either misinterpret facts or regurgitate nonsense, is just unbelievable.
I am an engineer at a company that builds battery-based military-grade uninterruptible power supplies and converters. At the time of this writing, my current project is the design of the electronics for a 24-channel battery pack charger for all of our lead-acid and lithium-iron-phosphate battery packs. I have been here doing this sort of work for over 12 years. I KNOW a thing or two about batteries, because I have decades of firsthand knowledge about them. And let me tell you that there is really only one practical way to get half a decade or more of life out of your battery, but first let me tell you what is nonsense:
1- Don't leave you phone on charger all night - GARBAGE! First off, understand that the thing that plugs into the wall that has a cable that you plug into your phone is not really a battery charger, but is actually a power supply for the charger built into you phone, unless you have a weird phone. Now, there are lots of phone out there, and I like to think that most if not all include correctly-designed and functioning charging circuitry that will perform the simple task of not exceeding around 4.1V top charge voltage, which varies slightly among various lithium chemistries. Where you might get **bleep** is if you buy a phone from a manufacturer who has succumbed to the marketing department's demand for the absolute-max battery runtime and thus programs the charger to output the absolute max voltage that the battery can take when new. This will shorten the life of the battery, and do so needlessly, because that last 1-3% of capacity just isn't worth it in terms of its effect on reducing battery life. So you either have a correctly-programmed internal charger or don't, but you don't know. Now, you COULD babysit your charger and unplug it when it reaches 97%, thinking that is the safest and best thing to do. But the instant that you unplug it, you start another charge cycle, and you only have so many of those available.
2- Plug in at 40%/50%/whatever and unplug at 60%/70%/whatever. GARBAGE! Even if you are willing and able to stare at your phone charger for a living and plug it in at 45% then unplug at 55%, you still have used up 10% of a battery cycle. And if you're like me, you might have to do that several times a day, plus stay up late at night to babysit it. Ridiculous.
3- Don't use your phone when on charger - GARBAGE! When on charger, your external charger supply is the power supply for your phone, relieving load on your battery. Try using Google maps in your car or use it for a hotspot for longer than a couple of hours without it being on charger - there goes one more of your limited battery cycles.
4- Don't charge frequently/ only charge above 20%/30%/whatever - GARBAGE! And the following is why:
To get more life out of your battery than you will keep your phone for, have a charger at home, at work, and in your car, and endeavor to keep your phone on one of them at 100% state-of-charge, 100% of the time. Doing so results in ZERO charge cycles. Granted, it would be nice if manufacturers gave you an option for being able to adopt that strategy with a setting to only charge to maybe 80%. That might result in a 10-year battery, though I am not convinced of even that. So instead, I, a power electronics engineer among who's specialty is batteries, try to keep my phone on charger 100% of the time. And as a result, my 7 year-old Note 5, which after all these years now has a worn-out camera focuser motor, has a battery that still has around half of its life left in it. Do you intend to keep you current phone for 7 years?
I suggest you be smart and listen to a real expert on this topic rather than all these random folks who believe the first thing Google pops up with or whatever popular regurgitation is running rampant. The only thing I would add is to avoid high temperatures while on charger, but even then, I doubt that there is a single phone out there that doesn't includes a temperature monitor and has a charger that will limit battery charging based on temperature, since heat is a very bad thing while charging. Don't charge your phone sitting on a pillow or in full sun on the dashboard of your car. Common sense stuff.
EDIT July 2023: I will add something about a new development - my last update (May 2023) to my 18-month old Zfold3 includes the ability to limit charging to 85%. I am using it. Charging turns on at 83% and off at 85%. I will still leave it on charger as much as possible, virtually 24/7. I suspect there is a good chance that this is a slight improvement over the 100% 24–7 strategy, and am using it. Time will tell.
I thought the key to what the electrical engineer said was that a phone would be running on AC and not the battery when fully charged. I checked that with two online sources and both confirmed that it was correct.
