Just tried the recovery at 12.2v, get to 100%, dings, then dialog box comes up and says download failed. Prompted to turn off for 5 seconds. Turn back on, prompts to run recovery again.The voltage recommended by Tune-ECU is at least 12.5V at upload.
I have had lower numbers and it worked. But never as far down as 11.8.
If you pulled the headlight fuse, you still need about 2A to keep it above 12.5.