Battery room
Encyclopedia
A battery room is a room in a facility used to house batteries
for backup or uninterruptible power systems. Battery rooms are found in telecommunication
central offices, and to provide standby power to computing equipment in datacenters. Batteries provide direct current
(DC) electricity, which may be used directly by some types of equipment, or which may be converted to AC by uninterruptible power supply
(UPS) equipment. The batteries may provide power for minutes, hours or days depending on the electrical system design, although most commonly the batteries power the UPS during brief electric utility outages lasting only seconds.
Battery rooms were used to segregate the fumes and corrosive chemicals of wet cell batteries from the operating equipment; a separate room also allowed better control of temperature and ventilation for the batteries. In 1890 the Western Union
central telegraph office in New York City had 20,000 wet cells, mostly primary zinc-copper type, in use.
s, which also serve to maintain full charge on the battery systems. In the event of a utility failure, the load is supported from the battery until an emergency power source can be applied, such as a generator
. The typical design of a battery in the telecommunications application is to provide DC power to the load equipment for a minimum of four hours if a generator is also installed at the site. If a generator is not installed at the site, the typical design of a battery system is to support the load equipment for eight hours. If a utility outage appears to be for an extended duration (such as during a hurricane or ice storm
) a mobile generator would be mobilized to a site (that does not have a generator installed) to recharge the battery system and support the site until utility power can be restored.
For outages longer than a few seconds, the batteries must continue to provide power until an emergency power source
can be started. Facilities that have no emergency power source follow a written manual protocol that dictates an orderly shutdown of the highest electrical demand equipment to extend battery life, followed after a specified interval by a complete power-down before the batteries are exhausted. As mentioned earlier, the batteries most frequently provide power for a UPS during brief, transient electric utility outages lasting at most, seconds. When electric utility outages last over 15 seconds to one minute, the UPS or the Automatic Transfer Switch (ATS)
recognizes this as a long duration power outage and signals an emergency power source to start. After the emergency power source is started and is allowed to stabilize, an Automatic Transfer Switch disconnects the facility from the electric utility and connects the emergency power source to provided replacement AC electricity to the facility, including the UPS. Once the emergency power source, such as a diesel engine-generator
(genset) or gas turbine
coupled to a generator
, is online, the UPS ceases drawing power from the battery room, and recharging the batteries begins with DC power supplied by the UPS or a free-standing battery charger. After electric utility power is restored, the batteries are again called on to supply power during the very brief period while the Automatic Transfer Switch disconnects the emergency power source and reconnects the electric utility. Recharging the batteries can add considerable additional load to the emergency power source, potentially overloading it. To avoid this, most UPS systems large enough to require a battery room have, as part of their electronic controls, a signal wire from the Automatic Transfer Switch that the ATS energizes when emergency power is active. When this signal wire is energized, the UPS recharges the batteries at a preselected reduced rate. When electric utility power is restored, full rate recharging resumes.
The interval the battery room provides electric power is known as ride-through, and a battery room is rated by the maximum amount of ride-through time it can provide at maximum rated load. An approximately reciprocal relationship exists between the ride-through time and the electrical load on the batteries. Thus, a battery room rated to provide 15 minutes of ride-through while delivering a maximum 900 amperes at 48 volts will provide more than 30 minutes of ride-through if the actual demand is only 450 amperes. The total capacity (product of current and time, or ampere-hour
s) increases at lower current discharge rates, an effect called Peukert's law
.
The type of battery most commonly employed in battery rooms is the flooded lead-acid battery
. Batteries are installed in groups. Several batteries are wired together in a series circuit forming a group providing DC electric power at 12, 24, 48 or 60 volts (or higher). Usually there are two or more groups of series-connected batteries. These groups of batteries are connected in a parallel circuit. This arrangement allows an individual group of batteries to be taken offline for service or replacement without compromising the availability of uninterruptible power. Generally, the larger the battery room's electrical capacity, the larger the size of each individual battery and the higher the room's DC voltage.
s where reliable power is required for operation of switchgear
, critical standby systems, and possibly black start
of the station. Often batteries for large switchgear line-ups are 125 V or 250 V nominal systems, and feature redundant battery chargers with independent power sources. Separate battery rooms may be provided to protect against loss of the station due to a fire in a battery bank. For stations that are capable of black start, power from the battery system may be required for many purposes including switchgear operations.
The world's largest battery is in Fairbanks, Alaska
, composed of Ni-Cd
cells. Sodium-sulfur batteries
are being used to store wind power
.
s of the diesel-electric type, where they contain the batteries used for undersea propulsion of the vessel. Even nuclear submarines contain large battery rooms as backups to provide maneuvering power if the nuclear reactor is shutdown. Batteries in surface vessels may also be contained in a battery room.
Battery rooms on ocean-going vessels must prevent mixture of seawater with acid, since this will produce toxic hydrogen chloride
gas. This is of particular concern on submarines.
gas especially if overcharged, ventilation of a battery room is critical to maintain the concentration below the lower explosive limit.
