TL;DR
A new accumulator train wagon that can hold a charge (loses charge slowly over time) with a new charge/discharge structure (similar to pumps) that needs to be hooked up to a power grid.What?
A new technology that unlocks a train wagon that works as an accumulator but wagon needs to be "connected" to a new charge/discharge structure when stationary for the train to charge or discharge (depending on mode of structure). The new structure that charges/discharges would be configurable by circuit which mode to use.Why?
It would be an interesting and fun alternative to providing outer bases with power other than placing long lines of power poles. Power poles would still be superior, but it could be a good and fun way for temporary mining bases.It might even be a prerequisite for an electric train engine
or laser turret wagons.