Electric Dump Truck Produces More Energy Than It Uses (hackaday.com)

Vehicle-to-grid[1] is a bit of a work in progress, but that's certainly the idea.

1: https://en.wikipedia.org/wiki/Vehicle-to-grid

The vehicle would just use its traditional mechanical disc or drum brakes then, as it already does all the time for harder braking

Time to bring back spark plugs? You can probably use a smarter charging algorithm and use electric power to brake. (Or maybe combine with a super cap to reduce battery wear)

Charge an electric backhoe at the top of the hill.

I have a friend who builds and rides “personal mobility” vehicles, like electric skateboards, scooters, etc. He lives up on a hill in SF and says that for his vehicles with regenerative brakes he doesn’t charge them beyond 90%. He says that they’re too small to meaningfully add the power “wasting” circuitry, so leaving the house and going downhill at the beginning of a journey would exceed 100% charge.

Anyways, it’s totally possible that they’re using some power wasting technique, but they could also start the day uncharged.

The shovels at the loading face are very often electric and have been in a number of mines since the 70s at least - they move from face to face once or twice a day on caterpiller tracks and drag fat cables behind that get protected with "drive over" plates for light vehicles.

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.

Put some bitcoin mining rigs on them.

Wireless power transmission of waste energy would be cool, lay down a long strip of antennas on the mountain road and all waste power gets dumped into a high gain directional antenna under the truck. Fringe benefits include all the flash fried wildlife you can eat.

There are some trains that can go off-grid for small sections on batter power.