The life span of secondary batteries is reduced at high temperature and the energy storage capacity is reduced at low temperature, so a battery room must have heating or cooling to maintain the proper temperature.
Batteries may contain large quantities of corrosive electrolyte
s such as sulfuric acid
used in lead-acid batteries or potassium hydroxide
used in nickel-cadmium batteries. Materials of the battery room must resist corrosion and contain any accidental spills. Plant personnel must be protected from spilled electrolyte. In some jurisdictions, large battery systems may contain reportable amounts of sulfuric acid, a concern for fire departments. Battery rooms in industrial and utility installations typically have an eye-wash station nearby, so that workers who are accidentally splashed with electrolyte can immediately wash it away from the eyes.
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
for backup or uninterruptible power systems. Battery rooms are found in telecommunication
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
central offices, and to provide standby power to computing equipment in datacenters. Batteries provide direct current
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
(DC) electricity, which may be used directly by some types of equipment, or which may be converted to AC by uninterruptible power supply
Uninterruptible power supply
An uninterruptible power supply, also uninterruptible power source, UPS or battery/flywheel backup, is an electrical apparatus that provides emergency power to a load when the input power source, typically mains power, fails...
(UPS) equipment. The batteries may provide power for minutes, hours or days depending on the electrical system design, although most commonly the batteries power the UPS during brief electric utility outages lasting only seconds.
Battery rooms were used to segregate the fumes and corrosive chemicals of wet cell batteries from the operating equipment; a separate room also allowed better control of temperature and ventilation for the batteries. In 1890 the Western Union
Western Union
The Western Union Company is a financial services and communications company based in the United States. Its North American headquarters is in Englewood, Colorado. Up until 2006, Western Union was the best-known U.S...
central telegraph office in New York City had 20,000 wet cells, mostly primary zinc-copper type, in use.
Telecommunications
In the application of stationary battery systems for telecommunications equipment, the equipment is operated on DC power (typically 48 volts in a central office - main telephone switching center or remote office). During normal operation when utility power is available, the telecommunications (load) equipment is operated from the DC power supplied from the rectifierRectifier
A rectifier is an electrical device that converts alternating current , which periodically reverses direction, to direct current , which flows in only one direction. The process is known as rectification...
s, which also serve to maintain full charge on the battery systems. In the event of a utility failure, the load is supported from the battery until an emergency power source can be applied, such as a generator
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...
. The typical design of a battery in the telecommunications application is to provide DC power to the load equipment for a minimum of four hours if a generator is also installed at the site. If a generator is not installed at the site, the typical design of a battery system is to support the load equipment for eight hours. If a utility outage appears to be for an extended duration (such as during a hurricane or ice storm
Ice storm
An ice storm is a type of winter storm characterized by freezing rain, also known as a glaze event or in some parts of the United States as a silver thaw. The U.S. National Weather Service defines an ice storm as a storm which results in the accumulation of at least of ice on exposed surfaces...
) a mobile generator would be mobilized to a site (that does not have a generator installed) to recharge the battery system and support the site until utility power can be restored.
For outages longer than a few seconds, the batteries must continue to provide power until an emergency power source
Emergency power system
Emergency power systems are a type of system, which may include lighting, generators, fuel cells and other apparatus, to provide backup power resources in a crisis or when regular systems fail. They find uses in a wide variety of settings from residential homes to hospitals, scientific...
can be started. Facilities that have no emergency power source follow a written manual protocol that dictates an orderly shutdown of the highest electrical demand equipment to extend battery life, followed after a specified interval by a complete power-down before the batteries are exhausted. As mentioned earlier, the batteries most frequently provide power for a UPS during brief, transient electric utility outages lasting at most, seconds. When electric utility outages last over 15 seconds to one minute, the UPS or the Automatic Transfer Switch (ATS)
Transfer switch
A transfer switch is an electrical switch that reconnects electric power source from its primary source to a standby source. Switches may be manually or automatically operated...
recognizes this as a long duration power outage and signals an emergency power source to start. After the emergency power source is started and is allowed to stabilize, an Automatic Transfer Switch disconnects the facility from the electric utility and connects the emergency power source to provided replacement AC electricity to the facility, including the UPS. Once the emergency power source, such as a diesel engine-generator
Engine-generator
An engine-generator is the combination of an electrical generator and an engine mounted together to form a single piece of equipment. This combination is also called an engine-generator set or a gen-set...
(genset) or gas turbine
Gas turbine
A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....
coupled to a generator
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...
, is online, the UPS ceases drawing power from the battery room, and recharging the batteries begins with DC power supplied by the UPS or a free-standing battery charger. After electric utility power is restored, the batteries are again called on to supply power during the very brief period while the Automatic Transfer Switch disconnects the emergency power source and reconnects the electric utility. Recharging the batteries can add considerable additional load to the emergency power source, potentially overloading it. To avoid this, most UPS systems large enough to require a battery room have, as part of their electronic controls, a signal wire from the Automatic Transfer Switch that the ATS energizes when emergency power is active. When this signal wire is energized, the UPS recharges the batteries at a preselected reduced rate. When electric utility power is restored, full rate recharging resumes.
