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B'Twin VIOO 520 USB front light



Surprisingly potent, funky looking and frugal, but very much a secondary/back up light

At every product is thoroughly tested for as long as it takes to get a proper insight into how well it works. Our reviewers are experienced cyclists that we trust to be objective. While we strive to ensure that opinions expressed are backed up by facts, reviews are by their nature an informed opinion, not a definitive verdict. We don't intentionally try to break anything (except locks) but we do try to look for weak points in any design. The overall score is not just an average of the other scores: it reflects both a product's function and value – with value determined by how a product compares with items of similar spec, quality, and price.

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The B'Twin V100 520 front light is a safety model with decent output and really distinctive, battery sipping flashing modes. However, lights with proper lenses are better bets if you want to be seen round town.

Given the cube shape and funky colour, the V100 520 could easily be the result of a passionate tryst between Knog's Blinder 4 and Gecko series. Inside the reassuringly thick rubberised body-cum-bracket lives four perky diodes and a lithium-polymer cell charged through a USB socket, reckoned to enjoy a lifespan of approximately 500 charge cycles before becoming bin fodder.

USB rechargeable lights are usually highly water-resistant rather than fully waterproof. However, the port on the V100 520 is well sealed and a two year warrantee should render other misgivings academic. It takes 2.5 hours to charge from a wall charger, ten minutes or so longer from a laptop or similar.

The straps can be a weak spot on rubbery one-piece lights. Thankfully, these have retained their elasticity despite being regularly ported between standard and oversized bars.

Powering up is simply a matter of depressing the reassuringly positive centre mounted switch for two seconds whereupon it defaults to steady mode. Subsequent prods engage the distinctive flashing and strobe patterns. Unless you get very unlucky it's unlikely to turn on wile it's in your posket or bag. Conversely, toggling down on the fly requires practice, especially wearing winter weight gloves.

The steady mode is certainly bright. It manages 3:27 and in a pinch, it's adequate for limping home following main system failure.

Indeed, urbanites might find it adequate for pub scoots, or hustling across town when paired to a second flasher. The first of these extrovert settings oscillates quite aggressively and B'Twin reckon visibility is 600 metres plus.

Perky diodes cast these further than expected but I'd say the reach is nearer 450m on a very clear night and 250m through neon-soaked town centres.

Two disco-strobe patterns are captivating and unique, and therefore brilliant for nailing driver attention when entering traffic flow or getting noticed by pedestrians using shared paths. Ours have returned between 14:27 and 15:19, fully charged. Only the slowest, pulsing mode has managed 17 hours.


Surprisingly potent, funky looking and frugal, but very much a secondary/back up light

The light comparator

If you have a nice big screen you can click here for the widescreen version (1400x1000px) test report

Make and model: BTwin VIOO 520 USB front light

Size tested: n/a

Tell us what the product 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?

"Cyclists wanting to improve their visibility, day or night, using a powerful and identifiable rechargeable light. Front light for visibility, rechargeable via USB." Broadly agree.

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


o Lights up to 15 m, visible from 650 m. 4 LED, 5 flash modes, 1 continuous mode.




o 3.5 hr/continuous mode, up to 17 hr/flash mode. Charge with mini USB cable 500x.



o Universal, one step, tool-free attachment.

4. Guarantee : 2 Years

Rate the product for quality of construction:
Rate the product for performance:
Rate the product for durability:
Rate the product for weight, if applicable:
Rate the product for comfort, if applicable:
Rate the product for value:

The market is getting more competitive every season. While not quite a bargain, it's certainly good value.

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

Overall, I've been very impressed by the V100 520. B'Twin have sidestepped the lumens race in favour of perky diodes and distinctive patterns, which seems an extremely effective formula for secondary lighting.

Tell us what you particularly liked about the product

Funky, compact design and super-effective modes.

Tell us what you particularly disliked about the product

Nothing of note.

Did you enjoy using the product? Yes.

Would you consider buying the product? Yes.

Would you recommend the product to a friend? Generally speaking, yes.

Overall rating: 7/10

About the tester

Age: 40  Height: 1m 81  Weight: 70 kilos

I usually ride: Rough Stuff Tourer Based around 4130 Univega mtb 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, mtb,


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)

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Urban_Manc | 9 years ago

I'd give these lights 10/10 , high intensity, great battery life, I can't fault them especially for the £12 sale price I bougnt them for.

I use them as a secondary flashing light to my main steady one.



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