Glossary

A, B, C, D, E, F, G, H, I, J, K, L, M,
N, O, P, Q, R, S, T, U, V, W, X, Y, Z

A

• AC impedance (ACZ) – A measurement of the resistance (real-domain impedance) resulting from a 1 kHz voltage or current perturbation on a cell or battery.
• active material – A material that chemically reacts to produce or store electric energy.
• ACZ - See AC impedance.
• Ah – See ampere-hour.
• alkaline battery – A primary or secondary battery in which the electrolyte is an alkaline solution. Nominally, alkaline batteries contain a zinc negative electrode active material, a manganese dioxide postive electrode active material and potassium hydroxide electrolyte. Alkaline batteries have moderate energy density in low-current applications, but poor rate capability due to a high internal resistance.
• amp – See ampere.
• amp-hour – See ampere-hour.
• ampere (amp, A) – A unit of electrical current, defined as an amount of electric charge (in coulombs) per second.
• ampere-hour (amp-hour, Ah) – A unit of electric charge, expressed as the time-integral of current (in amperes) for a defined time period (in hours). For example, a battery discharging 1 ampere for 1 hour has discharged 1 ampere-hour (1 ampere x 1 hour = 1 ampere-hour) of charge.
• anode – An electrode where oxidation occurs.

B

• balancing – Maximizes battery or battery system capacity and life by ensuring that all cell banks or batteries in a series string have comparable state of charge and/or voltage. The electronics in Valence battery systems actively balance cell banks and batteries to maximize life, discharge capacity, and to prevent reversal from occuring.
• battery – A group of two or more electrically interconnected electrochemical cells, including associated electronic components and casing.
• battery discharge indicator (BDI) – Valence hardware accessory that conveys state of charge information for Valence U-Charge RT Systems.
• battery load profile (BLP) – A sequence of discharging, charging, and rest steps performed by a cell, battery, or battery system.
• battery management system (BMS) – A device that monitors and reports battery and battery system voltages, currents, temperatures, and other status conditions while protecting the system from unsafe operation.
• battery pack – see battery.
• battery system – One or more electrically interconnected batteries with a battery management system.
• BDI – See battery discharge indicator.
• BLP - See battery load profile.
• BMS - See battery management system.

