New battery installed. Tested. Case closed :) iPod nano 3G is back for many more years of service, hopefully :) That was definitely a tough repair. These iPod nanos are quite demanding to pry open. But it is done. Onward to saving more devices from ending up at the landfill.
@jwildeboer Nice! I also have a 3g nano but have been lucky enough not to have to replace anything in it yet. After relying on my phone to listen to music for years, it's remarkable how well they actually hold up. Simple, elegant, good build quality, actually fits in your pocket, etc.
It won't work for the 3g but you might be able to stretch the capabilities of the gen 6 with rockbox. It would make it easier to load music onto them if you aren't able to run iTunes. I've had that issue with Linux. https://www.rockbox.org/wiki/TargetStatus