Glossary
AC
Alternating current; current flows in both directions. Household current is AC.
AGM (Absorbent Glass Mat) battery
A lead acid battery using a glass mat to promote recombination of the gases produced by the charging process.
Ampere-hours (Ah)
The energydrawn from a battery in one hour. (A current of 1A for one hour = 1Ah.)
Anode
The electrode on which oxidation occurs is called the anode; it releases electrons. When applying power to a device (vacuum tube, diode, battery on charge), the anode is positive; withdrawing power on discharge makes the anode negative. In a device that consumes power (charge), the anode of a battery is positive; a device that provides power (discharge), the anode is negative.
Barrel
Measuring unit for oil and other industries; 1 barrel has 42 US gallons, 35 Imperial gallons or 159 liters.
Battery
Electrochemical cell, or cells, connected in series (some may be in parallel). A battery is composed of the anode (negative electrode), cathode (positive electrode), separator and electrolyte as catalyst.
Battery cycle
Full charge, followed by a full discharge and recharge. No standard exists as to what level the battery needs to be discharged to constitute a cycle.
Battery Management System (BMS)
System inside or outside of a battery to manage charge and discharge, as well as report state-of-function; BMS is an important part of hybrid and electric cars, as well as satellites.
Bluetooth
Low-power radio communications to support personal consumer devices and peripherals over short distances of up to 10 meters (30 feet). Bluetooth borrowed the name from Harald Bluetooth, a king in Denmark more than 1,000 years ago.
Boolean bit
A 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.
Capacitance
Unit to hold an electrical charge in a capacitor (or condenser), which is measured in farad. The stored energy is in the form of a static charge (voltage difference between two electric fields separated by a dielectric insulator).
Capacitor
A device consisting of two conductive surfaces separated by an insulator. The resistance of a capacitor is indefinite on DC and decreases with rising frequency. When placed in the path of an AC current, the voltage lags behind the current (opposite of a coil).
Capacity
Electrical energy of a battery as expressed in ampere-hours (Ah). The energy is measured by observing the elapsed time while discharging a battery at a constant current to the specified end-of-discharge voltage.
Capacity offset
Capacity correction when discharging a battery under a higher or lower C‑rate than specified. For example, a lead acid battery produces a higher capacity if discharged at a 20-hour rate than at a 5-hour rate.
Carbon dioxide (CO2)
Heavy odorless gas formed during respiration, combustion and decomposition of organic substances. Plants absorb CO2 from the air by in photosynthesis.
Cathode
Electrode in an electrochemical cell in which reduction takes place, absorbing electrons. During discharge the positive electrode of the cell is the cathode. During charge the situation reverses and the negative electrode of the cell is the cathode. In a discharging battery, the cathode refers to the positive electrode.
C-code
Abbreviation of “configuration code” defining the battery parameters; C-code is stored in a battery adapter and configures the analyzer to the correct battery settings (Cadex systems).
Cell mismatch
Cells within a battery pack that have different capacities, voltages or resistive values. Differences in capacity are most common.
Cell reversal
During deep discharge, the strong cells apply a reverse polarity across a depleted cell when discharging too low. Cell reversal can damage the cell.
Charge
Replenishing electrical charge to a cell or battery.
Cobalt (Co)
Hard, lustrous, gray metal with atomic number 27; used for batteries, preparation of magnets, and high-strength alloys.
Co-generation
Utilization of heat or kinetic force as by-product. Heat drives steam turbines; kinetic force produces electricity through a generator.
Coke
Derivative of coal from which most gases have been removed through heating.
Coulomb
Unit of electric charge. One coulomb (1C) is equal to 1 ampere in 1 second.
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. For example, 1C charges and discharges a 2Ah battery at 2A; 0.5C at 1A and 0.25C at 0.5A.
Current-limiting charger
Charging occursby keepingthe current constant and allowing the voltage to fluctuate (typically used on NiCd and NiMH chargers).
Cycle
Charge/discharge/charge of a rechargeable battery. No standard exists as to what depth of discharge (DoD) constitutes a cycle.
Cycle life
Number of cycles before a battery is no longer usable. (A battery is considered non-usable if the delivered capacity of a fully charged battery falls to 60–80 percent; the application specifies the capacity threshold.)
