Battery Terminology

Accumulator A fairly old term for a lead-acid battery, with a number of cells in series to ‘accumulate’ a higher voltage.

Alkaline-Manganese Dioxide Cell A type of primary cell which uses an anode of powdered zinc, a cathode of manganese dioxide and a potassium hydroxide electrolyte. Offers up to 8 times the capacity of carbon-zinc cells. Commonly called the alkaline battery.

Ampere-hour (Ah) The unit used in specifying the storage capacity of a battery. A battery with 1Ah capacity can supply a current of one ampere for one hour or 0.5A for two hours, etc. 1Ah ist he equivalent of 3600 coulombs of electrical charge.

Ampere-Hour Capacity The number of ampere-hours which can be delivered by a storage battery on a single discharge. The ampere-hour capacity of a battery on discharge is determined by a number of factors, of which the following are the most important: final limiting voltage; quantity of electrolyte; discharge rate; density of electrolyte; design of separators; temperature, age, and life history of the battery; and number, design, and dimensions of electrodes.

Anode In a primary or secondary cell, the metal electrode that gives up electrons to the load circuit and dissolves into the electrolyte.

Aqueous Batteries Batteries with water-based electrolytes.

Available Capacity The total battery capacity, usually expressed in ampere-hours or milliampere-hours that are available to perform work. This depends on factors such as the endpoint voltage, quantity and density of electrolyte, temperature, discharge rate, age, and the life history of the battery.

Battery A device that transforms chemical energy into electric energy. The term is usually applied to a group of two or more electric cells connected together electrically. In common usage, the term "battery" is also applied to a single cell, such as a household battery. Battery Types -- There are, in general, two types of batteries: primary batteries, and secondary storage or accumulator batteries. Primary types, although sometimes consisting of the same active materials as secondary types, are constructed so that only one continuous or intermittent discharge can be obtained. Secondary types are constructed so that they may be recharged, following a partial or complete discharge, by the flow of direct current through them in a direction opposite to the current flow on discharge. By recharging after discharge, a higher state of oxidation is created at the positive plate or electrode and a lower state at the negative plate, returning the plates to approximately their original charged condition.

Battery Capacity The electric output of a cell or battery on a service test delivered before the cell reaches a specified final electrical condition and may be expressed in ampere-hours, watt-hours, or similar units. The capacity in watt-hours is equal to the capacity in ampere-hours multiplied by the battery voltage.

Battery Charger A device capable of supplying electrical energy to a battery.

Battery-Charging Rate The current expressed in amperes at which a storage battery is charged.

Battery Voltage, final The prescribed lower-limit voltage at which battery discharge is considered complete. The cutoff or final voltage is usually chosen so that the useful capacity of the battery is realized. The cutoff voltage varies with the type of battery, the rate of discharge, the temperature, and the kind of service in which the battery is used. The term "cutoff voltage" is applied more particularly to primary batteries, and "final voltage" to storage batteries. Synonym: Voltage, cutoff.

C Rate The charging or discharging rate of a cell or battery, expressed in terms of its total storage capacity in Ah or mAh. So a rate of 1C means transfer of all of the stored energy in one hour; 0.1C means 10% transfer in one hour, or full transfer in 10 hours; 5C means full transfer in 12 minutes, and so on.

CC Charging (Constant-Current Charging) Restoring charge to a battery in a mode where the charging current level is kept substantially constant.

CV Charging (Constant-Voltage Charge) Restoring charge to a battery in a mode where the battery’s terminal voltage is kept substantially constant, or kept below a certain level.

Carbon-Zinc Battery The earliest type of primary cell and battery, first developed by Georges Leclanché in 1868 and still very widely used. It uses carbon and manganese dioxide as the positive electrode and zinc as the negative electrode, with an aqueous solution of ammonium chloride and zinc chloride as the electrolyte.

Capacity The quantity of electricity delivered by a battery under specified conditions, usually expressed in ampere-hours.

Cathode In a primary or secondary cell, the electrode that, in effect, oxidizes the anode or absorbs the electrons.

Cell An electrochemical device, composed of positive and negative plates, separator, and electrolyte, which is capable of storing electrical energy. When encased in a container and fitted with terminals, it is the basic "building block" of a battery.

Cell Reversal In NiCad batteries with a number of cells in series, excessive discharge can cause the cells with least capacity to be partly recharged in the reverse direction. Tends to result in cell damage.

Charge Applied to a storage battery, the conversion of electric energy into chemical energy within the cell or battery. This restoration of the active materials is accomplished by maintaining a unidirectional current in the cell or battery in the opposite direction to that during discharge; a cell or battery which is said to be charged is understood to be fully charged.

