AME Aircraft Electrical Systems 2

Question 1

What is the primary hazard associated with a nickel-cadmium battery that is charged with excessive current at high temperature?

Accepted Answer

Thermal runaway

Answer

Rising temperature lowers internal resistance in a NiCd cell, so it draws more current and heats further until thermal runaway occurs.

Question 2

How is the state of charge of a nickel-cadmium battery determined?

Accepted Answer

It cannot be determined accurately by specific gravity; a measured discharge or charge is required

Answer

NiCd electrolyte specific gravity does not change appreciably with charge, so a hydrometer cannot indicate state of charge.

Question 3

Why should tools and equipment used to service lead-acid batteries never be used on nickel-cadmium batteries?

Accepted Answer

The sulfuric acid can contaminate and damage the alkaline NiCd electrolyte

Answer

Acid residue will neutralize and contaminate the potassium hydroxide electrolyte and ruin NiCd cells.

Question 4

When the voltage of a fully charged 24-volt lead-acid aircraft battery is measured, approximately how many cells does it contain?

Accepted Answer

12

Answer

Each lead-acid cell produces about 2.1 volts, so a 24-volt battery has 12 cells.

Question 5

What is the purpose of a battery vent system with a sump jar containing a bicarbonate of soda pad on a lead-acid installation?

Accepted Answer

To neutralize acid fumes before they are discharged overboard

Answer

The sump jar neutralizes corrosive acid vapors so they do not damage the aircraft structure.

AME - Aircraft Maintenance Engineer Practice Test