AS113 - Lecture - Lead Acid Batteries Flashcards
A device of two or more cells that changes chemical energy into electrical energy.
Battery
There are two Categories of battery
PG. 3-53 & 10-90
Primary Cell
Secondary Cell
Compact, light weight.
The active elements in this battery become exhausted and cannot be restored.
Primary Cell or Dry Cell
There are three Types of Primary Cells
- Carbon-Zinc cell
- Alkaline cells
- Mercury Cells
Electrons flow from zinc to carbon rod.
Produces 1.5 vdc regardless of size.
Size of cell will determine current.
Ammonium chloride-electrolyte .
Carbon-Zinc cell
Longer life and less expensive.
Zinc rod, potassium hydroxide electrolyte solution.
Potassium hydroxide has a lower resistance than ammonium chloride of carbon-zinc cells.
Built differently.
Alkaline cells
Use for hearing aids, cameras, etc..
High capacity.
Mercuric oxide (positive).
Potassium hydroxide (negative)-electrolyte.
Mercury Cells
Takes electrical energy and stores it chemically.
When called upon it converts chemical energy into electrical energy.
Secondary Cells
Typical battery consists of 6 or 12 cells.
Each cell produces 2.1 volts.
6 cells- 12volt battery.
12 cells- 24 volt battery.
Lead acid battery
Battery most commonly used on aircraft
Lead acid battery
Grid of lead and antimony filled with lead peroxide.
Positive Plates
Similar grid but it is filled with Spongy lead.
One extra negative plate
Negative Plates
Plates do not go all the way to the bottom because.
This allows for sediment to collect
Separates plates and allows electrolyte (sulfuric acid and water) to keep in contact with the active material on plates.
Porous Separator
Battery Case is made of; (smaller aircraft)
Hard plastic (previously hard rubber)
Close cell openings
Have lead weights to prevent electrolyte from escaping at unusual flight attitudes.
Vented screw-in type Caps
Battery case for Large aircraft is made of?
Steel case (larger aircraft)-for shielding and mechanical protection.
Electrons flow from negative to positive plates.
Positive Ions form on negative plates
which attracts negative sulfate ions from the sulfuric acid.
Discharge
This reaction causes lead sulfate to form on both the positive and negative plates.
As the sulfate ions are attracted by the plates the electrolyte becomes diluted.
Water then forms.
At this discharged state the battery is more susceptible to freezing.
Discharge
Electrons drawn from positive plates and force on negative plates.
Electrons drive lead sulfate back into the electrolyte.
This makes the electrolyte sulfuric acid again.
Hydrogen gas is created and released.
Charge
“Condition of Charge”
Open circuit voltage (OCV)
2.1 vdc per cell
OCV does not reflect the state of battery charge.
1.275-1.300 fully charged
@ 80 degrees F
1.150 battery discharged
Specific Gravity
Below ______________________,
there is not enough chemical
strength in the electrolyte to
convert the active material into
lead sulfate.
1.150 specific gravity
uses a calibrated float
more dense the liquid higher the specific gravity
more buoyant the hydrometer more dense the liquid
Hydrometer
Electrolyte is ____ dense at ______ temperatures, and more dense at lower temperatures.
less
higher
Active material converts into lead sulfate which increases the battery’s internal resistance when a.
A load is placed on the battery
The ability to produce a given amount of current for a specified time.
Capacity
______ is measured in ampere-hours
Capacity
Capacity is affected by four things
- Amount of active material.
- The plate area.
- Quantity of electrolyte.
- Temperature:
Cold temperature decreases _______.
Capacity
50 F fully charged battery may provide power for ____ hours.
0 F same battery supplies power for _____ hour.
5hr
1hr
Standard rating used to specify the capacity of a battery.
Five Hour Discharge:
5 amps for 5hours capacity = ____ampere-hours
25
Capacity will ______ when discharged at a higher rate.
decrease
This is due to heat, sulfation of plates and the tendency of the electrolyte to become diluted immediately around the plates.
Capacity decreasing when discharged at a higher rate.
Cell Test:
With load on the battery test cells.