Charge Rate The current applied to a secondary cell to restore its capacity. This rate is commonly expressed as a multiple of the rated capacity of the cell. For example, the C/10 charge rate of a 500 Ah cell is expressed as, C/10 rate = 500 Ah / 10 h = 50 A. In other words the C rate, but as applied to recharging.

Charge Retention The degree to which a charged cell or battery maintains its capacity when not supplying load current.

Charging The process of supplying electrical energy for conversion to stored chemical energy.

Constant-Current Charge A charging process in which the current of a storage battery is maintained at a constant value. For some types of lead-acid batteries this may involve two rates called the starting and finishing rates.

Constant-Voltage Charge A charging process in which the voltage of a storage battery at the terminals of the battery is held at a constant value.

Cutoff Voltage A voltage level or threshold where either the charging or discharging of a battery is ended, or should be ended for optimum battery life.

Cycle One sequence of charge and discharge. Deep cycling requires that all the energy to an end voltage established for each system be drained from the cell or battery on each discharge. In shallow cycling, the energy is partially drained on each discharge; i.e., the energy may be any value up to 50%.

Cycle Depth The degree to which the charge of a battery is drawn from it during discharge, expressed as a percentage of the total battery capacity.

Cycle Life For secondary rechargeable cells or batteries, the total number of charge/discharge cycles the cell can sustain before it becomes inoperative. In practice, end of life is usually considered to be reached when the cell or battery delivers approximately 80% of rated ampere-hour capacity.

Deep Cycling Repeated subjection of a battery to deep discharging and recharging; i.e., frequent withdrawal of most of the battery’s total storage capacity.

Depth of Discharge The relative amount of energy withdrawn from a battery relative to how much could be withdrawn if the battery were discharged until exhausted.

Discharge The conversion of the chemical energy of the battery into electric energy.

Discharging Withdrawing the stored energy from a cell or battery.

Discharge, deep Withdrawal of all electrical energy to the end-point voltage before the cell or battery is recharged.

Discharge, high-rate Withdrawal of large currents for short intervals of time, usually at a rate that would completely discharge a cell or battery in less than one hour.

Discharge, low-rate Withdrawal of small currents for long periods of time, usually longer than one hour. Discharge Rate: The rate at which charge is withdrawn from a cell or battery during discharge; i.e., the discharge current, expressed in terms of the battery’s capacity. In other words the C rate, as applied to discharging.

Drain Withdrawal of current from a cell.

Dry Cell A primary cell in which the electrolyte is absorbed in a porous medium, or is otherwise restrained from flowing. Common practice limits the term "dry cell" to the Leclanché cell, which is the common commercial type. Dry Cell Battery: The most common type of cell or battery nowadays, where the electrolyte is either in non-liquid form (i.e., a paste or gel) or absorbed in a porous separator material. This allows the cell or battery to be sealed.

EOC Voltage The terminal voltage of a secondary cell or battery at the end of charging.

EOD Voltage The terminal voltage of a cell or battery which is specified as representing the end of discharge.

Electrochemical Couple The system of active materials within a cell that provides electrical energy storage through an electrochemical reaction.

Electrode An electrical conductor through which an electric current enters or leaves a conducting medium, whether it be an electrolytic solution, solid, molten mass, gas, or vacuum. For electrolytic solutions, many solids, and molten masses, an electrode is an electrical conductor at the surface of which a change occurs from conduction by electrons to conduction by ions. For gases and vacuum, the electrodes merely serve to conduct electricity to and from the medium.

Electrolyte A chemical compound which, when fused or dissolved in certain solvents, usually water, will conduct an electric current. All electrolytes in the fused state or in solution give rise to ions which conduct the electric current.

Electropositivity The degree to which an element in a galvanic cell will function as the positive element of the cell. An element with a large electropositivity will oxidize faster than an element with a smaller electropositivity.

End-of-Discharge Voltage The voltage of the battery at termination of a discharge.

Energy Output capability; expressed as capacity times voltage, or watt-hours.

Energy Density Ratio of cell energy to weight or volume (watt-hours per pound, or watt-hours per cubic inch).

Energy loss The wasted energy due to internal resistance.

Fast Charging A term used to describe charging a battery at a rate of 0.5C or higher — i.e., in less than 2 hours.

Float Charging A term used to describe charging a battery at a rate only sufficient to neutralize its self-discharge — i.e., maintain it at full capacity.

Flooded cell A type of wet cell where the active electrodes are submerged in liquid electrolyte. The common car or truck battery uses this type of cell.

