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Battery Encyclopedia

Everything you want to know about batteries from A to Z, curated by TWAICE experts.

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Anode, cathode, state of health, depth of discharge, end of life - read about the most important battery terms and definitions.

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Electrolyte decompositon

Battery terminology

This term refers to the chemical deterioration of the electrolyte in a battery, often caused by factors like overcharging, excessive heat, or impurities. This breakdown can lead to reduced battery efficiency, gas generation, increased internal resistance, and a decrease in overall capacity. Preventing this is crucial for maintaining battery performance and safety.

Electrons

Battery cell

Electrons are negatively charged subatomic particles that play a key role in electricity. In the context of batteries and circuits, they are the carriers of electric current, moving from the negative to the positive terminal in a circuit.

Electrothermal

Battery modeling

Pertaining to the combined electrical and thermal properties or processes, often in the context of battery operation and management.

End of life (EoL)

Battery terminology

End of Life criteria is when the cell is retired from its (first) application, usually a State of health (SoH) of 80% or an increase of the ohmic resistance up to 200% is used for automotive applications. After automotive applications, there might be a second life in stationary applications with different EoL criteria (e.g. 50% SoH) possible.

A remaining capacity of 80% might seem as like an arbitrary choice for retiring the cell from its primary application but it might have its origins in rapid cell degradation going beyond this State of health of the cell. Above 80% of the remaining capacity, the capacity fading and resistance increase is generally observed in a quasi-linear way. After the 80% to 70% crossing, capacity fading and resistance increased behave in a more non-linear way, which makes longer term forecasts more challenging. While the above characteristic parameters have been defined for cells, they are also widely used for higher levels such as for modules, systems and batteries.

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Energy

Battery terminology

Energy is the total amount of work a lithium-ion battery can perform, usually measured in watt-hours (Wh). It is a product of the battery’s voltage and capacity, determining the duration for which a battery can power a device.

Energy Storage Management System (ESMS)

Energy storage

A system that manages and optimizes the charging, discharging, and overall performance of an energy storage system, ensuring safety, longevity, and efficient operation.

Energy density

Battery terminology

Energy density is the amount of energy a battery can store per unit volume (volumetric energy density) or weight (gravimetric energy density). Higher energy density batteries can store more energy in a smaller, lighter package, making them desirable for applications such as electric vehicles and portable electronics.

Energy integration

Energy storage

Energy integration involves combining various energy sources, including batteries, to create a cohesive and efficient energy system. This approach supports the stability and sustainability of the overall energy grid.

Equivalent Full Cycles (EFC)

Energy storage

An Equivalent Full Cycles (EFC) represents the amount of charge a battery has cycled relative to a full cycle. For example, a battery that charges from 50% to 100% State of Charge (SoC) and then discharges back to 50% has experienced 0.5 EFC.

FCR (Frequency Containment Reserve)

Energy storage

A reserve power service that helps maintain the stability of the electrical grid's frequency by quickly adjusting output.

Fast charging

Battery terminology

Fast charging refers to charging a battery at a higher current or voltage than standard charging rates, reducing the time required to reach a full charge. While fast charging can be convenient, it may generate more heat and stress the battery, potentially affecting its lifespan. There is no defined threshold for classification of fast charging. Some applications are deemed fast charging if full charging is performed within 30 mins, while others only call it fast charging if a full charge is done within 10 to 12 mins.

Fire Suppression System

Energy storage

A fire suppression system for battery energy storage systems (BESS) is a safety mechanism designed to detect and suppress fires, particularly those resulting from thermal runaway or internal cell failures. These systems may include clean agents, aerosol units, or water mist technologies and are often integrated with gas detection and early warning sensors. Fire suppression in BESS is essential for compliance with standards like UL 9540A, NFPA 855, and local fire codes.

Flow Battery

Battery cell chemistries

A type of rechargeable battery where energy is stored and released by chemical components dissolved in liquids contained within the system.

Frequency regulation/ control

Energy storage

Frequency regulation in the context of power systems refers to the maintenance of the constant frequency of the electrical grid (e.g., 60 Hz in North America or 50 Hz in Europe). This is crucial for the stability and reliability of the grid. Batteries, especially large-scale energy storage systems, can contribute to frequency regulation by quickly absorbing excess power when the frequency is too high or releasing power when the frequency is too low, thus helping to balance supply and demand in real-time.

