Following on from my earlier post on powering your gadgets for endurance racing, I decided to do a series of parallel tests with the dynamos and USB power units that I had accumulated. This included three dynamos (SON, Shutter Precision and Velogical) and six different USB power units (B&M Luxos U, Biologic Reecharge, Cycle2Charge, PedalPower Universal Cable, Supernova Plug III, and the ZZing). Interesting results …
Updated 19/4 to include Sinewave equipment
I set up the dynamo hubs in a wheel stand and used my multi-tool to spin the wheel. Kerrie from K-Lite had sent me a 3D printing file for a plastic gear that I could fit to the rim in lieu of the brake disc and run from a T5 belt. Unfortunately my multi-tool did not have enough torque to power this so I reverted to running it against the tyre. I mounted a cheap tyre for that wheel which I didn’t mind trashing. I mounted a wired Cats-eye odometer to the stand for the speed measurement. I did most of my tests with the Shutter Precision (SP) since its performance was similar to the SON (see Footnote 2). Here are a few photos of the setup.
Powering the Test Rig
Supernova Plug – No Output Below 13 km/h
I tried five different combinations of equipment:
- A Garmin 1000 which represents the basic navigation one needs to power;
- A Sony Xperia Z3 Compact phone which represents an alternative to the Garmin 1000;
- Garmin 1000 and Z3;
- Exposure Diablo light and Garmin 1000; and,
- Exposure Diablo light, Garmin 1000 and Z3.
With the B&M Luxos U I tested it with the Garmin 1000, Z3, and both—using its internal light.
For the Sinewave tests I replaced the Exposure Diablo light with a Busch & Muller Lumotec IQ-X light since my friend took the Diablo home to the UK.
The table below summarizes the results.
|Gear||Garmin||Z3||Garmin & Z3||Light & Garmin||Light & Z3||Light & Garmin & Z3|
|Reecharge||Y||Y||~ Drops||Y||Y||~ Drops|
|Cycle2Charge||>13 km/h||>13 km/h||N||>13 km/h||N||N|
|Supernova Plug III||>13 km/h||>13 km/h||N||>13 km/h||>31 km/h||N|
|eWerk (5 v and 1.4 amp setting)||Y||Y||Y||Y||Y||Y|
|Cycle2Charge + Goal Zero||Y||Y||Y||Y||Y||Y|
|Sinewave Revolution||Y||Y||~ Drops||Y||~ Drops||~ Drops|
|Sinewave Reactor||Y||Y||~ Drops||Y||~ Drops||~ Drops|
|PedalPower Universal Cable||Y||Y||N||Y||~ Drops||~ Drops|
Note: When I say ‘drops’ it means that the unit was providing power but it was intermittent. Most systems follow the USB standard of 0.5 amp output but it also depends on the dynamo output. Here, the combination of the power demands of the gear (e.g. the light and the cell phone) meant that there was insufficient power being passed through (the light always gets the most power). A different light or GPS/phone would likely give a different result.
There was a clear differentiation in the results for systems with batteries and those without. The ‘winner’ hands down was the ZZing. It was able to run an Exposure Revo dynamo light, a Garmin 1000 and the Z3 at the same time. This is because it was able to put out a whopping 1.2 amps. The B&M eWerk worked equally well—but it doesn’t have a battery (they have one available, but the total cost is more than the ZZing). The ‘worst’ performers were the Supernova Plug III and the Cycle2Charge as they provided no power below 13 km/h and then could only power the Garmin 1000 and not the Z3.
So what is the take away message?
- For simplicity and versatility you can’t beat the Luxos U light with an integrated USB and a cache battery. I’ve had two of them but there are two weaknesses: (i) they are not robust (all plastic and I broke one in a very slow speed crash); (ii) they are a pain to mount. For this reason, I would never use one again for long-distance endurance racing, especially mountain biking.
- Battery Systems:
- The ZZing coupled with a more robust light (e.g. Luxos IQ-X Supernova) is the perfect pair. You will be able to power your GPS and phone and will have about 19 hours of battery life from the ZZing should your dynamo fail. Only downside is that you can’t recharge the ZZing from AC without a special adapter, but I’ve written to the developer about that.
- The Reecharge is a good runner up to the ZZing. It’s smaller and lighter, but had trouble running both the phone and the GPS at the same time. The battery is good for about 10 h between recharges, but you can recharge it easily from AC with a standard AC-USB power adapter.
- Non-Battery Systems:
- I would go for the Sinewave Revolution or the eWerk. The Sinewave comes across as more roust, but the eWerk outputs a higher amperage. Both would run well with a pass-through battery pack like the Goal Zero. The eWerk also allows you to have it output different voltages if you, say, want to recharge something like an Ay-Up 12 volt light (not that I’ve tested it!).
- I am not sold on the stem tube systems as they are fiddly and don’t offer a lot of advantages. The Supernova Plug is very expensive relative to what it does and they have a poor reliability record. The Sinewave Reactor is a much nicer design and does not have such a bad reputation. The Sinewave also works at very low speeds (5 km/h or more). The Cycle2Charge is a lower cost solution but not as nicely engineered as the Sinewave, and also does not work below 13 km/h
- Battery Packs:
- If I was running AA batteries for other devices I would go for the Goal Zero along with a Sinewave Revolution, an eWerk or a Cycle2Charge.
Footnote 1: Velogical
The Velogical gave unusual results. It was unable to power the GPS directly through the Cyle2Charge of Supernova Plug. I’ve put a video of the tests on YouTube here. The top is the speedometer which goes up to over 30 km/h. Below it is the multi-meter showing the AC voltage gets up to 6.5 volts. On the right is the Cycle2Charge with a USB gauge showing the output current (top) and voltage (bottom) going to my Garmin 1000. You’ll see that at all speeds these read 0 so while it was generating power, not sufficient to get through the Cycle2charge to power the Garmin.
With the same setup the Velogical did provide power to the ZZing and the Reecharge, as well as powering the Luxos U light (and its internal USB battery). So you are probably safe using it with one of these systems but not sure otherwise. Will do some more testing to get a better handle on the Velogical performance.
Footnote 2: Voltage vs Speed
The chart below shows the output voltage vs speed for the Son and SP hubs. This was measured with a 10 ohm resistor in line. The SP has a slightly higher voltage but the two perform equivalently. The Velogical voltage was measured using the Cycle2Charge as opposed to the 10 ohm resistor as the resistor gave anomalous readings (maximum voltage only 3.5 volts!). It has a much higher voltage output than either of the hub dynamos. Need to rerun these tests with the SP and the SON using the Cycle2Charge to make sure comparing apples with apples since the SP and SON should be closer to 6 volts than 5 …
Footnote 3: Flat Battery?
After first publishing this I was asked by someone what happened when a battery goes flat – will it power the light or the battery or ??? So I ran the ZZing completely flat and ran a test with the SP. At about 4 km/h the Zzing started to recharge. At about 8 km/h the Exposure light came on and the Garmin 1000 began to charge.