Glossary

The chemical paste that adheres to the positive (+) and negative (-) electrodes in a battery and reacts with sulfuric acid.

The negative electrode. It is the part of a battery that oxidizes and sends electrons to the cathode (the positive electrode) on discharge.

Electrochemical cell, or cells, connected in series (some in parallel); composed of the anode (negative electrode), cathode (positive electrode), separator and electrolyte as catalyst.

One or more cells connected electrically in series or parallel, or both, to provide the required operating voltage and current levels*. As discussed in chapter 2, large UPS batteries typically consist of hundreds of cells. 

A complete system of parallel connected strings.

Battery chemistry is the combination of chemicals from which the battery cathode, anode, and electrolyte are constructed. Battery chemistry radically impacts battery characteristics and performance.

Eurpoean legislation on waste batteries tp protect the environment

A measure of battery performance and longevity, which can be quantified in several ways: as run time on a full charge (service life), as estimated by a manufacturer in ampere hours (design life), or as the number of cycles until the end of useful service (cycle life). 

An open structure used to support a group of cells or multi-cell units*. 

A portion of a building or facility with controlled walk-in access, physically set off from the rest of the building by walls, the primary purpose of which is to house a stationary battery or batteries*. 31

A series connection of individual battery cells or blocks to achieve the DC voltage required by the UPS DC bus.

A group of cells packaged as a single unit, common in VRLA and VLA batteries used in UPS systems.

One or more cells in a container also known as a battery. The terms block and jar are interchangeable. For this manual the term has been standardised as block to avoid using the somewhat unwieldy convention of "block/jar" throughout.

The period from the initiation of charging to the onset of gassing, during which charge is retuned to a battery at high efficiency*.   

The total amount of electrochemical energy a battery can store and deliver to an external circuit.  It is normally expressed in terms of Ah or runtime at a desired discharge rate.

An agent introduced into the headspace of a VRLA cell to mitigate the effect of self-discharge of the negative electrode, thereby reducing dry out and extending the life of the cell. 

A positive electrode made of a material that is electrochemically reduced and receives electrons from the anode (the negative electrode) on discharge in an electrochemical reaction that supp-lies electrons (i.e., electricity) to an external circuit.

The basic electrochemical building block of a battery, characterised by a positive electrode, a negative electrode, and electrolyte*, encased in a container. A cell can be a stand-alone unit (typically two volts nominal) or a multi-cell unit (typically six or twelve volts nominal).    

The basic electrochemical unit that can receive, store, and deliver electrical energy.

The smallest electrochemical unit in a battery system, particularly relevant for lithium-ion and NiCd technologies.

The conversion of electrical energy into chemical energy within a secondary cell*.   

The ability of a battery to conduct current. (see internal ohmic measurement) 

The electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of the material and its properties. The positive lead grids in a battery gradually corrode in service often leading to battery failure. Battery terminals are also subject to corrosion if they are not properly maintained.

Also called faradaic efficency or current efficiency describes the charge efficiency by which electrons are transferred in a battery

In a battery, one discharge plus one recharge equals one cycle.

(See battery life) 

The count of total cycles for a given standard test profile, measured until the battery is unable to meet minimum test criteria (e.g. discharge voltage or current)  Different standardized tests have different sized cycles and testing parameters depending upon the type of battery.  Results are not directly comparable.

Batteries designed to be regyularly dischraged (up to 8-% of more) and recharged, making them suitable for active storage systems e.g. solar power systems, electric vehicles, off-grid power etc.

(See battery life) 

Basic electrochemical battery with no electronic intelligence with which to communicate

The operating regime of a cell or battery including factors such as charge and discharge rate, depth of discharge, cycle length, and length of time in the standby mode.

The combination of active material that electrochemically stores and releases energy and a conducting substrate that supports or contains the material and allows useful electrical energy to flow to an external circuit.

The aqueous or non-aqueous medium that provides the ion-transport mechanism between the positive and negative electrodes of a cell*. In a lead-acid cell, the electrolyte is a solution of water and sulfuric acid, the concentration of which is known as specific gravity. 

Also known as volumetric energy density; specifies the amount of energy a cell can hold in volume (Wh/l). Energy density is synonymous with the runtime of a battery.

A charge, at a level higher than the normal float voltage, applied for a limited period of time, to correct inequalities of voltage, specific gravity, or state of charge that may have developed between the cells during service*.  

A constant-voltage charge applied to a battery to maintain it in a fully charged condition, while minimising degradation or water consumption. 

A slang term used to identify a vented cell or battery, in which the electrodes are immersed in free-flowing liquid electrolyte. 

Flow batteries (or redox flow batteries) are rechargeable batteries that store energy in liquid electrolytes held in external tanks, with electrolyte pumped through a cell stack for energy conversion. Suitable for large scale energy storage as their energy capacity is not limited by the cells physical size, offering flexibility and long life.

