All About Lead-acid Batteries

As one of the oldest and most widely used types of rechargeable batteries, lead-acid batteries can provide high power output and low cost. In this blog post, we will explore the basics of lead-acid batteries, their different types, and their applications.

What are Lead-Acid Batteries?

A lead-acid battery is a type of battery that uses lead and an acid electrolyte as major components. The lead-acid batteries are the first type of rechargeable battery created.

Chemistry of Lead-acid Battery

The basic structure of a lead-acid battery consists of two lead plates, called electrodes, immersed in a dilute solution of sulfuric acid, called electrolyte. The lead plate connected to the positive terminal is called the positive electrode, and the lead plate connected to the negative terminal is called the negative electrode. The electrodes are separated by a porous material, called a separator, that prevents them from touching each other and causing a short circuit.

How Does a Lead-acid battery work?

When connecting lead-acid batteries to an external load, such as a motor or a light bulb, a chemical reaction occurs between the electrodes and the electrolyte. The positive electrode reacts with the sulfuric acid and releases electrons, while the negative electrode reacts with the sulfuric acid and accepts electrons. The electrons flow from the positive electrode to the negative electrode through the external circuit, creating an electric current. The electric current can power the load and perform useful work.

The chemical reaction also changes the composition of the electrodes and the electrolyte. The positive electrode is converted from lead to lead dioxide, and the negative electrode is converted from lead to lead sulfate. The sulfuric acid is consumed and diluted by water. As a result, the battery loses its ability to produce electric current and becomes discharged.

The lead-acid battery can be recharged by applying an external voltage source, such as a charger or a generator, that is higher than the battery voltage. The external voltage source reverses the direction of the electric current and the chemical reaction. The positive electrode is converted back to lead, and the negative electrode is converted back to lead dioxide. The sulfuric acid is regenerated and concentrated by water. As a result, the battery regains its ability to produce electric current and becomes charged.

Types of Lead-acid Batteries

There are three main types of lead-acid batteries, based on their construction and electrolyte. They are flooded lead-acid batteries, sealed lead-acid batteries, and valve-regulated lead-acid batteries.

Flooded lead-acid(FLA) batteries

Flooded lead-acid batteries are the most common and traditional type of lead-acid batteries. FLA batteries have an open vented design, which means that the electrolyte is in liquid form and can spill or leak if the battery is tilted or damaged. The electrolyte also evaporates and produces hydrogen and oxygen gases, which need to be vented to prevent pressure build-up and explosion. Flooded lead-acid battery requires regular maintenance, such as adding distilled water to replenish the electrolyte and equalizing the charge to prevent sulfation.

Sealed lead-acid(SLA) batteries

Sealed lead-acid batteries are a modified version of flooded lead-acid batteries. They have a closed design, which means that the electrolyte is immobilized and cannot spill or leak. The electrolyte can be in the form of a GEL or an absorbed glass mat (AGM), which are both porous materials that hold the acid. This type lead-acid battery also has a valve that allows the gases to escape when the pressure is too high, but prevents the air from entering the battery. The battery does not require maintenance, such as adding water or equalizing the charge.

Sealed lead-acid batteries are mainly used for deep cycle applications, such as in backup power, solar power, and electric vehicles. SVC AGM Lead-acid Battery

Valve-regulated lead-acid(VRLA) batteries

Valve-regulated lead-acid batteries are a special type of sealed lead-acid batteries. They have a valve-regulated design, which means that the gases produced inside the battery are recombined into water, instead of being vented out. The battery has a pressure relief valve that opens only when the pressure is too high, and closes when the pressure is normal. The battery does not lose water or electrolyte, and does not need maintenance.

VRLA batteries are mainly used for high-performance applications, such as in telecommunications, medical equipment, and military equipment.

AGM Battery vs Gel Battery: What Differences?

Both AGM batteries and GEL batteries are the types of SLA battery and VRLA battery. All have a closed design that prevents the electrolyte from spilling or leaking and a valve that regulates the pressure inside the battery.

The differences between GEL and AGM lead acid battery are

  • AGM batteries use a glass mat to absorb the electrolyte, while GEL batteries use a gel-like substance to immobilize the electrolyte.
  • AGM batteries have a higher power output and a lower internal resistance than GEL batteries, which means they can charge faster and handle high currents better.
  • AGM batteries have a longer lifespan and a higher cycle life than GEL batteries, which means they can last longer and provide more power cycles before needing to be replaced.
  • AGM batteries have a better performance in cold temperatures than GEL batteries, but they may need a battery management system to protect them from overheating or overcharging in hot temperatures.
  • GEL batteries have a lower self-discharge rate than AGM batteries, which means they can retain their charge longer when not in use.
  • GEL batteries are more resistant to deep discharge and sulfation than AGM batteries, which means they can handle deeper and more frequent cycles without losing their capacity.

Related: AGM Deep Cycle Battery Guide

FLA Battery vs SLA Battery vs VRLA Battery

Costs: Valve-regulated lead-acid batteries are the most advanced and expensive type of lead-acid batteries. Sealed lead-acid batteries are more expensive and difficult to manufacture than flooded lead-acid batteries.

Energy Density&Cycle Life: VRLA batteries have the highest energy density, longest cycle life, and lowest self-discharge rate, compared with other two lead-acid battery types.

Environmental Resistance: VRLA and sealed lead-acid battery have better resistant to temperature, vibration, and overcharging than flooded lead-acid battery. Besides, they pose less environmental and safety hazards.

Lead-acid Battery Manufacturer

SVC are one of the solar products manufacturers with headquater in China and warehouse in German. If you want to become our reseller and distributor, please contact us.

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