Glossary of Battery Terms

Glossary of Battery Terms />


BatteryPower Zone believes that it is important to understand the jargon associated with batteries to help you make informed buying decisions. With that in mind, here is a list of terms that one may encounter when dealing with batteries their parts and functions.

Accumulator – A cell or battery with recharging capabilities. Also referred to as a secondary battery.

Ampere/ Amp – Unit for measuring electric current. Also denoted by A or I (in mathematical equations).

Amp Hour or Ampere-Hour – Mathematically, it is the product of current and time in hours. It denotes a battery’s electrical storage capacity. Denoted by Ah or mAh (1 Ah=1000 mAh).

Amp Hour or Ampere-Hour Capacity – The magnitude of Ah a battery can provide in a single discharge.

Anode – The terminal of the battery where current flowing in the electric circuit enters the battery. The negative electrode during discharging and positive electrode during charging.

Aqueous Batteries – Batteries that possess a water-based electrolyte.

Actual Capacity or Available Capacity – The actual electrical storage capacity of the battery. It is less than the rated capacity.

Battery Capacity - The magnitude of the battery's electrical output. Measured in Ah. Also measured in watt-hours (Wh) which is the product of Ah and the battery voltage.

Battery Charger – A source of supplying electrical energy to a battery.

Battery-Charge Rate – The magnitude of the current charging the battery.

Cutoff Voltage – A designated voltage which is set as the lower bound of the battery’s capacity.

C – Denotes the charging or discharging current. Calculated by dividing the battery’s capacity (in Ah) by 1 hour.

Capacity – A battery’s single discharge capacity.

Cathode - The terminal of the battery where current flowing in the electric circuit leaves the battery. The positive electrode during discharging and negative electrode during charging.

Cell – The basic unit of a battery comprising of negative and positive plates.

Charge – The process of storing electrical energy in a battery as chemical energy.

Charge Rate – The current flowing through the battery during charging.

Charging – See Charge.

Constant-Current Charge – Charging using the constant magnitude of the current.

Constant-Voltage Charge – Charging using the constant magnitude of voltage.

Cycle – One complete charge or discharge.

Deep Cycle – Discharging a battery till cut-off voltage.

Shallow Cycling – Charging or discharging a battery above the cut-off voltage.

Cycle Life – Number of charging/discharging cycles a battery can manage without any significant loss of its capacity.

Direct Current (DC) – A current which originates from a fixed polarity source like a battery.

Discharge – Process of converting a battery’s stored chemical energy into electrical energy.

Depth of Discharge – The portion of the energy withdrawn from the battery. Expressed as a percentage of total battery capacity.

Discharge, deep – Complete discharge till the battery’s end-point voltage.

Discharge, high-rate – Discharging high magnitude of current from a battery in a short time interval.

Discharge, low-rate - Discharging low magnitude of current from a battery in a long time interval.

Drain – Removal of current from a cell.

Dry Cell – A cell with an electrolyte that does not flow due to the presence of a porous medium.

Electrochemical Couple – Combination of reactive materials within a cell that facilitates storing chemical energy via an electrochemical reaction.

Electrode – A conductor which acts as the positive/negative terminal of the battery.

Electrolyte – A compound (normally dissolved in a water-based solution) that can conduct electricity due to the presence of ions.

Electro-positivity – The tendency to function as the positive terminal within a galvanic cell. High electro-positivity means a higher oxidation rate.

End-of-Discharge Voltage – The voltage left in the battery after discharging.

Energy - Output Capability – Product of capacity and voltage. Its unit is Wh.

Energy Density – Ratio of the cell’s stored energy with either volume or weight of the cell.

Final Voltage – See Cutoff Voltage.

Float Charging – A charging method normally used for lead-acid batteries. It comprises maintaining a secondary cell at full charge via a constant-voltage supply.

Galvanic Cell – A cell where electrodes are separated by the electrolyte and electrical energy can be produced via an electrochemical reaction.

Gassing – The emergence of gas from one or both electrodes during charging or discharging.

Internal Resistance – The resistance to current flow within the battery or cell.

Memory Effect – A battery’s temporary loss of storage capacity at normal voltage levels after it has been discharged below the full depth of discharge for multiple cycles.

Negative Terminal – The terminal from where the electrons leave the battery in an electrical circuit.

Non-aqueous Batteries – Cells without water-based electrolytes.

