The Anonymous Widower

Class 710 Trains And Regenerative Braking

The new Class 710 trains for the London Overground, will be a next generation train, which could set new standards of energy efficiency. This is from a Bombardier Press release, that the company released when they received the order from London Overground.

The new trains will have similar features to the existing London Overground fleet (also manufactured by Bombardier), including walk-through carriages, air-conditioning and improved accessibility. These next-generation AVENTRA trains will feature an innovative design with optimised performance, including reduced weight, energy consumption, maintenance costs and high reliability, providing substantial benefits to both TfL and its passengers traveling on key London Overground routes, including the newly acquired West Anglia Inner Metro Service.

Note that there is no mention of regenerative braking, but this is mentioned in relation to the other Aventra trains on order; the Class 345 trains for Crossrail.

The Aventra has a slightly unusual and innovative electrical layout.

This article in Global Rail News from 2011, which is entitled Bombardier’s AVENTRA – A new era in train performance, gives some details of the Aventra’s electrical systems. This is said.

AVENTRA can run on both 25kV AC and 750V DC power – the high-efficiency transformers being another area where a heavier component was chosen because, in the long term, it’s cheaper to run. Pairs of cars will run off a common power bus with a converter on one car powering both. The other car can be fitted with power storage devices such as super-capacitors or Lithium-Iron batteries if required.

This was published six years ago, so I suspect Bombardier have improved the concept.

Could it be that the Class 710 trains consists of a two-car power unit sandwiched between two indentical driving cars.

The train could have a formation defined by something like.


The cars are as follows.

  • DMSO – Driving Motor Standard Open
  • PMSO – Pantograph Motor Standard Open
  • DTSO – Driving Trailer Standard Open
  • TSO – Trailer Standard Open

I’ve assumed there are a lot of powered axles as there are with the Class 345 train, but an appropriate number of trailer instead of motor cars can be used according to the demands of the route.

Search the Internet for “Class 710 train regenerative braking” and you find nothing official of with provenance.

I don’t believe that the Class 710 trains are not fitted with regenerative braking, as if you want to save energy on an electric train, it is one of the must-have features in the design.

But you need to be able to handle the electrical energy generated under braking.

Normally, the electricity is fed back into the overhead wires or third rail, so that it can be used by another train nearby. This technique is used extensively on the London Underground and third-rail electrification systems. Although, it is used on some 25 KVAC overhead systems like c2c, it means that the braking energy has to be converted to a high voltage to feed the electricity back.

So on the Aventra are Bombardier taking an alternative approach of using onboard energy storage to handle the energy generated by the braking?


  • Braking energy generated at a station stop, is immediately available to accelerate the train back to line speed.
  • The onboard energy storage is designed to work with the traction motors.
  • It is irrelevant to the drive system, if power comes from 25 KVAC overhead or 750 VDC third-rail.
  • The overhead or third-rail power supply doesn’t need to be able to handle return currents.
  • The train probably has enough onboard power to get to the next station at all times, should the power supply fail.

But the biggest factor is the amount of energy needed to be handled.

In How Big Would Batteries Need To Be On A Train For Regenerative Braking?, I calculated that the energy of a fully-loaded Class 710 train travelling at 100 kph is around 15 KwH.

So when a train stops, this energy will be released.

To get a better handle on how much energy is involved let’s look at these specifications for a Nissan Leaf car.

Nissan talks about 24 and 30 kWH versions of the car, So if this is the battery size, then one of Nissan’s batteries could store all the braking energy of a four-car Class 710 train.

This sounds absolutely unbelievable, but you can’t argue with the Laws of Physics. or the performance of modern automotive battery technology.

There are five lines, where the new Class 710 trains will run.

  • Gospel Oak to Barking
  • Chingford Branch
  • Liverpool Street to Cheshunt
  • Romford to Upminster
  • Watford DC Line

How many of these lines are setup with the capability of accepting the return currents of regenerative braking?

The question is irrelevant if the Class 710 trains handle their own braking energy.


As the energy of a laden Class 710 train going at line speed is around 15 kWh, which is well within the capability of an automotive battery from a quality electric vehicle, I feel very strongly, that the Class 710 trains will handle regenerative braking using onboard energy storage.




January 21, 2017 - Posted by | Transport | , ,


  1. […] I think, it will be likely, that the Class 710 trains will be able to use regenerative braking on the line, as it typically saves around 20% of the energy required to drive a train. I discussed the capabilities of the trains in detail in Class 710 Trains And Regenerative Braking. […]

    Pingback by Up And Down The Gospel Oak To Barking Line « The Anonymous Widower | January 21, 2017 | Reply

  2. If 710 is dual, why the need for all this ho ha on the GOBLIN?

    They are really struggling to get it started at bridge 70 (the beginning of the cut)


    On 21 Jan 2017 7:58 a.m., “The Anonymous Widower” wrote:

    > AnonW posted: “The new Class 710 trains for the London Overground, will be > a next generation train, which could set new standards of energy > efficiency. This is from a Bombardier Press release, that the company > released when they received the order from London Overground” >

    Comment by Russ Hurley | January 30, 2017 | Reply

    • I think the Class 710 trains will be able to jump various bits of line by using the batteries, but the wires will have to be continuous for the freight trains.

      I do think that the extension to Barking Riverside will be built without wires.

      Comment by AnonW | January 30, 2017 | Reply

  3. How come you never answer emails?

    Any idea on height for c710 please.

    Comment by Russell | May 5, 2017 | Reply

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: