🛠 Budget énergétique : dimensionner une Zero sur batterie

Goal

Design a battery build around the Zero's measured consumption instead of folklore. Official table: idle average 0.10 A, typical active 100 mA, H.264 playback 0.23 A, stress max 0.35 A, halted 0.055 A — at 5 V that is ~0.5 W idle, under 2 W stressed.

Measure your own profile

vcgencmd measure_temp     # throttling 80-85 C, hard limit 85 C
sudo apt install sysbench
sysbench cpu --cpu-max-prime=20000 run   # watch an inline USB power meter

sudo halt                 # halted state: 0.055 A per the official table

Sizing math

A 10 Ah / 37 Wh Li-ion pack through a 5 V buck converter (~90 % efficient): idle ≈ 0.5 W / 0.9 ≈ 0.55 W, so roughly 37 / 0.55 ≈ 65 h. Add a 60 mA sensor node and you still clear 40 h. Duty-cycling — halt between sensor reads — is where the 0.055 A halt figure pays off.

Trim it down

• Raspberry Pi OS Lite: no desktop, less idle work on 512 MB RAM
• A fast, quality SD card: swapping on the Zero burns power and dies young
• Verify inside the sealed enclosure with vcgencmd measure_temp — even under 2 W, sun-baked cases can reach 85 C

Pitfalls

• Buck converter quiescent current can rival the Zero's own idle draw at light load — measure the whole chain, not just the board.
• Trusting vcgencmd get_throttled for supply health: the Zero range has no undervoltage detection at all.