Olight M31 (SST-50, 2x18650/18500, 3x-4xCR123A/RCR) Review: RUNTIMES, BEAMSHOTS +

Originally posted: December 24, 2010

Warning: pic heavy, as usual. :whistle:


The Olight M31 has been out a little while, although I am just getting to it now. How does it compare to other offerings in the high-output space? Scroll on, gentle reader ... ;)

Packaging is similar to other high-end Olight lights. Inside the plastic carrying case with closing flaps, everything is firmly secured in cut-out foam. You will find the light with battery extender tube, manual, battery carrier, spare o-rings, and belt holster.

From left to right: AW Protected 18650, Olight M31, M30, Jetbeam M1X, Fenix Tk45, Eagletac M3C4.

From left to right (with extender): AW Protected 18650, Olight M31, Jetbeam M1X, Thrunite Catapult V2, Lumapower MVP P7.

M31 no Extender: Weight: 258.1g (no battery), Length 209mm x Width 62.3mm (bezel)
M31 with Extender: Weight 275.1g (no battery), Length 245mm x Width 62.3mm (bezel)

As you can see the M31 is larger than the earlier MC-E-based M30. The main reason for this is the much larger head, with a wider and deeper reflector.

Build quality is very good. The overall shape and design is similar to the M30, only with a larger head and traditional tailcap.

The M31 comes with black finish type-III (hard) anodizing. Rather than traditional knurling, the M31 has a raised checkered pattern to help with grip. I typically find Olight lettering is bright and clear, and the M31 is no exception. Both the bezel opening and tailcap have raised scalloped edges. Like M30, the M31 can also tailstand.

Screw threads are not anodized on the battery tubes, but there is anodizing on the tailcap screw threads. So lock-out is possible, although it may not be as robust as where both sets of threads are anodized. Note that is a definite improvement over the M30, where no lock-out was possible as they needed to keep a constant current path for the tailcap side-switch.

The attached clip can be removed by unscrewing the retaining ring above it and pulling the clip off.

The tailcap switch is a typical forward clicky, with good feel. The light can tailstaind.

The included 3xCR123A/RCR battery holder is optional Ė you donít need to use it in this configuration, but it does remove battery rattle if you choose to. The bore width of the body tube is wide enough to accommodate protected 18500/18650, so thinner CR123A cells are prone to some rattle. At the very least, it makes a good storage holder for an extra set of cells.

Note the spring in the head, so high capacity flat-top batteries can be used.

All in all, a very nice build. :)

The M31 features the Luminus SST-50, with a large and smooth reflector. This should translate into good throw.

Which brings us to the requisite white wall hunting ;). All lights are on Hi on 2x 18650 (6xCR123A in the case of the M60R Ė mislabelled as M60C). Bezels are about ~0.75 meter from a white wall (with the camera ~1.25 meters back from the wall). Automatic white balance on the camera, to minimize tint differences.

Note:I accidentally mislabeled the M60R images and M60C in the pics below Ė sorry. :shhh:

From now on, all my beamshots will be taken in this standard configuration, to facilitate comparisons.

Ok, so the M31 can throw! There are specific details in my Summary Tables further down, but the M31 is the best throwing SST-50 Iíve seen yet. :ooo:

I've recently updated my 100-Yard Outdoor Beamshot Round-up, including the latest M31. Check out that round-up thread for more details on the testing method, plus higher quality JPEG images of all lights. For now, here is an animated GIF of some relevant comparisons:

User Interface

The M31 has the classic Olight M-series interface (different from the distinctive M30).

As always, on/off is controlled by the tailcap clicky (press for momentary on, click for lock on).

You move between modes by a simple switch of the head - loose/tighten the head to move to the next state. Sequence is: Lo - Med - Hi - Strobe, repeated in an endless loop. Light features mode memory, and retains the last setting used (so you can always have it come on where you want).


There is no sign of pulse width modulation (PWM) on any output mode - I believe that the light is current controlled. :)


Strobe was measured at a fairly typical 9.8 Hz.