Graphite

Battery cell

A form of carbon used as an electrode material in many batteries, known for its electrical conductivity and ability to intercalate lithium ions.

Grid Ancillary Services

Energy storage

Grid ancillary services are a set of technical functions and operational support mechanisms used by electricity grid operators to maintain the stable and reliable operation of the power grid. These services include frequency regulation, voltage control, reactive power support, spinning reserve, black start capability, and load following. Each service ensures that the supply and demand of electricity remain balanced in real time and that the grid infrastructure remains within its operating parameters. Ancillary services can be provided by power plants, battery energy storage systems (BESS), and demand response units, and they are essential components in both regulated and deregulated power markets.

Grid Operator

Energy storage

A grid operator is the entity responsible for the real-time coordination and operation of the electrical grid, ensuring a continuous balance between electricity supply and demand. Depending on the region, this can be a Transmission System Operator (TSO) or a Distribution System Operator (DSO). Grid operators maintain frequency, voltage, and system stability, dispatch generation units, and enforce compliance with grid codes.

Grid integration

Energy storage

Grid integration is the process of connecting battery systems to the electrical grid to enhance stability and efficiency. Batteries can store excess energy and supply it when demand is high, supporting renewable energy integration.

HVAC Component

Battery components

Parts of the Heating, Ventilation, and Air Conditioning system, significant for battery temperature management.

Heat-transfer-coefficients

Battery modeling

In the context of batteries, heat-transfer coefficients quantify how efficiently heat can be transferred away from the battery cells. High heat-transfer coefficients are desirable to efficiently dissipate heat and maintain optimal operating temperatures, thereby enhancing battery performance and lifespan.

Hybrid vehicle

Electric vehicles

A hybrid vehicle combines an internal combustion engine with an electric motor and battery system. This dual power system allows the vehicle to switch between or simultaneously use both power sources.

Hysteresis

Battery terminology

In the context of batteries, it refers to the different equilibrium potentials (difference in voltage between charging and discharging) at the same state of charge. The hysteresis effect can be very pronounced dependent upon the battery chemistry, requiring very accurate estimation or measurement of the terminal voltage.

IBR (Inverted Based Resources)

Battery terminology

Energy resources that use inverters to convert DC electricity to AC, enabling integration with the electrical grid.

IEC 60933

Energy storage

IEC 60933 does not apply to energy storage systems; it relates to printed board design. You likely meant IEC 62933, which is the series of international standards for electrical energy storage (EES) systems. IEC 62933 provides a comprehensive framework for performance, safety, testing, and grid integration of BESS and other energy storage technologies. It includes general principles, system guidelines, and testing protocols for safe and efficient deployment of energy storage in power systems.

IEC 62619

Energy storage

IEC 62619 is an international safety standard for rechargeable lithium battery cells and systems used in industrial environments, including stationary energy storage. It sets safety criteria for cell construction, system integration, abuse testing, and fault response. It is commonly used for BESS installations outside North America and aligns with international fire and safety practices.

ISOs

Energy storage

Independent system operator: Independent System Operators (ISOs) are organizations that manage regional electric grids and ensure reliable power delivery in the United States. They facilitate market operations and integration of new technologies, including battery storage.

Imbalanced Battery Cell

Battery terminology

A condition where cells in a battery pack exhibit varying states of charge, health, or voltage, affecting performance and longevity.

Impedance

Battery terminology

Contains information about the internal state of a battery and is composed of internal resistance and reactance, which are measured under defined conditions such as AC frequency, state of charge, state of health, and temperature.

Integrators

Energy storage

In the energy sector, integrators refer to systems or companies that combine various energy technologies and services to provide a comprehensive solution. This can include integrating renewable energy sources with traditional power systems, battery storage, and smart grid technologies to improve efficiency, reliability, and sustainability.

Intercalation of ions

Battery modeling

Intercalation of ions refers to the process where ions are inserted into the layers of a material without significantly altering its overall structure. This process is commonly seen in materials like graphite or layered metal oxides, where ions, such as lithium ions in the case of lithium-ion batteries, are reversibly inserted between the layers of the host material. The intercalation process is key to the functioning of various electrochemical systems, including rechargeable batteries, as it allows for the storage and release of energy.

