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

Acid :
Compound in a battery that promotes electrochemical reaction.

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.


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.

Battery energy storage system (also known as ESS).

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.

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.

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.

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 battery

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.

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. (80% depth of discharge)

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.

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.



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.

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.

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.

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.


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.


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.

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

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 :
Available in all modern technologies, Flooded (Wet), Absorbed Glass Mat (AGM) & GEL. The foundation of rechargeable batteries, invented in 1859 by French physicist Gaston Plante. Widely used and available in a comprehensive range of sizes and specifications commonly used in starting, lighting, ignition, deep cycle, marine and telecommunications. Lead acid batteries are a highly recycled commodity good with up to 99% recycled material.

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.



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.

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.

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

Nominal voltage :
Terminal voltage of batteries.



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

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.



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.

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.



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).

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.

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).

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 J537 - RC :
Apply a full charge (charge to 14.4–16V at 16°C–43°C (60°F–110°F)). After a 24h rest, apply a regulated 25A discharge to 10.50V (1.75V/cell). Readings are in minutes of discharge time known as “Reserve Capacity” (RC).

SAE J537 - CCA :
Fully charge the battery and cool to -18°C (0°F) for 24 hours. While cold, apply a discharge current equal to the specified CCA reading. To pass, the voltage must stay above 7.2V (1.2V/cell) for 30 seconds.

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.

Silver-zinc :
Rechargeable battery with high specific energy for defense and aerospace

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

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.

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.

Spectroscop :
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.



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.

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).



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.



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

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.

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