This version of the API shipped with Indigo 6 beta 10 - check the API Version Chart to see what version of the API is available in which Indigo versions.
batteryLevel attribute to device instances to return the current battery level (integer, 0 to 100) for devices that report their battery level. Devices that do not report battery level will return the None object.energyCurLevel and energyAccumTotal attributes to device instances to return the current Watts and Kilowatt hours energy usage information for devices that support energy reporting. Devices that do not support energy reporting will return None objects.