Hardware Problem about PsP battery

[Lemski07]

I'm having an issue with 1 of my battery , my psp boots up when its only plugged but turns off when I remove it, it happened today when I just watching "H#&%@!" movie in my psps when suddenly it turned off and wont open,(it sucks when its already in the climax), this is my backup battery that I bought just recently about 2 months ago and I dont often use it, just used around 5 times just when my original battery runs out of juice when Im outside, and today also make it 6

but when Im using the original one (main battery) It turns on just fine "for now"

so which of it has the real problem the unit itself (I hope not)

or my battery just short circuited (I hope so)

if youve encountered problem like this please share I would appreaciate it very much