Symptoms
- Random reboots or freezes under load (Wi-Fi traffic, USB disks, radios).
- USB devices (SSDs, Zigbee or Bluetooth dongles, modems) disconnecting.
- SD card or filesystem corruption after some weeks.
- "Undervoltage detected" in the kernel log (
dmesg), andvcgencmd get_throttledshowing bit 0 or bit 16 (see the throttling item).
What the hardware needs
| Model | Connector | Recommended supply |
|---|---|---|
| Raspberry Pi 1, 2, 3 | micro USB | 2.5 A micro USB supply |
| Raspberry Pi 4 / 400 | USB-C | 3 A USB-C supply |
| Raspberry Pi 5 | USB-C | 27 W USB-C supply (5 A at 5 V) |
All models need 5.1 V. On Pi 5 the supply also decides how much current the USB ports may deliver: 1.6 A with a 5 A supply, 600 mA with anything else. An SSD or radio dongle that works on the bench can brown out on a 3 A supply.
Other official numbers worth knowing:
- The GPIO pins can safely draw 50 mA combined, and 16 mA per pin. Don't power sensors or relays from GPIO pins; use the 3.3 V / 5 V rails or a separate supply.
- No Raspberry Pi model supports USB-PPS.
- A Pi 5 draws around 1–1.4 W when shut down by default;
POWER_OFF_ON_HALT=1in the EEPROM config (sudo rpi-eeprom-config -e) drops this to around 0.01 W. Useful for battery or solar installations.
Checklist
- Use the official supply for the model, or one that explicitly supports the required current at 5.1 V.
- Use short, thick cables; thin cables cause voltage drops even with a good supply.
- Power hungry USB devices (disks, modems, some antennas) through an externally powered USB hub, but avoid hubs that back-power the Pi.
- Check after deployment:
vcgencmd get_throttledshould be0x0, anddmesgshould show no undervoltage messages. - For installations where power can drop suddenly, also read the item on preventing SD card corruption.