The battery device is called battery.
The battery object gives the following informations about the iRobot battery.
The charge attribute in mAh, the estimated battery and the
capacity attribute in mAh. The battery internal
temperature attribute and its power source
attribute (none, power station or adapter).
It also indicate the battery current voltage in mV and its
current (val or current) in mA.
The state indicates if the battery is charging.