I have a 58 Farad supercapacitor bank that worked well at Field Day. It was charged using a solar panel. That is a great setup. I made five natural power QSOs at Field Day with the supercapacitor and the KX3. I ran into the K-Tor website and decided to try the "Power Box" which uses pedals. Pedals are much easier to deal with than a hand crank. A human powered generator would work if there are clouds or it is after dark.
The "Power Box" threw me at first as it puts out 110 volts DC. Yes DC. I have learned that most chargers and wall warts are the switching type. Those devices can operate on DC as well as AC. Now the "power Box is rated at 20 watts. You can use what ever charger you device would normally use to convert the 110 volts DC to the correct charging voltage.
In my case I am using a 10 watt charger to charge the supercapacitor as if it were a battery. Now I don't plan to charge the capacitor from zero volts to working voltage. I can do that with a solar panel. The supercapacitor loses about one percent a day due to the balancing circuit. That is pretty good really. So the main thing is to replace what I use to make QSOs. I found it takes about four minutes to go from 13 volts to 12 volts with the 210 ma draw from the KX3 on receive. It takes about 1.5 minutes of pedaling to put that energy back.
I had a QSO with KP4CPC today and the voltage went down from 13 volts to 10 .75 volts running five watts CW. OK it seems it took five minutes of pedaling to get it back to 13 volts. The charger was putting out 700 ma. I may find another charger that would double that current. But hey exercise is part of the RaDAR game. So there you go! Actually a cool night would be better for pedaling but I was just testing.
I think this device will be interesting for the next Field Day and makes a good educational tool. In fact, I might get others to do the pedaling!