Internal resistance

Battery terminology

Internal resistance in a battery refers to the amount of resistance that the battery's internal components, such as electrodes, electrolyte, and terminals, present to the flow of current within the battery. This resistance causes some of the electrical energy produced by the battery to be converted into heat, reducing the amount of available voltage and current that can be delivered to an external circuit.

Intraday Trading

Energy storage

Intraday Trading in energy markets involves buying and selling electricity within the same delivery day to respond to real-time fluctuations in supply and demand. Unlike day-ahead trading, intraday markets allow for continuous or auction-based trading closer to actual delivery time. This flexibility supports grid balancing, renewable integration, and portfolio optimization. Intraday trading is essential for managing forecast errors, especially for variable sources like wind and solar power.

Inverter

Battery components

An inverter converts direct current (DC) from batteries into alternating current (AC) and vice versa. One use case is to convert direct current from batteries into alternating current for use in homes, businesses, and the grid. Inverters are crucial for integrating battery systems with existing electrical infrastructure

Inverter imbalance

Battery terminology

"Inverter imbalance" refers to a condition where the output of an inverter (a device that converts direct current (DC) to alternating current (AC)) is not balanced across its phases. This typically occurs in three-phase inverters, where the voltages or currents in the three output phases (commonly denoted as A, B, and C) are not equal or not 120 degrees out of phase with each other as they should be in a perfectly balanced system.

Ion Transport

Battery modeling

In the context of batteries, ion transport refers to the movement of ions between the electrodes through the electrolyte. This process is fundamental to the operation of a battery, as it is essential for the flow of electric current and the storage and release of energy

Iron

Battery cell chemistries

Iron is a key component of the cathode of lithium iron phosphate (LiFePO₄) batteries, where it forms the cathode material. Lithium iron phosphate (LiFePO₄) is known for its thermal stability, safety, long cycle life, and relatively low cost, although it offers lower energy density compared to other cathode materials like lithium cobalt oxide or NMC (nickel manganese cobalt)

Joule

Battery terminology

The unit of energy in the International System of Units (SI), defined as the energy transferred when one ampere of current passes through a resistance of one ohm for one second.

Key Performance Indicator, KPI

Battery modeling

A Key Performance Indicator (KPI) in the context of batteries is a measurable value used to evaluate the performance and efficiency of a battery system. KPIs for batteries might include metrics such as energy density, cycle life, charge and discharge rates, efficiency, and capacity retention. These indicators help assess how well a battery performs under specific conditions and guide improvements in battery technology.

LCO (Lithium Cobalt Oxide)

Battery cell chemistries

LCO is a widely used lithium-ion battery cathode chemistry known for its high energy density and good cycle life. It’s predominantly used in portable electronic devices such as smartphones, laptops, and cameras. It was the initial cell chemistry in the 1990s when Sony commercialized the Li-ion battery.

LFP (Lithium Iron Phosphate)

Battery cell chemistries

LFP is a lithium-ion battery cathode chemistry offering high thermal stability, long cycle life, and excellent safety features. It’s commonly used in electric vehicles, grid storage systems, and industrial applications.

LMFP (Lithium Ferro-Manganese Phosphate)

Battery cell chemistries

This is a type of cathode material used in lithium-ion batteries. It offers benefits like high thermal stability, safety, and a long cycle life, although it typically has a lower energy density compared to other cathode materials like NMC (Nickel Manganese Cobalt Oxide).

LMO (Lithium Manganese Oxide)

Battery cell chemistries

LMO is a lithium-ion battery cathode chemistry that provides high power output and good thermal stability. It’s used in power tools, electric bikes, and some electric vehicles.

LMT (Light means of transport)

Electric vehicles

Light Means of Transport (LMT) includes electric bicycles, scooters, and other small electric vehicles. LMTs offer sustainable mobility solutions for short-distance travel.

LTO (Lithium Titanate)

Battery cell chemistries

LTO is a lithium-ion battery anode chemistry known for its extremely fast charging capabilities, long cycle life, and high safety. It’s used in applications that require rapid charging and discharging, such as electric buses and grid storage.

Lithium

Battery cell chemistries

Lithium is a key component in both the cathode and anode of lithium-ion batteries. In the cathode, it is often found in compounds like lithium cobalt oxide (LiCoO₂), lithium iron phosphate (LiFePO₄), and lithium nickel manganese cobalt oxide (NMC). In the anode, lithium can be used in the form of lithium metal or intercalated in graphite. Lithium enhances the battery’s energy density, allowing for longer-lasting, lightweight, and efficient power storage.

