Xiaomi’s temperature and humidity sensors are among the most popular smart home devices due to their accuracy, compactness and integration with the Mi Home/Aqara ecosystem. However, even such reliable gadgets require maintenance: over time, the CR2032 battery runs out and the sensor stops transmitting data. In this article, we will discuss how to replace the power supply in different models of Xiaomi sensors without damaging the case and maintaining tightness.
The replacement process seems simple, but there are nuances, from the type of mounting of the lid to choosing the right battery. Mistakes can lead to loss of leakage (critical for the bathroom), damage to contacts, or even failure of the sensor. We collected step-by-step instructions, comparison tables of batteries, and answers to frequent questions — for example, why a new battery goes down quickly or how to reset the sensor after replacement.
The article is relevant for all modern models: Xiaomi MiJia Bluetooth Temperature and Humidity Sensor (LYWSD03MMC, LYWSD02), Aqara Temperature and Humidity Sensor (WSDCGQ11LM), ClearGrass CGDK2 and their analogues. If your model is not specified, check the battery type in the specifications (usually CR2032 3V).
What are Xiaomi temperature sensors and how they differ
Xiaomi and its sub-brands (Aqara, ClearGrass) have several lines of temperature and humidity sensors, which differ not only in design, but also in the way the lid is attached, the type of battery, and even the communication protocol, which is important to consider before replacing a battery.
Main models:
- 🔹 Xiaomi MiJia LYWSD03MMC — The most common sensor with Bluetooth 5.0, battery CR2032 It's got a magnetic lid attachment, and it supports firmware for Home Assistant.
- 🔹 Xiaomi MiJia LYWSD02 — It's an outdated model with a more fragile body, and it's locked with latches that are easy to break.
- 🔹 Aqara WSDCGQ11LM — It's Zigbee protocol, battery. CR2032, The body is more sealed (suitable for the bathroom).
- 🔹 ClearGrass CGDK2 — budget analogue with simplified mounting of the cover (unwinds counterclockwise).
The main difference is the way the lid is fixed, for example, in the LYWSD03MMC it is held on magnets, and in the WSDCGQ11LM it is held on threads. If you apply force where you don't need it, you can damage the body or contacts. Some models (for example, Aqara) have a rubber pad to protect against moisture, which you can't lose when you replace the battery.
Signs of a discharged battery: when it is time to change
Xiaomi sensors don’t always explicitly signal low battery life, and in some cases they just stop transmitting data, and in others they start behaving unstablely, and here are key signs that the battery needs to be replaced:
- 📉 Data is updated less frequently (for example, every 30-60 minutes instead of 5-10 minutes).
- 🔋 The app appears a notification “Low battery” (not all models support this feature).
- 📡 The sensor periodically “disappears” from the network and reappears.
- 🌡️ Temperature/humidity readings become inaccurate (e.g. humidity is always 99% or temperature jumps).
- 🔌 The LED does not light up when you press the reset button (if it is in the model).
The average life of the CR2032 battery in Xiaomi sensors is 1 to 2 years, depending on the frequency of data transmission and ambient temperature. If the sensor is installed outside or in an unheated room, the battery can sit down faster due to extreme temperatures.
⚠️ If the sensor stops working immediately after the battery is replaced, check the polarity (+/-) And the density of the contacts, and 90 percent of the time, that's the problem, not the malfunction of the device.
Which battery to replace: CR2032 comparison
All Xiaomi temperature sensors use lithium batteries like the CR2032 3V, but not all batteries are the same. Cheap batteries can run out quickly, leak or fail to provide stable voltage. We tested several popular options and made a comparison table.
| Battery brand | Average service life (months) | Price (per 1 pc) | Pluses | Cons |
|---|---|---|---|---|
| Duracell | 18–24 | 80–120 ₽ | Long service life, stable voltage | More expensive than analogues |
| Energizer | 16–20 | 60–100 ₽ | Good Price/Quality Relationship | Can quickly sit down at low temperatures |
| Panasonic | 14–18 | 50–80 ₽ | Low self-discharge, reliable contacts | Hard to find in small shops |
| GP | 12–16 | 30–50 ₽ | Cheap, available everywhere | Fast discharge in sensors with frequent surveys |
| No-name (Chinese) | 6–12 | 10–20 ₽ | Very cheap. | Leakage risk, unstable tension |
For sensors installed in critical locations (such as a nursery or server room), we recommend using Duracell or Panasonic. If the sensor is in a dry room and is interviewed every 30 minutes, you can save and take GP.
