BATTERIES

 BATTERIES

WHAT IS A BATTERY-A battery is a combination of two or more cells in series, parallel or series-parallel combinations.

1. Primary Batteries (Non-rechargeable)
Also commonly known as dry batteries
Used for low to moderate power drain applications.
Shape is usually flat, button or cylindrical.
Voltage is produced due to chemical reaction where one of the electrodes gets consumed; usually the negative electrode.
They are normally not rechargeable but some (usually the alkaline type) can be recharged.

(a) Alkaline Type Battery
Widely used in household devices (e.g., AA, AAA batter). Known for long shelf life and steady energy output.

(b)Lithium Type Battery :Used in small electronics like watches, calculators, and medical devices. They provide high energy density and last longer.

(c)Zinc-Carbon Type Battery :Inexpensive and commonly used in low-drain devices like remote controls.

(d)Silver-Oxide Type Battery: Often used in small devices like hearing aids and watches due to its compact size and stable output.

2.Secondary Batteries (Rechargeable)

also commonly known as wet cells.

like dry cells they too have electrodes called anodes and cathodes and have a electrolyte.
used for starting, lighting, ignition.
in this type of cell, the electrodes and electrolyte are altered by chemical reaction when delivering a current and thus get “discharged”.
these types of cells can be “restored” to their original form by forcing a current through it in a direction “opposite” to the flow of discharge current.

(a) Lead-Acid Battery

Total Voltage = 12VDC
1) Each Cell Voltage is 2.0 V
2) Fully charged Cell Voltage is 2.2V
3) Fully Discharged Cell Voltage is 1.8V (More correctly 1.73V)
4) Specific Gravity of Fully Charged Cell is 1.280 (More correctly between 1.270-1.285)
5) Specific Gravity of Fully Discharged Cell is 1.120 (More correctly 1.100)
Rules require, that the normal charging facilities are to be such, that a completely discharged battery, can be recharged to 80% of it’s capacity in not more than 10 hours. This test is a requirement and has to be carried at least once a year.

Construction and Working of Lead-Acid Type Wet Cell :-

Lead-Acid Battery

The Positive Electrode (Anode) is made up of Lead Peroxide (PbO₂) and the Negative Electrode (Cathode) is made of Lead(Pb). The Electrolyte is made up of dilute Sulphur Acid (H₂SO₄) in the ratio of 1 part Concentrated H₂SO₄ and 3 parts of water (H₂O). 

DISCHARGING:-
When the Lead acid cell supply current to the load (discharges) a chemical reaction occurs, as a result of which lead sulphate (PbSO₄) is created on both the plates, and the electrolyte is converted into water; the sulfuric acid breaks into positive ions 2H+ and negative ions SO₄. At the Anode, the hydrogen ions react with the PbO₂ and make PbO (Lead Oxide)and water H₂O.  PbO start reacting with the H₂SO₄ and creates PbSO₄ (Lead Sulphate)and H₂O. At the Cathode SO₄- ions exchange electrons from Pb, creating radical SO₄ which further creates PbSO₄ reacting with the Pb.  

H₂SO₄  2H⁺ + SO₄^--

At Anode

PbO₂ + 2H⁺ PbO + H₂O  

PbO + H₂SO₄PbSO₄ + H₂O

  

At Cathode

 
Pb + SO4-- PbSO4 + 2e-

After the discharge process both the plates are converted into the same type of material. Also due to breaking down of H₂SO₄ into water, the SPGR reduces to about 1.110, due to which the battery cannot produce enough voltage to power up the electrical loads and therefore requires to be “RECHARGED”.

CHARGING:-

 

H₂SO₄  2H⁺  +  SO₄^--

At Anode

PbSO₄ + H₂O + SO₄^--   PbO₂   +  2H₂SO₄

At Cathode

PbSO₄ + 2H⁺   Pb   +  H₂SO₄

Charging is carried out such that current is forced to flow in the opposite direction of the discharge current and this reverses the process of chemical reaction, once again returning the electrodes to their original form and returning the diluted Sulphuric Acid to its normal SPGR.

