My second solar setup did not fare well:
Started during the day, with the supercap charged up in bright daylight behind a window, it was able to power the JeeNode for about 16 hours – and then in the middle of the night it gave up:
L 02:36:44.743 usb-A600dVPp OK 17 30 4 0 0 L 02:37:48.074 usb-A600dVPp OK 17 31 4 0 0 L 02:38:51.402 usb-A600dVPp OK 17 32 4 0 0 L 02:39:54.725 usb-A600dVPp OK 17 33 4 0 0
Times are in UTC and we’re in the CEST time zone, so this was two hours later – i.e. around 4:30 AM.
I left it there for another few days, but unfortunately once dead this setup never recovers. The main reason for this is probably that the RFM12B starts up in a very power hungry mode (well, relatively speaking anyway) with a 0.6 mA current consumption – because it starts with the crystal oscillator enabled.
Maybe the self-leakage of the supercap was still too high, and would be (much) lower after a few days in the mostly-charged state, so I’m not ruling out using supercaps just yet. But as it stands, not getting through even a single night is not good enough – let alone being used in darker spots or on very dark winter days.
More experimentation needed!