PortableBattery

One installed portable cell. Returned by: self.battery.holders()[...].batteries[...]

Member	Returns	Meaning
.id	string	"portable_battery" (50 Wh) or "heavy_portable_battery" (100 Wh)
.level()	number	Charge as a 0-1 fraction
.wh()	number	Current charge in Wh
.capacity()	number	Rated capacity in Wh