I inadvertently confirmed today that if you plug in a cell backwards you indeed do need to buy yourself a new Nano.  :)   Still works, but voltage calibration is way off and seems to bleed between channels.  I messed up the ADC for sure.

In other news, I built a 10 slot 1A charger so I can charge the cells now at least as fast as I can discharge them.  Looks good and works well, but two of my charger modules were DOA so that is waiting to become a Project for now.

<EDIT> 

Replaced the Nano.  Everything else survived.

Also got the replacement USB charger modules in today, and put them in.  Cell charger project complete.

</EDIT>