Small Branch Line, Big Lessons in Battery Fire Safety
- 2 hours ago
- 3 min read
Great Western Rail in the UK are successfully running one of the world's first electric trains. Some of our team got to hop aboard and learn more about battery fire considerations for the Greenford line from the brains behind the project.
For most passengers, the Greenford branch line is simply a short shuttle linking Greenford with West Ealing in west London. The journey takes little more than ten minutes and serves four intermediate stations.
For railway engineers, however, this modest branch line has become one of the most important testbeds in Britain.
Great Western Railway's battery-electric train is demonstrating whether fast-charging battery technology can provide a practical alternative to diesel operation on lightly used routes. Rather than carrying huge batteries and charging overnight, the train receives rapid top-up charges every time it returns to West Ealing, allowing it to operate throughout the day without overhead wires.
The project is not just about proving battery traction. It is also exploring how large lithium-ion batteries can be deployed safely in a passenger railway environment.
Battery capacity and charging
One of the most interesting details to emerge from GWR's technical reporting is the size of the onboard battery system.
The train carries three Lithium-Titanate Oxide (LTO) 84kWh battery packs beneath each powered driving car. With two powered driving cars in the three-car formation, the total onboard energy storage exceeds 500kWh. GWR states that the batteries are capable of accepting charging power of up to 1MW through the fast-charge system installed at West Ealing.
To put that into perspective, the train carries roughly six to eight times the battery capacity of a typical modern electric car.
The batteries are replenished at West Ealing using retractable charging shoes mounted beneath the train. When the train stops in the correct position, the shoes connect with charging rails installed between the running rails. The system can restore significant energy during the scheduled turnaround, allowing the train to complete repeated trips throughout the day.
According to GWR's Julian Fletcher, each minute of charging can add approximately seven kilometres of range. Regenerative braking also returns energy to the batteries whenever the train slows down, helping maintain charge levels throughout the day.
The batteries are designed for frequent high-power charging and discharging, something that is essential on a route where the train receives multiple rapid charges every day.
Designing fire safety
Whenever large lithium-ion batteries are discussed, questions about fire risk inevitably follow.
GWR's Greenford project provides an interesting example of how railway engineers have approached this challenge through multiple layers of protection rather than relying on a single safeguard:
Physical separation. The battery packs are mounted underneath the train in dedicated equipment areas rather than inside passenger spaces. This creates distance between passengers and the energy storage system while simplifying inspection and maintenance.
Battery management. Throughout the trial, engineers continuously monitored battery condition, state of charge and charging performance both on board and remotely. Detailed data is collected from every journey to understand how the batteries behave under different operating conditions, including winter heating loads and abnormal operating scenarios.
Charging safety. The charging rails at West Ealing are not permanently energised. Instead, power is only supplied when the train is correctly positioned and connected. The Fast Charge Battery Bank incorporates electrical interlocks and protection systems that monitor for faults such as earth leakage. If the train is not present, the rails remain unpowered.
Protection of the trackside battery installation itself. The large battery banks beside the railway are housed inside containerised enclosures equipped with air-conditioning systems to control temperature. GWR's published technical material also states that the battery containers incorporate dedicated fire-suppression systems for emergency situations.
This approach reflects a broader industry trend. Modern battery systems are increasingly designed around prevention, monitoring, containment and suppression rather than assuming batteries will never fail.
Electrification safety in all sectors
The Greenford trial challenges the traditional assumption that railways must choose between diesel trains and expensive full-route electrification.
Instead, GWR has demonstrated a third option: a relatively modest onboard battery, frequent rapid charging, and strategically placed energy storage at key locations.
The infrastructure supporting the train is surprisingly compact. The trackside battery banks are housed in shipping-container-sized units and draw power gradually from the local electricity supply before delivering rapid bursts of energy to the train when required.
What makes the project particularly significant is that it combines operational practicality with a strong focus on safety. Every aspect of the system — from controlled charging rails and battery monitoring to fire-suppressed battery containers — has been designed to manage the unique risks associated with large-scale lithium-ion energy storage.
A massive thanks to Julian and the GWR team for hosting us aboard the Greenford electric train and sharing their battery fire safety insights with us.
