The Challenge/Problem

When experimenting with low power, mesh networked IoT nodes outdoors there a bunch of power features that would make it easier to quickly prototype and deploy these nodes.

• Solar power input. 
• 18650 battery.
• Zero drain battery voltage monitoring. 

The Solution

So the solution here is going to totally be a standing on the shoulders of giants job.  Most of the hard work has already been done by Adafruit.  This project builds on a couple of different Adafruit projects and I acknowledge, credit and thank Adafruit for their awesome products and engineering. 

So the perfect form factor for a prototyping Solar/battery IoT nodes is the feather platform. You can then choose from a whole range of micro’s and different radio configurations.

https://www.adafruit.com/feather

https://learn.adafruit.com/adafruit-feather/feather-specification

Adafruit have already done the hard work and have a Solar Lithium Ion Battery charger.

https://www.adafruit.com/product/390

What I’m planning on doing for version 1 is build a PCB that is a FeatherWing that integrates the Adafruit solar lithium ion battery charger module, onboard 18650 battery holder, zero drain battery voltage monitoring circuit and a power switch (that switches the enable pin on the feather).

With mounting holes and the on board battery holder it will make for a very neat and easy to ingress protect/mount/enclose IoT node.