ISO 26262-4: Functional Safety Concept (FSC)

Field Value
Document ID FOX-SAF-FSC-001
Applicable Standard ISO 26262:2018 Part 4 — Product Development: System Level
System foxBMS 2 Battery Management System v1.10.0
Item Definition Li-ion BMS: 1 string, 1 module, 18s1p, NMC cells 3500 mAh
Date 2026-03-21
Status Released for Review
Related Documents FOX-SAF-HARA-001, FOX-SAF-TSC-001, FOX-SAF-FMEA-001

1 Scope and Purpose

This Functional Safety Concept (FSC) derives functional safety requirements from the safety goals defined in the HARA (FOX-SAF-HARA-001). For each safety goal, this document specifies:

The FSC serves as the bridge between the concept-level safety goals and the Technical Safety Concept (FOX-SAF-TSC-001) which maps these requirements to specific hardware and software elements.


2 Safe State Definition

2.1 Primary Safe State: Contactors Open (ERROR State)

The primary safe state for the foxBMS 2 BMS is the ERROR state in which all three contactors (string-plus, string-minus, precharge) are commanded open via the Smart Power Switch (SPS) driver. This state:

2.2 Secondary Safe State: Current Limitation

For hazards where immediate contactor opening could itself cause a hazard (e.g., loss of power steering/braking assist during highway driving), the BMS supports a degraded mode through the RSL (Recommended Safety Limit) tier:

2.3 Tertiary Warning: Early Notification

The MOL (Maximum Operating Limit) tier provides early warning before safety limits are reached:


3 FTTI Derivation Method

The Fault Tolerant Time Interval is the maximum time between the occurrence of a fault and the achievement of the safe state. For the foxBMS 2 diagnostic architecture, FTTI is composed of:

FTTI = T_detection + T_reaction + T_actuator

Where: - T_detection = threshold_count × task_period (time to accumulate enough diagnostic events to trigger FATAL) - T_reaction = delay_ms (additional debounce time configured in diag_cfg.c after threshold is reached) - T_actuator = contactor opening time (mechanical response, typically 20–50 ms for automotive contactors)

The task period depends on the diagnostic category: - SOA voltage/temperature/current checks: 10 ms (executed in BMS_Trigger from 10 ms task) - CAN timing checks: 10 ms (CAN periodic processing in 10 ms task) - Current sensor timeout: 10 ms (sensor communication check in 10 ms task) - System monitoring / flash checksum: 1 ms (system-level checks)


4 Functional Safety Requirements

4.1 FSR-01
↑ Traces Up
SG-01
: Cell Overvoltage Protection (SG-01
↓ Traces Down
FSR-01HZ-01
, ASIL D)

Attribute Specification
Safety Goal SG-01
↓ Traces Down
FSR-01HZ-01
: Prevent cell voltage exceeding 2800 mV
ASIL ASIL D
Functional Requirement The BMS shall continuously monitor each of the 18 cell voltages. If any cell voltage exceeds 2800 mV, the BMS shall interrupt the charge current path by opening all contactors.
Detection Per-cell voltage measurement via AFE at each measurement cycle. SOA check compares measured voltage against MSL threshold (2800 mV).
Safe State ERROR state — all contactors open
Warning Concept MOL threshold (lower than 2800 mV) triggers CAN warning message. RSL threshold triggers current limit reduction command via CAN. MSL threshold triggers contactor opening.
Degradation RSL: Reduce maximum charge current to zero (charge inhibit). Vehicle controller shall terminate charging session.
FTTI Calculation T_detection = 50 events × 10 ms = 500 ms. T_reaction = 200 ms (delay_ms). T_actuator = 50 ms. FTTI = 750 ms.
Physical Process Time Overvoltage at 2800 mV: Time to lithium plating onset depends on charge rate and temperature. At 1C charge rate, onset is ~10–30 minutes. At extreme overcharge (>4.5 V for NMC), onset is ~30 seconds. FTTI of 750 ms is well within the physical process time.
Verdict ADEQUATE — FTTI (750 ms) << physical process time (~30 s worst case)

