Hi @threekay I like your approach. I don't know your power drain details for your Pi or the wattage of your solar charger, but thinking about the Lantern, I came up with the following:
My Lantern draws 790 mA from my Boston Power 5300 3.7 volt Lipo to run the CHIP, SDR, and LNA when external power is disconnected. CHIP bootup without the SDR/LNA is 600 mA. These numbers came from an in-line amp meter on the Lipo leads.
I can run about 5 hours without external power from a fully charged Lipo which is only 3900 mAh of power from a 5300 mAh Lipo. As the Lipo discharges, the output voltage drops below the CHIP's operationally acceptable level and shuts down.
That said for example - - for 8 hours of direct sun when the Lantern runs directly off the solar cell, and recharges the Lipo for the 16 hours of darkness, I would need a battery reserve of 16 hours x 790 mA = 12,640 mAh for nighttime operation - - a large battery. No margins here or reserves for the dark rainy days, so I'd probably double the Lipo's size in practice.
During the 8 hours of sun, I would need solar power on the order of 8 x 790 = 6,320 mAh. So my solar array would have to generate enough energy to do the 8 hour daylight run (6,320 mAh) and provide the recharge of the 12,640 mAh for the 3.7 v Lipo's nighttime operation.
You would have to calculate the wattage of the solar array to do that based on how you store the solar energy.
Does this sound correct? So if it is correct, I can't see Outernet building that kind of storage into a single board product that would run at 790 mA, and they would have to throttle down to some other acceptable level. Alternatively they could design a single board that runs at way less power. Ken