Fully Loaded: Keeping Electrons Flowing | BIKE Magazine


Electrons. For most of us, our lives are utterly reliant on these little buggers for everything from powering our houses to making our cars run to keeping precious cell phones functioning. For so many of us, bikes provide some level of reprieve from other parts of our lives that provide less enjoyment or fewer endorphins. But one thing that's getting ever harder from which to pedal away is our reliance (or desire for) that steady stream of electrons—electronic shifting, power meters, GPS units, ever-fancier dropper posts, lights for when darkness falls, and even e-bikes. For lovers of long rides, bikepacking adventures, or ultra races that span days or weeks, packing or generating electrons to keep all the electronic gadgets working can be a challenge.

For adventures stretching beyond the long day ride or well into the dark hours and requiring long-lasting lights, any need for power devices needs to be supplied by either extra batteries, a dynamo hub that generates its own power, or the sun (we'll leave the discussion of solar panels and photosynthesis for another time). Some bikepackers prefer to rely on devices that run on AA or similar batteries that can be readily purchased along the way. But for phones, cameras, and most lights, that's not a viable option. USB batteries can potentially provide a few charges for most devices. And dynamo hubs can offer an endless source of power for charging batteries or powering lights so long as you keep rolling at an adequate speed.

So you want to retreat into the backcountry, but how to power all the things?

Dynamo hubs

Using the rotation of the front wheel to generate energy in the front hub, the concept of dynamo hubs seems a bit too good to be true. So long as you're moving, you've got power. In reality, these hubs offer a great option for riders spending longer days on dirt roads or pavement where riding speeds are high enough to generate notable power. At slower singletrack speeds, these hubs can struggle to produce enough energy to power particularly bright lights or charge devices quickly, but they still do generate some power. Generally, don't expect to be able to charge and power numerous devices with a dynamo setup unless you're moving quickly. And dynamo hubs themselves add a bit of resistance to your ride but not enough that you're likely to notice it in any way. The Schmidt SON28 hub ($300+ and a hefty 340 grams) has become the gold standard for dynamos—it's incredibly reliable and withstands the rigors of rough and wet riding.

The Schmidt SON 28 dynamo hub after a couple weeks of generating electrons to keep camera, phone and GPS unit powered on a cross-Arizona ride.

Lighting options

There is absolutely no shortage of lighting options available to bikepackers; everything from small AAA-powered headlamps or flashlights to blindingly bright singletrack-specific 24-hour racing setups. But having adequate light for night riding while not having to carry a backpack full of extra batteries is a balance, especially for ultra racers needing light for successive long nights of riding. For riders planning minimal night riding, simple headlamps or flashlights can work just fine. A light like the Blackburn Dayblazer 800 ($60, 129 grams) offers ample lighting for a few hours or more (300 lumens for ~five hours) and can be recharged via USB if needed. The Fenix BC21R Bike Light ($75; 68 grams) is a similar option that runs on USB-rechargeable and easily replaceable 18650 batteries ($10+, 50 grams), which resemble AA cells on steroids. The benefit of this system is that extra 18650 cells can be easily carried along, and a single battery provides a moderate amount of light for eight hours (200 lumens for 8+ hours). I've used this light for numerous ultras, carrying anywhere from two to 10 extra batteries for as much as a week of nearly-continuous racing. And lights like these are simple and clean for helmet or handlebars—entirely self-contained without any cords.

Left to right: Blackburn Dayblazer 800, Fenix BC21R, Sinewave Cycles Beacon, k-lite Bikepacker PRO v2, and the tiny AA-powered Fenix E12 flashlight.

For riders requiring more hours of lighting or brighter lights, dynamo-specific lights like the k-Lite Bikepacker PRO v2 or the Sinewave Cycles Beacon may be better options. The Bikepacker PRO v2 ($260, ~140 grams for full setup), made in Australia, includes a very small light unit and a separate waterproof box containing the system's electronic innards and a low/high beam switch. k-Lite also offers a separate USB charging module ($145) to add to the system so you can run the light in the dark and charge another device during the day. The light itself provides up to 1,300 lumens, but in my experience, anything remotely resembling that amount of light only happens at 20+ mph. At 10 mph, the light seems to run at about half its maximum power. But at low speeds on technical singletrack, the light seems to provide what looks more like just 100 lumens. A standlight feature provides a few minutes of light after stopping, but for an extended hike-a-bike, the light dims completely after less than 10 minutes. This setup is ideal for the relatively fast speeds of pavement and dirt roads, but on singletrack, it's best when combined with a helmet-mounted unit for additional light.

The Sinewave Cycles Beacon ($350+, ~130 grams for full setup; 1,300 lumens maximum) is made in the USA, like all the company’s products. The setup is slick and tidy with all the electronics housed within the light head itself, and a USB charging port is also included in the back of light. Beyond that, the light can be connected to a USB cache battery, and at low speeds, that external battery helps power the light to keep brightness notably higher (at what seems more like 300+ lumens). At higher speeds, however, the dynamo hub powers the light while simultaneously charging the cache battery. In my experience with this system on slower terrain, my 24,000 mAh cache battery gradually drained over the course of a night, becoming mostly depleted by morning and requiring much of the following day of riding to recharge. On dirt roads and other faster surfaces, the reliance on the cache battery is much lower.

GPS units for navigating

Bikepackers commonly rely at least in part on GPS units or phones for navigation, so keeping these powered can be critically important. The AA-powered Garmin eTrex series of GPS units have proven to be the most reliable relatively small options on the market. On a pair of lithium batteries, an eTrex runs for close to 30 hours, and I've been using them for more than a decade with zero complaints. For riders using bike-specific GPS units or wanting to collect power data on long rides (yes, some ultra racers desire this capability), units in the Garmin Edge series offer another option, but with run times of perhaps 12 hours on a full charge (and notably less if the map screen is always on display, depending on model), these require frequent charging from a USB cache battery. And the Edge series can be particularly fussy with variable charging current, so they don't charge well directly off a dynamo hub, necessitating a cache battery.

One additional family of options are GPS sports watches like the Suunto 9 ($500, 85 grams). This watch can run for 120+ hours on a single charge (the longest of any sports watch available), collect location and power data, and the watch offers some rudimentary navigation capabilities. Based on my experience, expecting more like 40-50 hours of runtime for most users is more reasonable. I wouldn't recommend this as a primary navigational device if you're trying to follow a GPX track, but it can serve as a back-up option.

Keeping other devices charged

Keeping the little screens powered (clockwise from left): Garmin eTrex 20 GPS, Suunto 9 GPS watch, Anker USB cache battery, Garmin Edge 810 GPS, Sinewave Cycles Reactor top-cap USB charger and Sinewave Cycles Revolution USB charger.

Finally, for other electron needs for cell phones, cameras, and any additional electronics you may want to carry, one other svelte USB charging option is the Sinewave Cycles Reactor. It's a top cap that mounts in your fork's steerer tube. Installation takes a bit of time—first, tap the star nut a bit deeper into the steerer, thread two small wires through gaps in the star nut, attach a pair of connectors, and plug the wiring into the top cap and a dynamo. Once that's done, slide a USB connector into the Reactor, start pedaling, and charge away. If your adventure plans don't include any notable night riding or light needs, this simple setup allows charging off a dynamo without really adding any other clutter to the front of the bike. Using just this setup on a rugged two-week dirt and 4×4 road tour across Arizona, I managed to keep two smart phones, two GPS units and a Sony A6000 camera powered for the entire trip. Had there been more slow trail riding, though, this would have been too much to keep charged even with full days of pedaling.