Longtime member (though longtime) dormant here ... I've been running DIY halogen bike lights with overvolted MR16 halogens for years, but I'm thinking it's time to finally upgrade to LED. Not really interested in the MagicShine route because of the floodiness of the beam: I spend a lot of time on shared paths and I'm not willing to subject oncoming pedestrians and cyclists to that much glare.
Im thinking the easiest and most cost-effective way to get a reasonably throwy LED setup is to take a P60 flashlight and mod it with an external battery pack. Probably initially going with an XP-G unit for low beam use, then maybe later adding a second XM-L (likely a nailbender drop-in) for high beam use in areas where I dont have to worry about blinding folks.
I haven't bought the flashlight(s) yet, so my options are wide open. The Solarforce units are appealing, but which voltage? I've been pretty happy with my NiMH packs over the years, and don't see a reason to upgrade, so my voltage choices are in 1.2V increments:
- 3.6V might work with the low voltage (4.2V max) lights and drop-ins, but will the working voltage be high enough to drive these effectively?
- 4.8V is more appealing to me than 3.6V because it means 33% more Wh out of a 5Ah pack, and would be capable of driving the new Philips bike light, should I choose to go that route in the future, and might also be capable of driving generator taillights. Should work with the medium (4.2-8.4V) lights and drop-ins, but these seem a little harder to come by. Am I limiting myself too much at this voltage? Can 4.8V effectively drive the higher voltage (4V-18V) lights and drop-ins, or is it a tad on the low side? Would 6V be better?
- 12V is also a contender, simply because I already own packs configured for this voltage, and can also power 12V automotive accessory lights for taillight or running light use. Ive seen some reviews on dealextreme indicating that some of the higher voltage drop-ins rated for up to 18V actually run very inefficiently (and excessively hot) at voltages this high. If not 12V, what would be an optimally efficient voltage for these drop-ins?
Thanks in advance for any advice on voltage, and also just generally on this approach for bike lighting. As long as you shim the drop-ins with aluminum to ensure proper heat transfer to the light body, do these setups run OK for an hour-plus of continuous use? Do you need to shut off the lights if you're stopped for more than a couple minutes (which I already do with my halogens)? Most of my night riding is in fairly cool conditions, 30 to 50 degrees F, although there is the occasional summertime night ride, which might involve more like 70 F.