Battery-powered trains may soon be coming to the UK, as the country’s aging diesel fleet nears retirement. Manufacturers are exploring eco-friendly replacements, including battery-powered options that could eliminate the need for overhead electrified wires on unelectrified tracks, saving installation costs.
At Hitachi’s Newton Aycliffe factory, engineers recently completed testing on a “tri-mode” train that replaces one diesel generator with lithium batteries, enabling up to 50% fuel savings on unelectrified lines. Based on this test, Hitachi also aims to develop a fully battery-powered model capable of covering up to 90 km (56 miles) on non-electrified tracks, with a goal of eventually phasing out diesel entirely.
Siemens is also working on its own battery-powered trains in Goole, East Yorkshire, anticipating orders from operators like ScotRail, Great Western Railway (GWR), and Transport for Wales. Solely battery-powered trains are already in use in Japan and Germany, though UK experts note that fire safety could be a unique challenge for lithium battery trains. Hitachi has run extensive safety tests to ensure passenger safety in emergencies.
Currently, diesel-electric trains operate on electrified tracks and use diesel engines on non-electrified sections. Hitachi’s new tri-mode design replaces a diesel unit with 16 EV-like batteries, capable of recharging on electrified lines or in 10–15 minutes while stationary. The tri-mode model is designed to switch power sources automatically, prioritizing battery use in urban areas to reduce emissions. Existing diesel-electric trains could also be retrofitted with batteries, making the transition more affordable.
Battery-only trains in the UK face some limitations. Hitachi’s test model could travel 70 km (44 miles) on battery power, which would support routes with intermittent electrification, such as London to Oxford. However, steeper, more energy-demanding routes like TransPennine’s would reduce battery range.
Experts say that EV batteries, when properly managed, pose lower fire risks than diesel or petrol engines, though there are challenges. Lithium batteries can enter “thermal runaway,” a situation where heat rapidly escalates, potentially causing a fire. Hitachi’s testing simulated worst-case scenarios, using shields and cooling units to prevent spread and monitoring software to manage temperatures. In emergencies, affected carriages could still be moved, even if a battery was burning.
Moving toward fully battery-powered trains aligns with the UK government’s net-zero emissions goal for 2050. As battery technology advances, the industry expects lighter, more powerful cells, making hybrid trains a feasible step toward a future of completely battery-driven railways.
