Lead battery needs protection against overcharging and deep discharge that is realized by two black boxes.
One box switches off solar cell when the battery voltage becomes 13V. Construction is done using a prototyping board.
Another black box protects battery for deep discharge. It switches off the load when voltage decreases below 10V and switches it back when voltage increases above 12 V. Emphasis is on low idle discharge current tha tis 5 mA.
Nice internet link about the solar charging topic is here
There is also a 12V to 5 V converter to supply digital devices, for example, cell phones that can be charged from USB. DC-DC converter one on picture is from Traco Power and draws 25 mA when idle. That is quite much. The one with smallest idle current of 5.5 mA was found from PowerTrends 78 SR 105 VC with specs 30 V in, 5V 1.5A out.