ISO 26262 — Functional Safety for Road Vehicles¶

Safety Is a Design Requirement¶

ISO 26262 is the functional safety standard for road vehicles. It forces safety to be engineered, verified, and proven — not assumed. For a BMS, this shapes how faults are detected, mitigated, and documented.

The ISO 26262 Framework¶

Safety lifecycle from concept to decommissioning.
Hazard Analysis and Risk Assessment (HARA).
ASIL levels (A–D) define required rigor.

Safety Goals → Requirements¶

BMS safety goals typically include:

Prevent cell overvoltage
Prevent cell undervoltage
Prevent unsafe overcurrent
Ensure safe shutdown when insulation fails

These become functional safety requirements that must be traced into design and tests.

Common Safety Mechanisms in a BMS¶

Redundant sensing (cell voltage, current)
Hardware OV/UV comparators
Watchdogs and safe‑state logic
Contactor diagnostics and HVIL
Fault logging with freeze‑frame data

Verification and Validation¶

ISO 26262 expects structured evidence:

Unit, integration, and system tests
SIL/HIL testing
Fault injection to measure diagnostic coverage
Traceability from requirement to test case

Documentation Burden (Why It Feels Heavy)¶

Safety plan
Safety case
FMEA / FTA
Test evidence and traceability matrix

If you cannot prove it, it didn’t happen.

Takeaways¶

ISO 26262 is a process standard as much as a technical one.
It drives redundancy, diagnostics, and test rigor in BMS design.
Compliance is expensive to add late — it must be designed in early.

Literature Review¶

Core References¶

ISO 26262‑1:2018 (framework)
ISO 26262‑6:2018 (software)

IEC 61508 (generic functional safety)