Zebralight SC51 run time on strobe

Apologies if this has been covered before, but I was wondering if anyone knew, or had found out the runtime of the SC51 on 2000mAh Eneloops when in 4Hz strobe mode? Their website states:

High: H1 172 Lm (0.9 hrs) or H2 86 Lm (2.4 hrs) / 120 Lm (1.7 hrs) / 4Hz Strobe

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with no mention of how long your battery may last if you're stuck in an emergency situation for example. OK, you should have spare batteries but it would be nice to know. Just thought I'd check if anyone else could save me hours of staring at a strobe to see when it finally stops!

mat_the_cat said:

how long your battery may last if you're stuck in an emergency situation

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What duty cycle does the strobe give you?

I'm not sure - I don't think I have any means of measuring it. I also am unsure how that would help me, as I don't know the strobe output, nor what current is being drawn between flashes. In saying that, I've just thought that if I measure the tailcap current when on strobe, it should give me some idea of battery life...

Runtime is not going to be great, because it's NOT A STROBE. It's a blink. Just from looking at it, the duty cycle can't be too far away from 50%. So the battery life wouldn't be that great. If the duty cycle were made more like 1%, the battery life could be vastly improved without really lowering the visibility at all.

You won't get anywhere at all trying to measure the current with a DVM. Even an analog multimeter would just swing the needle rapidly.

If somebody has a storage scope and the inclination, tell me if I'm very wrong on my estimate of duty cycle.

50% sounds like a fair guesstimate to me - I wasn't expecting a big increase in battery life because of this. I wasn't aware of a terminology difference between a blink and a strobe, just going from Zebralight's description. We do have some fairly high end DMMs at work (mA to 6 decimal places anyone?) and I think I can alter the sampling rate to average out the peaks, to obtain a mean current draw.

Alternatively I could just sit and watch it for 5 hours or so. Mmmmmm…..blinky.

Since there was no question mark in the title, I thought you were making a report of the run time.

/\ Fair point, well it is now!

Been running for just over an hour now, will update later with an approximate run time.

Update - 3.5 hours in and it has noticeably dimmed. But how long can it continue...?

mat_the_cat said:

Update - 3.5 hours in and it has noticeably dimmed. But how long can it continue...?

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Good work. You're using a 2000 mah eneloop I assume right?

That's right, taken off the charger yesterday and only a couple of minutes on low low to find my bed without waking SWMBO last night. 5 hours in and it has dimmed to such an extent that I can tailstand it on my desk in a well lit office without being too distracted. I have had people asking me exactly what I am doing though, as if it's a strange thing to do to have a strobe on your desk...

I would still consider it a useful output which would be visible in an emergency situation, but will accept that it's not what it was designed for.

Update - 6.5 hours and I would estimate that the output is down to a couple of lumens. Battery voltage is round about 0.8V, and it will not run any of the other modes, it just flickers. Strobe still going without visible flicker.

14 hours and flickering started although still strobing (just with a bit of a stutter), so I called the test a day at that. It was still very visible at a distance of 100m in the dark tonight (the longest uninterrupted view I could find around here - we live in a forest!) I'm quite impressed with the way it just seemed to keep on going with a low output! Longer than I expected.

mat_the_cat said:

I wasn't aware of a terminology difference between a blink and a strobe, just going from Zebralight's description.

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I should hasten to add that if there was any criticism implied in my post, it was most certainly directed at ZebraLight's description, not at you. The dictionary definition of stroboscope is "a lamp capable of producing an extremely short, brilliant burst of light," (actually it should say a precise train of such pulses) and that is definitely not what the ZebraLight does. "Blinking" on the other hand is only very loosely defined in the dictionary and could cover almost anything that is cycling on and off. But a blinker on a car or traffic signal is always much closer to a 50% duty cycle than a stroboscope. In terms of nautical navigation lights, I guess they don't even use "blinking," and "flashing" is favored. An unqualified flashing light has less time on than off, an isophase flashing light has exactly a 50% duty cycle, and an occulting light has more time on than off. Beacon is another good word. Strobe, it seems to me, is the most specific descriptor, and should always describe very brief flashes.

For what it is worth

No criticism perceived this end! In fact I've learnt a few new terms, although the chance to use them in everyday life is perhaps somewhat limited.

I notice that the Quark Mini's beacon mode (assuming as I think you are saying beacon should refer to an occulting light) is incorrect too, seeing as that is something like 10 seconds off followed by a brief flash.