How to lock and unlock the Nest × Yale Lock if the battery is drained. If you need, you can use a 9 Volt battery to temporarily charge the lock, so you can enter your passcode on the lock's keypad to lock or unlock it.
How do I check my Yale lock battery?
There is no way to check the battery level for your Yale devices in the Yale Access App, but you will be notified when the batteries need to be replaced. Once a lock's batteries reach 25% capacity, a low-battery notification appears on your phone's unlock screen.