Constant output for Xenon bulbs?

I haven't been able to figure this out as I can't find any runtime plots for incandescent flashlights, so do they have constant bright output and then just die or do they start petering out?

Actually, most incans just reduce their output as batteries become exhausted. IIRC one of the surefires is the only regulated incan out there right now. Not sure if there are others, though.

ok thanks. so is the rated time on them how long they last before going below their rating, or how long they last period?

To have a constant bright output with todays batteries you must have a regulator built in. Alkalines have a slow downward slope from the time you start them. Lithium and NiMH cells have much flatter discharge curves, and then drop off quickly. They act much closer to a constant bright output before quitting.

The Surefire A2, using 2 Lithium 123 cells, is the only widely available regulated incandescent out there. Runtime of approximately 50 minutes at full brightness before it shuts off and only the LED's will light up.

There is a regulated battery pack for the Surefire M6 undergoing field testing right now. This pack is designed and built by js, one of CPF's members and there are fairly lengthy threads in both the incandescent section and the Modified section about it, if you do a search.

Bill

In answer to your second question, the stated times are generally to 1/2 brightness, but every manufacturer has different standards.

Bill

You can find runtime graphs on the battery manufacturers web pages although they don't always have one that corresponds to any particular bulb.

I usually estimate run time based on battery capacity divided by .75 amps (most common Xenon bulb rating). For example, 2500mah nimh AAs can be expected to last 3 - 3.3 hours. This works better for nimh which hold a fairly constant voltage and therefore also have a fairly constant amp draw. Alkalines (2500-2800mah capacity) drop from about 1.5v to 1.0v, and therefor end up drawing about .450ma (about 1/2 light output) when the light is getting dim. This still approximates the usable run time since the average current is lower. YMMV since various light outputs are suitable under different conditions or for different people at different times.

Unregulated: dimming with time.

Regulated: constant output for a given amount of time, then either complete shutdown (you're left in the dark) or just enough light for you to navigate around and find new batts.

The Black Diamond Supernova and Vectra IQ are also regulated incans.