Originally posted: August 6, 2010
Last revised: September 19, 2010

Reviewer's Note: The M40A was provided for review by SUNWAYLED. Please see their website or for more info.

Warning: pic heavy, as usual

Manufacturer Specifications: (taken from the SUNWAYLED website) The M40A is part of a new series of lights launched by SUNWAYLED. This is the first shipping sample I have reviewed – I have previously reviewed engineering samples of the M10R, M20C and M40C. The M40A is a high-output MC-E light that runs on common AA batteries.

The light comes in a solid cardboard box with cushioned packing foam. Included inside the package were the light, wrist strap/lanyard, manual, warranty card, promotional insert, and extra o-rings. Note that no holster is included.

From left to right: Duracell AA, SUNWAYLED M40A, M40C, ITP A6 Polestar, Fenix TK45.

M40A: Weight: 247.0g (no batter), Width (bezel) 57.0mm, Length: 145mm
M40C: Weight: 258.5g (no battery), Width (bezel) 57.1mm, Length 156mm

As you can see, the light bears something of a resemblance to the 2x18650 M40C reviewed previously. I will point out key differences as we go along …

First of these is the styling – note the location of heatsink fins has moved, and the M40A features traditional knurling around the body/battery tube/handle. Knurling is reasonably aggressive compared to most made-in-China lights.

One comment about the anodizing – while I would consider my M40A sample to be excellent overall, but there is some mottling of the head of the light near the bezel, and a few fine concentric rings around the base of the head near the heatsink fins. While these are minor cosmetic blemishes, the earlier M40C/M20C/M10R I reviewed were all outstanding in comparison (i.e. flawless). The color has also changed slightly to more gunmetal gray appearance on my M40A sample.

The control ring is similar to the M40C, but with more pronounced detents at every level. As before, there are no identifying labels on the control ring. One small note – there is a bit of small gap between the control ring and the area containing the heatsink fins. And it looks like one of the control ring magnets is visible at the top of the ring (near the heatsink fins). Not necessarily a problem per se, but not something that was visible not on the M40C.

The M40A lacks the low-battery LED warning indicator present on the M40C.

Something that hasn’t changed – high quality machinist square-cut screw threads, anodized for head lock-out.

The light comes equipped with a MC-E emitter inside a fairly deep reflector. Shown above is a comparison to the M40C – although hard to tell in the pics, the M40A reflector is both wider and deeper than the main M40C reflector. The overall front opening width is similar on the two lights, but the M40A doesn’t have the ring of colored 5mm emitters.

Here’s another significant change – no clicky switch. On/off and mode switching is now controlled entirely by the control ring in the head. The M40A can tailstand.

This is where the light gets interesting – note the high quality 4xAA carrier. Unlike a number of competitors, the carrier is all metal. It is also reversible - you can insert it either orientation into the light handle. So as long as you put the batteries in correctly (well labeled inside the carrier), there’s no chance of accidentally reversing polarity. This is a creative design, and something I hope other makers pick-up.


I’ve recently moved, and haven’t had a chance to set up a proper beamshot closet yet, but here’s a quick comparison to the M40C, about ~1 meter from a white ceiling (both lights on Hi).

The deeper-cut bezel ring introduces the slight peripheral edging effect you see above, but this is not noticeable at regular distances. Overall spillbeam widths are similar, but the M40A has a more focused hotspot than the M40C (consistent with the deeper reflector).

UPDATE SEPT 19, 2010: I've added some additional lights to my 100-Yard Outdoor Beamshot Round-up, including the M40A. Check out that round-up thread for more details. Here is an animated GIFs of the relevant comparison to the M40C:

Scroll down for some throw and output numbers.

User Interface

On/off and mode switching is controlled entirely by the magnetic control ring in the head (i.e. there is no clicky on-off switch). As such, there needs to be a “standby” mode on the ring (i.e. where no light is produced, but a standby current is being drawn so the electronic circuit knows when you are switching modes).

The five control ring levels on the M40A are Standy - Lo – Med – Hi – Strobe, arranged clockwise if you have the light in hand pointed away from you. Like the M40C, the total traverse of the ring is ~1/2 the circumference of the light, and you can switch back and forth with ease one-handed. As mentioned previously, the detents feel more pronounced on my M40A than my M40C, increasing your confidence here of not accidentally switching modes.

As an aside, there is occasionally a brief flash of the emitter when the battery carrier makes contact upon tightening of the head – but only in standby mode. A similar flash was noted on my JetBeam RRT-2 Raptor, but in that case was present on all modes and all the time.

Thanks to the anodized threads, you can lock-out the light by a simple quarter-turn loosening of the head. This is very useful if storing the light for a period of time, or to prevent accidental activation. There are plenty of screw threads, so no risk of the head falling off by this slight loosening.

Standby/Parasitic Current

The parasitic drain of standby modes is always a concern, so I measured it on my sample: 96.5uA. Given the 4xAA batteries are in series, for 2000mAh Eneloops, that would translate into 2.4 years before fully charged batteries would be drained.

