Applications of Cells and Batteries Flashcards
What is the difference between a cell and a battery?
A cell is the fundamental unit consisting of a positive electrode, a negative electrode, and an electrolyte solution. A battery is an arrangement of two or more cells (although a single dry cell is commonly called a battery)
What is the difference between a primary cell and a secondary cell?
A primary cell is chemically irreversible after the active ingredients have been consumed, whereas the secondary cell can be recharged
What does the term “dry cell” imply?
The electrolyte is combined with various ingredients to form a paste or gel, rather than a liquid form
What is another name for the carbon-zinc dry cell?
The Leclanche cell
Which primary cell with similar features is considered as the heavy-duty counterpart to the carbon-zinc cell?
zinc-cloride cell
In order to form a 9V transistor battery, how must the individual carbon-zinc cells be connected?
In series (six 1.5V cells)
What two advantages does the alkaline cell have over the standard carbon-zinc cell?
Greater energy capacity; longer life (during both discharge and storage)
In what type of case shape are silver-oxide and mercury cells commonly constructed?
Miniture “button” case styles
Which type of primary cell has the highest open-circuit voltage?
Lithium cell (3V)
Which type of primary cell is generally considered as the most expensive for its energy capacity?
Silver-oxide cell
What is a storage battery?
A large-capacity rechargeable battery
What is meant by the term “wet cell”?
A storage (secondary) battery that has a liquid electrolyte
What are the four main categories of secondary batteries?
Automotive (SLI) batteries; motive power batteries; standby batteries; portable batteries
The relative density of the electrolyte in a battery is measured with an instrument called a ________
Hydrometer
What is the relative density expected for a fully charged portable battery?
Between 1280 and 1300 relative density
What is the relative density expected for a fully charged stationary battery?
Between 1210 and 1225 relative density
What happens to the internal resistance of a lead-acid battery during normal discharge?
The internal resistance increases during discharge, resulting in a decrease of the battery’s terminal (working) voltage
What is the terminal voltage expected for a fully charged, six-cell, lead-acid battery?
13.2V (Six cells at 2.2V per cell)
How many cells are in a conventional 12V lead-acid battery?
6
How many cells are in a conventional 12V nickel-iron battery?
10
How many cells are in a conventional 12V nickel-cadmium battery?
10
Compared to acid (in lead-acid batteries), what type of electrolyte is used in nickel-cadmium batteries?
Alkaline
What is the relative density expected for a fully charged nickel-cadmium stationary battery?
Approximately 1200 relative density
The relative density of a nickel-cadmium battery cannot be used as a reliable measurement of its state of charge. Why not?
The relative density does not change significantly during discharge (it remains constant), so it cannot be used to determine the state of charge for alkaline batteries
How can the memory effect be overcome in a nickel-cadmium cell?
Discharge the battery completely; then recharge to full capacity at the recommended charging current (this may have to be repeated several times)
What are three tasks involved in the monthly maintenance of lead-acid station batteries?
- Measuring relative density of pilot cells
- Recording temperature-corrected hydrometer readings
- Checking electrolyte levels and adding water as necessary
- Measuring and recording cell voltages
- Cleaning accumulated dust from cell tops
What are three items of personal protective equipment required when servicing wet-cell batteries?
- Eye goggles
- Rubber gloves
- Rubber apron
Why is it important that there be no smoking or open flames near stationary battery installations?
Because of the explosion hazard resulting from the presence of hydrogen gas
What type of electrolyte solution is used for lead-acid cells?
Sulphuric acid and water
What type of electrolyte solution is used for alkaline cells?
Potassium hydroxide and water
Why is it good practice to insulate tool handles for use on battery installations?
To protect against electrical shock and accidental short circuiting of cells
Would the indicator float in a hydrometer sink deeper or float higher in a fully charged lead-acid battery?
Float higher
If the relative density of an electrolyte read 1280 at 30°C, would you expect the temperature-corrected relative density at 25°C to be higher or lower in value?
Higher
Why should metal containers not be used to store distilled water for batteries?
Metal containers may contaminate the water (by leaching)
Why should a non-metallic bristle brush be used to clean the tops of battery cells?
Metal bristles are conductive and may cause a short circuit
Voltmeter readings of cell voltages should normally be recorded to how many decimal places?
Two at least two decimal places (one-hundredth)
What is the usual charging time required to fully restore a stationary battery from its discharged condition?
Approximately 8 hours
What is the name given to the charging system in which the battery and its load are connected in parallel with the rectified power source?
Float charge
What type of charge is given to a standby battery in order to maintain it in a fully charged condition?
Trickle charge
What are the two fundamental methods used for charging batteries?
- Constant-voltage charging
- Constant-current charging
In accordance with the CEC, what is the minimum spacing between battery cells?
10mm. See Rule 26-550(2)
The mounting surface of a battery rack is usually required to have a covering of insulating material with a dielectric strength of at least ___V
1500V. See Rule 26-550(1)(c)
Sufficient ventilation should be provided in battery rooms to prevent the hydrogen gas from building up to a level of ___% by volume in the room air at any time
2%. See Rule 26-546-Appendex B
Lead-acid batteries should not be located in areas where the temperature is likely to fall below ___°C or rise above ____°C
-7°C, 45°C. See Rule 26-546-Appendex B
Is it permitted to use MI cable for wiring between batteries?
Yes, if adequately protected against corrosion (where it may be in direct contact with acid or acid spray). See Rule 26-552(1)(d)