 

(b) Lithium-Ion (Li-ion) Battery:-Common in portable electronics, electric vehicles, and ships due to their high energy density, lightweight, and long cycle life.

(c)Nickel-Cadmium (Ni-Cd) Battery:-Used in power tools and emergency lighting. They can endure many charge-discharge cycles but suffer from the "memory effect.

(d)Nickel-Metal Hydride (NiMH) Battery:- An improvement over Ni-Cd batteries, offering higher capacity and no memory effect. Used in some hybrid cars and portable electronics.

(e) Lithium Iron Phosphate (LiFePO4):-A subtype of lithium-ion batteries with improved safety and thermal stability. Used in electric vehicles and energy storage systems.

(f) Solid-State Battery:-Emerging technology promising safer, more energy-dense batteries than traditional liquid electrolyte types. Future applications include electric vehicles and portable electronics.

Some Important Question:-

Q1:-Why are alkaline batteries not generally used on board ship?

Ans:-since alkaline cell voltage is only 1.2v as compared to lead-acid type
     which is 2.0v, more cells will have to be used to make up the same voltage;
     e.g. a lead-acid battery would require 6 cells to make up a 12v battery,
     whereas 10 such cells of equivalent size of the alkaline type would be
     required to make up a 12v battery, thus space occupied would be more.

Q2:-Why are alkaline & lead-acid batteries not kept in same room?

Ans:- Alkaline batteries are not generally used on board ships for several reasons, mainly related to their limitations in terms of performance, reliability, and safety in the marine environment:

1. Limited Energy Capacity and Lifespan

• Alkaline batteries are typically non-rechargeable and have a limited energy capacity. This makes them impractical for applications on board ships, where power demand is often high and continuous, requiring more durable and long-lasting power sources like lead-acid or lithium-ion batteries which can be recharged multiple times.

2. Temperature Sensitivity

• Ships operate in varying temperature environments, from extreme cold to tropical heat. Alkaline batteries are sensitive to temperature fluctuations, particularly to extreme cold, which can significantly reduce their capacity and performance. Rechargeable battery types like lithium-ion and lead-acid have better temperature tolerance, making them more reliable in harsh marine conditions.

3. High Demand for Rechargeability

• Onboard ships, many systems and equipment rely on rechargeable power sources due to the need for continuous operation and minimal maintenance. Alkaline batteries are non-rechargeable, and replacing them frequently is neither cost-effective nor practical for ship operations, where long-lasting and rechargeable batteries like lead-acid, nickel-cadmium (Ni-Cd), or lithium-ion are preferred.

4. Waste and Environmental Concerns

• Ships are governed by strict environmental regulations (e.g., MARPOL) that mandate proper waste management. Alkaline batteries generate more waste because they are single-use, and their disposal in large quantities would add to the hazardous waste on board. Rechargeable batteries reduce waste and are more environmentally friendly for ship operations.

5. Power Requirements on Ships

• Alkaline batteries are generally used for low-power devices like remote controls or small electronics. On ships, most equipment such as emergency systems, communication devices, and machinery—requires more robust power sources that can provide higher currents and handle greater power loads. Lead-acid and lithium-ion batteries are better suited for these high-power demands.

6. Marine Safety Considerations

• The marine environment is inherently more hazardous due to factors like vibration, corrosion, and potential exposure to saltwater. Alkaline batteries are more susceptible to leakage and damage in such conditions. In contrast, marine-grade lead-acid and lithium-ion batteries are designed with safety features to withstand the tough conditions at sea.

7. Availability of Superior Battery Technologies

• Advanced battery technologies, such as lead-acid (used in emergency systems) and lithium-ion (used for navigation and communication equipment), offer superior energy storage, rechargeability, and durability. These technologies are specifically suited for marine applications, making alkaline batteries less relevant for ships.

alkaline batteries are generally avoided on ships due to their limited energy capacity, non-rechargeability, environmental waste concerns, and inability to meet the high power demands and safety requirements of marine applications.