Here is the construction, operation, care, and maintenance of lead-acid and nickel
cadmium batteries:
Lead-Acid Batteries
Construction:
Consists of positive plates made of lead dioxide (PbO2) and negative
plates made of sponge lead (Pb).
These plates are immersed in an electrolyte, which is a solution of
sulfuric acid (H2SO4) and water.
The plates are separated by insulators to prevent short circuits.
The battery is housed in a durable plastic case.
Operation:
Discharging: During discharge, a chemical reaction occurs where lead
dioxide and sponge lead react with sulfuric acid, forming lead sulphate
(PbSO4) on both plates. This process releases electrons, providing
electrical current.
Charging: During charging, an external electrical source reverses the
chemical reaction, converting lead sulphate back to lead dioxide and
sponge lead, and restoring the sulfuric acid concentration in the
electrolyte.
Care and Maintenance:
Electrolyte Level: Regularly check the electrolyte level and add
distilled water as needed. Low electrolyte can damage the plates.
Clean Terminals: Keep terminals clean and free from corrosion. Use
a wire brush and apply a thin layer of petroleum jelly or battery terminal
protector.
Charge Regularly: Avoid deep discharges, as they can shorten
battery life. Regularly charge the battery to maintain its capacity.
Avoid Extreme Temperatures: Extreme temperatures can affect
battery performance and lifespan.
Proper Ventilation: Ensure adequate ventilation when charging to
prevent the build-up of explosive hydrogen gas.
Specific Gravity: The specific gravity of the electrolyte can be
measured to determine the state of charge.
Testing: Regularly test the battery's voltage and capacity to identify
potential problems.
Nickel-Cadmium (Ni-Cd) Batteries
Construction:
Consists of positive plates made of nickel hydroxide (Ni(OH)2) and
negative plates made of cadmium (Cd).
The electrolyte is a solution of potassium hydroxide (KOH).
The plates are separated by insulators.
The battery is sealed in a metal case.
Operation:
Discharging: During discharge, a chemical reaction occurs where
nickel hydroxide and cadmium react with potassium hydroxide,
releasing electrons.
Charging: During charging, an external electrical source reverses the
chemical reaction, restoring the original chemical composition of the
plates.
Care and Maintenance:
Avoid Deep Discharges (Memory Effect): Ni-Cd batteries can
develop a "memory effect" if repeatedly discharged to the same level.
This reduces their capacity. Avoid partial discharges when possible.
When needed, fully discharge, and then recharge the battery.
Charge Regularly: Regular charging is essential to maintain battery
health.
Avoid Overcharging: Overcharging can damage the battery. Use a
charger designed for Ni-Cd batteries.
Proper Ventilation: Ensure adequate ventilation when charging to
prevent the build-up of gasses.
Storage: Store Ni-Cd batteries in a cool, dry place.
Dispose of Properly: Ni-Cd batteries contain cadmium, which is a
toxic heavy metal. Dispose of them according to local regulations.
Safety Precautions for Battery Charging, Storage, and
Acids
Battery Charging:
o Ventilation:
Batteries release hydrogen gas during charging, which is highly
explosive. Charge batteries in a well-ventilated area to prevent
gas build-up.
Avoid enclosed spaces like closets or small rooms.
o Proper Connections:
Ensure the charger is properly connected to the battery
terminals, observing correct polarity (+ to + and - to -).
Incorrect connections can cause sparks, explosions, or damage
to the battery or charger.
o Charger Settings:
Use a charger with appropriate voltage and current settings for
the battery type (lead-acid, Ni-Cd, etc.).
Overcharging can overheat and damage the battery.
o No Smoking or Open Flames:
Keep sparks, flames, and smoking materials away from
batteries during charging.
o Disconnecting:
Turn off the charger before disconnecting the battery.
Disconnect the negative terminal first, then the positive terminal.
Battery Storage:
o Cool, Dry Place:
Store batteries in a cool, dry place to prevent corrosion and self
discharge.
o Upright Position:
Store lead-acid batteries in an upright position to prevent
electrolyte leakage.
o Separate Storage:
Store different battery types separately to avoid chemical
reactions.
Store away from flammable materials.
o Regular Checks:
Periodically check stored batteries for voltage and electrolyte
levels (if applicable).
o Neutralization:
Keep a neutralising agent, such as baking soda, nearby in case
of acid spills.
Acids (Electrolyte):
o Protective Gear:
Wear appropriate PPE, including safety glasses, gloves, and an
apron, when handling battery acid.
o Avoid Contact:
Prevent acid from contacting skin, eyes, or clothing.
o Eye Wash and First Aid:
Have an eye wash station and first aid kit readily available.
o Dilution:
Always add acid to water, never water to acid, to prevent
splashing and heat generation.
o Neutralization:
Use baking soda to neutralize acid spills.
o Proper Disposal:
Dispose of used acid and contaminated materials according to
local regulations.
o Labelling:
Clearly label all containers holding acid.
o Storage:
Store acids in acid resistant containers, in a cool dry location,
away from incompatible materials.
General Precautions:
o Read Manuals:
Always read and follow the manufacturer's instructions for
battery charging, storage, and handling.
o Children and Pets:
Keep batteries and acids out of reach of children and pets.
o Emergency Procedures:
Be familiar with emergency procedures for acid spills or battery
explosions.
o Training:
Ensure anyone working with batteries or acids has proper
training.