The output of hydrogen and oxygen gasses from the respective negative and positive electrodes during the final phase of charging, created from the decomposition of water in the electrolyte.

Electrolyte that has been immobilized by the addition of a chemical agent, normally fine silica, to prevent spillage and allow gas recombination. Batteries made with gelled electrolyte are often referred to as Gel batteries. Gel batteries are one type of VRLA batteries.

A lead alloy framework that supports the active material of a battery plate and conducts current generated by the active materials to an external connector.

An electrically conductive bar or cable used to connect adjacent cells in a battery*. 

Lead structures that connect adjoining battery cells in series, the positive of one cell to the negative of the next.

A non-continuous charging regime based on the following: (1) availability of the charging source; or (2) application of the charge by a permanently powered source*. 

The crystallized material that is deposited in each lead-acid battery electrode as a result of discharge of the charged lead materials in the electrodes and sulfuric acid within the electrolyte.

A secondary cell in which the active material of the positive electrode is lead dioxide, the active material of the negative electrode is lead, and the electrolyte is dilute sulfuric acid*. 

Soft, silver-white metal belonging to the alkali metal group; lightest and least dense metal in the element family; discovered by Johan August Arfwedson in 1817; metal is named after the Greek word “lithos” meaning “stone.”

A sealed rechargeable battery that uses various cathode and anode materials and lithium ions as the primary ionic conductor in an organic electrolyte.

A high-energy-density battery chemistry requiring fast sampling, thermal monitoring, and advanced safety controls due to higher thermal and electrical risk profiles.

Rechargeable battery with cobalt, manganese, nickel and/or other metals as the cathode and a graphite anode

Some cell chemistries (like Ni/Cd) require the cell to be fully discharged before being recharged in order to maintain their discharge capacities. If this is not done, the capacity from cycle to cycle diminishes fairly rapidly.

A term used to describe a single housing containing individual and connected battery cells.

Multiple cells in a single container*. 

A battery chemistry tolerant of wide temperature ranges and deep discharge, often used in harsh environments or industrial facilities.

A secondary cell in which the active material of the positive electrode is nickel oxyhydroxide, the active material of the negative electrode is cadmium, and the electrolyte is a dilute solution of potassium hydroxide*. 

The value assigned to a battery of a given voltage class for the purpose of convenient designation. The operating voltage of the system may vary above or below this value*. 32

Batteries designed tp remain charged and only discharge during power outages or emergencies.

A continued excess charging of a fully charged battery or, conversely, the excess discharging of a fully discharged battery. A lead-acid battery requires more charge than discharge due to inefficiencies, but excessive overcharge is abusive and leads to damage.  Over-discharge generally refers continuing discharge passed a cutoff voltage limit and can also lead to damage.

Multiple battery strings connected in parallel to increase available current capacity and runtime.

The interconnection of two or more strings in which the like terminals of each battery string are connected together* to increase the available power without changing voltage. 

Thin, flat structures comprised of a lead conductive grid and active material. The grid supports the active material and conducts electrons out of the cell. Plates are either positive or negative, depending on the active material they hold.

Designating, or pertaining to, a kind of electrical potential; opposite of negative. A point or terminal on a battery having the higher relative electrical potential. The positive battery terminal is the point to which electrons flow during discharge.

The formation of compounds on a post that can affect connection quality, and in extreme cases can result in failure of a post or post-to-cover seal and cracking of a cover or container*.   

Electrical circuit built into a battery pack to ensure safety under all operational/ environmental circumstances; preventing abuses such as excessive current, operation at extreme temperatures, overcharge and overdischarge.

An open structure, typically in a battery room, used to support a group of cells/units. 

The capacity assigned to a cell by its manufacturer for a given discharge rate, at a specified electrolyte temperature, to a given end-of-discharge voltage*. 

A feature of VRLA cells in which oxygen generated at the positive plates is ultimately recombined with hydrogen ions at the negative plates and converted back into water. In this process, hydrogen gas formation and evolution are suppressed. 

American way of measuring battery capacity by applying a fixed discharge current and measuring time in minutes. The EU uses the ampere-hour (Ah) method under DIN and IEC.

Remaining battery capacity before charge

The length of time a battery provides power with a charge

The generation or conversion of the normal lead sulfate discharge crystals in the plates to a state that resists recharge. Sulfation often develops when a battery is stored or cycled in a partially discharged state at warm temperatures. It is a vague term for low charge acceptance in a discharged condition with no quantitative measurement.

 A battery that does not have accessible vent caps or a VRLA (valve regulated lead-acid battery).

A cell that is designed not to allow release of gas or electrolyte during normal operation*. 

Another term for a valve-regulated lead-acid cell, derived from the characteristic of VRLA in which electrolyte can be neither added nor removed under conditions of normal operation; also considers that the safety pressure valve is closed to prevent escape of gas under conditions of normal operation. 

An electrochemical cell that is capable of being recharged following discharge*. 

Internal chemical reactions taking place within the electrodes that result in a loss in stored charge.