Lithium plating

Battery terminology

Lithium plating is a phenomenon that occurs in lithium-ion batteries when lithium ions are deposited as metallic lithium onto the anode (typically made of graphite) instead of being intercalated or inserted between the anode’s carbon layers.

This usually occurs under specific conditions like fast charging, charging at low temperatures, or when the cell is already at a high state of charge. Over time, this can create dendritic structures that may penetrate the separator, posing a risk of short-circuiting the battery. This not only reduces the battery’s life but also increases safety risks, as internal shorts can lead to thermal runaway and potential fires or explosions.

Lithium-ion battery

Battery cell chemistries

A type of rechargeable battery in which lithium ions move from the negative electrode (anode) to the positive electrode (cathode) during discharging and back again during charging .They are commonly used in mobile phones, laptops, electric vehicles, and grid-scale energy storage due to their comparatively high energy density and lightweight characteristics.

Load Profile (BESS)

Energy storage

A load profile for a Battery Energy Storage System (BESS) represents the pattern of power usage and charging/discharging cycles over time. It illustrates the operational behavior of the BESS in response to energy demand, market signals, or control algorithms. Accurate load profiling is critical for system design, financial modeling, and performance forecasting. It helps in determining optimal capacity, degradation rates, and energy throughput, and plays a vital role in battery sizing and lifecycle management.

Long-Term Service Agreement (LTSA)

Energy storage

A Long-Term Service Agreement (LTSA) is a contractual arrangement between an asset owner and a service provider that ensures ongoing maintenance, operational support, and performance management over a defined multi-year period—typically between 5 and 20 years. In the context of Battery Energy Storage Systems (BESS), LTSAs cover preventative maintenance, spare parts supply, performance guarantees, remote monitoring, and corrective actions. These agreements are crucial for asset longevity, reducing operational risk, and stabilizing life-cycle costs. LTSAs often include key performance indicators, availability guarantees, and financial incentives tied to system uptime and performance targets.

Loss of active anode material (LAMne)

Battery terminology

LAMne describes the degradation or consumption of the active material within the anode of a battery. For many lithium-ion batteries, graphite is the primary active material in the anode. Its layered structure allows for the intercalation of lithium ions. The loss of active anode material directly impacts the battery's capacity and overall cycle life. As the graphite is consumed, the battery's ability to store energy diminishes, leading to a decrease in its overall performance and efficiency.

Loss of active cathode material (LAMpe)

Battery terminology

LAMpe describes the degradation or consumption of the active material within the cathode of a battery. Several materials are used as active cathode materials in lithium-ion batteries. Common examples include Lithium Cobalt Oxide (LCO), Lithium Iron Phosphate (LFP), and Lithium Nickel Manganese Cobalt Oxide (NMC). The loss of active cathode material results in reduced energy storage capacity of the battery. As these materials degrade, the overall energy density of the battery diminishes, leading to shorter usable battery life and decreased performance.

Loss of electrical contact

Battery terminology

In battery cells, this refers to the disruption of the electrical connection within the cell, which can occur due to various reasons such as physical degradation of electrode materials, breakdown of the conductive network, or mechanical stresses. This loss impedes the efficient flow of electrons, crucial for battery operation, leading to reduced performance, efficiency, and sometimes complete failure of the battery cell.

Loss of lithium inventory (LLI)

Battery terminology

Refers to the irreversible loss of lithium ions in a battery, which can result from side reactions such as the formation of the solid-electrolyte interphase. This loss leads to a reduction of the overall capacity of a battery.

MISO

Energy storage

MISO (Midcontinent Independent System Operator) oversees the electric grid and market across multiple states in the central United States. It ensures grid reliability and facilitates the incorporation of energy storage solutions.

Machine learning model

Battery modeling

A machine learning model is an algorithmic structure that, based on input data, makes predictions or decisions, identifying patterns or making decisions with minimal human intervention. These models can range from simple linear regression to complex neural networks. They are trained on a set of data (training dataset) to learn from the properties of the data and then used to make predictions on new, unseen data. Machine learning models have a wide range of applications, including image and speech recognition, medical diagnosis, stock market trading, and battery performance prediction.

Maintenance

Battery terminology

Maintenance refers to the regular procedures performed to keep batteries in optimal working condition. This includes tasks like inspection, cleaning, and performance testing to ensure longevity and efficiency.

