Battery Icon disappeared, HELP

[kachun135]

I am a complete noob to this whole psp thing....i got my psp last year and its a fat one. Just when i figured out how to update my psp's firmware ( Currently 3.300EAR+) , i discovered that i have problem with my battery, the battery icon disappeared on the main menu and on the battey information it says 'External' and thats it. This problem is preventing from my PSP from updating, when i load the 3.52 M33 update, it always say that my battery is under 75% even though i charged it over night and the power light was off the next morning.
Please can someone give me a detail instruction to solve this problem or suggest to me whats going on ?
Sorry if i violated any rules by posting this, i am also new to this forum.

[CoNFuSeD™]

I think you over charged it.