The Anonymous Widower

Mathematics Of A Stadler Flirt Akku Battery Train

In Stadler Receives First Flirt Akku Battery Train Order, I  quoted this from as that of this article in Railway Gazette International.

Schleswig-Holstein transport authority NAH.SH has selected Stadler to supply 55 Flirt Akku battery multiple-units to operate regional services and provide 30 years of maintenance.

This is a substantial order for a large number of trains and many years of maintenance, and would appear to be structured similarly to deals in East Anglia, Glasgow and Liverpool in the UK.

Does The Train Have A Central Power-Pack Car?

Is the Flirt Akku, similar to Greater Anglia’s Class 755 trains and other of the companies products, in that it has a central power-pack car?

This picture shows a Class 755 train at Norwich.


Note that this four-car train has four full-size cars and a shorter one, that doesn’t appear to have any doors or proper windows.

This is the power-pack car, which in these trains has the following properties.

  • The power-pack car is 6.69 metres long.
  • The power-pack car is identical in both the four-car and three-car versions of the Class 755 trains.
  • The four-car trains have four diesel engines.
  • The three-car trains have two diesel engines.

The number of engines possible, leads me to believe there are four slots for engines in the power-pack car.

Transport for Wales have ordered a number of Flirts, which are similar to those in use by Greater Anglia, but they are tri-mode trains, that can run on overhead 25 KVAC electrification, diesel or battery power.

I speculate that they have one diesel engine and three batteries in the four slots.

This is a picture of the Flirt Akku.

I have enlarged the image and it would appear that the trains do not have a central power-pack car, but they do seem to have a lot of electrical gubbins on the roof.

This video shows the Class 755 train being tested at Diss.

It looks to have a much smoother roof line.

Could this indicate that the batteries on the Akku are placed on the roof of the train, as there is certainly a lot of equipment up there?




June 22, 2019 - Posted by | Transport | , , , ,


  1. Fascinating

    Comment by yamey | June 23, 2019 | Reply

    • I actually lost my thread! Stadler are making a big play for the indepenently powered trains. They’ll be clockwork next, as I believe that a Swiss speciality!

      Comment by AnonW | June 23, 2019 | Reply

  2. There are a number of reasons for using a power car: –

    1. Modularity – the same power car can be used with different trains.
    2. Scalability – it can be increased in length, capacity and power fairly easily.
    3. Replaceability – the car can be swapped out for repair or upgrade (though articulated, not loose coupled).
    4. Safety – keeps the flammable lithium away from the passengers.
    5. Noise – as with HST’s, engines are not under passenger cars.

    It is also central to minimise HT wiring to adjacent powered cars.

    Comment by R. Mark Clayton | June 24, 2019 | Reply

    • I seem ti remember thar some of Stadler’s GTWs have two power cars.

      The power bogies are not under the power xar, but at the ends of the train. If you read the Wikipedoa entry for the GTW, it says something about the dynamics, which were not easy!

      Comment by AnonW | June 24, 2019 | Reply

  3. Do you know the length of the other passenger vehicles as Wikipedia entry appears to be incorrect. Based on your info of the powercar length and the passanger vheicle spec provided by TFW i believe the total 3 Car length is 64.49 and the 4 car length is 80.19. Just want to make sure the TFW spec online is correct.

    Comment by Michael Fox | June 25, 2019 | Reply

    • Stadler’s data sheet on their web site, says the length over coupling for a three-car Class 755 train is 65 metres and that of a four-car is 80.7 metres. The power-pack length is given as 6.69 metres. I suspect that the TfW trains are the same as 755s.

      Comment by AnonW | June 25, 2019 | Reply

      • Thanks that was my understanding as well, that’s why you shouldn’t trust Wikipedia lol. According to the TFW data sheets the other passenger vehicles are 15.7 & 21.050

        Comment by Michael Fox | June 26, 2019

      • Stadler are to be commended for putting comprehensive data sheets for a lot of their trains on their web site. The Akku dataset would be very infirmative.

        Comment by AnonW | June 26, 2019

  4. THe FLIRT Accu on the picture indeed has batteries on the roof, this is only a concept unit with very low floors. In the actual order for NAH.SH the units will have higher floors (I believe 76 cm) thus willhave space under the floor for some of the power equipment.

    Comment by Daniel Altmann | June 26, 2019 | Reply

    • Thanks! As you have two nn’s in your surname are you in Europe?

      Comment by AnonW | June 26, 2019 | Reply

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