After years of writing in-depth about dynamo hubs, I was genuinely surprised by new data from FahrradZukunft revealing major differences in output power across SON models, especially when it comes to the new SON 29 S hub dynamo.
This new test paired four dynamo hubs with various lights and USB chargers, measuring performance across speeds from 0 to 30 km/h. The results were surprising, revealing just how much performance can vary, even among hubs all rated at 6 volts and 3 watts.
The SON 28 Classic dynamo hub, which has long been used for the majority of all dynamo light and USB charger benchmark tests over the years, now lags behind the performance of newer SON hub models. And that performance gap has real-world implications, especially when it comes to charging your devices or lighting your way.
Let’s dive into the details.
Hub Dynamo Lab Test
Andreas Oehler tested four different SON hub dynamo models for FahrradZukunft:
- SON 28 Classic: Standard 6V 3W dynamo hub
- SONdelux 12: Dynamo hub for high-speed use
- SON 28 12: Most powerful current SON hub
- SON 29 S: New 40 magnetic pole dynamo hub
These four hubs were connected to three different dynamo lights and USB chargers:
- SON Ladelux: All-new light and USB charger from SON
- B&M E-Werk USB Charger: Powerful new charger from Busch & Müller
- Supernova M99 DY Pro: Super bright dynamo light from Supernova
Method
The various SON dynamo hubs were mounted in the FahrradZukunft test rig and spun at different speeds.
The setup assumed a 28″ wheel with a 700 mm diameter. Electrical output from the hub, along with the charge and discharge power of the charging adapter’s buffer battery, was measured using a GMC Metrahit 29S. A programmable electronic load (Array 3711A) simulated the USB power draw.
Once everything was in place, drive power was calculated based on the measurements.
You can see the full test over at FahrradZukunft.
Results: SON Dynamo Hub Output Power
The graph above compares the four SON hubs when paired with various lights and USB chargers. Speed (in km/h) is shown along the horizontal axis, while power output (in watts) is displayed on the vertical axis.
For context, the minimum power required to charge a smartphone is around 2.5 watts. And most smartphones need between 3 and 4 watts to keep the screen fully lit during navigation.
While the graph offers valuable insights, I’ve broken down the power differences in percentage terms in the tables below, using the SON 28 Classic as the baseline. This makes it easier to see just how much more (or less) powerful each hub is in comparison.
SON Ladelux Light & USB Charger
| SON Classic | SON 28 12 | SON 29 S | SON Delux | |
| 10 km/h | Baseline | + 39% | + 57% | – 9.5% |
| 15 km/h | Baseline | + 29% | + 45% | – 4.8% |
| 20 km/h | Baseline | + 27% | + 40% | – 9.7% |
| 25 km/h | Baseline | + 27% | No Data | – 6.2% |
| 30 km/h | Baseline | No Data | No Data | – 5.9% |
| Average | Baseline | + 31% | + 47% | – 7.2% |
Whether you’re charging devices or powering lights, the SON 29 S consistently outperforms the SON Classic across all speeds, delivering 40 to 57% more power, with the most significant gains at lower speeds. This translates into a noticeable improvement in real-world use: you’ll reach the 2.5 W minimum charging specification for a smartphone by just 5 km/h, and over 6 watts by 15 km/h!
The SON 28 12 is slightly less powerful than the SON 29 S but still offers a substantial upgrade, with a 27 to 39% power increase over the Classic. As a result, it reaches the minimum charging threshold for a smartphone (2.5 watts) about 4 km/h sooner than the Classic.
As expected, the SONdelux produces less power across all speeds, but it remains close behind the SON Classic throughout the range.
B&M K-Werk USB Charger
| SON Classic | SON 28 12 | SON 29 S | SON Delux | |
| 10 km/h | Baseline | + 38% | + 125% | – 12% |
| 15 km/h | Baseline | + 28% | + 63% | – 12% |
| 20 km/h | Baseline | + 6% | – 1.0% | – 3.0% |
| 25 km/h | Baseline | + 3.2% | + 3.0% | + 3.0% |
| 30 km/h | Baseline | – 3.4% | + 5.1% | + 10% |
| Average | Baseline | + 14% | + 39% | – 2.8% |
When charging with the K-Werk at 10 km/h, the new SON 29 S delivered its strongest performance, producing 125% more power than the SON Classic. That’s right, 11 km/h is all the speed you need to achieve 4 watts of power, which provides a decent charge for most smartphones. While the hub’s power output remains impressive at 15 km/h, it has fully plateaued by 20 km/h.
