Spark SL6-740NW

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Spark started with headlamps, and has added some flashlights to their lineup. This light is a high power XM-L light. The SL6-740NW has 5 brightness settings and both a side and a tail switch that are wired in parallel, i.e. they work exactly the same. The light is made of aluminum with hard-anodized (Type 3) finish.
Note: This is the neutral white version of the light, it also exist in a SL6-800CW that is slightly brighter and cool white led.


The light is delivered in a soft cardboard box with foam insert.


The box contains the light, two extra o-rings, a diffuser, a holster and a general instruction sheet that has specifications for all flashlights models.

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The light has a LOP (Light orange peel) reflector with a XM-L led at the bottom. It has a thin aluminium bezel. A diffuser glass is supplied with the light, this can replace the original front glass for a broader beam (See beamshots).


As usual on high power lights it has some cooling fins and it also has a switch on the head.


The battery connection in the head is with two springs, the center spring is for the battery connection, the outer spring is for the tail switch.

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The threads on the battery tube are of the triangular type, both at the front and back, both are sealed with a o-ring.
Because the threads are anodized, it is possible to lock-out the light.


The body does not have knurling, but only some groves.


The light includes an optional clip.


The battery tube has a inner sleeve, that is used to transfer the tail switch signal.


The tailcap has a spring for the battery connection, there is also two rings, one for battery power and one for the switch.


The switch in the tail is countersunk, to prevent accidental activation and allow tailstanding.

The user interface has multiple operating modes (These function can be activated on either switch):
  1. A short click will turn the light on in last selected mode or off.
  2. A slightly longer press from off will momentary turn the light on, it will turn off again when the switch is released.
  3. A long press will start brightness selection, first low, then medium 1, medium 2 and high, this sequence will be repeated until the switch is released, the selected brightness is remembered. This function can be activated from both on and off.
  4. A double click will activate super mode, use 1 or 3 or wait 5 minutes to get out of it.


A holster is included with the light. The light can be used both bezel down or bezel up, but the best fit is with bezel up.


Here is all the part the light can be disassembled in without tools.

This light is not a tactical light, but more general purpose light. It has a very good stabilization with both a buck/boost regulator, the two switches makes it possible to activate it in both under hand and over hand position. Hiding the super mode is probably a good thing for battery life and heat, you will only activate it when you really need it. The included diffuser makes it possible to use the light for either flood or throw. I do also like the small and lightweight design.

Technical specification and measurements


This light is designed for 2xCR123 and 18650 batteries. All sizes of 18650 will work from 65 mm to 70 mm long with button or flat top.

Measured size and weight:
Length: 125 mm
Diameter: 23 mm to 31 mm
Weight: 112 gram with CR123 and 126 gram with AW18650-26

The light uses a Cree XM-L T5 neutral white led.


In the above table I have collected all modes, measured at 3.7 volt (i.e. with 18650 battery). I have also included off as a mode, because the light uses a small amount of power. All the estimated runtimes are with a 2600mA LiIon battery. The estimated lumen is scale from the specified maximum. The brightness is a relative measurement from a lux meter and scaled from the specified 740 lumen.
The specifications does match very well with the measured/estimated value, except the low runtime probably is to optimistic.


A voltage sweep at super high shows a very nice stabilization, this light has a buck/boost regulator! The sweep also shows that the light uses a lot of current, up to 5 ampere. Not all batteries can supply that, check my 18650 roundup to find useable batteries.


High does also show a good stabilization and here the current consumption is down to a maximum of about 3 ampere.


The two medium and the low level continues with the good stabilization.
Also note that all the curves stops at about 2.4 volt, this makes the light mostly safe to use with unprotected LiIon cells. The 2900 mAh cells that can be discharged to 2.5 volt will be completely safe to use in this light, even in unprotected version.


With this kind of stabilization the runtime curve can only be flat and it is. The light shows a very fine runtime on both CR123 and 18650 batteries.


The super mode boost the output for 5 minutes. As can be seen on the curve the output drops due to heat, but when the light returns to high it will cool down and output increase again. Note: This test was done with a fan to cool the light (I am using same brightness scale on this curve as on the runtime curve).


The light do not have pwm, but the low levels do have a lot of high frequence noise in it.

Comparison to other Flashlights

Fenix TK21 U2, Klarus XT10, Spark SL6-740NW
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Spark SL6-740NW with diffuser, OLight M20S S2, OLight M20S S2 with diffuser
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For the full comparison to other lights with graphs and beamshots see here