Battery Glossary - Common Battery Terms

Absorbent Glass Mat (AGM): An AGM battery is a lead-acid battery using absorbent glass mat (AGM) separator technology, representing the development trend of lead-acid batteries today and in the future.

Acid Stratification: When a lead-acid battery is charged, high-density acid is produced in the battery plates. Under gravity, the high-density acid sinks to the bottom of the battery, while lower-density acid floats to the top. This acid stratification can cause loss of battery capacity and/or battery failure.

Active Material: The active material in the positive plate is lead dioxide, while the active material in the negative plate is spongy lead. When the circuit is connected, these materials react with sulfuric acid during charging and discharging according to the following chemical reaction: PbO2 + Pb + 2H2SO4 = 2PbSO4 + 2H2O.

Ampere: The unit of measurement for electric current.

Battery Box: The container that holds the battery plates, connectors and electrolyte.

Battery Charger: A device that supplies electrical energy to a battery.

Battery Test: A test to determine the state of charge and electrolyte level of a lead battery containing liquid electrolyte. The state of charge depends on the measurement of acid density.

Capacity: The ability of a fully charged battery to deliver a specified amount of electrical energy (ampere-hours, Ah) at a given current (amperes, A) over a specified period (hours).

Cell: The basic unit that generates electrochemical current, consisting of a set of positive plates, negative plates, electrolyte, separator and housing. A 12V lead-acid battery contains 6 cells.

Charge Acceptance: The charging current value (expressed in ampere-hours) that a battery can accept within a certain period at a specified temperature, voltage and state of charge.

Circuit: The path along which electric current flows. A closed circuit is a complete path; there are open circuits and broken circuits.

Cold Cranking Rating: The ability of a lead-acid battery to sustain 30 seconds at 0 deg F (-17.8 deg C) while maintaining at least 1.2V per cell. This is very important for snowmobile battery operation.

Battery Case: A polypropylene or hard plastic case that holds the battery plates, connectors and electrolyte.

Corrosion: A destructive chemical reaction between the liquid electrolyte and reactive materials, for example dilute sulfuric acid on iron, producing corrosive substances such as rust.

Battery Cover: The cover of a battery.

Current: The rate of electrical flow, or the rate at which electrons move along a conductor. Current is measured in amperes.

Cycle: In a battery, one discharge plus one recharge equals one cycle.

Deep Discharge: A state in which the battery is fully discharged at a relatively low current so that the voltage drops below the final discharge voltage.

Discharge: When a battery produces current, the battery is discharging.

Electrolyte: In a lead-acid battery, the electrolyte is sulfuric acid diluted with water. The electrolyte is a conductor that supplies water and sulfate ions, producing the electrochemical reaction: PbO2 + Pb + 2H2SO4 = 2PbSO4 + 2H2O.

Fading: Long-term loss of capacity during use.

Fault: A state in which the battery is not functioning properly. Faults take several forms.

Permanent Fault: A state in which the battery or accumulator has poor recharging ability.

Reversible Fault: A fault condition that can be repaired by special electrical procedures or by reconditioning.

Final Charging Current: The current at the end of an IU charging operation (gas flow).

Final Discharge Voltage: The permissible voltage level to which a battery or accumulator can be discharged. If several cells are involved (lead, Ni/Cd, NiMH, etc.), discharging below this cutoff voltage (deep discharge) can affect or damage the electrochemical cells (through polarity reversal).

Formation: The initial charge that converts the active materials to the charged state (e.g., PbSO4 to Pb (-) and PbO2 (+)).

Frame: The outer reinforcement of the battery grid.

Grid Separator: The separator between the positive and negative plates that allows ions to pass through.

Ground: The reference voltage of a circuit. In automobiles, the battery cable is connected to the body or frame as the path of the complete circuit, replacing direct wiring of components. Today, more than 99% of automotive and light transport applications use the negative battery terminal as ground.

High Current Charging: Charging with a current intensity higher than 1C.

High Current Discharging: Discharging with a current intensity higher than 5C.

Impedance: The apparent resistance of an AC circuit to current, consisting of reactance and ohmic resistance.

Industrial Battery: An accumulator used to power industrial equipment such as forklifts.

Initial Charging: The first charging process after filling electrolyte into a pre-charged dry battery. The purpose is to bring the battery or accumulator to an initial full charge.

Initial Temperature: The temperature of the electrolyte in the battery when discharging or charging begins.

Initial Voltage: The working voltage of a battery when discharge begins. It is usually measured as soon as the current has flowed long enough for the voltage to stabilize, for example after using 10% of a previously fully charged battery.

Internal Resistance: The ohmic resistance of a battery.

Effective Internal Resistance: The measurable resistance to current flow in a battery, expressed as the battery voltage drop proportional to the discharge current. This value depends on how the battery is constructed, its state of charge, temperature and age.

