"Your comment kind of implies that 80% charge is irrelevant" I don't mean to merely imply that only charging up to 80% charge is (essentially) irrelevant. I me

"Your comment kind of implies that 80% charge is irrelevant" I don't mean to merely imply that only charging up to 80% charge is (essentially) irrelevant. I mean to state that it is. What actually happens at around 80% is that the charging regime changes. It's nothing to do with "making the battery age less". A lithium battery has two charging regimes: Constant Current and Constant Voltage. Up to about 80% a lithium battery is charged with constant current => charge speed is limited by the maximum output current of the charger => bigger charger faster charger speed => happy customer. Above ~80% you switch to Constant Voltage. Charger now charges at a constant voltage and the charge current drops off following a log curve. The closer you get to 100% the lower the current => battery charges slower and slower the closer you get to 100%. This is a simple matter of physics and is the antithesis to "Fast Charging" which is why fast charging always talks about charging up to 80%. "but the things you mention PLUS the discharge depth or how full you charge also affect the equation from what I gather." Yes, depth of discharge (DoD) does affect battery ageing. But there's also a dozen other factors as well. Some affect the battery life more than DoD. So yeah don't waste your life trying to compile custom kernels or whatever to only charge to 80% :) Just help the battery keep cool with what I posted earlier. It's all you can do. Worry about other things in life :)