C

• C-rate – A notation of current magnitude, expressed relative to the time required to discharge the rated discharge charge capacity of a cell or battery. A 1C rate corresponds to a current magnitude that would discharge the rated discharge charge capacity in 1/1 hour. A 2C rate would correspond to a current magnitude twice that of the 1C current, i.e. the rated discharge charge capacity divided by 1/2 hours. A 0.5C (C/2) rate would correspond to a current magnitude half that of the 1C current, i.e. the rated discharge charge capacity divided by 1/0.5 (=2) hours.
• CAN – see controller area network.
• calendar life – The quantity of time that a cell or battery can be stored before the reversible capacity drops below a minimum required value (signaling end of life).
• capacity – See charge capacity or energy capacity.
• capacity retention – The amount of electrical charge capacity or energy capacity retained after storage and/or cycling, expressed as a percentage of the initial discharge electrical charge capacity or initial energy capacity.
• cathode – An electrode where reduction occurs.
• CC – See constant current.
• cell – An electrochemical device utilizing the potential (voltage) difference between two reduction/oxidation couples (electrodes) to store or provide electric energy. Commercially, a cell is made up of positive and negative electrodes, electrolyte, a separator, and associated packaging.
• cell bank – A collection cells that are electrically connected in parallel. That is, all of the positive terminals of the cells share a common electrical connection and all negative terminals share a common electrical connection.
• cell bank balancing – See balancing.
• cell bank voltage sensor – Obtains cell bank voltage for over-voltage protection and for state of charge determination.
• cell block – A multi-cell entity of a battery.
• cell block temperature sensor – Measures localized cell block temperature for thermal protection purposes and for adjusting state of charge calculations.
• charge – A fundamental property of protons and electrons that whose balance determines the electromagnetic properties of an object. An atom with more protons than electrons is a positively charged ion and an atom with more electrons than protons is a negatively charged ion. Relative movement of these charged ions and/or electrons produces current.
• charge capacity - The quantity of charge that a cell or battery is capable of discharging or charging, quoted at a given temperature and current.
• charge efficiency - The ratio of the discharging charge capacity to charging charge capacity expressed as a percent.
• charger – A device that increases the stored electrochemical energy of a cell, battery, or battery system.
• charging – The conversion of electrical energy, provided by an external electrical source, to chemical energy stored within a cell or battery.
• charging capacity – The quantity of energy or charge a cell or battery can accept and store, quoted at a given temperature and current.
• charging voltage limit - A voltage that is not to be exceeded during a charge. The charging voltage limit may or may not signal an end to charging; often, it triggers a transition from constant current charging to constant voltage charging.
• charging termination current - A current that signals an end to charging during constant voltage charging control.
• CID - See current interrupt device.
• constant current (CC) – A type of charging or discharging control with invariant current.
• constant power (CP) – A type of charging or discharging control with invariant power.
• constant voltage (CV) – A type of charging or discharging control with invariant voltage.
• controller area network (CAN) – A microcontroller and device communication protocol and bus standard commonly used in vehicles.
• coulomb - A unit of electric charge, equivalent to 1 ampere*second or 1/3600 ampere*hour.
• coulombic efficiency – See charge efficiency.
• CP – See constant power.
• current – The rate of electric charge flow, usually expressed in amperes.
• current interrupt device (CID) - A pressure-based safety feature designed to break electrical contact within a cell when internal pressures increase to an unsafe level.
• CV – See constant voltage.
• cycle – One charging step followed by one discharging step.
• cycle-life – The number of cycles that a cell or battery performs at a controlled temperature and current before reaching its end of life discharge capacity.

D

• DCIR – See direct current internal resistance.
• depth of discharge (DOD) – The amount of energy or charge that has been removed from a fully charged cell or battery, expressed as a percentage of the rated capacity.
• direct current internal resistance (DCIR) – The electrical resistance of all current-carrying cell or battery components, usually measured from the voltage response of a direct current step change.
• discharge – The conversion of chemical energy, stored in an electrochemical cell or battery, into electrical energy provided to a circuit.
• discharge capacity – The amount of charge or energy that a cell or battery is capable of discharging, quoted at a given temperature or current.
• discharge termination voltage – The closed circuit voltage threshold that signals the end to a discharge.
• DOD – See depth of discharge.
• duty cycle – The fraction of time that a device is "on" during operation, usually expressed as a percent.

E

• EIS – See electrochemical impedance spectroscopy.
• electric charge - See charge.
• electrochemical cell – See cell.
• electrochemical impedance spectroscopy (EIS) – A technique for studying the electrochemical characteristics of electrodes and cells by measuring the AC Impedance over a range of perturbation frequencies.
• electrode – An assembly of active material(s) and conductive materials on an electrically conductive support.
• electrolyte – An electrically insulative medium that facilitates ion conduction in an electrochemical cell.
• end of charging current – See charging termination current.
• end of discharge voltage – See discharge termination voltage.
• end of life – The performance where a battery can no longer perform to the specifications of an application.
• energy – The capacity to do work or produce heat.
• energy density – The quantity of energy per unit volume.
• energy capacity – The quantity of energy that a cell or battery is capable of discharging or charging at given temperature and current/power.
• energy efficiency – The ratio of the discharge energy capacity to charging energy capacity expressed as a percent.
• equivalent cycles – The cumulative discharged ampere-hours divided by the battery’s rated capacity during lifecycling at <100% depth of discharge.
• E-Rate – A notation of power magnitude, expressed relative to the energy capacity (in watt-hours) of a cell or battery. A 1E rate corresponds to a power magnitude that would discharge the rated energy capacity in 1/1 hour. A 2E rate would correspond to a power magnitude twice that of the 1E power,i.e. the energy capacity divided by ½ hours. A 0.5E (E/2) rate would correspond to a power magnitude half that of the 1E power, i.e. the rated energy capacity divided by 1/0.5 (2) hours.

