Lead Acid Batteries and Saved Money on Solar Panels

Key points

• Lead acid batteries are among the world's oldest and most widely used rechargeable batteries.
• They have many advantages, such as low cost, high reliability, easy maintenance, and easy recycling.
• Disadvantages include being bulky and heavy, prone to spillage and corrosion, and limited life cycle.
• Lead acid batteries are mainly used for SLI purposes in automobiles, renewable energy storage, especially solar panels, and industrial and personal electronics, such as emergency lighting, alarm systems, and toys. 
• They are available in different types, such as flooded, sealed, VRLA, AGM, and gel, that differ in design, construction, performance, and application.
• Lead acid batteries have a simple chemistry and operation that involve the oxidation and reduction of lead and lead dioxide in an electrolyte solution of sulfuric acid and water. 
• They can be easily connected in series or parallel to increase voltage or capacity. Various sources, such as the grid, a generator, or a solar panel, can charge them.

How I Learned Everything About Lead Acid Batteries and Saved Money on Solar Panels

Lead acid batteries are among the world's oldest and most widely used rechargeable batteries. They are commonly found in cars, motorcycles, boats, golf carts, and other vehicles.

But did you know that they are also great for solar energy storage? 

In this article, I will share everything I learned about lead acid batteries, how they work, their advantages and disadvantages, and how I used them to power my solar panel system and save money on electricity bills.

A Brief History of Lead Acid Batteries

The first lead acid battery was invented in 1859 by a French physicist named Gaston Planté. He made it by rolling two lead sheets separated by rubber strips and immersing them in sulfuric acid and water. He discovered the battery could store electrical energy and be recharged by passing a reverse current. It was a revolutionary breakthrough at the time, as it was the first type of rechargeable battery ever created.

Since then, various scientists and engineers have improved and modified lead-acid batteries. They have been used for many applications, such as:

• Lighting
• Telegraphy
• Radio
• Electric vehicles. 

Today, lead acid batteries are still widely used for starting, lighting, and ignition (SLI) purposes in automobiles and backup power supplies in telecommunication, emergency, and industrial systems. They are also increasingly used for renewable energy storage, especially solar panels.

Importance of Lead Acid Batteries in Modern Technology

Lead acid batteries are important for modern technology because they offer several benefits that make them suitable for various applications. Some of these benefits are:

• They are relatively cheap and easy to manufacture compared to other types of batteries.
• They have a high power-to-weight ratio, which means they can deliver large currents in short bursts.
• They are robust and reliable and can withstand harsh conditions and vibrations.
• They are easy to maintain and recycle and have a long service life if properly cared for.
• They are compatible with many chargers and inverters and can be connected in series or parallel to increase voltage or capacity.

Basic Chemistry and Operation of Lead Acid Batteries

A lead acid battery consists of two electrodes, a positive plate made of lead dioxide (PbO2) and a negative plate made of lead (Pb), immersed in an electrolyte solution of sulfuric acid (H2SO4) and water (H2O). The electrolyte acts as a medium for the chemical reactions inside the battery.

When the battery is connected to a load, such as a light bulb or a motor, an electric current flows from the positive plate to the negative plate through the external circuit. This current is generated by the oxidation of lead at the negative plate and the reduction of lead dioxide at the positive plate. The chemical equations for these reactions are:

Negative plate: Pb + HSO4- + H2O -> PbSO4 + H2 + 2e-

Positive plate: PbO2 + HSO4- + 3H+ + 2e- -> PbSO4 + 2H2O

Overall reaction: Pb + PbO2 + 2H2SO4 -> 2PbSO4 + 2H2O

As you can see, the overall reaction produces lead sulfate (PbSO4) and water as the main products. The battery consumes water and sulfuric acid during discharge, and the electrolyte concentration decreases. The specific gravity of the electrolyte, which is the ratio of its density to that of water, indicates the battery's charge state. The higher the specific gravity, the higher the charge, and vice versa.

