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| A |
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Accumulator :
An electrochemical device that can transform electrical energy into stored chemical energy and by reversing the process, release energy again.
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Active Material :
The material which reacts chemically to produce electric energy when the cell discharges, and which is restored to its original state during the charge.
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Ampere hours [Ah] :
Product of the current strength (measured in amperes) and the duration (in hours) of the current. The quantity of electricity (capacity) of a battery or cell is usually expressed in ampere hours. Ah is the abbreviation.
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Ampere [A] :
Basic unit of electrical current strength.
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| B |
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Battery :
Two or more secondary cells connected together and used as a source of electrical energy.
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Battery charger :
Unit supplying electrical energy to a rechargeable battery.
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Battery, primary :
A battery which is not intended for recharging.
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Battery, rechargeable (or secondary) :
A battery which is rechargeable.
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Button Cell :
A cell of circular cross-section in which the overall height is less than the diameter .A sealed nickel-cadmium button cell comprises positive and negative electrodes, a separator, alkaline electrolyte and metal case.
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| C |
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C :
Rated capacity of a cell or a battery. The charging and discharging current of a cell is often expressed as a multiple of C. (Example: The 0.1 C current for a cell with a rated capacity of 1.4 Ah is 140 mA).
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Cadmium :
Chemical element (Cd) that belongs to the heavy metals. In battery technology, cadmium, cadmium oxides and cadmium hydroxide are used in the cadmium electrodes found in nickel-cadmium accumulators and in normal elements.
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Capacity :
The quantity of electricity or electric charge delivered by a fully charged cell or battery, under specified conditions (rated capacity). The capacity depends on the battery temperature and the discharging current. Note. The International System unit for capacity is the coulomb (ampere x second) but in practice, cell or battery capacity is expressed in ampere-hours (Ah).
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Capacity rated :
The capacity that is typically delivered when used under normal conditions (e.g. 20-hour capacity in Ah, reserve capacity during discharge with 25 A in min).
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Cell :
The smallest unit of a battery, consisting of a positive and a negative electrode, a separator and the electrolyte. The capacity of a cell is determined by its size. The cell voltage, however, depends on the electrochemical system of the element. A single nickel-cadmium or nickel-metal-hydride cell is rated at 1.2V. Two or more cells are usually combined to form a battery.
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Cell, cylindrical :
Cells whose heights are equal to or greater than their diameters. For the most part, this refers to primary cells as well as closed spiral nickel-cadmium cells and closed lead cells.
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Charge :
An operation during which a cell or battery receives electrical energy from an external circuit.This electrical energy is converted into chemical energy.
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Charge Rate :
The current at which a cell or battery is charged Generally expressed as a function of rated capacity. For instance, a charge rate of 0.4 A from a 4 Ah cell or battery is equal to C/10 or 0.1 C.
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Charging current :
The current flowing at the time a battery is being charged. It depends on the charge state, the charging method and the temperature.
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Constant current charge :
Constant current charging involves charging with a constant charging current and variable charging voltage. This process is normally used for Nickel-Cadmium and Nickel-Metal Hydride cells or batteries.
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Constant Voltage Charge :
A charge during which the voltage across the battery terminals is maintained at a constant value. It is the most frequently used method for closed lead batteries or lithium-ion batteries.
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Current :
The movement of electrical charges in an electrical field. Battery technology only uses direct current.
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Cut-Off Voltage :
The specified voltage at which a discharge of a cell or battery is considered finished (final voltage).
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Cutoff, voltage and temperature dependent (VTCO) :
A way of switching the charging current of a battery from highest-speed charging to peak charging by means of a control circuit in the battery charger. This circuit is activated by the battery voltage or battery temperature.
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Cycle :
A sequence of a discharge followed by a charge, or a charge followed by a discharge of a battery under specific conditions.
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Cycle Life :
The total number of cycles before a cell or battery becomes nonfunctional for a definite use.
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Cylindrical Cell :
Cell of circular cross-section in which the overall height is greater than the diameter A sealed nickel-cadmium cylindrical cell consists of positive and negative electrodes, a separator, alkaline electrolyte, metal case and sealing plate with a self-sealing vent.
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| D |
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Delta V :
Detecting the voltage drop which indicates a cell is fully charged.
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Direct current :
Current, whose polarity does not change over time (e.g. current from an electrochemical power source).
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Discharge :
An operation during which a battery delivers current to an external circuit by conversion of chemical energy into electrical energy.
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Discharge Rate :
The current at which a battery is discharged.
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Discharge Voltage :
The voltage between the terminals of a cell or battery under load, during discharge.
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Electrode :
The positive or negative plate holding active materials.
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Electrolyte :
The liquid which provides ionic conductivity between the positive and negative electrodes.
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| F |
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Final Voltage :
The specified voltage at which the discharge of a battery is considered finished (cut-off).
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| H |
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High current charging :
Charging with a current strength greater than 1C.
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High current discharging :
Discharging with a current strength greater than 3C or 5C.
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| I |
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IEC :
International Electrochemical Commission. Sets worldwide standards for the electromechanical industry. The main IEC standards applicable to sealed nickel-cadmium and nickel-metal hydride cells and batteries are IEC 60285 for Ni-Cd cylindrical cells IEC 60509 for Ni-Cd button cells IEC 61436 for cylindrical and prismatic Ni-MH cells.
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| L |
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Lead battery :
An accumulator in which the electrodes consist primarily of lead, whereas the electrolyte consists of diluted sulfuric acid.