Not really a problem, but good to have the easy head lock-out anyway.


I could detect no signs of PWM flicker by eye or with my sound-card oscilloscope setup. I believe the M40A is current-controlled on Lo/Med.


Strobe was measured at a “tactical” (and nauseating ) 15.7 Hz.

Testing Method: All my output numbers are relative for my home-made light box setup, a la Quickbeam's flashlight reviews 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.

Throw values are the square-root of lux measurements taken at 5 meters from the lens, using a light meter, and then extrapolated back to estimate values for 1 meter. This is my standard way to present throw on these types of high output lights. The beams don't really have a chance to fully converge until typically several meters out.

Throw/Output Summary Chart:

As previously mentioned, the M40A out-throws the higher-output M40C. Overall, I would say throw and output of the M40A are quite typical for this class of light.

Output/Runtime Comparison

Although the outputs and runtimes are a bit less, the overall pattern of the M40A is remarkably similar to the 2x18650 M40C. Both lights have excellent flat regulation on Med and Hi (Lo not tested, but I expect the same there).

Despite the differing battery sources, both lights go into a continuous flashing/strobing mode once the batteries fall out of regulation. On the M40C, you get some advance warning from the LED warning light. On the M40A, you instead get a few warning flashes of the main emitter a couple of minutes before dropping out of regulation. These flashes rapidly increase in frequency until they become continuous strobing as the output drops.

Like the M40C, you can switch to a lower output mode to temporarily restore constant light. But typically, there isn’t much battery life left at this point, and the low-battery flashing will begin again soon.

UPDATE: Just added the L91 lithium (Energizer e2) runtime on Hi. An impressive run - nearly 2 hours, well regulated.
How does the M40A stack up to the competition?

The closest comparables are really the other AA-powered lights: the ITP A6 and the Fenix TK45.

On Hi, the M40A does remarkably well in one sense – comparable in output to the ITP A6, the M40A manages to squeeze almost as much regulated runtime on 4xAA Eneloops as the A6 does on 6xAA. Of course, the difference is what happens after the lights fall out of regulation – the A6 has a slowly decreasing output that continues for quite some time, while the M40A drops quickly into low-output strobing. And as expected, the much larger 8xAA Fenix TK45 remains the output and runtime champ on Hi.

On Medium, you can see the effects of the lower number of batteries on the M40A. Although impressively regulated, it can’t match the runtime of the 6xAA ITP A6 or the 8xAA Fenix TK45. Still, this performance is impressive from just 4xAA cells.

Potential Issues

Like the M40C, there is no slow drop-off in output once the batteries fall out of regulation – the main light starts flashing with increasing frequency over a couple of minutes, and then drops to low output strobing.

There is a parasitic standby current, although this is minimal in my testing (i.e. 96.5uA – or ~2.4 years). The light can also be easily and reliably locked-out with a simple twist of the head if you are concerned.

Preliminary Observations

As expected – based on my earlier testing of the other SUNWAYLED lights - the M40A is a well-made and impressive light.

Like the other early releases, build quality and attention to detail are excellent. The only minor point is that the anodizing has a few minor blemishes on my M40A sample – but not enough to detract from the overall appearance of the light. As mentioned earlier, the other samples I tested were all outstanding, while this one is merely excellent.

I’m particularly impressed with their 4xAA battery carrier – solid metal construction, clear labels, and reversible polarity (i.e. fits in either way). This is the best AA carrier I’ve seen so far. Probably the only thing extra I would have liked to see is a clicky switch option like the M40C.

The beam is similar to the M40C (i.e. nice wide spillbeam), but with a more defined hostpot with greater throw. The centre-beam “donut” effect is of course present on all MC-E lights, but it is less noticeable on the M40A than most lights I’ve tested in this class. Definitely a good job on the reflector as well.

Personally, I quite like the overall size and styling of the light. It fits comfortably in the hand, and is reasonably compact for the output. The control ring is similar to the M40C, but with more noticeable detents on my M40A sample. The standby current is negligible, and the light is easily locked-out by a simple head twist. Spacing of output levels is good IMO.

As with the M40C, the regulation and output/runtime profile is very good, consistent with a current-controlled light. The only drawback for me is at the end of the run – I don’t see the point for the constant flashing when the batteries fall out of regulation. A low-voltage warning flash feature is fine, but why loose constant output at this stage? I would think the low output is enough of a signal that it's time to change the batteries - I recommend SUNWAYLED remove this "feature."

In terms of performance, one thing I would like to highlight – the M40A actually exceeds the manufacturer’s specs (a pleasant change for me ). I find their emitter lumen estimates for each level to be very believable, and runtime on Sanyo Eneloops (2000mAh) matched or exceeded their specs for 2600mAh NiMH.

As with the other SUNWAYLED offerings, this is a well made light that shows considerable design and manufacturing expertise. I suspect the design, feature set, and performance will find favor with many here – especially as it based on commonly available AA batteries (and in a convenient 4x configuration).

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

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