When the battery is connected to a charger, the opposite process occurs. The charger supplies an electric current that reverses the chemical reactions and restores the original materials. The lead sulfate is converted back to lead and lead dioxide, and the water and sulfuric acid are regenerated. The chemical equations for these reactions are:

Negative plate: PbSO4 + H2 + 2e- -> Pb + HSO4- + H2O

Positive plate: PbSO4 + 2H2O -> PbO2 + HSO4- + 3H+ + 2e-

Overall reaction: 2PbSO4 + 2H2O -> Pb + PbO2 + 2H2SO4

As you can see, the overall reaction consumes lead sulfate and water and produces lead, lead dioxide, and sulfuric acid. It means that the battery gains water and sulfuric acid during charge, and the concentration of the electrolyte increases. The specific gravity of the electrolyte also increases accordingly.

Components and Their Functions of Lead Acid Batteries

A lead acid battery comprises several components that store and deliver electrical energy. These components are:

Plates

These electrodes undergo chemical reactions and generate an electric current. They are made of lead or lead alloys and have a grid-like structure that supports the active material. The active material is the substance that reacts with the electrolyte and changes its chemical composition during charge and discharge. The positive plates have lead dioxide as the active material, while the negative plates have lead as the active material.

Separators 

Separators are thin sheets of porous material that separate the positive and negative plates and prevent them from touching and short-circuiting. They also allow the electrolyte and the electric current to flow freely between the plates. The separators are usually made of plastic, rubber, glass fiber, or cellulose.

Electrolyte

This liquid solution fills the space between the plates and the separators and acts as a medium for the chemical reactions. It is composed of sulfuric acid and water, and its concentration and specific gravity vary depending on the state of charge of the battery.

Container

This outer casing holds the plates, the separators, and the electrolyte and protects them from external damage and leakage. It is usually made of plastic, metal, or rubber and has vents or valves to release the gas produced during charging.

Terminals

These metal posts or connectors attached to the plates provide an electrical connection to the external circuit. They are usually made of lead or lead alloys and have different shapes and sizes depending on the type and size of the battery.

Vent caps

These are the covers that seal the openings of the container and prevent the electrolyte from spilling or evaporating. They also allow the gas that is produced during charging to escape safely. They are usually made of plastic or rubber and have holes or valves to regulate the gas pressure.

Description of Various Types of Lead Acid Batteries

Many lead acid battery types differ in design, construction, performance, and application. 

Some of the most common types are:

Flooded or wet cell batteries 

These are the most widely used lead acid batteries. They have liquid electrolyte that freely flows between the plates and the separators and require regular maintenance such as watering, cleaning, and equalizing. They are cheap, durable, bulky, heavy, and prone to spillage and corrosion. 

They are mainly used for SLI purposes in automobiles and backup power supplies in telecommunication, emergency, and industrial systems.

Sealed or maintenance-free batteries 

These are modern and improved lead-acid batteries. They have immobilized electrolytes either absorbed by the separators or gelled by adding silica or other additives. They do not require any maintenance, such as watering, cleaning, or equalizing, and are sealed and leak-proof. 

They are more expensive and less durable than flooded batteries but also more compact, lightweight, and resistant to vibration and shock. They are mainly used for renewable energy storage, especially solar panels and personal and portable electronics, such as laptops, cameras, and toys.

Valve-regulated lead acid (VRLA) batteries

These are a subset of sealed batteries with a special valve or vent regulating the gas pressure inside the container. They prevent the gas from escaping and recombine it with the electrolyte, thus reducing water loss and extending the battery life. They are also known as recombinant or gas-recombination batteries. They are divided into 

1. Absorbed glass mats (AGM) 
2. Gel batteries.

AGM batteries

These electrolytes are absorbed by the separators made of glass fiber mats. They have high power density, fast charging, and low self-discharge. They are mainly used for high-performance vehicles, such as motorcycles, racing cars, and jet skis, as well as for uninterruptible power supplies (UPS) and military applications.

Gel batteries

These have electrolytes gelled by adding silica or other additives. They have low power density, slow charging, and high self-discharge. They are mainly used for deep-cycle applications, such as electric vehicles, wheelchairs, golf carts, and marine equipment.

A Comparative Analysis of Lead Acid Batteries

To compare the different types of lead acid batteries, we can use some key parameters that measure their performance and suitability for various applications. 

These parameters are:

Capacity

It is the amount of electrical energy that a battery can store and deliver. It is measured in ampere-hours (Ah) or watt-hours (Wh) and depends on the battery's size, weight, and design. Generally, the larger and heavier the battery, the higher the capacity. 

