Batteries are dead so I can't open it and I have the key

On most safes you can get to the batteries on the outside. Look for a slide out panel on the bottom of the push buttons or dial. The safe should store your code in a permanent memory even when the batteries die. Replace the batteries and you should be able to use your old code to get into the safe. If for some reason this doesn't work, there should have been a default code in the literature that came with the safe. If you can't find that then contact the manufacturer and give them the serial number of the safe and they should be able to give you the default code.

Check your manual for such a situation. If nada contact support at the manufacturer web site for assistance with this dilemma. Sure you are not the only one who has experienced this so..........