I have a '97 Ford Contour and today a friend and I were installing 2 12" sub woofers and an amp with a Raptor amp power kit. We disconnected the car from the battery and cleaned some corrosion from the post and the connector unit, attached the power cord to the connector unit and tightened it back on to the battery posts. After this was done, the car did not start, but it did have a small amount of power. Enough for my automatic door locks to work, but at about half speed. Also, my car normally beeps when the key is in the ignition, but now the beeping is elongated and lower pitched. When I turn the ignition key, the starter does not turn at all.
Additionally, upon second inspection, there is a loose wire now that has been disconnected from something. I have a picture showing the loose wire and where I
think it was connected, but I would like to ask about it first. Also in the picture is the battery setup now, with the under-hood fuse box. The green piece that I highlighted in the picture was making a rattling noise at regular intervals when the problem first happened, but has since stopped.
Any advice or enlightenment as to the nature of my problem would be welcomed, thanks so much!
Battery Work made my car not start 
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