rpigear Raspberry Pi Solar Panel Module

I tested this HAT extensively in some pretty brutal conditions before writing this review. By brutal I mean temperature swings of 40F degrees reaching the max thermal limits of the hardware.What this pricey HAT offers over other solutions is space-savings and control. You will not find a smaller package that offers the ability to sleep the Pi and then wake it up based on any combination of: button, battery volts, solar volts, time, pin-shorting. That last one lets you wake up the Pi based on any external hardware you desire. Want to wake up the Pi using an SMS text message? Doable!—with other hardware.The ability to sleep the Pi and wake it up is crucial for remote outdoor applications where the system must survive on its own, with only the sun's energy to keep it going.Everything is well-documented and setup is an absolute breeze. CLI commands allow you to read the state of the battery or solar panel, initiate sleep, etc.Ironically, the one aspect of this Solar HAT that could use improvement is its solar charging. Oh it works!—but it's not MPPT, and the battery charger can only output up to 2A (at a user-defined voltage). The good news is that a separate DC/DC step down converter is used to power the Pi itself: 3A continuous and 4A peak. So the 2A sent to the battery is not consumed by the Pi (unless there's not enough wattage coming from the panel).Frankly, I find this dual step down design confusing and limiting. Imagine that you want to sleep the Pi during the day while the sun is out and the battery is charging, and only use the Pi at night. Well you've now "lost" the 3A (15W) from that second step down converter. It's not being used and is not helpful at all. In this case, it would be far better to have all the amps going directly to the battery, instead of 2A to the battery and 3A going nowhere.A better design would be a higher-amp step down converter to charge the battery, and a separate converter for powering the Pi from the battery. In other words, the Pi should always be powered from the battery, and the battery gets all the amps from the panel.It would also be nice if the RTC had a supercap or coin battery backup.