The Manufacturing Process of a Lead-Acid Battery

What is a Lead-Acid Battery?

A lead-acid battery is a type of rechargeable battery used in many common applications such as starting an automobile engine. It is called a “lead-acid” battery because the two primary components that allow the battery to charge and discharge electrical current are lead and acid (in most case, sulfuric acid).

Lead-acid batteries were invented in 1859 by Gaston Plante̒, a French physicist. Despite this being the first example of a rechargeable battery, the original basic design is still in use today. Further, even with subsequent battery innovations, lead-acid batteries continue to command approximately 50% of the battery market share in terms of value of product. Their continued success can be largely attributed to their low cost and universal use in starting internal combustion engines.

How do Lead-Acid Batteries Work?

It is important to note that lead-acid batteries do not produce an electrical charge. They are only capable of receiving a charge from another source and discharging it later. The battery uses chemical reactions between the lead and acid to both store and discharge electrical current. 

Batteries are divided into cells. Each cell is capable of storing two volts. Therefore, a 12-volt battery will have six cells. A cell is comprised of two lead plates. The positive plate is called the “cathode” and is made of lead oxide. The negative plate is called the “anode” and is made of sponge lead. A non-conductive separator is installed between the two to prevent the plates from touching and causing a short circuit. The plates are immersed in an electrolyte solution of 30% – 50% sulfuric acid.

The battery works through a complex electrochemical reaction that involves sending and receiving electrons between the anode and cathode plates. This causes a reaction with the sulfuric acid at the ionic level. During the course of all of this subatomic activity, the battery is able to receive or provide electrical current.   

The amount of charge which lead-acid batteries can store is dependent upon the size and number of battery plates and the amount of electrolyte contained in the battery case. The cells are connected together in series to produce the total voltage charge of the battery, i.e., 12-volt (six cells), 24-volt (twelve cells), etc. 

In addition to the plates, the amount and configuration of the electrolyte can also make a difference with the performance of the battery. Aside from the traditional liquid electrolyte solution, there are GEL and AGM batteries. “GEL” is an acronym for gelified electrolyte lead acid. GEL batteries use a silica-based additive that turns the liquid into a gel. “AGM” stands for absorbed glass mat. AGM batteries infuse the electrolyte into finely spun glass fibers that are then tightly packed into the battery. Both batteries are known for their longer life, better performance, and operation at low temperatures.

Where are Lead-Acid Batteries Used?

Lead-acid batteries are most commonly used to provide starting power for internal combustion engines. This includes cars, trucks, trains, planes, and ships. Their almost complete domination in this market, and thus prolific availability, has led to several other uses. 

Lead-acid batteries are often used as back-up power sources for all manner of electrical equipment that requires an uninterruptible power supply. This includes call centers, mobile phone towers, and hospitals. When installed in large numbers they become a battery energy storage system and are used by utility companies and renewable energy operators to store excess power production.

How are Lead-Acid Batteries Made?

With the correct equipment, battery manufacturing is not terribly complicated. A battery has few parts, and none of them move. However, any time energy is stored, it is not without risk. After all, the battery is managing a complicated electrochemical reaction in a small space. Batteries emit highly flammable hydrogen gas when they are charged and contain sulfuric acid. To minimize risk, batteries must be manufactured according to strict specifications.

Battery production usually begins with creation of the plates. When the plates are connected together, they make up the battery grid. There are two methods for manufacturing plates: oxide and grid production, and pasting and curing.

The first step in oxide and grid production is making lead oxide. There are a few options for manufacturers to create lead oxide from lead ingots. After creating lead oxide, it and the sponge lead are turned into plates. This is accomplished through casting the plates in molds or by stamping out the plates and milling the edges.

Pasting and curing involves coating the lead grid plates with a proprietary paste. The paste is specially designed for either the positive or negative plates. The pasted plates are then cured in an oven to adhere the paste to the plates.

The next step involves assembling the components into the battery case. The positive and negative plates are arranged with a separator inserted to prevent them from touching. Intercell connectors are installed to keep the cells from separating. 

The positive and negative plates are each bound together in the “burning” process. During burning, all of the positive and negative plates are each welded to a lead strap which is in turn welded to the respective positive or negative battery post. All of these elements are then inserted into the battery case. 

After the battery is assembled, it is filled with electrolyte solution. After filling, the battery goes through formation or charging. Then, after several rounds of charging/discharging, the battery reaches optimal performance. The battery is cleaned and washed and sent for distribution. There are several quality assurance and safety tests conducted throughout the battery manufacturing process.

What Equipment is Used to Manufacture Batteries?

With so few components, often the difference between a satisfactory battery and an exceptional battery lies in the equipment used to manufacture it. Batteries are intended to be produced according to precise manufacturing specifications and tolerances. Meeting these requirements is critical because a precisely built battery will always outperform and outsell an out-of-spec battery.

Meeting these exact specifications with consistency is most possible with automated equipment. Automation greatly reduces the human error component. At the same time, automation considerably improves productivity.

Fortunately for battery manufacturers, automated equipment is available to maximize efficiency and precision at virtually every step of the process. Plate production and assembly, electrolyte filling, lid sealing, and battery testing are just of the few steps that benefit from high-quality, automated battery manufacturing equipment. 

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Lead-acid batteries are an integral part of society. Without them, engines do not crank, and critical equipment can fail if the power is interrupted. Their simple design remains a lasting feat in human innovation. And advances in battery manufacturing equipment technology make it possible to produce reliable, high performing batteries in quantities sufficient to meet market demand. The ability to consistently deliver this exceptional product lies largely with the equipment used to produce the battery.