3.5 Flashcards
What is the resistance present inside a battery connected to a load called?
Internal resistance (IR)
What does the internal resistance do?
Restricts the movement of current inside any battery.
What is OCV and CCV?
Open circuit voltage.
Closed circuit voltage.
What happens to the battery’s internal resistance as the battery discharges?
Increases
How long would it be until the IR of a battery will adversely affect an aircraft electrical system?
Until it becomes 75% discharged.
What happens if the terminals of a battery are not very clean?
Connections will not be very good.
What is an example of a primary cell?
Zinc-carbon battery.
What voltage does a zinc-carbon battery provide?
Low voltage DC supply.
Carbon (positive)
Zinc (negative)
What prevents the build of hydrogen at the positive electrode of the cell?
Manganese’ dioxide
What part of the battery deteriorates as it discharges?
The negative plate as material goes irreversibly into solution with electrolyte.
Are primary or secondary cells rechargeable?
Secondary.
What are secondary cells made from in aircraft storage batteries?
Lead acid or nickel cadmium
What voltage do lead acid cells have?
2V charged.
1.83V final discharge.
What does a lead acid cell consist of?
Positive plate (lead peroxide)
Negative plate (pure spongy lead)
Liquid electrolyte (sulphuric acid 30%, water 70%)
What happens during a discharge of a lead acid cell?
Sulphuric acid in electrolyte breaks up into hydrogen ions carrying positive charge, sulphate ions carrying negative charge.
When is a lead acid battery said to be discharged?
Both plates are coated in lead sulphate and no further chemical action can take place.
How is a lead acid battery charged?
Sulphate ions driven back into solution in electrolyte and combine with hydrogen ions of the water, forming sulphuric acid.
What voltage do nickel cadmium cells have?
1.2V and 1V when discharged.
What is in the positive plate made up of in a nickel cadmium cell?
Nickel oxyhydroxide
What is the negative plate made up of in a nickel cadmium cell?
Metallic cadmium.
What is the electrolyte in a nickel cadmium cell?
Potassium hydroxide.
What are advantages of nickel cadmium cells to lead battery cells?
Better power to weight ratio.
Closed circuit voltage remains constant throughout discharge.
Larger capacity.
What are the disadvantages of nickel cadmium cells to lead battery cells?
More costly.
Larger.
If a higher voltage is needed, what can we do to batteries?
Connect them in series.
What can be done to circuits for high current purposes?
Connect batteries in parallel.
