This is a graph of solar power currents over about 12 hours. It began near the end of the day with the battery mostly charged from the morning's light.
The battery current explained:
The battery just has a small trickle charge of about 10 mA to maintain it. About ¼ of the way into the graph, the sun begins to set and the battery current begins to waver as the solar panel can no longer maintain the trickle charge. About half way through the graph the light has dropped enough that the solar panel is just able to break even. At 0 mA the solar panel is able to supply the computer but give nothing to the battery. After this point the battery current becomes negative as the computer is now drawing on the battery for what the solar panel cannot provide. The last part of the battery trend shows the battery discharging steadily. At this point, the sun is no longer providing power—just the battery.
The computer current explained:
The computer current is mostly flat, except for some fetchers right at the beginning. Because I got this setup running near the end of day light, the current numbers were pretty small. I needed to be sure things were connected properly, so I had the Sun Dragon start running some heavy computation to increase it's current draw. I did this three times, visible as three current spikes. Aside from these the current is pretty steady. There is, however, a slight increase as the sun begins to go down. This is because as the sun sets, the system voltage drops from around 14.5 volts to around 13 volts. The power required by the idling computer remains the same. So when voltage drops, current must increase. Thus the slight increase in current as the sun sets.
The solar panel current explained:
The solar current seems to track the battery current, except for the spikes when the computer is drawing higher current. The spikes at the beginning show the solar panel has enough light to fully supply the computer and the battery trickle current. In fact, much of the solar energy now received by the solar panel is unused because the battery is fully charged—there is no need for the excess energy.
With this set of data clearly working, it was time to wiring the A/D converters to the Sun Dragon.