I am running a 20W halogen off of a 14.8v Li-Ion pack. I find the current draw to be more like 2A than 1.4A. I get 2-2.5 hours from my 4.8AH pack.
For a housing I use a 4" piece of 3/4" copper pipe. I drill a hole in the side for the wires to come out. I solder the wires to the terminals of a MR16 bulb and then Gorilla Glue the bulb into the pipe. I add an endcap and seal around the wires to make it all water tight. I then spray paint the outside of the bulb to keep the light from leaking out. A Two-Fish handlebar connector is used to hold it in place.
I have been using this light for the past year with no problems. I actually built a backup but have never used it.