Glossary of Battery Terms

Rev 3: 04/26/2023


Aggregate lithium content:  The sum in grams of the lithium metal in all of the cells contained in a primary battery pack.
Anode:  The negative (-) electrode of a cell.
Battery:  One or more cells which are electrically connected together by permanent means, including case, terminals, wiring and marking.   A single cell battery, under the UN Model Regulations of Tests and Criteria (See UN38.3 Tests), regardless of whether the unit is termed a "battery" or a "single cell battery", meets the definition of a "cell".
BMS:  BMS is an acronym for Battery Management System which is the circuit that controls the battery icon in a laptop computer and the charge status indicator in a battery pack.

Button Cell:   A small round or elliptical cell whose diameter is greater than its height.  The most common button cells are Nickel-Metal Hydride cells made by Varta and Gold Peak.
Capacity:  Capacity is the product of the discharge current (Amps (A) or milli Amp ( mA) and the discharge time (h) at a given load and is expressed in Amp-Hours (Ah) or milli Amp-Hours (mAh).
Cathode:  The positive (+) electrode of a cell.
Cell:  A single encased electrochemical unit (one positive and one negative electrode) which exhibits a voltage differential across its two terminals.  Under the Model Regulations of Tests and Criteria (See UN38.3 Tests), to the extent the encased electromechanical unit meets the definition of a "cell" herein, is a "cell", not a "battery", regardless of whether the unit is termed a "battery" or a "single cell battery" outside of the Model regulations.

CE Mark:  The CE mark (Abbreviation of Conformité Européenne) is a mandatory conformity mark for products placed on the market in the European Community.   With the CE mark on the product, the manufacturer ensures that the product conforms with the requirements of the applicable EC directive.  In the case of batteries, they are below a voltage threshold and do not emit electromagnetic radiation (Radio waves); and they are also exempt, at the present time, from the RoHS requirements as defined in the EU Battery Directive 2006/66/EC.
Chemistry:  Refers to the basic material of the negative electrode. Example: Zinc, Lithium, Nickel.
Closed circuit voltage - CCV:  Voltage across the terminals of a battery under load when there is external current flowing.   Note:  The CCV is lower always than OCV because there is a voltage drop within the cell(s) due to the internal resistance (impedance) of the cell.
Coin cells:  A small cell whose diameter is greater than its height.  Coin cells are typically lithium chemistry.
Cycle:   One sequence of fully charging and fully discharging a rechargeable cell or battery.
Disassembly:  A vent or rupture where solid matter from any part of the cell or battery penetrates a wire mesh screen (annealed aluminum wire with a diameter of 0.25mm and grid density of 6 to 7 wires per cm) placed 25cm away from the cell or battery.

Discharge:  Operation during which a battery delivers current to an external circuit or load.
Discharge characteristics - Discharge curve:  Graphical representation of the change in output voltage over time under various loads and/or ambient temperature
Electrolyte:  Medium in a battery which causes ions to move to create an electrochemical reaction. Either water or non-aqueous solution is used as solvent. The latter is called non-aqueous electrolyte solution, either organic or inorganic.
End-point voltage:  Specified closed circuit voltage at which a cell is terminated.  Also referred to as “cutoff” or “final” voltage.
Energy Density:  Available energy of a battery per unit volume or unit weight. The former is called volumetric energy density (Wh/l); the latter gravimetric energy density (Wh/kg).

Equivalent Lithium Content:   This is the method that the U.S. DOT previously used to measure the size of a lithium-ion cell and battery.   For a lithium-ion cell, the product of the rated capacity, in ampere-hours times 0.3, with the result expressed in grams.  The equivalent lithium content of a battery equals the sum of the grams of equivalent lithium content contained in the component cells of the battery.  This definition was replaced in 49CFR 173.185 on 2/6/2015 by Watt-Hours (Wh) to be in harmony with the International Civil Aviation Organization (ICAO).   
Expiration date:  Expiration of guarantee period of a primary battery determined by each manufacturer conforming to the IEC (International Electrotechnical Commission) .  Because a secondary battery can be used over again by charging, there is no expiration date.

GHS:   The Globally Harmonized System of Classification and Labeling of Chemicals (GHS) is a new United Nations standard that has become the basis of the new U.S. Occupational Safety and Health Act (OSHA) Safety Data Sheet (SDS) standard under 29CFR Part 1910.1200.  The SDS replaces the legacy MSDS.  OSHA required that by December 1, 2013 workers be trained in the new label element and Safety Data Sheet (SDS) format, consisting of 16 specific sections in harmony with the GHS standards.   Fedco Batteries has updated to the new SDS format.

