NOTE: I made this projects specifically to have a powerful lamp to mount for a night ride. All the connections, the meter, the lamp pins, the battery terminals, are NOT waterproof, neither water-resistant. For the same reason I don't need any power switch, and I need a fast to plug lamp support. Pay attention to use a so much powerful battery pack with rain or wet hands!
Step 1: The Lamp
I bought in a shop a 4 cree leds 6W lamp, but of course I can change it whenever I wish with a more strange or powerful LED spotlight. You can determine your best choice also referring to the beam angle. You can find an angle from about 30° to 60°, remember that a narrow beam will light further, but street sides will remain in darkness, the same as road signs.
Step 2: Power Source and Connections
You can buy a little cheap display which shows voltage and amperage (mine from HobbyKing.com), so to solve the discharging problem.
In the first picture you can see the cables I made to connect battery to the lamp, and you can insert the display between them if you wish.
To make the lamp plug I simply used a pair of electrical screw connections for wires, I sanded down the sides, so to glue them and obtain the right distance between holes. In this way I can tight the MR16 pins with the screws.
Step 3: The Stand
I decided to build a "fork" which holds the lamp from the two groove on the stem sides.
So, with the aid of a saw I cut an opening in its end, and I enlarged it with some files.
Step 4: A Bit of Work
Step 5: That Fits!
Some lamps have a glass or ceramic stem. In that case you have to pay much attention to make a perfect "fork" and to not break the stem.
Step 6: Fastening the Battery Pack
I fastened everything with some velcro. Let some freedom to the white wire, so you can steer with no constrictions.
There is no power switch since the connections are very easy to unplug.
Step 7: Mounting the Lamp
I had to bend the support because my lamp was too low and the wheel shadow was annoying. The more you lift the light, the better you'll see in front of the wheel.
About the cost of the set it's not high at all (the lamp is about 15$, and the battery is an all purpose battery you probably already have if you like hobby-modeling). Of course we all know that nowadays you hardly save money making a tool or a gadget, but you could love the making more than the buying ;-)
Step 8: Let There Be Light
You have more than 10 hours of autonomy with a 5000 mAh battery! That's too much for me so I'm planning to add a second identical lamp and mount them side by side!
NOTE: I'm not sure the reason my lamp draws 350 mA from the battery, since the lamp details say 700 mA. It certainly derives on the fact the lamp is for AC current and I power it with DC current. But although I red some topics about the matter, I didn't understood enough to explain it here, I'm sure some of you can enlighten us ;-)