Around 15 years ago, my friend Al helped me build a mountain bike light system from a bunch used light parts and pieces:

It consisted of:
- A used set of black lamp shells
- A set of lamps from online (showing are the 450 lumen lamps, but had previously used a few different sets of incandescent with lower lumens)
- 1 nickel cadmium battery pack (ordered from online)
- 1 plastic Vons peanut butter jar (it fit into the bottom water bottle cage)
- A few used foam bits to pack the battery safely
- 1 toggle switch and some automotive connectors from Al's parts bin
- 12" of speaker wire
- An embarrassing amount of electrical tape, zip ties and Verdugo mud to hold everything in place
- A charger (not shown)
It was fairly bright and sort of reliable. One winter night while descending a fast and steep section of La Tuna, the lights simply went dark. Poof. After safely braking to a stop and fiddling with the wiring, I got it going again.
Surprisingly, I wasn't shopping for a new light system the next morning. Did I mention that I'm a Taurus? That may explain things a bit. I have this silly obsession of using things until they're absolutely used up. I'm reminded of the Scottish saying: "Use it up. Wear it out. Make it do. Or do without."
I kept it working and used it far longer than I should have. Last week it finally died and I'm still alive. For a while there I thought it would be the other way around.
Time for some real lighting:

Enter REI to the rescue. This light has a lithium ion battery, 750 lumens, easy on/off/adjust button, USB charging and weighs less than half of the old system. No zip ties, electrical tape or exposed wiring! I have seen the light.
Ok all you mountain riders, what is your light system story? If you've ever had a zip tie and speaker wire system, I'd love to hear how it all worked for you. Or didn't.