Aircraft Batteries

Question 1

what is a battery

Answer 1

device that converts chemical energy to electrical energy

Question 2

typical voltages for dry, lead-acid, nickel-cadmium cells

Answer 2

dry cell: 1.5 VDC
lead-acid cell: 2.1 VDC
nickel-cadmium cell: 1.2 VDC

Question 3

hierarchy of on-board power

Answer 3

battery + inverter
RAT Gen
APU
Generator

Question 4

lead-acid batteries specific gravity when fully discharged

Answer 4

1.18

Question 5

electrolytes used in lead-acid & nickel cadmium batteries

Answer 5

lead-acid: H2SO4

nickel-cadmium: KOH

Question 6

types of battery tests and checks

Answer 6

high-rate discharge test
capacity check
cell leakage test
insulation test
hydrometer test

Question 7

what does a hydrometer test do and determines?

Answer 7

measures the specific gravity of liquid wrt density of water

determines the specific gravity of electrolyte

Question 8

temperature inverse or directly proportional to specific gravity

Answer 8

inversely proportional

Question 9

battery vicious cycle

Answer 9

increased heat > reduced resistance > increased current > increased heat

Question 10

how to remove & install battery

Answer 10

remove negative lead first, install black lead last

BIL (black in last)

Question 11

lead acid vs nickel cadmium batteries

Answer 11

lead acid:
higher terminal voltage
lighter, smaller, cheaper

nickel cadmium batteries:
higher life expectancy
can withstand overcharging
higher working temperature

Question 12

2 battery charging methods

Answer 12

constant current, constant voltage

Question 13

difference between constant current and constant voltage charging

Answer 13

constant current is in series, constant voltage is in parallel

constant current: longer time to charge and dangers of overcharging
constant voltage: less time and supervision but leads to cell imbalance

Question 14

lead acid battery VDC when fully charged & discharged

Answer 14

fully charged: 2.2V

fully discharged: 1.8V

Question 15

connecting batteries in parallel/series will increase which factor?

Answer 15

parallel - increase Ah capacity, more amps

series - increase total voltage

Question 16

photocell vs fuel cell

Answer 16

photocell converts light into electricity

fuel cell converts potential energy from a fuel into electricity

Question 17

specific gravity of fully charged lead-acid battery

Answer 17

1.275 - 1.3

Question 18

factors determining span of useful life of battery

Answer 18

construction and design
conditions under which it operates
servicing it receives

Question 18

types of servicing on batteries

Answer 18

initial servicing

routine servicing

quarterly servicing

Question 19

what causes thermal runaway and what will it cause

Answer 19

thermal runaway happens when temperature conditions and charging rates exceeds a certain value

causes:
violent gassing
boiling of electrolytes
melting of plates and casing