⚠️ Warning: Never use rechargeable (battery) batteries ML2032 instead CR2032! Their tension (2.4V instead 3V) Not enough for the stable operation of the sensor, and it will constantly shut down.
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Before buying, check the battery production date – fresh cells (not older than 6 months) will last longer. The date is usually marked on the back in the format of "MM/YYYY".
Step-by-step: how to replace the battery in the sensor Xiaomi
The replacement process depends on the sensor model, but the overall pattern is the same. We'll go into the most difficult case in detail, the Xiaomi MiJia LYWSD03MMC, because it has a magnetic mount of the lid, which often raises questions. For other models, we'll give you key differences.
☑️ Preparation for battery replacement
1. Removal of sensor cover
The LYWSD03MMC has a two-magnet lid to remove it.
- Put the sensor down on the table.
- Insert a plastic shoulder blade (or mediator) in the lower right corner of the cover.
- Carefully slap the lid as you move around the perimeter, and you hear a click, and the magnets are disconnected.
- Remove the lid without making any effort - there may be wires inside!
For the Aqara WSDCGQ11LM, the lid is unscrewed counterclockwise (it takes a little force). The ClearGrass CGDK2 just shifts sideways.
2. Removal of the old battery
When you remove the lid, you'll see a CR2032 battery locked in a metal contact, and you'll be careful to put a screwdriver or tweezers on the side, and you'll be able to avoid touching the contacts with your fingers, because that can cause oxidation.
In some models (for example, Aqara) the battery can be soldered – in this case, it must be simply pulled out without making any effort to contact.
Installation of a new battery
Check the polarity: the sensor usually has a + and - mark. Set the new battery upside down (this is standard for most models). Make sure the contacts fit tightly - if the battery is dangling, bend the metal plate.
Critical: If the sensor doesn't turn on after you've replaced, check if the contact is buckled under the battery. This is the most common cause of malfunction after you've replaced it.
Sensor assembly
Carefully set the lid in place. For LYWSD03MMC, it should be magnetized with a slight click. In Aqara, turn the lid clockwise to the point, but don't pull it over, you can rip the thread.
Once assembled, the sensor should automatically turn on. If this does not happen, press the reset button (if any) or reset the sensor through the application.
What if the sensor does not turn on after replacing the battery?
How to Reset the Sensor After Replacing the Battery
Sometimes, after the battery is replaced, the sensor will not connect to the network or show incorrect data, in which case a reset is required.
- 🔄 Xiaomi MiJia LYWSD03MMC: Hold the button on the back for 5-10 seconds until the LED blinks quickly.
- 🔄 Aqara WSDCGQ11LM: Press the reset button (near the battery) 4 times in a row at intervals of 1 second.
- 🔄 ClearGrass CGDK2: Remove the battery, wait 30 seconds, then set it back. The sensor will reset automatically.
After resetting, the sensor will lose all previous settings (for example, binding to a room in the Mi Home).
- Remove the old device from the application.
- Add it again through Add the device → Sensors → Temperature and humidity.
- Set up alerts and automation (if any).
If the sensor doesn’t reset, try repeating the procedure or check if the battery contacts are dead (sometimes alcohol cleaning helps).
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After the reset, the sensor may temporarily show inaccurate data (for example, humidity is 99%), which is normal - after 10-15 minutes, the readings are stabilized.
Frequent Mistakes and How to Avoid Them
Even with the seemingly simple process, many users make mistakes that cause the sensor to fail, and here are the most common ones and ways to prevent them:
- 🔧 Using metal tools to remove the lid, which can scratch the body or close the contacts, use only a plastic blade or a mediator.
- 🔋 The battery is on the wrong side, and there's always a mark on the sensor. + and – Ignoring this will cause the device to not turn on.
- 💧 Loss of rubber gasket (in Aqara models) without it, the sensor will lose its tightness and can fail in a wet room.
- 🔌 Pressing the lid hard when assembled can damage the contacts or break the thread (in Aqara).
- 📱 If the sensor does not connect after replacing the battery, it must be reset within 5 minutes, otherwise it may "hang".
Another common problem is the rapid discharge of a new battery.
- Use of cheap or old batteries (check production date!)
- Frequently survey the sensor (for example, if the Home Assistant is 1 minute interval).
- Extreme temperatures (below -10°C or above +50°C).
If the battery goes down in a few days, check the sensor with a multimeter – it may be consuming too much current due to an internal malfunction.