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The Cateye Volt 400 Duplex is a well-thought-out light able to cover a multitude of use cases with a few add-on accessories, unfortunately let down by some battery information omissions. Overall, though, a recommended buy with a two-year warranty.
The Volt 400 Duplex arrives with a helmet mount, secured by a loop of Velcro-like material that doubles back on itself. This works well enough, but I was disappointed with the small footprint of the pad that contacts the helmet – the lack of material fore and aft meant that on some helmets without a pronounced centre ridge, the light vibrated rapidly up and down when cycling over rough surfaces. This made a quick blast along a stretch of bridleway akin to cycling in a disco, and were I to implement this as a long-term solution I'd be adding a plastic extension underneath to steady things.
At 136g including mount, and sitting quite high, the Volt 400 is noticeable atop your noggin, but it's not unreasonably wieldy. If you need to remove or place it back on while wearing your helmet this is do-able with some practice.
Selling with just a helmet mount, the Volt 400 does not meet the UK's Road Vehicle Lighting Regulations – the legal document that defines what lights you need to have on your bike by law – so don't view this light as a replacement for lights that are actually affixed to your bike, front and rear. That said, it can be a perfectly-adequate front light with the optional Cateye handlebar bracket (see below).
The party trick of the Volt 400 is the 2600mAH battery pack, which features a 10-lumen rear red light, allowing you to enhance your rearward visibility.
It's activated by a press of the central button, with a single press to swap between solid or a single fast flashing mode, and a long press to turn it off.
The constant rear light is good for 25 hours, the flashing rear for 250.
Operation of the main/front light is equally simple – two presses to turn on, then cycle through the five modes: 400-lumen High (3hrs), 100-lumen Medium (10hrs), 50-lumen Low (18hrs), 'HyperConstant' which is the Low-level always on with a twice-per-second full-power flash (9hrs) and finally a simple flash good for 150hrs.
Both front and rear have a memory mode, so will always turn on in the last-used setting.
I found the button moderately tactile and workable in all but the thickest of gloves.
Note that all these run-times are assuming the other end isn't operating... In the real world the worst-case scenario run-time for the front on high and rear on constant is about two and a half hours, the red low-battery button indicator coming on for the last 30 or so minutes. Once the front light dies, you have another 30 minutes of the front flashing setting to get you home or to another light source.
On the bike, in the dark, the Volt 400 is a surprisingly capable light. The yellowish beam is sharply focused, with a decent spread of lower light to aid peripheral vision. There are small cutouts at the front aiding side visibility, while the rear red is very visible for a 180-degree sweep, with a focused rearward beam through the on-off button.
The front beam on high has enough oomph to pick out potholes and drain grates if you're doing a moderate turn of speed – good for about 15mph in totally dark situations with my eyesight. If you're riding alongside others or amongst traffic it gets quickly overwhelmed.
During an off-road test of another light system, I descending a few hundred vertical metres of rocky Scottish mountain path using only the Volt 400, after my main light died. I might have gone a bit faster with a main light, but then probably wouldn't have just avoided the adult hind that leapt across my path on a corner. You wouldn't set out to use a Volt 400 as your only off-road light, but at a pinch it suffices.
My go-to comparison light is Lezyne's excellent 475-lumen Powerdrive XL from a few years back. Allowing for the extra 75 lumens, and considering that for around half the price in today's money you're getting a rear light as well, the Volt 400 stacks up well against a venerable industry benchmark.
When testing the 1700-lumen handlebar-mounted Magicshine system, I found the Volt 400 added a decent amount of information to the visible trail mix. Being able to pick out darker areas on the road, work out if they were indeed potholes or patches and therefore whether to avoid or roll over, made night riding more relaxing.
Where I think Cateye lets users down a bit is with the button that doubles as the battery level indicator. The only indication of battery level is when it's running low: the button lights red. This indication is only for the front light – there's no indication as to the charge state if you are only running the rear.
Charging the battery using the built-in micro-USB port from dead empty to full took 30 minutes longer than the indicated six hours, and that was using a wall charger with a theoretical 2400mA output, indicating a sub-USB 2.0 charge rate of 400mAH. Again, the button was red until fully charged, so you have no idea of progress. If you need to fill it up completely, plan ahead.
