Cavemud wrote:The Scurion is actually dated as Bif has come up with a way to have 3.7 volts run the leds which I do believe increases efficiency and allows a much greater runtime.
The Rude does run on 3.7V, whereas the Sten and Scurion run on 7.4V (2 Li-ion cells in series). I don't think it's accurate to claim that a lower voltage is more efficient. I think the only advancement is that the XM-L LEDs are capable of being driven off a lower voltage, but this is generally available to any light using these emitters. I think maybe the main advantage of running at a lower voltage is that you can run 1, 2, 3, or 4 Li-ion cells in parallel, which maybe allows more flexibility. For 7.4V systems it has to be even numbers of cells, e.g. 2 or 4, in order to have at least 2 cells in series. One advantage for having the Scurion run on 7.4V is that the batteries are interchangeable with the Sten, which is a fairly common light. I've swapped all my connectors to the Sten-style Molex for that reason, and I have loaned out a spare battery to a Sten user when they developed a short.
Run times for either system will be a function of battery capacity (mAh) and current demand. Efficiency would be a function of how many lumens are output at a given current draw. This is primarily driven by the type of emitter, but can be affected by circuitry and optics. I suspect all of the modern high-end XM-L based caving lamps - e.g. Rude, Scurion, Manley Light, have similar efficiency and therefore run time - assuming apples to apples on lumens and battery capacity. All of these lamps have discreet output settings, and they are never exactly the same, so it's difficult to make direct comparisons. There are also a great many ways to quantify lumen output, making comparisons even more difficult. Also, efficiency is not linear with current draw, so the lumens per watt varies.
Here are the lumen outputs, current draws, and battery life values for the settings I have programmed in the Scurion. My calculated battery life values are almost exactly what I get in real life. These are for a 5200 mAh, 7.4V battery pack (2s2p, 2600mAh LG, 3.7V).