What to do with a Pandora battery if your psp is bricked

your PSP usually boots up from the Flash 0
what the Pandora battery does is send a fake serial number "0xFFFFFF" to the PSP
this serial number makes the PSP boot up from the MEMORY STICK instead of the Flash 0

so you need to completely format a memory stick (erase all files completely)
and then put "magic memory stick" files on the formatted memory stick
download magic memory stick installer then put in your new magic memory stick, THEN put in the Pandora battery

from here you can unbrick safely :)