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
A converter that transforms a direct current (DC) voltage to a higher or lower potential.
Delta Temperature over delta time (dT/dt)
Senses the rate of temperature increase over time rather than measuring the absolute temperature to detect the full charge state of a battery.
DoD
Depth of discharge; 100 percent DoD is full discharge; 80 percent DoD is commonly used for specification. No standard exists as to what DoD constitutes a cycle.
Double layer capacitor
Capacitor with high farad rating made possible by a double layer that is formed near the surface of the carbon electrode. Also known as supercapacitor or ultracapacitor, the double layer capacitor serves as an energy storage device when fast-charging and high discharge currents are required.
Dumb battery
Battery containing no electronic intelligence with which to communicate.
Electrochemical impedance spectroscopy (EIS)
Method totest the electrochemical characteristics of a battery; EIS injects AC signals at different frequencies and analyzes the response.
Electrode
Conducting element within 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. Physical movement of ions enables current flow.
Energy
The work a physical system is capable of performing over time.In electrical terms, multiplying voltage times current overtime equals Watt-hours (Wh). Energy is also given in joules (J); 1,000 joules are 0.277Wh.
Energy density
Also known as volumetric energy density; indicates theamount of energy a cell can contain in volume (Wh/l). The energy density is synonymous with the runtime of a battery.
Energy Star
An organization that promotes energy efficiency. Some countries mandate meeting the Energy Star requirements.
Exercise
Commonly understood as one or several discharge cycles to the end-of-discharge voltage threshold with subsequent recharge. Used to maintain NiCd and NiMH batteries.
Farad (f)
Unit of capacitance that stores 1 coulomb of electrical charge when applying 1 volt of electrical tension.
Fast charge
Typical fast charge time is 1–3 hours; charger detects full state-of-charge and switches to trickle charge (nickel- and lead-based) or disconnects from any charge (Li-ion).
Float charge
Similar to trickle charge. Compensates for the self-discharge of a lead acid battery.
Frequency
Number of occurrences within a given time. Frequency indicates how many times the voltage potential changes from positive and negative per second, or how many times a battery is being cycled in a given time.
Fuel cell
Device convertsoxygen and hydrogen into electricity and water.
Fuel gauge
State-of-charge (SoC) indicator estimates the remaining charge of abattery.
Fuzzy logic
A form of multi-valued, mathematical logic derived from a range of blurred data to deal with reasoning that is approximate rather than precise. Battery rapid testing, image recognition and weather forecasting use fuzzy logic.
Graphite
A form of carbon with hexagonally crystallized allotrope, used in lead pencils, lubricants, batteries, etc.
Gravimetric energy density
Also known as specific energy; indicates theamount of energy a cell can contain in weight (Wh/kg). The gravimetric energy density is synonymous with the runtime of a battery.
Hertz (Hz)
Unit of frequency; 1 Hz constitutes one full cycle per second.
Hydrogen (H)
A chemical element with atomic number 1. Hydrogen is the lightest and most abundant chemical element, constituting roughly 75 % of the universe's elemental mass.
Hydrometer
Device used to measure the specific gravity of a fluid; reads state-of-charge of lead acid and other flooded batteries.
Hysteresis charge
Chargers turns off at full charge; a periodic recharge compensates for the self-discharge.
Imaginary impedance
Also known as complex impedance, the imaginary impedance is the electrical resistance of reactive components that changes with frequency. The capacitive resistance decreases with rising frequency and the inductance resistance increases.
Impedance
Combination ofcapacitive, inductive and pure ohmic resistance; applies to battery and other reactive devices. Impedance is measured in ohms (R) and is frequency dependent.
Inductance (L)
A coil that opposes AC and creates magnetic flux measured in Henry (H). When placed in the path of an AC current, the current lags behind the voltage (opposite of a capacitor).
Intelligent battery
Also known as a “smart” battery; contains circuitry to enable communication between the battery, application, charger and user.
Internal resistance
Electrical resistance of a battery pack given in milliohms (mW). A good battery that is fully charged has a low resistance; an aged or empty battery has a higher resistance.
