The other day while changing the negative battery cable i accidentally bridge the positive and negative cable ends with the socket and burned the shrink tubing insulator of the fusible link. I tried to remove the plastic cover of the fusible link to insert a new shrink tube but it seems impossible. Should i buy one new or should i just wrap some 3m electrical tape where the shrink tube was? What if i leave that o ring connector naked? 

That is not a fusible link, it's just a wire.  All of the wire ends down there are exposed so a little bit more won't matter.

Do you have a picture of the part on your car that was melted?  The picture you posted must be from somewhere else.

I circled the part that melted. Plastic shrink tubing that isolates the o ring terminal. I thought i could remove the plastic casing on the fusible link to slide a new shrink tube but it seems not possible. I took some other pictures where you can notice that i wrapped some 3m electric tape to act as insulator.  It seems not possible to remove the casing to insert a new shrink tube.

Edited February 17, 20196 yr by jalexquijano

Does everything still work correctly?  There is no need to put extra effort in to insulating those wires.

If you still want to do it, you could cut the ring off, add the shrink tube, then put a new ring on.