Battery only holds a bit of a charge

I just recently changed my audio jack/hold button. Upon taking off the battery I accidentally pierced the battery (the only thing around when I pierced it was the audio jack which I replaced anyway). So I ordered a new battery from the site (noticed that it was a slightly lower mAh than the one I have now, but I put it all together and it worked fine.

I received the battery at about 30% so I charged it, it showed it was at full battery. I used it for a few days, went to charge it again, and now it only charges to about 1/5th of battery capacity. It still connects to my computer fine and shows that it is charging. I've tried a bunch of different chargers, I've reset the ipod.

When I put the ipod back together I did notice that the horizontal metal line in the charging port is split in half. The one half is raised up a tiny bit. I'm unsure if I broke something or rearranged something (if this is making any sense at all).

I'm going to use it until it dies and see if it's not holding a charge at all anymore or just capping at a certain percent.

My ipod is the thin version.