Replacing the battery 2016 Ford Focus ST is a problem

[two4twoinpa]

I disconnected all the air intake stuff so that I could remove the front of the battery box and access the battery. I took off the "-" cable and cleaned it. (There is a sensor that may have gotten wet while I was cleaning the cable but I'm not sure.) Then I disconnected the "+" cable from the battery and removed the battery. I put in the new battery, connected the "+" cable to the "+" post and the "-" cable (with the sensor) to the "-" post but not yet to the terminal that's located outside the battery box. I connected all the air intake stuff again, put the lid on the battery box, and tried to attach the "-" cable to the terminal that's located outside the battery box. I got sparks and after a short time I heard a noise similar to when a breaker trips in your home. The noise came from behind the engine (I think). There are still some sparks if I touch the cable to the terminal. This is not a Ford brand battery. I got it from NAPA. I did attach the cables to the proper battery posts. What's could be the problem?

Update:
I put a meter between the "+" battery post with the "+" cable connected and the ground terminal on the vehicle without the "-" cable connected and got -0.06V reading. I can't 100% vouch for my meter but it does register 12.56V when I test the new battery. I also tested for ohms between the "+" cable not connected to the battery and the vehicle ground and got 65 megohms, showing me, in essence, no short in the system, so I can't exactly explain the -0.06V from the voltage test mentioned above.

 

[two4twoinpa]

OK, I decided to just hook it all up and it all worked OK anyway.