Electric Dump Truck Produces More Energy Than It Uses
hackaday.com
hackaday.com
Anyways, it’s totally possible that they’re using some power wasting technique, but they could also start the day uncharged.
It's possible that trucks being loaded and trucks queuing to be loaded could upload their excess into the mine grid and then roll down the hill fully loaded with a 100 tonne of ore and a near empty battery.
Not sure what occasional means in this contex, hard to find a train that doesn't use the grid