LightBench: A Laboratory Testing Procotol for Comparing the Performance of Flashlights and Headlamps

[Ryan Jordan]

Companion forum thread to: LightBench: A Laboratory Testing Procotol for Comparing the Performance of Flashlights and Headlamps

In this technical brief, we quantitatively evaluate the performance of lights considering brightness, battery life, and weight into an objective Lightbench Index.

[Terran Terran]

I think the lightest would be the light on my phone, which I’m already carrying. Perhaps something that plugged into a power bank that hung from your belt or sternum strap. Dual led headlights I think would be lighter than carrying an extra battery.

[tkkn c]

Headlamps have come a long way.  I think LED’s were the  biggest  improvement.  This was state of art in the late 70’s early 80’s.   You could run it on 4 AA batteries or a single Lithium D cell.   The Lithium D cells were expensive.

[John K]

One of the things I found manufacturers doing is ramping down brightness very slowly so the eye doesn’t notice. Example is the new nitecore NU20 classic ramps down in medium after one minute to some intermediate brightness. I noticed this when I was doing run time videos between old NU25 and new NU20. When I sped them up I noticed the shift in brightness.

[Marcus]

Nice inital scope. I’d like to see the NU25 (non-UL) and the NU20 Classic tested for comparison

[Greg F]

Good article.  Should the LBI value be de-rated to penalize manufacturers who don’t really achieve the maximum lumen value?  Or is this a common ‘feature’ with all manufacturers?  Looking at the plots, neither headlamp maintains their stated maximum lumen value for more than a few minutes.  The real number for the Fenix appears to be about 120 lumens, and for Petzl, 295.

[Ryan Jordan]

Greg – good point, the article was just updated this week to to add an analysis for effective brightness, which is a weighted measure of how much light is delivered early in the runtime. In addition, we re-ran the tests on new (better) instrumentation and dialed in the lighting performance more accurately. We’re using the new instrument and calibration standards moving forward with the rest of our testing now.

Marcus – yes, both of these headlamps are being tested right now, along with a whole slew of others. The tests are mostly done, we’re now writing up the results.

[Barry B]

How does temperature impact all these metrics? In really cold weather (like 10 deg F and lower) what are the specifications I should be looking for to maximize performance? Is there a specification I should be looking for to minimize battery drain? And in this case I’d be referring to long run times at reasonable lumen output. I’m always fascinated to see the wide range of head lamp styles when watching documentaries on expeditions like Everest and others. Most of my hiking is done in the Northeast and Winters can be quite cold and damp.

I have a lot of battery powered devices (like most here I’m sure) and the range of battery life across them is staggering. Batteries in photography equipment (or the infrastructure using them) seems to be particularly poor for handling colder temperatures. But probably getting off topic there….

[David D]

Lower temps can significantly reduce run time, but the impact will depend on the battery type, specific chemistry and make.

In general, NiMH loses run time (recoverable) below freezing more quickly than LiIon.  My BD Spot 200 run time shortens significantly below -15C using Energizer NiMH rechargeable batteries.  If out for more than a couple hours at night in the winter, I carry a LiIon backup (Nitecore Tube).

Headlamps rechargeable through an in-built USB port will be LiIon, but unfortunately no one tests cold weather run times.

Maybe we can convince Ryan to put a couple of the top contenders in the freezer?

There was a helpful reddit thread recently: https://www.reddit.com/r/Ultralight/comments/1h3ufes/winter_headlamp/

I’m considering picking up a 18650 headlamp with a replaceable battery like the Zebra H600 for use in situations where it would be dangerous to run out of headlamp at night in the winter (a list of others here).  Nitecore sell a battery they claim is cold tolerant: https://flashlight.nitecore.com/product/nl1835lthp

here’s another: https://www.18650batterystore.com/en-ca/products/molicel-m35a-18650-battery

but I haven’t seen any independent tests of them.

One thing to consider about any run time tests is that they’re usually reported when the battery is relatively new.  The number of discharge cycles seen by the battery under test will have a significant impact on the test results.  LiI loses capacity with repeated charges much more quickly than NiMH and the winner day 1 may not be the best at day 50.   50 cycle testing here  https://www.nytimes.com/wirecutter/reviews/best-rechargeable-batteries/#our-picks-for-the-best-rechargeable-aaa-batteries   showed

– there’s a wide variance in cycle life from brand to brand

– Ni MH dropped from 1.5 to 1.2V and lost 3% to 25% capacity depending on brand

– LiI held 1.5V but some lost 75% capacity.

It would be interesting to see how Nitecore fares in cycle life testing.  The lamps tend to be inexpensive and I wonder if the cycle life performance reflects this.  Absent independent testing, hard to say.

[Barry B]

I switched over to all LiIon gear quite awhile back for recharging and better performance. Age of the batteries definitely has a huge impact on capacity. My Zoleo and some other devices have degraded substantially and don’t have a rechargeable battery, which is a huge negative. I love the device but if I ever get a new messaging device I’ll definitely be looking for a rechargeable option.

Years ago I had a headlamp on my gear wish list (Zebra possibly?) that used an 18650 battery. I finally deleted it. I’ve been using the basic Petzl Actika light with the rechargeable batteries. I carry that with 2 extra batteries and rarely need to swap a battery out most times of the year.

What is the big deal about this 18650 battery? I have seen it mentioned in several articles as being “superior”. I was looking at the Nitecore NU53 earlier and it claims an output of 1300 lumens for 9 hours with its 6000mAh battery and an impressive 37 hours at 150 lumens. I didn’t even realize they made headlamps with batteries so large.

[NoCO-Jim]

Long ago I committed to 18650 + Zebralights (ZL), and have not regretted.  The 18650 offers flexibility not only in the ZL, but used with a lightweight Miller charger, can charge other devices, with energy to spare.  Much prefer a generic 18650 in a ZL, than a proprietary cell which years later can be replaced at a fraction of the cost of a proprietary cell, if it all available.

I depend upon and use the ZL as a snake light during their season, on dark early morning hikes, as well as camp lumination in the evening.  Have not had a ZL fail me.  If you want to dig deeper on ZLs & 18650s, there is much advice and experience here.

[NoCO-Jim]

Brain-Fart…this is the correct link in the above post: here

[David D]

“Table 3 suggests less efficiency (lower light volume) in the Turbo (highest) brightness mode of the HM50R. There are two possible explanations for this:

1. The light volume calculated from manufacturer specifications for brightness and runtime is inaccurate…
2. A significant amount of energy is lost to heat. This occurs when LEDs are operating near their maximum intensity.”

Expanding a bit on #2, resistive power loss happens all the time but is proportional to square of current draw, which show up as heat.  Higher current, lower efficiency.  P=I^2*R

It’s same reason AC power distribution is through very high voltage lines.

The higher lumens mode draw more current and decreases driver circuit efficiency from internal resistance.  This is illustrated well here, where driver circuit efficiencies are tested in isolation:

https://budgetlightforum.com/t/efficiency-measurements-of-a-few-drivers/68528

Looking forward to more test results, thanks for running these.

My personal opinion is it’s better to test at the most common use cases which will overwhelmingly be trail hiking, not SAR or emergency.  Based on your earlier matrix, 100 lumens is an overlap point between general trail hiking and trail running/bushwacking.

The Petzl had same lumen-hours as the Fenix despite a much larger battery.  Both are v1 model, ca. 2019.  Does this mean they were well used?  The Petzl LiI battery may have a poorer cycle life than the Fenix battery, or may have been cycled more often.  In my previous post, I showed examples of LiI suffering from cycle life degradation.

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