If your battery becomes low or weak, the safe locking/unlocking mechanism should give you repeated beeping during opening procedures. If this happens, you just replace the battery with either an Energizer or Duracell brand battery with an expiration date of at least 5 years in the future. Please use a regular 9V alkaline battery, not a lithium or rechargeable.  Since all batteries are not created equal and they are mass produced, sometimes you can get a “weak” one right out of a brand new packageIf your safe locking mechanism shows any behavior out of the ordinary, we would recommend purchasing 3 new batteries just to insure you get at least one “strong” one. Try each new battery and if you get the same exact symptom with each new battery, then that will eliminate the power source as the issue. This fixes most lock issues.