Charge battery only up to 80% option
To improve battery lifetime you could add an option to charge it only up to 80%.
I'm not sure, but I assume most device manufacturers actually lie about your battery life to improve battery life passively. So if the most efficient percentage to charge is 80%, the percentage would be scaled so that at 80% it shows 100%.
Then it will just trinkle charge at 80% which wouldn't be much better.