My sony psp is not working! may someone explain what it is?

[hotlife]

i charged it till it became a full battery and it DID charge cause the light was on. :/. but then i tried to turn it on and it would not work. TT^TT... then when i plugged it in the wall and turned it on it worked perfectly fine when i unplugged it for awhile. but now that i left it alone for just a few hours after i turned it off, it refuses to turn on UNLESS it is plugged. any ideas on the problem?

[irishbluestaffy]

u need a new battery m8