452e0d97_HAL_0_5_14_Specification__Description
[Key (type)] battery.reporting.unit (string) [Values] Examples: mWh, mAh, percent [Mandatory] No [Description] 
The physical unit used by the charge level properties (maximum and current) as reported by the hardware. In many cases, this property is omitted - which indicates that the charge properties are measured in some unknown units.
HAL 0.5.14 Specification
Description