Lead Acid Batteries

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Ampere Hours is?

(A/H) rating states the theoretical current the battery can supply in one hour

the electrolyte of a battery is what percentage of water and acid?

70% water and 30% acid

What is meant by "Cell Imbalance"?

A healthy battery should maintain approximately equal voltages across all its cells during discharge, and when fully recharged. Faulty batteries often develop problems in one or more cells that have a much lower terminal voltage than the rest.

what is the storage of a battery

Charge every 4 to 6 weeks. Charge and capacity check before returning to service. Capacity test new batteries every 6 months. Capacity test used batteries every 3 months. Insulation check every 12 months. Store batteries for no more than 18 months. Do not store in a discharged condition. Do not allow temperature to exceed 48°C. Record all maintenance.

How should exposed battery terminals be treated to prevent corrosion?

Coat exposed battery terminals with petroleum jelly or general purpose grease to exclude moisture, prevent corrosion and the formation of deposits on the terminals.

what four factors affect the capacity?

Plate area Amount of active material Quantity of electrolyte Temperature

leaving a battery permanently low discharged rate can what?

damage it

How should multiple batteries be charged using constant current charging?

multiple batteries are connected in series and the maximum supplied current is the capacity of the lowest battery

what is the charge of a cell when fully charge, but generally rated at

2.2V but usually rated at 2V

What is a typical constant voltage level used to charge a 24V battery?

28 volts

What SG readings indicate low charged lead acid battery state?

1.24 to 1.2

What SG readings indicate medium charged lead acid battery state?

1.275 to 1.24

What SG readings indicate high charged lead acid battery state?

1.3 to 1.275

what rate does the battery internal resistance increase?

Doubles

When should hydrometer readings be taken if water is to be added?

Hydrometer readings should be taken before adding water as it takes time for the additional water to mix thoroughly with the electrolyte allowing an accurate reading to be taken.

What capability does a battery require if used as an emergency power source?

Once airborne batteries often comprise the aircraft's emergency power supply and must be capable of operating emergency systems for thirty minutes. For these reasons aircraft batteries must be monitored for condition and replaced or serviced when required.

What can affect SG readings?

The two factors are temperature a impurities

what is the purpose of the vent cap?

allows gases to escape and you can check the electrolyte levels

what is a hydrometer?

an instrument that measures the relative density of a battery electrolyte compared to pure water. calibrated in SG

How does constant voltage charging current vary as the battery charges?

as the voltage of battery increase the current supplied drops off slowly

when charging several batteries together what can you do?

batteries of the same voltage can be charged together in parallel using the constant voltage method

how to calculate the internal resistance of a battery if? A battery containing 12 cells connected in series and charged to 2.1 V per cell delivers 6A of current into 4 Ohms resistance. Calculate the internal resistance of the battery.

calculate the terminal voltage 12 x 2.1V = 25.2V, use ohm's law to calculate the V = 6Ax4ohms = 24, voltage drop 25.2V - 24V = 1.2V, and internal resistance is 1.2V ÷ 6A = 0.2 Ohms

Why is moisture between the terminals undesirable?

can cause a current to flow and will discharge the battery of a period of time

what affect could be cause by moisture and / or dirt deposits between a lead acid Battery terminals?

could cause slow discharge of the battery

Why should lead acid batteries be kept in a high state of charge?

due to the heavy loading they are under, starting of engines requires a high charge state

how is the life of battery determined?

for example a 40 A/H battery should provide 20 Amps for 2 hours or 10 Amps for 4 hours.

When does a Lead Acid battery release the most gas?

gassing mostly occurs towards the end of the charging state

blue marks on a battery terminal hardware indicate?

high resistance is present due to loose hardware

How should multiple batteries be charged using constant voltage charging?

in parallel

What is excessive water consumption an indication of?

indication of overcharging, possibly a deflective cell or internal short

What causes slow loss of fluid from the electrolyte?

is caused by evaporation and decomposition during charging

terminal voltage is?

is determined by the number of cells in series

what is the standard rating used to specify the capacity of the battery?

is five hours

what does cold temperature to the battery current draw?

is reduces the chemical reactions

what is cold cranking amps?

is the maximum starting current a battery can provide

what main problem caused by sulphation in lead acid batteries is?

isolating the active material from the electrolyte

can multiple batteries be charged using the constant current method?

only if connected in series and limited to the lowest maximum charge current of any of the batteries being charged

what are the plates constructed of?

positive is lead peroxide and negative plate uses spongy lead

the main purpose of cell separators is to?

prevent the plates from touching

What type of water should be used when servicing batteries?

pure distilled water

Which temperatures require a correction of SG readings?

readings for temperature are not required between temperatures of 20 and 32°C(70 and 90° F). Outside of this range a correction chart must be referred to.

How high should the electrolyte level in the battery be?

should be same level just above the plates

what do you neutralize acid spills with?

sodium bicarbonate solution and rinse with water

what increases the internal resistance of a battery due to as it discharge?

sulphate forms on the outside of the plates. Not only is the amount of active material reduced, but the remaining surface area available for the electrolyte to react with is also reduced by the blocking effect of the sulphate.

what happens to the SG as the battery charges

the SG rises

What happens to the electrolyte during charging?

the acid content and density of the electrolyte increase

What advantage does a fully charged lead acid battery have in freezing conditions?

the electrolyte is less susceptible to freezing due to the increased density

How should acid and water be mixed when preparing fresh electrolyte?

the electrolyte should be mixed for cells that are dry, the acid should be added to the water and not the other way around, because will will float to the top and cause a violent reaction at the boundry

what determines the voltage of a battery?

the number of cells

What is the outer casing made of and why is there a space at the bottom?

the outer casing is made of hard rubber or high impact plastic. the sump in the bottom collects any sediment chamber that permits accumulation of lost plate material to prevent shorten of the plates

what is specific gravity?

the ratio of the weight of a substance to the weight of the same volume of pure water

what can determine the current delivery

the surface area of the plates as more chemical reactions can occur

what determines the capacity of a battery?

the thickness of the plates

how are the plates arranged?

they are arranged so that they are interleaved, with each positive plate sandwiched between two negative plates, the plates of each polarity are connected in parallel, and collectively connected to a terminal post plates of each polarity

What is the purpose of the separators?

they keep the plates apart while allowing electrolyte to contact the plates, channels are included to allow sediment to drop

what is the main reason why inter-cell hardware should be kept clean and properly torqued?

to prevent high resistance joints and heating

How should a battery's damaged painted surfaces be repaired?

touched up with acid resistance paint

when charging a battery typically you charge above the battery rated voltage true of false?

true

What effect does over-charging or heavy discharge have on a lead acid battery?

will result in excessive sulphation, heats the plates up and can cause shedding of the active material and also internal discharge

What test for cell imbalance can be performed on a battery installed in an aircraft?

• Crank the starter for three seconds • Turn on loads of about ten amps • Measure voltage of each cell good cells indicate 1.95 volts each and not more than .05volts difference


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