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A current of one ampere flowing for one hour.
Ampere-hour
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A group of two or more connected voltaic cells. Converts chemical energy to electrical energy. This conversion enables electrical power to be stored.
Battery
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How long the storage battery will operate at a certain discharge rate and is rated in ampere-hours.
Capacity
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If the electrolyte of a cell is a paste.
Dry cell
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A metallic compound, or metal, which has an abundance of electrons or an abundance of positive charges.
Electrode
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A solution that is capable of conducting an electric current. May be a liquid or a paste.
Electrolyte
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All the positive terminals are connected together, and all the negative terminals are connected together. The total voltage output of a battery connected is the same as that of a single cell.
Parallel cells
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Cells that cannot be returned to good condition, or recharged after their voltage output has dropped to a value that is not usable
Primary cells
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Cells that can be recharged to nearly their original condition.
Secondary cells
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The positive terminal of one cell is connected to the negative terminal of the next cell. The current flow is the same as for one cell.
Series cells
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The time that a battery may be stored and not lose more than 10 percent of its original capacity.
Shelf life
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The ratio comparing the weight of any liquid to the weight of an equal volume of water.
Specific gravity
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A combination of materials used to convert chemical energy into electrical energy.
Voltaic cell
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If the electrolyte of a cell is a solution.
Wet cell
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A combination of materials used to convert chemical energy into electrical energy.
voltaic cell
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State the purpose of a battery
- The purpose of a battery is to store chemical energy and to convert this chemical energy into
- electrical energy when the need arises.
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Describe the operation of a simple voltaic cell.
a chemical cell (or voltaic cell) consists of two electrodes of different types of metals or metallic compounds and an electrolyte solution that is capable of conducting an electric current.
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State the chemical equation for the reaction that occurs when a lead-acid battery is being charged or discharged.
When a lead-acid battery is discharged, the electrolyte (H2SO4) divides into H2 and SO4. The H2 will combine with some of the oxygen that is formed on the positive plate to produce water (H2O), and thereby reduce the amount of acid in the electrolyte. The sulfate (SO4) combines with the lead (Pb) of both plates, forming lead sulphate (PbSO4).
As a lead-acid battery is charged in the reverse direction, the action described in the discharge is reversed.
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Explain the relationship between specific gravity and state of charge of a lead-acid battery.
The electrolyte in a lead-acid battery plays a direct role in the chemical reaction. The specific gravity decreases as the battery discharges and increases to its normal, original value as it is charged. The decrease in specific gravity on discharge is proportional to the ampere-hours discharged. However, while charging a lead-acid battery, the rise in specific gravity is not uniform, or proportional, to the amount of ampere-hours charged
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Describe the relationship between total battery voltage and cell voltage for a series-connected battery
When several cells are connected in series, the total voltage output of the battery is equal to the sum of the individual cell voltages
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State the advantage of connecting a battery in parallel with respect to current-carrying capability.
- Cells connected in parallel, give the battery a greater current capacity. When cells are connected in parallel, all the
- positive terminals are connected together, and all the negative terminals are connected together. The total voltage
- output of a battery connected in parallel is the same as that of a single cell.
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State the difference between primary and secondary cells with respect to recharge capability
Cells that cannot be returned to good condition, or recharged after their voltage output has dropped to a value that is not usable, are called primary cells
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State the units of battery capacity.
The capacity of a storage battery determines how long the storage battery will operate at a certain discharge rate and is rated in ampere-hours. For example, a 120 ampere-hour battery must be recharged after 12 hours if the discharge rate is 10 amps.
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State the advantage of each of the following types of batteries:
a. Carbon-zinc cell
b. Alkaline cell
c. Nickel cadmium cell
d. Edison cell
e. Mercury cell
- The advantage of a carbon-zinc battery is that it is durable and very inexpensive to produce
- The alkaline cell has the advantage of an extended life over that of a carbon-zinc cell of the same size; however, it is usually more expensive.
- The nickel-cadmium battery has the advantage of being a dry cell that is a true storage battery with a reversible chemical reaction
- Edison Cell has the advantage of being a lighter and more rugged secondary cell than a lead-acid storage battery.
- The mercury cell has the advantage of maintaining a fairly constant output under varying load conditions
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Explain the adverse effects of a shorted cell.
Short circuits cause a great reduction in battery capacity. With each shorted cell, battery capacity is reduced by a percentage equal to one divided by the total number of cells.
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Explain how gas generation can be minimized for a lead-acid battery
To reduce the amount of gassing, charging voltages above 2.30 volts per cell should be minimized
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Explain how heat is generated in a lead-acid battery
Whenever the battery is charged, the current flowing through the battery will cause heat to be generated by the electrolysis of water
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