You will have to check the wires in the circuit for the system both positive and negative as you don`t say which battery terminal you connect when the fuse blows.it will be a short as an 80amp draw is alot to blow for a fuse.try disconnecting the alternator before hooking up the battery.if it(fuse)doesn`t blow then the problem is the alternator new or not,as thats the only thing removed from the system witht he fuse not blowing.if it does blow the wiring will have to be checked for shorts.

I suggest to check if you have oil leaking onto your alternator or did you recently replace the alternator? Keep in mind that the voltage regulator is built into the alternator on vehicles and I have seen oil leaks internally short the alternator or poor quality aftermarket parts.

Also check ground and wires broke or in short.