You should have done more grinding.
Go find the nearest save crystal, fight a few monsters you can handle until you start getting killed, then run away and use the save crystal again.
It also pays to know the monsters' elemental weaknesses - use Libra on them. I can't quite remember but I think the battery mimics were weak to thunder element damage. If you're in need of spells, just grind until you can afford them on the license board.
Oh, and get Basch some spells or a weapon. He's a real tank.