Xiaomi Mijia Sensor CR2450 Battery Tray

Description

The Mijia LYWSD03MMC temperature / humidity sensor is tiny and works great. The battery life is fine, but what if it was even better? This is a modification to the battery tray to accept a CR2450 battery, which increases the battery capacity to approximately 2.7x the original.

• CR2032 Typical Capacity: 225 mAh

• CR2450 Typical Capacity: 610 mAh

Compatibility

This only works with Mijia sensors with no components on the back of the PCB. The most recent revision has a button and chip which are in the way of the space required for the larger battery.

✅ Compatible	❌ Not compatible

Print Settings

To ensure the clip and clip-cut outs work correctly, I recommend printing at fine layer settings with a 0.4mm nozzle. 0.12mm layer height worked well for me.

4 top and bottom layers, 2 walls and 5% infill is plenty.

Use Inner-Outer-Inner walls to get the highest precision outer walls to ensure the clip areas print best.

Print upside-down with supports around the screw holes and at the bottom. All other areas will bridge fine without supports.

Installation

1. Pull the back cover off the sensor

2. Remove the battery

3. Unscrew the screws (a tiny torx driver is required - unsure which size, less than T6)

4. Pull the battery tray out

5. Replace with the new tray

6. Cover up Gnd, Reset, P3 pads with tape

7. Re-install screws

8. Remove foam pad from back cover and discard (or re-use on your cabinet doors!)

9. Insert CR2450

10. Re-install back cover - note that the cover holds the battery in place now.

Cover Gnd, Reset, P3 pads with tape

Remove foam pad and discard (or re-use on your cabinet doors!)