Bringing Diagnostic Clarity to Lithium-Ion Batteries in Rail

Rail is in the midst of a big energy storage shift: away from lead-acid batteries and toward lithium-ion. The reasons are persuasive: lithium-ion offers higher energy density, longer life, and lower maintenance. But switching is more than dropping in new batteries. It demands visibility, safety, and diagnostics under the harsh and varied conditions rail operations require.

Key Challenges

Safety concerns: lithium-ion batteries have risks of overheating, thermal runaway, and fires. These are amplified in rail due to extremes of temperature, vibration, and moisture.
Performance under variation: in rail operations, batteries must cope with wide temperature ranges, unpredictable loads, and start/stop duty cycles.
Legacy expectations: many maintenance crews and diagnostic tools are tuned to lead-acid systems. Predictive diagnostics are less common, and battery replacement is often reactive rather than proactive.

Solution Approach

The proposed solution involves embedding smart sensors and data loggers directly into each battery unit. Metrics such as voltage, current, temperature, charge cycle count, and long-term degradation are captured continuously. Data is transmitted over CAN-FD interfaces, enabling real-time streaming, cloud analytics, and even over-the-air firmware updates.

AI and machine learning tools can then analyze this data, detecting early warning signs and degradation trends before they turn into costly failures. Dashboards are integrated into existing maintenance workflows, minimizing disruption while maximizing insight.

Results

Pilot installations showed significant benefits:

Reduction in diagnostic time for battery faults
Fuel savings through optimized charge management
Extended battery life enabled by predictive maintenance
Zero critical failures during testing at extreme temperatures from –40 °C to +50 °C

By scaling these pilots across more fleets, operators can enhance safety, reduce costs, and accelerate lithium-ion adoption with confidence.

Why It Matters

Diagnostic visibility transforms battery management in three ways:

Reduces risk by detecting issues early.
Shifts maintenance from reactive to proactive.
Supports compliance with regulatory and safety standards through robust data logging.

SAE J1939 in Rail Applications

Alongside battery diagnostics, communication protocols play a vital role. SAE J1939, originally developed for trucks and heavy equipment, is increasingly relevant to rail applications.

What J1939 Provides

J1939 is a higher-layer protocol built on CAN bus technology. It organizes data into Parameter Group Numbers (PGNs) and Suspect Parameter Numbers (SPNs), which standardize signals such as engine speed, temperatures, or fault codes. It supports broadcast messaging, diagnostics, and network management across electronic control units (ECUs).

Applications in Rail

Subsystem communication: locomotives include engines, generators, auxiliary power units, braking systems, and now large battery packs. J1939 enables these subsystems to share standardized data.
Diagnostics and telematics: J1939’s built-in support for diagnostic trouble codes makes it valuable for fleet monitoring and predictive maintenance.
Battery integration: battery metrics such as state of charge, temperature, and health can be mapped into J1939 messages, allowing integration with propulsion and auxiliary systems.

Challenges and Adaptations

Bandwidth: traditional J1939 operates at 250 or 500 kbit/s, which may be insufficient for high-volume battery data. CAN-FD extensions offer a way forward.
Standardization gaps: while J1939 defines many engine and vehicle parameters, it lacks detailed standards for advanced battery diagnostics. Proprietary extensions or gateways may be needed.
Environmental and safety requirements: rail imposes stricter standards for vibration, electromagnetic interference, and fail-safe communication. J1939 must be adapted to meet these needs.

Future Outlook

Hybrid architectures are emerging: high-bandwidth networks handle raw battery data, while gateways translate key diagnostics into J1939 for fleet-wide integration. As rail fleets adopt lithium-ion batteries more broadly, pressure will grow to standardize battery-specific PGNs and SPNs within the J1939 framework.

Conclusion

The shift to lithium-ion in rail is not only about new chemistry but also about new intelligence. Embedding diagnostic solutions transforms batteries from black boxes into transparent, manageable systems. At the same time, protocols like J1939 provide the backbone for integrating these diagnostics into the broader rail ecosystem. Together, they pave the way for safer, more efficient, and future-ready rail operations.

References

SAE J1939 Starter Kit and Network Simulator

Our JCOM.J1939 Starter Kit and Network Simulator is designed to allow the experienced engineer and the beginner to experiment with SAE J1939 data communication without the need to connect to a real-world J1939 network, i.e., a diesel engine. It may sound obvious, but you need at least two nodes to establish a network. That fact applies especially to CAN/J1939, where the CAN controller shuts down after transmitting data without receiving a response. Therefore, our jCOM.J1939 Starter Kit and Network Simulator consists of two J1939 nodes, namely our jCOM.J1939.USB, an SAE J1939 ECU Simulator Board with USB Port.

The jCOM.J1939.USB gateway board is a high-performance, low-latency vehicle network adapter for SAE J1939 applications. The board supports the full SAE J1939 protocol according to J1939/81 Network Management (Address Claiming) and J1939/21 Transport Protocol (TP).

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