Typical pack and system structures¶
Per GB 38031-2025, Appendix A (Informative). The structures below are illustrative reference architectures — real designs vary, and the standard does not mandate any particular topology.
A.1 Typical battery pack¶
A battery pack typically includes:
- Battery cells (the energy storage elements)
- Components — busbars, fuses, relays, sensors
- High-voltage circuits — main power path from cells to pack terminals
- Overcurrent protection devices — fuses, contactors, current sensors with cutoff logic
- External interfaces:
- Cooling system inlet/outlet (coolant)
- High-voltage power
- Auxiliary low-voltage (12 V or similar)
- Communication (typically CAN)
Source: Appendix A, Figure A.1.
A.2 Typical battery system¶
The standard distinguishes two architectures based on where the Battery Control Unit (BCU) lives:
A.2.1 Battery system with integrated BCU¶
The BCU is housed inside the battery pack enclosure. The system presents a single electrical interface to the rest of the vehicle, including high-voltage output, low-voltage power/comms, and cooling interfaces.
Common in passenger vehicles (M1, N1) where space is constrained and the simpler integration is preferred.
Source: Appendix A, Figure A.2.
A.2.2 Battery system with externally integrated BCU¶
The BCU is mounted outside the battery pack, typically elsewhere in the vehicle (e.g., engine bay or floor pan). The pack provides cell-level data over a communication link to the external BCU, which handles high-level state estimation, charge control, and thermal management commands.
Common in commercial vehicles and where multiple battery packs are managed by a single controller.
Source: Appendix A, Figure A.3.
How this matters for testing¶
The pack/system architecture affects several test methods:
| Test | What changes by architecture |
|---|---|
| Insulation resistance (Appendix B) | Whether BCU's insulation monitoring must be disabled during measurement (depends on whether it's inside the pack and active). |
| Same type determination (clause 9) | Conditions on BMS hardware, software version, and protection thresholds (9.1 j) treat the BMS/BCU as a defining component. Changing BCU vendor or major software version can break "same type." |
| Electrical protection tests (8.2.11–8.2.15) | The BCU's protection logic is what's actually being tested. External-BCU systems may need additional fixturing to simulate vehicle-level signals. |
Engineering note (non-normative): The "battery system" definition in 3.4 includes "management systems" (i.e., the BCU and supporting electronics) as part of the system, regardless of whether the BCU is physically inside the pack enclosure. So a "battery system" test under 8.2.11–8.2.15 must include whatever portion of the BMS/BCU stack actually executes the protection logic — even if those components live elsewhere in the vehicle in the production configuration.
Engineering note (non-normative): Appendix A is informative (not normative). The figures are reference examples — they don't prescribe a particular architecture. A pack without a separate BCU, or a system using a non-standard topology, can still meet GB 38031-2025 as long as the safety requirements in §5 and the test methods in §8 are satisfied.
Source: GB 38031-2025, Appendix A (PDF p. 30–31).