BU-1101: Glossary

Discover easy-to-understand explanations of technical battery terms.

AC:  Alternating current; current flows in both directions. Household current is AC.

Acid: Compound in a battery that promotes electrochemical reaction.

AGM:  Absorbent Glass Mat is a lead acid battery that uses a glass mat to promote the recombination of gases produced by the charging process.

Allotrope:  Two or more forms of the same element in the same physical state (solid, liquid, gas) that differ from each other in physical and sometimes chemical properties.

Ampere-hours: Symbol Ah is a unit of charge. Example: Drawing a current of one ampere (1A) from a battery for one hour (1h) equates in one ampere-hour (1Ah).

Anode:  Electrode on which oxidation occurs; releases electrons on discharge. When applying power to a device (vacuum tube, diode, battery on charge), the anode is positive; taking power away on discharge turns the anode to negative.

Antimony: Used in lead acid batteries to improve mechanical strengths of lead plates and enhances performance. Other uses are flame proofing, producing low friction applications, and building semiconductors.

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

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

Barrel: Measuring unit for liquids (oil); 1 barrel has 42 US gallons, 35 Imperial gallons, 159 liters.

Basel Convention: International treaty to reduce the movements of hazardous waste between nations; signed in1989 in Basel, Switzerland and made effective in 1992.

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

Battery cycle:  Charge followed by a discharge and recharge. No standard exists as to level of charge and discharge to constitute a cycle.

Battery Directive 2006/66/EC: European legislation on waste batteries to protect the environment.

BESS: Battery energy storage system (also known as ESS)

BMS: Battery Management System used inside or outside a battery to manage charge, discharge and provide SoC; forms an essential part to assure battery longevity and safety.

Bluetooth:  Low-power radio communications up to 10 meters (30 feet). Bluetooth borrowed the name from Harald Bluetooth, a Danish king who lived more than 1,000 years ago.

Boolean bit:  System of symbolic logic devised by George Boole in the 1840s; used in computers.

Button cell:  Miniaturized battery also known as coin cell. Most are non-rechargeable.

Calcium:  Fifth most abundant element by mass in the earth crust; essential for living organisms to build bone, teeth and shells. Discovered by Humphry Davy (1778–1829). Improves mechanical strength of lead plates in lead acid batteries; enhances performance.

Candela (cd): Unit of luminous intensity; agreed international name since 1967.

Capacitance:  Unit measuring the electrical charge in a capacitor (condenser), measured in farad (f).

Capacitor:  Component consisting of two conductive surfaces separated by an insulator. Passes AC; indefinite resistance for DC; voltage lags behind the current (opposite of a coil). 

Capacity: Electrical energy of a battery in ampere-hours (Ah). The stored energy is measured by observing the elapsed time while discharging at a constant current to the end-of-discharge voltage. The capacity is the leading health indicator of a battery.

Capacity offset: Capacity correction when discharging a battery at a higher C-rate than specified.

Carbon dioxide: (CO2) Odorless gas formed during combustion, respiration and decomposition of organic substances. Plants absorb CO2; excess CO2 is blamed for climate change.

Cathode:  Electrode in an electrochemical cell in which reduction takes place by absorbing electrons. During discharge, the cathode is positive; reverse on charge.

C-code:  Abbreviation for  configuration code. C-code is stored in a battery adapter and configures the analyzer to the correct battery settings (Cadex systems).

Cell mismatch:  Cells in a battery pack that have unequal capacities, voltages or resistive values.

Cell reversal:  Cell polarity reverses on a deep discharge at high load. Damages affected cell.

Charge: Replenishing electrical charge to a cell or battery.

Chemical battery: Behavior of the actual battery as opposed to monitoring peripheral activities.

Cobalt (Co): Hard, lustrous, gray metal; used in batteries, magnets, and high-strength alloys.

Co-generation: Utilization of heat and kinetic force. Heat drives steam turbines; kinetic force produces electricity through a generator; charges a battery on deceleration.

Coke: Derivative of coal from which most gases have been removed through heating.

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

Coulombic efficiency, also called faradaic efficiency or current efficiency describes the charge efficiency by which electrons are transferred in a batteries.

C rate:  Unit by which charge and discharge times are scaled. At 1C, the battery charges and discharges at a current that is at par with the marked Ah. (See BU-402)

Current-limiting charger: Keeps current constant and allows voltage to fluctuate. (NiCd, NiMH chargers)

Cycle:  Charge/discharge/charge. No standard exists as to what constitutes a cycle.

