Task 1
Secondary Batteries Summary
Students to complete the Table 2 below by using Table 1 to match the batteries properties.
Table1
Boric Acid Nickel oxide
SG1.240-
1.300
Spongy lead
Cadmium
SG 1.270 Sulphuric acid
Lead peroxide
Sodium bicarbonate
Potassium hydroxide
Table 2
Type Positive
Plate
Lead
Peroxide
Negative
Plate
Spongy lead
Electrolyte Spillage Specific
Gravity
1.270
Lead
–
Acid
Alkaline
(Ni – Cad)
Nickel
Oxide
Sulphuric acid
Cadmium Potassium hydroxide
Sodium bicarbonate
Boric Acid 1.240 -
1.300
Task 2
Briefly describe the difference between a Primary Cell and a Secondary cell with reference to the following
(a) Primary Cell
(b) Secondary Cell
(a) A primary cell is any kind of battery in which the electrochemical reaction is not reversible. A common example of a primary cell is the disposable battery. Unlike a secondary cell, the reaction cannot be reversed by running a current into the cell; the chemical reactants cannot be restored to their initial position and capacity. Primary batteries use up the materials in one or both of their electrodes
(b) A rechargeable battery or storage battery is a group of one or more electrochemical cells. They are known as secondary cells because their electrochemical reactions are electrically reversible. Rechargeable batteries come in many different shapes and sizes, ranging anything from a button cell to megawatt systems connected to stabilize an electrical distribution network.

Task 3
With reference to Ni – Cad aircraft batteries state the following
(a) What is the battery voltage
(b) How can you convert it to 115 VAC 400Hz
(c) What limits the power usage of the battery
(a) 28 VDC
(b) Static Inverter
(c) Short life of battery

Task 4
Using the chart below compare the advantages and disadvantages of the
Lead acid battery to the Ni – Cad battery (alkaline)
(a)
Lead Acid
Advantages
 Less expensive
 Retains charge (during storage)
 Simple charger
 Cell voltage 1.5V (Ni Cad
1.2V)
Ni - Cad
Disadvantages
 Only supplies half its rated capacity
 Size
 Electrolyte (Sulphuric acid)
Advantages

Smaller
 Lighter
 Capacity not affected by high discharge currents
 Provides nearly all rated capacity
Disadvantages

Higher cost
 Negative temp coefficient
 Complicated charging

Loss of charge (1% per day)
 Lower cell voltage 1.2

(b) Using your tables from above what battery would you select for your aircraft and why?
Answer
Ni Cad
 Smaller
 Lighter

Capacity not affected by high discharge currents
 Provides nearly all rated capacity