Great middle act, confusing ending.

I ran this adventure today, I found section 1 and 2 really fun and the players enjoyed it just as much. The 3rd act fell a little flat, the players felt extremely confused about what they were supposed to be doing with the Battery, what the battery was, the crystal and so on. I believe part of this stems from my lack of understanding and preparations of the ending, however act 3 didn't feel nearly as well fleshed out as act 2.