All cells should be within ___ volts of each other.
.05
Cell Test:
Verify electrolyte level is ___.
Apply a heavy load for ___ sec. by cranking engine w/starter and ign. off.
Turn on taxi lights or landing lights, enough to draw ___ amps.
While load current is ________, measure voltage at each cell.
3
10
flowing
A good battery will not go below _____ and all cells should be within _____ of each other.
1.95v
.05v
In a discharge condition.
If any cell is higher than 1.95v with more than .05v difference between any cell, then a cell is _______.
defective
How to service and charge a battery
Keep terminals clean, connections tight with no corrosion.
Clean corrosion with brush and baking soda.
Coat terminals – Use manufacturer’s recommended grease.
Insure correct level of electrolyte.
Add only distilled or de-mineralized water.
Do not get the baking soda in battery.
It will neutralize the electrolyte.
How do you dilute acid
Pour acid into the water
Never pour water into acid
Pouring water into acid will cause a severe ______ reaction with acid
exothermic
If acid gets into your eyes, flush with _______.
water
Never mix automotive and aircraft _______
electrolyte
NEVER _____ THE TERMINALS OF A BATTERY.
SHORT
_________ SHOULD BE USED WHEN TRANSPORTING BATTERIES.
CARRYING STRAPS
PROTECTIVE CLOTHING, SUCH AS;
SHOULD BE WORN WHEN WORKING WITH BATTERIES.
RUBBER APRON
RUBBER GLOVES
FACE SHIELD
__________, ELECTRIC SPARKS, OR OPEN FLAMES SHOULD BE PERMITTED NEAR CHARGING BATTERIES.
NO SMOKING
CARE SHOULD BE TAKEN TO PREVENT __________ OF THE ELECTROLYTE
SPILLING
A mixture of hydrogen and air can be dangerously _______. No smoking, electric sparks, or open flames should be permitted near charging batteries.
Explosive
Charging source must be ____ than open circuit voltage (OCV)
greater
Batteries are charged by either ________ or _________
Constant Current or Constant Voltage Charging
Most effective
Always follow MFG’s recommendations
Multiple batteries - connect in series when charging
Constant Current Charging:
Aircraft charges batteries by constant voltage.
Shop chargers boost or jump battery- not airworthy.
Constant Voltage Charging:
(8083) Passing direct current through the battery in a direction opposite to that of the discharge current _____ charge a storage battery. Because the internal resistance (IR) in the battery, the voltage of the external charging source must be ______ than the open circuit voltage.
may
greater
When Installing the Battery
_______ terminal gets connected first.
_______ terminal last (this “arms” the battery).
Positive
Negative
When removing the Battery:
_______ terminal must be disconnected first (this “disarms” the battery).
_______ terminal last.
Negative
Positive
Keep wrenches, screwdrivers, jewelry, etc. from making unwanted contact with the terminals! True/Flase
True
Parallel-Series Battery Connections:
Connecting batteries in parallel increases ______ (capacity), but not ______.
amps
voltage
Connecting batteries in series increases _______, but not _______.
voltage
capacity
Vents-vent fumes from inside the battery box.
Battery Box
Sump jar-contains _________ ______ moistened with sodium bicarbonate and water.
absorbent pads
A ______ is a device that transforms chemical energy into electrical energy.
CELL
The cell has three parts;
the electrodes, the electrolyte, and the container.
There are two basic cells:
primary and secondary
________are the current conductors of the cell.
ELECTRODES
_______is the solution that acts upon the electrodes.
THE ELECTROLYTE
_________holds the electrolyte and provides a means of mounting the electrodes.
THE CONTAINER
is a cell in which the chemical action finally destroys one of the electrodes, usually the negative. The primary cell cannot be recharged.
THE PRIMARY CELL
_______is a cell in which the chemical action alters the electrodes and electrolyte.
THE SECONDARY CELL
The electrodes and electrolyte can be restored to their original condition by ________ the cell.
recharging
_______ is the process of converting chemical energy into electrical energy.
ELECTROCHEMICAL ACTION
________ is the positive electrode of a cell.
THE ANODE
