Leoch Battery UK




A rechargeable battery or cell (see also Secondary battery).

Actual Capacity or Available Capacity

The total battery capacity, usually expressed in ampere-hours or milliampere-hours, available to perform work. The actual capacity of a particular battery is determined by a number of factors, including the cut-off voltage, discharge rate, temperature, method of charge and the age and life history of the battery.

AGM (Absorbent Glass Mat)

A type of separator material composed of glass microfibers that absorb and retain the electrolyte, leaving no free liquid in the cell to spill.

Ampere Hour (Amp-hrs, Ah)

This term is used to signify the electrical storage capacity of a battery. One ampere-hour is equal to a current of one ampere flowing for one hour.

Ampere or Amp (Amp, A)

An Ampere or an Amp is a unit of measurement for an electrical current. One amp is the amount of current produced by an electromotive force of one volt acting through the resistance of one ohm. Named for the French physicist Andre Marie Ampere. The abbreviation for Amp is A but its mathematical symbol is "I". Small currents are measured in milli-Amps or thousandths of an Amp.

Ampere-Hour Capacity

The number of ampere-hours which can be delivered by a 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.


During discharge, the negative electrode of the cell is the anode. During charge, that reverses and the positive electrode of the cell is the anode. The anode gives up electrons to the load circuit and dissolves into the electrolyte.

Aqueous Batteries

Batteries with water-based electrolytes. The electrolyte may not appear to be liquid since it can be absorbed by the battery’s separator.

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.



An electrochemical device used to store 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 AA battery.

Battery Charger

A device capable of supplying electrical energy to a battery.

Battery Types

There are, in general, two type 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-Charge Rate

The current expressed in amperes (A) or milli amps (mA) at which a battery is charged.


CA (Cranking Amps)

A rating used in the battery industry to define a battery’s ability to start an engine.


The capacity of a battery is a measure of the amount of energy that it can deliver in a single discharge. Battery capacity is normally listed as amp-hours.


Is an electrode that, in effect, oxidizes the anode or absorbs the electrons. During discharge, the positive electrode of a voltaic cell is the cathode. When charging, that reverses and the negative electrode of the cell is the cathode.

CCA (Cold Cranking Amperes)

A rating used in the battery industry to define a battery’s ability to start an engine in cold temperatures. Provides a general idea of how a battery is designed to perform in the most demanding of conditions.


An electrochemical device, composed of positive and negative plates and electrolyte, which is capable of storing electrical energy. It is the basic “building block” of a battery.


The conversion of electric energy, provided in the form of a current, into chemical energy within the cell or battery.

Charge Rate

The amount of current applied to battery during the charging process. This rate is commonly expressed as a fraction of the capacity of the battery. For example, the C/2 or C/5.


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


The process of restoring capacity to a battery by deeply discharging and recharging the battery multiple times.

Constant-Current Charge

A charging process in which the current applied to the battery is maintained at a constant value.

Constant-Voltage Charge

A charging process in which the voltage applied to a battery is held at a constant value.


The chemical or electrochemical reaction between a material and its environment producing a deterioration of the material and its properties.

Cutoff 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 maximum useful capacity of the battery is realized. The cutoff voltage varies with the type of battery and the kind of service in which the battery is used. A device that is designed with too high a cutoff voltage may stop operating while the battery still has significant capacity remaining.


One sequence of charge and discharge.

Cycle Life

For rechargeable batteries, the total number of charge/discharge cycles the cell can sustain before it’s capacity is significantly reduced. End of life is usually considered to be reached when the cell or battery delivers only 80% of rated ampere- hour capacity. The cycle of a battery is greatly influenced by the type depth of the cycle (deep or shallow) and the method of recharging. Improper charge cycle cutoff can greatly reduce the cycle life of a battery.


The repeated charge/discharge cycle of a battery. Some batteries are rated according to their ability to cycle.


Deep Cycle

A cycle in which the discharge is continued until the battery reaches it’s cut-off voltage, usually 80% of discharge.

Deep Cycle Battery

Lead-acid batteries designed to be regularly deeply discharged using most of its capacity. A deep cycle battery is designed to provide a steady amount of current over a long period of time.

Deep Discharge

The withdrawal of all electrical energy to the end-point voltage before the cell or battery is recharged.

Depth of Discharge (DOD)

The amount of energy that has been removed from a battery. Usually expressed as a percentage of the total capacity of the battery. For example, 80% DOD means that eighty percent of the energy has been discharged, so the battery now holds only 20% of its full charge.

Direct Current (DC)

The type of electrical current that a battery can supply. Whilst household electricity known as alternating current (AC) provides electric in the form of a wave, the power output from a car battery appears much closer to a straight line. Essentially, in a direct current power source, the electrons flow in a single direction.


The conversion of the chemical energy of the battery into electric energy. When a battery is discharging, it is delivering a current.

Dry Cell

A primary cell in which the electrolyte is absorbed in a porous medium, or is otherwise restrained from flowing.

Dry Charged Battery

A type of battery in which both the positive and negative plates are formed and charged in acid baths before being dried and assembled. The battery is activated once electrolyte is added, at which time the battery will give instant current and be ready for use.



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.


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.


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.

Energy Density

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


Float Charging

Method of recharging in which a secondary cell is continuously connected to a constant-voltage supply that maintains the cell in fully charged condition. Typically applied to lead acid batteries.

Flooded cell type battery

A form of rechargeable battery in which the battery plates are immersed in liquid electrolyte (battery acid).


Galvanic Cell

A combination of electrodes, separated by electrolyte, that is capable of producing electrical energy by electrochemical action.


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.


Electrolyte liquid that has been immobilized by the addition of fine silica to create a gel like substance and avoid spillage. Provides many of the same advantages as AGM.


A framework that supports the active material of a battery plate and conducts current.


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Internal Resistance

The resistance to the flow of an electric current within the cell or battery.


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Lead Acid Battery

The oldest type of rechargeable battery. Relatively inexpensive, lead acid batteries are favoured for use in cars and other internal combustion vehicles as they can deliver a high ‘surge power’ (the initial energy required to get the engine started). Modern improvements have resulted in more stable batteries which are less prone to leakage and therefore safer. These include gel and AGM batteries.


Maintenance Free Battery (MF)

A battery type that requires no water servicing during its lifetime of use.

MCA (Marine Cranking Amps)

The same test procedure as Cold Craning Amps except that the test temperature is 32F. (This test is done warmer as a car is expected to operate in more severe operating temperatures)

Memory Effect

A phenomenon in which a cell, operated in successive cycles to less than full, depth of discharge, temporarily loses the remainder of its capacity at normal voltage levels (usually applies only to Ni-Cd cells). Note, memory effect can be induced in NiCd cells even if the level of discharge is not the same during each cycle. Memory effect is reversable.


Negative Terminal

The terminal of a battery from which electrons flow in the external circuit when the cell discharges.

Nonaqueous Batteries

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


Ohm’s Law

The formula that describes the amount of current flowing through a circuit. In a given electrical circuit, the amount of current in amperes (I) is equal to the pressure in volts (V) divided by the resistance, in ohms (R). Ohm's law can be shown by three different formulas:
To find Current I = V/R
To find Voltage V = I x R
To find Resistance R = V/I

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).


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. See Series Connection.


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

Positive Terminal

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

Primary Battery

A battery made up of primary cells. See Primary Cell.

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.


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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.


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



A condition that occurs when a short electrical path is unintentionally created. Batteries can supply hundreds of amps if short-circuited, potentially melting the terminals and creating sparks.


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Wet Cell

A cell, the electrolyte of which is in liquid form and free to flow and move.


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