Galvanic Cell A combination of electrodes, separated by electrolyte, that is capable of producing electrical energy by electrochemical action. An electrochemical cell which employs a chemical reaction to generate electrical energy. The first such cell is attributed to Luigi Galvani in 1792 — although Alessandro

Volta was the first to explain how it worked, in 1800.

Gassing The evolution of gas from one or both of the electrodes in a cell. Gassing commonly results from self-discharge or from the electrolysis of water in the electrolyte during charging.

Internal Resistance The resistance to the flow of an electric current within the cell or battery. All cells and batteries inevitably exhibit internal resistance, which limits discharging and charging current levels and produces heat within the battery.

Lead-Acid Battery A type of secondary battery which uses a positive electrode of lead oxide, a negative electrode of metallic lead and an electrolyte of sulphuric acid (in either liquid or gel form). First developed in 1859 by French physician Gaston Planté.

Li-ion Battery The lithium-ion battery is a secondary battery, which uses anegative electrode of lithium-cobalt dioxide and a positive electrode of carbon (coke or graphite), with an electrolyte of a lithium salt dissolved in an organic solvent.

Lithium-Manganese Battery A type of primary cell or battery which uses manganese dioxide and carbon as the positive electrode, lithium metal foil as the negative electrode and lithium perchlorate dissolved in propylene carbonate as the electrolyte. Often called simply ‘lithium cells’, they offer very high energy storage density.

Memory Effect If NiCad cells or batteries are subjected to repeated shallow cycling, their internal structure changes and they lose storage capacity — known as the memory effect.

Mercuric Oxide Cell Commonly called the ‘mercury cell’, a type of alkaline primary cell with a positive electrode of mercuric oxide (often with manganese dioxide), a negative electrode of metallic zinc and either potassium or sodium hydroxide as electrolyte.

Milliamp-hours (mAh) The unit generally used to specify the storage capacity of smaller batteries. A battery with a capacity of 100mAh can supply 100mA for one hour, or 10mA for 10 hours etc. One mAh is the equivalent of 3.6 coulombs of charge.

Negative Terminal (Electrode) The terminal of a battery from which electrons flow in the external circuit when the cell discharges.

NiCad Battery The most common type of secondary cell/battery, which uses nickel hydroxide as the positive electrode, cadmium/cadmium hydroxide as the negative electrode and potassium hydroxide as the electrolyte.

Nominal Voltage The average terminal voltage of a cell or battery during its discharge.

Non-aqueous Batteries Cells that do not contain water, such as those with molten salts or organic electrolytes.

OC Voltage The terminal voltage of a cell or battery when open circuited — i.e., not supplying any significant load current.

Ohm's Law The formula that describes the amount of current flowing through a circuit. Voltage = Current � Resistance.

Open Circuit Condition of a battery which is neither on charge nor on discharge (i.e., disconnected from a circuit).

Open-Circuit Voltage The difference in potential between the terminals of a cell when the circuit is open (i.e., a no-load condition).

Overcharging Attempting to store more charge into a battery than its electrochemical system can safely absorb beyond its capacity. Overcharging can cause overheating and irreversible structural damage, including explosion.

Over-discharging Withdrawing too much energy from a battery, which can shorten its working life or in extreme cases cause irreparable damage.

Oxidation A chemical reaction that results in the release of electrons by an electrode's active material.

Parallel Connection The arrangement of cells in a battery made by connecting all positive terminals together and all negative terminals together, the voltage of the group being only that of one cell and the current drain through the battery being divided among the several cells.

Plates Another term meaning much the same as electrodes

Polarity Refers to the charges residing at the terminals of a battery.

Positive Electrode The electrode of a battery which normally has a shortage of electrons due to the internal chemical reaction.

Positive Terminal The terminal of a battery toward which electrons flow through the external circuit when the cell discharges.

Primary Battery (Cell) An electrochemical cell or battery which contains a fixed amount of stored energy when manufactured, and cannot be recharged after that energy is withdrawn.

Primary Cell A cell designed to produce electric current through an electrochemical reaction that is not efficiently reversible. Hence the cell, when discharged, cannot be efficiently recharged by an electric current. Note: When the available energy drops to zero, the cell is usually discarded. Primary cells may be further classified by the types of electrolyte used.

Rated Capacity The number of ampere-hours a cell can deliver under specific conditions (rate of discharge, end voltage, temperature); usually the manufacturer's rating.

Rechargeable Alkaline A variety of manganese-zinc alkaline cell designed to absorb the hydrogen gas released during recharging, and allow re-use as a secondary battery. Low in cost, but with very limited cycle lifetime

Recharging With secondary cells or batteries, the process of re-storing electrical energy after the battery is discharged — by driving a current back into it from an external source.

