TradVolt › Processes › Battery Rack Torque Audit (CN→IN)

Battery Rack Torque Audit — Corridor CN→IN

Process / SOP · Vertical: Solar BoS · Issued: 2026-09-21 · Owner: TradVolt QA Desk

Verdict: This SOP audits rack bolted-joint torque to OEM specification via ISO 2859-1 AQL sampling (General Inspection Level II, AQL 1.0). Pass = every sampled joint inside the OEM N·m band (per Sungrow SBR128/256 or CATL EnerC rack manual); Fail = any joint outside band or any wrench out of calibration. Equipment in scope: Sungrow SBR128 / SBR256 battery rack and CATL EnerC battery rack on the CN→IN solar BoS lane. Location: supplier factory, China (FCA/FOB) or designated Indian site (CIF/DAP). Horizon: ~10 working days from PO receipt to audit-report sign-off. Evidence date: 2026-09-21. Limitation: torque windows are OEM-specific; for any other rack family the inspector must pull the matching OEM service manual and replace the values in torque_register.xlsx before audit. Request Quote — replies in 48h

Field	Value
Equipment family	Sungrow SBR128 / SBR256 LFP battery rack; CATL EnerC rack
OEM service manual	Sungrow SBR Series Installation Manual (rev 1.5, 2024-03); CATL EnerC Installation & Service Manual (rev 2.1, 2024-06)
AQL plan	ISO 2859-1, General Inspection Level II, AQL 1.0 for attribute "torque within band"
Audit length	~3 working days on site (D-1 setup, D 0 audit, D+1 NCR/report draft)
Inspection point	Per Incoterms 2020 (FCA/FOB = supplier factory CN; CIF/DAP = Indian port/site)
Pass criterion	All sampled joints inside OEM N·m ± tolerance; calibrated wrench; no NCR open
Limitation	Not a substitute for cell-level weld or DC string commissioning audits

Download Audit Checklist (PDF)

1. Scope and Applicability

This SOP applies to bolted battery mounting racks forming part of a solar-plus-storage BoS consignment from China to India, where the rack family is one of the named models below (or another OEM model added with its own manual reference). It covers M6/M8/M10 bolted joints between rack modules and the base frame / cabinet, torqued per the rack OEM service manual. It does not cover cell-level welding, BMS firmware commissioning, or DC string commissioning, which sit under separate procedures.

Models in scope (with public OEM sources):

Sungrow SBR128 (12.8 kWh LFP battery module rack, used with Sungrow hybrid inverters SH3.0–SH6.0RS and SH8.0–SH25T). Product page: https://en.sungrowpower.com/product/sbr. Installation manual reference: Sungrow SBR Series Installation Manual, document code SBR-IM-EN, revision 1.5 (2024-03), published at https://en.sungrowpower.com/upload/files/2024/03/SBR-Installation-Manual-EN.pdf. [Claim: Sungrow publishes SBR installation manuals publicly on its global product site. | accessed 2026-09-21]
Sungrow SBR256 (25.6 kWh, two SBR128 modules stacked on a single base). Same manual as above covers the bolted base-frame joints. URL: https://en.sungrowpower.com/upload/files/2024/03/SBR-Installation-Manual-EN.pdf. [accessed 2026-09-21]
CATL EnerC (rack-mounted LFP container battery, ~3 MWh per unit). Product page: https://www.catl-energy.com/product/enerc.html. Installation/service manual: CATL EnerC Installation & Service Manual, revision 2.1 (2024-06), published at https://www.catl-energy.com/upload/files/2024/06/EnerC-Installation-Service-Manual-EN.pdf. [accessed 2026-09-21]

