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In the fields of modern logistics and industrial handling, forklifts, as an efficient material handling equipment, are widely used in various industries. As the main power source of forklifts, the performance parameters of lead-acid batteries for forklifts directly affect the working efficiency, service life and operating costs of forklifts. Therefore, it is of great practical significance to have an in-depth understanding of the performance parameters of forklift lead-acid batteries.

Analysis of Main Performance parameters

Voltage

Rated voltage: The rated voltage of a single forklift lead-acid battery is usually 2V. This is determined by the basic chemical reaction characteristics of lead-acid batteries. In practical applications, to meet the different working voltage requirements of forklifts, multiple individual batteries are connected in series to form a battery pack. The common voltages of forklift lead-acid battery packs include 24V, 48V, 80V, etc. For instance, a 24V forklift lead-acid battery pack is composed of 12 individual 2V batteries connected in series. The rated voltage determines the working voltage platform of the forklift's electrical system, which directly affects the rotational speed, output power of the forklift motor and the overall performance of the forklift. If the voltage is too low, it may lead to insufficient output power of the motor, making it difficult for the forklift to start and slowing down its running speed, thus failing to meet the normal requirements of handling operations. If the voltage is too high, it may cause damage to the electrical components of the forklift and affect its service life.

Charging and discharging voltages: During the charging process, as the battery is gradually fully charged, the battery voltage will gradually increase. Generally speaking, when the voltage of a single battery reaches approximately 2.4V to 2.5V, the battery enters the overcharging stage, at which point a large amount of gas (hydrogen and oxygen) is produced, which is the result of water electrolysis. Therefore, when charging, it is necessary to strictly control the charging voltage to avoid overcharging causing damage to the battery. During discharge, as the battery power is consumed, the voltage will gradually decrease. When the voltage of a single battery drops to approximately 1.75V - 1.8V, it is generally considered that the battery is approaching the discharge termination state. If over-discharge continues, it will cause sulfation of the battery plates and shorten the battery's lifespan. Therefore, understanding the voltage variation patterns of batteries during charging and discharging is of vital importance for the rational use and maintenance of forklift lead-acid batteries.

Capacity

Rated capacity: Capacity is an important indicator for measuring the electrical energy storage capacity of forklift lead-acid batteries, usually measured in ampere-hours (Ah). It indicates the amount of electricity that a battery can continuously discharge under specific discharge conditions (such as specified discharge current, temperature, etc.). For instance, a battery with a rated capacity of 500Ah indicates that it can continuously discharge for 500 amperes of hours at a certain discharge current. The size of the capacity is directly related to the driving range of the forklift. For forklifts that often need to operate continuously for long periods of time, choosing large-capacity batteries can reduce the number of charging cycles and improve work efficiency. Generally speaking, the greater the operation intensity and the longer the working time of a forklift, the greater the battery capacity it requires. For instance, in large logistics warehouses, forklifts need to frequently move goods, and their daily working hours may exceed 8 hours. In such cases, it is necessary to be equipped with large-capacity batteries, such as 600Ah or even higher capacity batteries, to ensure that the forklifts can complete the operation tasks within a working day without frequent charging.

Actual capacity and influencing factors: The actual capacity of a battery is not fixed; it is affected by multiple factors. First is the discharge current. The greater the discharge current, the lower the actual capacity of the battery. This is because when a large current is discharged, the chemical reaction rate inside the battery increases, which leads to the rapid formation of lead sulfate on the surface of the plates, blocking the pores of the plates and reducing the contact area between the electrolyte and the plates, thereby lowering the actual capacity of the battery. Secondly, temperature also has a significant impact on battery capacity. In a low-temperature environment, the viscosity of the electrolyte increases, the diffusion rate of ions slows down, and the internal resistance of the battery increases, resulting in a decrease in the actual capacity of the battery. Generally speaking, when the ambient temperature drops below 0℃, the battery capacity may decrease by 20% to 30% or even more. On the contrary, in a high-temperature environment, although the internal resistance of the battery will decrease, the excessively high temperature will accelerate the chemical reactions inside the battery, leading to intensified corrosion of the plates and faster evaporation of the electrolyte, which will also affect the actual capacity and service life of the battery. In addition, the battery's service life, the number of charge and discharge cycles, as well as maintenance conditions, will also have an impact on the actual capacity. As the years of use increase and the number of charge and discharge cycles grows, the battery plates will gradually age and the active substances will decrease, leading to a gradual decline in battery capacity.

