Gear Review: Dynamo Systems

In this article I’m going to try and share my experiences of using various different dynamo lighting / charging systems. Chances are that if you’re reading this, you understand the concept of dynamo technology; but for those who don’t know, a dynamo powered system for lighting / charging will typically consist of three components: a dynamo generator within the front hub, a light, and a power converter to charge other electronics.

More and more competitors in endurance races have started to use dynamo technology — it removes the hassle of having to find power outlets to charge lights and GPS units, reducing stress and allowing you to spend more time on the road. I’ve been using a couple of different dynamo systems during the last few years and am completely sold on them. But don’t just take my word for it: Transcontinental competitor Nicholas Longworth sums up the frustrations that relying on mains power can cause:

“Stupidly I didn’t have a dynamo with the bike and the Garmin’s battery, whilst easily lasting a few days ride … of course does need to recharge at some point – and I paid for it.”

“I spent about 1 1/2 hours trying to wake the bar owners for what I thought was a charging GPS – the bar power socket must have been switched off as the GPS cut out an hour or two later – damn it!” (

When I was trying to research dynamo charging lighting systems, I struggled to find a resource with information from someone who had actually used them — just people trying to sell them! So, read on for what I hope will be an informative account of the systems I’ve used: SON hubs (both the delux and the new 28), Supernova and Exposure lights, the B&M E-Werk and Supernova Plug II power converters.

Typical concerns: Don’t dynamo systems cause a lot of drag?

Before I get into discussing pros and cons of specific systems, I thought I’d get address one of questions I get asked a lot about these systems: “Don’t they slow you down?” The short answer is a resounding “no”. If you’re interested in a more technical response, read the rest of this section, if not, skip to the specific gear reviews below.

I’ve used SON hubs in the past for touring on the road and have used them for long MTB rides at night — cumulatively I’ve ridden well over 20,000 miles using SON dynamo hubs and have never noticed any drag — I’m sure it’s there I just haven’t found it affected my riding (same daily distance in the same time). As the graph below shows, the drag of a SON hub vs. a good quality front hub is negligible (0.1 – 0.8W) between 5 and 25 km/h — provided the hub is not powering anything. To take a real world example: most people will climb between 5 and 25 km/h, this means that there will be almost no difference in the time it takes two equally strong riders, one with dynamo the other without, to climb the same pass. A bit of extra water in your bottle would cause more lost energy!

Dynamo hub drag comparison chart

Dynamo hub drag comparison chart

True, the hub does suck a greater number of watts when it is charging a device, or powering a light, but it is still a small number. At 20km an hour the SONdelux will pull about 5.5W from your legs — this is a similar number to the benefits provided by wearing an aero helmet. Obviously, there is a reason time-trialists worry about the watt-saving advantages of aero gear. It does help, but the gains are marginal — in the world of pro bike racing such gains can be the difference between 1st and 3rd. But these events aren’t where dynamo systems come into their own — adventure racing (and touring) is a different beast all together. My impression is that a good mental state is key unsupported ultra racing — I think having a GPS that does not run out of power, easy access to music for the monotonous sections, and light on demand (all things a dynamo hub will provide) will help to keep stress free and happy. Benefits that definitely outweigh the watts lost!

As far as weight is concerned, the SON28 model (the heavier of the two models I’ve used) weighs 430g — by comparison a Hope Pro 2 Evo hub weighs 185g — a difference of 245g. This might seem like a lot (I thought so when I first started looking into this), but when you factor in the amount of charging gear and batteries you don’t have to pack it doesn’t seem so bad! For starters, a dynamo powered front light has no battery, so that’s a 100-200g saved instantly.

Hubs: Why I chose SON 

There are an increasing number of companies producing lightweight, efficient dynamo hubs — Supernova, Shimano, and Shutter Precision (who supply hubs to Exposure) all make good quality hubs with low drag. However, SON have been in the game the longest, have a reputation for durability and quality, and still have the lowest drag numbers out there.

SON28 and SONdelux

SON28 and SONdelux

I’ve used their SONdelux model on the road and SON28 model for mountain biking and have never looked back — they just work without fuss or maintenance, which for me is the hallmark of quality engineering.

