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Introduction

In the power system of forklifts, lead-acid batteries play an extremely important role. Their performance directly affects the working efficiency, service life and operating costs of forklifts. As the core component of lead-acid batteries, the plates are like the heart to the human body, playing a decisive role in battery performance. Different types of plates have their own advantages in structure, materials and manufacturing processes. These differences further lead to significant variations in battery capacity, cycle life, charge and discharge performance, etc. A thorough understanding of the types and performance differences of lead-acid battery plates for forklifts is of crucial practical significance for forklift users, manufacturers, and battery R&D personnel. It not only helps users precisely select the appropriate forklift battery based on actual working conditions, improving operational efficiency and reducing operating costs, but also provides a strong basis for manufacturers to optimize product design and enhance product competitiveness. At the same time, it points out the direction of technological innovation for battery R&D personnel and promotes the continuous progress of lead-acid battery technology.

The plates play a crucial role in this series of chemical reactions. It is not only the site of electrochemical reactions, providing attachment support for active substances to ensure the orderly progress of the reactions, but also an important channel for current conduction. During charging, the plates efficiently transfer the electrical energy input from the outside to the active substance, promoting the chemical reaction to proceed in the direction of energy storage. When discharging, it can quickly conduct out the electrical energy generated by the reaction of active substances to supply power to the motors and other equipment of forklifts. It can be said that the performance of the plates directly affects key performance indicators of lead-acid batteries such as charging and discharging efficiency, capacity, and cycle life, and is the core element determining the overall performance of the battery.

The main types of lead-acid battery plates for forklifts

Pasted plate

Pasted plates are widely used in the field of lead-acid batteries and are a relatively common type of plate. Its structural features are distinct. The grid, as the skeleton of the entire plate, is usually made of lead alloy. It not only provides solid support for the active material, ensuring that it does not easily fall off during charging and discharging, but also assumes the important responsibility of conducting current, just like the combination of bones and blood vessels in the human body. On the grid-like structure of the grid, lead paste-like active substances are evenly coated. The main component of the active material of the positive plate is lead dioxide. This material has a high electrochemical activity and can release electrons through complex chemical reactions during the discharge process to supply power to the battery. The active material of the negative plate is mainly sponge-like lead. Its unique porous structure provides a large specific surface area for electrochemical reactions, which helps to improve the charging and discharging performance of the battery.

The manufacturing process of paste-type plates is relatively mature and the flow is clear. Firstly, lead alloy grating is prepared. Through processes such as casting or stamping, lead alloy is processed into grid-like grating with specific shapes and sizes. During this process, the composition ratio of the alloy and the manufacturing accuracy of the grating need to be strictly controlled to ensure that the grating has good mechanical strength and electrical conductivity. Next, the lead paste is prepared. Lead powder, sulfuric acid, additives, etc. are mixed in a certain proportion, and an appropriate amount of water is added, then stirred evenly to form a lead paste with suitable plasticity. In the paste application stage, a dedicated coating device is used to evenly apply the prepared lead paste onto the surface of the grid. The application thickness must be strictly controlled to ensure the consistency and performance stability of the plates. After the paste application is completed, the plates undergo curing treatment. By controlling the temperature and humidity, the moisture in the lead paste gradually evaporates, and a series of physical and chemical changes occur simultaneously, enhancing the adhesion between the active material and the grid and improving the mechanical strength of the plates. Finally, the formation operation is carried out. The plates are placed in the electrolyte. Through the charging and discharging process, the active substances on the plates are transformed into an electrochemically active state, completing the preparation of the plates.

Tubular plates

Tubular plates occupy an important position in the field of lead-acid batteries with their unique structural design, in sharp contrast to pasted plates. The structure of its positive plate is particularly special. The conductive skeleton is usually made of lead alloy and is in the shape of a column or a rod, providing good electrical conductivity and mechanical support for the entire plate. Outside the conductive skeleton, there are tightly woven fiber tubes, which are generally made of high-performance materials such as glass fiber and have good acid resistance and mechanical strength. The interior of the fiber tube is filled with active substances. Under the restraint of the fiber tube, the active substances are not easy to fall off, which greatly improves the stability and service life of the plate. Compared with the paste-type plates, this structural design of the tubular plates has changed the contact mode between the active material and the electrolyte, thereby having a profound impact on the battery performance.

