iPhone does not charge after battery change

Hey there,

I recently changed the battery of my iphone 4s and it works just fine until now. So I also changed the battery of a friend with the same phone. When I restarted it, I discovered that it won't charge. it shows the charging sign but the percentage does not change. Also the iphone did not work without beeing plugged in. I thought the battery must be defect and so I put the old battery back in. Now it works without being plugged in, but it does not charge again :((.

When I opened the iphone for the 3rd time to check for any errors I made, I experienced that the connector of the battery inside the iphone was ripped out with the connector belonging to the battery, when I took out the battery. This happened altough I was extremely careful. So there are loose solderings, but I could place it back together without new solderings, just with the screws on top of the battery connector and the phone still works, but it does not charge..

What should be my next steps to get it working?

Did any one had similar Problems?

Thanks for your help!