Hello all,
Awaiting the release of the QRP Labs U3B, I've already ordered some of those small solar panels from China to experiment with. To get some more experience with- and knowledge of those solar panels I'd like to see if I can power my U3S with them. I've got two sizes panels, one is 52x19mm and the other is 39x19mm. The panels are rated average voltage / average current 0,5 V / 0,3 A and 0,5 V / 0,24 A respectively. My U3S with QLG1 GPS together draws about 110 mA during idle and approximately 220 mA when transmitting on 40m and a little less on 20m.
Now my plan is to connect about 15 to 20 solar panels (of the 52x19mm size) in series giving approximately 7,5 to 10 V and enabling a current of 300 mA (which should be enough for the 220mA of the U3S). I then want to feed the power to a voltage regulator bringing down the voltage to a stable 5 Volts (I've made one from one of those cheap car mobile phone chargers) which lastly I connect the U3S to. I only want the U3S to be powered by the solar panels during daylight, so at this point I'm not interested in some kind of battery being charged as well.
Am I seeing this too simple, am I missing something here? Any tips and hints would be welcome. To be on the safe side with the current it also has crossed my mind to put two rows of 15 to 20 panels in parallel enabling a current of 600mA. Do I maybe also have to put in a diode in the circuit somewhere?
The biggest challenge will probably be soldering to the panels. I will follow the tips and tricks given on this group some time ago.
Best 73,
Michael PA7MDJ
