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Uninterruptible Power Supply (UPS) System - Retrofitting/replacing with New Batteries

Knowing which batteries can be replaced with uninterruptible power supply systems, depends on considering a number of codes, product listings, markings and installation instructions.

Racks of Uninterruptible Power Supply (UPS) Systems

May 20, 2020

Authored by: Jeffrey A. Fecteau, Senior Regulatory Engineer

Is it permissible to replace the batteries of an Uninterruptable Power System (UPS) system? The answer depends on a variety of factors that will be explained in this article. This article will identify the NFPA 70, National Electric Code (NEC), International Fire Code (IFC), International Building Code (IBC), NFPA 1 (Fire Code) and NFPA 5000 (Building Construction and Safety Code) requirements as well as the marking requirements in UL 1778, the Standard for Uninterruptible Power Systems, for UPS equipment with regards to battery replacement.

Applicable Codes

The 2020 NEC Article 100 defines a UPS as a power supply used to provide alternating current power to a load for some period of time in the event of a power failure. Several sections of the NEC such as 645.11, 700.12(E), 701.12(E) and 708.20(G) address certain requirements for a UPS when installed for use with information technology, emergency systems, legally required standby systems or critical operation power systems. Additionally, NEC Section 110.3(B) requires that listed equipment be installed and used in accordance with any instructions included in the listing or labeling.

Both the IFC (Sections 1203.1.3, 1203.4 and 1203.5) and the IBC (Section 2702.1.3) identify that a UPS installed as either an emergency power systems or as a standby power systems shall be installed, inspected, tested and maintained in accordance with the NEC, NFPA 110 (Standard for Emergency and Standby Power Systems) and NFPA 111 (Standard on Stored Electrical Energy Emergency and Standby Power Systems).  Both NFPA 1 (Sections 11.7.4, and NFPA 5000 (Section require that stored electrical emergency and legally required standby power systems be installed and maintained in accordance with the NEC and NFPA 111.

Listed Uninterruptible Power-supply Equipment

UL Certifies (Lists) UPS equipment under UL product category for Uninterruptible Power-supply Equipment (YEDU). The basic Standard used to investigate products in this category is UL 1778.

The UL guide information and Certifications (Listings) can be viewed on UL Product iQ™ available at; Product iQ is free to use, but requires a onetime registration.  Once registered, simply enter YEDU in the search field. Products covered by YEDU include indoor- and outdoor-use UPS equipment that may be stationary or fixed. This equipment is rated 600 V or less and is intended for use in accordance with the NEC.

This category also covers UPS equipment that is rebuilt by the original manufacturer or another party having the necessary facilities, technical knowledge and manufacturing skills. UPS equipment can be rebuilt to the extent necessary by disassembly and reassembly using new or reconditioned parts. Rebuilt UPS equipment is subject to the same requirements as new UPS equipment.

The UL product category for Electrical Equipment for Use in Ordinary Locations (AALZ) has general information pertaining to electrical equipment for use in unclassified (ordinary) locations that is intended to be installed in accordance with the NEC. The UL product category AALZ states that authorized use of the UL Certification Mark is the manufacturer's declaration that a product was manufactured in accordance with the applicable certification requirements, and was in compliance with those requirements when it was shipped from the factory. When a product bearing a UL Certification Mark is modified or rebuilt – including being refurbished, remanufactured, reconditioned or renovated – after it leaves the factory where the UL Certification Mark was applied, UL does not know if the product continues to meet the applicable requirements unless the modification or rebuilding has been specifically investigated by UL. To identify modified or rebuilt equipment investigated by UL, look for a UL Certification Mark that includes one of the following statements:

  • UL Rebuilt Product Certifications
  • UL Field Evaluated Products
  • UL Retrofit Certifications

The only exception to this is when a UL Certified (Listed) product has specific markings for field-installed equipment or the replacement of components.  UPS equipment evaluated to UL 1778 has an expected usage life that typically exceeds the usage life of the batteries it contains. Battery replacement in UPS equipment is considered part of normal maintenance and is evaluated as part of the original Certification (Listing).  The necessary markings and instructions to ensure continued safety and certification are identified in the instructions and the individual certification documentation.

Markings and Installation Instructions

UL 1778 requires that battery cabinets be clearly and legibly marked in such a way so that the following information can been seen by servicing personnel prior to accessing the battery compartment:

  • Battery manufacturer name and catalog number
  • Number of batteries
  • Nominal voltage of the total battery string
  • Nominal capacity of the total battery string

UL 1778 additionally requires that the UPS instructions contain the following information:

  • Sufficient information – including suitable manufacturer and catalog number – to enable the replacement of a battery
  • Identification of the battery type, e.g., sealed or valve-regulated, etc.
  • A message to use replacement batteries with a specific model number from a specific manufacturer
  • A caution statement identifying the risk of energy hazard, ______ V, ______ Ampere-hour (watt or kilowatt) battery


It is permissible to replace the batteries of a UPS with specific types of batteries that are identified by the manufacturer of the UPS system on the equipment and within the product instructions as required by UL 1778.

It is not permissible to replace the batteries of a UPS with battery types not identified on the equipment and within the instructions such as batteries other than valve regulated or vented types. Interchanging valve regulated and vented battery types is also not permitted. Replacing batteries in this manner is considered modifying the equipment and UL does not know if modified products continue to meet the applicable safety requirements unless the modification has been specifically investigated by UL. Evidence that UL has specifically investigated the modification can only be demonstrated by a product that bears either UL’s rebuilt Certification (Listing) Mark or UL’s Field Evaluation label.

For additional information on Certified (Listed) uninterruptible power-supply (UPS) equipment, please contact Jeff Fecteau at


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