edwin_m
Veteran Member
In principle that's possible for trains, although it would involve major changes to the control system which would require a lot of design effort as well as safety approvals. For vehicles built for the AC supply the batteries could replace the transformer, but for DC space would need to be found and the structure would have to be good enough to support the extra weight. This would all end up being a fairly drastic modification of what (given the small amount of preserved electric traction) may well be the only survivor of its type.Thus it is possible to envisage electric traction running off batteries, only a little larger than those in cars, given adequate starting current, rather like the class 230's. There would be some adjustment to circuitry and control, as well as ancillaries. Any demand for third rail or OLE would be really only cosmetic, even the 200V (or tramway 550V) needed could mostly be better provided from batteries.
Trams on the other hand don't have much spare space. The traction resistors might be replaceable, but may not free enough volume for a worthwhile battery, and only at the cost of sacrificing the traditional controller (very visible and part of the tram experience) or interfacing it to a modern electronic drive. Unlike preserved trains, preserved trams may well run at speeds where the motor needs full line voltage, so a lower voltage solution won't work here unless the motors are modified/replaced too. Seeing as the tram preservation fraternity seems to have no problem safely providing the traditional overhead supply, and it doesn't have the actual or perceived risk issues of third rail, I can't see any of them attempting this sort of conversion.