Intrinsically safe battery
Battery with built-in protection circuitry to allow safe operation in a hazardous area. Electronic circuit prevents sparks by limiting voltage and current peaks.
Ion
Atom or molecule with unequal number of electrons and protons; provides a positive or negative electrical charge.
Joule (J)
Measure of energy or cell capacity. For electrical energy, 1 joule is 1 amp at 1 volt for 1 second, or one watt-second; 1Wh = 3.6kJ; 1,000 joules = 0.277Wh; also applies to mechanical energy..
Lead acid battery
Rechargeable battery in flooded and sealed versions; has a low specific energy and is commonly used for wheeled mobility and stationary applications.
Lithium(Li)
Soft, silver-white metal belonging to the alkali metal group with atomic number 3. Lithium is the lightest metal and the least dense in the element family. Johan August Arfwedson from Sweden discovered lithium in 1817 and it was named after the Greek word “lithos,” meaning “stone.”
Lithium battery
Battery using lithium metal on the anode. Most lithium batteries are non-rechargeable.
Lithium-ion battery
Rechargeable battery with graphite anode; the cathode consists of cobalt, manganese-nickel phosphate, or a combination thereof. Other anode materials are being tried.
Lithium-ion polymer battery
Rechargeable battery similar to Li‑ion with a solid polymer as electrolyte; addition of gelled conductive material promotes conductivity.
Lithium polymer battery
Rechargeable battery using solid polymer as electrolyte; requires heat to promote conductivity.
Load current
Current draw when applying an electrical load.
Manganese (Mn)
Chemical element with atomic number 25. Manganese is used in combination with iron and other minerals in steelmaking and fabrication of Li-ion batteries.
Matrix
In batteries, a matrix serves as a reference to estimate characteristics, such as capacity.
Memory
In nickel-based batteries, memory relates to reversible capacity loss. The modern definition of memory refers to crystalline formation.
Microsecond (ms)
One-millionth of a second (10-9).
Milliampere-hour (mAh)
Specifies battery capacity or rating; 1000mAh equals 1Ah.
Millisecond (ms)
One-thousand of a second (10-6).
Nano
Latin word for “dwarf.” One nanometer is one-billionth (10-9) of a meter, a diameter of 3–6 atoms.
NCA
Lithium-ion battery made of nickel-cobalt-aluminum.
Negative delta V (NDV)
Drop in battery voltage when a sealed NiCd or NiMH battery reaches full charge; NDV detects full charge on nickel-based batteries in chargers.
Newton (N)
International unit of force named after Isaac Newton (1N = 0.2248 pounds of force).
Nickel-cadmium battery (NiCd)
Rechargeable battery using cadmium on the anode and nickel on the cathode; the electrolyte is alkaline-potassium-hydroxide.
Nickel-hydrogen battery (NiH)
Rechargeable battery commonly used for space applications; uses pressure vessels to contain the hydrogen.
Nickel-iron battery (NiFe)
Rechargeable battery developed by Thomas Edison in 1901.Used for mining in Europe, and during World War II. NiFe powered the German V-1 flying bomb and the V-2 rockets.
Nickel-metal-hydride battery (NiMH)
Similar to nickel-cadmium; the anode is made of a hydride alloy that is less toxic than the cadmium of NiCd; offers 30 percent more capacity than NiCd but is less durable.
Nickel-zinc battery battery (NiZn)
Similar to nickel-cadmium; first developed in 1920 but suffered from short life due to dendrite growth. NiZn is being reconsidered for commercial uses.
Nit
A unit of illuminative brightness equal to one candle per square meter, measured perpendicular to the rays of the source.
NMC
Lithium-ion battery made of one-third nickel, one-third manganese and one-third cobalt or similar combinations.
Nominal voltage
Refers tothe accepted standard of a terminal voltage. The nominal voltage of NiCd is 1.20 or 1.25V/cell; Li-ion can be 3.6 or 3.7V/cell.
Nyquist plots
Invented by Nyquist, who worked at Bell Laboratories; Nyquist plots are a way of showing frequency responses of linear systems. Nyquist plots display both amplitude and phase angle on a single plot, using frequency as a parameter in the plot.
Ohmic resistance
Pure electricalDC resistance without capacitive and inductive reactance.
