If the battery is below 20%, the lock will emit 2 sets of 2 short beeps with pulsing Red LED. 

If the battery is below 10%, the lock will emit 4 sets of 2 short beeps with pulsing Red LED. Please change your batteries as soon as possible when it is low in battery.

You can also check the status of your battery via the app.

Note: If the lock's battery power is completely out, it may not respond at all. In this case, use a 9V battery to jumpstart the lock.