Lead-acid batteries can be first described by type or construction:
Sealed Valve Regulated or Starved Electrolyte batteries
Sealed Valve Regulated Lead-acid (VRLA) or starved electrolyte AGM or GEL types use a solution of sulfuric acid and water completely suspended into a gel-like material using silicate additives or absorbed into a woven glass fibre mat (AGM). There is no excess electrolyte to leak out even if tipped or turned upside down. This sealed nonspillable characteristic is a product of the construction and chemistry of the battery design.
Sealed maintenance-free and accessible maintenance-free flooded batteries
Sealed maintenance-free flooded and accessible maintenance-free flooded types use a solution of sulfuric acid and water that can spill out of the battery if tipped. Even though the sealed maintenance-free flooded batteries are not accessible, electrolytes will eventually leak out through the central degassing manifold vents if tipped. Some maintenance-free flooded batteries have removable filler caps making the battery accessible.
Maintenance required batteries
These 2V, 6V or 12V industrial, commercial, general-purpose deep-cycle and hybrid batteries use a solution of sulfuric acid and water that can spill out of the battery if tipped. These batteries generally require high levels of watering and maintenance.
Lead-acid battery chemistry
A battery can be described by the chemistry of the alloys used in the production of the batteries'' grids or plates:
Lead-acid battery applications
Batteries can be referred to by the application they were designed for. These applications will range from pure starting to pure cycling or deep cycling and float service or standby/backup power (many application requirements are somewhere in between).
The lead acid battery is the most used secondary battery in the world. The most common is the SLI battery used for motor vehicles for engine Starting, vehicle Lighting and engine Ignition, however it has many other applications (such as communications devices, emergency lighting systems and power tools) due to its cheapness and good performance.
It was first developed in 1860 by Raymond Gaston Planté. Strips of lead foil with coarse cloth in between were rolled into a spiral and immersed in a 10% solution of sulfuric acid. The cell was further developed by initially coating the lead with oxides, then by forming plates of lead oxide by coating an oxide paste onto grids. The electrodes were also changed to a tubular design.
Voltage: 2 V Discharge characteristics: Generally quite curved, particularly at higher discharge rate. Best performance with intermittent discharge. Service Life: Several years
The lead acid battery uses lead as the anode and lead dioxide as the cathode, with an acid electrolyte.
The following half-cell reactions take place inside the cell during discharge:
At the anode: Pb + HSO4– → PbSO4 + H+ + 2e–
At the cathode: PbO2 + 3H+ + HSO4– + 2e– → PbSO4 + 2H2O
Overall: Pb + PbO2 +2H2SO4 → 2PbSO4 + 2H2O
During charging, given the high voltage, water is dissociated at the two electrodes, and gaseous hydrogen and oxygen products are readily formed leading to the loss of the electrolyte and a potentially explosive situation. Sealed batteries are made safer by allowing the gases to recombine within the cell.
Under certain circumstances the lead sulfate products at both the electrodes achieve an irreversible state, making the recharging process very difficult.
Pure lead is too soft to use as a grid material so in general the lead is hardened by the addition of 4 – 6% antimony. However, during the operation of the battery the antinomy dissolves and migrates to the anode where it alters the cell voltage. This means that the water consumption in the cell increases and frequent maintenance is necessary. There are two possible solutions to this problem:
(1) Using below 4% the battery water consumption is reduced, however it is then necessary to add small amounts of other elements such as sulfur, copper, arsenic and selenium. These act as grain refiners, decreasing the grain size of the lead and thereby increasing its hardness and strength. (2) Alkaline earth metals such as calcium can be used to stiffen the lead. This is often used for telephone applications, and for no maintenance automotive batteries, since a more stable battery is required. A typical alloy would be 0.03 – 0.10% calcium and 0.5 – 1.0% tin (to enhance mechanical and corrosion properties).
The function of the grid is to hold the active material and to conduct electricity between the active material and the battery terminals. The design is a simple grid framework with a “tab” or “lug” for connection to the terminal post.
“Book mold” casting is the most common method of production for the grid. Permanent steel molds are made from blocks by machining. The molds are closed and filled with sufficient molten lead to fill the mold, leaving some excess to form a sprue, which is then removed by cutting or stamping. Grids can also be formed by mechanical working, either by cutting deep grooves into a sheet of steel, or by rolling up crimped strips and inserting them into holes in a cast plate, see Introduction to Deformation Processes TLP.
Red lead (Pb3O4) can also be added to the PbO formed by these methods, as it is more conductive. This is produced from PbO by roasting in a flow of air. This process would also increase the percentage of lead oxide in the material.
The oxide is mixed with water, sulfuric acid and a mixer, and then mixed to form a paste. It is then integrated with the grid by extrusion to form a plate. The paste is pressed by a machine into the interstices of the grid. They are partially dried, then stacked for curing. The curing process transforms the paste to a cohesive, porous solid. The most typical form of curing is “hydrosetting”: the grid is left at low temperature and humidity (25 – 40°C and 8 – 20% H2O) for between 24 and 72 hours.
About Lead acid battery chemistry explained
As the photovoltaic (PV) industry continues to evolve, advancements in Lead acid battery chemistry explained have become critical to optimizing the utilization of renewable energy sources. From innovative battery technologies to intelligent energy management systems, these solutions are transforming the way we store and distribute solar-generated electricity.
When you're looking for the latest and most efficient Lead acid battery chemistry explained for your PV project, our website offers a comprehensive selection of cutting-edge products designed to meet your specific requirements. Whether you're a renewable energy developer, utility company, or commercial enterprise looking to reduce your carbon footprint, we have the solutions to help you harness the full potential of solar energy.
By interacting with our online customer service, you'll gain a deep understanding of the various Lead acid battery chemistry explained featured in our extensive catalog, such as high-efficiency storage batteries and intelligent energy management systems, and how they work together to provide a stable and reliable power supply for your PV projects.