2. Reference Documents

OEM Service Manual — Sungrow SBR-IM-EN rev 1.5 (2024-03) or CATL EnerC Installation & Service Manual rev 2.1 (2024-06); specifies torque window for M6/M8/M10 grade 8.8/10.9 joints, the torque-wrench calibration requirement, and tightening sequence. URLs above. [Claim: rack OEMs publish bolt-grade-specific torque values in their installation manuals. | accessed 2026-09-21]
ISO 2859-1:1999 — sampling procedures by attributes, used to draw the AQL sample from the inspection lot. [Claim: ISO 2859-1 defines AQL sampling plans for inspection lots. | Src: ISO 2859-1:1999 | URL: https://www.iso.org/standard/1141.html | accessed 2026-09-21]
Incoterms® 2020 — ICC publication; defines buyer/seller obligations including inspection location. [Src: ICC | URL: https://iccwbo.org/business-solutions/incoterms-rules/incoterms-2020/ | accessed 2026-09-21]
IEC 62477-1:2012 / AMD1:2016 — safety requirements for power electronic converter systems; covers bolted-joint safety for adjacent BoS. [Src: IEC 62477-1 | URL: https://webstore.iec.ch/publication/62886 | accessed 2026-09-21]
FIATA Multimodal Transport Documents — used when the CN→IN move includes road or rail legs beyond the ocean bill of lading. [Src: FIATA | URL: https://fiata.org/ | accessed 2026-09-21]
UN Manual of Tests and Criteria, Rev. 7 (2023), Section 38.3 — referenced for LFP cell transport classification (UN3480) when the rack ships containing cells. [Src: UN Manual of Tests and Criteria | URL: https://unece.org/transport/dangerous-goods/un-manual-tests-and-criteria | accessed 2026-09-21]

3. Torque Specification Table (OEM-sourced)

Rack family / model	Joint	Bolt grade	Target torque	Tolerance band	Wrench type	Source (URL)
Sungrow SBR128 / SBR256 — base-to-floor	M10	8.8 zinc-plated	35 N·m	±3 N·m	Click-type, 20–100 N·m, calibrated	SBR-IM-EN rev 1.5, §4.2
Sungrow SBR128 / SBR256 — module-to-module stacking bolt	M8	8.8	18 N·m	±2 N·m	Click-type, 5–50 N·m, calibrated	SBR-IM-EN rev 1.5, §4.3
Sungrow SBR128 / SBR256 — side bracket to base	M6	8.8	8 N·m	±1 N·m	Click-type, 2–20 N·m, calibrated	SBR-IM-EN rev 1.5, §4.4
CATL EnerC — rack base to ISO container cross-member	M12	10.9	85 N·m	±5 N·m	Click-type, 40–200 N·m, calibrated	EnerC ISM rev 2.1, §5.1
CATL EnerC — battery module to rack rail	M8	8.8	20 N·m	±2 N·m	Click-type, 5–50 N·m, calibrated	EnerC ISM rev 2.1, §5.2

For any rack model not listed, the inspector must pull that OEM's installation/service manual and add a row to torque_register.xlsx before the audit. Generic "rack OEM" is not acceptable on a torque procedure.

4. Step-by-Step Procedure

Step #	Action	Owner	Input doc	Output doc	Done-when
1	Receive PO, packing list, rack BOM, and rack model number from supplier	TradVolt Procurement	Supplier PO file	`shipment_file_v1.xlsx`	PO line items match rack quantity and model
2	Confirm Incoterm® 2020 term and inspection location	TradVolt Logistics	Purchase order	`incoterm_note.md`	Incoterm code and inspection point logged
3	Pull HS code for the rack and the fasteners into the shipment file	TradVolt Customs Desk	Indian Customs Tariff	`hs_block.json`	HS codes present; rates marked PENDING
4	Schedule pre-shipment inspection date with supplier QA	TradVolt QA Lead	Supplier calendar	`psi_appointment.pdf`	Date, time, and contact confirmed in writing
5	Extract OEM-specified torque values per bolt grade from §3 sources	TradVolt QA Inspector	Sungrow SBR-IM-EN rev 1.5 or CATL EnerC ISM rev 2.1	`torque_register.xlsx`	Each bolt size has a target N·m and tolerance band, cited to manual §
6	Draw AQL sample lot per ISO 2859-1 General Inspection Level II, AQL 1.0	TradVolt QA Inspector	`shipment_file_v1.xlsx`	`aql_sample.xlsx`	Sample size logged; AQL = 1.0
7	Verify torque-wrench calibration certificate is current (≤12 months, ISO 6789-1 traceable)	TradVolt QA Inspector	Calibration cert	`tool_log.md`	Cert within validity window; serial number logged
8	Apply controlled torque to each sampled joint in OEM-specified sequence; record reading	TradVolt QA Inspector	`torque_register.xlsx`	`torque_readings.xlsx`	Every sampled joint has a numeric N·m reading
9	Compare readings against OEM window; flag out-of-tolerance joints as NCR	TradVolt QA Lead	`torque_readings.xlsx`	`ncr_register.md` (if any)	Pass / fail decision recorded per sample unit
10	Compile audit checklist, photos, and readings into PDF report	TradVolt QA Lead	All of the above	`battery_rack_torque_audit_report.pdf`	Report signed by inspector and supplier rep
11	File report, NCRs, and customs docs in the shipment folder	TradVolt Document Control	All artefacts	`shipment_file_final.zip`	Folder complete; archive timestamp recorded

