I've never hard modded my psp battery and i wouldn't reccomend but a video on how to hard mod a fat psp battery can be found at youtube.com/watch?v=yvOnbQAVq30
also to make a magic memory stick is very easy, just go to pspmod.com/forums/psp-software-guides/28540-release-catb50-teams-magic-memory-stick-creator-v2-0-full-lite.html and download either the full or lite version
If you don't want to hard mod your battery you can always buy a datel tool battery from amazon.co.uk/Datel-Max-Power-Tool-Battery/dp/B000W4HSHC that's what i done
