[Xposed Framework Modules] 65536:
My experiences with Lithium batteries were way different.

I have a 10 year old laptop with its original battery. When I got it, it was about 8 years old and the battery went down from 100% to 0% in just 30 minutes.

Then I disabled the automatic shutdown at 0% battery (via command line; it's not possible in the power options of Windows). This resulted in another 2 hours (!) of run time. I was really surprised about that.

And indeed the battery recalibrated from fully discharging. After I did this a few times, I got about 2,5 hours of run time before the battery level reached 0%, and a few minutes later the laptop turned off because of insufficient voltage - this is like it should be.

When using the DisableCriticalBatteryShutdown module on my Galaxy S4 for the first time, I guess I got an additional 15% out of the battery. And the battery seemed to recalibrate too, giving a noticeably longer run time before reaching 0%.

And as an electrical engineer, I hope to be able to bring some clarity into the question if this module harms the battery:

There are many things Lithium batteries don't like, some are avoidable, some aren't.

- Charging to 100%: Fully charging the battery causes some chemicals to irreversibly react with each other, as a consequence the battery loses some capacity

- Being at maximum charging voltage for long times: Even worse than simply charging to 100%, although most phone users (me included) do this by charging the phone over night

- High temperatures: Not a real issue in phones

- Discharging to its cutoff voltage: Like charging to 100%, this causes the battery to lose some capacity, and this is the only way the addon may slightly harm the battery

- Discharging below 2.5V: This may seriously harm or even destroy the battery, though I have seen Lithium cells discharged to 1 volt and working just fine after recharging. In phones with removable batteries, this is completely impossible because the battery has its own protection circuit which will just turn off the power when the battery voltage fells below like 2.7V.

I assume that phones with fixed batteries have similar protection circutis inside.

- Charging at high currents: This one isn't too well known, and maybe the worst. According to a NASA study of the year 2009, Lithium cells dramatically lose capacity when being charged at 1 C rate. After 200 cycles with 1 C charge and discharge rate, only 1.2Ah of the original 2.8Ah capacity was left!

Link to the study: https://batteryworkshop.msfc.nasa.gov/presentations/Perf_Safe_Test_Panasonic_Li-Ion_NCR_18650_Cells_JRead.pdf

Maybe the batteries improved since 2009, but since I read this I use just a 500mA charger for charging my Galaxy S4 overnight, and use the 2.4A charger only when I really need fast charging.

So, for optimum care, one should always keep the battery between 20% and 80%, and avoid using fast chargers.

On the other hand, there are lots of Li batteries in not so smart applications like cordless drills, where they are simply discharged down to 2.5V/cell, and there batteries also last for quite a while. I see no problem in occasionally discharging a phone battery to the point where the phone just dies.