4.2 FSR-02
↑ Traces Up
SG-02
: Cell Undervoltage Protection (SG-02
↓ Traces Down
FSR-02HZ-02
, ASIL C)

Attribute Specification
Safety Goal SG-02
↓ Traces Down
FSR-02HZ-02
: Prevent cell voltage below 1500 mV
ASIL ASIL C
Functional Requirement The BMS shall continuously monitor each of the 18 cell voltages. If any cell voltage drops below 1500 mV, the BMS shall interrupt the discharge current path by opening all contactors.
Detection Per-cell voltage measurement via AFE. SOA check against MSL threshold (1500 mV).
Safe State ERROR state — all contactors open
Warning Concept MOL threshold triggers low-voltage warning via CAN. RSL threshold triggers discharge current limit reduction. MSL threshold triggers contactor opening.
Degradation RSL: Reduce maximum discharge current progressively. Vehicle controller implements torque reduction.
FTTI Calculation T_detection = 50 × 10 ms = 500 ms. T_reaction = 200 ms. T_actuator = 50 ms. FTTI = 750 ms.
Physical Process Time Copper dissolution at 1500 mV is a slow electrochemical process. Significant copper dissolution requires sustained undervoltage for minutes to hours. FTTI is orders of magnitude shorter.
Verdict ADEQUATE — FTTI (750 ms) << physical process time (~minutes)

4.3 FSR-03
↑ Traces Up
SG-03
: Deep Discharge Protection (SG-03
↓ Traces Down
FSR-03HZ-03
, QM)

Attribute Specification
Safety Goal SG-03
↓ Traces Down
FSR-03HZ-03
: Detect deep discharge and open contactors immediately
ASIL QM (treated as FATAL for defense-in-depth)
Functional Requirement The BMS shall detect deep discharge conditions (cell voltage significantly below undervoltage cutoff or deep discharge flag from cell monitoring) and immediately open all contactors.
Detection DIAG_ID_DEEP_DISCHARGE_DETECTED: threshold=1, single event triggers FATAL
Safe State ERROR state — all contactors open. Additionally, the BMS shall not permit re-closure of contactors until the deep discharge condition is manually cleared by a service technician.
Warning Concept Immediate FATAL response (no MOL/RSL progression for deep discharge). DTC stored in non-volatile memory.
Degradation None — immediate safe state transition
FTTI Calculation T_detection = 1 × 10 ms = 10 ms. T_reaction = 100 ms. T_actuator = 50 ms. FTTI = 160 ms.
Physical Process Time Gas generation from deep discharge occurs over minutes to hours.
Verdict ADEQUATE — FTTI (160 ms) << physical process time

4.4 FSR-04
↑ Traces Up
SG-04
: Overcurrent Discharge Protection (SG-04
↓ Traces Down
FSR-04HZ-04
, ASIL B)

Attribute Specification
Safety Goal SG-04
↓ Traces Down
FSR-04HZ-04
: Limit discharge current and open contactors on persistent overcurrent
ASIL ASIL B
Functional Requirement The BMS shall monitor discharge current at both cell level (180000 mA limit) and string level (2400 mA limit). If current exceeds the MSL limit, the BMS shall open all contactors. The BMS shall communicate maximum allowable discharge current to the vehicle controller via CAN.
Detection String-level: IVT current sensor measurement, SOA check in 10 ms task. Cell-level: calculated from string current / parallel cell count.
Safe State ERROR state — all contactors open
Warning Concept MOL: High-current warning via CAN. RSL: Discharge current limit reduction via CAN. MSL: Contactor opening.
Degradation RSL: Progressive current derating communicated to vehicle controller. Vehicle implements torque reduction and speed limiting.
FTTI Calculation T_detection = 10 × 10 ms = 100 ms. T_reaction = 100 ms. T_actuator = 50 ms. FTTI = 250 ms.
Physical Process Time I²R heating at overcurrent: cell temperature rise rate depends on current magnitude. At 2× rated current, internal temperature rises at approximately 0.5 °C/s. Time to reach thermal runaway onset (~130 °C from 25 °C ambient) is ~210 s. For extreme short-circuit currents (>10× rated), heating rate is much faster (~5 s to critical temperature).
Verdict ADEQUATE — FTTI (250 ms) << physical process time (~5 s worst case)

