Sorry for the confusion, this was a smartlock that used a keypad. No phone integration. Actually, I don't think I've ever seen a smartlock in person that uses a smartphone to unlock, although I've heard they exist.

Anyway the unit in question took 4 AA batteries which needed to be replaced every 6 months or so. The batteries of the lock itself died earlier than expected. Apparently the wifi connection to the front building door was bad and that caused the battery life to drain significantly faster than advertised.