Special car battery terms explained understandably

This article contains:

    Battery terms from A to Z: The most important specialist terms for batteries. So you know what we are talking about.

    Absorbent Glass Mat (AGM)

    The mat of micro glass fibers which is used for absorbing the sulfuric acid in lead batteries. The distinguishing feature of an AGM battery.

    Acid Stratification

    When charging a lead-acid cell, high density acid is produced in the plates. This heavy acid drops as a result of gravitation to the lower part of the cell while lower density acid rises to the top of the cell. This stratification of acid can cause loss of capacity &/or caused by battery.

    Active Material

    The active material in the positive plates is lead dioxide and that in the negative is metallic sponge lead. When an electrical circuit is created, these materials react with sulfuric acid during charging and discharging according to the following chemical reaction: PbO2 + Pb + 2H2SO4 = 2PbSO4 + 2H2O

    Ampere (Amp, A)

    The unit of measure of the electron flow, or current, through a circuit.

    Ampere (Amp) Hours

    A unit of measure for a battery’s electrical storage capacity, obtained by multiplying the current in amperes by the time in hours of discharge. (Example: A battery which delivers 5 amperes for 20 hours delivers 5 amperes x 20 hours = 100 Amp-Hr of capacity.)

    Battery Case

    Battery box containing the plate blocks, the connectors and the electrolyte.

    Battery Charger

    Unit supplying electrical energy to a secondary battery. Product release: Battery Chargers.

    Battery Test

    Battery Test describes the test for determining the charging condition and electrolyte level of lead batteries with liquid electrolyte. The charging condition is determined by measuring of the acid density.


    The ability of a fully charged battery to deliver a specified quantity of electricity (Amp-Hr, AH) at a given rate (Amp, A) over a definite period of time (Hr).


    The basic electrochemical current-producing unit in a battery consisting of a set of positive plates, negative plates, electrolyte, separators and casing. There are six cells in a 12-volt lead-acid battery.

    Charge Acceptance

    The quantity of current in ampere hours which a battery in a defined charge state can accept at a specified temperature and charge voltage within a defined period.


    The path followed by a flow of electrons. A closed circuit is a complete path. An open circuit has a broken or disconnected path.

    Cold Cranking Rating

    Number of amperes a lead-acid battery at 0oF (-17.8°C) can deliver for 30 seconds and maintain at least 1.2 volts per cell. Very important for the operation of snowmobile batteries.


    The polypropylene or hard rubber case which holds the battery plates, straps and electrolyte.


    The destructive chemical reaction of a liquid electrolyte with a reactive material – e.g., dilute sulfuric acid on iron, producing corrosion products such as rust.


    The lid for the container


    The rate of flow of electricity, or the movement of electrons along a conductor. The unit of measure for current is the ampere.


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

    Deep Discharge

    State in which a cell is fully discharged using low current, so that the voltage falls below the final discharging voltage.


    When a battery is delivering current, it is said to be discharging.


    In a lead-acid battery, the electrolyte is sulfuric acid diluted with water. It is a conductor that supplies water and sulfate for the electrochemical reaction: PbO2 + Pb + 2H2SO4 = 2PbSO4 + 2H20


    Long-term loss of capacity during use.


    A state in which a battery no longer functions satisfactorily. There are several forms of failure.

    Failure, permanent

    A state in which a cell or battery cannot be recharged to a satisfactory level.

    Failure, reversible

    A failure condition that can be remedied by using particular electrical procedures or by reconditioning.

    Final charging current

    The final charging current is the current at the end of an IU charging operation (gassing current).

    Final discharging voltage

    Indicates the lowest allowable voltage level that a battery or cell can be discharged to. Discharging to below this cutoff voltage (deep discharge) can impair or (through pole reversal) destroy the electrochemical cell in the case of various battery types (e.g. lead, Ni/Cd, NiMH).


    Initial electrical charging for converting the active masses into the charged state (e.g. PbSO4 -> Pb (-) und PbO2 (+) ).


    The reinforced outer parts of a battery grid.


    The lead alloy framework that supports the active material of a battery plate and conducts current.


    The reference potential of a circuit. In automobile use, the result of attaching the battery cable to the body or frame of a vehicle which is used as a path for completing a circuit in lieu of a direct wire from a component. Today, over 99% of automotive and LTV applications, use the negative terminal of the battery as the ground.

    High Current Charging

    Charging with a current strength greater than 1C.

    High Current Discharging

    Discharging with a current strength greater than 5C.


    Apparent resistance of an alternating circuit to current; comprised of reactance and ohmic resistance.

    Industrial battery

    A storage battery which is used to supply power to industrial equipment (e.g. fork-lift trucks).

