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Flashcards in Batteries Deck (16)
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Primary cells

Not rechargeable
Disposable, Duracell batteries
Emergency lightning
Carbon zinc cells


Secondary cells

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


Lead acid batteries - 12V

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


Connecting the cells in series

Voltage will go up but the capacitance will remain the same


Alkaline battery - 12v

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


Memory effect - Ni Cad

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


Cross vent system - batteries

Air is fed through the battery to keep it cool

Could be fed from outside or the cabin


Non spill battery vent

A vent allows gasses to escape through the battery vent outlet

Lead weight seals vent in the event of negative Gs


In the event of electrolyte spillage

Use an alkaline to neutralise

Bicarbonate soda for acid batteries

Basic acid for alkaline batteries


Battery capacity and when it is checked

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


The effect on temp to capacity

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


The effect of potential difference while charging a battery

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


Thermal r/y

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


Emergency batteries

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

Lights = 10mins


Batteries in parallel

Increases capacity but voltage remains the same


Batteries in series

Increases voltage but capacity remains the same