So: turns out if you have an Android-based handheld, definitely don’t let it run down to no battery and then leave it in a drawer for two months, because then it is VERY UNHAPPY about doing anything when you plug in a charger. Boot cycle a go go!
@ahchay It wouldn’t do anything at all. Just kept rebooting. Only worked when I convinced it to go into bootloader mode. At that point, I left it plugged in for a half hour and reset the device from the boot loader, whereupon the battery had charged very slightly. That was enough to leave it charging overnight with the screen off. But: yikes.