Leoch Battery UK has an enviable position of possessing a total of 100 collective years of staff experience in the battery industry.  From basic terms to more complicated technologies, you should find every aspect of batteries explained below, from A to almost Z!

Accumulator - 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 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 (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-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

Anode - 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.

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

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.

CA (Cranking Amps) - A rating used in the battery industry to define a battery’s ability to start an engine.

Capacity - 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.

Cathode - 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.

Cell - 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.

Charge - 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.

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

Conditioning - 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.

Corrosion - 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.

Cycle - One sequence of charge and discharge.

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

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.

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.

Discharge - 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.

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.

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.

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.

Gel – 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.

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

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

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.

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.

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)

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).

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. See Series Connection.

Polarity - 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.

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

Recombination - State in which the gases 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.

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 Battery - A maintenance-free battery with nonremovable vent caps.

Sealed Wet Cell Batteries - The maintenance-free version of the traditional flooded wet-cell (which requires occasional servicing). In a sealed design, gasses are contained within the battery casing and emissions are kept to an absolute minimum, meaning the battery can perform for the entirety of its service life without being topped up.

Secondary Battery - A battery made up of secondary cells. See Storage Battery; Storage Cell.

Self Discharge - Discharge that takes place while the battery is in an open-circuit condition.

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. See Parallel Connection.

Shallow Cycling - Charge and discharge cycles which do not allow the battery to approach it’s cutoff voltage.

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-Ciruit - 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.

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).

Smart Battery - A battery with internal circuitry designed to communicate information, such as capacity remaining, to the user or to other parts of the application's circuit.

Smart Charger - A charger that fully discharges a battery before recharging it to prevent a memory effect from occurring.

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) – The opposite concept to Depth of Discharge.

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

Stop-Start Technology – A system that automatically shuts down and restarts an engine to reduce the amount of time it spends idling, therefore reducing fuel consumption and emissions.

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.

Stratification - A condition in which the concentration of acid is greater at the bottom of the battery than at the top. Normally caused by continued undercharging.

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.

Tubular Plate Batteries - In comparison to a flat plate, a tubular plate is a more rigid structure which is more resistant to the continued stress of deep cycling. Electrolyte is piped into the tubes and is protected and utilised more thoroughly than in flat plate batteries where the electrolyte is exposed.

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

Volt - The unit of measurement of electromotive force, or difference of potential, which will cause a current of one ampere to flow through a resistance of one ohm. Named for Italian physicist Alessandro Volta (1745-1827).

Voltage, cutoff - Voltage at the end of useful discharge. The prescribed lower-limit voltage at which battery discharge is considered complete (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.

VRLA (valve-regulated lead-acid) - More commonly known as a sealed lead-acid (SLA), gel cell, or maintenance free battery (MF), is a type of lead-acid rechargeable battery. Due to their construction, the Gel and AGM types of VRLA do not contain high levels of liquid compared with the standard counterparts, and consequently can be mounted in any orientation, and do not require constant maintenance. They are widely used in large portable electrical devices, off-grid power systems and similar roles, where large amounts of storage are needed at a lower cost than other low-maintenance technologies like lithium-ion.

Watt - A measurement of total power. It is amperes multiplied by volts. 120 volt @ 1 amp = 12 volts @ 10 amps.

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