[Chenko]

for submission in the reviews section


I've been using the BT20 testing sample for two weeks now. It is the brand new illumination system by Fenix, specifically designed for biking use, and now the time came to share the impressions on it. We have come to know Fenix for their flashlights and headlamps made for tactical use, outdoor sports, exploration, search and rescue and other outdoor activities. The BT20 marks their entry in a whole new market segment: cycling, mountain-biking and bicycle touring. Let's see the outcome of the challenge took up by Fenix.


In all her beauty:



Contents of the package:
- BT20 unit
- 3 o-rings of different diameter to attach the BT20 on differently sized bars
- the 2x18650 battery pack with its nylon holster, which has two velcro straps for mounting purpose
- an extension cable to connect the BT20 to the battery pack
- a plastic bracket with nylon straps to attach the BT20 to an helmet





Fairly thorough equipment in my book.
As an accessory to be bought apart, the 4xAA battery pack is available too.


The battery pack seems well designed to be water-tight. A well placed o-ring and the screw-in closure system seem trustworthy. All the contacts are delegated to springs, so that most kinds of 18650s would fit.



A well visible signal helps to put the batteries the right way:



A nice design feature: it is not possible to close the battery pack the wrong way, the lid is made so as to be closed in one possible way only.


Time for first impressions: boy is this BT20… tiny!



Seeing preview pictures, without any dimensional references, I expected a much larger device. Well, this comes as a nice first welcome surprise if you ask me.


Handling it, the feeling is that of a compact and solid tool. The BT20 sure looks and feels well put toghether and nicely designed.





Surface finishing is very nice and seems quite impervious to scratching. The choice of the two tonalities is a very pleasant and characteristic aesthetic touch.


The body is attached to a rotating support that makes it possible to rotate the unit in the horizonal axis, with just the right level of resistance and excellent movement smoothness. It can be tightened, loosened or removed with a standard cross screwdriver.


The most interesting feature of the BT20 is probably the patented "dual distance beam system", a somewhat curious novelty. To put it simply, the brightness distribution of the beam has 2 spots: the most intense one is projected far for throw, while the other one is aimed to the closer lower part of the field of lighting. All this while mantaining a very large and bright spill, which is shifted in the vertical axis to better illuminate the ground. Fenix engineers could come to this result putting a fresnel lens in the upper part of the lens and molding the reflector with a in a peculiar way, other than placing a selective OP patch in the reflector section closer to the led.


A couple of pictures from the makers:



The interesting optics system of the BT20, with it's aggressive OP patch close to the led and the "fresnel lens" thing:



This is a beamshot I personally took, to which I added marks as to better show the peculiar BT20's beam. This is dedicated to all the passionate white wall hunters :-)






It is easy to recognize the off-center central spot and the secondary spot, which is much more obvious in real use thanks to its closer distance to the ground


In real use I have to say… it is as good as advertised! BT20's beam really is perfectly suited for biking. I'll let the pictures tell the story.
Fenix BT20 on HIGH (not TURBO):



Fenix TK41 on HIGH (not TURBO):



Petzl NAO in flood 70% + spot 70% setting:



Zebralight SC51W H1 (maximum brightness):



Zebralight H501W on HIGH:





The button, accessible on the upper part, is easy to operate. To be picky, the feedback it provides seems a bit lacking if the device is to be operated with thick gloves, such as the ones I use in winter time. On the other hand, a very appreciated feature is represented by the charge status communication by the means of the button's colored luminescence:
- from 100% to 50% of batteries' charge the indicator stays green
- between 50% and 20% the indicator turns steady red
- under the 20% range the indicator starts blinking red






Now that's a nice and very well implemented feature!


A potential issue seems to rise nonetheless, which was only spotted thanks to the prolonged use of the batteries before recharge: the BT20 reacts to dropping tension by (smartly) passing to a lower brightness setting, but since the UI sequence works in one way only (LOW-MID-HIGH-TURBO) it is a bit difficult to manually set a lower mode from the one in use while passing through an unsupported one. This happens because the BT20 could not leave the time to cycle through a brightness mode which it is unable to mantain at that battery drainage, before setting itself to the lower level. The potential mistake in that occasion is making two faster-than-needed clicks and inadvertently access flashing mode. This issue sure is irritating and is due to the way the UI was design, which is shared by some other of the recent Fenix flashlights that only sport a single electronic switch.


BT20 sure doesn't lack power. The available modes are as follow:
Low – 100 lumens - 21 hrs runtime
Mid – 300 Lumens - 6.5 hrs runtime
High – 450 lumens - 4 ore hrs runtime
Turbo – 750 lumens - 2 hrs runtime
Flash – 300 lumens - 21+ hrs runtime


Here are some beamshot of the differente brightness settings (I would like to clarify I personally find this type of picture utterly useless, yet they seem appreciated by some so I'm taking and posting them anyway):













I ride 10km (6,2 miles) at night everyday, the BT20 provides me with several weeks of use at the lowest level, which is bright enough even on the unlit trail I travel to get home. The good runtimes attest the efficiency Fenix's electronics are renowned for.


My personal opinion is that level spacing is less than optimal as it is now. In particular, the lowest mode being too bright, while the difference between MID and HIGH level seems negligible. A 30 - 100 - 300 - 750 lumens level spacing would have been preferred, providing with a lowest mode which would be more than enough to be seen by other drivers in well lit areas, mode which the BT20 as of now lacks. If it was to remain the same way, I would object the usefullness of the two central brightness modes, to the extent I would remove one of the two if you asked me.
Flashing mode alternates a medium speed blinking (about 2Hz) to a very fast strobe of "tactical" taste. I have to admit I fail to understand the choice: if the slower flashing could prove useful to be very visible (but it is too bright for that purpose anyway), the strobe just seems the perfect tool to trigger drivers' anger. I'm seriously puzzled by this choice and I hope it will be addressed in the BT20's final release.


Tint in my sample is a better than usual cool white, but considering the outdoor spirit of this piece of gear I would have encouraged the use of a neutral white led, closer to 4000k temperature (4* or 5* tint bin being optimal). Contrast, depth perception, natural colours' richness and easeness in distiguishing different surfaces would all have been boosted quite a bit, those being all quite important things when dashing on a uneven grounds. Cool white light renders grass quite similar to dirt, and light bouncing on haze is an exacerbated condition… at this high levels of power, a small loss in brightness in favor of tint would have been a wise choice.


All in all, the BT20 sports innovative design choices and terrific technical features, with a top-notch build quality (as deserved by the Fenix brand name), accompanied by some room for improvement that in any case won't affect the use of this unit for its intended purpose. I would recommend the BT20 without hesitation to any serious biker, it sure is an high-end piece of kit that will not disappoint the most discerning biker.