iPod nano 1 won't charge or sync

I had a nano with a bad battery, so I changed it, but now it won’t charge, when it still had a charge left, it wouldn’t sync, so I think the port is broken or I need a firewire cable, I tried charging it with 5v 3A, but the battery contact shows 0,05v, so it kinds charges, but extremely slowly, after a few minutes of charging I’m able to press the button and it shows the apple logo for a second and shuts off ( low battery)

edit: I don’t know what I did but the battery voltage dropped to 1.85, half of the 3.7 it was supposed to have