LightCharge Hub Dynamo-powered Bicycle USB Charger
- by Ken Self
- Published: 28 September 2012
As a cycling tourist and self-confessed gadget man, it is important to keep all of my gadgets charged whilst on tour; it isn’t always easy to find a source of electricity in the middle of nowhere. On my touring bike I have a dynamo hub that powers the lights and has a little spare juice for charging the gadgets. The problem is that my dynohub puts out 6V AC but most devices these days charge from USB which is 5V DC. Not only that, the output from the dynohub varies quite a bit depending on how fast you are going. This is not ideal for the camera, Garmin, power meter and other gadgets I normally travel with.
The Bike2Power LightCharge USB charger is designed to work with a dynohub putting out 6 to 12V AC and supplies a regulated 5V DC up to 250mA through a standard USB connector. The LightCharge consists of the unit itself with integrated cable and a bunch of cable ties for attaching it to the frame.
The unit is remarkably compact compared to similar devices I’ve seen and used; not much bigger in diameter than a 50 cent piece. It has two push buttons to toggle between using the unit to charge via the USB port or to direct all the power to standard dynamo lights – in effect switching the charging facility on or off. The buttons are weatherproofed by a soft plastic cover. LEDs indicate which switch position has been selected.
The USB port is the standard size and has a cover to keep out dirt and water when it is not in use. When a USB plug is inserted it is a snug fit, but one should position the unit carefully to minimise the chance of water getting in or the plug shaking loose. Placing the port horizontally would possibly be the best option.
The back of the unit has a plastic mounting block that is concave to fit on to most standard diameter tubes or handlebars. There are slots in the block for cable ties to secure it to the frame. As an example, I mounted the LightCharge on the underside of the handlebars, underneath the Garmin mount.
A three core cable comes out of the unit which is long enough to run all the way down the forks to the dynohub. Two of these wires connect to the dynohub. If you have a Shimano dynohub the bare wires attach straight into the Shimano connector. If you have a Schmidt dynohub (as I do) you need to terminate the wires with spade connectors (not supplied). The third wire is terminated with a crimp joiner. The idea is to crimp the open end onto the wire leading to your headlight.
My setup is a bit different to the usual. First of all I don’t like having two sets of wires running down the fork. So instead I have a kind of extension cord running from the dynohub to the top of the forks that terminates with spade connectors the same as on the dynohub. Also, I like to run my lights all the time and the dynohub can run my lights and charge my Garmin at the same time. So instead of connecting the third wire to my headlights, I wired the headlights in parallel with the LightCharge. If I want to disconnect the LightCharge so it does not draw power, I use its switch as an on/off switch. If I want to run the LightCharge with full power, I can simply switch off the headlights.
For my first ride I just threw the unit into my handlebar bag and grabbed a retracting USB cable with a mini-B end to connect the LightCharge to my Garmin Edge 705. I set out along the Main Yarra Trail and Diamond Creek Trail towards Diamond Creek. These trails are largely unsealed and a bit bumpy so a good test for the mechanical connections. The LightCharge worked as advertised; the LED indicated correctly the switch setting and kept the Garmin charged while I also had the lights running.
I once calculated that the Garmin draws about 0.3W or one tenth of the dynohub output which is why I can run the lights and keep the Garmin charged at the same time. Other devices may draw more power so this might not work for them. Also, keeping the Garmin topped up is one thing but recharging it is another thing altogether. I did a rough test where I allowed the Garmin to discharge about one third (the only gauge of this is a picture on the screen so it’s hard to be precise). With the LightCharge connected and headlights off I rode around and after about 2.5 hours gentle riding the Garmin was almost fully charged. This should give you the idea that fast recharging from a dynohub is not to be expected. One thing I did not test was recharging from completely flat. From experience, this is not usually very successful and the Garmin certainly wont operate until some minimum charge level is reached. In those situations you are better off recharging it with a PowerMonkey or equivalent.
A slight digression here for Garmin owners. The Garmin is quite picky about the type of USB cable you use. Basically, depending on how the pins are set up, it will decide if it is connected to a charger or connected to a computer. If it thinks it’s connected to a computer, even if only charging, it wont record your ride or show your data. Alas, my retracting cable was not set up properly and partway through the ride the Garmin switched into “computer” mode. Luckily I had also brought a proper Garmin cable just in case. I preferred the compactness of the retracting cable but I really wanted to record the ride and see the data. A quick cable change and all was well.
The LightCharge is compact and lightweight. The standard USB port makes it more versatile than units that use proprietary connectors, and it’s switchable so you can be sure your lights work when you need them or you can charge with full power if you want. Just be careful how you mount the unit to keep the USB port protected from the elements when it is in use.
The LightCharge Hub Dynamo USB charger is available for purchase online from Bike2Power for $67.95 (USD)