A porous membrane divider between the positive and negative plates in a cell that allows the flow of ionic current to pass through it, but not electronic current. Separators are made from numerous porous materials impervious to electrolyte and oxidation such as: polyethylene-silica, glass fiber, porous rubber, PVC, phenolic cellulose, etc.

(See battery life) The period of useful operation under specified conditions. 

The length of time a batter can be used in a given application

The normal operating period of time for a battery in an application until it no longer satisfies the minimum application requirements.

An unintended current bypass in an electrical device or wiring. Outside a battery a short circuit is established when an unintended conductive path is established between the two terminals of a battery. Inside a battery, a cell short circuit is the result of contact between the positive and negative plates that will cause a cell to discharge and render the battery useless.

Starting, Lighiting and Ignition battery. A battery primarily used to start a vehicle and to provide power for lights and accessories. SLI batteries include automotive, deep-cycle and heavy-duty commercial starting batteries.

A Smart Battery is a rechargeable battery pack incorporating a Battery Management System (BMS) with an external communication data bus (usually a 2-wire system called SMBus). The BMS protects the battery from operating outside its safe limits by monitoring key cell parameters (current, voltage, temperature, cycle count, state of charge, etc.) in a single or multi-cell pack, performing cell balancing to ensure optimum performance, battery authentication, as well as external communication of the battery health data with a smart charger and/or host device through the SMBus.

An advanced battery type that replaces the flammable liquid electrolyte in traditional Li-ion batteries with a solid material, offering higher energy density, faster charging, longer life and improved safety.

The ratio of the mass of a given volume of electrolyte to the mass of an equal volume of water at a specified temperature*. Specific gravity options are often available for vented lead-acid batteries; the specific gravity of VRLA batteries is usually fixed. 

Standby batteries provide backup power, staying fully charged until a primary power failure, at which point they instantly supply energy for critical functions like emergency lighting, alarms or uninteruptible power supply systems (UPS) to prevent disruption. Unlike batteries designed for continuous cycling, they are designed for infrequent, short sharp discharges.

Fixed energy storage systems designed for long-term, reliable power in permanent locations, they provide continuous power for applications like uninteruptible power sully systems (UPS), solar engery backup, grid stabilisation, often operating in a charge state ready for dischrage during outages or to balance energy supply and demand.

A battery designed for service in a permanent location*. 

The unequal concentration of electrolyte due to density gradients from the bottom to the top of a cell. This condition is encountered most often in batteries recharged from a deep discharge at constant voltage without a great deal of gassing for mixing wherein recharged higher concentration sulfuric acid sinks to the bottom of the cell. Continued deep cycling of a ‘stratified’ battery will result in softening of the bottoms of the positive plates and sulfation of the bottoms of the negative plates. Equalization charging is a way to avoid acid electrolyte stratification.

Two or more blocks connected in series

A grouping of interconnected cells that has the same nominal voltage as the dc system*. A UPS battery might have a single string or parallel strings. 33  

The electrical structures on the battery to which the external circuit is connected. Typically, batteries have either top-terminals (posts) or side-terminals. Some batteries have both types of terminals (dual-terminal).

A single container. This term is usually preceded by “single-cell” or “multi-cell”. 

A lead-acid cell that is sealed with the exception of a valve that opens to the atmosphere when the internal pressure in the cell exceeds atmospheric pressure by a preselected amount. VRLA cells provide a means for recombination of internally generated oxygen and the suppression of hydrogen gas evolution to limit water consumption*. 

A lead-acid cell in which the products of electrolysis and evaporation are allowed to escape to the atmosphere as they are created, also referred to as a “flooded cell”.

A flooded lead-acid battery with long service life, often used in legacy or high-reliability installations requiring regular maintenance.

A sealed lead-acid battery type widely used in data centres due to low maintenance requirements and predictable performance under float charge conditions.

The process of monitoring and controlling rechargeable batteries to ensure safety, optiomise performance and maximise lifespan

A system that not only monitors battery parameters but actively manages battery behaviour through charge control, equalisation, protection thresholds, and life-extension logic; more common in lithium and advanced lead-acid systems.

Electrochemical cell, or cells, connected in series (some in parallel); composed of the anode (negative electrode), cathode (positive electrode), separator and electrolyte as catalyst.

An electronic sensing system containing a program that monitors battery condition, performance and health that can be used by the application to make system decisions.

The process (either manually or through the application of a BMS) of altering individual cell voltage and state of charge through the distribution of charge current to produce uniform cells. This process can help improve the battery’s performance, safety, and longevity.

Battery chemistry is the combination of chemicals from which the battery cathode, anode, and electrolyte are constructed. Battery chemistry radically impacts battery characteristics and performance.

A discharge when a relatively large portion of the battery capacity, for a given rate of discharge, is removed.  Typically the voltage cutoff is 1.75 VPC to avoid cell reversal. Deep cycle batteries are designed to be repeatedly deep discharged without significant damage.

