Well you have two solution, the better is to find one psp in cfw and to make a pandora battery without open it.
But if you can't make with a cfw psp you can make at hand, well that easy :

- First open your battery with a knife or a cutter ( I had open my pandora battery with a cutter it's more easy but be careful because if you do that too fast you risk to cut a other chips well take your time !).
After she will be like this : http://i.imgur.com/4vjzH.jpg

- Secondly cut the 19 chips. Like on the picture I have make : http://i.imgur.com/wcbtg.jpg (sorry for the bad quality).

- Thirdly close your batterie and it in your psp, if the green led incandesce automatically you have succesful. If the green led didn't light you can cut the 19 chips again.

- After if you wanna make a normal battery just write with a wood pen on the chips you cut and she will become normal. You can put scootch around your battery for close it.

That all ^^