Malfunctions

Battery terminology

Failures in a system or device, such as a battery, that prevent it from operating as intended.

Manganese

Battery cell chemistries

Manganese is a chemical element used primarily in lithium-ion batteries cathodes. Manganese improves battery stability, safety, and energy density, contributing to longer-lasting and more reliable performance.

Microgrid

Energy storage

A microgrid is a small-scale power grid that can operate independently or in conjunction with the main electrical grid. Microgrids often use battery storage to provide reliable, local energy solutions.

NCA (Lithium Nickel Cobalt Aluminum Oxide)

Battery cell chemistries

NCA is a high-performance lithium-ion battery cathode chemistry known for its high energy density, long cycle life, and fast charging capabilities. It’s commonly used in electric vehicles, such as Tesla models, and portable electronics.

NFPA 68

Energy storage

NFPA 68 provides requirements for deflagration venting systems to mitigate the effects of explosions in enclosures. In the context of BESS, it applies when battery enclosures or rooms present a risk of gas buildup and explosion, particularly with chemistries that can release flammable gases. Proper venting design per NFPA 68 is essential for mitigating pressure and protecting equipment and personnel during a deflagration event.

NFPA 69

Energy storage

NFPA 69 covers active systems designed to prevent explosions, such as inerting, suppression, and control systems. For energy storage installations, NFPA 69 is relevant when flammable gas accumulation is a risk, and active explosion prevention methods are employed in battery enclosures or dedicated storage rooms. It complements NFPA 68 in situations where prevention is preferable to passive venting.

NFPA 70

Energy storage

NFPA 70, commonly known as the National Electrical Code (NEC), sets the foundation for electrical safety in the United States. Article 706 specifically addresses energy storage systems, including BESS. It outlines requirements for wiring, grounding, disconnects, overcurrent protection, labeling, and interconnection to ensure electrical safety throughout the lifecycle of the storage system.

NFPA 72

Energy storage

NFPA 72 governs the design, installation, and performance of fire detection, alarm, and emergency communication systems. In the context of BESS, it ensures that appropriate fire detection and alarm systems are installed, particularly in indoor or enclosed storage environments, to support early warning and response during thermal events or system failures.

NFPA 855

Energy storage

NFPA 855 is a U.S. safety standard developed by the National Fire Protection Association that governs the installation of stationary energy storage systems, including lithium-ion battery energy storage systems (BESS). It outlines key requirements related to fire suppression, thermal runaway mitigation, separation distances, ventilation, and emergency response planning. NFPA 855 often works in conjunction with other related standards—such as UL 9540 and UL 9540A—which address system safety and fire testing methodologies. Together, these standards are critical for permitting, code compliance, and the safe deployment of energy storage systems.

NFPA 885

Energy storage

National Fire Protection Association standards that provide safety guidelines for the installation of stationary energy storage systems. It covers requirements for system design, installation, ventilation, and maintenance, ensuring the safety of both the public and first responders.

NMC (Lithium Nickel Manganese Cobalt Oxide)

Battery cell chemistries

NMC is a popular lithium-ion battery cathode chemistry, offering a high energy density, good thermal stability, and relatively low cost. It’s widely used in electric vehicles, portable electronics, and grid storage applications. First NMC cathodes contained the same amount of nickel (Ni), manganese (Mn) and cobalt (Co) and were called NMC111 or NMC333. Recent developments increased the amount of Ni and reduced the Mn and Co content leading to relations such as 8 portions of Ni to 1 portion of Mn and Co, also called NMC811.

NPCC (Northeast Power Coordinating Council)

Energy storage

NPCC (Northeast Power Coordinating Council) is a regional organization responsible for ensuring the reliability and security of the electric grid in the Northeastern United States and parts of Canada. NPCC oversees the coordination of power system operations, develops and enforces reliability standards, and promotes collaboration among utilities and grid operators within its jurisdiction to maintain a stable and reliable electric grid.

Nickel

Battery cell chemistries

Nickel is primarily used in the cathode of lithium-ion batteries, typically in nickel-rich compounds like lithium nickel manganese cobalt oxide (NMC), nickel-metal hydride (NiMH) and lithium nickel cobalt aluminum oxide (NCA). Nickel improves the battery's energy density, stability, and overall performance, making it suitable for high-capacity and long-lasting energy storage.

