The phone will still work as a key even if it's out of power [0]. Obviously it won't work if your battery has been completely dead for weeks, but as long as you

The phone will still work as a key even if it's out of power [0]. Obviously it won't work if your battery has been completely dead for weeks, but as long as your phone can show the "out of battery" screen, it can still do NFC stuff. [0]: https://support.apple.com/guide/security/express-cards-with-power-reserve-sec90cd29d1f/web https://support.apple.com/guide/security/express-cards-with-...