I've been looking around for outdoor flood lights to make into a bike light. I've read through a lot of the Total Geekiness thread but I'm still confused with something - if I buy a light that uses a 20 watt 12 volt MR-16 lamp, won't it be using an AC current? If I have a lead acid battery (cheapest option), how can I get the lamp to work?

This may be some completely stupid question, I know but I'm pretty much a noob at this stuff.

Thanks in advance

Not a stupid question. Most of the outdoor flood lights sold at Home Depot, etcetera, such as the Malibu are low-volt systems, presumably for safety reasons. The 20W 12-volt MR-16 lamps can be connected directly to a sealed lead acid battery through a switch (and fuse, of course).

I looked at the outdoor flood light option back in November when I started work on my own light system. I went to Home Depot, took one out of the box and looked them over.

Black cast metal

The Canterbury Copper fixture looked nicer, but was much more expensive and heavier.

It is just a light fixture with wires coming out and isn't voltage specific. In the end, I decided the outdoor flood light housings were a little bit too heavy and clunky for me and chose to use the Optronics driving lights from JCWhitney instead. Even as we speak, I am working on the light system.

I 'successfully' rigged up a 20 watt 12 volt MR-16 lamp lighting system for my commuter in Dec 06. The biggest challenge/headache for me was mounting the lamp. In the end I kludged it together using a couple of hose clamps (on the stem). I did not use a fuse. I already had a battery charger (for trickle charging my motorcycle battery), so I made sure that I wired up the same kind of connectors on the 12-volt (4.5AH rating) SLA battery. I added a toggle switch (make sure it has adequate amp rating) and that was it. I mounted the battery on top of my rack and clamped it down using a u-bracket (again from Home Depot). Anyhow, all worked well and it sure lit up the dark spots on my commute (all urban). However, I caution you on the following:

1. the whole solution does add pounds to the bike - for me it was atleast 4lbs - I am newbie so I noticed it.
2. the bulb kept popping out due to the vibration - I had to epoxy it to the socket.

I am currently looking into the following:

https://www.littlefishbicycles.com/bikelight/

Pete Knox of Charles River Wheelmen has direction for 12V-20W headlight construction on www.crw.org/cheaplights. Since he uses a battery with 7.5ah the assy is well over 6lbs; however the 20W floodlight lights up the trail

I built my own 12v 20w halogen bike light. It was really pretty easy. I bought a 4.8ah lithium ion battery from batteryspace.com that came with a charger for $95. Not cheap but much lighter than SLA. I put the battery in a small camera case and velcro'd it to the bottom of my stem. I then used a short section of copper pipe and gorilla glued a mr16 halogen bulb in one end. I soldered wires to the bulb and ran them out the back. Connect to the battery through a switch and done. I use a twofish flashlight mount to hold the light to my handlebars. I have built a few of these lights as I get more ideas about the construction. I have yet to burn out a bulb but I carry a spare in my panniers. Each light is about $10 but you could build them for much less if you shop around. If one were to break I would just throw it away.