F

• float charging – Charging a cell or battery at a constant voltage sufficient to maintain the battery in a fully charged state after full charging.
• full charging – Charging constant current to the charging voltage limit followed by charging constant voltage to the charging termination current.
• full discharging – A constant current discharge to the discharge termination voltage.

G

• gravimetric energy – See specific energy.

I

• impedance – See AC impedance.
• internal resistance – See direct current internal resistance.
• intercalation - The insertion or removal of an ion, atom, or molecule to unoccupied, vacant spaces in a host material.
• ion - An atom or a group of atoms that have acquired a net electric charge by gaining or losing one or more electrons.

J

• joule (J) – A unit of energy, equivalent to 1 watt-second or 1/3600 watt-hours.
• joule heating – Heating caused by energy losses associated with current flowing through a resistance.

L

• lead acid battery – A secondary battery in which the positive electrode active material is lead, the negative electrode active material is lead oxide, and the electrolyte is sulfuric acid. In general, lead-acid batteries have a lower specific energy, lower energy density, lower cycle-life, and higher self discharge rate than Valence lithium iron magnesium phosphate solutions.
• LED – See light emitting diode.
• lifecycling – Charging and discharging a cell or battery repeatedly to determine how cell/battery characteristics change with operation.
• light emitting diode – A semiconductor device that emits light.
• lithium ion cell – A secondary cell in which lithium ions transport charge between an intercalatable anode and cathode.
• load – The circuit, device, or system to which a cell or battery discharges.

M

• module – A series string of cell banks within a battery.
• motor controller – A device that controls power delivery to an electric motor.

N

• negative electrode - The electrode that functions as the anode during discharging and the cathode during charging.
• negative terminal – The electrical interface between an external circuit and the negative electrode.
• NiCd – See nickel-cadmium battery.
• NiMH – See nickel-metal hydride battery.
• nickel-cadmium battery (NiCd) – A particular alkaline secondary battery in which the positive active material is primarily nickel and the negative active material is primarily cadmium. Nickel-cadmium batteries have lower specific energy, energy density, and cycle-life than Valence lithium iron magnesium phosphate solutions, have a relatively high self discharge rate, and contain toxic heavy metals.
• nickel-metal hydride battery (NiMH – A particular alkaline secondary battery in which the positive electrode active material is primarily nickel and the negative electrode active material consists of intermetallic metal hydride compounds containing heavy metals. Compared to Valence lithium iron magnesium phosphate solutions, nickel-metal hydride batteries have a higher self discharge rate and lower specific energy energy density, and cycle-life.
• nominal discharge charge capacity – The quantity of charge that can be discharged with a full discharge at a standard constant current when discharge is preceded by full charging.
• nominal discharge energy capacity – The quantity of energy that can be discharged with a full discharge at a standard rate when discharge is preceded by full charging.
• nominal voltage – An approximation of the average discharge voltage of a cell when fully discharged at a standard current, following full charging.

O

• OCV – See open circuit voltage.
• open circuit voltage – The voltage of a cell or battery that has been electrically isolated from a circuit for a sufficiently long period of time.
• over-current protection – Protects battery cells and electronics from damage pursuant to charging or discharging currents greater than designated maximums.
• over-temperature protection - Protects the battery cells and electronics from damage pursuant to temperature exposure that is greater than the designated maximum.
• over-voltage protection – Protects the battery cells from damage and venting pursuant to voltages greater than the designated maximum.
• oxidation – An electrochemical reaction that liberates electrons from an active material, resulting in the electrochemically active ions of the material becoming more positively charged.

