Why voltage and not percentage?
Because battery charging is a rubberband effect. If the charging controller applies a higher voltage, it will charge faster and go to a higher percentage.
Unfortunately, some charging controllers such as that of the Galaxy Note 4 go dangerously high (4.39V), which resulted in my replacement battery being inflated.
Limiting the percentage to something like 80% would not prevent battery inflation because shortly before charging stops at 80%, the voltage would still be at 4.39V to achieve the highest possible charging speed.
Limiting the charging speed (charging current) is possible by changing the value in the "siop_level" file (0-100), at least on Samsung devices, but that is also not so useful because a low speed at a high percentage can still exceed 4.3 V, and a low value in "siop_level" would also limit the current at low percentages even though a high current is possible at low percentages without exceeding 4.3V.
A voltage limit of 4.30V would still allow fast charging from 0% to roughly half, and above that it doesn't matter much anyway because fast charging is neede most when you are low on power.
All a voltage limit of 4.30V would do is slightly slowing down charging while the battery is already charged more than half, and reduce the used battery capacity by just a few percents, but it would significantly extend the battery life expectancy.
How to limit the battery to a specific voltage rather than a percentage or a speed?
Is there a way to do it for all manufacturers, or is it manufacturer-dependent? The closest possible thing for Samsung devices would be a script that lowers siop_level whenever the battery exceeds 4.3V, but siop_level apparently only exists on Samsung devices, so it would not work with other manufacturers.
I hope there is a file that specifically controls battery voltage, not just speed or percentage.
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