Battery Energy Storage Systems (BESS) contain large quantities of lithium-ion batteries, so international transportation is subject to strict safety and dangerous-goods regulations. One common question from BESS developers and EPC contractors is: What certificates are required before a BESS container can be shipped?
There is no single “BESS transportation certificate.” Instead, several certificates, test reports, declarations and container approvals may be required depending on how the batteries are configured and whether transportation is by sea, road, rail or air.
1. UN 38.3 Test Report and Test Summary
The most important battery transportation requirement is UN 38.3.
Lithium cells and batteries intended for transportation must generally meet the testing requirements in Part III, Subsection 38.3 of the UN Manual of Tests and Criteria. Tests address transport-related conditions such as altitude, thermal cycling, vibration, shock, external short circuit, impact/crush and overcharge. UNECE
Manufacturers must also make a UN 38.3 Test Summary available. It contains information such as:
- Battery manufacturer and model
- Battery type and mass
- Watt-hour rating
- Test laboratory
- Test report number
- Tests performed and pass/fail results
The UN 38.3 document is therefore one of the first documents a freight forwarder or dangerous-goods specialist will check.
2. Correct UN Dangerous Goods Classification
A complete containerized BESS can often be transported as:
UN 3536 – LITHIUM BATTERIES INSTALLED IN CARGO TRANSPORT UNIT
This classification is intended for lithium battery systems installed inside a cargo transport unit and designed to provide electrical power outside that unit. UNECE
However, classification must be confirmed case by case.
For example, batteries shipped separately rather than installed as a complete BESS may instead fall under classifications such as UN 3480 – Lithium ion batteries or other applicable entries.
The correct UN number determines the required documentation, labelling, placarding, handling and transport procedures.
3. IMDG Dangerous Goods Documentation for Sea Freight
For ocean transportation, BESS shipments must comply with the International Maritime Dangerous Goods Code — IMDG Code.
As of 1 January 2026, IMDG Code Amendment 42-24 is mandatory for international maritime dangerous-goods transport. International Maritime Organization
Typical shipping documentation may include:
- Dangerous Goods Declaration
- Multimodal Dangerous Goods Form
- Correct UN number and proper shipping name
- Hazard classification
- Container/vehicle packing information
- Emergency contact information
Exact requirements should be confirmed with the shipping line, dangerous-goods consultant and authorities at origin and destination.
4. CSC Certificate for the BESS Container
If the BESS enclosure is an ISO freight container used for international transportation, CSC approval is normally another key requirement.
The International Convention for Safe Containers establishes structural safety requirements covering testing, lifting, stacking, racking and container strength. Approved freight containers carry a CSC Safety Approval Plate showing information such as maximum gross mass and allowable stacking load. International Maritime Organization
This is particularly important for heavy BESS containers because a 20-foot BESS can approach the maximum allowable transport weight.
5. SDS / MSDS and Supporting Battery Documentation
Carriers and freight forwarders commonly request a Safety Data Sheet (SDS/MSDS) describing the lithium battery chemistry, hazards and emergency-response information.
The SDS should not be confused with UN 38.3. An SDS describes the product and hazards; UN 38.3 demonstrates that the battery design has passed the required transport tests.
Other supporting documents may include battery specifications, packing lists, gross-weight information and emergency-response documentation.
What About UL 9540, UL 9540A and IEC 62619?
Standards such as IEC 62619, UL 9540 and UL 9540A are important for battery and energy-storage safety, project certification and fire-risk assessment. However, they should not be treated as replacements for transportation requirements such as UN 38.3, dangerous-goods classification and CSC approval.
Conclusion
For a typical containerized lithium-ion BESS transported internationally, the core compliance package normally includes UN 38.3 battery testing, correct UN dangerous-goods classification, IMDG dangerous-goods documentation for sea freight, and CSC approval for the freight container.
TLS Energy designs and manufactures containerized BESS solutions with transportation, structural safety, battery integration and international deployment requirements considered from the beginning of the design process. Correctly planning transportation compliance during the BESS design stage can significantly reduce shipment delays, port problems and unexpected project costs. International Maritime Organization
