Batteries

Question 1

Primary cells

Answer 1

Not rechargeable
Disposable, Duracell batteries
Emergency lightning
Carbon zinc cells

Question 2

Secondary cells

Answer 2

Rechargeable
Used for main batteries in a/c
Lead acid
Nickel cadmium

Question 3

Lead acid batteries - 12V

Answer 3

When fully charged - 6x 2.2v cells
Fully discharged = 1.8v

Terminal voltage of 13.2v off load
Nominal voltage of 12v

Common in light a/c

Electrolyte SG - fully charged = 1.27
Discharged = 1.1

Question 4

Connecting the cells in series

Answer 4

Voltage will go up but the capacitance will remain the same

Question 5

Alkaline battery - 12v

Answer 5

Potassium hydroxide and Nickel oxide = electrolyte - constant SG when charged - 1.26 when discharged

10 cells - each cell charged = 1.3v
Discharged = 1.1v

Terminal voltage = 13v off load
Ni ld tern= 1.3v
Nominal voltage = 12v

Question 6

Memory effect - Ni Cad

Answer 6

The effects of crystalline growth - they grow to big and conceal the active material from the electrolyte

Occurs when a Ni Cad battery is recharged before it is fully discharged

Can cause high self discharge or electrical short

Question 7

Cross vent system - batteries

Answer 7

Air is fed through the battery to keep it cool

Could be fed from outside or the cabin

Question 8

Non spill battery vent

Answer 8

A vent allows gasses to escape through the battery vent outlet

Lead weight seals vent in the event of negative Gs

Question 9

In the event of electrolyte spillage

Answer 9

Use an alkaline to neutralise

Bicarbonate soda for acid batteries

Basic acid for alkaline batteries

Question 10

Battery capacity and when it is checked

Answer 10

Depends on size and number of plates, measure of the total energy - bigger battery = more chemicals

Measured in amp hours e/g 25AH = 25 amps for 1 hour or 25 hours for 1 amp

Checked at 3 monthly intervals, min capacity is 80% of the rated capacity

Question 11

The effect on temp to capacity

Answer 11

If a battery is reduced to -10 the capacity could be reduced to 10% of its rating

Thermal blankets, being charged at a low rate combats this

Question 12

The effect of potential difference while charging a battery

Answer 12

PD will be building during the charging and will oppose the charging current

To achieve the voltage req - charges at 2vdc higher for every 12vdc

12v battery = 14v charge

Question 13

Thermal r/y

Answer 13

As an alkaline battery warms up the resistance decreases and the current increases which makes it even warmer

Thermal r/y = batttery has overheated and caused a failure - does not happen in lead

Question 14

Emergency batteries

Answer 14

Must last at least 30 mins after total failure of the electrical generating system

Lights = 10mins

Question 15

Batteries in parallel

Answer 15

Increases capacity but voltage remains the same

Question 16

Batteries in series

Answer 16

Increases voltage but capacity remains the same