This mostly never happens. I've used fingerprint locks where the battery lasts easily for a year (that's with 5-6 accesses per day). Without getting into the d

This mostly never happens. I've used fingerprint locks where the battery lasts easily for a year (that's with 5-6 accesses per day). Without getting into the discussion of the security factor of biometrics, the working mechanism of the lock itself is such that when it detects a success, a small servo engages some sort of a gear which enables you to complete the mechanical circuit (so to say) when you push the door lever down and move the physical lock with human effort. This means that the battery is never constantly used, only when the actual sensor is active. Even if it were dead, there exists a manual key override. Also, (I've tested this personally), the factor of safety is quite good in that, the lock starts beeping "LOW BAT" a good 3-4 weeks before the battery is completely drained. Also, (Another one) it doesn't leak information about low battery until there's a successful entry, so an evil attacker can sit near your house activating the sensor all day and he won't know his progress in draining the locks' battery.