Building a Solar-Powered Repeater

Here's the parts list that Austin Mesh came up with as their preferred way to build a solar powered repeater.

This design doesn’t require any soldering or complicated connectors. It also doesn’t require any battery management chips (which often have long shipping lead times and can be hard to get).
For this design the solar panel is connected directly to the battery pack via USB. Then the battery pack is connected to the board via USB.

The Voltaic Systems V25 battery is nice because it is optimized to charge from a solar panel and it is set standard to an “always on” mode which means the battery bank does not shut off after a set amount of time like other battery packs – this is useful as the RAK chip uses very little power and can trick other battery packs into shutting off.

The other really nice thing about the Voltaic pack is than when it drains down completely it shuts down, but then once the solar panel has sufficiently charged it back up it will automatically turn itself back on again. Right now they're testing the V25 battery which has 6,400 mAh, but if we were going to install a node in a very hard-to-reach place we’d probably use the larger V75 19,200 mAh battery.

The RAK radio uses between 100 and 1000 mAh per day, with about 400 mAh per day being average so theoretically the Voltaic V25 could keep the radio working for 16 days without any solar power and the V75 could keep the radio running for 48 days without solar.