its an external battery for the PSP
as the PSP uses the same power plug as the Z and the same voltages you can use them for extra battery life for your Z, i have 2x 6000maH battery packs that work fine, each pack gives me an aditianol 3x of the normal battery meaning that i can run the z for 16 hours straight off of one battery or 28 hours off both.
to work out runnig time of any battery pack take the capacity in maH (miliamp hours) and divide that by 2000, add one and the multpily by 4 ((maH/2000) + 1) /4. that gives a rough estimite as to the running time of the Z with a given battery pack
also if you can grab a PSP sync and charge data cable, it has a normal USB-A plug on one end and a mini B plug and Z charging plug on the other. its a real life saver on the road
