{ "node": { "id": "term:diagnostic-coverage", "type": "Term", "label": "Diagnostic coverage", "properties": { "id": "diagnostic-coverage", "name": "Diagnostic coverage", "section": "topic-hvsafety", "definition": "The fraction of a component’s failure rate that a safety mechanism detects or controls. ISO 26262 treats coverage from about 60% as low, from 90% as medium and from 99% as high; comparing two independent measurements of the same cell voltage typically earns high coverage, while a simple plausibility check earns much less.", "formula": "coverage = λ_detected / λ_total", "related": [ "hardware-safety-metrics", "functional-safety", "redundant-bms", "fmea", "dtc" ], "example": { "title": "Calculate a simplified coverage fraction", "text": "If relevant dangerous failure rates total 100 units and 90 of those units are detected by the stated diagnostics, this simplified coverage is 90%. Counting failure modes without weighting their rates gives a different quantity." }, "url": "https://lemonergy.com/learn/glossary/diagnostic-coverage/", "mentions": [ "cell-voltage" ] } }, "edges": [ { "id": "edge:5157", "source": "term:diagnostic-coverage", "target": "topic:topic-hvsafety", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:5158", "source": "term:diagnostic-coverage", "target": "term:hardware-safety-metrics", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:5159", "source": "term:diagnostic-coverage", "target": "term:functional-safety", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:5160", "source": "term:diagnostic-coverage", "target": "term:redundant-bms", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:5161", "source": "term:diagnostic-coverage", "target": "term:fmea", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:5162", "source": "term:diagnostic-coverage", "target": "term:dtc", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/diagnostic-coverage/cell-voltage", "source": "term:diagnostic-coverage", "target": "term:cell-voltage", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:5164", "source": "term:diagnostic-coverage", "target": "visual:coverage", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } }, { "id": "edge:5165", "source": "term:diagnostic-coverage", "target": "reference:iso-functional", "type": "cites", "properties": { "sourceFile": "wiki-references.json", "scope": "direct technical reference" } } ], "neighbors": [ { "id": "topic:topic-hvsafety", "type": "Topic", "label": "High-voltage and functional safety", "properties": { "id": "topic-hvsafety", "name": "High-voltage and functional safety", "lede": "Keeping people safe from the pack’s voltage and keeping its electronics safe when they fail: insulation, switching, fusing and the functional-safety process.", "context": "Relate protection to faults, detection and response.", "example": "Normal-operation current limits do not demonstrate correct contactor behavior under a welded-contact or sensor fault.", "lesson_url": "https://lemonergy.com/learn/fundamentals/battery-basics/", "lesson_label": "Open battery basics" } }, { "id": "term:hardware-safety-metrics", "type": "Term", "label": "Hardware safety metrics", "properties": { "id": "hardware-safety-metrics", "name": "Hardware safety metrics", "abbr": "SPFM, LFM, PMHF", "aka": [ "single-point fault metric", "latent fault metric", "probabilistic metric for random hardware failures", "hardware architectural metrics" ], "section": "topic-hvsafety", "definition": "The ISO 26262 numbers showing that random hardware failures are under control. The single-point and latent fault metrics are the shares of failures that safety mechanisms cover — at least 99% and 90% for ASIL D — and PMHF is the residual rate of violating a safety goal, below 10⁻⁸ per hour (10 FIT) for ASIL D.", "related": [ "functional-safety", "diagnostic-coverage", "safety-concept", "fmea", "redundant-bms" ], "url": "https://lemonergy.com/learn/glossary/hardware-safety-metrics/", "mentions": [] } }, { "id": "term:functional-safety", "type": "Term", "label": "Functional safety", "properties": { "id": "functional-safety", "name": "Functional safety", "abbr": "ISO 26262", "aka": [ "ASIL" ], "section": "topic-hvsafety", "definition": "The discipline, standardised for vehicles in ISO 26262, of making sure electronic failures do not cause harm. Battery functions such as overvoltage protection are classified by risk into ASIL levels A to D, which set how redundant and verified their hardware and software must be.", "related": [ "bms", "high-voltage-interlock", "insulation-resistance", "fmea", "mcu", "iso-13849" ], "url": "https://lemonergy.com/learn/glossary/functional-safety/", "mentions": [] } }, { "id": "term:redundant-bms", "type": "Term", "label": "Redundant