ok first off you will need the following items.
1.a psp slim/phat psp
2.a battery( im showing the one that comes with the psp)
3.a knife or something to open the battery and remove the chip
1. the first step is opening the battery, now start on the bottom edge. one u cut that start moving twords the side and keep sawing that thing open. be carefull if u cut to deep you might touch the mother board. which means. your dust. ok once you open your battery it should look like one of these pictures below.(ignore the arrows).
2.ok now that you have it opened remove the pins. (look at pictures and read).
3.once you have them FULLY removed put your battery back together and tape it up a little bit. and your done.
SLIM:remove the pin on the right side right above the right arrow.MAKE SURE ITS FULLY REMOVED!!!