Testing Method:

All my output numbers are relative for my home-made light box setup, a la Quickbeam's flashlightreviews.com method. You can directly compare all my relative output values from different reviews - i.e. an output value of "10" in one graph is the same as "10" in another. All runtimes are done under a cooling fan, except for any extended run Lo/Min modes (i.e. >12 hours) which are done without cooling.

I have recently devised a method for converting my lightbox relative output values (ROV) to estimated Lumens. See my How to convert Selfbuilt's Lighbox values to Lumens thread for more info.

Throw/Output Summary Chart:

Effective November 2010, I have revised my summary tables to match with the current ANSI FL-1 standard for flashlight testing. Please see http://www.sliderule.ca/FL1.htm for a description of the terms used in these tables.

So, the M31 has the distinction of having the highest output AND the greatest throw of any SST-50 light in my collection. :party:

Lo level is reasonable for this class of light, but is not as low as some of the competition.

See my runtimes below for info on the relative output levels.

Output/Runtime Comparison:

Note: Effective January 2010, all CR123A runtimes are now performed on Titanium Innovations batteries. You can compare the performance of these CR123A cells relative to the Duracell/Surefire cells used in my earlier reviews here. These new light results are marked by an "*" in the graph legend

Output/runtime efficiency is excellent on the M31, at all levels and on all batteries. Basically, exactly what you would expect from a good current-controlled light - no surprises. :thumbsup:

On the primary CR123A Hi mode tests, you will note the light stepped down early into the runs (i.e. just like my Catapult V2 SST-50). This is likely due to a thermal sensor, designed to protect the light from overheating cells. A reasonable safety precaution, and one I'm glad to see.

Potential Issues

Light is heavily driven on Hi, so you should use this mode sparingly (especially on anything other than 2x18650). Heatsinking may not be as extensive as some other lights in this class.

Light is a bit top heavy, with the large head and reflector.

Strobe mode is included on the main sequence.

There is no bundled diffuser with the M31, unlike other M-series Olights.

Preliminary Observations

The M31 is a very impressive high-output light. I'll cut right to the chase - it has the highest output and throw of any SST-50 or MC-E-based light in my collection at the moment. :ooo:

The M31's reported 800 lumen ANSI FL-1 spec is actually believable in my testing. This is the first time I can say that for a SST-50-based light (i.e. most of them are closer to ~600 estimated lumens). Of course that overall output difference won't be too noticeable in practice (can you easily see the difference between 6 and 8 lumens? Or 60 and 80 lumens? Again, the same applies for 600 and 800 lumens).

But what you will definitely notice is the greater throw of the M31. As my center-beam testing and outdoor shots show, this is the best thrower I've come across for this class of light. While I personally like a more floody high output light most of the time, I know a lot here prefer the heavy throwers. :thumbsup:

The interface is good, except for the strobe mode on the main sequence. :sigh: Still, I much prefer this over the M30's low freq PWM. I also like the ability to lock-out the light at the tailcap now.

I particularly like the wide battery flexibility, both with the extender (i.e. 2x18650, 4xCR123A/RCR) and without it (i.e. 2x18500, 3xCR123A/RCR). Note that it is rather highly-driven on Hi, so I recommend you stick with 2x18650 in you want to run that way. As the runtimes show, it is not really feasible to run on Hi in 3x or even 4x primary CR123A.

In fact, that brings me to my main concern with the light - it is a bit lightweight for this class, and I worry about the heatsinking capabilities. I note the manual similarly cautions about this, and warns not to run for extended periods on Hi.

At the end of the day, this is a very impressive light in the high-output class - it has the highest output and furthest throw I've seen yet for a SST-50-based light. With appropriate common-sense about battery configurations on Hi, I think you will find it a very worthwhile contender. :)


M31 provided by Batteryjunction.com for review.

To follow the online discussions for this review, please see the full review thread at CPF.

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