Ohm’s Law – The law that defines the relationship between current (I), Voltage (V) and resistance (R). Ohm’s law can be written as I =V/R, V =I x R, and R =V/I.

Open Circuit – An incomplete circuit without an electric load where no current can flow.

Open-Circuit Voltage – The potential difference between two terminals in an open circuit.

Oxidation – The loss of an electron as a result of a chemical reaction.

Parallel Connection – It is the arrangement of combining cells by connecting the same polarity terminals. As a result, the voltage of individual cells is the same as the total voltage across the terminals and leads to an increase in the overall capacity.

Polarity – The positivity or negativity of a battery’s terminals.

Positive Terminal - The terminal from where the electrons enter the battery in an electrical circuit.

Primary Battery A combination of primary cells.

Primary Cell – A non-rechargeable cell. It is designed in a manner that once it discharges, it cannot be easily recharged.

Rated Capacity – The ideal capacity or the manufacturer’s capacity. It is the value of amp-hour a battery can provide under ideal conditions.

Rechargeable – A battery that can be recharged after it has been discharged. It is a quality of secondary cells or batteries.

Recombination – The phase during which the gases produced at the electrodes are recombined. The recombination normally forms water.

Reduction – The gain of an electron as a result of a chemical reaction.

Seal – The lock placed on a galvanic cell that prevents the electrolyte and other fluids from leaking out of the cell. It also prevents air from entering the cell.

Secondary Battery – A combination of secondary cells. See also Storage Battery; Storage Cell.

Self-Discharge – The battery discharge that occurs without attaching a load to the battery i.e. in open-circuit condition.

Separator – A permeable membrane that prevents physical contact between cathode and anode but allows ions to pass through

Series Connection – The arrangement of cells where the positive terminal of each cell is connected to the negative terminal of the other cell in a succession of one another. As a result, the voltage accumulates and the total voltage across the arrangement is the sum of individual voltages.

Shelf Life – Associated with dry cells, it is the period of time since their manufacturing date till the time they retain most (~90%) of their energy content. This time period is normally calculated at a temperature of 21 oC.

Short-Circuit – An electrical hazard created when a low resistance path is created through an unintentional connection in the circuit. This path bypasses the load and causes the battery to provide a high magnitude of current which can melt components and even cause electrical fires.

Short-Circuit Current – The high magnitude current flowing in the low resistance path during a short-circuit scenario.

Starting-Lighting-Ignition (SLI) Battery – A battery that provides the initial current required to start internal combustion engines found in automobiles. They also provide power to electrical components when the car engine is not running. They can also be used for emergency lighting purposes.

Stationary Battery – A rechargeable battery designed to be used at a fixed location.

Storage Battery – Also known as a secondary battery or accumulator, it is an arrangement of cells where the discharge caused by the electrochemical reaction can be reversed easily by applying a current that enters the battery from the terminal where the current leaves the battery during discharge. In theory, most batteries can be recharged but the process needs to be economically viable for it to be categorized as a storage battery.

Storage Cell – Also known as a secondary cell, it is a single cell where the discharge caused by the electrochemical reaction can be reversed easily by applying a current that enters the cell from the terminal where the current leaves the cell during discharge.

Taper Charge – An approach of charging the battery where relatively higher currents are provided to the battery when it is on a low charge level and the currents are tapered gradually to lower magnitudes as the battery reaches a higher charge level.

Terminals – The points on the battery for connecting wires so that they may be used to complete an electrical circuit with an electrical load.

Thermal Runaway – A destructive condition of a battery or cell where it destroys itself by generating an excessive amount of heat. The heat is normally caused as a result of over-charging or a high rate of discharge.

Trickle Charging (Float Charging) – The method of maintaining a battery or a cell where the re-charging process is completed. For most 12 volt batteries the voltage would be between 13.6 to 13.8 Volts with a current less than 50 milliamps.

Vent – An opening in the cell that allows the gases produced inside to escape outside.

Volt – The unit for measuring voltage.

Voltage, cutoff – Voltage after the completion of useful discharge.

Voltage, end-point – The voltage below which a battery or cell normally cannot power the connected load.

Voltage, nominal – The voltage when the rated current is delivered by the cell in its fully charged state.

Watt – The unit for measuring power. It is a product of current (amperes) and voltage (volts).

Wet Cell – A cell with a fluid-based electrolyte which can flow within the confines of the cell.

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