Whazzup with runtimes?

A general question, maybe too general:

What effects runtimes for LED lights with similar output?

Things that come to uninformed mind are:
1. Efficiency of LED.
2. Efficiency of voltage booster circuit.
3. Heat loss (related to above).
4. Battery's internal resistance.

A case in point. I recently got a Peak Killimanjaro 1AA light with "Snow" LED. Comparing it with my CMG's, it has slightly less throw, about the same sized spill, about the same spill brightness, hotspot wider and even more uniform but slightly less bright and less bluish. Overall lumens looks to my eyes to be essentially the same. (Yes, switched batteries around). Per various sources here and elsewhere, CMG gets about 10.5-11 hours to 1/2 brightness with alkalines; per Peak website, Killimanjaro runtime plot indicates about 8 hours at best. Yet the newer light should be using improved LED with presumed greater efficiency (yes? no??) compared to now "old technology" in the CMG.

Not sure what gives.

- Bill

One thing to consider is how good the regulator is. Some lights will have less time to 50%, but more time to 25%, for instance: a longer tail. Also, I have head that snow LEDs can be less efficient than other types. I think that you have to pay for the increased whiteness. It's worth it to me, anyway.

Well, it's pretty complicated. I know next to nothing about Peak or CMG/Gerber regulation other than in general, I like both lights. As dagger sort of said, there are different types of regulation... Actually, the higher end makers don't consider voltage regulated lights to be regulated at all... There are also voltage boosters (which take 1.2V from an AA cell and increase it to the 3.8-ish volts needed for the LED, there are voltage limiters which perhaps take 4 AA cells (4.8V) and throttle the voltage back to the 3.8 needed. Then there are current regulators... that send a given amount of current to the LED at all times... Some will use up the cell(s) until that much current can no longer be wrung out and then they just shut off... and there are regulators that send the whatever amount of current until they no longer can, then they dim after that point.

For my personal use, I figure out how much output I need a given light to put out and I figure how long it can do it. I honestly don't care if it dims 15% over the 'bright' period or if it maintains 100% brightness until it shuts off at the very end.