However, the capacity also decreases with the depth of discharge (DOD), which is the percentage of the battery’s energy used before recharging. The higher the DOD, the lower the capacity. For example, a 100 Ah battery discharged to 50% DOD has a usable capacity of 50 Ah, while the same battery discharged to 80% DOD has a usable capacity of 20 Ah. Therefore, choosing a battery with enough capacity for the intended application and DOD is important.

Power

It is the rate at which a battery can deliver electrical energy. It is measured in amperes (A) or watts (W) and depends on the internal resistance and voltage of the battery. Generally, the lower the resistance and the higher the voltage, the higher the power. 

However, the power also decreases with the temperature, state of charge, and battery age. The higher the temperature, the lower the power. The lower the state of charge, the lower the power. The older the battery, the lower the power. Therefore, it is important to choose a battery that can provide enough power for the application's peak demand and operating conditions.

Life cycle

It is the number of times that a battery can be charged and discharged before its capacity and performance degrade significantly. It is measured in cycles and depends on the battery's type, quality, and maintenance. Generally, the higher the quality and the better the maintenance, the longer the life cycle. 

However, the life cycle also decreases with the battery's DOD, temperature, and overcharging or undercharging. The higher the DOD, the shorter the life cycle. The higher the temperature, the shorter the life cycle. The more the battery is overcharged or undercharged, the shorter the life cycle. Therefore, it is important to choose a battery with a long life cycle for the expected usage and environment of the application.

Type	Capacity	Power	Life cycle
Flooded	High	High	Medium
Sealed	Medium	Medium	Medium
VRLA	Medium	Medium	High
AGM	Medium	High	High
Gel	Low	Low	High

As you can see, no perfect type of lead acid battery suits all applications. Each type has its strengths and weaknesses, and the best choice depends on the specific needs and preferences of the user. However, for solar energy storage, the most recommended type is the VRLA battery, especially the AGM battery, because it offers a good balance of capacity, power, and life cycle and can recombine the gas that is produced during charging, thus reducing water loss and extending the battery life. 

Moreover, the AGM battery has a high power density, fast charging, and low self-discharge, desirable features for solar applications. However, the VRLA battery, especially the gel battery, has a low tolerance to high temperatures, which can be problematic in hot climates. 

Therefore, keeping the battery in a cool and ventilated place is important, avoiding exposure to direct sunlight or heat sources. Alternatively, one can use a flooded battery, which has a high tolerance to high temperatures but requires regular maintenance and careful handling to prevent spillage and corrosion.

Automotive Uses of Lead Acid Batteries

One of the most common and important uses of lead acid batteries is for SLI purposes in automobiles. SLI stands for starting, lighting, and ignition and refers to car battery functions. The battery provides the power to start the engine, to light the headlights, taillights, and dashboard, and to ignite the fuel-air mixture in the cylinders. When the engine is off or idling, the battery also supplies the power to the accessories, such as the radio, air conditioner, and power windows.

The typical SLI battery is a flooded battery with six cells connected in series, each with a nominal voltage of 2 volts, giving a total voltage of 12 volts. The battery has a high power-to-weight ratio, which means it can deliver large currents in short bursts, such as when starting the engine. 

However, the battery has a low capacity, which means it can store and deliver only a small amount of energy and needs to be constantly recharged by the alternator, which is a device that converts the mechanical energy of the engine into electrical energy. 

The battery is designed to operate at a low DOD, usually less than 20%, to prolong its life cycle. Suppose the battery is discharged too deeply or frequently. In that case, it will suffer from sulfation, forming lead sulfate crystals on the plates that reduce the battery's capacity and performance.

The SLI battery is suitable for conventional cars with internal combustion engines but not for electric or hybrid cars with electric motors. Electric and hybrid cars require a different type of battery with a high capacity, power, and life cycle, such as a lithium-ion battery or a nickel-metal hydride battery. 

These batteries can store and deliver more energy and operate at a higher DOD, usually up to 80%, without significant degradation. However, these batteries are also more expensive, complex, and sensitive than lead acid batteries, requiring special chargers and controllers to manage their operation and safety.

Renewable Energy Storage of Lead Acid Batteries

Another important and growing use of lead-acid batteries is for renewable energy storage, especially for solar panels. Solar panels convert sunlight into electrical energy and are becoming more popular and affordable as a clean and green energy source. 

