Review: Wuben B2 - a budget-priced 21700 bike light


This Wuben B2 was provided by for review.


The Wuben B2 is a 21700-powered bike light. Far too many bike lights on the market use non-removable batteries, making them disposable when the battery wears out and making spare batteries impossible. The B2's use of a 21700 is enough by itself to stand out in the field. Its mount accommodates a variety of handlebars, and its efficient driver provides stable output in lower modes for a long time. The mount is reasonably secure, but it's important to press the light in firmly until it clicks, or it may fall, evidence of which is visible in some of the photos.

The B2 also differs from most bike lights in that it has a round beam. There are no hard cutoffs or other beam shaping to illuminate the road or trail while avoiding glare for other road users. That makes the B2 illegal for road use in some countries, such as Germany, and requires aiming the light carefully to be safe and courteous to others. Higher modes provide good visibility where color isn't important, but they throttle quickly regardless of wind or fan cooling.

For people on a budget who can accept a round beam, the Wuben B2 is conditionally recommended.



Spec -
Battery 1x21700, 1x18650
LED Osram P9
Color temperature 6589K
Color rendering index 71
Max output 1195 lm
Max throw 244m
Max sustainable output 566 lm
Max output at 50% battery 1187 lm
Best efficiency 167 lm/W @ 365 lm
Candela per lumen 12.5 (balanced)
Length 121 mm
Head diameter 36 mm
Weight 139 g
Weight with battery 213 g
Charging USB-C
Low Voltage Protection (LVP) 2.7V
Power from USB without battery Up to 470 lm
Lockout None
Approximate price $54 (21700 battery), $39 (18650 battery)
Rating ★★★☆☆ (conditionally recommended)


  • Good efficiency in all modes
  • No PWM flicker
  • Output is stable after throttling
  • One of a small number of bike lights with removable Li-ion batteries
  • Competitively-priced
  • Can run from USB


  • Round beam; bike lights should be shaped
  • Cool white, low CRI
  • Excessive throttling; sustainable output should be higher
  • Plastic TIR optic without a glass cover can scratch easily
  • No lockout
  • Confusing user interface

Details and technical analysis


The B2 comes in black, grey, and blue, and offers a choice of bundled 18650 or 21700 battery.


The B2 includes a bike mount, several rubber pads, a battery, an 18650 spacer, a USB-A to C cable, user manual, and spare O-rings. A taillight with a non-removable battery and MicroUSB charging was included in a box marked "Gift" suggesting it may not always be included with this model.

Modes and user interface


Mode Advertised Lumens Estimated Lumens Percent of claim Estimated throw (FL1 meters)
Low 200 185 93 97
Medium 400 365 91 134
High 1000 932 93 214
Turbo 1300 1195 92 244

Output is within 10% of claimed, and I'd consider that the margin of error of my test setup. Claimed throw is 280m, and what I'm seeing is a bit short of that.

User interface

State Action Result
Off Click On (last-used)
Off Double-click Blinking
On (l-m-h) Click Cycle modes l-m-h
On (l-m-h) Double-click Turbo
Blinking Click Off
Blinking Double-click SOS
Turbo Click l/m/h
On (any) Long-press Off

Output, runtime, and efficiency

Mode Estimated lumens Minutes to 80% Minutes to 50% Minutes to 10% Efficiency (lm/W) Current (mA)
Standby - - - 11 years - 0.05
Low 185 - - 17 hours 159 283
Medium 365 273 548 573 167 568
High 932 3.04 3.13 411 162 1870
Turbo 1195 1.06 1.17 283 153 2800

I was surprised that this light steps down so much and so soon given that it has more thermal mass than a typical EDC light and is air cooled during typical use. Perhaps it's meant to extend battery life, but if I want more runtime I'd rather select a lower mode myself.

Light quality

Readings are taken from the center spot diffused with DC Fix diffusion film using an X-rite i1Pro spectrophotometer.

Mode Color Temperature Tint Duv CRI CRI R9 (deep red) CRI R12 (deep blue)
Low 6423K 0.0046 (moderately green) 69.5 -41.6 45.7
Med 6589K 0.0038 (moderately green) 69.5 -39.9 46.5
High 6918K 0.0020 (slightly green) 70.8 -32.7 48.0
Turbo 6862K 0.0020 (slightly green) 70.8 -32.9 48.0

This is a very average spectrum for an LED light and I expect cyclists coming from other lights to have no complaints. Flashlight enthusiasts, however might hope for better color rendering and tint closer to sunlight. This isn't merely an aesthetic preference; bike lanes marked by red bricks, the distinction between mud and dirt, and of course distinguishing a stick on a trail from a snake are all aided by better color rendering.


Max, sustainable, and a cheap bike light with a shaped beam and SST-20 swap

B2 vs the cheap bike light to show beam shaping

Batteries and charging

The B2 is designed for a protected 21700 battery. It works well with a protected 18650 battery in the included adapter, but rattles severely without the adapter. Unprotected 21700s work, but rattle a bit and can cause flickering on very bumpy rides. An unprotected 18650 isn't long enough to make contact using the included adapter, but can be used with third-party spacers.

The 21700 battery charges in about 5 hours from any USB-C power supply, and the light operates without a battery from USB power up to 470 lm.

Modification potential

The retaining ring is easily unscrewed, giving access to the 29mm diameter TIR and LED. If a suitable elliptical optic could be found, that would be an improvement for this light. An LED with better color quality might also help, but it would likely reduce output, and the B2 does not need a reduction in its sustainable output.

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