How can I get a flex-bit unstuck if the shank is stripped?
If it is a steel shank drill bit, grind off where it's striped, ~2". Otherwise just skip to grinding three flats, 120 degrees apart to give the chuck something to grab. Back the bit out and start over with a nice, fresh battery. Corded drills with keyed chucks are way down in price. Using one of them could most likely get you out of this situation and would probably have avoided this in the first place.



You were using something like this, hex-headed flexible extension in a cordless, keyless-chuck drill.



When you should of been using this, 4' flexible drill bit, keyed in a corded drill's chuck with a handle.