ACID
Sulphuric Acid. This is the electrolyte or liquid contained in a battery’s cells

ACTIVE MATERIAL
The active material in the positive plates of a battery is lead dioxide and that in the negative plates is metallic sponge lead. When an electrical circuit is created, these materials react with sulphuric acid during charging and discharging according to the following chemical reaction

PbO2 + Pb + 2H2SO4 = 2PbSO4 + 2H2O

ACTIVATION
Adding electrolyte to a dry battery.

AGM
Absorbed Glass Mat

AGM BATTERY
A battery that does not contain any free liquid electrolyte. The electrolyte is absorbed in glass mat material located in each of the battery’s cells. AGM and VRLA batteries are the same design

AMPERE (Amp., A.)
The unit of measure of the electron flow rate, or current, through a circuit

AMPERE-HOUR (Amp.-Hr., Ah.)
A unit of measurement for a battery’s electrical storage capacity, obtained by multiplying the current in amperes by the time of the hours of discharge. (For example, a battery which delivers 5 amperes for 20 hours delivers 5A x 20Hr = 100Ah of capacity)

ANTIMONY
A hard brittle silver-white metal with a high lustre from the arsenic family. Chemical formula Sb, atomic number 51.

CADMIUM
A metallic element, highly resistant to corrosion, used as protective plating on battery components. Chemical formula Cd, atomic number 48.

CAPACITY
The ability of a fully charged battery to deliver a specified quantity of electricity (Ah) at a given rate (A) over a definite period of time (Hr). The capacity of a battery depends on a number of factors such as: active material weight, density of the active material, adhesion of the active material to the grid, number, design and dimensions of the plates, plate spacing, design of separators, specific gravity and quantity of available electrolyte, grid alloys, final limiting voltage, discharge rate, temperature, internal and external resistance, age, and life history of the battery.

CAPACITY TEST
A test that discharges a battery using a constant current at room temperature until voltage drops to 1.75 volts per cell.

CELL
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 to a 12 volt lead acid battery.

CHARGED
A battery cell’s maximum ability to deliver current (amps). The positive plates contain a maximum amount of lead oxide and a minimum of lead sulphate and the negative plates contain a maximum of sponge lead and a minimum of sulphate. The electrolyte is at maximum specific gravity.

CHARGED AND DRY (DRY CHARGED)
A battery assembled with dry, charged, plates and no electrolyte.

CHARGED AND WET (WET CHARGED)
A fully charged battery containing electrolyte (ready to be installed)

CHARGING
The process of converting electrical energy to stored chemical energy

CHARGING RATE
The current (amps) in amperes at which a battery is charged.

CIRCUIT
An electrical circuit is the path followed by a flow of electrons. A closed circuit is a complete path. An open circuit has a broken, or disconnected, path.

CIRCUIT (SERIES)
A circuit which only has one path for the flow of current. Batteries arranged in series are connected with the negative of the first to the positive of the second, negative of the second to the positive of the third and so on. If two 12 volt batteries of 50 Ah capacity each are connected in series, the circuit voltage is equal to the sum of the two battery voltages, or 24 volts, and the ampere-hour capacity of the combination is 50 Ah.

CIRCUIT (PARALLEL)
A circuit provides more than one path for the flow of current. A parallel arrangement of batteries (of like voltages and capacities) has all positive terminals connected to a conductor and all negative terminals connected to another conductor. If two 12 volt batteries of 50 Ah capacity each are connected in parallel, the circuit voltage is 12 volts and the ampere-hour capacity of the combination is 100 Ah.

COLD CRANK RATING
The number of amperes a lead-acid battery at zero degrees Fahrenheit (-17.8 degrees centigrade) can deliver for 30 seconds and maintain at least 1.2 volts per cell.

CONSTANT CURRENT CHARGE
A battery charger that produces a constant current (amps) during the charging process

CORROSION
The destructive chemical reaction of a liquid electrolyte with a reactive material. (e.g. dilute sulphuric acid on iron, producing corrosion products such as rust.) Battery terminals are subject to corrosion if they are not properly maintained.

CURRENT
The rate of flow of electricity, or the movement of electrons along a conductor. It is comparable to the flow of a stream of water. The SI unit of measure for current is the ampere (A)

CURRENT (ALTERNATING) (AC)
A current that varies periodically in magnitude and direction. A battery does not deliver alternating current.

CURRENT (DIRECT) (DC)
An electrical current flowing in an electrical circuit in one direction only. A battery delivers direct current (DC) and must be recharged with direct current in the opposite direction of the discharge.

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

DISCHARGE RATE
Any specified amperage rate at which a battery is discharged

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

ELECTROLYTE
In a lead-acid battery, the electrolyte is sulphuric acid diluted with water. It is a conductor that supplies water and sulphate for the electrochemical reaction.

PbO2 + Pb + 2H2SO4 = 2PbSO4 + 2H2O

ELEMENT
In a battery a set of positive and negative plates assembled with separators.

FLOAT CHARGE
Recharge voltage rate that is slightly higher than the open circuit voltage (OCV) of a battery

FORMING
In battery manufacturing, formation is the process of charging the battery for the first time. Electrochemically, formation changes the lead oxide paste on the positive grids into lead dioxide and the lead oxide paste on the negative grids to metallic sponge lead.

