Battery Design covers automotive, grid-scale storage and aerospace battery systems. Each of those industries draws its own line on acceptable risk using a different standard. Automotive BMS design lives under ISO 26262 (ASIL A–D); grid and stationary Battery Energy Storage Systems (BESS) more often reference IEC 61508 or IEC 62619 alongside standards like NFPA 855 and UL 1973 (SIL 1–3); off-highway and industrial machinery use ISO 13849 (Performance Level a–e) or IEC 62061; and aerospace or eVTOL systems answer to DO-178C, DO-254, and ARP4754A (Design Assurance Level A–E).
This page lines these frameworks up against each other by terminology, lifecycle stage, and stringency, and tackles a question that comes up often in practice: whether a BMS module already qualified to automotive ASIL D can be dropped directly into a commercial BESS or marine pack, or whether the differences between the standards mean it has to be re-qualified from scratch.
The comparison matrix below lines the four frameworks up side by side:
| Sector | Standard(s) | Integrity Levels | How the level is derived |
|---|---|---|---|
| Automotive | ISO 26262 | ASIL A–D | Severity × Exposure × Controllability, assessed per vehicle-level hazard |
| Grid & Stationary BESS | IEC 61508 / IEC 62619 / NFPA 855 / UL 1973 | SIL 1–3 | Probability of dangerous failure per hour (PFH), risk-reduction factor |
| Off-Highway / Machinery | ISO 13849 / IEC 62061 | PL a–e | Category, MTTFd and diagnostic coverage of the safety function |
| Aerospace / eVTOL | DO-178C / DO-254 / ARP4754A | DAL A–E | Failure Condition severity classification at aircraft level |
So, Can an ASIL D Module Go Straight Into a BESS?
The short answer is no, not without extra work, and the reason is structural rather than a matter of paperwork. ISO 26262 does not define a normative mapping from ASIL to the IEC 61508 SIL scale, so a module certified to ASIL D cannot simply relabel itself SIL-anything, and the reverse is equally true [1]. The rule-of-thumb equivalence quoted informally in the industry, that ASIL D sits close to SIL 3 rather than the nominally higher SIL 4, comes from a rough comparison of how many people are plausibly at risk in a road accident versus a process-industry failure — not from any agreed conversion table [1].
The two frameworks also derive their level from different inputs, which is the deeper reason a straight port doesn’t work. ASIL comes from Severity × Exposure × Controllability, assessed against a specific vehicle-level hazard scenario. Controllability in particular assumes a driver who can brake, steer or otherwise intervene — a factor that has no real equivalent for a stationary BESS container with no operator standing next to it, or only a loose one for a marine pack where the crew’s ability to intervene is very different from a driver’s. IEC 61508’s SIL, by contrast, is derived from a target probability of dangerous failure per hour (PFH) and a required risk-reduction factor, calculated independently of who might be nearby to react. A module engineered against one set of assumptions doesn’t automatically satisfy the other framework’s hazard analysis, even where the numeric levels look superficially similar.
In practice this means an ASIL D-qualified BMS module moving into a BESS or marine application has to be re-assessed against that sector’s own hazard analysis (a fresh HARA-equivalent under IEC 61508, or the relevant clauses of IEC 62619 / NFPA 855 / UL 1973 for stationary storage), not just relabelled. The underlying hardware architectural metrics — SPFM, LFM and PMHF, covered on this site’s BMS Hardware Architectural Metrics page — are usually the most reusable part of the safety case, since a well-designed diagnostic and redundancy architecture tends to satisfy more than one standard’s hardware requirements. The systematic safety case — the HARA, the safety goals and the software FFI argument built around ASIL-specific assumptions — is the part that typically has to be redone for the new sector, which is exactly why the recommendation in the standards-mapping literature is to treat reuse as requiring additional evidence rather than automatic equivalence [1].
References
- Mapping to IEC 61508 the hardware safety integrity of elements developed to ISO 26262, Journal of Loss Prevention / Taylor & Francis
See also: IEC 61508, IEC 62619, ISO 13849, Global Standards Certifications for BESS