Cycle life: Number of cycles a battery can deliver. (End of-battery-life for portable devices is commonly set to 80%.)

Cylindrical cell: Positive and negative plates are rolled up and placed into a cylindrical container.

DC:  Direct current; current flows in one direction. A battery delivers a DC current.

DC-to-DC converter: Converts DC to a higher or lower voltage potential.

Delta temperature over delta time (dT/dt): Senses rate of temperature increase over a given time rather than by measuring the absolute value; used for full charge detection of nickel-based battery. (See BU-407)

Digital battery: Peripheral that monitors battery activity associated with the smart battery.

DIN, IEC:  Capacity of a starter battery is measured with a 0.2C-rate (5h) discharge of a fully charged battery to 1.55V/cell or a 0.05 (20h) discharge to 1.75V/cell.

DoD:  Depth of discharge; 100% is full discharge; 80% is commonly used for specification.

Double-layer capacitor: Electrostatic storage device utilizing the electrical double layer effect that is formed near the surface of the carbon electrode; also called supercapacitors or ultracapacitors.

Driving range: EVs display the allowable driving rang range rather than capacity. As the capacity fades, battery gets charged more and discharged deeper. The full capacity is hidden.

Dumb battery: Basic electrochemical battery with no electronic intelligence with which to communicate.

Electrochemical impedance spectroscopy (EIS), also known as impedance spectroscopy; method to test electrochemical characteristics of a battery; EIS injects AC signals at different frequencies and analyzes the response. (See BU-904)

Electrode:  Conductor or plate in a cell in which an electrochemical reaction occurs.

Electrolyte: Non-metallic conductor of electricity (typically liquid) placed between positive and negative electrodes of a battery. Ion movement enables current flow.

Electrolyte oxidation (EO): Formation of a restrictive film on the Li-ion cathode if the voltage is kept above 4.10V/cell. The longer the battery stays in a high voltage, the more pronounced the degradation will be.

Energy: Work measures over time. Multiplying voltage x current x time = Watt-hours (Wh). Energy is also given in joules (J); 1,000 joules are 0.277Wh.

Energy Cell: Battery cell designed for maximum capacity. Power density may be compromised.

Energy density: 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.

Energy Star: Organization promoting energy efficiency.

Exercise: In battery maintenance, one or several discharge cycles to the end-of-discharge with recharge; prevents memory buildup in NiCd and NiMH batteries.

Farad (f): Charge in coulombs necessary to change the potential between the plates of a capacitor by 1V. (1 Farad = 1 Coulomb per Volt)

Fast charge:  1–3 hours charge time.

Float charge: Similar to trickle or maintenance charge; compensates self-discharge of lead acid battery.

Flow battery: A cross between a conventional battery and a fuel cell. Liquid electrolyte of metallic salts is pumped through a core with positive and negative electrodes, separated by a membrane. The resulting ion exchange generates electricity. (See BU-210b)

Frequency: Number of events in a given time. Indicates how often the AC voltage changes from positive to negative per second, or how many times a battery is cycled.

Fuel cell: Device converts oxygen and hydrogen into electricity and water. (See BU-210)

Fuel gauge: State-of-charge (SoC) indicator to estimate the charge level of a battery.

Fuzzy logic: Multi-valued, mathematical logic derived from blurred data derives at a voted result. Battery rapid testing, image recognition, weather forecasting and medical tests follow fuzzy logic.

Graphene: Allotrope of carbon in a two-dimensional hexagonal lattice in which one atom forms each vertex; establishes the basic structural element of graphite, charcoal diamonds and more.

Graphite: A form of carbon with hexagonally crystallized allotrope, used in lead pencils, lubricants, batteries and the anode of most Li-ion.

Gravimetric energy density: Also known as specific energy; indicates the amount of energy a cell holds in weight (Wh/kg); synonymous with battery runtime.

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

Hertz (Hz): Unit of frequency; 1Hz constitutes one full cycle per second.

Hydrogen (H): Chemical element with atomic number 1; lightest and most abundant chemical element; constitutes roughly 75% of the universe's elemental mass. Hydrogen gas becomes explosive at a concentration of 4 percent.

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

Hysteresis charge: Charger turns off at full charge and resumes after a time to compensate for parasitic loads and self-discharge.

I2C:  Inter-Integrated Circuit is a multi-master, multi-slave, single-ended, serial computer bus invented by Philips Semiconductor.

IEC 60079: Intrinsically safe standards to prevent explosion in areas of flammable gas and dust.

