Que_Ans.
[1] When working on Batteries, what precautions should be taken?
Ensure the space is well ventilated, do not smoke or use naked lights and also wear protective clothing such as apron, gloves and face shield.
[2] What are the different types of battery cell?
Two types of battery cell are the lead acid and the alkaline cell.
[3] What is the range of voltages of a lead acid cell?
The range of voltages of a lead acid battery cell is 2 volts.
[4] What is battery capacity rated as?
Battery capacity is rated in ampere hours (Ah).
[5] During charging which gas is given off?
During charging of a battery cell, the gas given off is hydrogen.
[6] Why must the two types of cell be kept separate?
The two types of cell must be kept separate because rapid electrolyte corrosion to metal work can take place and certain damage to batteries can occur.
[7] What does the value of the electrolyte specific gravity indicate in lead acid batteries?
The electrolyte’s SG in lead acid batteries indicates the charged state of the battery, i.e., SG of 1270 – 1285 when fully charged and 1100 when discharged.
[8] What arrangement is used in battery charging equipment?
The arrangement used in battery charging equipment is normally a transformer / rectifier unit to supply the required DC voltage to the cells.
[9] What is the maximum allowable temperature of the electrotype during charging?
The maximum allowable electrolyte temperature during charging is 45 degrees C.
[10] What is the only indication of a fully charged alkaline cell?
The only indication of a fully charged alkaline cell is when the voltage remains at a steady maximum of 1.6 – 1.8 volts.
[11] What will happen if the cell plates are exposed to air?
If the cell plates are exposed to air, the life of the battery will rapidly reduce
[12] What indicates the state of charge in case of (a) lead acid battery (b) ni-cd battery.
- A) The specific gravity of the cells reaching the maximum required value.
- B) Only the voltage remaining constant for a considerable period of time during charging (as Specific gravity remains constant always)
[13] Why the batteries are kept on ‘trickle charge’?
1) To make up for the loss due to local action
2) To prevent freezing of electrolytes in cold climates.
[14] How is the electrolyte for lead acid battery prepared?
The 3% solution (3% sulphuric acid and 97% distilled water) is prepared by pouring the acid into the water.
[15] What is the electrolyte in the ni-cd cell?
Pottassium hydroxide (21% solution)
[16] How do you measure the temperature of battery?
By the liquid filled thermometer (mercury filled thermometers are not used as an accidental breakage can cause severe sparking and explosions)
[17] What is the open circuit voltage of fully charged lead acid cell and ni-cd cell?
Lead acid cell = 2.0 volts; ni-cd cell it is 1.2 volt.
[18] What is the name of the instrument used for measuring specific gravity?
Hydrometer.
[19] If a 6V battery is connected in series with a 24v battery by connecting their negative terminal together, what would be the result?
Net voltage available will be 18V (18V on the positive of the 24 volts battery)
[20] How is the lead acid battery cell sustaining a short circuit is indicated?
The battery will become excessively heated while being charged.
[21] What will be the freezing point of electrolyte in a fully charged lead acid battery?
Lower than the in a discharged battery
BATTERY 30-60 words
[1] What are the Advantages and Disadvantages of Alkaline Batteries?
The Advantages of Alkaline Batteries are that they retain charge on open circuit and even if discharged, it can be left for long periods without adverse effect.
The Disadvantages are that they require a greater number of cells to produce a particular Voltage.
They are also more expensive than Lead Acid Batteries.
[2] What are the Disadvantages and Advantages of a Lead Acid Battery?
The Advantages of a Lead Acid Battery are; they require fewer cells to achieve particular voltage and are reasonably priced.
The Disadvantages are that they require regular attention to keep fully charged, always require a trickle charge and they discharge on open circuit.
[3] How is the weak or dead cell in a battery is detected?
By measuring and comparing the specific gravity of all the cells.
In what way the nickel -cadmium batteries are superior to lead-acid Batteries?
At high discharge rates, ni-cd batteries deliver more power and they can be rechalged in a shorter time.
[4] What is the effect of ambient temperature on performance of the Battery?
Increase in ambient temperature increases the local action. However, the capacity increases with temperature, after a certain temperature rise, the sulphation starts, and the battery efficiency decreases. Optimum temperature will be between 400c and 450c.
60-100 words
[1] What are Batteries used for On-Board Ships?