The manufacturing process of tubular plates is equally complex and delicate. First, a conductive skeleton is manufactured. Through precision casting or other forming processes, the dimensional accuracy and electrical conductivity of the skeleton are ensured. Then, the woven fiber tubes are accurately placed on the conductive skeleton. This process requires strict control of the tension and placement of the fiber tubes to ensure a tight fit with the skeleton. Next, the prepared active substances are filled into the fiber tubes. During the filling process, it is necessary to ensure the uniformity and density of the active substances to fully exert their electrochemical performance. After the filling is completed, a series of post-treatment processes are carried out on the plates, such as curing and drying, to further improve the performance and quality of the plates.

Other special plates

In addition to the common paste-type plates and tubular plates, with the continuous advancement of technology and the increasingly diverse market demands, some plates with special structures or functions have gradually emerged. For example, plates made of new materials, such as graphene-reinforced plates. Graphene, as a new type of material with excellent electrical and mechanical properties, has been introduced into the manufacturing of plates. In this type of plate, graphene is compounded with traditional lead alloys or active substances to form a unique microstructure. The high electrical conductivity of graphene can significantly reduce the internal resistance of the plates, improve the charging and discharging efficiency of the battery, and make the forklift start and accelerate more quickly. Its high strength and good flexibility can also enhance the mechanical properties of the plates, effectively reduce the shedding of active substances during charging and discharging, and extend the cycle life of the battery.

There are also plates designed for specific application scenarios, such as high-temperature resistant plates that can adapt to high-temperature environments. Under some special working conditions, forklifts may need to operate for long periods in high-temperature environments, which poses a severe challenge to battery plates. High-temperature resistant plates are made by optimizing the material formula and structural design, using special high-temperature resistant alloys as the grid material, and modifying the active substances at the same time, so that they can maintain stable electrochemical performance at high temperatures. This type of plate can effectively resist the negative impact of high temperatures on battery performance, ensuring the normal operation of forklifts in high-temperature environments and broadening the application scope of lead-acid batteries.

The performance differences of different types of plates

Capacity performance

The type of plates has a crucial impact on the capacity of forklift lead-acid batteries. From a theoretical perspective, tubular plates often have certain advantages in terms of capacity. Due to its unique structure, the active substances filled in the fiber tubes can come into contact with the electrolyte relatively fully. Moreover, the presence of the fiber tubes makes the distribution of the active substances more uniform, effectively increasing the area of the electrochemical reaction. In contrast, although the paste-coated plates can also ensure the contact between the active material and the electrolyte, they are slightly inferior to the tubular plates in terms of the uniformity of the active material distribution and the effective reaction area.

The actual test data also strongly confirm this theoretical analysis. Under the same specifications, the capacity of lead-acid batteries with tubular plates is usually about 10% to 20% higher than that of batteries with pasted plates. This difference in capacity is of great significance in the actual operation of forklifts. A battery with a higher capacity means that forklifts can work continuously for a longer time, reduce the frequency of charging, and thereby improve work efficiency. For some forklift scenarios that require continuous operation for long periods of time, such as the handling of goods in large logistics warehouses, lead-acid batteries with tubular plates can better meet the demands, avoid operation interruptions caused by frequent charging, and improve the overall logistics operation efficiency.

Cycle life

Cycle life is a key indicator for measuring the durability of forklift lead-acid batteries, and different types of plates show significant differences in this aspect. During the recycling process of the paste-type plates, as the active material is directly coated on the surface of the grid, the active material will undergo cyclic changes of expansion and contraction during repeated charging and discharging processes. Such frequent volume changes can easily lead to a decrease in the adhesion between the active material and the grid, which in turn causes the active material to gradually fall off, affecting the performance and lifespan of the battery.

Tubular plates have significant advantages in terms of cycle life. Its active substances are tightly wrapped by fiber tubes. The fiber tubes not only provide good support for the active substances but also effectively buffer the volume changes of the active substances during the charging and discharging process, reducing the risk of active substance shedding. In addition, the structure of the tubular plates makes the distribution of the electrolyte inside the plates more uniform, reducing the possibility of local overheating or overcharging and overdischarging of the plates, and further extending the cycle life of the battery. During the long-term use of forklifts, batteries with a long cycle life can reduce the frequency of battery replacement and lower operating costs. For some forklifts with high usage frequency, such as those operating in ports, docks and other places, the use of tubular plate batteries can significantly enhance the stability and economy of equipment operation, and reduce the downtime and replacement costs caused by short battery life.

