Olight SR51 Intimidator


Olight has made many lights, both small and large, this light here is one of the more powerful lights. The light is an update of the SR50, it has gotten a new and brighter led. The light has two brightness settings and strobe. The light is turned on by a side switch that also is used to change between levels (hold the switch down) and strobe (double click). Holding the switch down for some time will activate a lockout function. When locked out the light need 3 fast pressed on the switch to turn on. The light is made of aluminum with hard-anodized (Type 3) finish.

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The light is delivered in a aluminium case.


The box contains the light, two extra o-rings, a diffuser, a lanyard, a holster and a manual.

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The light has a OP (Orange peel) reflector with a XM-L led at the bottom. It has a solid steel bezel.

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As usual on high power lights it has some cooling fins and just behind the fins are the switch.


The battery connection in the head is reinforced with metal.

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Both front and back threads are square cut, they are also anodized but because both power connection are in the head this has nothing with lockout to do, but it is possible to do a mechanical lockout by loosen the body half a turn.


The body is cut with large rectangles to improve the grip.

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The tailcap is flat, i.e. the light can tail stand. In the tailcap there are two holes for a lanyard, one on each side.


Inside the tailcap is a plastic insert to press down on the battery carrier.


This light uses a battery carrier to hold the 6 batteries it needs. This is mostly plastic but does feel very solid. The batteries are connected as 3 parallel groups or 3 batteries each, i.e. the light is gets 6 volt from the carrier and triple the mAh.

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The carrier has 3 minus connections and one plus connection to the head. The plus connection inside the carrier to the batteries is recessed, providing a mechanical polarity protection.

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The supplied diffuser is in a rubber ring and can easily be mounted or removed.


The light also includes a holster


The holster looks like it is designed for multiple types of flashlights and for the SR51 the zipper must be down.


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

This light, like its larger brethern, has a solid feel and a good grip. The addition of a electric lockout function has improved the SR series, now it is easier to transport them safely. The good throw and a included diffuser does also make for a very versatily light. The only "problem" is the power supply, as delivered the light can only use CR123 or 16340 batteries, not 18650 (But it can be ordered as an extra).

Technical specification and measurements


This light is designed for 6xCR123 batteries and can also use 6x16340. With a extra battery carrier it is possible to use 2x18650. Because the batteries are used in 3 parallel banks it is possible to use less than a full load for low (see runtime graph).

Measured size and weight:
Length: 190 mm
Diameter: 43.7 mm to 63 mm
Weight: 506 gram with CR123

The light uses a Cree XM-L U2 cool white led.


In the above table I have collected all modes, measured at 5 volt. I have also included off as a mode, because the light uses a small amount of power. All the estimated runtimes are with 1400mAh CR123 batteries. The estimated lumen is scale from the specified maximum. The brightness is a relative measurement from a lux meter.
The specification does match very well with the measured/estimated value.


A voltage sweep at high shows a very nice stabilization. According to specifications the light will work down to 4.5 volt and this curve shows that it stabilizes down to 4.5 volt, then reduces output slowly down to 4 volt. The maximum current draw is 2.75 ampere, this is below 1 ampere for each battery. I.e. this light is not running the batteries to the edge.


At low it works down to 4 volt and only uses 0.5 ampere.


The runtime is mostly flat, the output drop between 4.5 and 4 volt do translates to a slow drop in output on high, when batteries are running low. When the batteries are nearly empty the light starts flashing.
The low runtime I did was with only two batteries in the light, i.e. with all 6 batteries it will be more than 3 times as long. From the 89 minutes low runtime on 16340 I would estimate the high runtime on 6x16340 to be about 38 minutes.
Note: The runtime I uses in the table is to 50% brightness, not the ANSI/FL1 recommandion of 10% brightness


Olight is sharing technology with 4Sevens and I was curious if SR51 did regulate down (like some 4sevens light) when it got hot. It was a bit difficult to get the temperature up, I had to wrap a towel around the light. As can be seen from the curve the light output and current consumption does drop with temperature, but not much. This does not look like a real temperature regulation, but then the light does hardly need a temperature regulation.


The light uses a 9.77 hz strobe with 45% duty cycle.


The light does not have any kind of pwm, but is does have a little bit of 10 hz noise in the light on low mode.

Comparison to other Flashlights

Olight SR51, Olight SR51 with diffuser, Olight SR90:
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Olight SR91, Olight SR92, Fenix TK35:
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For the full comparison to other lights with graphs and beamshots see here


The light was supplied by 4Sevens for review.
It is possible to get a 2x18650 battery carrier for the light.