ATmega328P, 8Mhz, FIO Bootloader at 3.3V (arduino compatible)
BreadBoard friendly
Low Consumption
LIPO Battery Charger MCP73831 on board
LIPO Battery Regulator
Switch at pin D4
PCB size 45mm x 22mm (1.77inch x 0.87inch)

Running the ATmega328P at 8Mhz drops the consumption drastically. That way you can have U3 Module to run on a battery for a long time.

The onboard battery charger makes sure you can charge the battery from a solar panel, or any other source without having to use an external LIPO charger.

By placing the MCU on a sleep mode, you can drop the consumption to less then 200µA!

Just like the U2 Module, the NRF24l01 can be used, to transmit your data from and to another Arduino™.

Important. U3 is a 3.3V module! Do not connect with 5V.