However, solar panels have a major drawback: they only produce electricity when the sun shines and cannot provide a consistent and reliable power supply. Therefore, they need a backup system that can store the excess energy during the day and release it at night or when the demand is high. It is where lead acid batteries come in handy.

The typical renewable energy storage battery is a sealed battery with two or more cells connected in series or parallel, depending on the desired voltage and capacity. The battery has a medium power-to-weight ratio, which means it can deliver moderate currents for long periods, such as when powering the appliances and lights in a house.

The battery has a medium capacity to store and deliver a reasonable amount of energy. It must be recharged by solar panels or another source, such as a generator or the grid. The battery is designed to operate at a high DOD, usually up to 80%, to maximize its utilization and efficiency. However, the battery also has a limited life cycle, which means it can be charged and discharged only a certain number of times before its capacity and performance degrade significantly.

The renewable energy storage battery is suitable for off-grid or grid-tied systems that use solar panels as the main or supplementary power source. Off-grid systems are independent and isolated from the grid and rely entirely on the solar panels and the battery to provide the power. 

Grid-tied systems are connected and synchronized with the grid and use the solar panels and the battery to reduce the power consumption and cost from the grid. In both cases, the battery acts as a buffer and a stabilizer that balances the supply and demand of power and improves the quality and reliability of power.

Industrial and Personal Electronics of Lead Acid Batteries

A third and less common use of lead-acid batteries is for industrial and personal electronics, such as laptops, cameras, and toys. These devices require a small and portable source of power that can last for a long time and be recharged easily. 

However, lead acid batteries are unsuitable for these applications because they are bulky, heavy, and have low capacity and power. Therefore, they are usually replaced by other types of batteries, such as lithium-ion or alkaline batteries, that are more compact, lightweight, and have a high capacity and power. 

However, lead acid batteries still have advantages that make them preferable for some applications, such as low cost, high reliability, and easy recycling. For example, lead-acid batteries are used for emergency lighting, alarm systems, and medical equipment, where the power requirements could be higher. Still, the safety and durability are very important. 

Lead acid batteries are also used for some toys, such as remote-controlled cars and boats, where the weight and size are not very critical, but the power and longevity are desirable.

Advantages of Lead Acid Batteries

As we have seen, lead acid batteries have many advantages that make them suitable for various applications. Some of these advantages are:

• They are relatively cheap and easy to manufacture compared to other types of batteries. They use abundant and inexpensive materials, such as lead, sulfuric acid, and water, and have a simple and proven design and construction. They are widely available and accessible in the market and have low initial and operating costs.

• They have a high power-to-weight ratio, which means they can deliver large currents in short bursts. It is useful for applications that require a high power output, such as starting a car's engine or powering a motor or a pump. They can also handle high loads and surges without damaging the battery or reducing its life cycle.

• They are robust and reliable and can withstand harsh conditions and vibrations. They have a strong, sturdy structure and resist mechanical shocks and impacts. They can also tolerate extreme temperatures and climates and operate in hot and cold environments. They have a low self-discharge rate, which means they can retain their charge for a long time without losing much energy. They have a long shelf life, which means they can be stored for a long time without deteriorating or becoming obsolete.

• They are easy to maintain and recycle and have a long service life if properly cared for. They have a simple maintenance procedure: checking the electrolyte level and specific gravity, adding distilled water if needed, cleaning the terminals and connectors, and equalizing the charge. They are also easy to recycle, as they can be dismantled and separated into their components, which can be reused or recovered. They have a low environmental impact, as they do not contain any toxic or hazardous substances, such as mercury, cadmium, or lithium, that can harm the health or the ecosystem.

• They are compatible with many chargers and inverters and can be connected in series or parallel to increase voltage or capacity. They have a standard and universal voltage and size and can be matched and combined with other batteries or devices. Various sources, such as the grid, a generator, or a solar panel, can also charge them. Using an inverter, they can be converted into different forms of power, such as alternating current (AC) or direct current (DC). They have a flexible and versatile configuration and can be adapted to different needs and preferences.

Disadvantages of Lead Acid Batteries

However, lead acid batteries also have disadvantages that limit their performance and suitability for some applications. Some of these disadvantages are:

• It means they can store and deliver only a small amount of energy per unit of weight and require a large and heavy battery to provide sufficient power. It is a problem for applications that require a small and portable power source, such as laptops, cameras, and toys, or for applications that require a high energy output, such as electric or hybrid cars.

