Engineering360: "Locomotive to ferry freight by battery power"

The problem with battery locomotives is that they have to be stopped to charge the batteries. Most rail companies want these locomotives rolling 24/7, otherwise they have wasted capital.

Yep but a stopping passenger train could have overhead pantographs at and near each station, maybe on uphill sections also. The weight of batteries matters less on trains due to the low rolling resistance, and the batteries and solar PV panels are getting cheaper all the time. Urban buses are going to batteries, it will be hard to stop the trains doing the same. AC coil tech on the undersides can also recharge them both.

But this is a freight train. Now, admittedly, since this is a dedicated line where some energy can be recovered on the "downhill" leg of the trip, maybe this makes some sense. Overhead pantographs at the station still requires the train to be stopped to charge. Overhead pantographs along the whole track would probably be a better technical solution, but that has it's own capital expense and maintenance. Where multiple trains pass over the same section of track every day or even hourly, pantographs along the whole length makes good sense, i.e Acela between Washington D.C and Boston.

P.S. AC coil tech is horribly inefficient and very expensive. I have looked at inductive charging between loosely coupled resonant coils for an underwater charging application and the physics is daunting. There are applications for that but other factors must play into the equation or it just doesn't make any sense. I worked with the Witricity company on one of our proposal efforts and you have to have some severe requirements for that to be the best option. Obviously, charging underwater at not insignificant depths is one type of requirement that might make this a viable option in spite of all the drawbacks. Wet-mateable power connectors have limited mate/de-mate cycles due to the oil loss of the PBOF connection systems. Non-contact charging begins to look very favorable at depth. Witricity's main emphasis at the time was stationary charging of EV's while parked over inductive coils that stood several inches proud of the road surface. 80% was about the best efficiency at the time.