The interval the battery room provides electric power is known as ride-through, and a battery room is rated by the maximum amount of ride-through time it can provide at maximum rated load. An approximately reciprocal relationship exists between the ride-through time and the electrical load on the batteries. Thus, a battery room rated to provide 15 minutes of ride-through while delivering a maximum 900 amperes at 48 volts will provide more than 30 minutes of ride-through if the actual demand is only 450 amperes. The total capacity (product of current and time, or ampere-hour
Ampere-hour
An ampere-hour or amp-hour is a unit of electric charge, with sub-units milliampere-hour and milliampere second...
s) increases at lower current discharge rates, an effect called Peukert's law
Peukert's law
Peukert's law, presented by the German scientist W. Peukert in 1897, expresses the capacity of a lead–acid battery in terms of the rate at which it is discharged. As the rate increases, the battery's available capacity decreases....
.
The type of battery most commonly employed in battery rooms is the flooded lead-acid battery
Lead-acid battery
Lead–acid batteries, invented in 1859 by French physicist Gaston Planté, are the oldest type of rechargeable battery. Despite having a very low energy-to-weight ratio and a low energy-to-volume ratio, their ability to supply high surge currents means that the cells maintain a relatively large...
. Batteries are installed in groups. Several batteries are wired together in a series circuit forming a group providing DC electric power at 12, 24, 48 or 60 volts (or higher). Usually there are two or more groups of series-connected batteries. These groups of batteries are connected in a parallel circuit. This arrangement allows an individual group of batteries to be taken offline for service or replacement without compromising the availability of uninterruptible power. Generally, the larger the battery room's electrical capacity, the larger the size of each individual battery and the higher the room's DC voltage.
Electrical utilities
Battery rooms are also found in electric power plants and substationElectrical substation
A substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions...
s where reliable power is required for operation of switchgear
Circuit breaker
A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow...
, critical standby systems, and possibly black start
Black start
A black start is the process of restoring a power station to operation without relying on the external electric power transmission network.Normally, the electric power used within the plant is provided from the station's own generators...
of the station. Often batteries for large switchgear line-ups are 125 V or 250 V nominal systems, and feature redundant battery chargers with independent power sources. Separate battery rooms may be provided to protect against loss of the station due to a fire in a battery bank. For stations that are capable of black start, power from the battery system may be required for many purposes including switchgear operations.
The world's largest battery is in Fairbanks, Alaska
Fairbanks, Alaska
Fairbanks is a home rule city in and the borough seat of the Fairbanks North Star Borough in the U.S. state of Alaska.Fairbanks is the largest city in the Interior region of Alaska, and second largest in the state behind Anchorage...
, composed of Ni-Cd
Nickel-cadmium battery
The nickel–cadmium battery ' is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes....
cells. Sodium-sulfur batteries
Sodium-sulfur battery
A sodium–sulfur battery or liquid metal battery is a type of molten metal battery constructed from sodium and sulfur . This type of battery has a high energy density, high efficiency of charge/discharge and long cycle life, and is fabricated from inexpensive materials...
are being used to store wind power
Wind power
Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electricity, windmills for mechanical power, windpumps for water pumping or drainage, or sails to propel ships....
.
Submarines and ocean going vessels
Battery rooms are found on submarineSubmarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...
s of the diesel-electric type, where they contain the batteries used for undersea propulsion of the vessel. Even nuclear submarines contain large battery rooms as backups to provide maneuvering power if the nuclear reactor is shutdown. Batteries in surface vessels may also be contained in a battery room.
Battery rooms on ocean-going vessels must prevent mixture of seawater with acid, since this will produce toxic hydrogen chloride
Hydrogen chloride
The compound hydrogen chloride has the formula HCl. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric humidity. Hydrogen chloride gas and hydrochloric acid are important in technology and industry...
gas. This is of particular concern on submarines.
Design issues
Since typical secondary batteries may give off hydrogenHydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
gas especially if overcharged, ventilation of a battery room is critical to maintain the concentration below the lower explosive limit.
The life span of secondary batteries is reduced at high temperature and the energy storage capacity is reduced at low temperature, so a battery room must have heating or cooling to maintain the proper temperature.
Batteries may contain large quantities of corrosive electrolyte
Electrolyte
In chemistry, an electrolyte is any substance containing free ions that make the substance electrically conductive. The most typical electrolyte is an ionic solution, but molten electrolytes and solid electrolytes are also possible....
s such as sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
used in lead-acid batteries or potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
used in nickel-cadmium batteries. Materials of the battery room must resist corrosion and contain any accidental spills. Plant personnel must be protected from spilled electrolyte. In some jurisdictions, large battery systems may contain reportable amounts of sulfuric acid, a concern for fire departments. Battery rooms in industrial and utility installations typically have an eye-wash station nearby, so that workers who are accidentally splashed with electrolyte can immediately wash it away from the eyes.