Review of Xtar Wk21 with measurements and outdoor beamshots

HKJ

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Mar 26, 2008
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Copenhagen, Denmark
[size=+3]Xtar Wk21[/size]

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Xtar has made flashlights, batteries and chargers for some time. In this review I am looking at a small high power light, that uses a LiIon battery to drive a XM-L led.
The light is turned on/off and brightness changed by loosing and tighten the head. The light is made of aluminum with anodized finish.


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The light comes in a a small box with a foam insert.

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Included in the package is the light, a LiIon battery, a chain with claw and split ring, a manual and a warranty card.

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The light uses a smooth reflector with a XM-L led. With this small reflector and a XM-L led the beam will be mostly flood.

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The head has some groves for grip, but is not equipped with any cooling fins.

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The light has up to five modes, that can be selected with loosing/tightening the head. It will remember the last selected mode.

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A look at the head from the backside shows that there is a metal plate on the plus connection, but also show 4 small solder pads. Bridging any of these pads will disable one mode from the user interface, the only mode that cannot be disabled is high. How to do this is well explained in the manual. On the last picture I have disabled SOS mode and there is also some solder on strobe, but it is not bridged.

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The battery tube has triangular threads with anodized.

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Inside the battery tube is the usual spring.

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On the tube is a removable clip.

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The tailcap has a magnet below the round plate. The magnet is strong enough to attach the light to a fridge. The plate can be unscrewed and the magnet removed, for people that do not want a magnet.

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



The light is small and bright and has a lot of flexibility both for modes and for physical configuration with/without magnet and clip, but it is not designed for long runtime. I like this light, it is a nice EDC.



[size=+3]Technical specification and measurements[/size]

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The light is rated for use with one 16340 LiIon battery.

Measured size and weight:
Length: 71 mm
Diameter: 22.4 mm to 25.6 mm
Weight: 70 gram with Xtar 16340

The light uses a Cree XM-L T6 led.

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In the above table I have collected all modes. The current is measured at 3.7 volt. All the estimated runtimes are with a 600mAh LiIon battery. The estimated lumen is scale from the specified maximum of 500 lumens.

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The first voltage sweep is done in high mode. The light uses a linear current regulator, i.e. the current draw does not change with voltage.
Also note that the current draw has fallen to around 0 at 2.6 volt, this does give some protection for LiIon batteries.

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Reducing the brightness to medium with 40% pwm reduces the power consumption to about 40% of high.

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At low there is not much regulation, it is just low brightness.

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The light does not last long at high, it is better at medium, but this is definitly not the light to use for long runtime and lot of light at the same time (Larger batteries are needed for that).


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The strobe is 10 Hz and has a 50% duty cycle. It runs at full brightness.

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SOS is not really a SOS, it only sends SO, the last S is missing.

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The light uses pwm at 500 Hz to control brightness, here is medium.

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Pwm at low.



[size=+3]Comparison to other Flashlights[/size]

Xtar Wk21, Xtar Wk25B, Xtar Wk26:
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Sunwayman V10R Ti, Fenix LD15, Fenix E15:
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For the full comparison to other lights with graphs and beamshots see here




[size=+3]Notes[/size]

The light was supplied by Xtar for review.
 

Hoop

Enlightened
Joined
Dec 18, 2011
Messages
316
Location
Spokane, WA
That's cool you can disable modes.

So about the SOS: It does SOSOSOS instead of SOSSOSSOS eh? SOSOS is more efficient I think. :)
 

jgray3690

Newly Enlightened
Joined
Dec 4, 2011
Messages
20
Thanks for the review. I am looking for a small EDC light and
this is good info.
 

candle lamp

Flashlight Enthusiast
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Jun 16, 2010
Messages
1,572
Location
South Korea
Excellent review as always. HKJ! :thumbsup:
Looks like that you've used XTAR 16340 li-ion battery for runtime check. If so, is the capacity 750mAh?

I've seen the Selfbuilt's review as well and found his runtime graph on max.(high) mode isn't similar to yours.
Your graph on high is almost flat regulation, but Selfbuilt's is not.(The runtime to 50% brightness is also different.)
I think the runtime & its shape can be depend on the battery brand or life or capacity or manufacturing batch and so on.

But I'm curious if the reason is because of the different circuit in this case. :confused:
 

HKJ

Flashaholic
Joined
Mar 26, 2008
Messages
9,715
Location
Copenhagen, Denmark
Excellent review as always. HKJ! :thumbsup:
Looks like that you've used XTAR 16340 li-ion battery for runtime check. If so, is the capacity 750mAh?

I've seen the Selfbuilt's review as well and found his runtime graph on max.(high) mode isn't similar to yours.
Your graph on high is almost flat regulation, but Selfbuilt's is not.(The runtime to 50% brightness is also different.)
I think the runtime & its shape can be depend on the battery brand or life or capacity or manufacturing batch and so on.

But I'm curious if the reason is because of the different circuit in this case. :confused:

Yes, I did the test with the supplied Xtar battery and it probably has less capacity than specified. The light only runs 20 minutes at full brightness with about 1.2 ampere in current draw. That looks more like 400 mAh capacity (remember this is at 1.2 a current draw) at high enough voltage to drive the light at full brightness. A battery that sags more in voltage will give longer runtime, due to less current draw.
What I find very strange is that at full brightness my measurement shows stabilization down to 3 volt and at medium it only stabilizes to 3.5 volt, but the Wk26 works the same way.

It would be nice with some detailed test data on both Xtar and AW 16340 batteries, but I am not going to do that in the next few months (That time is reserved mostly for 18650 test).
 

selfbuilt

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Canada
A battery that sags more in voltage will give longer runtime, due to less current draw. ...
It would be nice with some detailed test data on both Xtar and AW 16340 batteries, but I am not going to do that in the next few months (That time is reserved mostly for 18650 test).
Yes, that makes sense. If the Xtar battery has less voltage sag than the AW protected RCR at those currents (and has lower capacity), that may explain the different pattern that I observed. FYI, I also did a runtime on AW IMR, and got a similar runtime pattern but with a longer flat-regulated period (i.e., about 15 mins instead of 10 mins), with only a slight increase in time to 50%. I will update my review with that graph when I get a chance later today.

Will be interesting to see the direct comparison of the Xtar and AW batteries in your test bed - but I can understand why all those 18650 tests are keeping you busy! :wave:
 

candle lamp

Flashlight Enthusiast
Joined
Jun 16, 2010
Messages
1,572
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Yes, I did the test with the supplied Xtar battery and it probably has less capacity than specified. The light only runs 20 minutes at full brightness with about 1.2 ampere in current draw. That looks more like 400 mAh capacity (remember this is at 1.2 a current draw) at high enough voltage to drive the light at full brightness. A battery that sags more in voltage will give longer runtime, due to less current draw.
What I find very strange is that at full brightness my measurement shows stabilization down to 3 volt and at medium it only stabilizes to 3.5 volt, but the Wk26 works the same way.

It would be nice with some detailed test data on both Xtar and AW 16340 batteries, but I am not going to do that in the next few months (That time is reserved mostly for 18650 test).

Thanks for your detailed reply. HKJ!

I got the following runtime with an AW RCR123A(black label).
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Considering your reply, I can assume AW RCR123A has more capacity and sag in voltage than Xtar. Xtar looks like IMR.
It's very interesting but curious the voltage at high is less than at medium brightness, and looks the circuit of the Wk21 may be same as Wk26.

Can't wait your upcoming 18650 test review. :)
 
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