Gemini Duo front light – review

Incredibly bright, user-programmable front light

The Gemini Duo packs an incredible punch considering its tiny footprint.

With four user-programmable settings, pumping out anywhere between 150 and 1,500 lumens, and superb battery life, the Duo, which sits second-from-top in Canadian firm Gemini’s range, is a versatile number most at home on unlit country lanes and, at £179.99 for the model on test, it’s good value up against comparable lights from rival brands.

The Gemini Duo has a maximum output of a claimed 1,500 lumens

High-powered lights typically come in two moulds: the all-in-one unit with a self-contained battery, like the Exposure Strada currently on test, and those which separate the light itself from the battery pack, like the Gemini Duo.

Both designs have their pros and cons. The 800-lumen Strada takes up considerable real estate on the handlebar but, at 228g, is lighter than the Duo and it’s all-in-one design is a neat solution for a high-powered light, while the Duo requires the rider to strap the 229g battery pack to the toptube and connect it to the 63g light unit via a DC cable which runs from the back of the light and plugs into the appropriate connection from the battery pack.

The battery is kept in a soft case bag which securely straps to the toptube using velcro. We occasionally found that the battery pack slipped a little towards the rider on a compact frame with a sloping toptube, where it was then liable to brush the inside of the thighs when climbing out of the saddle. Still, while the external battery pack may put some riders off, it wasn’t of great concern to us and contributes significantly to the Duo’s impressive run times.

The Duo is powered by an external battery pack

Up front the Duo’s head unit is tiny and sits inconspicuously on the handlebar. The unit itself is made from machined aluminium and attaches to the ‘bar via a silicone o-ring which provides secure attachment while allowing the rider to adjust the angle of the beam on-the fly to avoid dazzling oncoming cards. The o-ring attachment also means the Duo is quick and easy to move between bikes and Gemini provide two, of different sizes, to account for handlebars with a traditional 26mm diameter and those, as is normally the case now, that are beefed up to 31.8mm. Gemini also supply a helmet mount though this will more likely appeal to those who ride off-road or serious night riders heading out for long excursions under cover of darkness.

The Duo gets its name from the two Cree XM-L2 U2 LEDs housed in the unit. They emit an incredibly clean light and the beam pattern throws a even spread of light across the tarmac to offer excellent peripheral vision on unlit roads.

The Duo has four settings – low, medium, light and flashing – and each can be programmed, allowing the user to pick from ten levels of brightness between ten per cent and 100 per cent. We ran through how to programme the light in our first look and Gemini’s instructions are easy to follow. It’s an excellent feature which allows the rider to harness as much or as little of the light’s power as necessary. We settled on 10 per cent, 50 per cent and 60 per cent for our low, medium and high settings, equating to 150 lumens for commuting through London’s well-lit urban sprawl, and 750 lumens and 900 lumens for night riding. We rarely needed 900 lumens, only switching to the highest setting on the darkest lanes with no traffic, and if you only need a light for road riding then you’re unlikely to unlock the Duo’s full potential. However, if you also ride off-road at night – whether that’s cyclo-cross or mountain biking – then the world’s your oyster.

The single button is easy to operate when wearing gloves

Gemini sell the Duo with a choice of two battery packs. The two-cell battery pack is smaller and cheaper at £154.99, while the four-cell option we tested is £20 more at £174.99 and doubles the run times. The two-cell battery weighs 122g, while the four-cell battery is 229g. The four-cell battery’s run times are very impressive, ranging from a claimed 34 hours on 10 per cent power to three hours on full power. There, in a nutshell, you have the main benefit of an external battery pack. Gemini list battery life and lumen output for each of the ten beam settings on their website, which is helpful for when programming the light. The battery is charged by plugging the pack into the supplied mains charger so, unlike USB (when you can charge from any computer providing you have an appropriate cable), there’s no opportunity to add some juice unless you have that with you, but the battery life is generous enough that you’re unlikely to ever be caught short.

The light is operated by a single rubber button at the rear of the unit. Turn the light on with one click, use the button to cycle through the three low, medium and high modes, and hold the button down to turn the light off. Flashing mode isn’t part of the main cycle. Instead turn the light on by holding the power button for one second, rather than just with a single click. The button itself is easy to use when wearing gloves and the fact it doubles as the battery life indicator (showing green when there’s 100-20 per cent charge remaining, amber when the charge drops to 20-10 per cent and red when there’s less than 10 per cent juice left) means there’s no fumbling in the dark when trying to switch between settings.


Light technology has come a long way in a short time and the Gemini Duo is a case in point. It’s undoubtedly a premium option but is very competitively priced considering the lumen output and battery life – both of which are superb. Not everyone will want an external battery pack but it ensures impressive run times and means the light itself sits inconspicuously up front.

In truth, it’s likely to be too powerful for those who only ride on the road, and Gemini’s 950-lumen Xera (£129.99/£149.99) is an alternative worth exploring, but otherwise the Duo is an incredibly bright, versatile light for riders who want to turn night into day.

Discuss in the forum

Price: £154.99 (two-cell battery), £174.99 (four-cell battery)
Website: Gemini Lights
UK distributor: i-ride


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