With the newest Nuki iOS App Beta (APP UPDATE: Nuki iOS App 2.6.8-Beta) in the Battery report (tap 7 times on the info text below the “Automatically” switch to get it) the battery in % value is also shown.
@PharaDos In the Android App the critical value in the (hidden) battery report is shown as “yes” with the new Smart Lock Beta firmware due to a bug which will be fixed in one of the next updates. Please ignore it and only check the “official” Battery state on top when testing for now.