In use, the main/front light just turns off when the battery gets critical – there's no warning flash or stepped degradation from High to Medium to Low, as employed by the likes of Exposure. Once the front light dies the rear red remains on, and manually switching the rear to flashing mode, it ran on for another few hours which should do to get you home. You can turn the front light back on in flashing mode, but don't expect more than about 30 minutes of run.
It's a pity the solid rear light doesn't switch to flashing (one-tenth the battery drain) to preserve life, or indicate the critical level. And beware – once the rear turns off from solid mode, that's it – no turning back on in flashing.
Being part of Cateye's Volt modular range, the Volt 400 can use other Volt accessories. You can opt for extra batteries without the red light – either 2200mAH or 3600mAH. There are two external charging options: a simple £10 vertical USB-powered cradle, or a nifty £20 model that lets you charge the battery or use it as an external battery pack to charge a phone or other accessory. I can see this being of interest to bikepackers or other folk in need of backup power for e-things.
For £6 you can buy the standard Cateye handlebar bracket, which would of course render the rear red light pointless, but as part of a system you might juggle between a road bike, commuter or mountain bike, the modular nature of the batteries and brackets might work for you.
If you need a helmet light for visibility or off-road use, fancy a modular system you can expand with extra batteries or mounts or use to charge other things, perhaps while recharging from a dynamo or solar charger, give the Volt 400 a look. Minor foibles like battery level indication aside, it's a well-executed package.
A well-executed helmet-handlebar package covering a multitude of needs, but lacking battery information
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road.cc test report
Make and model: Cateye Volt 400 Duplex helmet light
Size tested: 400 lumens front, 10 lumens rear
Tell us what the light is for
It's for people wanting a helmet-friendly system that can turn its hand to being a handlebar or general-purpose torch/battery pack.
Cateye says: "Safety should be an important consideration for anyone riding a bicycle, and a premium lighting system like the Volt400 Duplex can play a critical role in the equation, especially when riding in traffic. This helmet mounted light integrates both headlight and taillight all in one lightweight package. Five front modes vary between a bright 400 lumen constant beam down to a flashing setting, while the rear can be switched between constant and flashing modes. On high, the front will run for 3 hours before the Li-ion battery will need recharging via a convenient USB port, but can go for an amazing 150 hours in flashing mode. In busy city traffic, running bright lights, especially in flashing mode at eye level to many motorists, can be one of the best visual defenses a bicyclist has. Use it."
Tell us some more about the technical aspects of the light?
127 x 42.5 x 31 mm
108.5 grams (light unit and battery)
High intensity white LED x1, red LED x1
(Front) * when the rear light is turned off.
400 lumens： 3hrs
100 lumens： 10hrs
50 lumens： 18hrs
Hyper Constant mode
400/50 lumens： 9hrs
(Rear) * when the front light is turned off.
10 lumens： 25hrs
10 lumens： 250hrs
Li-ion rechargeable battery (3.6V-2600mAh)
Approx 6hrs (USB2.0 recharge)
Recharge/discharge number of times：
About 300 times（until the rated capacity drops to 70%）
Low battery indicator, lighting mode memory function. Helmet mount included
Usual high Cateye standards.
Easy enough, but wish the battery level was indicated better, charging or discharging.
Bit fiddly with gloves on, but do-able.
Didn't leak or show any ill-effects.
2.5hrs run-time on full is decent for the size, a long charge time though.
For the size and cost, the spot focus does add useful information when in the dark.
Typical Cateye – should last a lifetime.
For what it does, surprisingly light.
Tell us how the light performed overall when used for its designed purpose
Overall I was pleased with the Volt 400. Does what it says on the tin.
Tell us what you particularly liked about the light
The flexibility to repurpose for other tasks.
Tell us what you particularly disliked about the light
No indication of charge level until it's low, with only 30 minutes left.
Did you enjoy using the light? Yes
Would you consider buying the light? Yes
Would you recommend the light to a friend? Yes
Use this box to explain your overall score
I'd like to like this light more, but the lack of battery level management and the sudden turn-off of the main beam leaves it wanting. It's a good light, but some simple software implementations would make it so much better.
About the tester
I usually ride: Merida Ride 5000 Disc My best bike is:
I've been riding for: Over 20 years I ride: A few times a week I would class myself as: Expert
I regularly do the following types of riding: cyclo-cross, club rides, general fitness riding, mountain biking, Dutch bike pootling