Host Device:  The equipment that the battery pack is designed to operate.  This can be a totally portable device or one that operates from power line voltage.

IATA:  The International Air Transport Association (IATA), pronounced Eye-Ah-Ta, is an international trade group comprised of some 240 airlines and is headquartered in Montreal Quebec, Canada.  IATA's stated mission is to represent, lead and serve the airline industry.  The main aim of IATA is to provide safe and secure transportation is its passengers. 
IATA annually publishes the IATA Dangerous Goods Regulations (DGR), which are modeled after the ICAO Technical Instructions. (The 64th Edition becomes effective on 1-1-2023.)  Working closely with governments in the development of the regulations, including ICAO and other national authorities, IATA ensures that the rules and regulations governing dangerous goods transport are both effective and efficient.  The U.S. Department of Transportation (DOT) does not officially recognize or enforce the IATA Dangerous Goods Regulations.  Instead, the DOT has the authority to enforce the ICAO Technical Instructions

ICAO:  The International Civil Aviation Organization (ICAO), pronounced Eye-Kay-O, is a specialized agency of the United Nations, and  is headquartered in Montreal Quebec, Canada. 
The Dangerous Goods Panel (DGP) of ICAO is responsible for periodic updating of Annex 18 to the Convention on International Civil Aviation and the Technical Instructions on the Safe Transport of Dangerous Goods by Air (Technical Instructions).  Virtually all shipments of hazardous materials transported internationally by air are transported in accordance with the ICAO Technical Instructions as well as U.S. domestic air shipments.

Internal Impedance:  Internal impedance of a cell that increases as the cell ages or is discharged.  This is measured by a 1000Hz bridge.  Also called internal resistance.  Typical internal impedance of a cell is <100µOhms.
Internal short circuit:  Direct contact electrically between the positive electrode and negative electrode of a cell caused by damage to the separator or gasket, or the presence of metallic contamination.   The battery cell will become useless and may, in fact, vent or explode.
Leakage:   The escape of material from a cell or battery.  The most common leakage is electrolyte, which is very flammable and/or very corrosive.
Lithium content:  The mass, in grams, of lithium metal contained within the anode of lithium metal or lithium alloy cell.   These are, for the most part, primary cells.  The lithium content of a lithium battery is the sum of the lithium mass of the anodes of all the cells in the battery.  See Aggregate lithium content and Equivalent lithium content.
Load:  External device or method through which a battery is discharged.

MSDS:  Material Safety Data Sheets are required by the Occupational Safety and Health Administration's (OSHA) Hazardous Communication Program to identify substances that are used or contained in materials that may be hazardous to human health.   Although batteries are classified as "articles" and do not require MSDS,  cell manufacturers and battery pack manufacturers normally provide them.   In 2013 OSHA has revised their hazardous communication program to be in harmony with the Global Harmonized System (GHS) and has renamed the safety sheets to Safety Data Sheets (SDS).

Nominal voltage:  Approximate midpoint voltage, during discharge, of a fully charged battery cell.  This varies by chemistry with common examples and nominal voltages below:

  • Alkaline manganese Primary – 1.5V
  • Zinc carbon Primary – 1.5V
  • Lithium carbon monofloride Primary - 3.0V
  • Lithium iron disulfide - 1.5V
  • Lithium manganese dioxide Primary – 3.0V
  • Lithium sulfur dioxide Primary - 2.9V
  • Lithium thionyl chloride Primary – 3.6V
  • Mercury Oxide Primary (Now Banned) - 1.352V
  • Silver Oxide Primaary - 1.55V
  • Zinc-Air Primary - 1.45V
  • Nickel cadmium Rechargeable – 1.2V
  • Nickel metal-hydride Rechargeable – 1.2V
  • Nickel zinc Rechargeable – 1.6V
  • Lead / Lead acid Rechargeable - 2.0V
  • Lithium-ion Rechargeable - 3.7V
  • Lithium-iron phosphate Rechargeable - 3.2V
  • Lithium-prismatic Rechargeable – 3.7V
  • Lithium-polymer  Rechargeable  – 3.7V

Open circuit voltage - OCV:  Voltage across the terminals of a battery when no external current is flowing and not under load.  The OCV is typically higher than a battery's nominal voltage.
Over discharge:  To discharge a cell to a voltage below its end-point voltage.