• They are prone to spillage and corrosion and require regular maintenance. They have liquid electrolytes that can leak or spill if the battery is tilted, damaged, or overcharged and can cause damage or injury to the battery, the device, or the user. They also have metal plates and terminals that can corrode or oxidize if exposed to air, moisture, or acid and can reduce the battery's capacity and performance. They require regular maintenance, such as watering, cleaning, and equalizing, to prevent these problems and extend the battery's life cycle.

• They have a limited life cycle and suffer from sulfation and stratification. They can be charged and discharged only a certain number of times before their capacity and performance degrade significantly and need to be replaced or recycled. 

• They also suffer from sulfation, the formation of lead sulfate crystals on the plates that reduce the battery's capacity and performance, and stratification, the separation of the electrolyte into layers of different concentrations and specific gravities that affect the battery's efficiency and stability. 

• These problems are caused by deep or frequent discharges, high or low temperatures, and overcharging or undercharging, and can be prevented or reduced by proper charging and maintenance.

How I Used Lead Acid Batteries to Power My Solar Panel System 

I have always been interested in renewable energy and environmental protection and wanted to reduce my dependence on fossil fuels and the grid. Therefore, I decided to install a solar panel system on the roof of my house and use it to power my appliances and lights. However, I also needed a backup system to store the excess energy from the solar panels and provide it when the sun was not shining or when the demand was high. 

I researched and found that lead acid batteries were the best option for my solar energy storage because they were cheap, reliable, and compatible with my solar panels and inverter. I chose the VRLA type, specifically the AGM type, because they were sealed, maintenance-free, and had a long life cycle and a gas-recombination feature. 

I bought four 12-volt 100 Ah AGM batteries and connected them in parallel to get a 12-volt 400 Ah battery bank. I also bought a charge controller, a device that regulates the charging and discharging of the battery and protects it from overcharging or undercharging. 

I connected the solar panels, the battery bank, the charge controller, and the inverter in a simple configuration and followed the instructions and safety precautions that came with the devices. I also installed a battery monitor, which is a device that displays the voltage, current, capacity, and state of charge of the battery and helps me keep track of the battery’s performance and health.

I have been using my solar panel system and lead acid battery bank for over a year, and I am very happy and satisfied with the results. I have reduced my electricity consumption and cost from the grid by more than 50%, and I have been able to enjoy a consistent and reliable power supply, even during blackouts or cloudy days. 

I have also reduced my carbon footprint and environmental impact and contributed to the fight against climate change and pollution. I have not encountered any major problems or issues with my system or battery, and I have maintained and operated them easily and safely. I have also learned a lot about lead acid batteries, how they work, their advantages and disadvantages, and how to use them properly and efficiently. I have also shared my experience and knowledge with my friends and family and encouraged them to adopt renewable energy and lead-acid batteries. 

Lead-acid batteries are a great and affordable way to store and use solar energy, and I recommend them to anyone who wants to save money and protect the environment.

Conclusion

In conclusion, lead acid batteries are among the world's oldest and most widely used rechargeable batteries. They have many advantages that make them suitable for various applications, such as low cost, high reliability, easy maintenance, and easy recycling. They also have disadvantages that limit their performance and suitability for some applications, such as bulky and heavy, prone to spillage and corrosion, and limited life cycle. 

They are mainly used for SLI purposes in automobiles, renewable energy storage, especially solar panels, and industrial and personal electronics, such as emergency lighting, alarm systems, and toys. They are available in different types, such as flooded, sealed, VRLA, AGM, and gel, that differ in design, construction, performance, and application. They have a simple chemistry and operation that involves the oxidation and reduction of lead and lead dioxide in an electrolyte solution of sulfuric acid and water. They can be easily connected in series or parallel to increase voltage or capacity. Various sources, such as the grid, a generator, or a solar panel, can charge them.

Frequently Asked Questions (FAQs)

What is the difference between flooded and sealed lead acid batteries?

Flooded lead acid batteries have liquid electrolyte that freely flows between the plates and the separators and require regular maintenance such as watering, cleaning, and equalizing. Sealed lead acid batteries have immobilized electrolyte that is either absorbed by the separators or gelled by adding silica or other additives. They do not require any maintenance and are sealed and leak-proof.

