Lead Acid Batteries: a Complete Guide

Read more in this guide about the fascinating technology of lead acid batteries, their various systems, and their uses.

A lead acid battery is a type of rechargeable battery that runs on lead and sulfuric acid. In order to facilitate a controlled chemical reaction, the lead is submerged in sulfuric acid. The battery generates electricity as a result of this chemical reaction. In order to recharge the battery, this reaction is then reversed.

Please continue reading for more information if lead acid batteries are of interest to you.

What Are Lead Acid Batteries?

The most popular battery type in photovoltaic systems is the lead acid battery. In contrast to other battery types, lead acid batteries have a long lifespan and low cost despite having a low energy density, only moderate efficiency, and high maintenance requirements.

Lead acid batteries have the distinct advantage of being the most widely used type of battery for the majority of rechargeable battery applications (such as starting automobile engines), which has resulted in a well-established, mature technology base.

Advantages and Disadvantages of Lead-acid Batteries

The long service life of lead-acid batteries is well known. For instance, a lead-acid battery used as a storage battery can last between 5 and 15 years, depending on its quality and usage. They are typically affordable to buy. They also don’t require a lot of maintenance and are incredibly reliable and durable. These features contribute to the lead-acid battery’s excellent price-performance ratio.

However, lead batteries have a flaw in that they are sensitive to deep discharge, which could make a battery useless. Therefore, it should always be charged to at least 20 percent. Deep discharge protection is now available on some models.

Lead batteries are typically distinguished by a high power density because less gas is produced while they are charging, necessitating the need for well-ventilated spaces to house them in order to prevent explosions. They can deliver high currents. This is especially helpful for industrial applications or vehicle starter batteries. Read Can Lead-acid Batteries Explode?

Their low energy density is one of their disadvantages. They consequently weigh a lot for their volume. Because of this, they are less than ideal for electric vehicles that need to store a lot of energy. However, the high weight can also be advantageously used, such as a counterweight for machinery that must move heavy loads.

Characteristics of Lead Acid Batteries

The battery lifetime, depth of discharge, and maintenance requirements are generally considered to be the three most crucial battery properties for renewable energy systems. The following section describes this set of parameters and how they relate to charging schedules, temperature, and age.

Depth of Discharge and Battery Capacity

As the amount of energy that can be extracted from the battery is determined by multiplying the battery capacity by the depth of discharge, the depth of discharge together with the battery capacity is a fundamental parameter in the design of a battery bank for a PV system. Batteries can either be classified as deep-cycle batteries or shallow-cycle batteries.

A deep-cycle battery will have a depth of discharge that is greater than 50% and may even reach 80%. A shallow-cycle battery bank needs more capacity than a deep-cycle battery bank does in order to have the same usable capacity.

Battery Lifetime

Battery capacity decreases over time as a result of sulfation and material shedding. The degradation of battery capacity depends most strongly on the interrelationship between the following parameters:

• The charging/discharging regime that the battery has experienced
• The DOD of the battery over its life
• Its exposure to prolonged periods of low discharge
• The average temperature of the battery over its lifetime

Maintenance Requirements

Lead acid batteries require regular water replacement due to the production and escape of hydrogen and oxygen gas from the battery, which causes water loss. Water loss can be a big issue because other parts of a battery system don’t need maintenance as frequently. Checking for water loss can be expensive if the system is in a remote area.

By limiting the amount of gas that escapes the battery, maintenance-free batteries reduce the need for routine maintenance. However, all batteries to some extent add an extra maintenance component to a PV system because of the corrosive nature of the electrolyte.

Battery Efficiency

The typical coulombic and energy efficiencies of lead acid batteries are 85% and 70%, respectively.

Materials Used for Lead Acid Battery

The primary active materials required to construct a lead acid battery are:

• The dark brown, hard, and brittle substance called lead peroxide (PbO2) is used to create the positive plate.
• Pure lead in soft sponge conditions produces the negative plate in sponge lead (Pb).
• H2SO4 in solution: A potent acid that functions well as an electrolyte. It is highly ionized, and the hydration of the hydrogen ions causes the majority of the heat released during dilution. With a water-to-acid ratio of 3:1, it is utilized for lead-acid batteries.

How Does a Lead Acid Battery Work?

The lead peroxide plate and sponge lead plate are submerged in diluted sulfuric acid to create the lead acid storage battery. Between these plates, there is an external electrical connection. The molecules of sulfuric acid split into positive hydrogen ions (H+) and negative sulfate ions (SO4 − −) in dilute sulfuric acid.

The hydrogen ions receive electrons from the PbO2 plate as it approaches, becoming hydrogen atoms that attack PbO2 once more to produce PbO and H2O (water). As a result of the reaction between this PbO and H2 SO4, PbSO4, and water are produced. Read more information about How Do Lead-acid Batteries Work?

The SO4 ions (anions) move in the direction of the electrode (anode) attached to the positive terminal of the DC source, where they will surrender their extra electrons and transform into radical SO4. Due to its inability to exist on its own, the radical SO4 reacts with the PbSO4 in the anode to produce lead peroxide (PbO2) and sulfuric acid (H2SO4).

Lead Acid Battery Charging

Lead discharge batteries contain sulphuric acid, which must be replaced because it degrades over time. The structure of the plates can occasionally change entirely on its own. Battery replacement or charging is necessary when it starts to lose efficiency.

Lead sulfate build-up may become very challenging to remove when car batteries are left in their discharged states for protracted periods of time. For this reason, lead-acid batteries need to be charged as soon as possible (to stop lead sulfate from accumulating). Most frequently, an external current source is used to charge lead-acid batteries.

