Supernova Airstream: High Powered German Rechargeable Bike Light
- by Ken Self
- Published: 21 August 2013
If you are a commuter, a cycle tourer, or an endurance rider who does a lot of night riding, the Supernova Airstream could be for you. It is a high powered USB rechargeable light in a torch format that mounts on your handlebars and offers four levels of brightness plus a flashing mode.
Sounds simple, but beginning with the presentation in a tin box with Supernova stamped on the lid, this is something more. Inside the tin box you have: the light itself with a mounting plate, two shims of different thickness, a mains recharger, two O-rings, two dust caps for the recharging socket, and instructions.
My first impressions were that this was a very attractive light, and solidly built. I liked the rubber O-ring attachment system, though this obviously needed to be tested in practice. What I didn’t like, however, was the small rubber cap that covers the recharging port, as I’ll explain later.
Before I received the light, Christopher (BNA Overlord) had challenged me to work out how to operate the light without reading the manual and I eagerly took the challenge. To start with, I gave the button one press and nothing happened. I then tried a long press but still nothing. There are no other buttons so this had to the right approach. After a few random presses at different intervals it eventually it switched on and subsequently changed into flash mode and then was adjusting the brightness. This confirmed that the battery was charged and I was not the target of a practical joke and facing an unproductive evening. A long press turned off the light which is conventional.
After further experimentation I discovered that a double-click switched the light on. Once the light was switched on, another double click started flash mode and a single click returned it back to the steady beam. Single presses cycle the light through the 4 brightness levels but the clicks have to be “long enough”: a quick click is too short while a long press of course switches off. This brings me to the first of my “dislikes”. The double-click to switch on is not intuitive, but I guess an advantage of that is that you are unlikely to switch on the light accidentally by stuffing it in a bag when not in use. Also, getting the right amount of “press” to change brightness levels reliably takes a little practice.
The top two brightness levels are hard to tell apart, and there is no other feedback that you have successfully changed, so I spent a few times cycling through the brightness levels till I was sure I had the mode I wanted. I won’t lose any sleep over this, and of course I could read the instructions, though it is nice when you get a product that works intuitively.
Now that the experimental phase was over, I was allowed to read the manual. I found that the light comes out of the box with 30% charge and needs 6 hours to charge fully. To charge the light, remove the cap covering the recharge socket (that’s right, the rubber cap I don’t like) and plug in the mains charger. A USB charge cable is an optional accessory. With the mains charger connected a pulsing green LED indicates that the light is charging and a solid green LED indicates full charge. The manual has dire warnings about shorting out the recharge socket, so once charged it is a good idea to replace the cap right away.
Here comes the dislike again, perhaps it’s because of my age or eyesight but do you think I could find that cap? It took me 15 to 20 minutes of looking to find it and on each subsequent recharge I also had to spend time looking for it. Luckily there is a spare cap in the pack, but if the cap was attached to the light it would be much harder to lose it.
I was interested to see how long the light would last in different modes. The manual states 2.5 hours at maximum brightness, 3.5 hours at level 2, 7 hours for the third brightness level and more than 24 hours for the fourth level. For most uses I would expect level 3 or level 4 to be the most practical. At the higher levels, commuters would probably want to recharge during the day to ensure a safe trip home and tourers who like having lights on during daylight would need more than 3 hours.
At level 3 it took 3.75 hours from switch on till the indicator LED changed from green to red+green indicating 50% charge or less. After 7.25 hours the LED turned to red only indicating less than 10% charge. At 7.5 hours the red LED started flashing and within a couple of minutes the light died. So the light performs in this mode as claimed. Recharging to a full charge from flat took six hour, also as claimed.
The manual gives no information on the burn time for flashing but the Supernova Airstream website says 12 hours which was confirmed by testing. Flashing mode has a rate of about 2 flashes per second.
