Saft launches high-voltage LFP rail batteries

Saft has launched two lithium iron phosphate battery platforms for railway applications, covering high-energy traction systems up to 1,500V and 5.6MWh alongside auxiliary batteries for onboard electrical loads.

The traction platform is intended for battery electric multiple units, hybrid trains, locomotives, and tramways. Its modular architecture allows rolling stock manufacturers to configure voltage, energy, and power around different vehicle requirements, with systems available up to 1,500V and 5.6MWh per battery installation.

The auxiliary platform serves a different electrical function. It can be configured from 24V to 110V for trams, metros, regional trains, and high-speed rolling stock, supplying onboard systems rather than traction motors. Saft says the LFP design can provide up to four times the energy of conventional lead-acid batteries within the same footprint and operate for up to 20 years.

Traction and auxiliary batteries face different duty cycles. A propulsion battery must repeatedly supply and absorb substantial power as a train accelerates, travels beyond continuous electrification, and captures regenerative braking energy. Auxiliary systems support controls, communications, lighting, doors, ventilation, safety equipment, and other loads when the main electrical supply is unavailable or interrupted.

Saft has selected lithium iron phosphate chemistry for both platforms. LFP is widely used where thermal stability and cycle life are priorities and where manufacturers want to avoid nickel and cobalt in the cathode, although cell chemistry alone does not determine railway performance.

Mechanical packaging, cooling, monitoring, protection, isolation, vibration resistance, and fire behaviour all have to be engineered around the rolling stock installation. Equipment mounted beneath or inside a train also has to tolerate repeated mechanical shocks, temperature variation, contamination, and long service intervals while remaining accessible for maintenance.

The traction range addresses growing deployment of battery and hybrid trains on routes where full overhead electrification is unavailable or uneconomic. Recent UK battery train programmes have also incorporated dedicated charging infrastructure, illustrating how onboard storage, route duty cycle, charging power, and fixed electrical equipment have to be designed as one system.

A maximum 5.6MWh battery offers significant energy capacity, but the practical installation on any vehicle will depend on mass, space, axle loading, target range, charging rate, power demand, reserve margin, thermal limits, and expected cycle life. Carrying more stored energy can extend unelectrified operation, but the battery mass must then be accelerated and braked throughout every journey.

The 1,500V upper limit also affects the surrounding electrical equipment. Raising DC voltage reduces current for a given power transfer, which can reduce conductor size and resistive losses, but insulation, connectors, contactors, switching, isolation monitoring, and protection must all be designed for the higher voltage.

Traction converters then have to coordinate battery power with the motors and regenerative braking system. Energy recovered during braking can be returned to the battery within its charge limits, while acceleration places high discharge demands on cells, cooling systems, busbars, and power electronics.

The auxiliary platform’s 24V to 110V range reflects the variety of established low-voltage systems used across rolling stock fleets. A scalable platform can allow manufacturers to retain common battery technology across several vehicle classes while configuring modules and controls for the voltage used by each train.

Saft says the auxiliary design can deliver up to four times the energy of lead-acid within the same footprint. Operators could use that additional capacity to extend backup duration or reduce the physical space allocated to batteries, depending on the vehicle architecture and required emergency operating time.

Both platforms use Saft’s SIL2 battery management system. The BMS monitors cell and module condition, estimates state of charge, applies operating limits, identifies abnormal behaviour, and communicates with the wider train control system. Functional safety becomes particularly important when a battery fault or incorrect state estimate could affect traction availability or essential onboard services.

The platforms are designed around railway and industrial battery standards including IEC 62928 for traction applications, IEC 62973-5 for auxiliary batteries, and IEC 62619 and IEC 62620 for lithium-ion safety and performance. Vehicle integration will still require programme specific qualification because mounting, cooling, electrical interfaces, and operating profiles differ between train platforms.

Manufacturing will take place at Saft’s Raškovice facility in the Czech Republic. Rail equipment may remain in service for decades, making manufacturing continuity, replacement modules, configuration control, technical documentation, and long term support central to the supply agreement rather than secondary considerations after initial delivery.

Saft already supplies nickel based and lithium titanate batteries into rail applications. The new LFP range broadens the available chemistry options rather than replacing those technologies across every duty cycle. Required power, charging speed, operating temperature, mass, expected cycles, maintenance, and total ownership cost can favour different battery systems.

Commercial deployment will now depend on rolling stock selections and qualification programmes. The new platforms provide a technical envelope extending to 1,500V and 5.6MWh for traction and 110V for auxiliary duties; named train programmes will establish where operators and manufacturers judge LFP to offer the strongest balance of capacity, service life, safety, and cost.