[Android Apps and Games] Infy_AsiX:
For devices still missing a charge stop file I looked through the directory for other files that looked related. I found a few files that look related to limiting voltage but are all write only. I’m on a Sony Z3C stock M rom where Sony introduced a 4.25V limit from 4.35V setting in the firmware. These files seem related so are worth checking. Try one by one changing their permission, writing, resetting permission, restarting, checking if value is kept and testing. Of course have a nandroid backup ready in case. The way Sony's change shows percentage as 100% in OS but voltage is now lower. For example turning off the phone and charging or in TWRP shows a percentage around 10% lower.

/sys/class/power_supply/battery/voltage_max_design 425000
/sys/class/power_supply/battery/voltage_min_design 420000 (I’m not sure why min is called 4200, putting here for possible relation. Looks to possibly be the float voltage)
/sys/class/power_supply/battery/voltage_min 420000 (there’s also this, don’t know why there’s the two similar)
/sys/class/power_supply/battery/device/vdd_max 4250

That drop to 4.25V seems to be shown as 15% less total capacity by these files.

/sys/class/power_supply/battery/charge_full_design 2660
/sys/class/power_supply/battery/charge_full 2315 (MaH it seems)

Right. Higher current increases voltage further. That charge voltage is the important limit to target as it's higher.

I’ve taken a related interest to batteries as required while trying to form a good custom solution to my initial charging rate problems and capacity limit. I’ve been reading and have still yet to read some more about it all. What I have formed is that Tasker project I linked before. I renamed all the profiles and tasks with a number so they can be sorted into a legible sense as Tasker's import seems to ignore any previous set sort. I’ve since added low temp limits and a shortcut secondary mode of lower set custom limit values maxed at 75% instead of 90% for when leaving the device plugged for an extended period for example like when staying at home all day. However that’s only viable if you can always carry a powerbank or have a spare removable battery to swap in, in case of a plan change and needing to be on the go with power. I’ve modded my Z3C to have it’s battery swappable by cutting out some mid-frame as well typically carrying powerbanks.

Maybe. However it only applies to devices with both files functioning, I don’t know how relevant it is. I’m pretty sure all the percentages will need to be dropped 10% or so due to my Z3C Sony firmware lowered voltage difference still. I could get a USB power meter as they don’t cost much, to see the voltage and current when the screen is off. I can only see a lowered current+voltage caused by power draw from the screen, so my custom rates are lowered accordingly by guess. It won’t be much of a difference but it’s there and not exact.

It’s only a Tasker project with a rather basic setup. If someone has development knowledge with interest in battery performance, this can be done even better and improved. For example Tasker can monitor battery percent but not voltage without further tasks creating inefficiency. If there’s anyone with electrical engineering expertise they could understand the CCCV parameters that can be found in /sys/class/power_supply/bms/device/.

I guess I should mention that overriding charging rates is risky. Unlike other hardware failures, a battery failure can be violent. Extremes should still shutdown by various other software and hardware protection fail safes. If it was very risky manufacturers wouldn’t allow it even through root, like what if there’s a malicious hack designed to damage batteries. Heck I believe the way charging is currently set up default in software and hardware by manufacturers themselves nowadays is risky and poor. Let’s think about constant new faster charging protocols and hardware specifications. Slimmer designs, hotter thermal physical dimensions and performance constraints. Culminating to a major double recall from the Note 7 case that was caused by initially by physical design fault and manufacturing then the second time just manufacturing. I don’t like aggressive damaging, short term planned obsolescence but it's not just in hardware. In my personal case I’m interested in longevity and value. There’s simply no manufacturer on that level as long as charging isn’t limited at least 4.1-4.2V. That’s a good enough reason to override the standard method with a smarter alternative.