The OpenBattery, depicted in the following image, is an interface board for the OpenMote-CC2538. The OpenMote-CC2538 is connected to the OpenBattery using the XBee header and has a 2xAAA batery holder to provide energy to operate autonomously. The OpenBattery includes a switch to power on/off the board, as well as three different digital sensors: a temperature/humidity sensor (SHT21), a acceleration sensor (ADXL346) and a light sensor (MAX44009). All the sensors are interfaced with the OpenMote-CC2538 using the I2C bus.
Here you can download the OpenBattery Schematic.