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Verdict: 
Some doubts over the claimed visibility, but nonetheless an inexpensive and surprisingly bright contingency light
Weight: 
31g
BTwin VIOO 320 USB Dual Bike Light
8 10

The BTwin VIOO 320 Bicolour bike light is a reversible red/white LED with two modes. While I'm not totally convinced by BTwin's claims regarding visibility distances, at 22 and 7 lumens respectively, it's a surprisingly useful contingency light – the sort you might lend to a mate should one of their blinkies unexpectedly power down.

As the photos illustrate, it's a very compact design, although it occupies more handlebar space than some of the thimble-sized blinkies, such as the Lucas F-40 and similar. However, at £8.99, it's considerably cheaper.

> Buy this online here

Despite this, materials and build quality seem reassuringly good. Inside that familiar rubberised monocoque shell cum strap (which is very secure, although benefits from some gentle pre-stretch before being mounted to beefy bars) sits a single diode, lithium-ion battery and switchgear.

The battery is designed to serve 500 charge cycles, so at a conservative estimate that's at least three years' hard use and the retail giant's standard two-year, no-quibble warranty adds further peace of mind.

A full mains charge takes just under two hours and the diode emits a subtle red pulse during this phase. Similarly, when reserves dwindle, it flashes intermittently, giving 28 minutes and a sporting chance of getting home before powering down.

There's no IPX rating, but so long as you've reinstated the USB port cover properly, there's little chance of water/similar ingress getting inside. Cursory blasts from the garden hose made no impression either.

The simple top-mounted switch is intuitive to use, requires a definite two-second prod, and is easily operable in middle-weight full-finger gloves. Ours defaulted to white steady, another prod engages flashing, and two further nudges selects the red beams.

LED technology is improving all the time in terms of output and efficiency. Curiously, despite the disparity in power, both flashing settings are reckoned to achieve 9 hours from a full charge. Calling their bluff, I'm pleased to report 8hrs 54mins and 8:56, which should be accurate enough for all but the most pedantic.

Performance/visibility

As I mentioned earlier, in both settings, it's quite a potent little light, especially relative to some household names costing twice as much. The highest, 22-lumen front flash isn't quite a daylight mode in the sense of being visible to other traffic on brighter days. However, it's surprisingly useful when skies are overcast, thanks to the combination of pace and pure white diode.

Past dusk, oncoming traffic seemed to register at around 300 metres, not quite the 450 metres quoted, even along otherwise deserted lanes with starry skies.

This also compensated for the lens's relatively small peripheral punch around town. Even in the latter context, paired with my Univega's potent Exposure Revo dynamo lamp, the BTwin registered first. Distance-wise, by my reckoning it's between 150 and 200 metres. Again, short of those cited on the packaging, but good nonetheless.

The steady mode is quite piercing and reckoned to project a pool of light to 11 metres (36ft in old money). It's not intended as a light in the legally accepted sense but passable for tackling roadside mechanicals, map reading, pannier foraging and similar close detail stuff. Visible to 450 metres? Not by my reckoning, although, with main systems switched off, a very reasonable 200m is nearer the mark, and that's along unlit roads on clear nights.

> Buyer's Guide: The best front lights for cycling

The red, or rear, setting is brighter than 7 lumens would suggest, and again BTwin cites 300 metres in constant and flashing. Fellow riders concurred with my estimate of 200m in flashing, less around town; on the flipside, it's less intense at close quarters than some, so passable for group riding, although my generally diplomatic persuasion erred towards the constant setting.

Used thus, visibility is around 80 metres, dipping to 40 in suburban/urban settings – a few split-second stealth moments when exiting roundabouts left me slightly uncomfortable, although the same could be said for other bijoux models in a comparable context.

> Buyer's Guide: The best rear lights

When all's said and done, this is still a very capable contingency system and deserves a place next to the patch kit in a wedge pack.

