AS113 - Lecture - Nickel-Cadmium Batteries Flashcards
Ni-Cad batteries require the user to completely use up their capacity before ________.
recharging
______ _____ require higher current for starting.
Turbine Engines
____ _____ has a tendency to build up sulfates on the plates when they are in use, which causes higher resistance and a voltage drop.
Lead acid
_____ battery was developed for aircraft use because it has low internal resistance and voltage stays constant until the battery is discharged.
Ni-Cad
Main disadvantages of a Ni-Cad Battery
Cell Imbalance (Battery Memory)
Heavy in weight
Potential for Thermal Runaway
Nickel-Cadmium Battery Construction
Individual Removable Cells.
The cells are charged to an Open Circuit Voltage (OCV) of 1.55v to 1.80v.
12 volt system 9 or 10 cells 13.95v-18v.
24 volt system 19 or 20 cells 29.45v-36v.
Positive Plates
Powdered nickel sintered (fused) to porous nickel mesh.
Porous mesh impregnated with nickel hydroxide.
Negative plates
Powdered nickel sintered to porous nickel mesh.
Impregnated with cadmium hydroxide.
Plates are separated with a _____ and _____ material.
nylon and cellophane
Nickel-Cadmium Battery
______ is 30% by weight solution of potassium hydroxide and distilled water.
Electrolyte
Nickel-Cadmium Battery
The electrolyte Specific Gravity is ____ to ____ @ room temperature.
1.240 to 1.300
Chemical Changes During Discharge
Cadmium on ________ plates combine with hydroxide ions in electrolyte, which releases electrons.
negative
Chemical Changes During Discharge
Hydroxide on _______ plates goes into the electrolyte solution.
positive
Chemical Changes During Discharge
_____ ______ stays the same, so it does not give an indication of batteries state of charge.
Specific gravity
Chemical Changes During Discharge
Electrolyte liquid level will be at its ______ when a battery is discharged.
lowest
Chemical Changes during charge
The oxygen is driven from ________ plates.
This leaves the metallic cadmium on ________ plates.
This continues until all oxygen is released.
negative
negative
During the charging cycle electrolyte is driven from the ______ and ______ plates.
positive and negative
The liquid level of the electrolyte is at its ___ ____immediately after charging cycle.
This is the proper time to check the electrolyte level.
Check and add distilled water only when battery is fully charged.
highest level
Servicing Ni-Cad Batteries
When cleaning tops of batteries.
Neutralize with ____ ____ or ______ and then flush with clean water.
insure that no neutralizing agents enter into the cells.
boric acid or vinegar
A small accumulation of ______ ______ on top of the cells is common.
potassium carbonate
______ is formed by the electrolyte combining with carbon dioxide.
potassium carbonate
An excessive amount of potassium carbonate is caused by.
Battery was charged to fast.
Level of electrolyte too high.
Internal short circuits.
Battery wont hold a ______.
charged
Internal short circuits.
Check for electrical leakage between cells and steel case with ________.
_______ lead - terminal
_______ lead- case
ammeter
Positive
Negative
When checking the internal short circuit with the ammeter it should not be no more than ____ mA
If its more than ____ mA disassemble and clean and retest .
100
100
In Service Checks
Condition of cell hardware.
Should not have any ______.
Should be properly _______.
Corrosion
Torque
Burn marks will result from improper ______ and ______.
torque and corrosion.
Perform a measured discharge test to determine the ______ _______ of charge of NI-Cad battery
actual state
To perform a measured discharge test.
Fully charge battery use a 5 hour rate (ampere-hours / 5 = charging amps)
adjust electrolyte when fully charged
After performing a measured discharge
If capacity is normal recharged and _______ _______.
If capacity is not normal a
____ _____ may exist
return to service
cell imbalance
Negative plates controls the cell’s voltage characteristics.
Lower charge efficiency in positive plate.
Cell Imbalance
Imbalance between Negative and Positive plates.
Cell Imbalance
Continue to discharge the battery but at a slower rate.
When cell voltage gets to .2vdc per cell, short the cells with shorting straps
Sometimes a load bank is used
Leave straps on 3 to 8 hours.
This will rid of cell imbalance
Deep Cycle or Equalization
Charge per manufactures recommendations.
Monitor battery during charging cycle.
Looking for cell differential.
Nearing full charge- gases are released.
OCV is 1.55 to 1.80 volts per cell.
Deep Cycle Process
High discharged rate and high charging rates
causes high temperature.
_____ temperature breaks down the separator material (cellophane like material).
High
______ circuit will occur if cellophane breaks down
allowing current flow to increase, causing more heat
Short
More material break down, during thermal runaway causes
more current to flow.