When a battery is delivering current, it is said to be discharging.

A controlled charging process used to balance battery voltages and extend service life.

A constant voltage charging method intended for extended periods of time in which the voltage set point is lowered and optimized for low water loss and reduced grid corrosion while maintaining the battery at a full state of charge.

The temperature at which a battery operates. The battery will operate effectively within a specified temperature range which varies based on the battery’s function and application purposes. If the battery is used outside of this range, the application may fail prematurely.

This is a phenomenon where a protective layer forms on the surface of an electrode upon initial contact with the electrolyte upon assembly. After an initial passivation layer is formed, the process slows down considerably and prevents further reaction on the electrode surface and thereby extends the shelf life of the battery (cell). This is an important characteristic of Lithium cells.

Maintenance that is regularly performed on a battery to lessen the likelihood of it failing, usually performed while the battery is connected. 

Planned maintenance activities guided by monitoring data rather than fixed time intervals.

Variation of intermittent charging in which the charger switches on and off several times per minute (or per second). 

During extended storage, cells will slowly lose some of their capacity (energy) due to internal chemical reactions to the chemistry. This affects shelf-life.

The adjustment of charging voltage with respect to temperature, normally accomplished using a slope or step function*, to prevent thermal runaway.

Battery life dramatically shortens when operated at extreme high or low temperatures. High temperatures increase internal cell pressure, which can result in leaks or other cell integrity issues. Low temperatures can increase internal resistance which produces heat. This heat can cause the electrolyte to evaporate in a non-hermetic system, hence reduces capacity.

A technique used to describe maintaining the charge level of a battery by charging with a small current either through float charging (which is constant voltage) or a small constant current charge.

Also known as maintenance charge, compensates self-discharge of a battery

An abnormally low voltage, below the expected value, during the discharge of a battery. Sometimes seen in extremely low temperatures (typically < - 20°C).

Time delay for a battery to deliver the required operating voltage after it is placed under load. Typically a voltage depression followed by a recovery will be observed when this phenomenon is present.

Battery thresholds on charge and discharge

Current is allowed to fluctuate in saturation while the voltage is capped (lead-acid and Li-ion charging)

Applying a momentary current pulse to a battery to evaporate a short.

A predefined parameter limit that triggers alerts when exceeded.

A lower-severity alert indicating abnormal conditions requiring investigation but not immediate action.

The amlount oif water vapour in the surrounding air.

The surrounding air temperature of the battery environment, used to assess HVAC adequacy and thermal stress risks.

The capacity assigned to a cell by its manufacturer for a given constant-current discharge, at a specified electrolyte temperature, to a given end-of-discharge voltage, for a specified duration. 

Absolute state-of-charge; ability to take specified charge when the battery is new.

 Absolute state-of-health; ability to store specified energy when the battery is new.

The process of continuously tracking a battery's health and performance, using sensors to measure key parameters to provide real-time data, estimate charge (SoC), health (SoH) enabling proactive battery management to optimse battery performance and longevity

Application software providing dashboards, alarms, trending, and reporting for battery systems.

A permanently installed system for measuring, storing and reporting battery operating parameters*.   

A system that continuously measures electrical and environmental parameters of UPS standby batteries (voltage, impedance, temperature, current, ripple) to detect degradation, predict failures, and support operational decisions in mission-critical facilities.

The difference in temperature between individual cells or battery blocks (monoblocks) within a single series-connected battery string. Maintaining uniformity in battery temperature is crucial because uneven temperatures lead to premature aging, capacity loss and increased risk of themal runaway.

The difference in float voltage measurements among individual blocks (monoblocks) within a single series-connected string. In standby (UPS) systems batteries are continuously charged to maintain full capacity. Ideally each block should receive an equal share of the total charger voltage, but variations occur due to internal resistance differences, temperature, or degradation. A key indicator of battery health. Large variations lead to poorer battery performance, reduced capacity and accelerated degradation of the entire string, as weak cells are over worked.

The gradual reduction in usable energy storage capacity as a battery ages or experiences adverse operating conditions.

Closed circuit voltage, measured when a battery or cell is under a load from an external source.

The central processing unit that timestamps, stores, analyses, and communicates battery data to software platforms.

An alert indicating conditions likely to result in imminent battery or system failure.

The electrical current flowing into or out of a battery string, critical for identifying load sharing, charger performance, and abnormal conditions.

Critical high accuracy measurement devices that convert the electrical cuyrrent flowing in and out of a battery string (charging or discharging) into a proportional, low voltage, or low current standatrdised analog signal. These devices provide critical data on battery health by monitoring float current, charging rates, and discahrge rates without causing significant power loss or interference with the circuit.

The duration for which historical battery data is stored for analysis and compliance.

Post-event analysis of real-world battery discharge behaviour during utility outages.

Also known as impedance spectroscopy; method to test electrochemical characteristics of a battery; EIS injects AC signals at different frequencies and analyzes the response.

