iPod Still DEAD. Battery+Display REPLACED , Hold cable BROKEN

Hey there,

I need your help.

-I was replacing the battery of my iPod classic 7th generation and while i was trying to open the case , I accidentally broken the display.

During the process i also accidentally cut the Hold cable.

-Nevertheless the new battery seemed to work, I could see (through the broken display) that the iPod was charging even if it wasn't working as intended

I mean that the iPod couldnt stay fully operative (Continuos intermittence ON-->Charge-->OFF--->ON-->Charge-->OFF)

I also replaced the Display with a new one (this time without broken anything, HURRAY) but it still doesnt work properly....

Now it seems more dead than ever. not a single sign of life.

Could it be that the broken Hold CABLE (that now is the only broken thing inside) is doing a sort of "short circuit"?

I can't understand anything.

Maybe is just the new battery that is defective and i just need a new one.

(Sorry for my bad english, i'm not a "native")

Hope someone can help me,

Thank in advance,

Mattia :D