most energy efficient lights in the 1AA and 2AA class?

Hi,
I was wondering which lights you would pick for the most energy efficient for the single AA and two AA flashlight? Disregarding interface, which lights give you the most efficiency (lumens vs run time).

Not sure if I should quality lumens vs runtime...because how do you compare 0.2 lumens running for 1200 hours vs. 200 lumens for 2 hours, and every flashlight has different modes. But take a shot at it.

As a small divergence...how would you quantify efficiency? Area under the runtime curve?

200 lm * 2 hr=400 lm*hrs
0.2 lm * 1200 hr = 240 lm*hrs

I'll start off with my picks, but I'm by no means an expert, so please chime in:

2AA:
Klarus ST20
Quark AA^2

1AA:
Zebra SC51
Klarus ST10

2AA: Quark aa^2
1AA: Fenix LD10, Zebralight SC/H51

How do those Thrunite Neutrons in 1xAA and 2xAA fare????

It sounds like you understand the concept pretty well. I would just add that the best one to one comparison for your purpose might be to decide on a fixed drive current, or a fixed luminous flux and see which light either has higher flux at that current, or draws fewer amps at that flux.

That said. For light in the usable range, I would put the SC/H51 at the top for one AA.

Edit I forgot to mention the thermal aspect. In your example of finding area under the curve, you assume a constant flux for a given duration, however LED's tend to become less efficient at higher temperatures. You're going to be making a lot more heat at 200 lumens than at .2 lumens which will reduce the area under the curve.

The Thrunites do very well at Turbo at high-their high mode is as high as the Fenix/4seven's offerings turbo's. At turbo, the 1A does higher than the Zebralight H51, for only a bit less runtime. The 2A runs almost as bright as the LD20 on high, and runs 45 more minutes.

coachclass said:

2AA:
Klarus ST20
Quark AA^2

1AA:
Zebra SC51
Klarus ST10

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Good picks. As a general rule, current-controlled lights (like the prototypical Fenix LDx0/PDx0 models) are at the top of the efficiency class. The Klarus lights have comparable circuits. Olight/4Sevens and Eagletac also use current-controlled in a number of lights (although Fenix/Klarus often seem to squeak ahead of them). Zebralight uses PWM at lower levels, so won't typically be as efficient (but the SC51 is stunning on Hi).

FYI, I just posted a review of the new JetBeam Backup series, which is very impressive on both Hi and Lo.

selfbuilt said:

Good picks. As a general rule, current-controlled lights (like the prototypical Fenix LDx0/PDx0 models) are at the top of the efficiency class. The Klarus lights have comparable circuits. Olight/4Sevens and Eagletac also use current-controlled in a number of lights (although Fenix/Klarus often seem to squeak ahead of them). Zebralight uses PWM at lower levels, so won't typically be as efficient (but the SC51 is stunning on Hi).

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Interesting. I'm don't know about the amount of circuit overhead that results from PWM vs. current control...but it seems like more manufacturers use PWM for moonlight modes. In that moonlight mode, I suppose the LED is using so little energy that the circuit overhead becomes a large percentage of total watts consumed. Does anyone implement a moonlight mode <2lm with current control?

I thought they used PWM for moonlight because it was more difficult to do current control for the low moonlight consumption? Kind of like it's difficult to regulate current over a large dynamic range (from 5mA moonlight to 1000mA high, let's say).

Overall efficiency requires a good circuit matched to a good emitter. In addition, most emitters are more efficient at lower output levels. You'll get more lumen-hours at 5 lumens out that at 100 lumens out. Good circuits (Fenix, Quark, some Zebra output levels) matched to a Cree XP-G with an S2 or S3 output bin are documented as very efficient. New lights with XM-L emitters may be even better, time will tell.

I have the both the fenix ld10 and the ld20 and both provide as much light as you would realistically need for most everyday circumstances and the runtimes are excellent. I wouldn't hesitate to recommend them.

Also Boost only drivers (like Fenix) or Buck only are generally more efficient than broad voltage support Buck/boost drivers like in a Quark. I'd still pick up a Quark though for the battery versatiltiy.

coachclass said:

Does anyone implement a moonlight mode <2lm with current control... I thought they used PWM for moonlight because it was more difficult to do current control for the low moonlight consumption? Kind of like it's difficult to regulate current over a large dynamic range (from 5mA moonlight to 1000mA high, let's say).

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Yes, my understanding is that it is very difficult to do stable current-control for moonlight. Even relatively low Lo levels are tricky (i.e. say, below 10 lumens). But I have seen a few lights on moonlight with undetectable PWM in my setup - doesn't mean they aren't using PWM, but the freq seem to be above the range I can detect.

cave dave said:

Also Boost only drivers (like Fenix) or Buck only are generally more efficient than broad voltage support Buck/boost drivers like in a Quark. I'd still pick up a Quark though for the battery versatiltiy.

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Yes, a good point - boost-only circuits (like many of the Fenix lights) have an advantage over boost/buck (like the Olight/4Sevens). And I agree, I'd go with the extra battery versatility for a small drop in efficiency.