The stage at which the battery meets specific failure criteria (e.g., capacity and/or power degradation). Specifically, when either: the net delivered capacity of a cell, module, or battery is less than 80% of its rated capacity when measured on the RPT (Reference Performance Test); or the peak power capability (determined using the Peak Power Test) is less than 80% of the rated power at 80% DOD.

Number of events in a given time. Indicates how often a battery monitoring system samples each type of battery data it collects 

As applied to battery operating temperature, the sustained temperature at which the expected service life of a battery is reduced by 50%. 

A data aggregation device collecting measurements from multiple sensors within a battery string or rack.

Device to measure the specific gravity of a fluid; reads state-of-charge of a lead acid and other flooded batteries.

A measure of the opposition to an alternating current; a combination of internal resistance and reactance. [See also:  internal ohmic measurement] 

The rate at which internal resistance increases over time, used for predictive maintenance modelling.

Long-term analysis of impedance changes to predict end-of-life well before functional failure occurs.

A measurement of the electronic and ionic conduction paths within a cell or unit, expressed in terms of conductance, impedance, resistance, or admittance*. 

The resistance within a cell or battery that causes a drop in the source voltage when there is a current. (See internal ohmic measurement) 

A key health indicator representing opposition to current flow within a battery; increasing impedance correlates strongly with ageing and impending failure.

A controlled discharge test used to verify actual battery capacity under load.

Ripple Current,AC current superimposed on DC charging current, typically originating from UPS rectifiers and capable of accelerating battery degradation.

The precisionwith which a battery monitoring system measures the internal resistance, impedance, or conductance of a battery cell or unit to estimate state of health )SoH) and detect degradation.

Often referred to as internal ohmic measurement - the specific measurement of a cells internal resitance, impedance, or conductance to assess its health and predict its remaining lifespan without the need to perform a full, invasive discharge test. As a battery ages and degrades, its internal components (plates, grids, electrolyte) break dow, causing the ohmic resistance to increase, which correlates directly to a decrease in capacity.

The precision, sensistivity, and fineness of measurement scale used to quantify the internal resistance, impedance, or conductance of a battery cell. It defgines how small a change in the internal ohmic value a battery monitoring system can detect.

(See internal ohmic measurement) 

An electric resistance measured in Ohms, typically associated with components or materials that maintain a constant resistance regardless of applied voltage. Meaning they follow Ohm's Law (V = IR)

Ohmic variation describes how a components resistance changes with voltage, current or temperature. In battery monitoring, Ohmic variation refers to the change/increase in the internal resistance (impedance, conductance or resistance) of a battery cell over time, which directly correlates to a reduction in its capacity to deliver power.

Voltage measurement where the battery or cell is under no load from an external source.

A constant-current or constant-power discharge capacity test, made on a battery after being in service*. 

The practice of systematically checking, recording and analysing key battery parameters at set intervals. Provides a static partial view of dynamic systems and lacks real-time visibility required to catch and respond to rapid battery changes/failures.

Calculates battery capacity on discharge rate; higher rates decrease capacity. Mainly used for lead acid batteries; a reading close to 1 indicates a battery with minimal loss; larger number reflect higher losses; named after Wilhelm Peukert (1897).

A remote sensor that can be used to measure string current and ambient temperature of the battery bank. mSensors can be connected to it so that they share the same communication cable from the PowerShield Controller.

A scalable enterprise battery monitoring platform form PowerShield, capable of monitoring VRLA, VLA, NiCd, and lithium-ion batteries across large multi-site data centre estates with high-resolution sampling, analytics, and system integration.

Data logger that periodically communicates with PowerShield Hubs and PowerShield mSensors to obtain system measurements. There are two versions of Controller: MX and LX

For large installations. Can monitor up to 8 strings and up to 512 blocks

A remote sensor that is connected to the blocks. It periodically measures the block voltage, ohmic value and temperature

For small to medium sized installations. Can monitor up to 4 strings and up to 200 blocks.

Conductive and capacitive resistance; frequency dependent

a key function declared by the battery monitoring/management system. A prediction of how many cycles the pack has before hitting the minimum requirements for operation.

Generic industry term for off-site visibility into battery system health across multiple locations.

The opposition to the free flow of direct current in a circuit or battery. Resistance (measured in units of ohms or milliohms) in batteries is a measure of the rapid change in voltage with respect to the rapid change in current.

A periodic waveform riding in the dc circuit, normally expressed as peak-to-peak, or root mean square (rms)*. Can refer to voltage or current. 

A small unwanted AC component that rides on top of a DC signal, often seen in power supplies after rectification, causing fluctuations and generating heat in components like capacitors and batteries..

A small unwanted AC fluctuation or variation that remains on a DC power supply's output, caused by imperfrect conversion from AC to DC and appearing as a ripple on an otherwise smooth DC waveform.

AC voltage fluctuations on the DC bus that contribute to heating and reduced battery life.

