🛠 Alimentation et consommation : le point faible de la Zero

Goal

Learn how the Zero consumes power and why the supply is the most fragile point of this board. Official figures: idle average 0.10 A, typical active 100 mA, H.264 video 0.23 A, stress max 0.35 A, halted 0.055 A — roughly 0.5 W idle and under 2 W stressed at 5 V.

Why it matters

The official recommendation is a 5 V / 1.2 A supply over micro-USB. And the Zero range has a documented trap: it has no undervoltage detection (unlike every model since the Pi B+ in 2014). A sagging 5 V rail produces no warning message — only SD corruption and random lockups.

Measure it

# Temperature: progressive throttling 80-85 C, hard limit 85 C
vcgencmd measure_temp

# Throttle flags — but the undervoltage bit is meaningless on a Zero,
# because the board cannot sense the rail at all:
vcgencmd get_throttled

# Load test while watching an inline USB power meter:
sudo apt install sysbench
sysbench cpu --cpu-max-prime=20000 run

A cheap inline USB power meter is the only honest undervoltage detector on this board.

Check

Around 0.1 A at idle, under 0.4 A in stress with a healthy supply. If the voltage at the board sags below ~4.75 V under load, change cable/supply before trusting the SD card with real data.

Pitfalls

• Trusting vcgencmd get_throttled to prove the supply is fine: the Zero literally cannot detect a brownout.
• Long, thin micro-USB cables: large voltage drop, SD corruption at boot current peaks.
• Powering from a PC USB port: explicitly discouraged — voltage often sags.
• Sealed cases in the sun can still reach 85 C despite the sub-2 W draw.