For disconnecting the battery, you have to desolder the connection on the logic board. Take care, don<t remove the 3 solder pads. Use hot solder iron, lot of flux and solder wick. http://www.youtube.com/watch?v=LrFaXblPn... If you bought a broken ipod, take a look if you have a missing pad. That can cause the problem. Take a look on youtube, how desolder an ipod battery.
First try to enter into disk mode and connect to itune. If you stuck on not disconnect, hold down the menu and center button to reboot and disconnect the cable when the apple logo appear. if you can't enter in disk mode, open the ipod and disconnect the hard drive cable for 5 minutes. Reconnect and try to open it. You could have trouble if the battery is very low...
If you talk about the ribbon cable of the battery, your ipod won't turn on. It's 3 wires, red, black and white. You could change for a new battery. The wire are attached to the battery. Be sure it's the same cable you're talking about.
You get the flashing apple icon when the battery is really low....Charge the battery and take a look after 1-2 hours. You should fix your sleep button, unscrew it, there is a little metal pad under the sleep button, just replace it in the center with glue and it's done. It hard fix an ipod without sleep and home button.