BMS Cell-Balancing Verification SOP — CN→LU Corridor

Vertical: Solar Balance-of-Systems (BoS) · Document type: Process / Standard Operating Procedure · Revision: 2026-Q3

1. Scope and Purpose

This Standard Operating Procedure defines how TradVolt verifies the cell-balancing function of Battery Management Systems (BMS) integrated with solar Balance-of-Systems equipment shipped from original equipment manufacturers in China to project sites in Luxembourg. The SOP exists to detect balancing faults before energisation on-site, and to provide an auditable evidence file for the customer.

[Claim: Cell-balancing faults detected pre-shipment reduce on-site commissioning risk | Src: IEC 62619 | URL: https://webstore.iec.ch/publication/65959 | Accessed: 2026-09-21]

2. Normative References

IEC 62619 — Secondary lithium cells for industrial applications, including stationary applications.
UL 1973 — Standard for Batteries for Use in Stationary, Vehicle Auxiliary Power and Light Electric Rail (LE) Applications.
ISO 2859-1 — Sampling procedures by attributes, AQL framework.
ICC Incoterms® 2020 — DAP Luxembourg terms assumed as default corridor delivery basis.
FIATA Multimodal Transport Document guidance.

3. Step Sequence

Step #	Action	Owner	Input doc	Output doc	Done-when
1	Open inbound shipment, reconcile packing list with commercial invoice and customs paperwork.	Warehouse Lead	Packing list, commercial invoice, CN→LU customs declarations	Goods Received Note (GRN)	GRN signed and quantities match; deviations logged.
2	Move BMS units to ESD-safe, climate-controlled verification cell (15–25 °C).	Warehouse Lead	GRN	Staging log	Units grounded; staging log entry recorded.
3	Connect OEM service tool, apply nominal bus voltage, confirm BMS firmware handshake.	BMS Technician	OEM service manual (per model), firmware version sheet	Handshake record	Firmware version and serial number logged; telemetry visible.
4	Record resting per-cell voltage (mV) after 1 h settling; compute ΔVmax.	BMS Technician	OEM service manual tolerance table	Baseline voltage sheet	ΔVmax ≤ OEM-specified threshold (mV) for each unit.
5	Apply controlled discharge to lowest-voltage cell using bench supply until ΔV trigger met.	BMS Technician	OEM service manual, bench PSU	Imbalance induction log	ΔV between weakest and strongest cell ≥ trigger threshold.
6	Enable active balancing and log balancing current (A) and duration (s) until convergence.	BMS Technician	OEM service manual pass criteria	Balancing response log	ΔVmax returns within OEM-specified mV band within stated s.
7	Capture cell and balancer PCB temperatures (°C) with calibrated thermocouples.	BMS Technician	OEM service manual thermal limits	Thermal log	All readings ≤ OEM thermal limit (°C).
8	Apply ISO 2859-1 attribute sampling; classify lot Pass / Conditional / Fail.	Quality Engineer	Per-unit logs, AQL sampling plan	Lot classification sheet	AQL decision recorded with sampled n and Ac/Re values.
9	Compile verification report with serial numbers, photos, and raw CSV logs.	Quality Engineer	All per-unit logs, calibration certificates	Customer Verification Report (PDF)	Report reviewed and counter-signed by QA Manager.
10	Archive evidence pack and release lot for onward dispatch under DAP Luxembourg.	Documentation Officer	Signed verification report, raw logs	Archived evidence pack in project folder	Files stored with read-only hash; lot marked release-ready.

[Claim: Attribute sampling per ISO 2859-1 governs lot acceptance decisions | Src: ISO 2859-1 | URL: https://www.iso.org/standard/11418.html | Accessed: 2026-09-21]

4. Documentation Checklist

The following files must exist in the project folder before the lot is marked released. Filenames are literal.

01_GRN_[ProjectID]_[Date].pdf
02_StagingLog_[ProjectID].xlsx
03_HandshakeRecord_[ProjectID].csv
04_BaselineVoltage_[ProjectID].xlsx
05_ImbalanceInduction_[ProjectID].csv
06_BalancingResponse_[ProjectID].csv
07_ThermalLog_[ProjectID].csv
08_AQLClassification_[ProjectID].pdf
09_VerificationReport_[ProjectID]_[Rev].pdf
10_CalibrationCerts_Bundle_[ProjectID].pdf

5. Corridor Timeline (CN → LU, indicative)

Stage	Owner	Duration	Depends on
Pre-shipment QA at CN factory	Supplier QA	2 days	—
Export customs clearance (CN)	Freight forwarder	1 day	Pre-shipment QA
Multimodal transit CN → LU port/airport	Carrier (FIATA-issued MTD)	7 days (indicative)	Export clearance
Import customs clearance (LU)	Customs broker	1 day	Goods arrival, HS-coded paperwork
Inbound BMS verification (this SOP)	TradVolt QA	2 days	Import clearance
DAP Luxembourg delivery to site	Last-mile carrier	1 day	Verification Pass

Transit durations are indicative and depend on carrier schedule, port congestion, and customs workload; values are NOT lead-time commitments.

6. Cost Slots

Cost element	Basis	Value
Verification labour	Per unit, indicative	UNCERTAIN — request quote
AQL re-test (if Conditional)	Per re-tested unit, indicative	UNCERTAIN — request quote
Documentation pack	Per lot, indicative	UNCERTAIN — request quote
EU import duty	Per HS code, official portal	PENDING — lookup, see §7

7. Duty / HS Block

Equipment class: Lithium-ion battery management systems and stationary lithium battery assemblies intended for solar Balance-of-Systems installations.

Indicative HS code candidates (must be confirmed by a licensed customs broker for the exact shipment):

8507.60 — Lithium-ion accumulators (battery assemblies).
8537.10 — Boards/panels for electric control, incl. BMS controllers.

Applicable duty / VAT rates: PENDING — lookup at the official EU Customs Trader Portal (TARIC consultation).

Official portal: European Commission — Access2Markets / TARIC — https://ec.europa.eu/taxation_customs/dds2/taric/taric_consultation.jsp?Lang=en.

HS classification and duty/VAT rates are shipment-specific and must be confirmed by a licensed customs broker against the exact tariff measure in TARIC at the time of import. No rate is hardcoded in this SOP.

[Claim: Official EU tariff measures are published in the TARIC database | Src: European Commission TARIC | URL: https://ec.europa.eu/taxation_customs/dds2/taric/ | Accessed: 2026-09-21]

[Claim: Incoterms DAP designates the seller responsible up to the named place of delivery in the country of import | Src: ICC Incoterms® 2020 | URL: https://iccwbo.org/business-solutions/incoterms-rules/incoterms-2020/ | Accessed: 2026-09-21]

8. Roles and Responsibilities

Warehouse Lead: Goods receipt, ESD staging, chain-of-custody.
BMS Technician: Functional verification steps 3–7.
Quality Engineer: Sampling decision, report compilation, sign-off.
Documentation Officer: Filing, archival, evidence integrity.
QA Manager: Counter-signs the verification report.

9. Records and Retention

All artefacts listed in §4 are retained for the duration of the warranty period plus statutory minimums applicable in Luxembourg. Raw CSV logs are immutable once signed; corrections are made by appending a delta file, not by editing the original.

10. Call to Action

Request Quote — replies in 48h Download checklist (PDF)

Revision history

Rev	Date	Change
2026-Q3	2026-09-21	Initial release, CN→LU corridor.