I just got a Nite Hawk Nomad which burns a 5w 6v Halogen bulb. I took it out for a test last night and was surprised that my 1/2w LED was brighter. After pulling out the bulb I discovered that the 6v bulb was replaced by a MR11 20w 12v bulb so it was running at 1/2 voltage.

The stock power source is a 6v 4xD Cell pack. I tried two 4xAAA battery packs (with regular alkaline batteries) wired in parallel to see if they would power the 20w 12v bulb. No luck. Is there a minimum size battery required to power a 20w 12v bulb?

The plan is now to run the unit as a 12v 20w system. This what I'm thinking of doing based on info from this forum and batteryspace.com.

1. Use existing housing and 12v 20w MR11 lamp.

2. Use 12 NiCad or NiMH AA (if they will work) rechargable batteries. I would be overvolting but it seems like this is a fairly common practice.

3. Use 14-18 gauge wire for the project (that seems to be the gauge range for this type of wiring). Does the wire type make a difference?

Basically I'm hoping that you guys can let me know if I am on the right track and understanding what I have read regarding DIY lighting. Thanks for any feedback you can provide.

Have you considered going LED as well? The Cree Q5's have dropped $2 already in price reflecting the new Cree R2 LED's that have been on the market recently.

www.dealextreme.com and get the orange-peel or smooth reflectors whichever seems to suit your liking. IMHO smooth has longer range. The OP reflectors diffuse the light a little.

My quad-damage uses 4 x SSC P4 LED's.

http://www.flickr.com/photos/49184877@N00/

It's around a 600lm light right now. I'msure with a better housing (uber ghetto right now as I'm opening it to change things all the time) I can make it cooler and thus possible more brighter.

I'm running off 6xAA. Booyah!

You should be able to fit a Fraen Elliptical Beam Lens With Holder, Star mounted power LED, and heat sink similar to this example.
http://pilom.com/BicycleElectronics/LEDhead.htm
Here is where I get the Fraen lens and holder used in the link above as Martin does not provide it.
http://www.luxeonstar.com/item.php?id=462&link_str=121::125&partno=FHS-HEB1-LL01-H
You may battery power it or use a standard dynamo. Martin has a very good page showing how to do both here.
http://pilom.com/BicycleElectronics/BicycleElectronics.htm

Here is my dynamo powered light using a Fraen Elliptical 15X30 and a 10 degree narrow.
http://i143.photobucket.com/albums/r154/n4zou/HPIM0395.jpg
Note the use of a blinkie due to the fact that my light goes out when I am stopped. Otherwise dynamo power allows unlimited night time rides. The blinkies I use front and rear will operate on 2 AAA batteries for about 200 hours.

I was going with halogen for the simplicity and ease of finding components locally. Is LED significantly more complicated?