[Feature Request] Add option to limit battery charging to extend battery life span on Steam Deck

Your system information

Steam client version: 1671675017
SteamOS version: 3.4
Opted into Steam client beta?: No
Opted into SteamOS beta?: No
Have you checked for updates in Settings > System?: Yes

Overview:

Quite some mobile devices these days have an option to limit battery charging. E.g. on the Samsung Galaxy mobile phone the battery does not exceed charging beyond 85% if the option is turned on.

Why:

Charging the battery to 100% shortens the life span of batteries on the Steam Deck. With an option everyone can choose between longer battery time and longer battery life span. Especially when gaming and working with the Steam deck (yes I do use it for working a lot as well) connected to a USB C monitor it will always charge too 100%.

If considered to be implemented:

consider whether to show 100% when battery is fully charged and option is turned on or the true 85% only. From a customer point the true value of 85% might be less confusing if option is turned on.
add a flag/info in logs somewhere if option is enabled in case someone contacts technical support.
option should be off by default.
should work both in SteamOS as well as desktop mode.

This feature is a MUST HAVE for portable devices. I've even had a look into the Steam Deck bios if there is a hidden option to specify this charging limit.

From what I have observed, currently a discharge down to 97 % is allowed and then it is completely charged to 100 %. This is the WORST possible way because the last about 6 % is the most stressful and slowest charging for lithium-ion batteries. Side-note: It also should be avoided to discharge them below 20 %. The optimal storage is with 40 % and cold.

The best implementation I've seen yet on one of my devices is that it is possible to specify a percentage corridor for discharge-charge.

So my suggestion for GUI implementation is that the user gets a slider with an adjustable lower and and upper mark. There he can specify the lower limit down to which discharging is allowed and the upper limit up to which charging is allowed. If one slider is not possible, there could be two sliders which are interconnected (validation lower <= upper).

ValveSoftware / SteamOS