Level 4 brightness is only available for the “international” (non-German) model and the manual states “> 24 hours” burn time while the website says 25 hours. On the bench it lasted 24.25 hours. The following graph shows the bench tested burn times for each level along with a rough indication of the brightness.
Level 4 is quite dim compared to the other levels, but does it meet the Australian requirement for visibility from 200 metres? As a crude test, I set up the light at level 4 at night and walked 200 metres down the road. The light was clearly visible so I would expect it would be legal to use in that mode.
A feature of the Airstream is its heat management, which gives higher light output and longer life. At maximum brightness, an ambient temperature of 19 degrees, and with no airflow, the temperature at the heatsink stabilised at around 40 degrees after 50 minutes until about 145 minutes when the light dimmed to conserve power before switching off some 15 minutes later. With a domestic fan blowing air over the light to simulate the airflow when riding, the temperature stabilised at around 24 degrees after 15 minutes until it dimmed at around 140 minutes.
Now I’m no expert on these things but the results seem pretty good. I believe the critical temperature for these devices is around 85 degrees, beyond which the brightness and lifetime are degraded. Obviously, the temperature of the LED will be higher than at the heatsink, but a 5 degree temperature rise above ambient should be of no concern. Even with no airflow, the temperature rise was less than 23 degrees which would suggest that you would have to be stationary on a hot day with the light on full to even begin to have any worries and, seriously, who would be doing that?
A great feature of the Airstream is that it can be recharged whilst it is in use. By connecting it to the mains charger I could simulate running the light from an external source, like a dynamo or Powermonkey, and see how long it lasts at different brightness levels. Something more realistic, like a dynamo-USB adapter connected with the USB cable, would have been preferable, but the USB charger is an add-on and I’m a little puzzled why it isn’t included as standard. The charger is rated at 550mA output, which is above the USB standard of 500mA, so it charges the Airstream faster than a normal USB supply. Also, in real life, the dynamo only works to recharge when you are in motion so you can expect shorter running times.
Note: A trap to watch for when using the Airstream in this way. I found I had to first switch on the light then plug in the charger. Doing it the other way around led to the light not recharging.
At level 1 it lasted for nearly 6 hours before it switched off. My own calculations indicated 5 hours would be the limit and the difference is accounted for by the extra current from the charger. At level 2, my calculations predicted 11.7 hours but it ran for at 15 hours. Note that at the end of this time the light is fully discharged and needs 6 hours to recharge fully.
At levels 3 and 4 running from a dynamo the light should be able to be used “indefinitely” with minimal discharging. Of course that assumes you are moving fast enough to power the light from the dynamo.
The Airstream mounts onto handlebars using one of the two supplied O-rings. For my handlebars I did not need the shims but noted that they have a convenient lug that fits into a matching hole in the mounting bracket so they don’t fall out. This system makes for easy fitting and removal and adapts to fit different handlebar diameters. The bracket can also be rotated to allow mounting on the stem.
For comparison, I normally run a dynohub driven Busch & Müller (B&M) Lumotec IQ Cyo which is regarded as a bright light at 60 lux. The Supernova website says the Airstream produces 370 lumens. I personally don’t like lumens for rating and prefer lux as it is more accurate for measuring and comparing brightness as it takes into account factors such how focussed the light beam is versus how much of the road it lights up.
So how to compare lux versus lumens? My day job often requires me to come up with “reasonable” assumptions to estimate outcomes so, working off the back of an envelope, I estimated that the Airstream would produce 100 lux at level 1, 70 lux at level 2, 40 lux at level 3 and 10 lux at level 4, assuming equivalent beam shapes, among other things.
