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20-Hour Rate
The number of amps that can be withdrawn at a constant rate for 20 hours @ 80 F before voltage drops to 1.75 volts per cell (discharged).

Refers to sulphuric acid (H2SO4), the active component of the electrolyte, or a mixture of sulphuric acid and water.

Active Material
The active portion of the battery plates; peroxide of lead on the positives and spongy metallic lead on the negatives.

As used in battery practice, a homogeneous combination of lead and antimony.

Alternating Current
Electric current which does not flow in one direction only, like direct current, but rapidly reverses its direction or "alternates" in polarity so that it will not charge a battery.

The unit of measure of the rate of flow of electric current.

Ampere Hour
The product resulting from multiplication of amperes flowing by time of flow in hours, e.g., a battery supplying 10 amperes for 8 hours gives 80 ampere hours. See note under "Volt?' for more complete explanation of current flow.

Two or more electrical cells, electrically connected so that combination furnishes current as a unit.

Battery Terminals
Devices attached to the positive post of one end cell and the negative of the other, by means of which the battery is connected to the circuit.

Warping or bending of the battery plates.

A term used to describe the operation of joining two pieces of lead by melting them at practically the same instant so they may run together as one continuous piece. Usually done with mixture of oxygen and hydrogen or acetylene gases, hydrogen and compressed air, or oxygen and illuminating gas.

A metal used in about the shape of a pencil for obtaining voltage of positive or negative plates. It is dipped in the electrolyte but not allowed to come in contact with plates.

The number of ampere hours a battery can supply at a given rate of current flow after being fully charged, e.g., a battery may be capable of supplying 10 amperes of current for 8 hours before it is exhausted. Its capacity is 80 ampere hours at the 8 hours rate of current flow. It is necessary to state the. rate of flow, since same battery if discharged at 20 amperes would not last for 4 hours but for a shorter period, say 3 hours. Hence, its capacity at the 3 hour rate would be 3x2O=60 ampere hours.

The containing box which holds the battery cells.

The battery unit, consisting of an element complete with electrolyte, in its jar with cover.

Passing direct current through a battery in the direction opposite to that of discharge, in order to put back the energy used on discharge.

Charge Rate
The proper rate of current to use in charging a battery from an outside source. It is expressed in amperes and varies for different sized cells.

The attack of metal parts by acid from the electrolyte; it is the result of lack of cleanliness.

The rubber cover which closes each individual cell; it is flanged for I sealing compound to insure an effective seal.

One charge and discharge.

Specific gravity.

The flow of current from a battery through a circuit, opposite of "charge."

Term frequently applied to cell containing insufficient electrolyte. Also applied to certain conditions of shipment of batteries.

The conducting fluid of electro-chemical devices; for lead-acid storage batteries it consists of about two parts of water to one of chemically pure sulphuric acid, by weight.

Positive group, negative group and separators.

The result of circulation and diffusion within the cell which accompanies charge and discharge. Difference in capacity at various rates is caused by the time required for this feature.

Term used to describe the making uniform of varying specific gravities in different cells of the same battery, by adding or removing water or electrolyte.

Loss of water from electrolyte from heat or charging.

Filling Plug
The plug which fits in and closes the orifice of the filling tube in the cell cover.

Finishing Rate
The current in amperes at which a battery may be charged for twenty-four hours or more. Also the charging rate used near the end of a charge when cells begin to gas.

Electro-chemical process of making pasted grid or other plate, types into storage battery plates. (Often confused with Developing.)

Freshening Charge
A charge given to a battery which has been standing idle, to keep it fully charged.

The giving off of oxygen gas at positive plates and hydrogen at negatives, which begins when charge is something more than half completed-depending on the rate.

A contraction of the term "specific gravity," which means the density compared to water as a standard.

The metal framework of a plate, supporting the active material and provided with a lug for conducting the current and for attachment to the strap.

A set of plates, either positive or negative, joined to a strap. Groups do not include separators.

