Itouch battery trouble

Hello, My name is Mason. A few days ago i took apart my ipod Touch 1st gen to repalce the digitizer. when i reassembled it, it wouldnt turn on for a day. now i got it to turn on but the battery runs out much faster than usual. i took it apart again and noticed that one of the three wires connected to the battery had come undone. I dont understand why the touch still works but more importantly how to fix my battery life. Please help!!!