Technical Glossary
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A
Ampere-Hours
Product of current in amperes multiplied by the time current is flowing. Capacity of a cell or battery is usually expressed in ampere-hours. Abbreviated as Ah.
Anode
Electrode at which an oxidation reaction (loss of electrons) occurs. In secondary cells, either electrode may become the anode, depending upon direction of current flow. The negative electrode is the anode on discharge.
B
Battery
One or more electrochemical cells electrically interconnected to form one unit and having provisions for external electrical connections.
Battery Case
Battery box or enclosure which contains cells, connectors, and associated hardware.
C
C
Rated capacity of the cell or battery. Cell charge/discharge current is often specified in terms of a multiple of C. (For example the 0.1C current for a cell rated at 1.4 Ah is 140mA.)
C Rate
Charge or discharge current in amperes that is numerically equal to the rated capacity of a cell in ampere-hours.
Capacity
Amount of charge available from a battery or cell. Measured in ampere-hours. There are various sub definitions of capacity as listed below depending on the conditions under which it is measured.
Cell
Electrochemical unit, composed of positive and negative electrodes, separator, and electrolyte, which is capable of storing electrical energy. When encased in a container and provided with electrical terminals, the cell is the basic "building block" of a battery.
Charge
Return of electrical energy to a battery.
Cycle Life
Number of cycles a battery survives before its capacity falls below the acceptable level.
D
Deep Cycling
Charge/discharge cycle where approximately 100 per cent of the available capacity is withdrawn at a low rate.
Deep Discharge
Condition where a cell is fully discharged at a low rate resulting in removal of all dischargeable capacity.
Depth of Discharge
Capacity removed from a battery divided by its actual capacity, expressed as a percentage.
Discharge Rate
Rate at which current is withdrawn from a battery. May be expressed in absolute terms (amps) or in relative terms (as a fraction or multiple of the C rate).
E
Electrode
Conducting body within the cell in which the electrochemical reactions occur. It normally consists of the active material and the structures necessary to collect the charge and to support the active material as required.
Electrolyte
Medium, usually liquid, within the cell that permits the movement of ions between electrodes. Sealed-lead cells contain a dilute sulphuric acid electrolyte.
Energy Density
Energy stored within a battery or cell as a function of weight (gravimetric energy density - watt-hours per gram) or volume (volumetric energy density - watt-hours per cubic centimetre). Rate dependant.
F
Float Charge
Charging for batteries used in backup applications that reduces the charge rate to prolong life while maintaining the battery in a ready-to-serve condition.
Fast Charging
Rapid return of energy to a battery, usually at the 1C rate or greater.
G
Gel Battery
A type of VRLA battery where the electrolyte is immobilized as a gel, providing enhanced performance in deep discharge applications and better resistance to vibration.
H
High-Rate Discharge
Discharge at currents greater than the C rate, typically used in applications requiring short bursts of high power.
I
Internal Resistance
Apparent resistance value calculated from the cell voltage difference between high rate and low rate discharge.
Interconnections
Method of providing electrical linkage between cells in a battery. May be external in the case of single cells or internal in the case of monobloc batteries.
J
Joule
A measure of work, energy or cell capacity. For electrical energy, one Joule is one Amp at one Volt for one Second, or one Watt Second. 1 Wh = 3.6kJ.
K
Kilovolt-Ampere (KVA)
One thousand volt-amperes. The output of a UPS is typically rated in volt-amperes.
K-ion Battery
A potassium-ion battery or K-ion battery (abbreviated as KIB) is a type of battery and analogue to lithium-ion batteries, using potassium ions for charge transfer instead of lithium ions.
L
Lead Dioxide
Active material for the positive electrode in a sealed-lead battery.
Lead Sulfate
Chemical compound formed at both positive and negative plates of a lead battery when the battery is discharged.
Life
Duration of satisfactory performance, measured in years (float life) or in the number of charge/discharge cycles (cycle life).
M
Maintenance-Free Battery
Battery that does not require addition of water. Often applied to sealed recombining cells, but also used for flooded batteries carrying excess electrolyte so that water addition is not required over the course of life.
Monobloc Battery
Sealed-lead battery constructed as an integrated unit rather than assembled from single cells.
N
Negative Electrode
Electrode which has an electrical potential below that of the other electrode during normal cell operation. The sponge-lead electrode is the negative electrode for the sealed-lead battery.
Nominal Capacity
Typical capacity; greater than the rated capacity which is a minimum value.
Nominal Voltage
Midpoint voltage observed across battery during discharge at a selected rate, usually at the 0.2C or 0.1C rate.
O
Open-Circuit Voltage
Voltage of a battery with no load applied to it.
Overcharge
Normal application of charge current after the battery has reached full charge.
Overdischarge
Discharge past the point where the full capacity of the cell has been obtained.
P
Parallel
Electrical term used to describe the interconnection of batteries in which all like terminals are connected together.
Positive Electrode
Electrode which has an electrical potential higher than that of the other electrode during normal cell operation.
Primary Cell
Cell designed to be used only once, then discarded. It is not capable of being returned to its original charged state by the application of current.
Q
Quick Charge
Rate of charging which returns full capacity reasonably quickly, but may be sustained into overcharge with a specially designed cell.
R
Rated Capacity
Capacity value shown in the specification sheet. The minimum expected capacity when a new, but fully formed, cell is measured under standard conditions.
Recharge
Return of electrical energy to a battery.
Recombination
Chemical reaction of gases at the electrodes to form a non-gaseous product.
S
Sealed Cell
Cell where the internal environment is controlled and isolated from the external atmosphere, often by use of some form of vent valve.
Secondary Battery
Battery system which is capable of repeated use through employing chemical reactions that are reversible; i.e., its discharge capability may be restored by supplying electrical current to recharge the cell.
Self-Discharge
Spontaneous decomposition of battery material from charged to discharged states.
Separator
Material which provides physical separation and electrical insulation between plates of opposite polarity.
State of Charge
Residual capacity expressed as a per cent of fully-charged capacity.
T
Terminal
Location on the cell or battery exterior that is electrically connected to either the positive or negative electrode.
Trickle Charge
Low-rate charge used to keep battery fully charged after charging at higher rate.
U
UN 38.3
UN 38.3 presents a combination of significant environmental, mechanical, and electrical stresses designed to assess lithium batteries' ability to withstand the anticipated rigors incurred during transport.
UL 94:V0
UL 94, the Standard for Safety of Flammability of Plastic Materials for Parts in Devices and Appliances testing. UL 94 rating V-0 definition means burning stops within 10 seconds on a vertical part allowing for drops of plastic that are not inflamed.
V
Valve-regulated Lead Acid (VRLA)
Maintenance-free lead acid battery recombines oxygen (positive plate) with hydrogen (negative plate) on charge; valve regulates pressure by release of excess gases. Repeated venting will lead to dry out.
Voltage (V)
Electric energy potential per unit charge. 1V = 1J/Coulomb. (1,000 joules = 0.277Wh).
Volumetric Energy Density
Also known as energy density; specifies energy storage in volume (Wh/l).
W
Watt (W)
Unit of power; ampere (A) times volt (V) equals watts (W).
Watt-hour (Wh)
Unit of electrical energy equivalent to a power consumption of one watt for one hour (One watt-hour = 3600 Joules). Multiplying a battery voltage (V) by the rated capacity (Ah) gives the battery energy in Wh. Example: 14.4V x 2.5 Ah = 36 Wh.