Packing Instructions:  The ICAO Technical Instructions and the IATA Dangerous Goods Regulations require compliance to specific Packing Instructions (PIs) in order to offer lithium-metal primary cells and batteries and lithium-ion rechargeable batteries for transport in passenger and cargo aircraft.    (See "Lithium Battery Packing Instructions"  under "Battery Shipping Regulations" under the "Resources" button.)
   PI 965:  UN3090 Lithium-metal primary cells and batteries. 
   PI 966:  UN3091 Lithium-metal primary cells and batteries shipped with equipment.
   PI 967:  UN3091 Lithium-metal primary cells and batteries installed in equipment.
   PI 968:  UN3480 Lithium-ion rechargeable cells and batteries.
   PI 969:  UN3481 Lithium-ion rechargeable  batteries shipped with equipment.
   PI 970:  UN3481 Lithium-ion rechargeable batteries installed in equipment.

Protection Circuit Module - PCM:  The safety circuit installed in all lithium-ion, lithium-polymer and lithium-iron phosphate rechargeable battery packs to control over-charge, over-discharge and short circuit of the cells within the pack.  This circuit is mandated by the UN Manual of Tests and Criteria, paragraph 38.3, Rev. 5.

Protective Devices:   Devices, such as fuses, diodes and current limiters which interrupt the current flow, block the current flow in one direction or limit the current flow in an electrical circuit.
Primary:  A cell or battery which is not designed to be charged and discharged.  ie: Single use.
Rated Capacity:  The capacity, in ampere-hours (Ah) of a cell or battery as measured by subjecting it to a load, temperature and cut-off voltage point specified by the manufacturer.

RoHS:  Restriction of the use of Hazardous Substances in Electric and Electronic Equipment.  Adopted in the EU in 2006.  Batteries are currently exempt from RoHS.
Rechargeable:  A cell or battery which is designed to be electrically recharged.
Rupture:  Mechanical failure of a cells container or battery case induced by an internal or external cause, resulting in exposure or spillage but not ejection of solid materials.

SDS:   Safety Data Sheets are required by the Occupational Safety and Health Administration's (OSHA) Hazardous Communication Program to identify substances that are used or contained in materials that may be hazardous to human health.   Although batteries are classified as "articles" and do not require SDS,  cell manufacturers and battery pack manufacturers normally provide them.  SDS are in compliance with the new Global Harmonized System, or GHS.   OSHA has replaced MSDS with SDS in 2013 under 29CFR Part 1910.1200; and requires that by December 1, 2013 workers be trained in the new label element and Safety Data Sheet (SDS) format, consisting of 16 specific sections in harmony with the GHS standards.  Fedco Batteries has updated to the new SDS format.

Self-discharge:  Decreasing capacity during storage without load, caused by chemical reaction in a battery. The higher the temperature during storage, the greater the rate of self-discharge.
Short circuit:  A direct connection between the positive and negative terminals of a cell or battery that provides a virtual zero resistance path for current flow.

SMBus:  SMBus is the System Management Bus as defines by the Intel Corporation in 1995.  It is used in personal computers and servers for system management communications, including battery charge status.

T-Tests:  "Nickname" for the UN38.3 Tests.

UN3090, UN3091, UN3480, UN3481 & UN3496:   The IATA Dangerous Goods Regulations and the U.S. Code of Federal Regulations (49CFR Part 172(c)(1) classify lithium-metal primary and lithium-ion rechargeable cells and batteries as Dangerous Goods; and must be shipped in passenger and cargo aircraft in accordance with specific packing instructions.  (See Packing Instructions)
    UN3090 - Lithium-metal primary cells and batteries. 
    UN3091 - Lithium-metal primary cells and batteries shipped with or in equipment. 
    UN3480 - Lithium-ion rechargeable cells and batteries.
    UN3481 - Lithium-ion rechargeable cells and batteries shipped with or in equipment.
    UN3496 - Nickel-Metal Hydride rechargeable cells and batteries (When shipping >100kg by Ocean Freight)

UN 38.3 Tests:  In order to offer for transport in passenger and cargo aircraft, lithium-metal primary cells and batteries and lithium-ion rechargeable cells and batteries must comply with Packing Instructions 965 through 970 (as applicable) in The ICAO Technical Instructions "Recommendations on the Transport of Dangerous Goods Manual of Tests and Criteria".   These packing instructions includes mandatory provisions for the testing of lithium metal and lithium-ion cells and batteries (Sub-section 38.3).   (See the UN38.3 Lithium Tests Rev. 7 PDF in "Battery Shipping Regulations".)

Vent:  A safety device built into almost all cells designed to release internal pressure in the case of overcharge, over temperature and other abuses.  The vent will preclude rupture or disassembly.
Venting:   The release of excessive internal pressure from a cell or battery in a manner intended by design to preclude rupture or disassembly.  Venting may also release electrolyte and catch fire.  
Watt-hours:  A cell or battery’s nominal voltage multiplied by it’s rated capacity in amp-hours.


REV 3: 04/26/2023