Hey! Props to you for trying something new. While the through hole components look OK, soldering large gauge wire can be quite tricky, especially if the soldering iron is not powerful. What soldering iron do you use? In these cases especially, it is important to wickthee wire first, wick the soldering pad and finally assemble the two. Raising the iron temperature for this can also be useful (I sometimes use 400° or a bit higher). It is counter intuitive, but hotter iron means quicker soldering job, and less heat in the surrounding area (e.g cable’s insulator)