They are used for supplying essential power to: Radio Equipment, Telephone Exchange, Fire Detection, General Alarm Circuits, etc. These Systems are often supplied from two sets of batteries worked on a regular charge/discharge cycle.
They are also used as Emergency Supplies, i.e. for Emergency Generator Start-up and Emergency Lighting. Being used in this case in a “stand-by” role to give power when Main Supplies fail.
[2] How are the emergency Batteries maintained?
The connections to be checked for tightness. Casing surfaces should be kept clean. Terminals are protected with petroleum jelly or Vaseline. Specific gravity should be checkecl at reqular intervals and the batteries to be topped up with distilled water as required. Batteries are ro be kept on trickle charging after attaining its full charge. Load test to be carried out at specified Periodic intervals.
[3] Describe the circuit sketched, making special reference to how battery charge is maintained and how it operates upon loss of main power.
The circuit sketched shows a standby battery system which is used as a back up system in the event of total power failure, so that power is maintained to important sources such as alarm panels, communications etc.
In the event of power failure, a two-pole switch which is held on contacts 1 and 2 by an energized Coil in normal operating condition ie. From the mains supply will change over due to loss of Power onto contacts 3 and 4, now power is supplied from the back up batteries.
The battery change over switch is normally changed over weekly to ensure both sets of batteries Are fully charged. The batteries off load being charged, while the batteries those are not, are on Stand-by for loss of power.
[4] How do you ensure that Batteries are always in good working order?
Where Lead Acid Batteries are used, they require a constant trickle charge, but for both types of Battery a regular charge up is necessary.
Check state of Battery using a Hydrometer; Lead Acid – S G 1270®1285 Alkaline is 1190 but S G for Alkaline Batteries does not change much during charge or discharge.
Ensure cells are covered with electrolyte, if not, top up with distilled water.
Keep batteries dry and clean
Terminals should be smeared with Petroleum Jelly.
[5] Describe how a battery of alkaline cells may be tested for its usefulness after long storage and if found deficient, how it can be rendered fit for service.
A battery of alkaline cells may be tested for usefulness by measuring the voltage across the cells to give an indication of charge. If the voltage is low, but the electrolyte S.G is okay ( taken using a hydrometer ), the battery may be recharged. But if the S.G is found to have dropped to @ i.i60, the electrolyte solution should be replaced and then the battery recharged.
[6] State why one of the following battery types requires a trickle charge and the other does not;
Lead acid
Alkaline nickel cadmium
A lead acid battery requires a constant trickle charge as it tends to loose its charge, a trickle charge keeps it fully charged. An alkaline nickel cadmium battery usually only requires a full charge and is able to hold its charge. Also there is a danger of putting a lead acid battery on full charge as a lot of heat is produced and as a result of this the battery could be destroyed.
100-150 words
[1] With respect to an emergency standby lead acid battery;
State the safety features incorporated in the design and construction
State, with reasons, two causes of short circuit
State, with reasons, five causes of fall off in rated capacity
- a) Safety features that are incorporated in the design of lead acid battery construction are; caps that allow gas to vent off while on charge, cells that are separated, the outside casing of the battery is of a robust material, i.e. plastic.
- b) Two causes of short circuit are a buildup of sediment at the bottom of the cells and break down of cells usually due to the battery being over charged, causing the battery to overheat.
- c) Five reasons for fall off of rated charge are;
Low specific gravity of electrolyte due to not being charged for a period
Plates/ cells that are not covered with electrolyte
Internal short circuit due to build up of sediment at the bottom of the cells
Cold temperature causing S.G to drop off
Overcharge, causing overheating of the battery, causing breakdown
[2] With reference to shipboard batteries, state the difference between the following;
primary and secondary cell;
acid cell and alkaline cell
- a) The difference between primary and secondary cell batteries are that primary cells can only be used once, as where secondary cell batteries can be recharged.
- b) The difference between lead acid cell batteries and alkaline cell batteries are that acid cell batteries use sulphuric acid as an electrolyte, as where alkaline cell batteries use potassium hydroxide.
Also the voltage of an acid cell battery is greater than the voltage of an alkaline cell.
The cell of an acid battery consists of a lead peroxide positive plate and a lead negative plate. As where an alkaline cell consists of nickel hydroxide positive plate and a cadmium and iron negative plate.