The Pandora battery is not a battery but a device which can be used to re-install corrupted system files for your PSP. It is used for what is termed a "bricked" psp (ie a psp that won't work and is as much use as a brick). Using the provided instructions and the memory card (which holds the new system files), it takes about 5 mins to fix a completely useless psp (though you will need to charge the Pandora "battery" first which takes a while). I cannot recommend this product highly enough. It is really easy to use and the instructions are very clear, and most importantly it can save you the cost of a new or reconditioned psp which is likely to set you back at least £80 (reconditioned) or £130 (new).
Note it isn't going to fix mechanical failure though you can find 3rd parties on the internet to replace most mechanical bits (broken screen, damage disc mechanism or cracked case) but it is pretty much bomb-proof at repairing the software (if it doesn't work or you make a mistake - just start again).
How do I know if my psp is bricked or mechanically broken? The indication of a bricked psp is when you switch the power on, the green light will come on for about 10secs then go out again but you will not see or hear another other response from it.
What size card do I need? If you already have a reasonable sized MS Pro Duo card for your PSP then get the smallest available one (the cheapest) - 512KB - which is what I would recommend because you can keep it safe with the recovery files in case it bricks again. If, however, you don't have a decent sized one already for your files, you might want to get a larger one to use after you have unbricked the device for storing game files, music or video (instruction tell you how to reformat it).
Folks it is really easy, saves a lot of money and satisfying to fix - it is almost worth bricking a psp just to do it!
No I don't work for the company, I just think it is a great product and an excellent service.