Same problem, the battery was working perfectly before updating, now it’s just showing service recommended warning and diagnostics is not showing any problem, this is a serious bug with battery on Big Sur.
qamarulzaman00
Users receive reputation points by contributing quality content to the forums.
Posts include post and replies published on the forums.
Post authors can mark replies as Accepted to indicate successful solutions.
Apple Developer Forums admins can mark replies as Apple Recommended to indicate an approved solution