Charge and discharge performance

Lead-acid batteries with different types of plates also have significant differences in charging and discharging performance. In terms of charging acceptance capacity, tubular plates perform relatively well. Due to its structural characteristics, the contact area between the active substance and the electrolyte is large and uniform, which enables the current to be more evenly distributed on the plates during the charging process. The active substance can receive the charging current more efficiently, thereby accelerating the charging speed. Research data shows that under the same charging conditions, the time required for lead-acid batteries with tubular plates to reach full charge is about 10% to 20% shorter than that of batteries with pasted plates. For example, a certain type of paste-type plate battery takes 8 hours to be fully charged, while the same type of battery using tubular plates only needs 6.4-7.2 hours.

In terms of discharge performance, both pasted plates and tubular plates have their own characteristics. At the initial stage of discharge, the paste-type plate can quickly release a large current. This is because its active material is directly exposed to the electrolyte, and the reaction initiation speed is relatively fast, which can meet the working conditions of forklifts that require a large current in an instant during start-up and acceleration. However, as the discharge continues, due to issues such as the uneven consumption and shedding of active substances, the discharge voltage will gradually decrease and the discharge performance will gradually weaken. During the discharge process of the tubular plate, although the initial discharge current may be slightly smaller than that of the pasted plate, it can maintain a relatively stable discharge voltage and current output. This is attributed to its structural advantage of uniform distribution of active materials and low risk of shedding. When forklifts perform long-term and stable handling operations, tubular plate batteries can provide more stable power output, ensuring the smoothness and reliability of forklift operation.

Factors affecting the performance of the plates

Plate material

The material of the plates is one of the key factors determining the performance of the plates and has a profound impact on the overall performance of lead-acid batteries. The performance of the grid material, as the supporting framework of the plates and the current conduction carrier, is of vital importance. The traditional lead-antimony alloy grid has excellent casting properties and mechanical strength, and can provide reliable support for active substances. However, lead-antimony alloys have some obvious drawbacks. For instance, during the charging process, the antimony element can reduce the hydrogen evolution overpotential, causing the battery to easily produce hydrogen and resulting in water loss. This requires frequent water replenishment for maintenance, which to some extent increases the usage cost and maintenance difficulty. Meanwhile, antimony ions may migrate during charging and discharging, leading to an increase in the battery's self-discharge rate and affecting its storage performance.

To solve these problems of lead-antimony alloys, lead-calcium alloys emerged. Lead-calcium alloy grid plates have a relatively low hydrogen evolution overpotential, which can significantly reduce water decomposition during the battery charging process and lower the water loss rate, thereby achieving maintenance-free or low-maintenance functions for the battery. In addition, the self-discharge rate of lead-calcium alloy is relatively low, which enables the battery to better maintain its power during storage and enhances its storage performance. However, the early lead-calcium alloys also had some shortcomings, such as relatively poor deep cycle performance, and a rapid decline in battery capacity after multiple charge and discharge cycles. To further optimize the performance of lead-calcium alloys, researchers added other elements such as tin and aluminum to them, forming multi-component alloys. For example, lead-calcium-tin alloy improves the conductivity and corrosion resistance of the grid by adding tin element, refines the alloy lattice, effectively inhibits the early capacity attenuation phenomenon, and enhances the deep cycle performance of the battery. The addition of aluminum in lead-calcium aluminum alloy enhances the mechanical strength and creep resistance of the alloy, making the grid more stable and less prone to deformation during long-term use.

The active substance material also plays a decisive role in the performance of the plates. The crystal structure, purity and particle size of lead dioxide, the active material of the positive plate, all affect the performance of the battery. Generally speaking, lead dioxide with high purity and an appropriate crystal structure can enhance the charging and discharging efficiency and capacity of batteries. The porosity and specific surface area of the spongy lead, the active material of the negative plate, are also of crucial importance. Spongy lead with high porosity and large specific surface area can provide more active sites for electrochemical reactions, promote the transport of electrons and ions, and thereby enhance the performance of batteries.