Before a battery energy storage system reaches site, buyers want evidence that the delivered package matches the approved design. For a BESS container supplied as an empty enclosure, inspection can verify the structure, finish, doors and specified interface provisions. It cannot verify battery operation, electrical protection, cooling performance or control logic when those systems are outside the supply scope.
Recent TLS content discusses factory acceptance testing (FAT) for integrated BESS. The same quality-planning principle applies to enclosure-only orders: define the checks and acceptance criteria before production, and make sure the inspection plan reflects what is being purchased.
Separate enclosure inspection from system FAT
FAT is often used to describe checks performed at the factory before shipment. Its scope varies by contract. An integrated BESS FAT may include mechanical, electrical, thermal, control, communication and safety tests when those systems are supplied and available for testing.
An enclosure-only order has a narrower boundary. The inspection can confirm the physical product against its drawings and specification. It should not be described as a complete BESS FAT if the container ships without batteries, PCS, BMS, cooling equipment, fire systems and controls. The buyer, enclosure manufacturer and system integrator should assign each test to the party that supplies or installs the relevant equipment.
Build an inspection plan from the approved drawings
The approved drawing set should identify dimensions, openings, doors, structural interfaces, lifting points, finish requirements and any project-specific accessories within scope. A practical inspection plan then turns those requirements into observable checks, with an agreed method and acceptance criterion for each one.
For example, the plan may specify which overall dimensions are measured, how door operation is checked, what finish documentation is required and how cable openings are compared with the approved interface drawing. Inspection points should be selected to suit the order and any applicable standards or customer specifications. There is no single universal checklist for all container projects.
Typical checks for an enclosure-only package
Dimensions and configuration
Confirm the external dimensions, door locations, equipment openings and overall configuration against the latest approved drawings. If the buyer has specified internal clearances or mounting interfaces, record how these will be checked and which drawing revision governs acceptance.
Structure and lifting provisions
Review the structural features and lifting points included in the design. The project documents should state the applicable design basis and any required inspection or test evidence. Do not assume a lifting certification, offshore classification or a particular load rating unless it is expressly included and documented for that unit.
Doors, access and sealing details
Operate doors and access panels to confirm that they open and close as intended. Check the installed hardware and sealing details against the approved scope. If the project requires a water-ingress or other performance test, define the method and acceptance level in the specification; a visual inspection alone does not prove a particular ingress-protection rating.
Cable openings and customer interfaces
Compare the number, location and size of the agreed cable openings with the interface schedule. Verify frames, blanking arrangements or sealing components only when these are part of the order. Cable glands, cable trays and electrical terminations should not be presumed included.
Coating and corrosion protection
Where specified, review coating records and carry out agreed visual or thickness checks. The inspection standard, sampling plan, measurement locations and acceptance limits should be agreed in advance. Required performance depends on the site environment and the selected coating system.
Documentation to request at handover
The purchase order can list the records required for release. Depending on the project, these may include approved as-built drawings, material or weld documentation, coating records, dimensional inspection results, non-conformance closeout and a final inspection report. Only request records relevant to the supplied scope and applicable specification.
The handover package should make clear what the buyer or integrator must complete after delivery. Site installation, final grounding, customer cabling, equipment installation and integrated system commissioning may sit outside the enclosure supplier’s work.
Plan tests that require integrated equipment separately
If the project expects checks of BMS communication, PCS functions, battery alarms, thermal controls or fire-system responses, identify which supplier provides the equipment and who leads the test. Those functions require an agreed system configuration, test procedure, inputs, expected responses and acceptance criteria. An enclosure supplier cannot demonstrate functions of equipment it does not provide.
For a multi-party project, a responsibility matrix can help connect enclosure inspection, equipment FAT, site acceptance testing and commissioning. The goal is to avoid both gaps and duplicate tests while keeping each result traceable to the responsible party.
FAQ
1.Is enclosure inspection the same as BESS FAT?
No. Enclosure inspection covers the contracted container structure and interfaces. A system FAT may cover electrical, battery, thermal, controls and safety functions if those systems are included and available for testing.
2.Can an empty container be certified as IP55 through a visual check?
A visual check alone does not establish an IP rating. Any required ingress-protection rating and verification method must be specified and assessed for the completed design under the applicable test or certification process.
3.Should lifting tests be included in every container order?
The required lifting design basis and verification depend on the application, governing requirements and contract. The buyer should state the intended transport and lifting conditions and request the applicable evidence in the specification.
4.Who tests the BMS, PCS and cooling system?
The suppliers or integrator responsible for those systems should define and perform the relevant tests. The project should document responsibilities and interfaces before the factory test stage.
Conclusion
TLS conducts Factory Acceptance Testing according to its established FAT standards and the requirements applicable to the supplied package. For an enclosure-only order, FAT focuses on the container structure, dimensions, doors, finish and specified interfaces. When batteries, PCS, BMS or other systems are included in TLS’s supply, the applicable tests can also cover those integrated systems.
The FAT scope follows what is included in the project delivery. This gives the customer a clear record of what TLS has inspected and tested before shipment, while identifying any equipment or site checks handled by other suppliers or the system integrator.
