so what happened is this... i have (had a slim and fat) i sold the fat fo $80 usd last night with nothing extra but a charger cord ( gamestop will only give you 60 for store credit and 44 as money) so i would not give up the fat battery cause i need it for pandora.. the fat psp was on 3.52 so i wanted to put 3.90 on it.. i used the pandora i have to make it 3.71-4 (i think -4) then i was going to go to 3.80 then use the networkupdate... well the updates for some reason crash when you have a pandora battery in the psp with the ac cord plugged in so i tried my slim battery and all was fine till i reboted to the recovery menu on the fat... i changed nothing i was just showing to the person i sold the fat to... so i restarted and it would not work.. i put the battery back in the slim and nothing... no orange light, no battery bar in the xmb nothing ( yes it was charged.. fully).. so i dropped it on the concrete floor from 5 feet three time and still no go so i went to bed... woke just now and slapped the slim battery into the slim and the damn thing works.. im so happy but also got to say double you tee eff???  don't put a slim battery in a fat