The SONdelux offers slightly less drag in a marginally lighter package, whereas the SON28 builds a stronger wheel, due to the wider flange spacing (66mm vs. 54mm), and outputs at 3W rather than the SONdelux’s 2.4W. The higher output and additional robustness of the 28 make it a great fit for slower off-road speeds, whereas the delux is best used on road. I’ve never found with either hub that the drag is noticeable, or that I don’t generate enough energy to keep everything charged and the lights powered.

I haven’t used other hubs, and so can’t speak to their strengths and weaknesses, but I can say that I’ve had nothing but a great experience using SON hubs. My delux has more miles on it (over 20,000) and it has had one service in that time — for free at the factory in Germany. That in itself was precautionary, the hub was still working fine, I just wanted to be on the safe side.

Useful link for wiring a SON hub:

Lights: Supernova and Exposure

Paired to SON hubs I’ve used the Supernova E3 Pro 2 and the Exposure Revo light. Both have worked well, but between the two the Revo is the clear winner.

I’ve done far more night miles commuting, touring, and racing with the E3 and it does the job fine, but there have been times when its 205 lumens have felt inadequate — riding a fast descent on a rough Serbian road at night during the Transcontinental Race, I definitely wished I could turn up the brightness! The Revo on the other hand packs 800 lumens and much more of a punch — I’ve had cars flash me to dip my headlight using it, and off-road I’ve ridden technical sections at night with confidence that I can see the trail.

They’re minor, but there are two features the E3 has that I miss on the Revo. Firstly, the E3 has a switch to turn the light on and off, whereas the Revo has to be unplugged to turn it off. As I said it’s a minor point, but I prefer not having to have an exposed cable-end when riding long distances in inclement weather. The second bonus about the E3 is that it has more attachment options — great if you want to attach it to the front fork to save room on the bars.

Power Converters: B&M E-Werk vs. Supernova Plug II+

Where there are myriad options on the market as far as lights and hubs are concerned, there are far fewer power converters out there. I’ve used the B&M E-Werk and Supernova Plug II+ — neither system is perfect, each having a couple of limitations.

The E-Werk sits on the down tube of the bike frame and can be set to output at different voltages and amperages — giving it the flexibility to charge numerous different devices. I’ve used it with an in-line cache battery to power a Garmin 800, iPhone, and camera. This system works flawlessly when the cache battery is in good condition, but the battery seems to be somewhat temperamental — it’s good for several thousand miles, after which it begins to fail and stops holding charge. The E-Werk can still be used to charge devices directly, but it can be somewhat temperamental without the battery and will not charge a Garmin at less than 11 kilometers an hour or an iPhone below 16.

Tony Hawke repairing Plug II. Transcontinental Race

Tony Hawke repairing his Plug II during the Transcontinental Race

The Plug II is the clear winner in terms of design aesthetic — it replaces the headset top cap, with all electronics housed within the steerer tube. It outputs a steady 5V through a USB port. The design is great and is way neater than the numerous wires of the E-Werk. It will charge my Garmin from around 6-7kmph and an iPhone from slightly higher; however, the Plug II+ will cut out at high speeds (35kmph) — not a deal breaker off-road, but a lot of power can be generated effortlessly during long, high speed descents on road and it’s annoying not to be able to use it (a look at the Supernova website suggests this has been fixed in the Plug III). Further, there have been reports of the Plug II+ being unreliable — I’ve not experienced this myself and have around 1000 miles on my unit, but it is a worry. A couple of guys on the Transcontintental race had this happen to them.

The better system is the E-Werk, but only when the cache battery is working. Considering this, if I had to pick a winner I’d possibly go with the Plug, it’s not perfect but it it’s a neater package and seems to be better at outputting a usable voltage at low speeds. It’s definitely not perfect however, and I’m interested to see reviews of the new Plug III, especially if they release a cache battery.


