AES Flashcards
What are Primary batteries in aviation?
Primary - Are capable of producing current as soon as they are constructed and are unable to be recharged.
What are Secondary batteries in aviation?
Secondary batteries are rechargeable and are used for starting engines or auxiliary power units
(APU), powering aircraft systems before starting, allowing technicians to test systems on the
ground and as an emergency source of power in the air.
Where would you use a primary battery in aviation?
In aviation they are used
cockpit voice recorders (CVR), flight data recorders (FDR), emergence locator transmitters (ELT)
and life vest lights
How must secondary batteries be constructed in aviation
They must be able to
cope with large temperature variations, atmospheric pressure variations and cope well with
inversion, vibration and impact
The two most common secondary aircraft battery types?
- Lead acid
- Nickel Cadmium (NiCad)
What are the methods to keep batteries held in position during flight?
Typically, hold down points are manufactured into the lid of the
case that are used to secure the battery to battery tray or the airframe.
No hold down points available: Positioned using brackets
In general aviation batteries can have posts located on top that accept bolts. What must be done to prevent damage when torquing the battery
These bolts must be torqued to the manufacturer’s specifications to prevent damage
What can be combined to make electrolyte in lead acid batteries?
Electrolyte used in lead acid batteries is sulphuric acid combined with
distilled water.
With regards to Lead Acid Batteries, what is the nominal voltage of each cell?
What is the nominal voltage of a battery in aviation, which are typically comprised of 12 cells.
Each cell in a lead acid battery has a nominal voltage of 2V DC.
Aviation batteries are typically comprised of 12 cells joined in series giving a total nominal voltage of 24V DC
What is the reccomended voltage do Lead acid batteries need to be charged at?
When charging lead acid batteries out of an aircraft, constant potential charging is usually the best method of restoring a lead acid batteries charge. A voltage of
approximately 2.4V DC per cell is the recommended voltage. With a 12-cellbattery, this equates to 28.8V DC at the output of our battery charger
What is the limiting voltage?
Once the cells have dropped to 1.75V DC per cell, this is considered to be the limiting voltage.
What is the C1 Rating?
Aviation batteries have a 1-hour rating referred to as the C1 rating. This is the average current that a battery is capable of supplying without interruption for an
interval of 1 hour.
Thus, if a battery can deliver 20 amperes continuously for 1 hour, the battery has a rating of 20 Ah.
The 20Ah battery mentioned above supplied 20A for 1 hours (C1
rating) before the battery discharged to a voltage of 21V (12 cells x 1.75V DC each).
The average current the battery is capable of supplying without interruption for an
interval of 1 hour.
Lead acid batteries are made up of what components?
- Battery case
- Connectors
- Cells
What is the typical range of Cold Cranking Amps (CCA) Ratings of aircraft secondary batteries?
Typical CCA ratings can range from 300A for general aviation up to 1000A for turbine-based
aircraft.
300A-1000A
Aircraft battery cells consist of which 3 main components?
Cells in a lead acid battery are made up of what components?
- Plates (positve plate have lead dioxide paste added to the grive and negative plates have a pasteof sponge lead added to the grid)
-
Separator Seperators are placed between the positve plate (anode) and the negative plate (cathode)
Alternating layers of plates and separators are used to form a cell
- Electrolyte
Electrolyte used in lead acid batteries is sulphuric acid combined with
distilled water
What makes Nickel Cadmium Different to Lead Acid Batteries?
Nickel cadium case can be opened and indiviual cells can replaced with new cells
The capacity of a battery is measure in what?
Ampere-hour (Ah)
How many cells are found in a NiCad battery?
What is the nominal voltage of each cell?
A typical NiCad battery has 20 individual cells fitted into the case. Each cell is a nominal 1.2 V DC
How are the cells in a NiCad battery joined together?
Each cell is joined to another in series giving the battery the required voltage.
Nickel plated copper solid links are used for the interconnections
- Nickle plated copper used to interlink the cells
- Linked in series
In a Nickel Cadium Battery what range do the vent caps, vent at?
Most vented NiCad’s vent
at between two and ten PSI.
What connector is used for a NiCad battery
A Elcon style connector
What is a major danger regarding NiCad batteries?/
Define thermal runaway?
A Ni-Cad battery is able to operate over a wider temperature range than
a lead-acid battery. However, they need to be watched very closely in
high temperatures and high charging rates as they become unstable. This
can cause thermal runaway which is an uncontrolled increase in battery
temperature potentially leading to a discharge of toxic fumes and the risk of
ignition and fire
- Uncontrollable increase in the temperature of a battery
- Leads to discharge or toxic fumes or ignition
High temp / high changing rate = battery becomes unstable
How are the State of Charge and State of Health Calculations done?
The temperature of the cells is an important factor for
determining the battery’s SOC and SOH calculations,
Using the temperature
Label the component
Cockpit Control Panel