[pmontra]

You can hack that on any system that lets you read the battery status. All you need is a smart plug. You power the laptop from the smart plug. You switch off the plug when the battery is at 80% and you switch it on again when it's at 20%.

[jraph]

This has a major drawback: it's constantly using battery cycles.

Does a computer with charging throttle like described draw power from battery too, or does it use the power from the plug directly?

[pmontra]

I know that there are laptops that bypass the battery if plugged into the mains but I think that the answer varies case by case.

A battery level check every five minutes should be more than enough, not a big draw from the battery for a laptop.