4Sevens Maelstrom S12

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4Sevens makes many different flashlights, at the time of introduction the S12 is the brightest flashlight he makes (But brighter models has been promised). The light uses a large led and a special battery to get the high brightness in a small size. The user interface is very simple, there is no on/off switch, the button on the tailcap is only momentary on, to turn it permanently on the tailcap must be tightened. Turning on twice with a short pause between will change brightness between high and low.

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The light is delivered in a cardboard box with a window. The box has plastic insert to hold the light.


The content of the box is: Flashlight, lanyard with split ring, 2 spare o-rings, manual. I believe that 4Sevens has removed the lanyard from the box, because the light has no holes for a lanyard!
The package does not include batteries or charger, this has to be bought separately.

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The light has a smooth reflector with the big SST90 led in the center. As can be seen in the beamshot comparison this does not make it a thrower.

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The light has some knurling on the front part of the head, this is mostly for decoration. After the knurling there are some small heat sink fins, but this is not enough to keep the temperature down, the light will automatic reduce the brightness when it gets hot (See runtime curve).


Looking at the backside of the head there is a metal bump for connection to the battery and two chips on the circuit board (I expect that there are more chips on the other side).


The body (That is glued together with the head) gives a good grip on the light.


The threads between the battery tube and tail are square threads and there is an o-ring.


Looking into the tailcap cap it looks like any other tailcap, but there is no switch behind the circuit board, the spring is connected directly to the ring. The button on the back of the tailcap will move the circuit board, this is used for momentary on. Tighten the tailcap will make a stable connection between the ring and the battery tube, this is used to turn the light on.


The button on the tail is not a switch, but will move the circuit board in the tail a little bit, this is used for momentary on. This interface makes it very easy to use the light for fast flashes of brightness, but the user interface will change between high and low when doing this. This is not my idea of a tactical light.


The tailcap has a white dot that can be used to see how far the tailcap is turned, but the body does not have any marking that say when the light is in momentary mode, lockout mode or off.


The light is supplied with a holster.

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It is possible to use the holster with either bezel up or down. Notice the dent in the side of the holster, this will hold the light when it has bezel down.

Looking at this light there are a lot of details I think could have been better: UI that changes level when flashing the light, very aggressive thermal regulation, "low brightness" due to regulation. What I really like about the light is the small size with high brightness. It is also a nice detail that the batteries are standard batteries, although not very common.

Technical specification and measurements


This light is designed for 26650 LiIon cells with protection, this is not a common cell size for flash lights and 4Seven has produced his own cells for the light. These cells are much cheaper than the usual custom batteries.

Measured size and weight:
Length: 139 mm
Diameter: 31 mm to 46 mm
Weight: 250 gram with battery.

The light uses a Luminus SST-90 led.


The measurements are done at 3.7 volt and for high I have measured both with a cold and a hot light. The estimated lumen are scaled from the specified lumen. The measured runtime is to 50% brightness, but is not really useful, because the light runs a long time below 50% (See runtime chart). Because the light is not fully stabilized the power will change with battery voltage, at 4 to 4.2 volt it is 18 watt on high.


I have done two voltage sweeps, one where the light had time to cool down between each measurement and one where it was running for 10 minutes at full brightness, before I started measuring. As can be seen the light does not really stabilize the brightness, except when the light is hot and it runs with reduced brightness. The light turns off at 3 volt, this gives an extra level of battery safety.


The runtime chart also shows the missing regulation and the temperature regulation. With no cooling the light will drop to about 50% brightness within a few minutes, with good cooling (I used a fan), the light will drop slowly, following the battery voltage.
Without cooling the light will have a much longer runtime, because it is running at a lower brightness.

The light uses current control and has no flashing modes.

Battery and charger

Because this light uses a uncommon battery size 4Sevens is also selling battery and charger for this light, but it is possible to find batteries and chargers from other manufacturers.

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The battery has a diameter of 27.7 mm and a length of 70 mm. The extra length compare to the specified 65 mm (26650) is due to added protection circuit and button top. The copper from the protection pcb can be seen as the minus pole on the battery.
The capacity is specified as 3900 mAh, but the real capacity is higher.



I have done a full review of the charger here:

Comparison to other Flashlights

4Sevens Maelstrom S12, Fenix TK35, Fenix TK40
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Sunwayled M40C, Crelant 7G3 XML T6, Olight M31 Triton
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For the full comparison to other lights with graphs and beam shots see here.

The included lights are: