Please excuse me if I have inappropriately categorized my post.
I'm in the process of searching for information as self-titled. I am working on a project that features a pair of solar charged lithium phosphate batteries, specifically, 850mAh 3.2v LiFePo, two cells connected in parallel. I started out the project with a solar powered garden light, but at this point, I would like to move away from the OEM circuit board that came with the light. I'll be using these batteries, in tandem of course with a solar charging circuit, and a voltage step-up circuit to power a very very generic ESP8266-12E. The purpose is data collection. I'll be taking measurements of soil moisture, temperature and humidity periodically and recording this data with timestamp to a CSV file that will be stored in SPIFFS and later offloaded to a micro-sd card. I'll also be displaying graphs on a web interface hosted by the ESP.
So back to the point, the issue I'm running into now is finding an acceptable circuit or schematic that is purpose-designed to charge this type of battery using a PV. I know from testing that in direct sunlight, the PV that came with this light outputs ~3.8 volts.
As for the voltage step-up circuit, I imagine I could use one of a number of off-the-shelf solutions that will give me 5v and around 300-500mA. I'm also looking at several very similar schematics that will do this. so really, my only stumbling block currently is the charging circuit. I'll be attempting to logically deconstruct the solar light circuit to a functional schematic, but I have a feeling this schematic or one similar has already been published and I'm just using the wrong syntax when asking Google for help finding it.
If anybody has an idea, recommendation or suggestion for this dilemma, please share your insights here. I would greatly appreciate it and it's bound to be useful to some other folks as well.
Please let me know if I have left out any critical details.
Thank you.