Why didn’t anyone tell me there is a battery in my safe lock?

More than 90% of safe locks use battery power instead of a power cord plugged into a wall. Safe locks were developed with batteries so safe technicians could easily replace a traditional dial lock with an electronic lock without compromising the integrity of the safe by drilling a hole to run the power cord.read more
http://www.ssnw.co/blog/why-didn%E2%80%99t-anyone-tell-me-there-battery-my-safe-lock