Lead-acid batteries remain one of the most widely used energy sources due to their reliability, accessibility and simplicity of design. The main role in their work is played by a liquid electrolyte, which not only ensures the transfer of ions between the electrodes, but also participates in chemical reactions that convert chemical energy into electrical energy and vice versa.
In lead-acid batteries, the electrolyte is dilute sulfuric acid. The concentration of the electrolyte varies depending on the specific design and operating mode, but it usually ranges from about 30% to 40% by weight.
The electrolyte consists of:
- Sulfuric acid (HSO₄), which provides ionic conductivity due to the presence of H⁺ (protons) and SO₄2⁻ (sulfate ions) ions. When fully charged, this acid helps to ensure an optimal level of electrical conductivity and determine the characteristics of discharge and charging reactions.
- Water (HO), which dilutes sulfuric acid, regulates the concentration and provides conditions for the reaction.
The volume of electrolyte and its concentration have a significant impact on battery parameters such as capacity, internal resistance, and service life. Regular monitoring of the electrolyte level is an important maintenance component in the operation of lead-acid batteries.
What is the role of electrolyte in battery operation?
There are two electric statuses inside the lead-acid battery – one made of lead (Pb) and the other made of lead dioxide (PBO₂). Both of them are immersed in a liquid electrolyte – dilute sulfuric acid (HSO₄).
When the battery is discharged:
- at the positive electrode (PBO₂), sulfuric acid reacts with lead dioxide, turning it into lead sulfate (pbso₄), and releases water;
- at the negative electrode (Pb), lead turns into lead sulfate (PBSO₄) and releases electrons.
These two reactions cause the formation of lead sulfate on the electrodes, and sulfate ions move through the liquid electrolyte. As a result, an electric current is generated that can be used to power devices.
When the battery is charged, the reverse transformation occurs: lead sulfate is converted back into active materials (Pb and Pbo₂), and sulfate and water return to their original state.
It is also worth noting that during operation and discharge, the electrolyte becomes saturated with lead sulfate (PBSO₄), which causes sedimentation on the electrodes and reduces their active area. This is why periodic charging-quenching helps to dissolve sediment and restore battery capacity.
The use of liquid electrolyte in lead – acid batteries provides a number of advantages. The main thing is high electrical conductivity, which ensures efficient ion transfer and low internal resistance. This factor directly affects the battery’s ability to quickly give or take charge while maintaining high power, but at the same time, such an electrolyte requires careful maintenance.
A liquid electrolyte based on dilute sulfuric acid is the heart of lead-acid batteries, providing not only ion conduction, but also participation in essential chemical processes. Its composition and concentration directly affect the efficiency, durability and safety of the battery. Constant research and improvement of the electrolyte composition make it possible to improve the parameters of these classic batteries, making them one of the most reliable energy sources for various industrial and domestic applications.
Edcon brand batteries are maintenance – free batteries that do not require monitoring of the electrolyte level. They are designed so that the liquid electrolyte inside is sealed tightly, and its level does not change during operation, which makes them convenient and easy to use.
