about batteries in a safe keypad
you do realize they come with KEYS? Good old fashioned metal keys, never fail battery or not. The one I posted has a plastic cover over the middle, that hides a real old fashioned lock that uses a KEY.
again, nothing will keep out a determined person, who came to get in a safe, no matter the cost of it. I worked in a bank vault manufacturer for a few years actually building bank vaults. We only had to pass a minimum test of a 18"x18" hole in under 45 minutes to get a UL certification. As they had a guy that could actually get through a 18x18 hole and be INSIDE the vault. And we were building embassy vaults, that were installed around the world. Some filled with concrete and re-bar, with concrete having added steel fiber to it for burst pressures against explosives, some with just old fashioned wood panels and expanded metal(think bbq grill) between the wood panels, but again, for a particular threat, as wood wont cut with a torch and the metal to foul saw blades. Nothing is perfect given infinite time and resources you will gain entry to any vault.
Locks are for honest people. A lock keeps you honest. A thief, will only see a obstacle to over come.