Nominal voltage

Battery terminology

Nominal voltage is the average voltage at which a battery operates during its discharge cycle. It is a key parameter for determining the battery's compatibility with devices and applications. For lithium-ion batteries, the nominal voltage typically ranges between 3.3V and 3.8V, depending on the cell chemistry.

Non-linear Discharge Characteristics

Battery terminology

The property of a battery that causes its discharge behavior to vary non-linearly with different loads and conditions.

North American Electric Reliability Corporation (NERC)

Energy storage

The North American Electric Reliability Corporation (NERC) is a regulatory authority responsible for developing and enforcing reliability standards for the bulk power system in North America. Covering the United States, Canada, and part of Mexico, NERC's mission is to ensure the secure and reliable operation of the interconnected electric grid. NERC oversees system planning, operations, cybersecurity, and compliance through a network of regional entities. Its standards are mandatory and include critical reliability and cybersecurity guidelines like CIP (Critical Infrastructure Protection).

OCV aging

Battery terminology

OCV aging refers to the decline or shift in the open circuit voltage of a battery over its lifespan. This change in OCV is due to the irreversible chemical and physical changes within the battery as it ages. Factors contributing to OCV aging include loss of active materials, formation and growth of the solid-electrolyte interface (SEI), and other degradation mechanisms. As the battery ages, its maximum and minimum OCV values can shift, affecting its total usable capacity. A shift in OCV values can make state of charge estimation more challenging, potentially leading to reduced battery performance and lifespan.

Open Circuit

Battery terminology

A condition where there is a break in the circuit path, preventing current flow.

Open Circuit Voltage (OCV)

Battery terminology

OCV is the difference of electrical potential across the terminals of a battery when it's not under any load (i.e., when no current flows in or out of the battery). The OCV of a lithium-ion battery is determined under certain conditions such as state of charge (SoC) or temperature and can vary with respect to the specific chemistry of the cell.

Operating Strategies

Battery terminology

These strategies may include managing the charging and discharging cycles to balance performance with battery life, or dynamically adjusting parameters based on real-time usage and vehicle/grid conditions.

Operating limits

Energy storage

These are the boundaries within which a battery or energy system must operate to ensure safety, reliability, and longevity. Operating limits can include maximum and minimum state of charge, voltage levels, temperature ranges, and charge/discharge rates.

Operation mode

Battery terminology

Operation mode refers to the different settings or conditions under which a battery operates. These modes can include charging, discharging, standby, and various performance settings optimized for specific applications

Optimization

Battery terminology

Optimization involves enhancing the performance and efficiency of batteries through advanced techniques and technologies like predictive battery analytics. This can include improving charge and discharge rates, increasing energy density, and extending battery life.

Overcharging

Battery terminology

Refers to charging a battery beyond its maximum voltage limit. Overcharging can lead to overheating, electrolyte breakdown, and in severe cases, to a thermal runaway.

Oversizing

Battery terminology

In the context of battery systems, oversizing refers to the practice of installing a battery with more capacity than what is routinely needed. This is often done to account for future load increases, degradation of the battery over time, or to ensure reliability and uninterrupted power supply in critical applications.

PFR Market (Primary Purchase Agreement)

Energy storage

A market mechanism that compensates participants for providing immediate response services to help balance grid frequency.

PPA (Power Purchase Agreement)

Energy storage

A contract between an electricity generator and a buyer to purchase electricity at a pre-agreed price for a specified period.

Particle cracking

Battery terminology

In battery cells, particle cracking refers to the mechanical degradation of electrode materials, often seen in cathode particles. This can happen due to repeated charging and discharging cycles, leading to a decrease in the mechanical integrity of the particles. This degradation can cause a loss of electrical contact within the electrode, reducing the battery's capacity and efficiency over time.

Peak shaving

Energy storage

Peak shaving is the practice of using batteries to reduce the demand on the electrical grid during peak usage times. This helps lower energy costs and prevent grid overloads.

Performance Guarantee (BESS)

Energy storage

A performance guarantee is a contractual commitment in energy and infrastructure projects, including battery energy storage systems (BESS) and power plants, which ensures that the system will meet a minimum threshold of operational performance over a defined period. This guarantee typically covers metrics such as energy output, round-trip efficiency, system response time, and capacity retention.

