LED Flashlight for Helmet Light

I blame Dave Harris for getting me interested in LED lights for cycling. Here are some of his LED light projects. As you can see, he's come up with some very bright, long-running lights for his endurance races. I've done plenty of tinkering in my time, so I got fired up to build my own lights. But as I searched the web, I decided to try an intermediate step first - use a LED flashlight as a helmet light.

But first, a little background on LED (Light Emitting Diode) lamps. The newest LED lamp products from Cree (XLamp X-RE Q5) and SSC (Z Power P4) put out more than 100 lumens of light at 350 mA, and over 240 lumens at 1000 mA (1 Amp)! To put this in perspective, a 4-cell Maglite flashlight with a normal incandescent bulb outputs 122 lumens and a 100 Watt incandescent light bulb outputs 1700 lumens. So these new LEDs may not seem like much compared to a 100 Watt house light, but compared to a Maglite they output around the same light but require much less electrical current (from the batteries).

So I went looking to see what flashlights used these new LEDs. I found plenty, but went with the UltraFire C2 that uses the Cree XLamp X-RE Q5 - here it is:



It may look big, but it's only 5 inches long. I bought the UltraFire C2 for $26 from Deal Extreme along with some lithium ion rechargeable batteries (protected 18650 and RCR123A) and a charger. I spent about $55 and it took 2 weeks for the items to arrive from Hong Kong.

I charged up the 18650 batteries and popped one into the flashlight - wow, it was really bright! I came across a video showing how one cyclist used a rubber LiveStrong wristband to attach a flashlight to a helmet, and I was pleased to find that it works perfect for my Specialized helmet:



The angle even appears to be about right, but I may need to shim it up a little. From my first night ride I learned that it's important to have the light shinning where I naturally look. Otherwise I'd have to tilt my head up or down to compensate and this put my head in an unnatural position which was very annoying.

The flashlight makes the helmet a bit front-heavy so I hope it doesn't tip down as I ride. If this is a problem, hopefully I'll just need to tighten the straps on the helmet, but I may need to add a counterbalance to the back of the helmet (I can hear the weight-weenies gasping).

I've been anxious to get out and try the light on a ride, but the recent cold and snow has changed my mind each time. Last night I took it out on the street and snapped this photo:



It probably doesn't look like much, but I'm pretty sure that's enough light for me to mountain bike. Some day I'll take the new flashlight out for it's first ride, and I'll be sure to blog about it.

In the mean time, I need to at least find out how long each type of battery will run. I can use one 18650, or two RCR123A batteries. The two RCR123A batteries should run longer because they produce a higher voltage that will stay above the cutoff (won't run anymore) voltage of the regulator built into the flashlight. In any case it's nice to have more than one set of batteries. When I get the testing done I'll post here in case anyone else is buying an UltraFire C2 and needs to know which battery works best.

I should also mention the two modifications I made. To the flashlight I added a mound of solder to the center of the lamp board so the the short positive terminal of the 18650 battery wouldn't touch other [bad] areas of the board. To the charger I had to add some wires to connect up the horizontal terminals so I could also charge the shorter RCR123A batteries (see the Specifications and Discussions sections for more details).

This flashlight may work as-is for a cycling helmet light. But if not, I could use the parts to make a more customized light - maybe add a larger battery pack for longer run time, or add a bFlex to give me more light control options, or gang two of these together on the helmet for more light, or add 1-3 of them on the bars for even more light! I bought a handlebar mount, but it is made out of weak and brittle plastic and it broke the first time I opened the clasp so, I'll either have to rebuild it, or try something else if I want to try the flashlight on the bars.

Update: I ran a fairly-recently-charged 18650 battery for 5 hours last night and it was still going strong! I finally had to go to bed so I shut it off. I was expecting it to go 2-3 hours tops. Now I'm even more excited about this light. I'll run the light again to see how much longer it will go past 5 hours. Yes, I know the battery will "bounce back" some, but even flawed it's useful data. Maybe I'll take the light with me to work and let it run - if it goes over 8 hours I'll be shocked. Next up is the pair of RCR123A batteries.

Update 2: Continuing the session with the 18650 battery it ran strong for an additional hour, then started to fade. It ran another 30-45 minutes with light that would be good enough for low speeds (i.e. climbing). After that it got pretty dim - enough to see if walking, but biking would be difficult. So, a solid 6 hours of bright light is better than I expected and more than enough for my evening rides - and since I have more batteries I could easily go all night if I did a 24 hour race. Not bad! OK, the next test will be the RCR123A batteries.

Update 3: I tried the RCR123A batteries twice, but they only ran about an hour. The first time I noticed that the flashlight was fairly warm, so for the second try I put it out in the garage with an air temperature near 20. But it shut off again. Both times the light would go back on after it went out, but putting in a 18650 battery it would light. I can only conclude the RCR123A batteries were drained or defective. I'll look into this a bit more, but with the 18650 batteries working so well, I'm not really motivated.