    Initial Charge

    The initial charge is the first charging process after the electrolyte has been poured into a dry precharged battery. It has the purpose of bringing the cell or battery to full initial capacity.

    Initial Tempertature

    The temperature of the electrolyte in an accumulator when discharging or charging begins.

    Initial Voltage

    A battery’s initial voltage is the working voltage when discharging begins. Measurement usually follows, as soon as current has flowed long enough for the voltage to remain at a constant level, for example after 10% usage of a previously fully-charged cell.

    Inner Resistance

    Ohmic resistance of a battery.

    Inner Ressistance, Effective

    The measurable resistance against the flow of current in a battery expressed as a drop in the battery voltage proportional to the discharging current. The value is dependent on the manner of construction, the charge state, temperature and the age of the battery.

    Insulation Resistance

    Insulation resistance is the resistance between a cell or battery and a mass/earth (motor-vehicle body, torso)

    JIS Code

    Powersports batteries are tested according to the JIS Norm Standards ; in that case JIS D 5302. : 2004 Edition This Japanese Industrial Standard norm is relevant for standard flooded lead-acid batteries for motorcycles. This standard is stipulating the types, structures and tests of lead-acid batteries including in the last revision for the VRLA ( valve regulated lead-acid ) also the tests methods.

    Lamp Black

    A fine carbon powder used as an ingredient for negative lead masses. Component share ≤ 0.5%.

    Lead (Pb)

    A chemical element which belongs to the heavy metals (specific weight 11.341 g/cm³). It is used in the form of bivalent and / or quadrivalent compounds (PbSO4 or PbO2), as porous sponge lead for active masses, and as lead-antimony or lead-calcium alloys for grids in lead batteries.

    Lead battery

    An accumulator in which the electrodes consist primarily of lead, whereas the electrolyte consists of diluted sulfuric acid. Product release: Automotive batteries catalog.

    Lead Dioxide

    Quadrivalent lead oxide (PbO2), which is generated electrochemically during formation and which forms the active mass of the positive lead electrode. Color: black-brown.

    Lead Oxide (Litharge)

    A bivalent lead oxide (PbO), which can occur in two modifications: the orthorhombic, yellow high-temperature modification and the tetragonal, red modification. It is used in producing active lead masses.

    Lead Sulfate (PbSO4)

    Chemical compound produced on the positive and negative plates of a lead battery during discharge. It is the result of a chemical reaction between the sulfuric acid and lead dioxide of the positive electrode or the metallic lead of the negative electrode.

    Lead Sulfate, Tetrabase

    Chemical formula 3 PbO

    Lead, Free (Pbmetallic)

    Non-oxidized residual lead in cured lead plates. See Curing.

    Lead-Calcium Alloy

    A lead alloy for grids used in maintenance-free lead batteries. The typical calcium component is approx. 08%.

    Lead-Coated Part

    A metal part with a thin protective coat of metallic lead that has been deposited on the surface by galvanization.


    General term for the non-cellulose wood component (lignin sulfuric acid or desulfonate sulfuric acid). It is the main component of the additives for negative lead masses with a component share of ≤1%. It is sold under the name Vanisperse.


    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 cutoff voltage.

    Low Current Charging

    Charging with a current strength that is only slightly higher than what is needed to compensate for self-discharge losses.

    Low Current Discharging

    Discharging with current flow under 0.1 C.

    Machine Casting

    A full or semi-automatic casting process for grids or small parts.

    Maintained Capacity

    The battery is kept in a fully charged state by means of a constant voltage charger with a low charging voltage (compensates for self-discharging).

    Maintenance-Free battery with Fixed Electrolyte

    Lead-acid battery in which the electrolyte is held in place in a gel or microglass mat (AGM). The battery is sealed and is equipped with valves. It is highly stable and exhibits good cycling characteristics.

    Mass, Active

    The material in the electrodes that takes part in the charging and discharging reactions. In the 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.

    Mold, Casting

    A component made of cast iron or steel in which the required geometry of the mold takes the form of a cavity (e.g. casting mold for producing lead grids).

    Negative Electrode

    See Electrode, negative.

    Negative Terminal

    Negative pole of a battery.

    Nominal Voltage

    See Voltage, Nom.


    A unit for measuring electrical resistance or impedance within an electrical circuit.

    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.


    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.

    Plate- Negative

    Cast metallic frame which contains a spongy lead active material. Reserve Capacity Rating (RC) – Number of minutes that a new, fully charged will deliver 25 amperes at 26.7°C/80o F and maintain a terminal voltage equal to, or higher than, 1.75 volts per cell. This rating represents the time the battery will continue to operate essential accessories if the alternator or generator of a vehicle fails.

    Plate- Positive

    Cast metallic frame which contains the lead dioxide active material.


    Component with venting ducts for sealing a cell opening.