Unlike an availability guarantee, which ensures that a system is operational and ready to perform, a performance guarantee focuses on how well the system actually performs under operation. It is used as a risk mitigation mechanism for investors, offtakers, and operators, and may include financial penalties or compensation if the system underperforms.

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Performance Manager

Energy storage

The Performance Manager from TWAICE is a software tool designed to make it effortless for asset managers to identify and rectify underperforming components within their battery energy storage systems (BESS), providing system transparency and actionable business insights. It offers a comprehensive overview of the system, displaying the number of underperforming issues, their severity levels, exact locations within the BESS, and recommended actions.

Physico-chemical models

Battery modeling

These are models based on the physical and chemical processes occurring within a system. In the context of batteries, they consider electrochemical reactions, ion diffusion, and other phenomena to describe and predict battery behavior.

Physicochemical-mechanical Degradation

Battery terminology

The combined physical, chemical, and mechanical processes that lead to the deterioration of battery materials and performance.

Pouch cell

Battery cell

A type of battery cell that is housed in a flexible, flat, and rectangular package. The packaging material usually is a laminate of thin metal and plastic layers.

Power

Battery terminology

Power refers to the rate at which energy is supplied or consumed by a lithium-ion battery, measured in watts (W). A battery with higher power can deliver more energy in a shorter period, enabling faster charging and discharging rates.

Power Conversion Systems (PCS)

Energy storage

Power Conversion Systems (PCS) are integrated hardware and control systems used in energy storage and renewable installations to manage the conversion of electrical energy between different forms - typically from direct current (DC) to alternating current (AC), and vice versa. While an inverter is a component that specifically handles DC-to-AC conversion, a PCS includes additional functions such as grid compliance control, bidirectional power flow, frequency regulation, voltage control, and protection systems. In Battery Energy Storage Systems (BESS), the PCS serves as the core interface between the battery modules and the electrical grid, enabling advanced energy management and grid services. PCS units are designed to meet strict requirements for safety, power quality, and efficiency in utility-scale and commercial energy systems.

Power Derating

Energy storage

Power Derating refers to the reduction in the power output that a battery energy storage system (BESS) can deliver compared to its nominal (rated) capacity. This reduction may be deliberate or required due to factors such as environmental conditions, operational constraints, or design limitations. As a result, the system's actual power availability may be lower than expected, affecting its performance, reliability, and ability to meet grid demands. The effect of derating is often represented using a derating curve, which illustrates how power output declines as these influencing variables increase. To determine the derated power output, the rated power is adjusted by a derating factor. For example, if a battery system is rated at 100 kW and experiences a 15% derating, its actual usable output would be 85 kW.

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Power density

Battery cell

Power density measures the amount of power a battery can deliver relative to its size or weight. Higher power density allows for more compact and efficient energy storage solutions.

Power distribution

Energy storage

Power distribution involves managing and directing the flow of electrical power from batteries to various loads and systems. Effective power distribution ensures reliable and efficient energy delivery

Predictive maintenance

Battery terminology

Predictive maintenance uses data analysis and monitoring to predict when a battery will need maintenance. This proactive approach helps prevent unexpected failures and extends battery life.

Prismatic cell

Battery cell

A type of battery cell that comes in a rectangular or square shape, housed in a hard metal or plastic case. Prismatic cells are commonly used in energy storage systems and electric vehicles.

Prussian Blue

Battery cell chemistries

Prussian blue is a deep blue pigment with the chemical formula Fe₄[Fe(CN)₆]₃, and in battery applications, it's used in the form of a compound known as "Prussian blue analogs" or "Prussian blue derivatives." It is used in the cathodes of sodium-ion batteries, where its unique structure provides several advantages. The stability, combined with the cost-effectiveness of the materials, makes Prussian Blue a promising option for large-scale energy storage systems, such as grid storage, where long battery life and low costs are critical. Additionally, while still in development, Prussian Blue-based batteries could eventually find applications in electric vehicles, particularly in lower-cost models.

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RTE (Round Trip Efficency)

Battery terminology

The efficiency of a battery system calculated by dividing the energy output by the energy input over a complete charge-discharge cycle.

Recoverable Energy

Energy storage

Recoverable energy is the portion of lost capacity that can be restored by addressing specific, reversible issues within the system—such as weak cells, state-of-charge imbalances, or non-operational components. Unlike irreversible losses from aging, recoverable energy represents the gap between current performance and what the system could deliver if these correctable factors were resolved.

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