As far as I’m concerned dynamo systems are the way to go for unsupported ultra racing: they provide an awesome degree of flexibility and remove the need for complex, stressful, power management strategies. The range of hubs and lights available on the market today is superb; while there are issues with power converters, and no perfect solution is available, the E-Werk and Plug II+ are both capable of getting the job done (with a bit of tweaking).

I hope this has been helpful to anyone looking to take the plunge and invest in a dynamo lighting / charging system. Any questions let me know.

12 thoughts on “Gear Review: Dynamo Systems

  1. Supernova told me that the problems I and others had with the Plug II+ were due to an issue in the low/high speed cutout failing. This issue is supposed to be fix in the Plug III, one of which is on its way to me at the moment.

  2. Pingback: Keeping your batteries charged | Trails and Tours - Bikepacking

  3. This summer I met a used a son 28 with a plug 2 on a salsa fargo 3 for a lap of the west (palm springs/whistler BC/San Diego/palm spring) used the sierra cascade route north and the west coast south. Befor I got out of southern cal. The resistor in the head tube fried. I had to make a trip back to Topanga Creek cycles for a replacement. BTW this is an awesome shop! If your in the area go there if not for a bike,service or parts, then for like minded great people, coffee, or banana bread. Beautiful location for the shop too. Before I got to Tahoe I had problems again. Same thing, it shorted out in the steertube. They replaced it again. Before I got to Klamath Falls, the usb connection broke one of the metal connectors and wouldn’t charge. Ryan got me another replacement. This one would not charge on fast down hills and cycled off and on and destroyed the battery in my phone. I was done. Ryan at Topanga Creek cycles put up with my super frustration and got me a e-werks that has work for the rest of the trip. I didn’t get until Seattle where the guys at Rodriquez bikes put on. From there on I was able to charge my samsung tab 2 and charge a nightrider 800 light. I need to pair down what I carry. This trip was bike/kit 100 lbs with 3 litre bladder of water.

    I now have a philips saferide 60 in stead of a battery light. I use a 200 lumens head lamp with it when on the trail.

    On the tour I met 2 other people who had the plug on their bikes that were not working as well. One at Whistler, one south of Bellingham, Wa.

    I like the concept but the execution sucked. There is no excuse for this.

    • Hi,

      Thanks for your comments! It’s good to know that there are some reliability problems with the Plug II, although I haven’t experienced them myself I know that other’s have. Glad you managed to salvage the trip — sounds like an awesome ride!


  4. I forgot to tell about the nomad 7 guide 10 set up that saved my butt. Strapped it on top of my seat bag. That and coffee shops along the way.

  5. Hi Ed! Thanks for the super-useful article.
    I’m looking for a way to charge a tablet and i saw you talking about the possibility to use Plug II with a cache battery (on a post on adventurecycling). Have you ever tried that? Which kind of battery is possible to use? Also check our site if you like!

    • Hi Daniele,

      Thanks! I think the Plug II should work in conjunction with any batter that charges via USB (e.g. a Power Monkey). If you were charging a tablet you’d have to use quite a large battery, which would take a good few hours riding to fill. Other than that I don’t see any reason it wouldn’t work. I’m assuming that you’d use a tablet to blog while on tour, so you’d only have to charge it once every few days.

      Let me know how it works out if you give it a go!


      • The key with a cache battery is to find one that can accept charge from the dynamo as well as discharging to a device (eg Garmin) at the same time. This is particularly beneficial in smoothing the charge of a GPS unit at low speeds (rather than the charge cutting in and out as you go below minimum speed). A power monkey will not do this – there are a few options designed specifically for use with a dynamo (reecharge battery, and Cinq5 shortly to release one specifically for the Plug III). However, they are typically much lower capacity than eg a power monkey (maybe 2000mHa v 10,000), so i tend to take and use both (not recommended for UL racers…).

        Nice website btw!

  6. How do you divert energy from the headlight to the USB port during the daytime, so that you can charge your GPS? Your headlight doesn’t have an off switch so I imagine it must be sucking power all the time.

    • Hi TJ,

      Sorry — I only just saw your comment! The Supernova E3 does have an off switch (on the back) and the Exposure Revo can be unplugged. With either light it’s dead easy to make sure they’re not sucking power during the day!


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s