Download the file with the button above

Rename the downloaded file to tb.bat

Start a youtube video

Open a command window in the downloaded directory and start with:
cmd> tb

Unplug the laptop and wait. If the laptop goes to sleep (maybe youtube auto-pause) just wake and start the video playing again

If battery dies check the number of minutes with:
cmd> type tb.txt | find /c /v ""

If running is >100 and estimated is >120, record the estimated and stop the script with CTRL-C