Here is a Cool Homemade Tester for 24 Volt Locks
Have you ever been in a situation where you don’t have a power supply but need to test a lock?
This portable power supply simply consists of three 9VDC batteries connected in series to create 27VDC. I bought a 9VDC battery harness at a local electronics store and cut it in half to create a separate positive and negative leg and soldered alligator clips to each one. (If you wish to go “green” you can also use rechargeable 9V batteries.) Then I just taped the three batteries together and viola, my portable power supply for 24 volt locks was ready to go.
If it’s going to be kept in a tool box or tool bag I suggest fusing it to make it safer. You can put a 2 amp fuse holder in line with the positive leg to protect you and the hardware if there are any shorts in the lock, current transfer hinge or wire.
I guarantee once you use this handy little gadget, you will keep one in your tool box all the time.