It was a beautiful night for the test ride. A bit chilly at 7 degrees, so no chance of the Airstream overheating, but almost no wind and no chance of rain. I rugged up and sallied forth to my local shared path that runs through parklands with no lighting except from the distant street lights. Alternating between my B&M and the Airstream, I felt that the Airstream gave a similar light output at level 3 and with that I could ride comfortably at speeds up to 25 km/h before reaching for the brakes. The Airstream has a narrower beam that throws an evenly lit oval with a sharp cutoff at the edges which accounts for the brighter than expected lighting at that level. That is, it concentrates less light into a smaller area so it appears brighter. Riding with both lights together was a joy with a very bright spot in front where the two lights converge, and the sides lit up with the wide beam. But of course, not everyone will be in a position to do that.
Levels 1 and 2 were a boon for the winding and dipping path, but leads me to my next dislike. At some points it was useful to use one of the brighter modes than level 3, but to get there requires a couple of long button presses. So getting more light in a hurry is not easy and changing modes in general is quite distracting when you need to keep your eyes on the track. A trick I discovered was to double click to go into flashing mode then a single click to go to level 1 brightness. This was quicker and more reliable than trying to click through the various levels.
On the suburban streets, level 4 or flashing mode were both more than adequate. I particularly liked the flashing mode as it is considerably brighter than other “cheapo” flashing lights I’ve used and I was confident that nobody could possibly miss seeing it.
Who is it for?
If you have a 1 hour commute each way you could run the Airstream at level 4 and still have plenty of charge left at the end of the week. Or you could run it in flashing mode and be close to empty by the weekend. Alternatively, you could run it at level 3 with the odd increase when needed and recharge overnight.
Personally, I would not use the higher levels continuously as it would mean having a charger sitting both at home and in the office. Plus, with my notoriously bad memory, it’s a dead cert I’d regularly leave the light behind at the office.
In the time I’ve been using the Airstream I’ve converted into quite a fan of riding shared paths in darkness whereas previously I was quite wary of them outside daylight hours. Having a bright light when it’s needed makes it that much easier to maintain a reasonable speed.
For touring I enjoy the convenience of a dynamo powered light and the Airstream is beneficial for those wanting to get the most from their lighting investment. With the USB cable and a dynamo USB adapter, the Airstream can be used in place of a hard wired dynamo light running on level 3 or 4, where the USB charger can keep up. It has the advantages of more light when needed, courtesy of its battery power, plus a flashing mode. Additionally, you can easily swap it over to whichever of your other bikes you need to whether they have a dynamo or not. Note however, that the USB cable is an optional extra that you should order when you purchase the light.
Audax riders would really benefit from this light on dark country roads as it provides the bright lighting when you need it but also the flexibility to adjust the setting and have a ‘legal’ light that provides illumination the whole distance. This is especially important for extreme events such as the 24 hour Oppy in March when you need to ‘light up’ for 12 hours or more.
The best feature, in my opinion, is that this is one of the few, if not the only light, that I know of that can operate whilst being recharged from a USB port. So for a long overnight ride it is possible to hook up an auxiliary power source, like a Powermonkey or similar, to almost double the burn time (e.g. around 12.5 hours at level 3), while a Powermonkey extreme would quadruple the burn time (e.g. around 29 hours at level 3). This eliminates the need to stop to swap lights or batteries.
I’d give the Airstream 4 stars out of 5 and I’m a notoriously hard marker. It could be improved by supplying a USB cable as standard, having more intuitive and usable controls, and a dust cap that is attached to the body of the light.
But these are minor niggles in what is otherwise a great combination of: a bright light with decent battery life, lots of versatility by being able to move it from one bike to another, and being able to power it from multiple sources.
Supernova dropped their previous Australian importer and if you buy direct from the Supernova online store in Germany this light will set you back €199 Euro (plus postage) so over $300. At the time of writing, the Supernova Airstream has been spotted in the Pro-Lite Oz online shop for $199.
This version of the light is known as the Airstream International and further information is available from the Supernova Website: supernova-lights.com
Article Title: Supernova Airstream: High Powered German Rechargeable Bike Light
Article Link: http://www.bicycles.net.au/2013/08/supernova-airstream-powerful-bicycle-night-light/