The SON 28 12 also shows a solid improvement at lower speeds, offering 28 to 38% more power than the Classic. However, like the SON 29 S, its output levels off around 20 km/h.
Interestingly, while the SONdelux produces about 12% less power than the SON Classic at lower speeds, it overtakes all other hubs by the time you reach 30 km/h – delivering the highest USB charging output in the test.
Supernova M99 DY Pro Light
| SON Classic | SON 28 12 | SON 29 S | SON Delux | |
| 10 km/h | Baseline | + 44% | + 75% | – 12% |
| 15 km/h | Baseline | + 32% | + 61% | – 13% |
| 20 km/h | Baseline | + 31% | + 49% | – 8.0% |
| 25 km/h | Baseline | + 15% | + 30% | – 9.0% |
| 30 km/h | Baseline | + 10% | + 24% | – 5.0% |
| Average | Baseline | + 26% | + 48% | – 9.0% |
Shifting focus from USB charging to lighting, let’s look at the Supernova M99 DY Pro dynamo headlight.
At 10 km/h, the SON 29 S delivers 75% more power than the SON 28 Classic, and this results in a significantly brighter beam and reduced flickering. Even at 20 km/h, the 29 S still provides nearly 50% more power than the Classic.
The SON 28 12 offers more modest gains, delivering between 10% and 44% more power than the SON Classic, or roughly half the improvement seen with the SON 29 S.
As expected, the SONdelux lags behind in output. It produces less power than the SON Classic across the board, resulting in a dimmer beam (especially at lower speeds). At 10 km/h, it delivers only about half the power of the SON 29 S, making the difference in brightness quite noticeable.
SON Dynamo Hub Comparison
Recent dynamo hub testing indicated that the new Shimano hub could produce more power (especially between 5 and 15 km/h), but I hadn’t realised how much variation there is among SON hubs too.
Running an average across all tests and speeds:
- The new SON 29 S delivered 45% more power than the SON 28 Classic
- The SON 28 12 was 24% more powerful than the SON 28 Classic
- The SONdelux was 6.3% less powerful than the SON 28 Classic
More power means brighter lights or stronger device charging at a given speed. But keep in mind, it also results in increased drag, which can slow you down.
Or to put it another way: the power the SON Classic generates at 15 km/h can be matched by the SON 28 12 at just 12 km/h, and by the SON 29 S at only 10 km/h. In contrast, the SONdelux would require you to travel at 16 km/h to achieve the same output.
Which SON Hub Dynamo Is The Best?
The best SON dynamo hub for you depends on how and where you ride.
For off-road adventures and bicycle touring, where strong lighting and USB charging at low speeds are essential, the SON 29 S or SON 28 12 are your top choices.
The new, high-output SON 29 S is especially impressive, generating 4 watts at just 11 km/h when paired with either the SON Ladelux or K-Werk USB chargers. At the same speed, it can also power the M99 DY Pro’s high beam mode without flickering.
For road and gravel riding, where average speeds tend to be higher, the SON 28 Classic or SONdelux will be more than adequate.
With either the Ladelux or K-Werk USB chargers, both hubs hit the minimum charging specification for a smartphone at approximately 11 to 13 km/h. And by 15 to 16 km/h, they’re producing around 4 watts, which is enough power to keep a smartphone screen continuously powered for navigation.
How Do SON Dynamo Hubs Compare To Other Hubs?
Previous testing has revealed significant differences in dynamo hub power output.
When paired with a kLite USB charger, Shimano hubs produced 30 to 60% more power than the SON Classic at speeds between 15 and 20 km/h. In contrast, the SP dynamo hub delivered 6 to 47% less power than the SON Classic under the same test conditions.
While the current testing uses a different protocol and equipment (making direct comparisons difficult), we can reasonably expect the SON 28 12 to match or outperform the Shimano 3D32, and the SON 29 S to exceed the output of the Shimano UR700.
Summary
This test highlights the significant differences in power output between various SON dynamo hubs.
On average, the new SON 29 S delivers 45% more power than the SON 28 Classic, while the thru-axle versions of the SON 28 offer a 24% boost.
For cyclists who typically ride below 15 km/h, especially on long-distance tours or bikepacking trips, a higher-output dynamo hub is well worth considering if consistent USB charging or bright lighting is a priority.
