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Comment by dredmorbius | Hacker News Reader

You'd almost certainly do better to have the storage at a stationary off-track location rather than as part of the trainset.

Batteries are massive (in the weight sense), and frequent acceleration and deceleration as well as safety would be major concerns.

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The reason people look to battery trains is to avoid the infrastructure costs of the overhead lines / third rails, substations etc. to get electricity from trackside to the trains. The costs can be difficult to justify for smaller branch lines. A train that can use overhead lines on the main lines, then switch to battery for a branch is (hopefully) greener / more efficient than say running a diesel under the wires all the way[1].

It is a bit of a case of shuffling costs from infrastructure to rolling stocks, trains with batteries would still cost more than a pure overhead line electric, but I guess it comes from a different budget...

I'm not sure of any real reason why you'd use a battery off-track instead of a connection to the electricity grid except as some sort of backup for a power failure?

[1] Bi-mode diesel / electrics also exist of course, which solve the problem in a slightly different way (insert NOX / CO2 v Lithium mining debate here).

You don’t need massive batteries for short regional/suburban branch lines. We’re not talking about long intercity routes here.

For NYC diesel trains, you're talking about stretches like the one from Croton-Harmon to Poughkeepsie (by car, it's about 40 miles). I'm not sure whether this counts as "short."

https://www.reddit.com/r/nycrail/comments/l57nw2/map_of_the_...

(LIRR Montauk branch is longer, but I'm less familiar with it.)

It's not the length of the line.

It's the duty cycle of the rolling stock.

Running a trainset four times along a 100 mile route, or 40 times along a 10 mile route, you're still travelling 400 miles.

And the stop frequency is likely far higher on the urban route. It's the acceleration that costs, and batteries only save you so much there, even with regenerative braking.

Add in heating/cooling loads, air handling, etc., and there's a lot to consider.

About the only place batteries make sense on rail is where you're moving a heavy load one-way down-grade. There are operating quarry and logging operations which effectively work as battery storage. Laden cars (or trucks) run downhill, whilst regenerative braking charges the batteries. Empties return uphill, slowly, on that charge.

Other than a Soylent Green operation from a mountain resort, few commute rail systems have a suitably matching travel pattern.

Could make sense for short distance, low frequency. I know of a few services on branch lines that have long linger times at stations. They will do a 10 minute journey twice an hour and stay in the station between trips.

> "Running a trainset four times along a 100 mile route, or 40 times along a 10 mile route, you're still travelling 400 miles."

We're not talking about 100 miles on battery power here - although there are already battery electric transits that are capable of that and more. For the most part, inter-urban trunk lines in Europe are already electrified.

There are many outer-suburban/regional routes that are, for example, 50 miles along an electrified trunk line then 25 miles on an un-electrified branch line. Currently that means whole route needs to be operated by diesel trains. But a battery train only needs to be capable of doing (eg) 50 miles on battery, then it can recharge when it's running under the wires.

Do you have any references for serious studies or proposals for such systems?

Not just proposals: orders have been placed and trains should be in passenger service this year. Google "FLIRT Akku" which is the name of Stadler's battery-electric train.

https://www.urban-transport-magazine.com/en/schleswig-holste...

"The longest non-electrified section on the diesel network is 80 km. Under optimal conditions, however, a battery range of 150 km should be possible."

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