I'm not going to sit here and argue that the belief itself exists as it's obvious that it does. Lots of people believe a lot of things, to argue otherwise is nonsensical. I've argued against this stuff myself before so I'm not going to take your word for it that it doesn't exist.

What the source I cited does for sure show is that NMC batteries (used in phones) do in fact last for about 300 cycles to 70% if you discharge 100% every time, not your 500 cycles to 80% claim.

Table 6 also shows that the figure I cited as closest to what I'm arguing for (which is 60-10%) 75-25%, had 88% capacity at 5000 cycles as opposed to the 80% for 100-40, with the line definitely trending much more heavily down the Y axis than the 75-25. By 9000 cycles, 75-25% would have 84% capacity while 100-40 would have 69% (nice) 100-25% would have 62% proving that the maximum you allow your battery to charge is truly the main deciding factor here. The depth of discharge for 100-25 is 75, 100-40 is 60, 100-50 is 50 and 75-25 is 50. So comparing apples to apples, the 100-50 has about 74% capacity remaining while the 75-25 range has 84%, a 10% capacity difference over 9000 cycles which is pretty incredible. It proves beyond a doubt that the lower discharge of 25% does not negatively effect the battery nearly as much as how HIGH you charge it does. I'm insanely confident that my 60-10 I use for my own phone is more efficient than the 75-25 they use in table 6, and likely even more efficient than the 75-65 even though I'm able to use 50% of my batteries capacity as opposed to 10%.

As for the extra protection phones have.. https://en.wikipedia.org/wiki/Cutoff_voltage which cites http://www.ibt-power.com/Battery_packs/Li_Ion/Lithium_ion_tech.html as it's source. This shows a cutoff of 3v, although it also says manufacturers set this limit themselves which is kind of obvious. I doubt they set the limit just above what kills the phone, otherwise we'd hear of phones being replaced every few months instead of every 2 years as normal. I also never did claim phones have extra protection, just that they have a BMS that protects them from full discharges. Again with the strawman arguments...

I'm not sure if you're intentionally misreading everything I've posted or not, but I never said that discharging your battery causes it to explode. Table 6, the third best result was discharging from 75%-25%, which was the lowest discharge they bothered to test. The very worst was 100%-25%, and the second worst was 100%-40% and even 85-25% performed much worse. The only results with better performance were 75-45 and 75-65, both of which are basically impossible to maintain if you have a real job where you can't just sit there and stare at your phone battery the whole time.

However they didn't test the range I've been testing for the past year, and the results have been very very good between 60-15%. I Haven't lost any capacity at all as far as I can tell, and it's counting each charge in this range as being about 0.02 cycles but we'll see how this goes during the next few years. At minimum I'm expecting to stay above 75% capacity for 4 years, but if it drags out to 8 I'm not going to be crying about it.

Just so we're clear, in the first post in this chain I did say this: Discharging the battery entirely can be bad, however phone batteries are super well protected against this type of damage and often stop battery draw well before the battery actually loses all charge.

So you're kind of arguing against a strawman anyways. You can pretty safely discharge your battery well below the 40% level and still expect amazing longevity, you're really making the very most gains in your battery by not charging to 100%. The "Don't discharge below this level" gang is talking about miniscule battery life gains, and here I am trying to promote massive multi-year gains.

It's not something that all lithium ion batteries have, and if you used them in something other than phones you'd be painfully aware of how fun it is to install your own PCM which I've done for my motorcycle and several RC cars and Airsoft guns. Replacing batteries often is expensive.

I never said the PCM added lifespan, but what it does do is dispel this myth that it's catastrophically damaging to your phone battery to discharge it to 0%. It's not. Your phone turns off at 10% capacity at the very least (no matter what the indicator on the phone says), otherwise phone fires would be an insanely common occurrence. I don't know a single person who hasn't had their phone die at least once with obviously no issues.

Actually getting a lithium ion battery to 0v is very bad cuz it's dead, but unless you're working with the battery completely stripped of all protections and software it will never reach this point.

(Table 2 in my link shows that discharging an NMC battery, the ones used in phones by 100% did in fact cause it to go to 70% capacity by 300 cycles) That 500 cycles to 80% ignores every other kind of battery depleting issue, like the fact that TIME also degrades your battery among several others.. But yeah, all cellphone cells have a PCM that blocks them from going below the minimum voltage by quite a bit.

This is also incorrect. All modern phone batteries have a PCM (Actually they use a BMS, a more robust sysem than PCM. I use PCM's in other equipment myself so I was biased to this type of battery protection) so they CANNOT be fully discharged no matter how hard you try. You can bring your phone battery to 1% or dead and the phone actually still has plenty of juice left, the PCM just keeps that charge so the phone cant brick the battery. The best practice is to keep your phone battery between 15-60%, you'll get close to 900% charging efficiency vs. charging to 100% (which is 100% efficiency) or charging to 85% (200% efficient) at least according to the battery tracking software accubattery I've been using for the past year.

I completely agree with you. While it's technically correct advice that doesn't mean it isn't totally useless. When I'm in the middle of a 10 hour shift I can't just go take a few hours to recharge lol so it's not practical advice at all. You start resting on the clock and you'll be looking for a new job real fast.

Just got the Accubattery app a year ago for S22+, phone battery started at 95% of spec (apparently it's normal for phones to have up to 10% less capacity than they're specced for, I did NOT know this prior to actually testing) and after 1 year it's still at 95%. The real trick is to charge to 60% max, but you can discharge as low as you want. Disable fast charging, it causes heavy wear. Charging between 80-100% causes heavy wear. Discharging the battery entirely can be bad, however phone batteries are super well protected against this type of damage and often stop battery draw well before the battery actually loses all charge.

Have gone through ~80 cycles in total, or what the battery considers to be 80 full charges/discharges. At about 300 cycles your battery should be at about 75% battery capacity, so instead of being there at 2 years which is pretty typical I should be able to keep the phone in amazing shape battery-wise for 4 years. Every phone I've ever owned got pretty weak after 2 years so learning all this was a huge game-changer.

EDIT: All of the information I used is what I've gathered myself from using the Accubattery app to track my own phones discharge rate and capacity, and this website for the 300-500 cycle figure that manufacturers themselves cite. https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries

EDIT 2: I should've been more clear what I'm arguing for. Charging between 80-40% is worse for your battery than charging between 60-10%, even though you net +10% usable capacity with the second. So if you really want to maximize battery life, go to the lowest maximum charge you're comfortable with (60% is what I use) and go as low as you're comfortable with, most people are comfortable with between 10-20% before charging.