Insulation Resistance: The resistance between the battery or accumulator and a material/ground (vehicle body, frame).

JIS Specification: Powersports batteries are tested according to JIS specification standards; in this case, the JIS D5302 2004 edition is used. This Japanese industry standard applies to SLI lead-acid batteries for motorcycles. It specifies the types, construction and tests of lead-acid batteries, including the latest versions of valve-regulated lead-acid (VRLA) batteries, and also specifies test methods.

Carbon Black: A fine carbon powder used as a component of the negative electrode active material, with a content of less than or equal to 0.5%.

Lead (Pb): A chemical element that is a heavy metal (specific gravity 11.341 g/cm3). It is used in divalent and/or tetravalent compounds (PbSO4 or PbO2), as porous spongy lead for active material, and as lead-antimony or lead-calcium alloy in battery grids.

Lead-Acid Battery: A type of accumulator in which the electrodes consist mainly of lead and the electrolyte consists of dilute sulfuric acid. Product release: automotive battery category.

Lead Dioxide: Tetravalent lead oxide (PbO2), produced electrochemically during formation, which forms the active material of the positive lead electrode. Color: black-brown.

Lead Oxide (Lead Monoxide): A divalent lead oxide (PbO) with two modifications: an orthorhombic yellow high-temperature modification and a tetragonal red modification. It is used to produce active lead material.

Lead Sulfate (PbSO4): A compound produced on the positive and negative plates of a lead battery during discharge. It is the product of the chemical reaction between sulfuric acid and the lead dioxide of the positive plate or the metallic lead of the negative plate.

Tetravalent Lead Sulfate: Chemical formula 3PbO.

Free Lead (Metallic Lead): Non-oxidized residual lead in the solidified lead plate.

Lead-Calcium Alloy: The lead alloy used for grids in maintenance-free lead batteries. The calcium content is usually about 0.08%.

Lead-Coated Parts: Metal parts with a thin protective layer of metallic lead formed on the surface by lead plating.

Lignin: A general term for non-cellulosic wood components (lignosulfonic acid or desulfonated sulfonic acid). Lignin is the main component of the negative electrode active material additive, with a content of less than or equal to 1%. It is sold under the name Norwegian lignin.

Load: The current (in amperes) that a fully charged battery can deliver at a specified temperature and within a specified time without the voltage dropping below a pre-specified cutoff voltage.

Low Current Charging: Charging with a current intensity only slightly higher than that required to compensate for self-discharge losses.

Low Current Discharging: Discharging with a current below 0.1C.

Machine Casting: A fully automatic or semi-automatic casting process for grids or small parts.

Maintenance (Float) Charge: Keeping a battery fully charged with a constant-voltage charger at a low charging voltage (compensating for self-discharge).

Maintenance-Free - Starved Electrolyte (AGM): The electrolyte is immobilized in absorbent glass mat (AGM) separators. The battery is sealed, fitted with pressure valves, and has a good cycle life.

Active Material: The materials in the electrodes that participate in the charging and discharging reactions. In nickel-cadmium batteries, nickel hydroxide and cadmium hydroxide are used as active materials in the positive and negative electrodes. In lead batteries, lead dioxide and spongy lead are used as active materials in the positive and negative electrodes. The sulfuric acid used as electrolyte in lead batteries can also be regarded as an active material because it also participates in the battery reaction.

Casting Mold: A component made of cast iron or cast steel in which the required geometric dimensions of the mold take the form of cavities (such as lead grids in production molds).

Negative Pole: See negative pole.

Negative Terminal: The negative pole of the battery.

Rated Voltage: See rated voltage.

Ohm: The unit of measurement for resistance.

Parallel Connection: Connecting all positive terminals or all negative terminals of several batteries. This increases the capacity of the battery network while keeping the voltage constant.

Active Material (Paste): A mixture of various compounds (such as lead oxide and water, sulfuric acid, etc.) used to coat the positive and negative grids of lead batteries. Positive and negative active materials differ in their formulations. These active materials are then converted into positive and negative cured substances.

Negative Plate: A cast metal frame containing spongy lead active material. Reserve capacity rating: the number of minutes a new fully charged battery can deliver 25A at 80 deg F (26.7 deg C) while maintaining a voltage equal to or higher than 1.75V per cell. This rating indicates how long the battery can keep essential accessories running if the vehicle alternator or generator fails.

Positive Plate: A cast metal frame containing lead dioxide active material.

Plug (Vent Plug): A component with a vent tube used to seal the opening of a battery.

Polarity: An electrical term describing the charging or voltage relationship between two electrodes.

Purified Water: Distilled or deionized water used to compensate for water loss in batteries that require maintenance.

Rated Capacity: The capacity under specified discharge conditions (current, temperature), expressed in Ah (according to manufacturer specifications).

