UL 1973 for UPS Batteries: Requirements, Scope and OEM Considerations

Lithium-ion batteries are increasingly used in uninterruptible power supply (UPS) systems for data centers, telecommunications infrastructure, and industrial facilities. For UPS manufacturers, battery suppliers, and system integrators, selecting a suitable battery involves more than comparing capacity and voltage. The battery must also meet the safety and compliance requirements applicable to the intended product and market.

UL 1973 is an important safety standard for battery systems used in applicable stationary applications, including UPS installations. However, battery certification alone does not establish that the complete UPS is compliant or that the battery is compatible with every UPS model.

This guide explains what UL 1973 covers, how it differs from other relevant standards, and what OEMs should verify before approving a lithium UPS battery for integration or procurement.

What Is UL 1973 for UPS Lithium Batteries?

UL 1973, Batteries for Use in Stationary and Motive Auxiliary Power Applications, establishes safety requirements for battery systems within its scope, including applicable UPS battery applications.

For lithium-ion batteries, the standard evaluates safety under specified conditions, including applicable simulated abuse tests. It does not establish a universal guarantee of battery capacity, backup runtime, cycle life, or compatibility with every UPS.

For OEMs, three separate questions need to be answered:

• Safety: Does the battery have the required safety evaluation for the intended application?
• Performance: Can it deliver the required backup power and runtime under specified operating conditions?
• Integration: Can it operate within the UPS electrical, communication, and installation requirements?

As of October 2026, UL Standards & Engagement lists UL 1973 Edition 3 as active. Before beginning a new qualification project, verify the applicable edition, revisions, and certification requirements with the relevant certification body.

UL 1973 vs. UL 1778 vs. IEC 62619

These standards address different aspects of battery and UPS safety. The appropriate compliance pathway depends on the product configuration, target market, customer specifications, and applicable regulations.

When should an OEM prioritize UL 1973?

For UPS products intended for North American customers, evaluate UL 1973 early when the battery falls within its scope and the applicable certification pathway or customer specification calls for it.

UL 1778 addresses the safety of UPS equipment. A battery's UL 1973 certification does not automatically establish compliance of the integrated UPS.

When is IEC 62619 relevant?

IEC 62619:2022 specifies safety requirements and tests for secondary lithium cells and batteries used in industrial applications, including UPS systems. It may be relevant to projects serving international markets, depending on customer specifications and the applicable compliance framework.

UL 1973 and IEC 62619 should not be assumed to be interchangeable. Confirm which standard is accepted for the specific product, market, and project.

Does every UPS battery require UL 9540?

No. UL 9540 addresses energy storage systems and equipment within its scope. Whether it applies depends on the product classification, intended use, and relevant requirements. It should not be treated as a universal requirement for every UPS battery.

How to Verify a UL 1973-Certified UPS Battery

A certification claim is only useful when the supporting evidence matches the product being purchased. Before approving a supplier, verify the following information.

Check the certification record and product scope

Request the applicable certification record, model schedule, and relevant supporting documentation. Confirm the manufacturer, model designation, electrical ratings, and configuration covered by the evaluation.

Pay particular attention to the distinction between a cell, module, battery pack, and complete battery system. Documentation covering one component does not necessarily demonstrate that the entire proposed assembly has been evaluated to the same standard.

A supplier declaration, laboratory test report, and product certification record are different forms of evidence. Verify the certification through the appropriate official directory or certification organization, and ask for clarification if the product scope is unclear.

Review the technical documentation

The exact documentation required depends on the project and certification pathway. If a document is unavailable, ask the supplier or certification body what alternative evidence is acceptable.

For a broader assessment of engineering, validation, and production capability, see our guide to evaluating a custom lithium UPS battery manufacturer.

Confirm Compatibility Before Integrating the Battery

A battery can have the relevant safety certification and still be unsuitable for a particular UPS. OEMs should validate the battery against the actual UPS specifications rather than relying on nominal voltage or capacity alone.

Electrical compatibility

• DC voltage range: Confirm that the battery's operating limits match the UPS DC bus requirements.
• Charging profile: Check the permitted charging voltage, current, and control requirements.
• Discharge capability: Verify that the battery can support the expected load and discharge conditions.
• Protection coordination: Confirm that battery protection and UPS fault responses operate as intended.
• BMS communication: Where required, validate the protocol, data mapping, alarms, and shutdown behavior.

