That melted fuse is telling you you have a direct short. It won't charge with that fuse blown. Lots of guys rewire the charger receptacle to go around the old fuse. It is easy to do and works fine. You loose the protection that you obviously used
but you can replace it with a $4 175 amp fuse from any auto parts store mounted between the battery pack Negative post and the cart...... Do you have a voltmeter? Is this a controller cart or resistor? If you can't tell how about posting a picture of the battery compartment?