Quite a few people have noticed some unusual behavior on their Nintendo Switch systems- where, specifically, their battery never seems to hold any charge. The indicator always shows it being discharged, although apparently the system can go on for 2-3 hours even on no charge after that.
The reason this happens is because the battery is functioning fine, but the battery display indicator software has lost calibration with it. And now, Nintendo Switch update 3.0.1, released last night, addresses this issue- though it does require the user to charge a battery to the fullest and then run it down multiple times before the software synchronizes with the battery entirely.
That apart, the system also enhances system stability, because of course it does. Your Switch should have downloaded the update automatically if you left it on sleep mode (though you do have to manually confirm its installation). If not, you can delve into system settings and initiate an update for yourself.