Great Western Railway have been testing their "Battery Electric Train" on the line from West Ealing to Greenford for a while now, and they invited a group of stakeholder along to see it, hear about it, and have a ride yesterday.   

The test train runs from West Ealing in a side platform away from the main line - and that was where I found it; it's a 3 carriage conversions of an old district line underground (similar conversions on the Isle of Wight and from Wrexham to Birkenhead). Smart it looks too.

The challenges with a battery train include the distance it can travel on a charge, and the time it takes to recharge.  This train has proven capable of running over 100 miles on a single charge, but is normally used over a much shorter distance.  "Fast Charging" at West Ealing means than in its three minutes turn around, it can take in enough charge for the next round trip of around 25 minutes, with three intermediate stops each way, to Greenford.

That charging rate is more than the local grid could cope with, so there are containers of batteries beside the track which are charged much more gradually when the train is not there, ready to "thump" power into the train when it's turning around there.  I understand that less that 10% of the battery charge is used on each trip, and with recharging at 65% of the maximum possible that 10% is replenished in the three minutes. Screens and graphics on the test train were showing that it had been working with batteries charged to between 75% and 85% all day.

The journey itself - uneventful (as a train journey should be). We stopped at each intermediate station - Drayton Green, Castle Bar Park and South Greenford, passing the normal passenger service going the other way, before pulling into the single platform for the GWR^▸ (Great Western Railway) Greenford Branch at Greenford. And back that same way, meeting up with many long term friends and a really useful day.  I hung around at West Ealing to get few photos of that charging ramp.

---

Apart from the long distance (IET^▸ (Intercity Express Train)) trains, all the trains that GWR run in the West of England are old. Classes 150, 158, 165 and 166 are all expected to be life expired by 2035 and it would be "madness" to replace them with a further generation of diesel trains. So what is to be done to replace them?

Lines get longer and the national grid less able to provide even the trickle charging for storage batteries as you get further west. Major engineering would be required for continuous overhead electrification. Third rail / fourth rail as used in the South East of England and London Underground is considered unsafe for use on newly electrified line.   Hydrogen is ruled out as a fuel.  So where does that leave us?

A very few lines may be pure battery trains using the technology developed "at Greenford".  Beyond that, we are looking largely at discontinuous electrification where overhead equipment is put in on the easier (to install) parts of the route with batteries in use to cover the gaps. On the electric sections, battery charging can take place at train runs through.

As I recall, the HSTs^▸ (High Speed Train) were introduced as a quick stop-gap when it became obvious that the planned electrification wouldn't be done before the previous kit had to be replaced. So they were introduced, and electrification was forgotten about. The IETs^▸ (Intercity Express Train) intended to replace them years after they were supposed to have been retired were originally supposed to have been all electric between Bristol, South Wales and Oxford, but were fitted with diesel engines as a quick stop-gap when it became obvious that the planned electrification wouldn't be completed. My guess at what will happen to intercity services next will be some other hasty stop-gap once they get too close to reaching 40 of their planned 25 years in service.

But it isn't just intercity services. Someone, somewhere is going to have to make big decisions very soon about what happens to commuter trains too. The choice seems to be between implementing plans already made to electrify much more railway and buy new electric stock, or do practically nothing and enter a new period of managed decline in railways. Battery trains will do an excellent job filling in on track that isn't worth electrifying fully, as the trial at Greenford seems to be showing. But there aren't any more around, nor any more fast charging points, so they will need either their own infrastructure or at least some 25 kV OHLE to power and charge along the routes.

Broadgage is right, we can't go on with diesel forever. It's already an anachronism, given that there is no engineering reason why the whole rail network cannot be run on electricity alone.

Someone asked elsewhere how 10 tonnes of batteries compare with an equivalent diesel train. If I've missed something blindingly obvious - which is very possible - please let me know!

I think a Class 166 is broadly comparable to the Class 230 test train. A Class 166 has a Perkins 2006 TW-H engine under each car, with a dry weight of 1118kg. Each of these is coupled to a Voith T211 hydraulic transmission weighing 760kg. Ignoring fuel and fuel tanks, that gives a total weight of 5634kg - just over half the weight of the batteries on the test train. But then there's the traction motors...

I'm struggling to get data on how much the class 230's traction motors and gearboxes weigh - I'm guessing it could be quite a large fraction of the equivalent diesel/hydraulic setup?

Just to complicate the comparison further, on the day we visited half the batteries were out of use - so potentially the weight of a BEMU could be reduced significantly.