Hey there. I am currently taking Apple's IT courses for device support, and I would be happy to help you out!
Your battery is most likely the issue, these devices will show no signs of life without a battery. Since you mentioned the iPod had been unused for long periods of time, this is very probable.
However, there are some things you can try before you open up the device and attempt to replace the battery:
# ***Use a different charger***
## There is a chance that the cable you are using is damaged
# ***Clean out the port***
## Using a toothpick, clean out any dryer lint or dust that has built up in the charger port, both lint and dust can cause faulty connections
# ***Connect the iPod to a Mac or PC***
## Does the device show up in the Finder or iTunes? If so, let me know, and we'll go from there.
In conclusion, your device may not be completely dead. Try these suggestions and let me know what you discover!