Yesterday evening one more array 4×1.2V rechargeable batteries (accumulators of 3000m A/h) was added in parallel to existing identical 4×1.2V battery-array.
This kept the RPi alive 10 more hours so that we have the device living about 20 hours total. But this is not enough. The goal is several months or – forever.
It looks like although the single solar panel gives high enough voltage (~5V), the current is not high enough to charge the accumulators (taking to account the winter not-sunny days). But, the device death time is at evening (17:30), that means to me that the currents from the panel were enough to keep RPi alive at the day-light hours (despite the winter overcast days).
These overcast days and dark long nights served the worst-case conditions for the experiment. This was by occasion, but this will allow to develop more robust system. We’ll need spare currents from the panels for faster charging and for additional loads (sensors and modules) that may be attached to RPi further.
One more pleasant event happened today: heat sinks finally arrived. Thus, I have applied one to the RPi undergoing the current experiment. This will make me more quiet about these warm days that are coming starting tomorrow. 🙂
These more sunny days will also show if we get better charging and longer times of staying alive with higher exposure to sun.