Battery systems for rail
Battery systems in railway applications store electrical energy onboard and provide traction power, auxiliary power, or both — enabling operation on the non-electrified sections that make up roughly 44% of Europe’s rail network, or supplementing catenary supply.
Battery use in rail divides into three categories. Auxiliary batteries supply low-voltage systems — lighting, heating, ventilation and air conditioning (HVAC) controls, door operation, passenger information, emergency functions — and are present on virtually all rolling stock regardless of primary traction type.
Traction buffer batteries on electric multiple units absorb regenerative braking energy and smooth peak demand on the DC link. Battery-electric multiple units (BEMUs) carry large traction battery packs sized to provide propulsion for 40–100 km or more on non-electrified track, charged from the overhead contact system wherever it is present.
BEMUs typically charge at terminus stations equipped with short overhead contact sections, from the electrified main line during approach runs, or from dedicated depot chargers. The Holstebro–Skjern line in Denmark, operated by Midtjyske Jernbaner using Siemens Mireo Plus B units officially inaugurated on 19 December 2025, covers 67 km of non-electrified track between charging points.
Battery chemistry
Three lithium-ion chemistries dominate current rail deployments. Lithium nickel manganese cobalt oxide (NMC) offers high energy density and is widely used in regional BEMU applications where range per charge matters. Lithium iron phosphate (LFP) provides lower energy density but superior thermal stability and longer cycle life, making it common in tram and metro buffer applications.
Lithium titanate oxide (LTO) delivers very fast charge and discharge capability and exceptional cycle life but at lower energy density — it is used in applications requiring rapid power exchange, including the buffer batteries on Siemens Mireo Plus H hydrogen trains.
All three chemistries impose thermal management requirements, and packs on railway vehicles must operate across the environmental ranges specified in EN 50155. EU Battery Regulation 2023/1542 has applied CE-marking and general due-diligence obligations to traction batteries since 2024; mandatory minimum recycled-content thresholds for cobalt, lead, lithium, and nickel follow from August 2031, alongside a digital battery passport requirement.
European deployment
The market for railway traction batteries was estimated at USD 662.1 million in 2025, growing from USD 621.1 million in 2024, with lithium-ion chemistries accounting for around 35% of revenue and lead-acid batteries — still dominant in auxiliary and legacy applications — accounting for over half (Global Market Insights, 2025).
Operators across Austria, Denmark, Germany, France, and Italy have placed orders for BEMU platforms from manufacturers including Stadler, Alstom, Siemens, CAF, and Hitachi. BEMUs are the primary diesel replacement technology for non-electrified routes where charging infrastructure is available; hydrogen covers longer gaps beyond battery range.