Ditto on the shorted battery. If the internal resistance of the dead battery is low enough, it will take the full output of the boost vehicle's alternator, plus drain the battery, without building up a charge in the dead one. It's like trying to fill up a bucket with a big hole in the bottom! If you can get the cell caps off, look for one cell that gassing violently or boiling the acid- - - -that one's shorted!
Jerry
