Geez,you guys don't know how lucky you are......When
I was a kid.........
the only power unit for Lego was about the size of a house brick and ran at about 2 m.p.h.It was attatched to its fuel source,another house-brick size unit full of flashlight batteries by a short cable,and if was any uglier it would have come pre-fitted with Ford stickers....
http://www.fgltc.org/bwoabs/9v_12v/9v_12v.phtml