I like the bold and legible typography in these concepts.
I'm not a fan of using the initials of Jumper Cable as a visual design. I'm not sure it adds much from a communications standpoint.
I think using red and black (the typical colors of real jumper cables) would better link the visual to the brand name as opposed to green or blue if we're trying to visually depict actual cables (entry # 4).
Finally, any logo design should include the current (may change) slogan, "Restart your marketing."
I think it now looks more like electrical cable as opposed to tubes with the addition of the copper. Could I see a version where the copper cable interior does not extend past the red and black insulation?
#47, #48, #49 don't feel like improvements over #28. I think without the head, wire guy is just a couple of wires. I prefer the clean look for this design.