Depending on the motherboard on your PSP, it might not be crackable at all. If it's a PSP 3000 or a relatively recently manufactured 2000, you're SoL.
If it's a 1000 or an older 2000, then yeah, you can crack your PSP with a Pandora battery (either purchased independently or created using another homebrewed PSP). No hardware mod is necessary, though if you don't want to purchase a special battery and have no access to another cracked PSP to make one, some batteries can be hard-modded to turn them into Pandora-ready batts, as an option.