The frequency at which battery parameters are measured, critical for detecting fast-developing faults.

The ability of a monitoring system to grow with increasing battery count, power density, and site numbers.

A device installed at each battery block or cell to measure electrical and thermal parameters with high accuracy.

Any component whose failure would result in loss of critical power functionality.

Specific Gravity is a measure of the sulfuric acid electrolyte concentration in a battery at a specific temperature. This measurement is based on the density of the electrolyte compared to the density of water and is typically determined by the use of a hydrometer (see Hydrometer). By definition, the specific gravity of water is 1.00 and the specific gravity of the sulfuric acid electrolyte in a typical fully charged lead-acid battery is 1.265-1.300. Specific gravity measurements are typically used to determine battery charge level or if the battery has a bad cell.

An estimate of the current available capacity of a battery expressed as a percentage of full charge.

The percentage of remaining discharge capacity or discharge time available in a battery under prevailing conditions of discharge compared to a fully charged battery under the same or defined conditions: SOC = 100% x Cremaining / Ccharged

The stored or remaining capacity in a battery expressed as a percentage of its fully-charged capacity/nominal capacity in Ah. 

A calculated indicator representing remaining usable battery life compared to its original condition.

A measure representing the present state of battery available capacity or remaining service life relative to rated capacity or specifications. (See battery life*) 

The cumulative DC voltage across a complete battery string, used to verify UPS compatibility and detect systemic issues.

The total electrical potential (voltage) of a group of individual battery cells or blocks connected together in series to achieve a specific, higher voltage required by a critical power system (UPS).

See string current

See string voltage

The temperature of individual cells or blocks, directly influencing battery life, capacity, and safety.

A condition that is caused by a battery charging current or other process, which produces more internal heat than the battery can dissipate*, potentially leading to fire in a short amount of time. 

A failure mode where increasing temperature accelerates internal reactions, potentially leading to fire or explosion, especially in lithium-ion systems.

An uncontrolled increase in battery internal temperature during a voltage-controlled charging process where the current rate increases as the battery temperature continues to rise causing the electrolyte to boil away.

Thermal runaway occurs in a battery when the rate of internal heat generation exceeds the rate at which the heat can be dissipated into the ambient environment. If the battery cannot dissipate the excess heat, its internal temperature will rise continuously which can cause the case of the battery to rupture.

Early identification of abnormal thermal and electrical behaviour that precedes a runaway event.

System-level logic and alerting designed to mitigate or respond to detected runaway risks.

(See thermal runaway) A variation of thermal runaway that occurs over a longer period of time and usually results in battery failure but not necessarily fire. 

The unit of measure for electrical potential.

An electromotive force or potential difference expressed in volts.

The DC electrical potential measured across an individual battery cell or block, used to identify imbalance, failure, or overcharge conditions.

The net difference in the electrical potential (voltage) when measured across a resistance or impedance (ohms) with applied current. See Ohm’s Law.

The upper and lower limits of electrical potential that indicate the health and state of charge (SoC) and the operational safety of a battery bank. Because a battery's interna;l resistance increases as its capaity decreases, accurate ohmic measurements allow for the identification of faulty cells, or the estimation of end-of-life before the battery fails under load.

The smallest chage or variation that a Battery monitoring system can detect and record.

Continuous monitoring required to meet battery manufacturer warranty conditions.

The unit for measuring electrical power, i.e., the rate of doing work, in moving electrons by, or against, an electrical potential. Formula: Watts = Amperes x Volts.

The unit of measure for electrical energy equivalent to a power consumption of one watt per for one hour.

Unit oif electrical energy equivalent to a power consumption of one watt for one hour. Multiplying the battery voltage (v) by the rated capacity (Ah) gives the energy in Wh.

International safety requirements for battery installations.

A standard defining maintenance, testing, and replacement practices for VRLA batteries.

A standard covering maintenance practices for flooded lead-acid batteries.

The Institute of Electrical and Electronic Engineers, advancing technology through setting global standards

International Electrotechnical Commission, develops and publishes international standards for elctrical, elctronic and related technologies like energy storage.

The international standard for Occupational Health & Safety (OH&S) Management Systems, providing a framework for oganisations to proactively manage risks, prevent work-related injuries and illnesses, and create safer, healthier worplaces for employees and vistors.

The international standard for Quality Management Systems (QMS), providing a framework to consistently meet customer and regulatory requirements, improve efficency and enhance customer staisfaction through effective processes and continuous improvement.

Protective clothing, helmets, goggles, or other garments or equipment designed to protect the wearer’s body from injury or electric shock. Hazards addressed by battery PPE equipment can include physical, electrical, heat, chemicals, and airborne particulate matter, but not all at the same time. 

A hazard communication form (also known as a Material Safety Data Sheet [MSDS]), by which regulators require a battery manufacturer, importer, distributor, or integrator to identify each hazardous material present in a battery unit; typically readily accessible to anybody expected to perform maintenance on a battery system.      