Battery-related terms:
Ampere-Hour Capacity (Ah)
Ampere-hour capacity is a measure of a battery's ability to deliver a specific
amount of current over a period of time. It indicates how much electrical
charge a battery can store.
Explanation: A battery with a higher Ah rating can supply more current for a
longer duration than a battery with a lower Ah rating. For example, a 100Ah
battery can theoretically deliver 100 amperes for one hour, or 50 amperes for
two hours, and so on. However, the actual capacity can vary depending on
factors like temperature, discharge rate, and battery age.
Formula (General Concept): Ah = Current (A) × Time (h)
Reserve Capacity (RC)
Reserve capacity is the amount of time (in minutes) a fully charged battery
can deliver 25 amperes at 80°F (26.7°C) before its voltage drops below 10.5
volts.
Explanation: This rating is particularly important for automotive batteries. It
indicates how long a vehicle can operate on battery power alone if the
charging system fails. It essentially provides a "backup" time for essential
electrical systems.
Formula: There isn't a simple calculation formula. Reserve capacity is
determined through standardized testing.
Cold Cranking Amps (CCA)
Cold cranking amps is a measure of a battery's ability to deliver a high current
at low temperatures. It's the number of amperes a battery can deliver at 0°F (
-17.8°C) for 30 seconds while maintaining a voltage of 7.2 volts or higher.
Explanation: This rating is crucial for starting a vehicle in cold weather. Cold
temperatures reduce battery performance, and a high CCA rating ensures the
battery can provide enough power to crank the engine.
Formula: Similar to reserve capacity, CCA is determined through
standardized testing rather than a direct calculation.
Battery testing instruments and charging methods.
Battery Testing Instruments
Hydrometer
Construction: A hydrometer consists of a glass tube with a weighted
bulb at the bottom and a graduated scale inside.
Operating Principle: It measures the specific gravity of the battery's
electrolyte. Specific gravity is the ratio of the density of the electrolyte
to the density of water. The specific gravity of the electrolyte is directly
related to the state of charge of a lead-acid battery.
Operation:
Insert the hydrometer's nozzle into the battery's cell.
Draw electrolyte into the tube until the float rises freely.
Read the specific gravity on the graduated scale at the liquid
level.
Compare the reading to the manufacturer's specifications to
determine the battery's state of charge.
Interpretation: A higher specific gravity indicates a higher state of
charge.
High-Rate Discharge Tester
Construction: A high-rate discharge tester consists of a heavy-duty
resistor, an ammeter, and a voltmeter.
Operating Principle: It applies a high current load to the battery for a
short period, simulating the load of starting an engine. The voltmeter
measures the battery's voltage under load.
Operation:
Connect the tester's leads to the battery terminals, observing
correct polarity.
Apply the load for a specified time (e.g., 15 seconds).
Observe the voltmeter reading during the test.
Compare the voltage reading to the manufacturer's
specifications to determine the battery's condition.
Interpretation: A significant voltage drop indicates a weak or failing
battery.
Cadmium Tester
Construction: A cadmium tester consists of a voltmeter and a
cadmium electrode.
Operating Principle: It measures the voltage between the cadmium
electrode and the positive and negative plates of a nickel-cadmium (Ni
Cd) battery. This allows for the individual checking of the positive and
negative plates.
Operation:
Carefully expose the electrolyte of the Ni-Cd battery.
Insert the cadmium electrode and the voltmeter probes into the
electrolyte, making contact with the appropriate plates.
Read the voltage measurements.
Compare the readings to the manufacturer's specifications to
determine the condition of the individual plates.
Interpretation: A reading outside the specified range indicates a faulty
plate.
Battery Charging Methods
Constant Current Charging:
Principle: The charger delivers a constant current to the battery,
regardless of the battery's voltage.
Procedure:
Connect the charger to the battery, observing correct polarity.
Set the charger to the desired current level.
Monitor the battery's voltage and temperature during charging.
Terminate charging when the battery reaches the desired
voltage or when the charging current drops to a low level.
Application: Suitable for charging Ni-Cd batteries and some lead-acid
batteries.
Constant Voltage Charging:
Principle: The charger maintains a constant voltage across the battery
terminals, allowing the charging current to decrease as the battery
charges.
Procedure:
Connect the charger to the battery, observing correct polarity.
Set the charger to the desired voltage level.
Monitor the charging current, which will decrease as the battery
charges.
Terminate charging when the charging current reaches a low
level.
Application: Commonly used for charging lead-acid batteries.
Trickle Charging:
Principle: A low-current, constant voltage charge used to maintain a
battery's state of charge during long periods of inactivity.
Procedure:
Connect the trickle charger to the battery, observing correct
polarity.
Allow the charger to maintain a low current flow to the battery.
Monitor the battery periodically.
Application: Used to prevent self-discharge of stored batteries.
Pulse Charging:
Principle: The charger delivers short pulses of high current to the
battery, followed by periods of rest.
Procedure:
Connect the pulse charger to the battery, observing correct
polarity.
Allow the charger to cycle through its pulse and rest periods.
Monitor the battery's voltage and temperature.
Application: Can help to reduce sulfation in lead-acid batteries.
Equalization Charging:
Principle: A controlled overcharge used to balance the charge
between the cells of a lead-acid battery.
Procedure:
Connect the charger to the battery, observing correct polarity.
Apply a higher-than-normal voltage for a specific period.
Monitor the battery's voltage and temperature.
Application: Used periodically to maintain the health of lead-acid
batteries in standby power applications.
