Upped my game in the DIY halogen light stakes and stumbled across a QH-12IT driving light by Optronics which uses an MR-16 halogen bulb. One thing that worries me is the slots (presumably for ventilation) in the back. This suggests that they may not be suitable for use in rain. Has anyone had any experience with this? Any recommended modifications to improve weather resistance?

Rain will not damage MR-16 outdoor halogen lights. A little petroleum jelly on the bulb pins will prevent oxidation and contact problems when it gets wet. You may want to put a 20-watt MR-16 bulb in the housing for longer run time as most come with a 50-watt bulb. A 20-watt bulb provides plenty of light for bicycle use.

Rain will not damage MR-16 outdoor halogen lights. A little petroleum jelly on the bulb pins will prevent oxidation and contact problems when it gets wet. You may want to put a 20-watt MR-16 bulb in the housing for longer run time as most come with a 50-watt bulb. A 20-watt bulb provides plenty of light for bicycle use.

I agree and will add that these lights are meant to hang off the bumper of a car. Last time I checked they are used in all kinds of weather;)

Cool. I thought as much but was hoping for some feedback from more experienced folks (thanks guys). I put in a 20w bulb and crimped my way (with various connectors) to a very crude but functioning system. I just need to find some weatherproof housings for the battery and switch and things should be good (at least until I start to refine the setup).

Cool. I thought as much but was hoping for some feedback from more experienced folks (thanks guys). I put in a 20w bulb and crimped my way (with various connectors) to a very crude but functioning system. I just need to find some weatherproof housings for the battery and switch and things should be good (at least until I start to refine the setup).

Put the battery in a Rocket Cage (http://www.rei.com/product/776187?cm_re=pageContent*productsNo1*rocket%20cage%20%20%20Cage%20Rocket%20Dry%20SPod). You can seal the edges with silicone (although they seem water resistant as is) and use a nylon strain relief (http://store.solar-electric.com/nystreliti1.html) http://us.st12.yimg.com/us.st.yimg.com/I/wind-sun_2009_15535337to make the electrical connection.

Battery space has good seal switches (http://www.batteryspace.com/index.asp?PageAction=VIEWCATS&Category=887) as well as cables.