Formal contracts between the data centre provider and clients that specify the expected standards for service delivery, including parameters such as uptime guarantees, response times for issue resolution, and maximum allowable downtime, ensuring clear expectations and accountability for performance and reliability.

Abbreviation of Underwriters Laboratories Inc. in USA. The UL establishes various safety standards, and performs official recognition of materials, aprts and products.

Safety acceptance test for lithium based batteries by Underwriters Laboratories. Other agencies are IEC 62133, IEEE 1625, IEEE 1725, BAJ, UN. In 2010, UL 1642 transitioned to IEC 62133.

Safety norms for shipping battery products

A dangerous condition associated with the possible release of energy caused by an electric arc. An arc flash (sometimes called flashover), is the light and heat produced as part of an arc fault, a type of electrical explosion or discharge that results from a low-impedance connection through air to ground or another voltage phase in an electrical system. An arc flash might also be accompanied by an arc blast, which is the supersonic shockwave produced when the uncontrolled arc vaporizes the metal conductors. 

A safety hazard associated with high DC fault currents in battery systems, mitigated through design, monitoring, and maintenance practices.

Battery Storage Energy System (also known as ESS)

A facility-level system that aggregates operational data from electrical, mechanical, and environmental subsystems.

The computer equipment and systems whose continuous operation is essential for business functions, typically supported by an uninterruptible power supply (UPS) to ensure consistent power and minimise downtime in case of power interruptions. Critical load is measured in watts (W) or kilowatts (kW), which quantify the amount of power required to keep essential computer equipment and systems operational.

A period of time when systems are unavailable due to failures or maintenance, impacting service continuity and potentially disrupting business operations and client access to critical data.

Agent to suppress fire. Used also for Li-ion fires.

Electrical power infrastructure designed to operate with near-zero tolerance for downtime, typically supporting data centres, hospitals, financial services, telecommunications, and defence facilities.

The duplication of critical infrastructure components and systems to ensure backup and protection against downtime caused by failures, thereby maintaining continuous operation and service availability.

Redundancy levels are defined relative to the baseline “N,” representing the minimum number of independent resources required for system operation. In an N+1 configuration, there is one additional backup resource; N+2 includes two backup resources; and 2N provides double the total resources available to the system.

A UPS system using kinetic energy storage (flywheels) combined with batteries or generators to provide short-term ride-through and power conditioning.

A solid-state UPS topology using rectifiers and inverters with battery energy storage, commonly used in modern data centres.

Critical power facilities often characterise their relaiblility by the number of nines in their uptime percentage, representing the maximum allowable downtime per year. Three nines 9.99% (( hours of downtime pa), Four nines 99.99% (52 minutes of downtime pa). Five nines 99.999% (<6 mnutres of downtime pa)

A battery-powered device that provides immediate backup power to a computer system or other equipment when the primary power source, such as the utility main, fails. It ensures an instant or near-instant continuation of electrical current, protecting against power interruptions and allowing for safe shutdowns or transitions to alternative power sources.

A power system that provides instantaneous backup power during utility outages or disturbances, supplying energy from batteries until generators stabilise or systems shut down safely.

The duration for which a UPS system can support critical loads solely from battery energy, typically expressed in minutes at a defined load percentage.

Occurs when a UPS system stops providing seamless backup power during an power outage leading to an aburpt shutdown, harcdware damage and potentially data loss; often the result of battery failure.

UPS Battery Plant,The complete battery installation supporting a UPS system, including battery strings, racks, cabling, monitoring hardware, and environmental controls.

The percentage of time that critical power systems are fully operational and providing continuous, high quality electricity to IT equipment or critical machinery without interuption. It is the inversion of downtime and serves as a key performance indicator (KPI) for reliability, often measured annually to quantify effectiveness of infrastructure, redundancy and maintenance strategies.

The highest standard of system availability, typically targeting "five nines" (99.999% or higher). Batteries are the 1 cause of UPS failure

The Uptime Institute is a global advisory organisation that sets industry standards for Tier Standards for data centers design, construction and operational sustainability

 The practice of housing multiple customers’ servers and other computing hardware within a single data centre facility, where each customer retains ownership of their equipment while sharing the facility’s infrastructure, such as power, cooling, and connectivity. 

 A facility that houses and manages computer systems, storage, and networking equipment to ensure the reliable operation and secure management of critical data and applications. 

 The delivery of off-site physical data centre facilities and infrastructure to clients, providing managed and scalable IT resources without the need for clients to own or maintain their own data centre infrastructure. 

 Software tools used to discover, monitor, and control the assets within a data centre, including both power and computing resources, to optimize operational efficiency and resource management. 

 Software used to manage and optimise data centre physical infrastructure including power, cooling, and environmental systems. 

 A data centre owned and operated by a private company, dedicated to processing internal data and hosting mission-critical applications, thereby supporting the organisation’s operational needs and ensuring data security and control. 