4.5 FSR-05
↑ Traces Up
SG-05
: Overcurrent Charge Protection (SG-05
↓ Traces Down
FSR-05HZ-05
, ASIL C)

Attribute Specification
Safety Goal SG-05
↓ Traces Down
FSR-05HZ-05
: Limit charge current and open contactors on persistent overcurrent
ASIL ASIL C
Functional Requirement The BMS shall monitor charge current at both cell level (180000 mA limit) and string level (2400 mA limit). If current exceeds the MSL limit during charging, the BMS shall open all contactors. The BMS shall communicate maximum allowable charge current to the charger/vehicle controller via CAN.
Detection Same as FSR-04
↑ Traces Up
SG-04
but for charge direction (sign convention)
Safe State ERROR state — all contactors open
Warning Concept MOL: High charge current warning. RSL: Charge current limit reduction. MSL: Contactor opening.
Degradation RSL: Reduce charge current limit communicated to charger. Charger shall reduce charging power.
FTTI Calculation T_detection = 10 × 10 ms = 100 ms. T_reaction = 100 ms. T_actuator = 50 ms. FTTI = 250 ms.
Physical Process Time Lithium plating from overcurrent: onset depends on C-rate and temperature. At room temperature, plating onset at >3C requires sustained overcurrent for ~60 s. At high C-rates (>10C), onset time reduces to ~10 s.
Verdict ADEQUATE — FTTI (250 ms) << physical process time (~10 s worst case)

4.6 FSR-06
↑ Traces Up
SG-06
: Overtemperature Protection (SG-06
↓ Traces Down
FSR-06HZ-06
, ASIL C)

Attribute Specification
Safety Goal SG-06
↓ Traces Down
FSR-06HZ-06
: Monitor cell temperatures and open contactors on overtemperature
ASIL ASIL C
Functional Requirement The BMS shall monitor all 8 temperature sensors. If any sensor reading exceeds 45 °C (charge mode) or 55 °C (discharge mode), the BMS shall open all contactors to remove the current-induced heat source.
Detection Temperature measurement via AFE multiplexed NTC inputs. SOA temperature check in 10 ms task.
Safe State ERROR state — all contactors open
Warning Concept MOL: Temperature warning via CAN (e.g., at 40 °C charge / 50 °C discharge). RSL: Current derating based on temperature (reduce current to reduce I²R heating). MSL: Contactor opening at 45 °C / 55 °C.
Degradation RSL: Temperature-dependent current derating curve. As temperature approaches MSL threshold, maximum current is progressively reduced. This allows continued operation at reduced power.
FTTI Calculation T_detection = 500 × 10 ms = 5000 ms. T_reaction = 1000 ms. T_actuator = 50 ms. FTTI = 6050 ms (6.05 s).
Physical Process Time Thermal runaway onset from external heating: from 55 °C to thermal runaway onset (~130 °C), temperature rise rate depends on current and cooling. Adiabatic self-heating at >130 °C is self-sustaining. Time from 55 °C to 130 °C with continued current: ~30–300 s depending on current magnitude and cooling effectiveness.
Verdict ADEQUATE — FTTI (6.05 s) << physical process time (~30 s worst case)

4.7 FSR-07
↑ Traces Up
SG-07
: Undertemperature Charge Protection (SG-07
↓ Traces Down
FSR-07HZ-07
, ASIL B)

Attribute Specification
Safety Goal SG-07
↓ Traces Down
FSR-07HZ-07
: Prevent charging below -20 °C
ASIL ASIL B
Functional Requirement The BMS shall monitor all 8 temperature sensors. If any sensor reading is below -20 °C and the system is in charge mode, the BMS shall open all contactors to prevent cold-temperature lithium plating.
Detection Temperature measurement via AFE. SOA undertemperature check in 10 ms task.
Safe State ERROR state — all contactors open
Warning Concept MOL: Low temperature warning via CAN. RSL: Charge current limit set to zero (charge inhibit) at temperatures below the RSL threshold. MSL: Contactor opening at -20 °C.
Degradation RSL: Complete charge inhibit. No current derating — charging is fully prohibited below the RSL temperature threshold. Discharge may remain permitted with reduced current limits.
FTTI Calculation T_detection = 500 × 10 ms = 5000 ms. T_reaction = 1000 ms. T_actuator = 50 ms. FTTI = 6050 ms (6.05 s).
Physical Process Time Lithium plating at -20 °C: plating onset during 0.5C charge at -20 °C occurs within ~60–120 s. At lower C-rates, onset time extends proportionally.
Verdict ADEQUATE — FTTI (6.05 s) << physical process time (~60 s worst case)

