Maybe this can done via sysfs. Charge_control_limit and charge_type look intetesting.
https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-class-power
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After a few more days of tests, all I can say is that sometimes it restarts charging upon every USB cable reconnection, while other times it just won’t restart charging (no matter how many times I disconnect and reconnect the cable) until I stop and restart the Battery Buddy service (of course as long as battery level is above the lower limit).
I haven’t yet discovered if it is purely random (i.e. erratic) behavior or if it actually depends on something. Something tells me (but I haven’t had the time to confirm it) that it depends on whether charging has reached the upper limit and was stopped because of that (in such case it won’t restart upon cable dis- and re-connection as long as the battery level is above the lower limit) or if it wasn’t the case (i.e. the upper limit hasn’t been reached yet - in such case removing and reconnecting the cable always restarts charging). It will take some more charging cycles (and the time to play with it) to further observe it.
Not really to percentages but to VOLTAGES that the cell has when it is either nearly fully charged or discharged. Voltages of either ~4.2 Volts (upper limit) or close to 2.4 Volts (lower limit) are simply not healthy for lithium cells chemistry, especially if preserved for longer periods of time (e.g. fully charged and then not used).
At high too. Storing fully charged cells degrades their capacity. Good Li-Ion / Li-Poly chargers have a “Storage” charging mode, charging the cells to 3.8 Volts.
Not voltage but current (that’s what affects the charging “speed”). In Battery Buddy there is a setting to limit the max charging current. And it does work very well. I do use it quite often to slow down charging so that it finishes shortly before I wake up rather than fully charge in the middle of the night and then discharges by 5% or so before I wake up.
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These are about currents (i.e. Ampere), not voltage.
Some engineer told me it would be be beneficial to slightly reduce the voltage, but I guess it’s something I can live without, because see next reply.
Thanks for the additional clarification.
I am meanwhile happy to significantly lower the charging current through BB - iirc 500mA is what a computer’s USB port provides?
We’ll see how that goes -so far it still seems fast enough.
Off topic/Rant:
I have since learned so much about charging Li-ion batteries that I’m slightly angry at Lenovo/ThinkPad because of how badly they manage charging for their dual batteries.
It’s basically impossible to not wear them out because the machine doesn’t start pulling current from the other battery before the first is very low.