The Anonymous Widower

More On Tri-Mode Stadler Flirts

In the July 2018 Edition of Modern Railways, there is an article entitled KeolisAmey Wins Welsh Franchise.

This is said about the Stadler Tri-Mode Flirts on the South Wales Metro.

The units will be able to run for 40 miles between charging, thanks to their three large batteries.

In Tri-Mode Stadler Flirts, I said this.

I would expect that these trains are very similar to the bi-mode Stadler Flirt DEMUs, but that the power-pack would also contain a battery.

As an Electrical and Control Engineer, I wouldn’t be surprised that the power-pack, which accepts up to four Deutz diesel engines, can replace one or two of these with battery modules. This could make conversion between the two types of Flirt, just a matter of swapping a diesel module for a battery one or vice-versa.

Note that the three-car Class 755 trains for Greater Anglia have two diesel engines and the four-car trains have four engines.

So could it be that the tri-mode Stadler Flirts have three batteries and just one diesel engine in the four slots in the power-pack in the middle of the train?

I wonder how much energy storage you get for the weight of a V8 diesel, as used on a bi-mode Flirt?

The V8 16 litre diesel engines are made by Deutz and  from their web site, it looks like they weigh about 1.3 tonnes.

So how much energy could a 1.3 tonne battery store.

The best traction batteries can probably store 0.1 kWh per kilogram. Assuming that the usable battery weight is 1.2 tonnes, then each battery module could store 120 kWh or 360 kWh if there are three of them.

How Far Would A Full 360 kWh Battery Take A Three-Car Flirt?

In an article in the October 2017 Edition of Modern Railways, which is entitled Celling England By The Pound, Ian Walmsley says this in relation to trains running on the Uckfield Branch, which probably has a terrain not much different to the lines to the South and West of Cardiff.

A modern EMU needs between 3 and 5 kWh per vehicle mile for this sort of service.

This would mean that a 360 kWh battery would take a three-car train between twenty-four and forty miles.  The claim in Modern Railways of a forty mile range, isn’t that out of line.

How Much Energy Is Needed To Raise A Three-Car Flirt From Ystrad Mynach To Rhymney?

In Tri-Mode Stadler Flirts, I estimated the following about the weight of three-car Flirt.

  • I reckon, that the weight of the train will be around 130 tonnes.
  • I will assume 150 passengers at 80 Kg. each, which gives a weight of 12 tonnes.

Raising it through the 125 metres between Ystrad Mynach and Rhymney, will need 48 kWh.

But what about stopping and starting at the seven stations on the route?

At every stop, a proportion of the energy will be recovered. If 20% is lost at every station, I think we can add about another 20 kWh of energy use.

And then there’s the power rneeded to run the train. Using the Ian Wa;msley formula shown earlier, we get between

three-cars x 10 miles x 3kWh and three-cars x 10 miles x 5 kWh or between 90 kWh and 150 kWh.

It would appear there is certainly enough power from a full battery, that will have been charged all the way from Cardiff to drive a three-car Flirt up to Rhymney on battery power.

For a four-car train my weight estimate is 166 tonnes, which means Raising the train between Ystrad Mynach and Rhymney, will need 57 kWh.

I estimate that losses for stopping and stasrting would be about 24 kWh

Train running power would be between 120 kWh and 200 kWh.

It would still be possible to go between Ystrad Mynach and Rhymney on battery power.


It looks to me, that Stadler have designed a tri-mode train on steroids!

June 28, 2018 - Posted by | Transport | , , ,


  1. You may almost certainly have to know about these concerns at the same period, in case you also
    are trying to find a similar alternative.

    Comment by Silvia | November 21, 2018 | Reply

  2. according to a recent press release Stadler are ‘about to kick off the project’.

    Comment by Peter Robins | March 20, 2019 | Reply

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