Reversible Reaction: A chemical reaction that can occur in either direction (oxidation or reduction). Since accumulators are in constant discharge and charge states during use, the battery reaction must be reversible.

Recharge: Creating a fully charged state from any charge state (e.g., caused by self-discharge).

Reconditioning: Discharging at a low current (e.g., I100) and charging with about 30% overcharge. The procedure can be repeated if necessary.

Residual Capacity: The capacity remaining after discharge.

Residual Charge: The full charge remaining in an undefined state of charge.

20-Hour Rated Capacity (C20): The capacity produced when a battery is discharged at a current equal to one-twentieth of its 20-hour rated capacity at an ambient temperature of 80 deg F (26.7 deg C) until the terminal voltage drops to 10.5V. It determines the ampere-hours needed to provide enough power for vehicle operation without the voltage dropping.

Self-Discharge: A permanent chemical reaction process of the electrodes of a battery or accumulator without any power-consuming device connected, which depends on temperature.

Separator: A distributor between the positive and negative plates of an element through which current can flow.

Series Connection: Connecting the positive terminal of a battery/accumulator to the negative terminal of the next battery/accumulator.

Service Life: The number of years of service or charge-discharge cycles of an accumulator that meet performance requirements.

Cycle Life: The number of cycles a battery can sustain before its capacity drops below an acceptable value.

Service Life: The service life of an accumulator, expressed as the period before its capacity drops below a specified fraction of the rated value.

Shock Resistance: Protection of the battery against impacts through design measures (e.g., fixing the battery plates in place with hot-melt adhesive).

Short Circuit: An accidental bypass of current in electrical equipment or wiring, usually with very low resistance, resulting in a large current flow. A short circuit in a battery may be permanent and can cause the battery to discharge and become unusable.

SLI: Stands for starting, lighting and ignition.

Standard Charging: A charging current that can be maintained indefinitely without a special battery unit or switchable battery charger. Under normal conditions, the battery is charged for 12-14 hours.

State of Charge (SOC) / State of Health (SOH): The amount of electrical energy stored in a battery at a given time, expressed as a percentage of the energy at full charge.

Nominal Temperature (Tnom): A specified value for the electrolyte temperature, usually used as a reference for capacity tests (e.g., according to European standard EN 60095-1, for a 20-hour capacity lead battery, Tnom is 25 +/- 2 deg C).

Terminal Post: The electrical connection between the battery and the external circuit. When cells are connected in series in a battery, each terminal post is connected to the first (positive) or last (negative) connecting cable.

Thermal Runaway: Continuous heating of the electrolyte to its boiling point caused by an increase in charging current when the charging voltage drops (the charge of non-lead batteries drops).

Total Cost of Ownership (TCO): An accounting method that shows all aspects/costs during the life of a vehicle: acquisition, energy (fuel consumption), repair and maintenance (tires, battery), showing both primary costs and hidden costs. Similar to life-cycle costing (LCC). Used for capital goods such as buildings or production machines.

Valve: A device that allows gas to escape when internal pressure is too high while preventing air from entering.

Valve-Regulated Lead-Acid (VRLA) Battery: A sealed, maintenance-free battery.

Resealable Vent Valve: A safety valve in a battery that opens automatically when pressure is excessive and closes automatically when normal rated pressure is restored (e.g., in gel batteries, absorbent glass mat (AGM) batteries, etc.).

Volt: The unit of measurement for voltage, abbreviated V, named after the Italian physicist and physician Alessandro Volta (1745-1827).

Voltage and Temperature Dependent Cutoff (VTCO): See voltage and temperature cutoff value.

Voltage Dip: A momentary drop in voltage when discharging at high current (e.g., with non-lead batteries).

Voltage Drop: If current flows through a resistor inside a closed circuit, the voltage drops.

Voltage Plateau: A slow voltage decline over a long period. Many closed cadmium and closed lead battery discharges have this characteristic. In general, the voltage plateau lasts from the initial voltage drop at the start of discharge until the curve bends at the final rapid voltage drop.

Rated Voltage: The average voltage of a battery during discharge at low current intensity. The manufacturer specifies the value on the battery (e.g., Ni/Cd = 1.2V per cell).

Watt: The unit of measurement for electrical power, i.e., the rate of work done in moving electrons along or against the direction of the potential, calculated as: watts = amperes x volts.

Welding: Connecting two or more battery plates together by welding connecting wires to form one plate.

Working Capacity (Energy): The electrical energy that an accumulator can discharge, expressed in watt-hours [Wh]; the working voltage is the average discharge voltage adjusted to the nominal value (Tnom).

Working Voltage: The voltage at which a battery or accumulator starts working at the electrical connection as soon as a power-consuming device is connected; the working voltage is lower than the rated voltage.