FAQ
TL;DR: The Zigbee Sonoff SNZB-02D (62.5 × 59.5 mm) sends four metrics every ~5 minutes and showed ±0.2 °C spread in side-by-side tests; “worked great for two years” [Elektroda, VPSA132, post #21393874] [Elektroda, SławekSS, #21397163].
Why it matters: Picking the right wireless sensor saves batteries, avoids range headaches and feeds reliable data to your automations.
Quick Facts
• Power: CR2450 3 V coin cell, typical life 12–24 months [Elektroda, VPSA132, post #21393874]
• Display: 2.5 in monochrome LCD driven by BU9792FUV controller [Elektroda, p.kaczmarek2, post #21393683]
• Radio: EFR32 MG22 Zigbee 3.0; external 8 Mbit P25Q80H flash for OTA images [Elektroda, agendek, post #21393848]
• Measurements: temperature (-10–60 °C), humidity (0–100 % RH), battery %, link quality [Elektroda, p.kaczmarek2, post #21393683]
• Street price: ~60 PLN locally, ~30 PLN imported [Elektroda, p.kaczmarek2, post #21393683]
What does the SNZB-02D report to Home Assistant?
It exposes four entities: temperature, relative humidity, battery level (0–100 %) and Zigbee link quality index (LQI) [Elektroda, p.kaczmarek2, post #21393683]
How do I pair the SNZB-02D with Home Assistant using Zigbee2MQTT?
1) Enable ‘Permit join’ in Zigbee2MQTT.
2) Press the device reset button until the icon blinks to enter pairing mode [Elektroda, p.kaczmarek2, post #21393683]
3) Wait ≤30 s; new entities appear in HA. No vendor gateway is required.
This 3-step flow works for other Sonoff Zigbee battery sensors as well.
Does the SNZB-02D extend my Zigbee mesh?
No. Being battery-powered, it stays in ‘sleepy end-device’ mode and never acts as a router or repeater [Elektroda, p.kaczmarek2, post #21393683]
Which chips are inside and why the extra flash?
Main MCU/radio: EFR32 MG22 (C224HG marking). The extra 8 Mbit P25Q80H SPI flash stores over-the-air (OTA) firmware images—“external flash memory probably for OTA image storage” [Elektroda, agendek, post #21393848]
How accurate are the readings?
Side-by-side tests of 11 Xiaomi Mi2 sensors showed ±0.2 °C and ±1 % RH spread [Elektroda, SławekSS, #21397163]. The Sonoff uses a similar AHT/SHT-class element, so expect comparable indoor accuracy.
What battery life can I expect?
A comparable AAA-powered display ran 24 months before its first recharge [Elektroda, VPSA132, post #21393874] Coin-cell units typically last 12–18 months when reporting every 5 minutes.
Can I change the report interval or delta?
Yes. Zigbee clusters allow you to set periodic reporting (250 ms–hours) and/or value-change triggers. Configure right after onboarding while the device is awake [Elektroda, agendek, post #21395169]
What range issues have users seen?
One AAA-powered display lost connection beyond a single floor, despite using a ZTU module [Elektroda, @GUTEK@, post #21414679] Add a mains-powered Zigbee router or move the sensor closer to improve LQI.
Is there an edge-case where reconnection is slow?
Yes. An Aqara sensor needed 32 hours to resynchronize after two days offline [Elektroda, krzbor, post #21394818] Picking devices with better re-join logic avoids such delays.
How do Bluetooth alternatives compare?
Xiaomi Mi2 (BLE) costs ~25 PLN, transmits every 15 s, and its CR2032 battery lasts ~12 months [Elektroda, SławekSS, #21393971]. It lacks mesh routing but reconnects within a minute [Elektroda, SławekSS, #21394948].
Can one ESP32 act as a gateway for many BLE sensors?
Yes. Users run Tasmota32-Bluetooth on an ESP32, apply MQTT rules for each MAC, and gather data from up to nine sensors per node [Elektroda, SławekSS, #21394049].
What extra statistic highlights longevity?
An RTX TS0201 Zigbee thermometer still showed 100 % battery after 12 months of operation [Elektroda, krzbor, post #21394818]
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