5. Inspection Checklist (filenames)

01_shipment_file_v1.xlsx
02_incoterm_note.md
03_hs_block.json
04_psi_appointment.pdf
05_torque_register.xlsx — columns: joint, bolt size, grade, target N·m, ± band, OEM manual §
06_aql_sample.xlsx — columns: sample unit ID, joint type, drawing method
07_tool_log.md
08_torque_readings.xlsx — columns: sample unit ID, joint, applied N·m, pass/fail
09_ncr_register.md — only if NCRs raised
10_battery_rack_torque_audit_report.pdf

Checklist mirror: battery-rack-torque-audit-checklist.pdf

6. Timeline and Dependencies

Day	Activity	Depends on	Owner
D-14	PO and packing list received	Supplier commercial team	TradVolt Procurement
D-12	HS code and Incoterm confirmed	PO file	TradVolt Customs / Logistics
D-10	OEM torque datasheet (Sungrow or CATL) reviewed	Supplier document pack	TradVolt QA Lead
D-7	PSI date booked with supplier	Supplier production plan	TradVolt QA Lead
D-3	Travel and visa (if required) arranged	PSI date	TradVolt Logistics
D-1	Wrench calibration verified; AQL sample drawn	Calibration cert; lot list	TradVolt QA Inspector
D 0	On-site torque audit executed (~1 working day for ≤50 rack units; scale linearly)	Sample drawn; wrench calibrated	TradVolt QA Inspector
D+1	NCRs raised; report drafted	Audit readings	TradVolt QA Lead
D+2	Report signed and filed	Supplier rep acknowledgement	TradVolt QA Lead
D+3	Shipment released; customs filing prepared	Final report	TradVolt Customs Desk
D+5 to D+10	Ocean transit CN→IN	Bill of lading; FIATA docs if multimodal	TradVolt Logistics

7. Cost Slots (indicative / uncertain)

Cost item	Status	Note
QA inspector day rate (China)	indicative	Confirm per engagement letter
Round-trip travel and visa	indicative	Depends on departure city
Calibrated torque-wrench rental (per ISO 6789-1)	indicative	Local hire at supplier site preferred
AQL lab fee (if subcontracted)	UNCERTAIN	Quoted per lot size
Indian customs duty / IGST	PENDING — lookup	See Section 8
Demurrage / detention buffer at Indian port	UNCERTAIN	Container availability at discharge port

8. Duty / HS Block

Equipment / parts in scope: Sungrow SBR128 / SBR256 racks, CATL EnerC racks, and associated M6/M8/M10/M12 grade 8.8/10.9 fasteners (bolts, washers, nuts) for solar-plus-storage BoS assemblies, shipped CN→IN.

Item	HS code (proposed)	Rate	Source portal
Sungrow SBR128 / SBR256 rack assembly (steel/aluminium frame)	7610.90 (aluminium structures) or 7308.90 (steel structures) — verify per exact composition	PENDING — lookup	Indian Customs Tariff — CBIC
CATL EnerC rack assembly	7610.90 / 7308.90 / 9406.90 (prefabricated building modules) — verify per end-use classification	PENDING — lookup	Indian Customs Tariff — CBIC
Fasteners (bolts, nuts, washers) grade 8.8/10.9	7318.xx group — verify per alloy and grade	PENDING — lookup	Indian Customs Tariff — CBIC

Disclaimer: HS classifications and applicable rates depend on exact material composition, intended use, and any applicable exemptions or concessional notifications (e.g., Mega Power / Solar Project EPC exemptions under Indian Customs notifications). The codes listed above are placeholders for verification. Confirm via the official CBIC Indian Customs Tariff portal, or via the Customs Broker of Record, before filing the Bill of Entry. TradVolt does not provide binding tariff advice.

9. Standards and Transport Classification (quick reference)

UN3480 — Lithium-ion batteries (installed in the rack) under UN Manual of Tests and Criteria, Rev. 7 (2023), §38.3. UN Manual.
IEC 62477-1:2012 / AMD1:2016 — safety for power electronic converter systems and adjacent BoS. IEC Webstore.
ISO 6789-1 — torque tool calibration (referenced for wrench cert acceptance).

10. Call to Action

Request Quote — replies in 48h Download Audit Checklist (PDF)