OhmTest™
Internal resistance measurement of a battery using pulse method (Cadex trademark).
Organic
Relating or belonging to chemical compounds having a carbon base.
Overcharge
Exceeding the full charge acceptance ofa battery. The battery heats up and produces gases.
Parasitic load
In electrical terms, power consumptionwhen an appliance is turned off.
Passivation layer
Resistive layer that forms in some cells after prolonged storage. The passivation layer must be broken to enable proper operation; applying a charge/discharge may do this.
Peukert law
Reflects internal resistance and recovery of lead acid and other battery chemistries. A low reading close to one (1) indicates a well-performing battery with minimal losses.
Phosphate
A salt or phosphoric acid.
Polymer
Electrical insulator that passes ions.
Pouch cell
Cell packaged into a flexible, heat-sealable foil pouch.
Power
Transferable power.In electrical terms, multiplying voltage times currentequals power in watts (W). Power is also given in horsepower (1hp = 746W). Power over time is energy in Wh or joule.
Power density
Also known as volumetric power density; reflects the loading capability or the amount of current the battery can deliver. Power density is synonymous with power delivery; readings are in Wh/l.
Power factor
Ratio of real power to apparent power. The unity power factor of 1.00 delivers 100 percent of the current to a load; a power factor of 0.50 reduces the contribution to 50 percent. A purely resistive load (heater elements) has a unity power factor; purely capacitive or inductive loads have zero pf.
Primary battery
Non-rechargeable battery.
Prismatic cell
A battery in which the positiveand negative plates are stacked instead of rolled.
Protection circuit
Electronic circuitbuilt into a battery pack to maintain safe operation of a battery and equipment when improperly handled.
Quick charger
Charger that charges a battery in 3–6 hours.
QuickSortä
Classification tool that sorts battery state-of-health into groups of good, low and poor (Cadex trademark).
QuickTestä
Method to quick-test the state-of-health of a battery (Cadex trademark).
Rapid charge
Same as quick charge.
Reactance
Presence of inductive and capacitive resistance; the reading is frequency dependent.
Recondition
Secondary discharge applied below the 1.0V/cell cut-off threshold of a nickel-based battery; helps break down crystalline formation (memory).
Reformer
A device that extracts hydrogen from fossil and other fuels. The catalytic reaction of a reformer separates the hydrogen from the carbon in a fuel and mixes the carbon to form carbon dioxide that is released into the atmosphere.
Residual capacity
Remaining battery capacity when a portable device cuts off, or capacity prior to charge.
Resistance
Electrical resistance is a restriction of current flow. Batteries with high internal resistance are unable to deliver high currents on demand; resistance generates voltage drop and heat.
Reverse load charge
Charge method interspersing discharge pulses between charge pulses to promote the recombination of gases generated during fast charge; helps reduce memory.
Runtime
The length of time a battery can provide power with a charge.
SAE J537
Standard to serve as a guide for testing procedures of automotive 12V storage batteries.
SAE J1634
Electric vehicle energy consumption and range test procedure.
Secondary battery
Rechargeable battery.
Self-discharge
Capacity loss during storage due to internal leakage between the positive and negative plates in a cell.
Silver-zinc
Rechargeable battery with high specific energy; used for defense and aerospace applications, as well as professional TV cameras; battery is expensive and has a short cycle life.
Single Wire Bus
Simplified “smart” battery using only one wire for 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; pack contains intelligence to communicate between battery, equipment, charger and user.
SMBus
System Management Bus is a two-wire interface that 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
A further development of sodium-sulfur battery. Zeolite Battery Research Africa Project (ZEBRA) made the battery commercially viable; needs heat for operation, used for large UPS and EVs.
Sodium–sulfur (NaS)
Gained attention in 1970s and 1980s; battery has a short service life and high manufacturing costs. The sodium-nickel-chloride battery (ZEBRA) is its successful replacement.
Soft cell
High cell resistance causes the applied voltage to rise above a defined level during charge and drops low on a load. Cold temperature or lack of electrolyte causes the soft cell condition.
Specific energy
Also known as gravimetric energydensity;indicates theamount of energy a cell can contain in weight (Wh/kg). Specific energy (capacity) is synonymous with the runtime of a battery.
