A BQ24210 Charger for Your Space-Constrained Portable Applications
This solar-powered lithium-ion battery charger is designed for projects like data loggers and environmental monitoring systems.
If you are looking for a portable charge where there is no electricity supply, then Curious Electric Company's solar lithium-ion single-cell battery charger based on Texas Instruments IC BQ24210 may solve your problem. The charger is essentially designed for projects like data loggers and environmental monitoring units.
The solar charger is built around the BQ24210, which is a single-input, single-cell lithium-ion battery charger IC measuring just 2mm x 3mm in size with bidirectional power flow capability.
The hardware comes with the main components pre-soldered, but you need to solder the battery holder, screw terminals, and a small solar panel. It's worth noting that the 18650 lithium-ion cells and solar panels are not including with the charger.
All instructions to solder the components are available on Curious Electric's GitHub repository. However, if you are interested in the functional block diagram, it can be found in the BQ24210 IC's datasheet. The Solar Charger BQ24210 is currently selling on Tindie for $17.