iFixit

Gently glide the iPod opening tool on the top of the display, making sure to free the retaining clips.

The other sides of the iPod should now easily come loose. If they do not, use iPod opening tools on the right side of the iPod in the same way as on the left side of the iPod.

Separate the front of the iPod from the back about an inch (or a couple of centimeters).

The iPod casing is now open, but don't completely separate the two halves just yet. Two ribbon cables are still connecting the back panel to the rest of the iPod.

Use an iPod opening tool to slide up the brown connector holding the orange battery ribbon cable in place. You only need to lift the brown connector up about 1-2mm to free the cable.

Don't lift up too far or you could pull the battery connector out of the logic board.

Make sure to slide the brown connector directly upwards. The connector is frail and will break if it is accidentally shifted to the side. The connector has hooks at the bottom to hold the cable in place. As soon as you break one of the arms you will have problems putting the battery cable back on. If it breaks put the cable in the slot and then push the brown holder in place to keep the cable from slipping out.

Remove the cable from the connector.