Reflections on the GWR Fast Charge Trial

Article By Dave Horton, Chief Mechanical Engineer, GWR Fast Charge Battery Train Trial

If, at the start of my career, you’d told me that nearly 20 years on I’d be spending a fair amount of my time shuttling backwards and forwards on GWR’s Greenford branch line in West London on a pioneering battery-powered ex-Underground train, I probably wouldn’t have believed you. But this has been my life for the last couple of years. The train, a Class 230 (therein lies a tale in itself), has been part of a 12-month trial to test an automatic, Ground Based Fast Charging (GBFC) system for battery trains, which I’ve had the privilege of helping to design, build, install, homologate (approve) and test.

The reason for GBFC is simple; we have diesel trains and we have electric trains. The former are useful because they are ‘self-powered’ and require very little infrastructure other than the track they run on, plus re-fuelling facilities at a depot. The latter are useful because they are relatively simple and therefore cheap to build and maintain. They also deliver high performance in terms of power and acceleration, and zero emissions at the point of use. So conventional electric trains are great, but the downside is that they require electrification to power them, and electrification infrastructure comes at a very high price. Diesel trains have done an excellent job, for decades, of operating those lines where electrification cannot be financially justified. But these days, building new diesel trains is becoming less and less politically and morally acceptable on account of the fact that they will ‘lock in’ harmful CO2, NOx, particulate and other undesirable emissions for 30 years or more, which tends to be the assumed asset life of a train. Unfortunately our existing diesel train fleet is gradually succumbing to the march of time just like all of us, so what to do?

Into this breach between no more diesel trains and unaffordable electrification steps the ‘compromise’ of battery electric trains, but it isn’t a bad compromise at all, and it’s getting better. The idea of a battery-powered rail vehicle is absolutely nothing new; examples of battery locomotives go right back to the late 19th century. What is new is the rapid advance of battery and charging technology, spurred on largely by the spread of Electric Vehicles (EVs) on our roads, and the wider push towards electrification.

The primary purpose of the GBFC system which myself and just 10 of my fellow Engineers have worked to develop and demonstrate to hundreds of people from both inside and outside the rail industry since 2024 is to overcome one simple operational problem; that battery trains don’t quite have the range (yet!) to complete a whole day’s service. Therefore they need to be charged en route. The remit of the charging system was to deliver this safely, automatically, reliably, with the minimum of infrastructure, and within the boundaries of the existing timetable.

Suffice to say there isn’t space in this short article to go into all the technical details but GBFC has achieved everything it set out to achieve. We have tested it through all seasons, varied many variables e.g. passenger load and driving styles, and with all conceivable failure modes, both simulated and sometimes real. We have measured energy consumption and State of Charge (SoC) trend in all these scenarios and have used it to validate our mathematical models. We have developed operator procedures and worked with drivers to help them get comfortable with the new technology. The system offers tantalising possibilities for the future as well, including as a means to do ‘energy arbitration’ and make greater use of renewables, which could have a real financial benefit to the railway as well as offering greater resilience to energy price shocks and the effects of climate change.

The presence of a ‘real life trial’ on the UK National Network has worked wonders to give confidence to the rail industry that battery trains are a practical proposition. The main benefits of battery trains to the rail network will be a reduction in whole life operating costs and CO2 emissions, and a reduction in local air pollution and noise. There is very little not to like!