Hi. I have a 20W solar panel with Vlp=16.9V, Ilp=1.2A. I am thinking about building a system that can produce power to two Arduinos that draws maybe 500mA at most.
My simple idea is to connect the panel to a dc/dc step down converter to 7.2V through a forward diode, then connect the 7.2V output to 6 Ni-Cd connected in series. The output of the battery then goes to the onboard DC regular of the first Arduino, and connect its 5V pin to the 5V pin of the second Arduino.
This is the dc-dc converter I am considering to get:http://www.ebay.com/itm/DC-DC-Converter-Auto-Boost-Buck-2A-18W-3-35V-to-1-2-30V-/271157070361?pt=LH_DefaultDomain_0&hash=item3f22388a19
Both Arduino is going to be located in an extremely remote location and I expect it to keep operating for a long time. So do you think the system is going to work? There is no current control element in my circuit to restrict the charge rate. Is it going to be a problem? Do I need another diode goes from the output of the dc/dc converter to the battery? Thanks a lot.