There have been many debates on r.b.t. regarding bicycle lights and beam
shapes. For those of us whose rides combine both unlit trails or
multi-use paths, plus regular roads (with or without street lights), a
single beam light can be an unacceptable compromise.
Vehicle headlights either have one sealed beam with two separate bulbs
or two entirely separate lamps to accommodate different conditions. For
a bicycles there are a few lights with one spot beam and one flood beam,
but this is not really the same as high beam and low beam though by
mounting the light with the beam aimed slightly down it could be close
enough.
Back in the olden days, of MR-11 and MR-16 based bicycle lights, you
could choose different combinations of beam shapes since these lamps
came in a huge variety of intensities and beam angles. The LED versions
of these lamps have a lot fewer beam angles available because of the
difficulty of LED optics versus incandescent optics (see
<
http://spie.org/x47766.xml>). MR16 LED lamps are easily available in
wider angles, but for narrow spot beams they begin using large numbers
of lower power LEDs in a single lamp.
There are a lot of multiple beam bicycle LED lights but most of them are
just multiple beams that are exactly the same. They use multiple beams
to effectively manage thermals as the total power increases to levels
where it's too difficult to do passive cooling of a single LED. The
lamps are have the same optics and cannot be independently aimed.
Presently I use “manual aiming” with an adjustable spot to flood light
but it would be nice to have a dual beam light with one spot and one
flood beam, even better if they are independently aim-able.
Here are some lights that may be acceptable bicycle-specific lights that
I've found:
Nite-Lumen BC-A2 Windrunner Far-And-Near
Power Source: 4 x 18650
Claimed Lumens:
High: 1100
Medium: 5871
Low: 801
Review: <
www.youtube.com/watch?v=7WL2JgJhrJo>
Source: <
www.gearbest.com/led-light-bulbs/pp_136062.html>
Price: $43
Comments: This light has two different LED types, and two distinct
reflectors. The lamps are not individually aimable.
2 in 1 CREE XM-L L2
Power Source: 6 x 18650
Claimed Lumens:
High: 2000
Medium: Not Specified
Low: Not Specified
Source:
<
www.ebay.com/itm/2in1-CREE-XM-L-L2-LED-2000Lm-Front-Bicycle-High-Low-Beams-Lights-9600mAh-Battery/261449138971>
Price: $42
Comments: This is essentially two separate lamps with different optics
that can be independently aimed. It uses a Y cable from one battery. It
may just be a diffuser lens on one lamp, rather than a different reflector.
Each beam also has a separately controlled "ring light" that can be
steady or flashing. This might be a nice feature when you want a lower
power flasher for night use, combined with the steady main beam.
Fenix BT20
Power Source: 2 x 18650 (not included)
Claimed Lumens:
Low: 100 Lumens
Mid: 300 Lumes
High: 450 Lumens
Turbo: 750 Lumens
Strobe: 300 Lumens (nice to have a more reasonable level for the strobe)
Review: <
www.youtube.com/watch?v=ABmwlrFWNOk>
Price: $90 (not including batteries)
Source: <
www.fenix-store.com/fenix-bt20-led-bike-light/>
Comments: This light is a single beam but the optics create a dual beam
that combines spot and flood but it's only one LED so you can't choose
(see
<
http://cdn1.bigcommerce.com/server4500/12psl01c/products/1270/images/8224/201312510052961292__09342__18217.1443047637.1280.1280.jpg?c=2>).
For those terrified of CCBLs (Cheap Chinese Bicycle Lights) Fenix is a
well-regarded LED lighting company.
Ding (not yet available, Kickstarter finished, in pre-production)
Power Source: Internal battery
Claimed Lumens:
Mode 1: Hyper, 400 Lumen Froward, 150 Lumens Downwards
Mode 2: Track, 300 Lumen Forward, 125 Lumens Downwards
Mode 3: City, 200 Lumen Forward, 100 Lumen Downwards
Mode 4: Flasher, 150 Lumen Forward, Flash 100 Lumen Downwards
Mode 5: Daytime, 170 Lumen Forward, Fast Flash Downward Beam OFF
Source: <
http://www.dinglights.com.au/>
Price: $50 (AUD $70)
Comments: This light has two front lights with different optics (spot
and flood) and a third beam pointed down, an interesting "being seen"
concept. This is not a CCBL, it is a CABL (cheap Australian Bicycle Light).