HI AGAIN!
The battery number of the SE50 is CR 2032. You can find it in Radio Shack, Wall Mart or in any foto lab.
Replace the battery can cause lost of the user memory, so back up first. First, buy the battery, then unpluged the A/C power supply, open the FX, find the battery (it's like a .25 cents coin size) You can put out the battery whit your hand and replace it fast. (maybe you can save your patches).
you can do this whit the power on, but it's risky and this will help you save your patches.
Good luck y adios amigo!!!
kunny