When a plug connected to the lead-acid battery is inserted, the chemical reaction moves in the other direction. The charging procedure might become ineffective if the sulphuric acid in the battery (or another battery component) has undergone decomposition. Therefore, it is wise to periodically check the battery.

Potential Problems With Lead Acid Batteries

The electrodes in a lead acid battery are made of lead oxide, and the lead is submerged in a weak sulfuric acid solution. Potential problems encountered in lead-acid batteries include:

1. Gassing: Gases oxygen and hydrogen evolve. Safety issues and water loss from the electrolyte result from the battery gassing. The water loss increases the maintenance requirements of the battery since the water must periodically be checked and replaced.
2. Destruction of the electrodes Because it is soft and prone to damage, the lead at the negative electrode is used in applications where the battery may move continuously or erratically.
3. Stratification of the electrolyte. A heavy, viscous liquid, sulfuric acid is. The concentration of sulfuric acid in the electrolyte decreases during battery discharge and increases during charging. The electrolyte may stratify as a result of this cycling of sulfuric acid concentration, with the less concentrated solution, water, remaining close to the top and the heavier sulfuric acid remaining at the bottom of the battery. The close proximity of the electrode plates within the battery means that physical shaking does not mix sulfuric acid and water.
4. Battery sulfurization On the lead electrode, rather than the fine-grained material that is typically produced on the electrodes, large lead sulfate crystals may grow at low states of charge. The insulating material is lead sulfate.
5. Acidic waste being spilled. A significant safety risk exists if sulfuric acid leaks from the battery housing. Gelling or immobilizing the liquid sulfuric acid reduces the possibility of sulfuric acid spills.
6. Low discharge levels can cause the battery to freeze. The electrolyte’s freezing point will also decrease if the battery is discharged to a low level after the entire electrolyte has been turned into water.
7. loss of electrodes’ active materials Several processes could result in the electrodes’ active material being lost. The active material flaking off as a result of volumetric changes between xxx and lead sulfate is one process that can result in a permanent loss of capacity. Gassing and improper charging conditions can result in the permanent loss of capacity by shedding active material from the electrodes.

Different Lead-acid Battery Systems

There are several types of lead batteries available today, including pure lead batteries, lead-gel batteries, and lead-fleece batteries. The substance used as the electrolyte is primarily responsible for the variations. For instance, they can be observed in the performance, intensity, and possibility of storage.

Lead-fleece Batteries

Acid serves as the electrolyte in lead-fleece batteries; it is bound in a micro-glass fleece. It is frequently referred to as an AGM battery because another name for this is Absorbent Glass Mat (AGM). This battery is leak-proof and requires no maintenance because of the glass fiber fleece. Therefore, it can also be used continuously in a lateral position.

Lead-fleece batteries are a type of valve-regulated lead-acid battery. They typically have a longer lifespan than flooded batteries and provide better performance and speed. With them, the volume of hydrogen and oxygen that can escape during charging can be controlled.

As a result, these batteries are frequently used in situations where a significant amount of energy needs to be kept stored for an extended period of time, such as in the emergency power supply. A battery must adhere to the highest quality standards if it is used for an alarm system, emergency power supply, emergency lighting, or fire alarm system.

Due to its many positive properties, the lead-fleece battery is now used in a variety of ways and has different properties:

• Alarm systems and UPSs both utilize standby lead-fleece batteries. They have a relatively long standby duration despite being designed for a few charging processes.
• Lead-fleece batteries, in particular, can be discharged and recharged frequently. Like with conventional lead batteries, the charging process is also quicker. They are utilized in wheelchairs, marine applications, recreational vehicles, medical e-scooters, and more.
• Lead-fleece high-current batteries are created especially for uses that call for high discharge currents in a brief period of time. For instance, they can be applied to robotics, motorcycles, and vehicles.

Lead-gel Batteries

Liquid sulfuric acid, which is bound with silica, serves as the electrolyte in lead-gel batteries. This type also features a valve that stops the electrolyte from leaking and is completely sealed. As a result, they can be set up in a lateral position and are easier to transport. Additionally, they require almost no upkeep. See Sealed Lead Acid Battery and Valve Regulated Lead Acid (VRLA) Battery.

The sealed design of the batteries allows them to be used in close proximity to people and in enclosed spaces without any gas escaping. Additionally, they can be utilized in areas with stricter environmental protection laws, such as on watercraft.

The fields of application are similar to those of the lead-fleece accumulator. In electric cars, mobile homes, boats, and stairlifts, accumulators for cyclic operation are frequently used. For warning and emergency power systems, as well as telephone and solar systems, accumulators made for continuous operation are appropriate.

There is only one thing to keep in mind: Lead-gel batteries are less suited for delivering high currents because their internal resistance is higher than, say, open lead batteries.

Here is what we have compared:

• Gel Battery Vs Lead Acid Battery: Which is Better?
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• Lithium Vs Alkaline Batteries: Which is Better for You?

Pure Lead Batteries

For extremely demanding industrial applications, pure lead batteries are designed specifically. Their design is closed as well. In comparison to lead-acid batteries with conventional electrode materials, high-purity lead is used for the electrode. A substitute material for the plates is a lead-tin compound. This lowers the internal pressure within the battery, enabling rechargeable batteries to achieve high power density.

Conclusion: Understanding Lead Acid Batteries

Nearly 170 years after the first lead-acid battery was created, the technology is now well-established in a wide range of application fields. The advantages of long service life, power density, and resistance make accumulators essential for the industry.

Lead acid batteries have the distinct advantage of being the most widely used type of battery for the majority of rechargeable battery applications (such as starting automobile engines), which has resulted in a well-established, mature technology base.

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