BMS architecture", "properties": { "id": "redundant-bms", "name": "Redundant BMS architecture", "aka": [ "redundant BMS", "secondary safety monitor" ], "section": "topic-pack", "definition": "A BMS design that duplicates safety-critical functions so no single failure can hide a hazard: an independent second voltage monitor beside the main measurement chip, two current sensors of different principle, a watchdog or second processor, and two separate paths to open the contactors. It is how BMS hardware reaches ASIL C or D.", "related": [ "functional-safety", "bms-architecture", "hardware-safety-metrics", "lockstep-core", "current-sensor", "diagnostic-coverage" ], "url": "https://lemonergy.com/learn/glossary/redundant-bms/", "mentions": [ "bms" ] } }, { "id": "term:fmea", "type": "Term", "label": "Failure mode and effects analysis", "properties": { "id": "fmea", "name": "Failure mode and effects analysis", "abbr": "FMEA", "section": "topic-hvsafety", "definition": "A structured review that lists every way a component or process could fail, its effect, and how likely it is to happen and be detected, scoring each to prioritise fixes. Battery programmes run it on the cell, the pack design and the production process.", "related": [ "functional-safety", "abuse-testing", "cell-design", "fault-tree-analysis" ], "url": "https://lemonergy.com/learn/glossary/fmea/", "mentions": [] } }, { "id": "term:dtc", "type": "Term", "label": "Diagnostic trouble code", "properties": { "id": "dtc", "name": "Diagnostic trouble code", "abbr": "DTC", "aka": [ "fault code" ], "section": "topic-data", "definition": "A coded fault a controller stores when a check fails — a cell overvoltage, a sensor out of range, an isolation fault — with a status and often a snapshot of conditions when it occurred. Reading and interpreting DTCs is the first step of any battery root-cause analysis.", "related": [ "uds", "bmu", "insulation-resistance", "freeze-frame" ], "url": "https://lemonergy.com/learn/glossary/dtc/", "mentions": [ "insulation-fault" ] } }, { "id": "term:cell-voltage", "type": "Term", "label": "Cell voltage", "properties": { "id": "cell-voltage", "name": "Cell voltage", "aka": [ "electromotive force", "EMF" ], "section": "topic-electrochemistry", "definition": "The difference between the positive and negative electrode potentials at equilibrium: for NMC against graphite about 3.7 V. It is set by the chemistry, and the difference in Gibbs free energy of the cell reaction per unit charge.", "formula": "E = E₊ − E₋ = −ΔG / nF", "unit": "V", "related": [ "electrode-potential", "gibbs-free-energy", "open-circuit-voltage", "nominal-voltage" ], "example": { "title": "Subtract equilibrium electrode potentials", "text": "If two illustrative electrode potentials are 4.0 V and 0.2 V versus the same reference, their equilibrium cell voltage is 3.8 V. Under load, resistance and polarization change the measured terminal voltage." }, "url": "https://lemonergy.com/learn/glossary/cell-voltage/", "mentions": [ "electrode", "negative-electrode", "graphite" ] } }, { "id": "visual:coverage", "type": "Visual", "label": "Detected failures are part of the total rate", "properties": { "title": "Detected failures are part of the total rate", "summary": "Coverage is a rate-weighted fraction, not a count of checks.", "readout": "Detecting 90 FIT out of 100 FIT gives 90% coverage. 1 FIT = 1 failure per billion operating hours.", "formula": "Diagnostic coverage = λ_detected / λ_total", "note": "Detected and total rates must describe the same population, failure modes and operating basis. Independent assessment is needed to justify either rate.", "software": { "status": "reference", "label": "Reference concept", "body": "This reference ratio is not a functional-safety assessment. No diagnostic coverage or integrity level is certified by this chart.", "href": "../chapter-1/" }, "html": "
Rate-weighted coverage
Rate-weighted coverageDetected failure rate (FIT) versus Coverage (%). Coverage. Interpretation follows the graphs.00252550507575100100Detected failure rate (FIT)Coverage (%)
Coverage
" } }, { "id": "reference:iso-functional", "type": "Reference", "label": "ISO 26262-1:2018 — Road vehicles — Functional safety — Part 1: Vocabulary", "properties": { "title": "ISO 26262-1:2018 — Road vehicles — Functional safety — Part 1: Vocabulary", "publisher": "International Organization for Standardization", "url": "https://www.iso.org/standard/68383.html", "type": "Standard catalogue", "scope": "Scope and terminology of automotive electrical/electronic functional safety. The catalogue is not the full standard.", "year": 2018, "accessed": "2026-10-27" } } ] }