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Lithium-ion battery (Li-ion) :
Type of accumulator which has a high gravimetric and volumetric energy density. The cell voltage (open circuit voltage) is governed by the electrode pairing and, for a Li2MnO2 / C combination for example, has a value of 3 V or 4 V, depending on the type of manganese dioxide used. This system is therefore recommended for applications such as mobile telephones, video cameras.
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Load :
Describes the current in amperes with which a fully charged battery can be loaded over a defined period and at a defined temperature without the voltage falling below a pre-specified cut-off voltage.
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| M |
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Mass, active :
The material in the electrodes that takes part in the charging and discharging reactions. In a nickel-cadmium cell, nickel hydroxide and cadmium hydroxide are used as active mass at the positive and negative electrodes. In the lead cell, lead dioxide and sponge lead serve as the active mass at the positive and negative electrodes. The sulfuric acid in the lead cell which functions as an electrolyte can also be considered as an active mass, because it also takes part in the cell reaction.
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Memory effect :
If nickel-cadmium batteries are recharged before they have been fully discharged, cadmium crystals can form at their negative electrode. This results in an unwanted second discharge stage. The battery stores this stage as a discharge stage for the next cycle in its memory, even though capacity is still available 'below this'. During the next discharge process, the battery only remembers this reduced capacity. Any further incomplete discharge cycles which follow will aggravate the situation still further and the performance of the battery will continue to fall. Nickel-cadmium cells should therefore be discharged fully at occasional intervals. This prevents the 'memory effect' from occurring and prolongs the service life of the cell or battery. This effect does not occur with nickel-metal-hydride batteries. Consequently, these batteries can be discharged and recharged without problem.
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| N |
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Nickel-Cadmium battery (Ni-Cd) :
An alkaline accumulator in which the positive mass consists primarily of nickel hydroxide and the negative mass of cadmium.
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Nickel-Metal Hydride (Ni-MH) :
New battery technology providing increased volumetric capacity. An original system comprising a nickel positive electrode and metal hydride (MH) negative electrode.
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Nominal Voltage :
A suitable approximate value of voltage used to identify the voltage of a cell or battery. The nominal voltage of a single nickel-cadmium or nickel-metal hydride cell is 1.2V.
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| O |
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Open circuit voltage (OCV) :
The open circuit voltage is the voltage of an accumulator without external load. It is generally higher than the nominal voltage.
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Overcharge :
Continued charging after the full charge of a cell or battery.
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| P |
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Parallel connection :
Connecting all the positive or all the negative poles of several batteries. This increases the capacity of a battery network while maintaining a constant voltage.
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Paste :
Mixtures of various compounds, (e.g. lead oxide and water, sulfuric acid) that are used to coat positive and negative lead battery grids. A distinction is made between positive and negative pastes depending on the recipe. These pastes are then transformed into positive and negative cured masses.
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Plate :
An electrode consisting of active mass and conductive carrier.
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Primary Cells :
A cell which is not intended for recharging (usually carbon-zinc or alkaline).
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Prismatic cell :
Differs in external appearance from the round cell. Prismatic cells are block-shaped and are therefore very flat.
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| R |
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Rated Capacity :
The quantity of electricity, as defined by the manufacturer, delivered by a cell or a battery under specified conditions after a full charge ( C/5 discharge rate to a final voltage of 1V at 20°C, after storing 1 hour and charging 16 hours at C/l0).
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Reaction, reversible :
Chemical reaction that can take place in either direction (oxidation or reduction). The cell reaction must be reversible in order to use a secondary battery.
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Rechargeable battery :
A battery which is rechargeable.
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Resealable Safety Vent :
The resealable safety device built into a cell to prevent dangerously high internal pressure.
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Round cell :
Round cell, in contrast to prismatic cell.
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| S |
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Sealed Cells :
A cell which remains closed and does not release either gas or liquid when operated within the limits of charge and temperature specified by the manufacturer The cell's electrolyte cannot be topped up.
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Secondary battery :
Rechargeable battery.
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Self-Discharge :
Loss of chemical energy due to spontaneous reactions within the battery when not connected to an external circuit. Rate of self discharge is defined by percentage of loss of capacity per unit of time It varies according to cell technology and temperature.
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Separator :
A device used for the physical separation and electrical isolation of electrodes of opposing polarities.
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Series connection :
Connection of the positive terminal of a cell / battery to the negative terminal of the next cell / battery. This increases the voltage of the battery network while keeping the capacity constant.
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Standard Charge :
The normal charge used to recharge a cell or battery in 16 hours. Sometimes called an overnight charge.
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| T |
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Temperature Cut-Off :
A temperature sensing method which detects heat rise in a cell at overcharge and either switches the charger off or to a lower rate of charge.
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Terminal :
Polarity-specific component on the battery for making a (detachable) connection with the consumer.
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Typical capacity :
Average quantity of electricity delivered by a cell or a battery, under the same specified conditions as the rated capacity, after a full charge.
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| V |
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Valve :
A device allowing gas to escape when inner pressure is too high, while preventing air from entering.
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Venting valve, recloseable :
Safety valve in the cell which opens in case of overpressure and closes again automatically when normal pressure has been restored.
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Volt :
Unit of measurement for electrical voltage. Abbreviation V.
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Voltage and temperature dependent cut-off (VTCO) :
A way of switching the charging current of a battery from highest-speed charging to peak charging by means of a control circuit in the battery charger. This circuit is activated by the battery voltage or battery temperature.
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Voltage Cut-Off :
A voltage sensing device which will end a charge or discharge at a preset voltage value.
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Voltage, nominal :
The battery's average voltage during discharging with a low current strength. The manufacturer specifies the value on the accumulator (e.g. Ni-Cd = 1.2 V per cell).
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| W |
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Welding :
Connecting together two or more plates to form a plate block by welding on a connecting strap.
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