Battery unable to hold a charge even after replacement.

Hey guys,

I've recently been trying to repair my seventh generation iPod Classic 160Gb, and it's really starting to get me confused.

Initially, the battery stopped holding a charge and would drain incredibly fast, and eventually it ended up at the point where the device wouldn't power up at all even when plugged in.

My first thought was that the battery was likely dead, so I bought a replacement on eBay and fitted it.

At first it seemed OK, but I was initially worried because it was taking a long time to charge to full. At this point, everything seemed fine, but it appears to be suffering from the same problem as before. The device struggles to hold a charge, and even if left turned off overnight it won't power up again in the morning. However, at this point, plugging it in will produce the 'charging' screen and it'll eventually charge back up again.

I'm a bit lost as to what to do now, as I can't work out whether the replacement battery is also potentially faulty or whether the issues lies with the logic board.

Does anyone have any ideas?

Thanks!