eGo batteries are not really meant for use with low resistance atties.. I have heard of this happening all to often. I would bet the cisco you are using was a 1.5ohm and that over stresses the battery protection circuit and causes this failure. If you are going to use a low resistance on a eGo type battery you should go no lower than 2 ohms resistance as a standard Joye atty is 2.3 ohms the 2 ohm is not far enough out of spec to fry the battery mosfet circuitry.