    Electrical term for describing the charge or voltage relationship between two electrodes.

    Purified Water

    Distilled or demineralized water for compensating the water losses in batteries requiring maintenance.

    Rated Capacity

    The capacity in Ah (as defined by the manufacturer) under defined discharging conditions (current, temperature)

    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 (e.g. charging or discharging a secondary battery).


    Creating a fully-charged state from any charged state (e.g. caused by self-discharging).


    Discharging with low current (e.g. I100) and recharging with approx. 30% overcharge. The procedure can be repeated if required.

    Remaining Capactiy

    The capacity that remains after discharging.

    Remaining Charge

    Full charge from undefined charge state.

    Reserve Capacity Rating (RC)

    Number of minutes that a new, fully charged will deliver 25 amperes at 26.7o C/80o F and maintain a terminal voltage equal to, or higher than, 1.75 volts per cell. This rating represents the time the battery will continue to operate essential accessories if the alternator or generator of a vehicle fails.


    Self-discharging is a temperature-dependent permanent chemical reaction process at a cell’s or battery’s electrodes, without connection to a consumer.


    A divider between the positive and negative plates of an element which allows the flow of current to pass through it.

    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.

    Service Life

    The length of satisfactory performance measured in years or charging / discharging cycles.

    Service Life, Cyclical

    The number of cycles a battery lasts before its capacity falls below the acceptable value.

    Service Life, Useful

    The useful service life of an accumulator expressed as the period of time prior to its capacity falling to a specified component of the rated value.


    Battery protection against vibration achieved through design measures (e.g. fixing a plate block in position using hot-melt adhesive).

    Short Circuit

    An unintended current-bypass in an electric device or wiring, generally very low in resistance and thus causing a large current to flow. In a battery, a cell short circuit may be permanent enough to discharge the cell and render the battery useless.

    Standard Charging

    Charging current that can be maintained indefinitely without the need for special cells or switchable battery chargers. Under normal circumstances, cells can be charged overnight in 12 to 14 hours.

    State of Charge (SOC)/Health (SOH)

    The amount of electrical energy stored in a battery at a given time expressed as a percentage of the energy when fully charged.

    Temperature, Nominal (Tnom)

    An electrolyte’s nominal temperature is a specified value which is used as a reference value for capacity tests (e.g. according to European standard EN 60095-1, Tnom lies in the region of 25±2 °C for the 20-hour capacity of lead batteries).


    Electrical connection from the battery to the external circuit. Each terminal is connected to either the first (positive) or last strap (negative) in the series connection of cells in a battery.

    Thermal Runaway

    Continuous heating of the electrolyte up to the boiling point due to an increase in charging current as the charging voltage decreases (lead accumulator with falling charge characteristic).

    Total Cost of Ownership (TCO)

    Definition TOTAL COST OF OWNERSHIP Accounting technique •Shows all aspects/costs during life time of a vehicle: •acquisition •energy (fuel consumption) •repair and maintenance (tyres, batteries) •Shows main and hidden costs •Similar to Life Cycle Cost (LCC) For investment goods like buildings or production machines


    A device allowing gas to escape when inner pressure is too high, while preventing air from entering.

    Valve Regulated Lead-Acid (VRLA) battery

    Batteries which are sealed and maintenance-free.

    Venting Valve, Recloseable

    Safety valve in the cell which opens in case of overpressure and closes again automatically when normal pressure has been restored (e.g. gel battery, AGM battery).


    Unit of measurement for electrical voltage. Abbreviation V. Named after the Italian physicist and doctor Count Alessandro Volta (1745 – 1827).

    Voltage and Temperature Dependent Cutoff (VTCO)

    See Cutoff, voltage and temperature dependent.

    Voltage Dip

    A momentary drop in voltage when high current discharging is used (e.g. in the case of lead accumulators).

    Voltage Drop

    Should current flow through a resistor inside a closed electric circuit, a voltage drop will occur.

    Voltage Plateau

    A slow decrease in voltage over a long period of time. Characteristic for many discharges of closed cadmium cells and closed lead cells. As a rule, the plateau extends from the first voltage drop at the start of the discharge to the bend of the curve after which the voltage drops rapidly at the end.

    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).


    The unit of measure for electrical power, i.e., the rate of doing work, in moving electrons by, or against, an electrical potential. Formula: Watts = Amperes x Volt.


    Connecting together two or more plates to form a plate block by welding on a connecting strap. See COS.

    Working Capacity (Energy)

    The working capacity of a cell or battery is the dischargeable electrical energy in watt hours [Wh] for an accumulator with average discharge voltage and corrected to Tnom.

    Working Voltage

    The working voltage of a cell or battery begins at its electrical connections as soon as an electrical consumer is connected to it; it is smaller than the nominal voltage.