I want to build an “always on” Inky Frame 4.0" (PIM654) so I wounder if I can combine it with a Galleon 400mAh Hard Case LiPo Battery (BAT0016) and a 3.0V 100mA Polycrystalline Solar Cell (KIT-3604)?
If so, how do I connect the solar panel to the InkyFrame, can I just connect it to - and V+ on the extension header on the back? Or do I need additional hardware for charging the battery when solar energi is available?
My use case would be something like, connect to wifi and fetch data, update screen and then deep sleep for ~10min and repeat.
I have tried something similar but this does not work without a special breakout in between. The problem is that the solar cell only delivers 3V at no load (open-circuit, right side of the graph below). As soon as you attach a load, the voltage drops to a level that won’t power anything. The usable range is very small as you can see.
If you search the internet, you will find similar curves, often for different lighting conditions.
Adafruit has a solar-charger which has connectors for a panel, a battery and a load. But you still have to be careful with what you attach. A 3V panel is definitely not enough, you need at least two of them (and a lot of sun).
I did some power profiling for the Inky Frame 5.7. This is a MicroPython program reading off the micro SD card and not (intentionally) starting up the Wi-Fi: YouTube: Nordic Power Profiler Kit II and Pimoroni Inky Frame
I’ve been using this Adafruit charger, a 6V solar panel and a Galleon battery for my Enviro weather station if that helps - though you could probably get away with a less beefy 6V panel!
Yes the charger @hel linked to is the way to go. Note that Adafruit has also an older solar-charger, but the old one does not regulate the output to the load and could therefore supply more than 5V in full sunlight. Which is too much for most MCU-boards.