GLASS MAT
Fabric made from glass fibres with a polymeric binder, such as styrene or acrylic, which is used to help retain positive active material. Glass mats also absorb electrolyte in an AGM battery.

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

GROUND
The reference potential of a circuit. In automotive use, the result of attaching one 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.

HYDROMETER
A float type device used to determine the state of charge of a battery by measuring the specific gravity of the electrolyte. (i.e. the concentration of sulphuric acid in the electrolyte).

LEAD
A chemical element, the principal constituent of a lead acid battery. Chemical formula Pb, atomic number 82.

LEAD ANTIMONY
A metal alloy commonly used in battery castings or plates.

LEAD CALCIUM
A lead base alloy sometimes used for battery components in place of antimonial lead alloys.

LEAD PEROXIDE
A brown lead oxide which is the positive material in a fully formed positive battery plate.

LEAD SPONGE
The chief component of the active material of a fully formed negative battery cell plate.

LEAD SULPHATE
A compound that results from the chemical reaction of sulphuric acid on oxides of lead within a battery cell.

SULPHURIC ACID
The principal acid compound of Sulphur. Sulphuric Acid in diluted form is the electrolyte of a lead acid battery. Chemical formula H2SO4.

TRICKLE CHARGE
A low rate continuous charge approximately equal to a battery’s internal losses and capable of maintaining a battery at a fully charged state.

LOAD TESTER
An instrument which draws current (discharges) from a battery using an electrical load while measuring voltage. It determines the battery’s ability to perform under actual discharge conditions.

LOW WATER LOSS BATTERY
A battery which does not require periodic water addition under normal conditions. Also known as a maintenance free battery.

MILLIAMPERE
One thousandth of an ampere (amp)

MODIFIED CONSTANT VOLTAGE CHARGE
A charge in which the charging voltage is held constant while a fixed resistance is inserted in the battery charging circuit causing a rising voltage as charging progresses.

NEGATIVE
Designating, or pertaining to, electrical potential. The negative battery terminal is the point from which electrons flow during discharge.

NEGATIVE PLATE
The grid and active material that current flows to from the external circuit when a battery is discharging.

NEGATIVE TERMINAL
The battery terminal from which current flows through an external circuit to the positive terminal when a battery discharges.

OHM
The SI unit of electrical resistance. Also a unit of electrical impedance within an electrical circuit.

OHM'S LAW
Expresses the relationship between volts (v) and amperes (A) in an electrical circuit with resistance (R). It can be expressed as follows

V = IR

Volts (v) = amperes (I) x Ohms (R). If any two of the three values are known, the third can be calculated using the above calculation.

OPEN CIRCUIT VOLTAGE
The voltage of a flooded lead acid battery when it is not delivering or receiving power. It is 2.11 volts for a fully charged battery cell, or 12.66 for a fully charged 12 volt battery (6.33 for a 6 volt battery).

POSITIVE
Designating, or pertaining to, a kind of electrical potential; opposite of negative. A point or terminal on a battery having lower relative electrical potential.

POSITIVE TERMINAL
The battery terminal that current flows toward in an external circuit when the battery is discharging.

PRIMARY BATTERY
This type of battery can store and deliver electrical energy, but cannot be recharged.

RATED CAPACITY
Amp Hours of discharge that can be removed from a fully charged battery at a specific constant rate.

RESERVE CAPACITY RATING
The time in minutes that a new, fully charged, battery will deliver 25 amperes at 80 degrees Fahrenheit 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.

RESISTANCE (ELECTRICAL)
The opposition to the free flow of current in a circuit. It is commonly measured in Ohms.

SECONDARY BATTERY
A battery which can store and deliver electrical energy and can be recharged by passing direct current through it in a direction opposite to that of discharge.

SELF DISCHARGE
Gradual loss of electrical energy when a battery is stored.

SEPARATOR
A divider between the positive and negative plates of an element which allows the flow of current to pass through it. Separators are made from numerous materials, such as polyethylene, polyvinyl chloride, rubber, glass fibre, cellulose, etc.

SHORT CIRCUIT
An unintended current by-pass in an electrical 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.

SPECIFIC GRAVITY (SG)
The density of a liquid compared to the density of water. The specific gravity of the electrolyte is the weight of the electrolyte compared to the weight of an equal volume of pure water.

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

VOLT
The SI unit of measure for electrical potential.

VOLTAGE
The difference in electrical potential that exists between the terminals of a battery or any two points in an electrical circuit.

VOLTAGE DROP
The net difference in the electrical potential (voltage) when measured across a resistance or impedance (ohms). Its relationship to current is described in Ohm's Law.

VRLA
Valve Regulated Lead Acid. A sealed battery that features a safety valve designed to release excessive internal pressure while maintaining sufficient pressure for recombination of oxygen and hydrogen into water. VRLA and AGM refer to the same type of battery design.

WATT
The SI unit for measuring electrical power. (i.e. the rate of doing work, in moving electrons by, or against, an electrical potential.

Formula: Watts = Amperes x Volts

WATT-HOUR (Watt-Hr., WH)

The unit of measure for electrical energy expressed a Watts x Hours.