An instrument for measuring the specific gravity of the electrolyte.

The hard rubber container holding the element and electrolyte.

Lead Burning
Making a joint by melting together the metal of the parts to be joined.

The extension from the top frame of each plate, connecting the plate to the strap.

Maximum Gravity
The highest specific gravity which the electrolyte will reach by continued charging, indicating that no acid remains in the plates.

The terminal of a source of electrical energy as a cell, battery or generator through which current returns to complete circuit. Generally marked "Neg."

The unit of electrical resistance. The smaller the wire conductor the greater is the resistance. Six hundred and sixty-five feet of No. 14 wire (size used in house lighting circuit) offers I ohm resistance to current flow.

The carrying of discharge beyond proper cell voltage; shortens life if carried far enough and done frequently.

The mixture of lead oxide or spongy lead and other substances which is put into grids.

The combination of grid and paste properly "formed." Positives are reddish brown and negatives slate gray.

An electrical condition. The positive terminal (or pole) of a cell or battery or electrical circuit is said to have positive polarity; the negative, negative polarity.

The terminal of a source of electrical energy as a cell, battery or generator from which the current flows. Generally marked "Pos." or It+."

The portion of the strap extending through the cell cover, by means of which connection is made to the adjoining cell or to the car circuit.

Number of amperes for charge or discharge. Also used to express time for either.

Reserve Capacity Rating
The time in minutes that the battery will deliver 25 amperes at 80 degrees. This rating represents the time the battery will continue to operate essential accessories during night and bad weather driving if the alternator or Generator Fails.

Material (usually lamps or wire) of low conductivity inserted in a circuit to retard the flow of current. By varying the resistance, the amount of current can be regulated. Also the property of an electrical circuit whereby the flow of current is impeded. Resistance is measured in ohms. Analogous to the impediment offered by wall of a pipe to flow of water therein.

Reversal of polarity of cell or battery, due to excessive discharge, or charging in the wrong direction.

Making tight joints between jar and cover; usually with a black, thick, acid-proof compound.

Loosened or worn out particles of active material fallen to the bottom of cells; frequently called' "mud."

An insulator between plates of opposite polarity; usually of wood, rubber or combination of both. Separators are generally corrugated or ribbed to insure proper distance between plates and to avoid too great displacement of electrolyte.

Short Circuit
A metallic connection between the positive and negative plates within a cell. The plates may be in actual contact or material may lodge and bridge across. If the separators are in good condition, a short circuit is unlikely to occur.

Specific Gravity
The density of the electrolyte compared to water as a standard. It indicates the strength and is measured by the hydrometer.

The result of giving insufficient charge in relation to the amount of discharge, resulting in poor service and injury to the battery.

The leaden casting to which the plates of a group are joined.

Common term for lead sulphate. (PbSO4.)

Term used to describe cells in an under-charged condition, from either over- discharging without corresponding long charges or from standing idle some time and being self discharged.

Part to which outside wires are connected.

Vent, Vent Plug or Vent-Cap
Hard or soft rubber part inserted in cover to retain atmospheric pressure within the cell, while preventing loss of electrolyte from spray. It allows gases formed in the cell to escape, prevents electrolyte from spilling, and keeps dirt out of the cell.

The commercial unit of pressure in an electric circuit. Voltage is measured by a voltmeter. Analogous to pressure or head of water flow through pipes. NOTE. - Just as increase of pressure causes more volume of water to flow through a given pipe so increase of voltage (by putting more cells in circuit) will cause more amperes of current to flow in same circuit. Decreasing size of pipes is increasing resistance and decreases flow of water, so also introduction of resistance in an electrical circuit decreases current flow with a given voltage or pressure.

The commercial unit of electrical power, and is the product of voltage of circuit by amperes flowing. One ampere flowing under pressure of one volt represents one watt of power.

Watt Hour
The unit of electrical work. It is the product of power expended by time of expenditure, e.g., 10 amperes flowing under 32 volts pressure for 8 hours gives 2560 watt hours.

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