Nuki Opener, battery and usb operation

Maybe it’s just me, then I dind’t understand how to know if the Opener unit is operated by the battery or the usb 5V connection when both the battery and the 5V usb are operated in the same time. In the app I just can see the option to ignore battery warnings if Opener is operated by usb, so how can I understand which of the two is operated my unit in that moment? I could take off the battery and I also will do that, then my Opener is firmly installed on the wall and even if I follow carefully the instruction to open it to remove the battery, it seems really difficult to me without eradicating the whole unit from the wall, it is too firmly pressed and if I push the unit do not unblock the battery socket. My request for a future version of the Nuki app is to have clearly stated if the Opener is operated in 5V or on battery. For now I need help to understand this and to unblock the socket of the Opener to remove battery. Thank in advance for any help, if any.

I reply to myself. After a month or so of use with Opener operated by USB I can say I didn’t was dissappointed with operating on battery, then using USB with a simple, old apple charger (1A) makes Opener like if it is on steroids. Battery IMHO are unrialable especially becose you can never see which is the level of charge, the App indicator in my experience is totally unreliable (the same for me is applicable to SmartLock too). After some months of Opener use with the same battery reported by Nuki App as still quietly charged, it started to miss some ring to open. With USB charger never happened again and I can also put the Open TIme from the default 3 sec to 1 sec and it works perfectly fine with less noise. So if some work as to be done over the Opener is battery reliability.