Traduciendo paso 3
Now the battery's out, it's time to open it up. From this point on you should be extremely careful, as damaging the battery could cause a fire. If the battery starts getting hot, or you slip and damage it, throw it outside immediately.
The battery case comprises a base and a lid, held together by some hot glue around the inside. Some gentle persuasion with a screwdriver around the edge is all it takes to separate the two pieces.