ESP32 boards can easily be powered by batteries, either through an external USB battery shield, or direct connection to an ESP32 board fitted with battery charger circuitry. But Miek Rankin has done something a bit different, as he designed ESP32 Coincell board based on an ESP32 Pico D4 SiP (System-in-Package) powered by a rechargeable LIR2450 coin cell battery with 100mAh capacity.

ESP32 CoinCell board specifications:

SiP – Espressif Systems ESP32 Pico D4 Wifi/Bluetooth processor

Connectivity 802.11 b/g/n WiFi up to 150 Mbps Bluetooth 4.1 LE On-board antenna

Display – 0.69″ OLED display with 96×16 resolution

USB – 1x micro USB port for charging and debugging (via CP2102N USB to TTL chip)

Sensor – LIS3DHTR accelerometer

Battery / Power Supply SE5218ALG-LF 500mA LDO power supply SL4054ST25P LiPo battery charger Socket for for LIR2450 (3.7V/100Mah battery) Consumption – 0.45mA in sleep mode

Dimensions – Small

If you don’t connect the battery, the board can still be powered through the USB port. No battery life was provided, but let’s say if you kept the board in sleep mode, a 100mAh battery should last over 200 hours @ 0.45mA, or a bit over 9 days.

The project is somewhat open source hardware with PDF schematics, Gerber files, and Arduino sample code available on Github. Mike showcases the board and sample firmware in the short video below.

Mike explains the board “was not made for any specific purpose and was a design challenge to try and made it as small as possible”, so it may never be sold directly. You can also make it yourself if you are interested, or contact Mike via his Github page if you have a specific use for the board..