Verdict

Some doubts over the claimed visibility, but nonetheless an inexpensive and surprisingly bright contingency light

road.cc test report

Make and model: BTwin VIOO 320 USB Dual Bike Light

Size tested: 22 lumen white, 7 lumen red

Tell us what the light is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

BTwin says:

"PRODUCT BENEFITS

Visibility Lights up to 11 m, visible from 450 m. Two-tone LED, flashing/continuous modes.

Autonomy 3h in continuous mode, up to 9h in flash mode. USB cable to charge (500 cycles)

Easy assembly / dismantling Universal, one step, tool-free attachment."

My feelings: Bargain LED that converts from reversible front/rear light at the push of a button. Output an lumens are relatively impressive given the asking price too.

Tell us some more about the technical aspects of the light?

Visibility B'TWIN has created the B'VISIBLE label to designate products that improve your visibility while cycling. It guarantees high-performance visibility that has been scientifically tested and approved in the lab, available on a full line of B'TWIN products.

Performance Battery capacity: 210 mAh.

Brightness:

- White mode: 22 Lumen,

- Red mode: 7 Lumen.

COMPOSITION / ADVICE

Composition

Structure

100.00% Styrene Ethylene Butadiene Styrene (SEBS)

Lens

100.00% Polycarbonate (PC)

Inside Shell - Main fabric

100.00% Battery - Lilo

Restricted use : Not a substitute for bicycle lights required by law

Rate the light for quality of construction:
 
7/10
Well made, especially for the money – certainly doesn't feel cheap.
Rate the light for design and ease of use. How simple was the light to use?
 
7/10
Rate the light for the design and usability of the clamping system
 
8/10
Good and secure, but showed some minor signs of indigestion on some oversized bars and seatposts.
Rate the light for waterproofing. How did it stand up to the elements?
 
6/10
Water-resistant in the everyday road riding sense. Two year warranty adds further peace of mind.
Rate the light for battery life. How long did it last? How long did it take to recharge?
 
8/10
Pretty good – 1hr 58mins zero to fully charged, and delivers nearly 9 hours in the flashing settings.
Rate the light for performance:
 
7/10
Much brighter than the lumens might suggest, but while quite potent, by my reckoning it's not the 450 and 300 metres cited.
Rate the light for durability:
 
7/10
Rate the light for weight:
 
8/10
Rate the light for value:
 
9/10

Tell us how the light performed overall when used for its designed purpose

Overall, the VIOO 320 bicolour light is a remarkably good contingency light that is surprisingly bright in both settings – at least in the being seen with sense. It's intuitive to use, generally well made and quick to charge; arguably, two could be the perfect companions to a tyre-driven dynamo on a commuter bike, or as contingencies when enjoying longer summer evening outings on the best bike.

Tell us what you particularly liked about the light

Super-compact, well made for the money and surprisingly bright.

Tell us what you particularly disliked about the light

Nothing, when everything's taken into account.

Did you enjoy using the light? Yes

Would you consider buying the light? Yes, as tertiary/contingency lighting.

Would you recommend the light to a friend? Yes

Use this box to explain your score

Cheap and extremely cheerful contingency lights that work surprisingly well in both modes.

Overall rating: 8/10

About the tester

Age: 43  Height: 1m 81cm  Weight: 70kg

I usually ride: Rough stuff tourer based around 4130 Univega mountain bike frameset  My best bike is: 1955 Holdsworth Road Path and several others including cross & traditional road

I've been riding for: Over 20 years  I ride: Most days  I would class myself as: Experienced

I regularly do the following types of riding: cyclo cross, commuting, touring, fixed/singlespeed, mountain biking

Shaun Audane is a freelance writer/product tester with over twenty-eight years riding experience, the last twelve (120,000 miles) spent putting bikes and kit through their paces for a variety of publications. Previous generations of his family worked at manufacturing's sharp end, thus Shaun can weld, has a sound understanding of frame building practice and a preference for steel or titanium framesets.
Citing Richard Ballantine and an Au pair as his earliest cycling influences, he is presently writing a cycling book with particular focus upon women, families and disabled audiences (Having been a registered care manager and coached children at Herne Hill Velodrome in earlier careers)