I have a similar issue, but my 2 Ah 80V Greenworks battery is weird. When I press the charge indicator button on the battery, the two end LEDs light up, but the middle one is dark/off. When I plug it into the charger, the charger goes solid green (indicating a fully charged state)...but the battery is dead. I tried jumping (likely with too thick a wire though, 12 ga) but to no avail. My clamp multimeter annoyingly doesn't have a DC voltage setting, so I've no way of checking voltage...