Article 480

Storage Batteries

  1. Scope. This article applies to all stationary installations of storage batteries.Informational Note: The following standards are frequently referenced for the installation of stationary batteries:
    1. IEEE 484, Recommended Practice for Installation Design and Installation of Vented Lead-Acid Batteries for Stationary Appli‐ cations
    2. IEEE 485, Recommended Practice for Sizing Vented Lead-Acid Storage Batteries for Stationary Applications
    3. IEEE 1145, Recommended Practice for Installation and Main‐ tenance of Nickel-Cadmium Batteries for Photovoltaic (PV) Systems
    4. IEEE 1187, Recommended Practice for Installation Design, and Installation of Valve-Regulated Lead-Acid Batteries for Stationary Applications
    5. IEEE 1375, IEEE Guide for the Protection of Stationary Battery Systems
    6. IEEE 1578, Recommended Practice for Stationary Battery Elec‐ trolyte Spill Containment and Management
    7. IEEE 1635/ASHRAE 21, Guide for the Ventilation and Ther‐ mal Management of Batteries for Stationary Applications
    8. UL 1973, Standard for Batteries for Use in Light Electric Rail (LER) Applications and Stationary Applications
    9. UL Subject 2436, Outline of Investigation for Spill Contain‐ ment for Stationary Lead Acid Battery Systems
    10. UL 1989, Standard for Standby Batteries
  2. Definitions.Cell. The basic electrochemical unit, characterized by an anode and a cathode, used to receive, store, and deliver electri‐ cal energy.Container. A vessel that holds the plates, electrolyte, and other elements of a single unit in a battery.Informational Note: A container may be single-cell or multi-cell and is sometimes referred to in the industry as a “jar.”Electrolyte. The medium that provides the ion transport mech‐ anism between the positive and negative electrodes of a cell.Intercell Connector. An electrically conductive bar or cable used to connect adjacent cells.Intertier Connector. An electrical conductor used to connect two cells on different tiers of the same rack or different shelves of the same rack.Nominal Voltage (Battery or Cell). The value assigned to a cell or battery of a given voltage class for the purpose of convenient designation. The operating voltage of the cell or battery may vary above or below this value.Informational Note: The most common nominal cell voltages are 2 volts per cell for the lead-acid systems, 1.2 volts per cell for alkali systems, and 3.6 to 3.8 volts per cell for Li-ion systems. Nominal voltages might vary with different chemistries.Sealed Cell or Battery. A cell or battery that has no provision for the routine addition of water or electrolyte or for external measurement of electrolyte specific gravity and might contain pressure relief venting.Storage Battery. A battery comprised of one or more recharge‐ able cells of the lead-acid, nickel-cadmium, or other rechargea‐ ble electrochemical types.Terminal. That part of a cell, container, or battery to which an external connection is made (commonly identified as post, pillar, pole, or terminal post).imageN
  3. Equipment. Storage batteries and battery management equipment shall be listed. This requirement shall not apply to lead-acid batteries.
  4. Battery and Cell Terminations.
  1. Corrosion Prevention. Where mating dissimilar metals, antioxidant material suitable for the battery connection shall be used where recommended by the battery manufacturer.Informational Note: The battery manufacturer’s installation and instruction manual can be used for guidance for acceptable materials.
  2. Intercell and Intertier Conductors and Connections. The ampacity of field-assembled intercell and intertier connectors and conductors shall be of such cross-sectional area that the temperature rise under maximum load conditions and at maxi‐ mum ambient temperature shall not exceed the safe operating temperature of the conductor insulation or of the material of the conductor supports.Informational Note: Conductors sized to prevent a voltage drop exceeding 3 percent of maximum anticipated load, and where the maximum total voltage drop to the furthest point of connec‐ tion does not exceed 5 percent, may not be appropriate for all battery applications. IEEE 1375-2003, Guide for the Protection of
      Stationary Battery Systems, provides guidance for overcurrent protection and associated cable sizing.
  3. Battery Terminals. Electrical connections to the battery, and the cable(s) between cells on separate levels or racks, shall not put mechanical strain on the battery terminals. Terminal plates shall be used where practicable.

Informational Note: Conductors are commonly pre-formed to

eliminate stress on battery terminations. Fine stranded cables may also eliminate the stress on battery terminations. See the manufacturer’s instructions for guidance.