IEC 60086: Safety standard for primary batteries.

IEC 62133: Safety requirements for sealed secondary cells/batteries for portable use. 

IEEE 1625: Standard for rechargeable batteries for mobile computing devices.

IEEE 1725: Standard for rechargeable cells/batteries for mobile phones.

Imaginary impedance: Also known as complex impedance; characterizes the electrical resistance of reactive components as a function of frequency. Rising frequency lowers the capacitive resistance and increases the inductance resistance.

Impedance: Combination of capacitive, inductive and ohmic resistance; measured in ohms (R); frequency dependent.

Inductance (L): Winding that causes an electromotive force when current is applied; frequency dependent; reacts opposite to a capacitor; measurement in Henry (H. 

Intelligent battery: Also known as smart battery; enables communication between device, charger and user.

Internal resistance: Electrical resistance of a battery pack in milliohms (m). A good battery has low resistance; corrosion raises it.

Intrinsically safe battery: Has built-in protection circuit to enable safe operation in a hazardous area; prevents sparks by limiting voltage and current spikes.

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

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

Lead acid battery: Oldest rechargeable battery; used as starter battery wheeled mobility, UPS, etc.

Lithium (Li): 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.”

Lithium battery: Has lithium-metal anode; most are non-rechargeable.

Lithium-ion battery: Rechargeable battery with cobalt, manganese, nickel and/or other metals as cathode and graphite anode.

Lithium-ion polymer battery: Similar to Li ion with a solid polymer as electrolyte; addition of gelled material promotes conductivity.

Lithium polymer battery: Also known as solid-state battery; uses solid polymer as electrolyte; heat induces conductivity.

Load current: Current flow when applying an electrical load.

Manchester coding, also known as phase coding, is used in 1-Wire battery communications to combine data and clock in a single-wire system 

Manganese (Mn): Cathode material of Li-ion. Also used in steelmaking.

Matrix:  Lookup table to compare and derive at characteristics, such as battery capacity.

Max Error: Expected margin of error (%) of charge calibration on SMBus battery.

Memory:  Reversible capacity loss in nickel-based batteries.

Microsecond (μs): One-millionth of a second (10-6).

Milliampere-hour (mAh): Specifies battery capacity or rating; 1000mAh equals 1Ah.

Millihertz: Unit of frequency. Example: 1 Hertz = 1 cycle/second; 1mHz = 1,000 seconds.

Millisecond (ms): One-thousand of a second (10-3).

Nano:  Latin for dwarf. 1 nanometer (nm) is one-billionth (10-9) of a meter or a layer of 3–6 atoms.

NCA:  Nickel-cobalt-aluminum Li-ion; serves as cathode material.

Negative delta V (NDV): Drop in battery voltage when sealed NiCd and NiMH reach full charge; used to detect full charge.

Newton (N):  Unit of force named after Isaac Newton; equal to accelerating 1kg a distance of 1 meter per second; (1N = 0.2248 pounds of force).

Nickel-cadmium battery (NiCd): Rechargeable battery using cadmium as anode and nickel as cathode.

Nickel-hydrogen battery (NiH): Rechargeable battery for satellites; pressure vessel contains the hydrogen.

Nickel-iron battery (NiFe): Rechargeable battery developed by Thomas Edison in 1901.Used for mining; powered German V-1 flying bomb and the V-2 rockets during World War II.

Nickel-metal-hydride battery (NiMH): Similar to NiCd; anode made of a hydride alloy that is less toxic than cadmium; 30 percent more capacity than NiCd but is less durable.

Nickel-zinc battery (NiZn): Similar to NiCd; first developed in 1920; short life due to dendrite growth.

Nit: Unit of brightness equal to one candela per square meter.

NMC:   Lithium-ion with nickel, manganese and cobalt as cathode material.

Nominal voltage: Terminal voltage of batteries.

Nyquist plots:  Invented by Harry Nyquist (1889–1996) while working at Bell Laboratories; provides the  frequency response of a linear system that displays both amplitude and phase angle on a single plot using frequency as parameter.

Ohmic resistance: Electrical DC resistance with no capacitive and inductive reactance.

OhmTest™: Battery resistance measurement based on IEC 61951 (Cadex trademark).

Organic: Relating or belonging to carbon-based chemical compounds. Also relates to an organism, a living entity. Organic matter is the product of decay from a once living organism

Overcharge: Exceeding charge acceptance. The battery heats up, produces gases and is subject to an evet.

