GitHub - sparkfun/Photon_Battery_Shield: Battery Shield for the Spark Photon. Has a charging circuit, as well as a fuel gauge.
SparkFun Electronics, Inc. - Don't miss out on our Deal of the Week! The SparkFun Battery Babysitter is half battery charger, half battery monitor, and all you'll ever need to keep your
SparkFun Photon Battery Shield
SparkFun USB LiPoly Charger - Single Cell - PRT-12711 - SparkFun Electronics
Amazon.com: SparkFun ESP32 Thing Developement Board WiFi & microcontroller compatible with Bluetooth for IoT & prototyping projects w/ Integrated LiPo battery charger 4MB flash memory 3 to 3.6V operating range : Electronics