[duckymcduckface]

The problem with that is getting the batteries to surface. Underground mines operate in either of two access methods: shaft to surface or ramp to surface. In shaft to surface you use an elevator to move all the ore and waste out of the mine for processing, in ramp to surface you'll either use a conveyor belt or use trucks like these to run from where they're loaded to surface. Trucks are also used in shaft access to move ore internally but generally not to surface. In the truck to surface the swap would work but in a shaft access scenario you'd have to throw the batteries into the elevator which has an impact on the proportion of the time you use the shaft for ore. Also usually those trucks are left near where they're needed the operators get picked up at the end of their shift and the next guy gets dropped back at the equipment at the start of his shift. So positioning of these chargers would be tricky. The payoff in terms of savings in ventilation though are where the benefits come for these though. Price of electricity can be very high depending on where the mine is since it's very common to operate off grid in remote locations.

[scrumper]

Thanks, I understand that. Of course access-to-surface is another constrained resource which is no doubt already optimized for existing operations.