On the A-Star 32U4 Mini SV, What’s the difference between Bat- and GND?
Bat- and GND are connected together on the A-Star 32U4 Mini SV. See page 6 of the schematic diagram. https://www.pololu.com/file/0J780/a-star-32u4-mini-schematic.pdf
Jim is right; BAT- and GND are the same node.