One of these is not like the other: iPod classic upgrade

One of the great things with electronc devices in previous years was the ability to replace/repair items but also importantly as the device ages, to replae the battery. Apple have a certain reputation when it comes to repairability of their portable devices (iPhones, iPods etc) and its not positive as they cram more and more into smaller spaces. However there is a set of iPod that can be relatively easily self serviced and revived.