I have lost the keys for power devil electronic safe model PDW5500 battery is flat

CALL THEM
there is no other way
if there was , the safe is a useless toy

Oxy-acetylene.

You're going to have to cut your way into it, I'm afraid.

If you leave it for a week or so, the batteries MAY just have enough charge to open the safe once more.

Take apart the unit if it appears to have an internal battery with no access hatch and replace it with a new one that is compatible. If you cannot find a replacement, you can always build your own battery pack.

Use the same battery type and voltage and solder them together if required. Make it clean with no potential for any short circuits. Do not mix old batteries with new ones. If you can find higher capacity batteries than what the vaccum came with, those will be fine to use as well. Just make sure they are rated at the same voltage level so that charging them wont require any modifications. Don't burn yourself!

Most middle schoolers and highschoolers can help you with this if you have any younger folks around you.

check the wires to the plug on the 9 v battery or clean the terminals

if the key is broken -- then the best thing to do is to take the broken key down to your local locksmith shop and have them duplicate the key from the two pieces. if you cannot get the broken piece out of the lock then take the whole safe down to your local locksmith shop and have them dig it out and copy the key for you. if the safe is bolted to the floor and you cant move it and you cant get the broken piece out of the lock then you will need to have the locksmith come out to your house and extract the key and duplicate it for you and then you will be able to get into the safe using the new key and replace the battery.

c...

I have a micromart electronic safe and i lost the key. The key number at the back of the plate states 024. Can you tell me where to get such key please?

1) look again for the key
2) call a lock smith
3) drill the lock
these safes arent expensive , cheaper to drill the lock and replace that a lock smith , but get a quote

i got the same problem i lost my key and cant open now
any idea what to do

This manual will answer both of your questions.
http://www.sentrysafe.com/pdfs/OwnersManuals/501664.pdf