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Soleil mounted in the solar panel case

Soleil

Open source power HAT for Raspberry Pi. Solar and USB-C charging, battery fuel gauge, and a 20µA sleep mode with programmable wake-up. Built for Nerves

€35.00

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Soleil is an open source power management HAT for the Raspberry Pi Zero and Zero 2W. It handles battery power, solar charging, and low-power sleep on a single board, with expansion capabilities.

It was designed Nerves-first, with a custom Nerves system, driver libraries on Hex, and an onboard NervesKey (ATECC608A chip) for connecting your project to NervesHub.

Power your project anywhere

Plug in a single-cell LiPo battery and your Raspberry Pi turns on. An onboard boost converter steps the battery up to 5V. A fully charged 2000mAh cell will run a Pi Zero 2W for roughly 9 hours.

Soleil charges the battery and powers the Pi at the same time from either a USB-C supply or a 6–16V DC input. That DC input accepts a solar panel directly: the charger uses a dynamic power management algorithm similar to MPPT, and an ideal-diode multiplexer avoids the voltage drop that ordinary diodes impose on solar charging.

An onboard fuel gauge reports voltage, current, temperature, and state of charge over I2C, so you can build low-battery warnings instead of guessing.

Sleep for years, not hours

Powering off a Raspberry Pi still leaves it drawing around 80mA. Soleil instead disables the 5V rail entirely through a low-power load switch, cutting the whole system down to roughly 20µA.

Wake up on schedule via the onboard real-time clock — any second up to a year out — or manually, via the onboard button or the Hall-effect switch. The Hall switch responds to a magnet through an enclosure wall, so weatherproof cases need no protruding hardware.

Soleil.sleep_for(30, :minutes)
Soleil.sleep_until(~N[2027-01-01 00:00:00])
Soleil.battery_info()

No firmware, by design

Comparable boards use an onboard microcontroller for power sequencing. That works, but it means you may need special debuggers or tools to flash and update the firmware. Soleil is built entirely from integrated circuits and works out of the box, so the design stays genuinely reproducible.

Hardware is licensed CERN-OHL-P; software libraries are MIT.

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