Using UPS HAT UPS Module with Raspberry Pi

UPS HAT practical reference

An uninterruptible power supply HAT that seamlessly switches a Raspberry Pi to battery power during outages, common in always-on home servers. It sits between the main power source and the Pi's power input, continuously trickle-charging an onboard Li-ion/LiPo battery while mains power is present, and instantly switching over to battery when power is lost — keeping projects like home automation hubs, network-attached storage, or security camera servers running through brief outages, or at least allowing a graceful shutdown before the battery depletes.

Key specifications

• Form factor: Raspberry Pi HAT — mounts directly on the 40-pin GPIO header, matching standard Pi board dimensions
• Input power: 5 V via micro-USB or USB-C, or direct DC barrel input depending on model
• Output power: Regulated 5V to the Raspberry Pi via the GPIO header pins (bypassing the Pi's own USB power input)
• Battery: Single or dual-cell Li-ion/LiPo (18650 cells are common), charge-managed onboard
• Switchover behavior: Automatic, near-instantaneous switch to battery power on mains loss with no reboot of the Pi
• Monitoring: Many models expose battery voltage/percentage over I2C so software running on the Pi can log status or trigger a graceful shutdown before battery depletion
• Backup runtime: Model and battery-capacity dependent, commonly tens of minutes to a few hours depending on Pi model and attached peripherals

Pinout and connection notes

Because most UPS HATs deliver power through the GPIO header rather than the Pi's normal USB/barrel power input, they typically require running the Pi's official low-voltage warning to be disabled or reconfigured, and it's worth checking whether the specific HAT model leaves the rest of the 40-pin header accessible for stacking other HATs. Battery status is usually read over I2C so a background script can trigger a clean shutdown before the battery is fully drained.

• 40-pin GPIO header (pass-through): Mounts on and passes through the Pi's GPIO header, supplying regulated 5V power while typically leaving GPIO pins available for other HATs/wires
• Battery terminals: Connection points for the onboard Li-ion/LiPo cell(s), usually via a JST connector or solder pads
• Power input (micro-USB/USB-C/barrel): Main 5V power input from the wall adapter
• I2C (SDA/SCL, via GPIO pass-through): Used by many UPS HATs to report battery voltage/capacity to software running on the Pi

Integration checklist

1. Confirm the exact part number and breakout-board revision.
2. Verify supply voltage, current demand, logic levels, and signal direction against the datasheet.
3. Check controller pin assignments and bus address or interface mode against the example code.
4. Power up with external loads disconnected, then test signals before full integration.
5. If readings or communication fail, check power and ground first, then pin mapping, interface settings, and library initialization.

Troubleshooting and reproducibility

Record the board used, wiring, library/version, supply arrangement, and measured behavior. Use the selected board-specific wiring example as the source of truth. Never assume visually similar modules share identical voltage tolerance or pin order.