Kemo M172N Bicycle Power Charge Controller USB Connection for Mobile Phones, Navigators, PDAs, MP3 Players on Bicycle Dynamo Input voltage up to max. 70V with LED Indicator

Absolutely brilliant

This converter is far cheaper than others on the market and seems to perform well. Coupled with a SonDelux dynamo, on a 700C wheel, it starts to produce charge from a surprisingly low speed. My only gripe is where the wires from dynamo and lights pass through three holes in the case and terminate in a screw-terminal block, just a few mm inside (see photo). There is no provision for strain-relief, or any obvious way to add it. If the wires get snagged, as is very likely on a bike, they will either pull out of the terminals (annoying) or rip the terminal block off the PCB. This would be literally terminal, as the PCB is back-potted with resin and therefore unrepairable. I doubled the wires back along the stem and securely attached them with cable ties, close to where they enter the converter, to add some external support. The USB port is also unsealed, so you need to be careful about where and how the unit is mounted to avoid water ingress.A generally good product, slightly let down by lack of basic good design practice in the execution.

Not the simplest one to use, but it seems to work okay fingers crossed

Didn't work

This did worked for me. I bought the (much) larger, more powerful USB version because I thought it would be more adaptable, and I had read poor reviews of the smaller mini-USB version failing to charge phones and satnavs. In the event, I found it quite adequately charged my Garmin Edge 800 satnav (with big touch LCD screen and Bluetooth HR monitor and speed/cadence sensor) at any speed between about 3 and 20mph - it went from 60% to 95% charge in about 1.5 hours of cycling at an average speed of 14mph. It took a further 30 minutes to get to 98%, but then charging gets successively harder as you get closer to 100%. This makes it very useful for long multi-day tours, where there may be opportunity to charge the satnav overnight. NB: my front wheel has a Shimano DH-3N80 hub dynamo, and I wasn't drawing any other power from it.However,it is HUGE - compared to the mini-USB version - something I failed to grasp from the Internet images! The only convenient place to mount it is on the head tube, below the handlebars. Furthermore, it failed to charge my iPhone5. For these reasons I have only given it 3 stars. To be fair, the latter complaint may be Apple's fault, and I am due to test it with my son's Android phone - after which I will update this review.

This is OK for charging up your phone. You may need to travel for a about 5+ hours for a full charge from about 10 percent.Did not power my Garmin GPS in any meaningful manner. The batteries still died on me even when I had this attached to it.Will not be using mine in the future....