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TERMINOLOGY GUIDE Absorbed glass mat (AGM) Type of lead-acid battery in which the electrolyte is absorbed into a fibreglass mat. The plates in an AGM Battery are generally flat, but in cylindrical AGM s, the plates are thin and wound in a tight spiral, sometimes referred to as spiral wound.

Ampere, or Amp The unit of measurement of current flow. One volt placed across a one ohm resistance will cause a current of one Amp to flow. One amp for one hour is called an amp-hour or Ah.

Ampere-hour or Ah The unit of electrical capacity - this tells you how much energy the battery will store. Current multiplied by time in hours equals ampere-hours. A current of one amp for one hour would be one amp-hour; a current of 3 amps for 5 hours would be 15 Ah.

Battery A battery is an electric device that converts chemical energy into electrical energy, consisting of a group of electric cells that are connected to act as a source of direct current. Batteries are made of connected cells encased in a container and fitted with terminals to provide a source of direct electric current at a given voltage. A battery is characterised by its chemical composition (combination of metal(s) and electrolyte used), voltage, size, terminal arrangements, capacity and rate of capability or more cells.

Battery pack (bank) Set of any number of (preferably) identical batteries or individual battery cells. They may be configured in a series, parallel or a mixture of both to deliver the desired voltage, capacity, or power density.

Cell Basic functional unit providing a source of electrical energy by direct conversion of chemical energy. A cell consists of two dissimilar substances, a positive electrode and a negative electrode, that conduct electricity, and a third substance,

an electrolyte, that acts chemically on the electrodes. The two electrodes are connected by an external circuit. The electrolyte functions as an ionic conductor for the transfer of the electrons between the electrodes.

Cycle A cycle is a somewhat arbitrary term used to describe the process of discharging a fully charged battery down to a particular state of discharge. The term deep cycle refers to batteries in which the cycle is from full charge to 80% discharge. A cycle for an automotive battery is about 5%, and for telephone batteries is usually 10%.

Electrolyte Conductive chemical (such as acid), usually liquid, solid or gel, in which the flow of electricity takes place within the battery, and which supports the chemical reactions required.

Lead-acid battery Lead-acid batteries are still the most common type of rechargeable automotive batteries, after over 150 years in use. Their power-to-weight ratio is often quite good. Also, the energy-to-volume ratio is good compared to other types of batteries. They are more economical and supply high burst of energy needed to start engines.

Separator Material with an ion permeable structure that provides electrical insulation between plates of opposite polarity in a cell.

SLI Starting, Lighting and Ignition.

Storage battery A storage battery consists of several cells connected to each other. Each cell contains a number of alternately positive and negative plates, a separator and electrolyte. The positive plates of the cell are connected to form the positive electrode; similarly, the negative plates form the negative electrode.

During the process of charging, the cell is made to function in reverse of its discharging operation; i.e., current is forced through the cell in the opposite direction, causing the reverse of the chemical reaction that ordinarily takes place during discharge, so that electrical energy is converted into stored chemical energy.

Valve-regulated sealed battery Battery in which cells are closed but have an arrangement (valve) which allows the escape of gas if the internal pressure exceeds a predetermined value.

Vented cell Cell with a cover having an opening through which products of electrolysis and evaporation are allowed to escape freely from the cell, in order to avoid excessive pressure inside the cell.

Vent valve Part of certain types of batteries which permits the escape of gas in the case of excess internal pressure but which does not allow the entry of air.

Volt (V) The unit of measurement of electrical potential or pressure . Most batteries come in 6, 12, & 24 volt. A single cell is 2 volts.

Watt (W) A unit of power. 1W is 1 Joule per second (J/s), or also 1 amp multiplied by 1 volt (AxV). 1 amp at 120 volts gives the same result in watts as 10 amps at 12 volts.

Watt-hour (Wh) Watt-hours measure amounts of energy for a specific period of time. For example if a 60W light bulb is on for one hour, then that light bulb will have used 60Wh of energy. If left on for two hours, then the 60W light bulb will have used 120 Wh of energy.