Rechargeable Capable of being recharged; refers to secondary cells or batteries.

Rechargeable Battery Any electrochemical cell or battery which can be recharged i.e., a secondary cell or battery.

Recombination State in which the gasses normally formed within the battery cell during its operation, are recombined to form water.

Reduction A chemical process that results in the acceptance of electrons by an electrode's active material. SLA Battery: The sealed lead-acid battery is a type of secondary battery derived from the original flooded lead-acid type. It has a positive electrode of lead oxide, a negative electrode of porous metallic lead and sulphuric acid as the electrolyte.

Seal The structural part of a galvanic cell that restricts the escape of solvent or electrolyte from the cell and limits the ingress of air into the cell (the air may dry out the electrolyte or interfere with the chemical reactions).

Sealed Dry Battery A cell or battery where the case can be effectively sealed to allow operation in any position without leakage of the chemical electrolyte.

Secondary Battery An electrochemical cell or battery which can be recharged.

Self Discharge Discharge that takes place while the battery is in an open-circuit condition. All batteries tend to discharge themselves even when not supplying energy, as a result of internal losses. The self-discharge rate describes this effect in terms of a percentage

Separator The permeable membrane that allows the passage of ions, but prevents electrical contact between the anode and the cathode.

Series Connection The arrangement of cells in a battery configured by connecting the positive terminal of each successive cell to the negative terminal of the next adjacent cell so that their voltages are cumulative.

Shallow cycling Repeatedly discharging a secondary battery by only a small proportion of its capacity before recharging again. Some types of battery prefer it, some don’t.

Shelf Life For a dry cell, the period of time (measured from date of manufacture), at a storage temperature of 21 degrees C (69 degrees F), after which the cell retains a specified percentage (usually 90%) of its original energy content.

Short-Circuit Current That current delivered when a cell is short-circuited (i.e., the positive and negative terminals are directly connected with a low-resistance conductor).

Silver Oxide Cell The silver oxide-zinc cell is an alkaline primary type. It uses silver oxide as the positive electrode and zinc as the negative electrode, with an electrolyte of either sodium or potassium hydroxide. They are mainly used in low-drain applications. Slow or Trickle Charging: Recharging a secondary battery at a rate of between 0.05C and 0.2C — i.e., over a period between 7 and 28 hours (charging 140% of nominal capacity).

Starting-Lighting-Ignition (SLI) Battery A battery designed to start internal combustion engines and to power the electrical systems in automobiles when the engine is not running. SLI batteries can be used in emergency lighting situations.

State of Charge (SOC) Condition of a cell in terms of the capacity remaining in the cell.

Stationary Battery A secondary battery designed for use in a fixed location.

Storage Battery An assembly of identical cells in which the electrochemical action is reversible so that the battery may be recharged by passing a current through the cells in the opposite direction to that of discharge. While many non-storage batteries have a reversible process, only those that are economically rechargeable are classified as storage batteries. Synonym: Accumulator; Secondary Battery. See Secondary Cell.

Storage Cell An electrolytic cell for the generation of electric energy in which the cell after being discharged may be restored to a charged condition by an electric current flowing in a direction opposite the flow of current when the cell discharges. Synonym: Secondary Cell. See Storage Battery.

Taper Charge A charge regime delivering moderately high-rate charging current when the battery is at a low state of charge and tapering the current to lower rates as the battery becomes more fully charged.

Terminals The parts of a battery to which the external electric circuit is connected.

Thermal Runaway A condition whereby a cell on charge or discharge will destroy itself through internal heat generation caused by high overcharge or high rate of discharge or other abusive conditions.

Trickle Charging A method of recharging in which a secondary cell is either continuously or intermittently connected to a constant-current supply that maintains the cell in fully charged condition.

Vent A normally sealed mechanism that allows for the controlled escape of gases from within a cell.

Voltage, cutoff Voltage at the end of useful discharge. (See Voltage, end-point.)

Voltage, end-point Cell voltage below which the connected equipment will not operate or below which operation is not recommended.

Voltage, nominal Voltage of a fully charged cell when delivering rated current.

Wet Battery (cell) An electrochemical cell or battery in which the electrolyte is in the liquid form.

Zinc-Air Cell A recently developed type of primary cell which has a very high energy density, but a relatively short working life. It uses a negative electrode of powdered zinc mixed with potassium hydroxide and a negative electrode of moist air.

Zinc Chloride Battery An enhanced version of the standard zinc-carbon primary battery, with about 50% higher capacity. The main difference is the use of zinc chloride as the electro

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