Specific gravity (SG)
Weight ratio of a chemical solution compared to water at a specified temperature. The 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. Specific power is synonymous with power delivery; readings are in Wh/kg.
Spectroä
Stands for multi-model electrochemical impedance spectroscopy (Cadex trademark).
Spectroscopy
Same terminology as electrochemical impedance spectroscopy (EIS).
Spinel
A hard glassy mineral consisting of an oxide of magnesium and aluminum that forms a three-dimensional chemical structure. Manganese-based Li‑ion consists of a spinel structure.
Spintronicaä
Monitors battery state-of-charge through magnetic field strength. Applies to lead- and lithium-based batteries (Cadex trademark).
State-of-charge (SoC)
Indicates themaximum charge a battery can hold. A fully charged battery has 100 percent SoC; one that is at the half way point has 50 percent and an empty pack has zero SoC.
State-of-function (SoF)
Reflects battery readiness; includes capacity, ability to deliver current (internal resistance), voltage, self-discharge, charge acceptance and SoC. A battery that meets manufacturer’s specifications has an SoF of 100 percent; performance degradation lowers the reading.
State-of-health (SoH)
Reflects performance; includes capacity, ability to deliver current (internal resistance), voltage, self-discharge and charge acceptance. A battery that meets manufacturer’s specifications has an SoH of 100 percent; capacity loss and other anomalies lower the readings. SoH excludes SoC.
Sulfation
Lead sulfate crystal formation in a lead acid battery that inhibits current flow, caused by storage at low state-of-charge.
Supercapacitor
Also known as an ultracapacitor or double layer capacitor, the supercapacitor is an electrochemical capacitor that can charge and discharge quickly. The specific energy is about one-tenth that of lithium-ion but has a high cycle life and performs well at cold temperatures.
System Management Bus (SMBus)
Protocol for “smart” battery.
Thermal runaway
Uncontrolled disintegration of a battery from inside out; can be caused by cell defect, overcharging, excess heat and other abusive conditions.
Titanate
Substance used for anode material of some lithium-based batteries.
Trickle charge
Small charge to compensate for the self-discharge of a battery.
UL1642
A safety acceptance test for lithium-based batteries mandated by Underwriters Laboratories.Other commonly used approval norm is IEC62133.
Universal Serial Bus (USB)
The USB port is a bi-directional data port featuring a 5-volt supply and two data lines to accommodate auxiliary devices such as memory sticks, keyboards, mice, wireless interfaces, cameras, MP3 players and battery chargers.
Valve-regulated lead acid (VRLA)
Maintenance-free lead acid battery for uninterruptible power supply systems (UPS); recombines oxygen (positive plate) with hydrogen (negative plate) during charge; valves regulate cell pressure through release of gases.
Voltage (V)
Electric energy potential per unit charge. One volt = 1 joule per second(1,000 joules = 0.277Wh).
Voltage delay
During prolonged storage, some battery systems develop a passivation film on the surface of the active material, delivering a momentarily lower voltage until the film dissipates through discharge.
Voltage limit
Set threshold on charge and discharge of a battery.
Voltage-limiting charger
Charging occurs bylimiting the battery voltage at a maximum charge level and allowing current to fluctuate (typically used on lead acid and Li‑ion chargers).
Volumetric energy density
Also known as energy density; indicates theamount of energy a cell can contain in volume (Wh/l). The volumetric energy density is synonymous with the runtime of a battery.
Watt (W)
Unit of power; ampere (A) times volt (V) equals watts (W).
Watt-hour (Wh)
Unit of power in one hour. Multiplying the nominal battery voltage (V) by the rated capacity (Ah) gives the battery energy in Wh. Example: 14.4V by 2.5A = 36Wh.
Wi-Fi
Radio waves to provide wireless high-speed Internet and network connections; based on 2.4GHz 802.11b standard.
Zapping
Applying a momentary high-current pulse to a battery to evaporate a short. Zapping is said to improve new NiCd batteries.
Zinc-air
Generates electrical power by an oxidation process of zinc and oxygen from the air. Most zinc-air batteries are non-rechargeable; offer a high specific energy but poor load capabilities.