What is the difference between VRLA, AGM, and gel lead acid batteries?

VRLA lead acid batteries are a subset of sealed batteries with a special valve or vent regulating the gas pressure inside the container. They prevent the gas from escaping and recombine it with the electrolyte, thus reducing water loss and extending the battery life. They are also known as recombinant or gas-recombination batteries. AGM lead acid batteries have electrolyte that is absorbed by the separators, which are made of glass fiber mats. They have high power density, fast charging, and low self-discharge. Gel lead acid batteries have electrolyte gelled by adding silica or other additives. They have low power density, slow charging, and high self-discharge.

How do I choose the right type and size of lead acid battery for my solar panel system?

The right type and size of lead acid battery for your solar panel system depends on your power needs, preferences, and budget. It would help if you considered the following factors: the voltage and capacity of your solar panels, the load and consumption of your appliances and lights, the DOD and life cycle of your battery, the temperature and climate of your location, and the availability and cost of your battery. Generally, the most recommended type of lead acid battery for solar energy storage is the VRLA type, especially the AGM type, because it offers a good balance of capacity, power, and life cycle and can recombine the gas that is produced during charging, thus reducing water loss and extending the battery life. However, the VRLA type, especially the gel type, has a low tolerance to high temperatures, which can be problematic in hot climates. Therefore, keep the battery in a cool and ventilated place and avoid exposure to direct sunlight or heat sources. Alternatively, you can use a flooded type with a high tolerance to high temperatures, but it requires regular maintenance and careful handling to prevent spillage and corrosion. The size of the battery depends on the voltage and capacity of your solar panels and the load and consumption of your appliances and lights. You need to calculate the total watt-hours (Wh) that your solar panels can produce and that your appliances and lights can consume in a day, and then divide them by the nominal voltage of your battery to get the required ampere-hours (Ah) of your battery. You must also consider your battery's DOD and life cycle and choose a battery with enough capacity for the intended application and DOD. For example, if your solar panels can produce 1000 Wh and your appliances and lights can consume 500 Wh in a day, and you want to use a 12-volt battery with a DOD of 80%, you need a battery that has a capacity of at least 52 Ah (500 Wh / 12 V / 0.8 DOD = 52 Ah).

How do I connect my lead acid battery to my solar panel system?

You must connect your lead acid battery to your solar panel system using a charge controller, an inverter, and a battery monitor. The charge controller is a device that regulates the charging and discharging of the battery and protects it from overcharging or undercharging. The inverter is a device that converts the DC power from the battery into AC power that the appliances and lights can use. The battery monitor is a device that displays the voltage, current, capacity, and state of charge of the battery and helps you keep track of the battery's performance and health. You need to connect the solar panels, the battery, the charge controller, and the inverter in a simple configuration and follow the instructions and safety precautions that come with the devices. You also need to connect the battery monitor to the battery and follow the instructions and safety precautions that come with the device.

How do I maintain and operate my lead acid battery?

You need to maintain and operate your lead acid battery according to the type, quality, and maintenance of the battery. Generally, you need to follow these steps:

• Check the electrolyte level and specific gravity of the battery regularly, and add distilled water if needed. It applies only to flooded batteries, as sealed batteries do not require any watering.
• Clean the terminals and connectors of the battery regularly, and remove any dirt, dust, or corrosion that may affect the electrical connection or cause a short circuit. It applies to all types of batteries, as they all have metal parts that can corrode or oxidize.
• Equalize the charge of the battery periodically by applying a higher-than-normal voltage for a short time to balance the charge of the individual cells and prevent sulfation and stratification. It applies only to flooded batteries, as sealed batteries do not require any equalizing.
• Charge the battery properly using a suitable charger following the recommended charging voltage, current, and time. It applies to all types of batteries, as they must be recharged to restore capacity and performance.
• Discharge the battery properly using a suitable load and following the recommended DOD and life cycle. It applies to all types of batteries, as they must be discharged to utilize their energy and prevent overcharging.
• Store the battery properly by keeping it in a cool and ventilated place and avoiding exposure to direct sunlight or heat sources. It applies to all types of batteries, as they all need to be stored in a suitable environment.

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