Where are they at with power supply? All these videos are now showing the robots untethered (and they have been for a while), but how long can they operate un

Where are they at with power supply? All these videos are now showing the robots untethered (and they have been for a while), but how long can they operate untethered? Are they just running on Lithium Ion batteries? And the new electric joint motors are more efficient than powering hydraulics?