Overpack: Package can contain other non-dangerous or compatible dangerous good items. Limit is one package in accordance with Section II of PI 965. (Effective 1 April 2016).

Parasitic load: Power consumption with the device turned off.

Passivation layer: Resistive layer that forms on some batteries after prolonged storage. Applying a brief load breaks the layer and enables current flow.

Peukert law: 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).

Phosphate: Salt or phosphoric acid.

Polymer: Electrical insulator that passes ions.

Pouch cell: Packaged into a flexible, heat-sealable foil pouch similar to wrapping food products.

Power:  Voltage x current = power in watts (W). Also in horsepower (1hp = 746W).

Power Cell: Battery cell designed for maximum current delivery. Energy density may be compromised.

Power density: Also known as volumetric power density; reflects loading capability of a battery.

Power factor:  Ratio of real power versus apparent power. The unity power factor of 1 delivers 100% current to a load; a power factor of 0.50 reduces the contribution to 50%. A purely resistive load (heater elements) has a unity power factor of 1; a purely capacitive or inductive load has a power factor of 0.

Primary battery: Non-rechargeable battery.

Prismatic cell: A battery in which the positive and negative plates are stacked instead of rolled.

Protection circuit: Electronic circuit in a battery pack maintains safety when exceeding design limits.

Quick charger: Charges a battery in 3–6 hours.

QuickSort™: Classifies battery state-of-health into good, low and poor (Cadex trademark).

QuickTest™: Method to quick-test battery state-of-health (Cadex trademark).

Ragone chart: Plots battery performance on specific energy versus specific power

Randles Model: Equivalent electrical circuit representing electrolyte resistance in a battery that is commonly used in electrochemical impedance spectroscopy (EIS).

Rapid charge: Same as quick charge.

Reactance: Inductive and capacitive resistance; frequency dependent.

Recondition: Secondary discharge applied after end-of-discharge to drain the battery further; helps break down crystalline formation (memory) of nickel-based batteries. (See BU-807)

Reformer: Device that extracts hydrogen from fossil and other fuels.

Reserve Capacity: American way of measuring battery capacity by applying a fixed discharge current and measuring time in minutes. Europe uses the ampere-hour (Ah) method under DIN and IEC. DIN and IEC mark the battery in Ah at a typical discharge of 0.2C-rate (5h-rate). See Abbreviation.

Residual capacity: Remaining battery capacity before charge.

Resistance: Restriction to current flow; high resistance generates voltage drop and heat.

Reverse load charge: Intersperses discharge pulses between charge pulses to promote the recombination of gases generated during fast charge; reduces memory.

RSoC: Relative state-of-charge; available charge with capacity fade (also known as SoC).

RSoH: Relative state-of-health; available storage capability when battery is broken in (also known as SoH)

Runtime:  The length of time a battery provides power with a charge.

SAE J537: Test standard for 12V automotive starter batteries.

SAE J1634:  Test standard for electric vehicle; energy consumption, range.

SAE J1772: North American standard for electrical connectors for electric vehicles.

Secondary battery: Rechargeable battery

Self-discharge: Capacity loss due to internal leakage.

Separator: Isolates cathode and anode in a battery; acts as catalyst to promote ion movement from cathode to anode on charge and in reverse on discharge.

Siemens (s): Unit of electric conductance; equal to reciprocal ohm. Named after Ernst Werner von Siemens (1816–1892).

Silver-zinc: Rechargeable battery with high specific energy for defense and aerospace; has a short cycle life; is expensive. 

Single-wire Bus: Simplified smart battery with one wire providing digital communications.

Slow charge: Overnight charge lasting 10–16 hours at a charge current of 0.1C.

Smart battery: Also known as an intelligent battery; communicates with device, charger and user.

SMBus: System Management Bus is a two-wire interface based on I2C; communicates with the battery and device by accepting control parameters and providing battery status, such as state-of-charge, manufacturer information, cycle count and error messages.

Sodium-nickel-chloride: Further development of sodium-sulfur battery. Zeolite Battery Research Africa Project (ZEBRA) made the battery commercially viable; must be heated for operation, used for large UPS and EVs.

Sodium–sulfur (NaS): Molten-salt battery; gained attention in 1970s, 1980s; has a short service life and high manufacturing costs; superseded by the sodium-nickel-chloride battery.

Soft cell: High cell resistance. The voltage drops on a load and is unable to clamp on charge. Very cold temperature and lack of electrolyte causes this condition.