4.8 FSR-08
↑ Traces Up
SG-08
: Contactor Welding Detection (SG-08
↓ Traces Down
FSR-08HZ-08
, ASIL B)

Attribute Specification
Safety Goal SG-08
↓ Traces Down
FSR-08HZ-08
: Detect contactor welding and prevent further operation
ASIL ASIL B
Functional Requirement The BMS shall read the feedback signal from each contactor (string+, string-, precharge) and compare it against the commanded state. If the feedback indicates the contactor is closed when the BMS has commanded it open, or vice versa, the BMS shall declare a contactor feedback fault.
Detection Contactor feedback GPIO reading compared against SPS command state. Checked in 10 ms BMS_Trigger context.
Safe State ERROR state. If the welded contactor is detected during opening: the BMS shall open the remaining non-welded contactors and signal a permanent fault. The string shall not be re-energized until the welded contactor is physically replaced.
Warning Concept No MOL/RSL progression — contactor welding is a hardware failure requiring immediate response. Immediate FATAL flag.
Degradation In multi-string configurations, the affected string is permanently isolated. The vehicle may continue operation on remaining strings with reduced power. In this single-string configuration, the vehicle is immobilized.
FTTI Calculation T_detection = 20 × 10 ms = 200 ms. T_reaction = 100 ms. T_actuator = 50 ms (for non-welded contactors). FTTI = 350 ms.
Physical Process Time If a contactor welds during a fault-current event, the fault current continues to flow. The time to reach a dangerous condition depends on the fault type. Worst case: short-circuit current through a welded contactor — time to thermal damage is ~1–5 s.
Verdict ADEQUATE — FTTI (350 ms) << physical process time (~1 s worst case)

4.9 FSR-09
↑ Traces Up
SG-09
: Current Sensor Failure Detection (SG-09
↓ Traces Down
FSR-09HZ-09
, ASIL B)

Attribute Specification
Safety Goal SG-09
↓ Traces Down
FSR-09HZ-09
: Detect current sensor failure and open contactors
ASIL ASIL B
Functional Requirement The BMS shall monitor the communication link to the IVT current sensor. If the sensor stops responding (no valid CAN messages received within the timeout period), the BMS shall open all contactors. Additionally, the BMS shall monitor the coulomb counting (CC) and energy counting (EC) channels and the three voltage measurement channels (V1, V2, V3) of the IVT.
Detection CAN message timeout monitoring. Each IVT channel has a dedicated DIAG ID.
Safe State ERROR state — all contactors open
Warning Concept Current sensor communication loss is treated as FATAL. No MOL/RSL progression because loss of current measurement capability is a complete loss of a safety-critical sensing path.
Degradation None — immediate safe state. The BMS cannot safely operate without current measurement.
FTTI Calculation Primary (CURRENT_SENSOR_RESPONDING): T_detection = 100 × 10 ms = 1000 ms. T_reaction = 200 ms. T_actuator = 50 ms. FTTI = 1250 ms. CC/EC channels: T_detection = 100 × 10 ms = 1000 ms. T_reaction = 2000 ms. T_actuator = 50 ms. FTTI = 3050 ms. V1/V2/V3: T_detection = 1 × 10 ms = 10 ms. T_reaction = 100 ms. T_actuator = 50 ms. FTTI = 160 ms.
Physical Process Time Loss of current sensing does not directly cause a hazard. The hazard arises only if a secondary fault (overcurrent) occurs simultaneously. Probability of coincidence within FTTI is very low.
Verdict ADEQUATE — FTTI covers the sensor loss; overcurrent protection is lost but probabilistic analysis shows acceptable residual risk.

4.10 FSR-10
↑ Traces Up
SG-10
: Interlock Monitoring (SG-10
↓ Traces Down
FSR-10HZ-10
, QM)

Attribute Specification
Safety Goal SG-10
↓ Traces Down
FSR-10HZ-10
: Detect interlock break and de-energize HV path
ASIL QM (treated as FATAL defense-in-depth)
Functional Requirement The BMS shall continuously monitor the interlock loop circuit. If the interlock loop is open (indicating HV connector disconnection or service cover removal), the BMS shall open all contactors within 200 ms.
Detection Interlock feedback GPIO signal monitoring. Checked in 10 ms task.
Safe State ERROR state — all contactors open
Warning Concept Immediate FATAL response. No warning progression.
Degradation None — immediate safe state
FTTI Calculation T_detection = 10 × 10 ms = 100 ms. T_reaction = 100 ms. T_actuator = 50 ms. FTTI = 250 ms.
Physical Process Time Interlock break implies physical access to HV components. Time from connector removal to skin contact: ~0.5–2 s (manual dexterity).
Verdict ADEQUATE — FTTI (250 ms) < physical process time (~0.5 s)