P

• parallel connection – Within a group of cells or batteries, the electrical connection of all positive terminals to each other and the electrical connection of all negative terminals to each other. Parallel connections increase the charge capacity, and therefore energy capacity, of the cell group beyond that of a single cell or battery.
• positive electrode - The electrode that functions as the cathode during discharging and the anode during charging.
• positive terminal – The electrical interface between an external circuit and the positive electrode.
• power – The rate of energy flow, usually expressed in watts (W) or kilowatts (kW).
• power density – The discharge power capability of a cell or battery divided by its volume.
• primary battery / cell – A non-rechargeable battery or cell.
• pulse width modulation (PWM) – A method to approximate a continuous waveform by varying the duration and duty cycle of discrete pulses of equal magnitude.
• PWM – See pulse width modulation.

R

• rate – See C-rate or power.
• rate capability - The ability of a cell or battery to discharge or charge at a high current or power.
• rated discharge charge capacity – The amount of charge discharged to the discharge termination voltage at a standard temperature, following full charging,.
• rechargeable cell / battery – See secondary cell.
• reduction – An electrochemical reaction characterized by the acceptance of electrons, resulting in the electrochemically active ions in the material becoming more negatively charged.
• resistance - The opposition to the flow of charged particles (i.e. current) through an object.
• reversal - A damaging condition where a cell or battery is discharged below 0 volts resulting in the positive terminal becoming negative and the negative terminal becoming positive.

S

• secondary battery / cell – A battery or cell that can be safely charged and discharged multiple times.
• self discharge – The charge and energy loss due to side reactions or internal shorts within in a cell, or due to circuitry in a battery.
• separator – A cell component that electrically insulates the positive electrode and negative electrode of an electrochemical cell.
• series charging – The bulk charging of a battery or battery system through application of a voltage or current over a series arrangement of cells or batteries.
• series connection – An electrical connection between the negative terminal of a cell or battery with the positive terminal of another cell or battery to increase the overall voltage and energy of the battery.
• shelf-life – See calendar life.
• short - An undesired electrical pathway between the positive terminal and negative terminal of a cell or battery.
• SOC – See state of charge.
• specific energy – The amount of energy per unit mass for a battery, cell, or material.
• specific power – The amount of power per unit mass for a battery, cell, or material.
• standard temperature – A temperature at which tests are performed to establish rated capacities, nominal voltages, and other cell or battery parameters. Commonly 23 °C or 25 °C.
• (SOC) state of charge – An estimation of the amount of charge remaining in a cell or battery expressed as a percentage of the rated or estimated full discharge charge capacity.
• state of energy – An estimation of the amount of energy remaining in a cell or battery expressed as a percentage of the rated or estimated discharge energy capacity.
• state of health – An approximation of the overall state of a battery or cell by taking into account its environmental and electrical history.
• storage – See calendar life.
• string – A single group of cells or batteries connected in series.
• system – See battery system.

T

• terminal – On a cell, an interface between electrodes and external electrical connections. On a battery, the electrical interface between the battery and external loads.
• thermal runaway – A critical condition caused by a self-sustaining, heat-generating reaction that proceeds uncontrollably. Unlike other lithium ion chemistries, Valence lithium iron magnesium phosphate is not susceptible to thermal runaway.
• thermistor – A device whose resistance changes with temperature. When a known current flows through the thermistor, the voltage measured across the thermistor can be converted to a temperature measurement.
• trickle charging – See float charging.

U

• under-voltage protection - Protects the battery cells from damage pursuant to voltages less than the designated minimum.

V

• volt (V) – A unit measuring voltage.
• voltage – The electropotential difference between two points.

W

• watt (W) – A unit measuring power. Defined as 1 joule per second.
• watt-hour(Wh) – A unit measuring Energy, equal to 3600 joules.
• Wh – See watt-hour.