Safety of Machinery — Safety-Related Parts of Control Systems
ISO 13849 is an international standard for the safety-related parts of control systems used in machinery, including battery management systems (BMS) where they form part of a safety function. It defines performance levels (PL a–e) as a measure of the ability of a safety-related part of a control system to perform a safety function under foreseeable conditions.
Published by: International Organization for Standardization (ISO)
Current edition: ISO 13849-1:2023 (Part 1: Design principles), ISO 13849-2:2012 (Part 2: Validation)
Related standard: IEC 62061 (functional safety of machinery, SILCL approach)
Scope
ISO 13849-1 applies to safety-related parts of control systems for machinery, including electronic control units. In the battery industry it is relevant for BMS designs in industrial battery systems, energy storage installations, and EV charging equipment where the BMS implements safety functions such as overcurrent protection, thermal shutdown, or isolation switching. It provides an alternative safety design methodology to IEC 61508.
Key Concepts
Performance Level (PL)
Performance levels PL a to PL e describe the reliability of a safety function in terms of probability of dangerous failure per hour (PFH). PL e corresponds to the highest reliability (<10⁻⁸/hr), used for functions protecting against the most severe hazards. The required PL (PLr) is determined by risk assessment; the achieved PL must equal or exceed PLr.
Categories and Architecture
ISO 13849-1 defines five architectural categories (B, 1, 2, 3, 4) describing the structure of the safety-related control system — single channel, redundant, with or without monitoring. The combination of category, mean time to dangerous failure (MTTFd), and diagnostic coverage (DC) determines the achievable PL.
Disclaimer: This is not a definitive guide, just an indication and it is important that you always go back to the source for legislation.
References
- ISO 13849-1:2023, ISO