 A hybrid cloud integrates both public and private clouds, enabling organisations to run workloads on public cloud infrastructure for scalability and cost efficiency, while managing sensitive or critical workloads on private clouds for enhanced security and control. 

 A massive, highly scalable facility housing tens of thousands of servers. >10,000 sq ft in size with some reaching over 1.5m sq ft. Typically consumes 100- 300 megawatts (MW) of power. 

 Providing computer infrastructure—including virtualisation platforms, servers, software, data centre space, and network equipment—on a subscription basis, allowing clients to access and manage these resources as a fully outsourced service rather than investing in and maintaining their own hardware and infrastructure. 

 The central space in a data centre where the structured cabling system is distributed. It typically houses the Main Distribution Frame (MDF), which includes core routers, core switches, UPS power, cooling systems, and manages incoming telecommunications and internet wiring, distributing it to various Intermediate Distribution Frames (IDFs). 

 A cloud computing environment dedicated to a single organisation but hosted within a shared data centre infrastructure that serves multiple tenants, offering the benefits of privacy and customization while leveraging shared resources to optimize cost and efficiency. 

 A cloud computing environment exclusively dedicated to a single organisation, providing customisable and secure access to computing resources, storage, and applications, which can be hosted within the organisation’s own data centres or by a third-party provider’s data centre, tailored to meet the organisation’s specific needs and compliance requirements. 

 A computing environment where computing resources, such as servers, storage, and applications, are hosted and managed by third-party providers and made available to multiple organisations or individuals over the internet, offering scalability and cost-effectiveness without requiring users to manage the underlying infrastructure. 

 A Tier 1 data centre, as defined by the Uptime Institute’s tier classification system, is a basic server room that adheres to general guidelines for computer system installations, providing 99.671% availability. It operates with a single, non-redundant distribution path and non-redundant capacity components, offering minimal protection against disruptions and downtime. 

 A Tier 2 data centre, according to the Uptime Institute’s tier classification system, meets all the requirements of Tier I and offers an improved availability guarantee of 99.741%. It includes redundant site infrastructure capacity components, providing enhanced reliability and protection against disruptions compared to Tier 1. 

 A Tier 3 data centre, as defined by the Uptime Institute, builds on the requirements of Tiers 1 and 2 by offering dual-powered IT equipment connected to multiple independent distribution paths, ensuring an increased availability of 99.982%. This setup provides enhanced reliability and fault tolerance, allowing for maintenance and upgrades without interrupting operations. 

 A Tier 4 data centre, according to the Uptime Institute’s tier classification, incorporates all components from the previous tiers and adds independently dual-powered cooling systems. It features fault-tolerant infrastructure with redundant distribution paths and the capability to store electrical power, ensuring a high level of reliability with a guaranteed availability of 99.995%. 

 An electrical current that periodically reverses direction and changes its magnitude continuously with time, in contrast to direct current. A battery does not deliver alternating current. 

 The unit of measure of the electron flow rate, or current, through a circuit. 

 A daisy chain communication bus used between the PowerShield Controller and PowerShield Hubs or PowerShield mSensors 

 The ability to transmit current in a circuit or battery. It is the reciprocal of resistance and measured in Siemens. 

 Unit of electric charge. One coulomb (1C) equals one ampere-second (1As) 

 An electrical current flowing in an electrical circuit in one direction only. A secondary battery delivers direct current and must be recharged with direct current in the opposite direction of the discharge. 

 The reference zero potential of a circuit. 

 The opposition to the flow of a small alternating current in battery at a particular frequency combining resistance and reactance. Measured in ohms or milliohms. 

 The opposition to direct discharge current flow within a battery that causes a drop in battery voltage. Measured in ohms or milliohms. 

 Atom or molecule with unequal number of electrons and protons; provides a positive or negative electrical charge. 

Energy measurement: 1 joule = 1A at 1V for 1 second. Also applies to mechanical energy. 

An industrial communication protocol widely used for integrating electrical systems into BMS platforms. 

Designating, or pertaining to, a point of electrical potential. The negative battery terminal is the point from which electrons flow during discharge. 

 Electrical DC resistance with no capacitative or indictive reactance 

 A unit for measuring electrical resistance or impedance within an electrical circuit or battery. 

 Expresses the relationship between volts (V) and current (I) in an electrical circuit with resistance (R). It can be expressed as follows: Volts (V) = Amperes (I) x Ohms (R). 

Battery resistance measurement based on IEC 610951 (Cadex trademark) 

A web-based interface allowing programmatic access to battery monitoring data. 

 An unwanted electrical connection between negative and positive plates. A short circuit can damage the battery and any connecdted equipment as well as cause sparks and/or fire. 

 Simple Network Management Protocol used for alarm and status integration with IT monitoring platforms. 

 Bi-directional data port featuring a 5 volt supply and two data lines to accommodate auxiliary devices and to charge batteries 

 Electrical energy potential per unit of charge. IV = 1J/Coulomb.