For example, a battery may have the correct nominal voltage but an incompatible maximum charging voltage. Such a mismatch must be resolved before the combination is approved.

Where the project requires a tailored electrical or communication configuration, review our guide to a custom lithium UPS battery system.

For a product-specific reference, see the 48V lithium-ion UPS battery and review its documented voltage, charging, discharge, temperature, and certification information. Its specifications should not be assumed to apply to other battery models.

Runtime and environmental validation

UL 1973 does not guarantee a specific backup duration. Runtime must be evaluated against the intended load, UPS conversion efficiency, battery discharge characteristics, end-of-discharge limits, and required design margin.

Also confirm the permitted operating temperature, cooling requirements, enclosure conditions, and installation instructions against the actual environment.

Use documented acceptance criteria and representative operating conditions to validate performance. For detailed capacity calculations, see our guide to UPS battery sizing calculations.

What Happens If the Battery Design Changes?

Changes to a previously qualified battery may affect its certification scope or compatibility with the UPS. Examples include:

• Replacing the original cell with a different model.
• Changing the BMS, firmware, or protective components.
• Modifying the battery configuration, electrical ratings, or enclosure.
• Changing connectors, wiring, or thermal management arrangements.

Not every change automatically requires complete recertification. The impact depends on the existing certification, the nature of the change, and the applicable requirements.

Before approving a change, the OEM should:

1. Obtain a written description of the proposed change.
2. Identify the affected models, components, and ratings.
3. Ask the supplier to explain the potential certification impact.
4. Confirm with the certification body whether a review, additional testing, or revised documentation is required.
5. Update approved product configurations and supplier records as appropriate.

The key principle is to assess certification against the actual approved configuration, not simply the product family name.

Final OEM Approval Checklist

Before approving a UPS battery supplier or releasing a battery for production, confirm that the following decisions have been resolved.

• Does the certification cover the exact battery model and configuration?
• Have the applicable battery, UPS, market, and customer requirements been identified?
• Can the certification record and relevant supporting documents be verified?
• Have voltage, charging, discharge current, protection limits, and BMS communication been checked against the UPS specifications?
• Has the required backup runtime been validated under the intended operating conditions?
• Has the responsible team confirmed whether the integrated configuration is covered by the UPS evaluation?
• Is there a process for reviewing changes to cells, BMS components, firmware, and other relevant parts?

Assign unresolved questions to the appropriate team:

• Certification body: Standard applicability, certification scope, and the effect of design changes.
• UPS engineering: Electrical compatibility, BMS coordination, runtime, and system integration.
• Procurement and quality: Document verification, product traceability, and supplier change control.

Frequently Asked Questions

Is UL 1973 mandatory for every UPS lithium battery?

Not universally. Requirements depend on the target market, applicable codes, product certification pathway, and customer specifications. Confirm the requirements for the specific project before selecting the battery.

Can an IEC 62619-certified battery replace a UL 1973-certified battery?

Not automatically. The standards have distinct scopes and certification pathways. Acceptance of one in place of the other must be confirmed for the intended market and application.

What if a supplier provides a certificate but not the full test report?

Verify the certification record first and determine what it covers. Ask the supplier or certification body whether additional documentation is necessary for the intended application. A full test report may not be required for every procurement decision, but the available evidence must be sufficient to establish compliance with the applicable requirements.

Can a UL 1973-certified battery be used in any UPS?

No. The battery's operating limits, charging requirements, discharge capability, communication interface, installation conditions, and the UPS's applicable requirements must be checked for the specific combination.

Conclusion

UL 1973 is an important safety standard for battery systems used in applicable UPS applications, but certification is only one part of battery qualification.

OEMs should establish the applicable compliance pathway, verify the exact certified configuration, and validate electrical compatibility, BMS coordination, runtime, and integration with the complete UPS. When a supplier proposes a design change or replacement battery, its impact on existing certification and product approval should be confirmed before implementation.

This approach turns certification from a procurement checkbox into a documented qualification process, helping manufacturers make better-supported decisions about battery safety, compatibility, and product compliance.

Official references:

• UL Standards & Engagement — UL 1973
• UL Solutions — UPS Safety and Compliance with UL 1778
• IEC — IEC 62619:2022
• UL Solutions — Energy Storage System Testing and Certification