Solid electrolyte interface (SEI): A film composed of lithium oxide and lithium carbonate forms on the surface of the Li-ion anode. The SEI layer grows with cycling and can form a barrier to obstruct ion flow.

Sol: Used by planetary astronomers to refer to the duration of a solar day on Mars. A Mars solar day has a mean period of 24 hours 39 minutes 35.244 seconds.

Specific energy: Also known as gravimetric energy density; indicates the amount of energy a cell contains in weight (Wh/kg); relates to battery capacity; governs runtime.

Specific gravity (SG): Weight ratio of a chemical solution compared to water at a specified temperature. SG of water is 1.0; the electrolyte of a fully charged lead acid battery is about 1.30.

Specific power: Also known as gravimetric power density; reflects the loading capability or the amount of current the battery can deliver; readings in W/kg.

Spectro™: Multi-model electrochemical impedance spectroscopy. Scans battery with a frequency and compares the signatures against matrices representing various conditions. (Cadex trademark) (See BU-904)

Spectroscopy: Analysis of a compound or a battery when scanned with a frequency.

Spinel: Hard glassy mineral consisting of an oxide of magnesium and aluminum that forms a three-dimensional chemical structure. Manganese-based Li ion has such a spinel structure.

State-of-charge (SoC): Indicates charge level of a battery; normally measured in percent. SoC has no relationship with capacity. 

State-of-function (SoF): Reflects battery readiness that verifies capacity, current delivery, voltage, SoC, self-discharge and more; measured in %. (Capacity, current delivery and SoC are most basic.)

State-of-health (SoH): Reflects battery performance that verifies capacity, current delivery, voltage and self-discharge; measured in %. SoH excludes SoC.

Sulfation: Formation of lead sulfate crystal in a lead acid battery that inhibits current flow; storage at low state-of-charge causes this.

Supercapacitor: Electrochemical capacitor also known as an ultracapacitor or double-layer capacitor; specific energy is a fraction of Li-ion. Has high cycle life; offers good cold temperature performances.

System Management Bus (SMBus): Protocol for smart battery (See SMBus in Glossary).

Thermal runaway: Uncontrolled disintegration of a battery from the inside out; can be caused by cell defect, overcharging, excess heat and other abusive conditions.

Thermal voltage: A voltage created by the junction of dissimilar metals when a temperature difference exists between these junctions

Thermistor: Electrical resistor that changes resistance with temperature.

Titanate: Substance used for anode material of some lithium-based batteries.

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

UL 1642: Safety acceptance test for lithium-based batteries by Underwriters Laboratories. Other agencies are IEC 62133, IEEE 1625, IEEE 1725, BAJ (Japan), UN. In 2010, UL 1642 transitioned to IEC 62133, made fully effective on 1 May 2012.

UN 38.3: Safety norms for shipping battery products

Universal Serial Bus (USB): Bi-directional data port featuring a 5-volt supply and two data lines to accommodate auxiliary devices and to charge batteries.

Valve-regulated lead acid (VRLA): Maintenance-free lead acid battery recombines oxygen (positive plate) with hydrogen (negative plate) on charge; valve regulates pressure by release of excess gases. Repeated venting will lead to dry out.

Vinylene carbonate: Additive to improve performance of Li-ion cathode. 

Voltage (V): Electric energy potential per unit charge. 1V = 1J/Coulomb. (1,000 joules = 0.277Wh).

Voltage delay: During prolonged storage, some battery systems develop a passivation layer. This results in a momentarily lower voltage until the film is dissipated through discharge.

Voltage limit: Battery thresholds on charge and discharge.

Voltage-limiting charger: Current is allowed to fluctuate in saturation mode while the voltage is capped (lead acid and Li ion charging).

Volumetric energy density: Also known as energy density; specifies energy storage in volume (Wh/l). (See Energy Density in this Glossary)

Watt (W):  Unit of power; ampere (A) times volt (V) equals watts (W).

Watt-hour (Wh): Unit of electrical energy equivalent to a power consumption of one watt for one hour (One watt-hour = 3600 Joules). Multiplying a battery voltage (V) by the rated capacity (Ah) gives the battery energy in Wh. Example: 14.4V x 2.5 Ah = 36 Wh.

Wi-Fi:  Wireless Internet connections; based on 2.4GHz 802.11b standard.

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

Zinc-air: Generates electrical energy by an oxidation process of zinc and oxygen. Most zinc-air batteries are non-rechargeable, provide high specific energy but have poor load capabilities.

Last updated 2017-11-20

 

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