BESS factory acceptance testing should begin before the witness day. Put the delivered configuration, agreed test items, acceptance criteria, witness or hold points, required records, open-item process, and shipment-release authority into the RFQ and contract. Then use that same register at the factory.
Use this page in four moves: freeze the tested configuration; witness the agreed controls and records; close or disposition every exception; and hand the remaining site work to SAT with named owners. That is how a FAT becomes a procurement control rather than a factory visit.
FAT produces factory-scope evidence before shipment; SAT verifies the installed system and real site interfaces. For the commercial scope around those decisions, start with our solar container procurement and TCO guide. For the broader RFQ structure, see how to write an RFQ for containerized solar BESS.
Freeze the test plan before equipment arrives at the factory
An evidence-control failure occurs when the factory, buyer, EPC, and appointed third party work from different configuration revisions or different definitions of acceptance.
Before travel or remote witnessing, identify the system configuration, equipment identifiers, drawings, BOM, firmware/software baseline, test-procedure revision, acceptance criteria, and the authority that can make a shipment-release decision. Request instrument evidence where the contract requires it. A supplier’s quality-management-system certificate may be relevant context, but ISO 9001 addresses an organization’s QMS. If it is claimed, request the certificate scope, issuer, validity, and covered legal entity; it does not replace a project FAT procedure or prove that the offered BESS passed the specified test.
For a containerized BESS FAT, use the following BESS FAT checklist as the configuration-specific RFQ attachment or buyer-controlled test-plan register. Use its test-control column only for W, H, or N/A; record project roles in the separate RACI below.
| RFQ requirement / witness point | Test control: W / H / N/A | Required evidence | Leave for SAT or site scope |
|---|---|---|---|
| Freeze the delivered configuration, revision, and equipment identity to be tested. | Signed configuration baseline and document-revision list | Site as-built verification and field changes | |
| Approve procedure, test sequence, criteria, witness points, retest rules, and safety controls. | Approved FAT procedure and witness plan | Site safety and energization procedure | |
| Verify agreed identification, enclosure/build, service-interface, and supplied-auxiliary checks. | Inspection record; documented deviations | Delivery-condition inspection, placement, foundations, and clearances | |
| Demonstrate agreed BMS, PCS, and EMS states within the approved factory scope. | Test record; configuration/software revision; agreed logs | Actual grid, generator, and installed-interface operation | |
| Demonstrate agreed alarms, interlocks, shutdown, and reset/recovery logic. | Alarm/event log; test matrix; retest results | Site emergency response, local signaling, and authority requirements | |
| Review controlled drawings, interface schedule, manuals, packing list, and evidence register. | Controlled document register | Final local design, protection settings, and submissions | |
| Record failed items, waived tests, retests, and open items with owner, due date, and shipment effect. | Open-item/deviation log and disposition | SAT/site punch-list items in a separate log | |
| Define the FAT-to-SAT handover, site prerequisites, and responsible SAT-plan owner. | Handover index and SAT prerequisites | Installed-site tests and final acceptance |
Do not let a generic catalogue test list replace this register. The buyer’s required evidence should track the offered configuration and contract scope.
Treat factory evidence, shipment release, and SAT as separate decisions
For buyers comparing FAT vs SAT BESS responsibilities, retain three separate controls: the factory evidence record, the contract-defined shipment-release decision, and the installed-site acceptance process. Neither a shipment release nor a site acceptance test is the same as an authority or utility approval. Keep the decisions in separate logs and assign an owner to each.
| Decision | What the project should control | What it does not establish |
|---|---|---|
| Factory test evidence | Agreed procedure, configuration, test records, deviations, and retests | Installed-site interfaces, local design, or final project acceptance |
| Contract-defined shipment release | Release authority, remaining exceptions, packing/document handover | Carrier acceptance, customs outcome, delivery condition, or site readiness |
| SAT / site acceptance | Installed configuration, agreed site functions, interfaces, and site evidence | A replacement for utility/AHJ/insurer decisions unless their scope says so |
| Utility / AHJ / insurer process | Project-specific submission, review, and decision path | A conclusion that FAT secured approval |
This distinction matters when the project carries a long open-item list. A factory exception can transfer to later closure only through a written, contract-defined disposition. Record its owner, required evidence, due date, shipment impact, and whether it transfers to the separate SAT/site-punch process. For timeline context, see our solar container deployment timeline guide.
Assign the FAT-to-SAT handover before anyone travels
The table below turns the witness plan into actions and owners. Replace the labels with the parties named in your project scope.
| Activity | Supplier | Buyer / owner | EPC / local engineer | Appointed third party | Site team / operator |
|---|---|---|---|---|---|
| Freeze configuration and FAT document baseline | R | A | C | I | I |
| Draft the configuration-specific FAT procedure | R | A | C | C | I |
| Classify witness, hold, review, and N/A points | C | A | C | R/C if appointed | I |
| Execute agreed factory tests and collect records | R | W if agreed | C | W if appointed | I |
| Log deviations, retests, and open items | R | A | C | C | I |
| Decide FAT reservations and contract-defined shipment release | C | A/R | C | C | I |
| Assemble the FAT evidence pack and handover index | R | A/R | C | C | I |
| Confirm site-readiness inputs and plan SAT | I/C | A | R | I | R/C |
R = responsible; A = accountable project party; C = consulted; I = informed; W = witness/review only when appointed or agreed in the approved plan.
Add standards evidence only when it changes the FAT plan
Do not turn the FAT into a generic standards list. Add a standards item only when the contract, jurisdiction, or project reviewer needs a specific record. For example, cite the relevant IEC 62933 part and edition where it is named in the project specification. If a North American fire-safety review requires a UL 9540A test report, compare its tested configuration and assumptions with the offered system. For locally adopted U.S. installation codes, NFPA 855 may shape the site submission—not the factory witness list by default. Record the requested evidence, configuration, reviewer, and destination gate in the register.
Define the FAT-to-SAT handover before release
The factory evidence pack should identify completed work, open items, the tested configuration, and the records the site team needs. For this buyer-controlled workflow, the handover index should identify the approved procedure, attendance/witness record, results and conditions, document register, deviation/open-item log, retest evidence, release decision, and SAT prerequisites.
Remote-interface testing is one example of the handover. FAT can record agreed alarm paths, event-log retrieval, and specified loss-of-communications behavior. SAT then verifies installed communications, network ownership, access routes, and the actual site interface. Our remote BESS maintenance guide explains the operational boundary in more detail.
Request an RFQ-ready FAT plan for your configuration
Use the project RFQ enquiry form to send the configuration/BOM revision, country and site context, witness scope, acceptance criteria, expected interfaces, and required records. Use those inputs to structure the RFQ conversation around the factory evidence the project needs.
