by BatterySharks
What is a lead-acid battery?
A lead-acid battery is a fundamental type of rechargeable battery. It is made with lead electrodes immersed in a sulfuric acid electrolyte to store and release electrical energy. Lead-acid batteries have been in use for over a century and remain one of the most widely used types of batteries due to their reliability, low cost, and relatively simple construction.
How is a lead-acid battery constructed?
Lead-acid batteries consist of smaller cells connected in series - to learn more about battery cells and ways to connect them, read more here. Each cell contains a series of lead plates immersed in a sulfuric acid electrolyte solution. These plates are typically made of lead dioxide (PbO2) and sponge lead (Pb), and they are separated by insulating material to prevent short circuits.
How do lead-acid batteries work?
During discharge, a battery is being used to supply electric energy to an external circuit. The lead dioxide reacts with the sulfuric acid, releasing electrons and turning into lead sulfate. At the same time, the sponge lead reacts with the sulfuric acid to form lead sulfate as well, while releasing more electrons. These electrons flow through the external circuit, powering connected devices, before returning to the battery's positive terminal. This cycle continues until the battery's charge is depleted.
During charging, an external electrical power source is used to apply a voltage to the battery, causing a chemical reaction. This reaction converts lead sulfate (which forms on the electrodes during discharge) back into lead dioxide and sponge lead. This process restores the battery's charge and prepares it for further use.
What types of lead-acid batteries are there?
- Flooded lead-acid batteries, also known as wet-cell batteries: Flooded lead-acid batteries have liquid electrolyte that circulates freely between the lead plates. These batteries require regular maintenance, as the water that evaporates with time needs to be regularly replenished and electrolyte levels need to be monitored.
- Valve-regulated lead-acid batteries (VRLA batteries), also known as sealed lead-acid batteries (SLA batteries): These batteries are sealed, meaning electrolyte cannot leak or spill out. They also don’t require adding water to the cells, which makes them maintenance-free. The term valve-regulated refers to a feature that allows the batteries to release produced during charging excess gasses to escape. This happens through pressure-relief valves, located under the top of the battery, that allow the gasses out without letting any air in. This feature makes these batteries safer and the preferred type of battery when maintenance-free operation is required.
VRLA batteries come in two main types:
- Absorbent Glass Mat (AGM) batteries: AGM batteries use a fiberglass mat separator to absorb the electrolyte and hold it in place, providing enhanced resistance to vibration and shock.
- Gel batteries: Gel batteries use a silica gel to immobilize the electrolyte. They offer similar benefits to AGM batteries but may have slightly different performance characteristics.
What are lead-acid batteries used for?
Lead-acid batteries find application in a wide range of industries as well as home and office settings. They are a popular choice is application where a reliable backup power is needed
- Automotive: Lead-acid batteries are commonly used in vehicles for starting, lighting, and ignition (SLI) systems.
- Mobility: They are widely used in electric scooters, wheelchairs, stairlifts, golf carts, etc.
- Backup Power: They provide backup power in uninterruptible power supplies (UPS), emergency lighting systems, and telecommunications equipment.
- Renewable Energy Storage: Lead-acid batteries are used to store excess energy generated by solar panels and wind turbines for later use.
- Industrial: They power forklifts, industrial cleaning equipment, and other heavy machinery.
For a variety of applications, lead-acid batteries have proven to be a dependable and affordable energy storage solution over the years. Lead-acid batteries are still very important, even if more recent battery technologies like lithium-ion are gaining ground. This is especially true in areas where lead-acid batteries' dependability and price are highly appreciated. Lead-acid battery performance and design may continue to advance as battery research and development continues, guaranteeing their continued use in our dynamic energy environment.
Lead-acid batteries and the environment
Because of their sealed construction, VRLA batteries are thought to be more environmentally benign than conventional flooded lead-acid batteries; nonetheless, they still contain lead and sulfuric acid, which can be dangerous if not handled or disposed of properly. There are recycling programs in place to handle spent VRLA battery disposal in an appropriate manner.
Overall, VRLA batteries offer a balance between cost, performance, and maintenance requirements, making them a popular choice for various standby power applications.