  1. Wiring and Equipment Supplied from Batteries. Wiring and equipment supplied from storage batteries shall be subject to the applicable provisions of this Code applying to wiring and equipment operating at the same voltage, unless otherwise permitted by 480.6.
  2. Overcurrent Protection for Prime Movers. Overcurrent protection shall not be required for conductors from a battery with a voltage of 60 volts dc or less if the battery provides power for starting, ignition, or control of prime movers. Section 300.3 shall not apply to these conductors.
  3. DC Disconnect Methods.
    1. Disconnecting Means. A disconnecting means shall be provided for all ungrounded conductors derived from a stationary battery system with a voltage over 60 volts dc. A disconnecting means shall be readily accessible and located within sight of the battery system.Informational Note: See 240.21(H) for information on the loca‐ tion of the overcurrent device for battery conductors.
    2. Remote Actuation. Where a disconnecting means, located in accordance with 480.7(A), is provided with remote controls to activate the disconnecting means and the controls for the disconnecting means are not located within sight of the station‐ ary battery system, the disconnecting means shall be capable of being locked in the open position, in accordance with 110.25, and the location of the controls shall be field marked on the disconnecting means.
    3. Busway. Where a DC busway system is installed, the disconnecting means shall be permitted to be incorporated into the busway.
    4. Notification. The disconnecting means shall be legibly marked in the field. A label with the marking shall be placed in a conspicuous location near the battery if a disconnecting means is not provided. The marking shall be of sufficient dura‐ bility to withstand the environment involved and shall include the following:
    1. Nominal battery voltage
    2. Maximum available short-circuit current derived from the stationary battery system
    3. Date the short-circuit current calculation was performed
    4. The battery disconnecting means shall be marked in accordance with 110.16.

    Informational Note No. 1: Battery equipment suppliers can provide information about short-circuit current on any particu‐ lar battery model.Informational Note No. 2: The available short-circuit current marking(s) addressed in 480.7(D)(2) is related to required short-circuit current ratings of equipment. NFPA 70E-2015, Standard for Electrical Safety in the Workplace, provides assistance in
    imagedetermining the severity of potential exposure, planning safework practices, and selecting personal protective equipment.
  4. Insulation of BatteriesBatteries constructed of an elec‐ trically conductive container shall have insulating support if a voltage is present between the container and ground.•
  5. Battery Support Systems. For battery chemistries withcorrosive electrolyte, the structure that supports the battery shall be resistant to deteriorating action by the electrolyte. Metallic structures shall be provided with nonconducting support members for the cells, or shall be constructed with a continuous insulating material. Paint alone shall not be consid‐ ered as an insulating material.•The terminals of all cells or multi-cell units shall be readilyaccessible for readings, inspection, and cleaning where required by the equipment design. One side of transparent battery containers shall be readily accessible for inspection of the internal components.
  6. Battery Locations. Battery locations shall conform to 480.10(A), (B), and (C).
    1. Ventilation. Provisions appropriate to the battery technol‐ ogy shall be made for sufficient diffusion and ventilation of gases from the battery, if present, to prevent the accumulation of an explosive mixture.Informational Note No. 1: See NFPA 1-2015, Fire Code, Chap‐ ter 52, for ventilation considerations for specific battery chemis‐ tries.Informational Note No. 2: Some battery technologies do not require ventilation.
      Informational Note No. 3: For additional information on theventilation of stationary battery systems, see IEEE Std 1635-2012/ ASHRAE Guideline 21-2012 Guide for the Ventilation and Thermal Management of Batteries for Stationary Applications.
    2. Live Parts. Guarding of live parts shall comply with 110.27.
    3. Spaces About Battery Systems. Spaces about battery systems shall comply with 110.26. Working space shall be meas‐ ured from the edge of the battery cabinet, racks, or trays.For battery racks, there shall be a minimum clearance of 25 mm (1 in.) between a cell container and any wall or struc‐ ture on the side not requiring access for maintenance. Battery stands shall be permitted to contact adjacent walls or struc‐ tures, provided that the battery shelf has a free air space for not less than 90 percent of its length.Informational Note: Additional space is often needed to accom‐ modate battery hoisting equipment, tray removal, or spill containment.
    4. Top Terminal Batteries. Where top terminal batteries are installed on tiered racks or on shelves of battery cabinets, work‐ ing space in accordance with the battery manufacturer’s instructions shall be provided between the highest point on a cell and the row, shelf, or ceiling above that point.Informational Note: IEEE 1187-2013, IEEE Recommended Practice for Installation Design and Installation of Valve-Regulated Lead-Acid Batteries for Stationary Applications, provides guidance for top clearance of valve-regulated lead-acid batteries, which are commonly used in battery cabinets.
    5. Egress. A personnel door(s) intended for entrance to, and egress from, rooms designated as battery rooms shall open
      in the direction of egress and shall be equipped with listed panic hardware.
    6. Piping in Battery Rooms. Gas piping shall not be permit‐ ted in dedicated battery rooms.
    7. Illumination. Illumination shall be provided for working spaces containing battery systems. The lighting outlets shall not be controlled by automatic means only. Additional lighting outlets shall not be required where the work space is illumina‐ ted by an adjacent light source. The location of luminaires shall not:
    1. Expose personnel to energized battery components while performing maintenance on the luminaires in the battery space; or
    2. Create a hazard to the battery upon failure of the lumin‐ aire.
  7. Vents.
  1. Vented Cells. Each vented cell shall be equipped with a flame arrester.Informational Note: A flame arrester prevents destruction of the cell due to ignition of gases within the cell by an external spark or flame.
  2. Sealed Cells. Where the battery is constructed such that an excessive accumulation of pressure could occur within the cell during operation, a pressure-release vent shall be provided.