4.11 FSR-11
↑ Traces Up
SG-11
: Insulation Fault Detection (SG-11
↓ Traces Down
FSR-11HZ-11
, ASIL A)

Attribute Specification
Safety Goal SG-11
↓ Traces Down
FSR-11HZ-11
: Detect insulation faults and transition to safe state
ASIL ASIL A
Functional Requirement The BMS shall monitor pack voltage plausibility by comparing the sum of individual cell voltages (from AFE) against the pack voltage measurement (from IVT V1/V2/V3). A significant discrepancy indicates a potential insulation fault or measurement error. The BMS shall open all contactors if the plausibility check fails persistently.
Detection DIAG_ID_PLAUSIBILITY_PACK_VOLTAGE: comparison of AFE cell sum vs. IVT pack voltage.
Safe State ERROR state — all contactors open
Warning Concept FATAL on persistent plausibility failure.
Degradation None — immediate safe state
FTTI Calculation T_detection = 10 × 10 ms = 100 ms. T_reaction = 100 ms. T_actuator = 50 ms. FTTI = 250 ms.
Physical Process Time Insulation degradation is a slow process (hours to years). Once a fault path exists, time to dangerous contact depends on human interaction.
Verdict ADEQUATE — FTTI (250 ms) << physical process time

4.12 FSR-12
↑ Traces Up
SG-12
: Cell Imbalance Protection (SG-12
↓ Traces Down
FSR-12HZ-12
, ASIL C)

Attribute Specification
Safety Goal SG-12
↓ Traces Down
FSR-12HZ-12
: Enforce per-cell voltage limits regardless of string-level measurements
ASIL ASIL C
Functional Requirement The BMS shall monitor each of the 18 cell voltages individually and apply overvoltage (2800 mV) and undervoltage (1500 mV) limits on a per-cell basis. The safety mechanism shall not rely on pack-level or string-level voltage averaging. Each individual cell exceeding its limit shall independently trigger the safety reaction.
Detection Per-cell AFE measurement. Same DIAG IDs as FSR-01
↑ Traces Up
SG-01
and FSR-02
↑ Traces Up
SG-02
(CELL_VOLTAGE_OVERVOLTAGE_MSL, CELL_VOLTAGE_UNDERVOLTAGE_MSL). Detection inherently operates per-cell because the SOA check iterates over all cells.
Safe State ERROR state — all contactors open
Warning Concept Same three-tier MOL/RSL/MSL as FSR-01
↑ Traces Up
SG-01
and FSR-02
↑ Traces Up
SG-02
.
Degradation RSL: Current limiting based on the weakest cell.
FTTI Calculation Same as FSR-01
↑ Traces Up
SG-01
/FSR-02
↑ Traces Up
SG-02
: FTTI = 750 ms.
Verdict ADEQUATE — Same analysis as FSR-01
↑ Traces Up
SG-01
/FSR-02
↑ Traces Up
SG-02
applies

5 FTTI Summary Table

FSR Safety Goal ASIL T_detect (ms) T_react (ms) T_actuator (ms) FTTI (ms) Process Time Verdict
FSR-01
↑ Traces Up
SG-01
SG-01
↓ Traces Down
FSR-01HZ-01
ASIL D 500 200 50 750 ~30 s ADEQUATE
FSR-02
↑ Traces Up
SG-02
SG-02
↓ Traces Down
FSR-02HZ-02
ASIL C 500 200 50 750 ~minutes ADEQUATE
FSR-03
↑ Traces Up
SG-03
SG-03
↓ Traces Down
FSR-03HZ-03
QM 10 100 50 160 ~minutes ADEQUATE
FSR-04
↑ Traces Up
SG-04
SG-04
↓ Traces Down
FSR-04HZ-04
ASIL B 100 100 50 250 ~5 s ADEQUATE
FSR-05
↑ Traces Up
SG-05
SG-05
↓ Traces Down
FSR-05HZ-05
ASIL C 100 100 50 250 ~10 s ADEQUATE
FSR-06
↑ Traces Up
SG-06
SG-06
↓ Traces Down
FSR-06HZ-06
ASIL C 5000 1000 50 6050 ~30 s ADEQUATE
FSR-07
↑ Traces Up
SG-07
SG-07
↓ Traces Down
FSR-07HZ-07
ASIL B 5000 1000 50 6050 ~60 s ADEQUATE
FSR-08
↑ Traces Up
SG-08
SG-08
↓ Traces Down
FSR-08HZ-08
ASIL B 200 100 50 350 ~1 s ADEQUATE
FSR-09
↑ Traces Up
SG-09
SG-09
↓ Traces Down
FSR-09HZ-09
ASIL B 1000 200 50 1250 probabilistic ADEQUATE
FSR-10
↑ Traces Up
SG-10
SG-10
↓ Traces Down
FSR-10HZ-10
QM 100 100 50 250 ~0.5 s ADEQUATE
FSR-11
↑ Traces Up
SG-11
SG-11
↓ Traces Down
FSR-11HZ-11
ASIL A 100 100 50 250 ~hours ADEQUATE
FSR-12
↑ Traces Up
SG-12
SG-12
↓ Traces Down
FSR-12HZ-12
ASIL C 500 200 50 750 ~30 s ADEQUATE

