I'm currently working on a wireless charging setup on both a iPod Classic 5th and 7th Gen. I learned early on that soldering the positive and negative connections from my wireless receiver coil to the battery neg/pos terminals on the iPod mainboard immediately drained any battery I had in the iPod. It would, however, charge the battery if it were on a charging station. The only solution is to pull the mainboard of the iPod out and find the pos/neg terminals that the sync port uses via USB and make the coil solders there, where it's meant to receive power. Those terminals are so tiny, though, I'm already dreading it as I'm no soldering expert. This should work, though. You can also purchase charging base stations with a receiver coil kits for about $10 on eBay. I've found even the cheapos to be reliable.
Matt