Hi, guys -

On a whim I bought one of those two-LED Thorfires you see on eBay. They kinda look like an owl's face the way the two wings come off the corners. Came with a battery pack and all for 20something dollars.

I knew four good 18650's would cost way more than $20 but I wanted to see what I'd get.

The battery pack was heat-shrinked into a single package. The cable snaked out from underneath the shrink-wrap. I cut it open. The four batteries had a hot-pink heat-shrink wrap on them with no labeling whatsoever. The color looked like LG or Samsung but no labels tells me they ain't LG or Samsung. My guess - batteries probably scrounged out of old laptop battery packs.

The batteries are all parallel. Output voltage is the same as one 18650 cell. Roughly 3.8 volts or so. AFAIK most 18650 LED lights take about 7.4 V. To make 7.4V with four 18650's means a series/parallel combination.

In other words, the battery pack would not be compatible with most lights. Not that you'd want to use a funky pack made from cells of dubious origin anyway.

The "charger" isn't a charger. There's no circuitry to detect when cells are full or to protect you from trying to charge dead cells. It's just a run-of-the-mill power supply that is too weak to overcharge the batteries. Hopefully.

The light itself is reasonably bright, but it's that cold bluish light that just isn't very pleasant.

You get what you pay for...

Oh, yeah, I forgot to mention it looks like the Thorfire I bought might have been assembled from broken ones. The metal backplate is stained with some kind of crust, the lenses are slightly scratched and lots of little particles on the inner side of the lens.

There's an "On" button on the back of the light, and three tiny lights that I assume indicate the three intensities available by clicking the "on" button repeatedly. But the three lights don't match the three intensities. All of them come on immediately, stay on for two of the intensities, then one light drops out at the highest intensity. Doesn't make sense.

Thanks for posting your review. I am tired of people posting links to "bargains" and telling other people how great the cheap stuff is but don't write when they have broken it. A bicycle light has to withstand strong vibrations. Often the cooling of the LED is also bad in cheap lights.

Thanks for the warning. That seems unconscionable to me.

I've been using 18650 headlamps for the last few years. Work-related, not bicycle. Have a Nitecore HC30, an Armytek Wizard Pro, and a nice little Zebralight. All of these are basically flashlight tubes with 90 degree angled heads.
I've tried headlamps with wires connecting battery packs to the lights. Every one of them has failed and all failures were related to the wires. Headlamps like these are intrinsically more reliable. No wires.

I also bought a couple of good-quality 18650 chargers.

These lights are bright, they go for hours on one battery, and they're small. One strapped to the helmet would throw light wherever you turn.

Here's what I keep imagining - little pockets sewn into your riding clothes at the appropriate height. Below the shoulders somewhere, but above a traditional chest pocket location. The pockets would be just big enuf to accept 90 degree angled headlamps like the ones described above. I'd want the fit to be snug enuf so that the headlamp doesn't move. Maybe you'd need a strip of velcro or something similar to lash the light securely into place. Slip the headlamps into the pockets, aim them in the proper direction, snug them down, go riding.

The headlamps described above all throw a fairly wide beam. This is intentional. Tightly focused headlamps tend to be disorienting as you walk because the jiggling is disorienting, so wider beam is typical. 18650 flashlights from the same manufacturers will have a tighter beam.