6 Safety Mechanism Architecture

6.1 Three-Tier Diagnostic Response

The foxBMS 2 diagnostic system implements a three-tier response architecture that maps to the ISO 26262 warning and degradation concept:

               ┌─────────────────────────────────────────────┐
               │           Physical Measurement               │
               │  (Cell Voltage, Temperature, Current)         │
               └──────────────┬──────────────────────────────┘
                              │
                    ┌─────────▼──────────┐
                    │   SOA_Check*()      │
                    │   (10 ms cycle)     │
                    └──┬──────┬──────┬───┘
                       │      │      │
                 ┌─────▼┐  ┌─▼────┐ ┌▼─────┐
                 │ MOL   │  │ RSL  │ │ MSL  │
                 │ INFO  │  │ WARN │ │FATAL │
                 └───┬───┘  └──┬───┘ └──┬───┘
                     │         │        │
              ┌──────▼───┐ ┌───▼────┐ ┌─▼──────────┐
              │ CAN Msg   │ │ CAN +  │ │ DIAG_Handler│
              │ Warning   │ │ Current│ │ threshold   │
              │ to HMI    │ │ Limit  │ │ counter     │
              └──────────┘ │ via CAN│ └──────┬──────┘
                           └────────┘        │
                                      ┌──────▼──────┐
                                      │ FATAL flag   │
                                      │ set          │
                                      └──────┬──────┘
                                             │
                                      ┌──────▼──────┐
                                      │ BMS checks   │
                                      │ IsAnyFatal   │
                                      │ ErrorSet()   │
                                      └──────┬──────┘
                                             │
                                      ┌──────▼──────┐
                                      │ BMS →        │
                                      │ ERROR state  │
                                      └──────┬──────┘
                                             │
                                      ┌──────▼──────┐
                                      │ Contactors   │
                                      │ OPEN via SPS │
                                      └─────────────┘

6.2 Independence of Safety Mechanisms

For ASIL D safety goals (SG-01

↓ Traces Down
FSR-01HZ-01
), the diagnostic configuration provides independence through:

  1. Primary path: AFE cell voltage measurement → SOA_CheckCellVoltage() → DIAG_ID_CELL_VOLTAGE_OVERVOLTAGE_MSL → ERROR → contactor open
  2. Secondary path: IVT pack voltage measurement → plausibility check against AFE sum → DIAG_ID_PLAUSIBILITY_PACK_VOLTAGE → ERROR → contactor open
  3. Hardware watchdog: SBC (System Basis Chip) monitors BMS software execution. If the BMS software hangs, the SBC resets the microcontroller, causing contactors to open (fail-safe default).

7 Allocation to System Elements

Element Safety Function ASIL Allocation
AFE (LTC6813 or equiv.) Cell voltage and temperature measurement ASIL D(D)
IVT Current Sensor String current and pack voltage measurement ASIL B(D)
Microcontroller SOA checking, DIAG handling, BMS state machine ASIL D
SPS Driver Contactor control (actuation of safe state) ASIL D
SBC Watchdog, power supply supervision, reset control ASIL D
Interlock Circuit HV connector integrity monitoring QM
CAN Interface Communication of warnings, current limits, fault status ASIL B

8 References

Ref Document
[1] ISO 26262:2018 Part 4 — Product Development: System Level
[2] FOX-SAF-HARA-001 — Hazard Analysis and Risk Assessment
[3] FOX-SAF-TSC-001 — Technical Safety Concept
[4] FOX-SAF-FMEA-001 — Software FMEA
[5] FOX-SAF-FTTI-001 — FTTI Calculation Report
[6] foxBMS v1.10.0 src/app/engine/diag/diag_cfg.c
[7] foxBMS v1.10.0 src/app/application/config/soa_cfg.c

End of Document FOX-SAF-FSC-001