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What is the acid in a lead-acid battery?

    The acid in lead-acid batteries is mainly sulfuric acid. Sulfuric acid plays a vital role in lead-acid batteries. It is a strong acid, colorless and transparent, denser than water, with strong corrosive and oxidizing properties. In lead-acid batteries, sulfuric acid reacts chemically with lead and its oxides to produce electrical energy.

    Lead-acid batteries are a type of chemical battery widely used in automobile starting, uninterruptible power supply (UPS), and industrial power supplies. Its core components include lead (as the cathode material), lead oxide (usually as the positive material), and a dilute sulfuric acid solution. In this article, we will introduce the acid components used in lead-acid batteries in detail, and discuss its working principle, maintenance and common problems. Specifically, the positive electrode of a lead-acid battery is mainly made of lead dioxide, the negative electrode is made of pure lead, and the electrolyte is an aqueous solution of sulfuric acid. When the battery is discharged, the lead dioxide of the positive electrode reacts with the sulfuric acid in the electrolyte, generating lead sulfate, water and electricity; at the same time, the pure lead of the negative electrode also reacts with the sulfuric acid, generating lead sulfate. In the charging process, these reactions are reversed, so that lead sulfate is reconverted into lead dioxide and pure lead, thus completing the storage and release of electrical energy. Therefore, sulfuric acid is the core component in lead-acid batteries, which is directly involved in the chemical reaction inside the battery to realize the conversion and storage of electric energy. At the same time, due to its strong corrosive properties, the use of lead-acid batteries also requires extra attention to safety and protection.


The role of acid in lead-acid batteries

    First of all, the acid used in the lead-acid battery is dilute sulfuric acid (H2SO4). Dilute sulfuric acid plays a vital role as an electrolyte. During discharge, the sulfuric acid reacts with lead to form lead sulfate (PbSO4), while a flow of electrons is generated inside the battery to provide electrical energy. During charging, an external power source restores the battery's charge by pressing the electron flow back through the battery, transforming the lead sulfate back into sulfuric acid and lead.

How lead-acid batteries work

     The process of discharging and charging a lead-acid battery can be described by chemical equations: Discharge process (chemical conversion to electrical energy): Positive pole: PbO2 + 4H+ + SO4^2- + 2e- → PbSO4 + 2H2O Negative: Pb + SO4^2- → PbSO4 + 2e- Overall reaction: Pb + PbO2 + 4H+ + 2SO4^2- → 2PbSO4 + 2H2O Charging process (conversion of electrical energy to chemical energy): Positive pole: PbSO4 + 2H2O → PbO2 + 4H+ + SO4^2- + 2e- Negative pole: PbSO4 + 2e- → Pb + SO4^2- Overall reaction: 2PbSO4 + 2H2O → Pb + PbO2 + 4H+ + 2SO4^2- Since lead-acid batteries utilize chemical reaction equations to store and release energy, the concentration of sulfuric acid in the battery and the state of charge of the battery are closely related. In the state of charge, the concentration of sulfuric acid is higher and the specific gravity of the battery is greater; in the state of discharge, the sulfuric acid is converted so that its concentration decreases, and the specific gravity of the battery decreases as a result.

Lead-acid Battery Maintenance and Common Problems

     In order to ensure that the lead-acid battery's normal work and long service life, maintenance is very important. Regularly check the battery electrolyte (dilute sulfuric acid) level and specific gravity is the basic step of maintenance. When the level is too low, distilled water needs to be replenished instead of dilute sulfuric acid because the battery consumes only water, not sulfuric acid, when discharging. In addition, the battery terminals need to be cleaned regularly to maintain good connections and to avoid corrosion caused by sulfuric acid spills. Common problems with lead-acid batteries include sulfation, over-discharge and under-charging. Sulfation refers to the formation of hard-to-convert crystals of lead sulfate on the electrode plates as a result of prolonged periods of non-charging, which can lead to a reduction in battery capacity or even battery obsolescence. Over-discharge will reduce the concentration of sulfuric acid in the battery below a certain level, which can lead to battery damage. Insufficient charging will cause the internal resistance of the battery to increase, which will reduce the efficiency of the battery. Therefore, it is very crucial to avoid these situations in the process of using to ensure the stability and life extension of the battery. To summarize, the acid in lead-acid batteries refers to dilute sulfuric acid, which plays a central role as a medium in the discharge and charging process of the battery. In order to guarantee the normal operation and prolong the usage time of the battery, suitable maintenance measures are essential. Through regular inspection and maintenance, you can maximize the protection of lead-acid batteries and ensure their safe and efficient operation.

    The advantages of lead-acid batteries include low cost, maturity and stability as well as a high recycling rate, but the disadvantages are also very obvious, such as the high weight, large size, poor charging and discharging efficiency and the potential impact on the environment. With the continuous development of new battery technologies, such as lithium-ion and solid-state batteries, lead-acid batteries are facing more and more alternatives. However, due to their economy and applicability in certain applications, lead-acid batteries are still one of the commonly used power sources in the industrial and automotive fields today.

    Finally, it is worth mentioning that since the chemical composition of batteries contains lead and sulfuric acid, which are harmful substances. Therefore, the recycling and disposal of used lead-acid batteries is also an environmental issue that needs attention. Proper recycling not only reduces environmental pollution, but also recovers lead resources and realizes sustainable development.