The digital lock might need 4 AA batteries. Some models requires 6 or 8 AA batteries. You can still unlock the door with the power bank ( some models has got 9V battery ) as emergency power supply. Once the door is unlock, please replace the batteries at once to make sure the digital door lock work properly. You can contact me for any questions for the digital door lock with fingerprint access. I am glad to help. Below is our new digital door lock which will be launched in the market soon. You will be greatly appreciated if you can give me your advice for our product.