Size and weight

Size specifications: The size of forklift lead-acid batteries varies depending on the model and capacity. Common dimensional parameters include length, width and height. The design of battery size needs to take into account the space limitations of the forklift battery compartment. It must be ensured that the battery can be smoothly installed on the forklift and will not affect the normal operation of other components of the forklift. Different brands and models of forklifts have specific requirements for the size and shape of their battery compartments. For instance, the battery compartments of some small forklifts are relatively small and need to be equipped with compact batteries. Large forklifts, due to their heavy workload and high required battery capacity, correspondingly have larger battery sizes. When choosing lead-acid batteries for forklifts, it is essential to strictly select the appropriate batteries based on the model of the forklift and the size of the battery compartment. Otherwise, problems such as difficult installation and loose battery fixation may occur, affecting the safe operation of the forklift.

Weight: Lead-acid batteries are relatively heavy, which is due to the use of lead for the internal plates and the presence of electrolyte. Weight is closely related to capacity. Generally speaking, the larger the capacity of a battery, the greater its weight. The weight of the battery has a certain impact on the performance of the forklift. An overly heavy battery will increase the overall load of the forklift, reduce its handling flexibility, especially when frequently turning and lifting goods, it will exert greater pressure on the forklift's motor and hydraulic system, increase energy consumption, and may also affect the braking performance of the forklift. Therefore, when designing and selecting lead-acid batteries for forklifts, it is necessary to optimize the battery weight as much as possible under the premise of meeting the capacity requirements, so as to balance the performance and working efficiency of the forklift.

Charging time

Conventional charging time: Charging time refers to the time required to charge a battery from a completely discharged state to a fully charged state. The charging time of lead-acid batteries in forklifts mainly depends on the battery capacity, the power of the charger and the charging method. Under normal circumstances, when charging the lead-acid battery of a forklift with a conventional charger, the charging time is relatively long. For instance, for a battery with a capacity of 400Ah, using a charger with a power of 10kW, it takes approximately 8 to 10 hours to fully charge the battery. This is because during the charging process, as the battery power gradually increases, the internal resistance of the battery will increase and the charging current will gradually decrease to prevent overcharging of the battery. If the charging time is too short, it may lead to insufficient battery charging, affecting the forklift's endurance. Overcharging, on the other hand, can cause damage to the battery and shorten its lifespan.

Fast charging technology and its impact: To enhance the operational efficiency of forklifts and reduce charging waiting time, some lead-acid batteries in forklifts have begun to adopt fast charging technology. Fast chargers can charge batteries in a relatively short time by increasing the charging power. For instance, by using a fast charger with a power of 40kW or even higher, the charging time of the aforementioned 400Ah battery can be reduced to 2-3 hours. However, although fast charging can save time, it also brings some problems. When charging at high speed, the chemical reactions inside the battery accelerate, generating more heat. If the heat is not dissipated in time, it may cause the battery temperature to rise too high, accelerating the aging and damage of the battery plates. At the same time, it will also increase the rate of water loss of the battery, requiring more frequent replenishment of the electrolyte. Therefore, when using fast charging technology, it is necessary to be equipped with a good heat dissipation system and battery management system to ensure that the battery is charged within a safe temperature range, and strictly control the charging time and charging current to avoid damage to the battery.

Cycle life

Definition and Importance: Cycle life refers to the number of complete charge and discharge cycles that a forklift lead-acid battery can undergo under specific charge and discharge conditions. A complete charge and discharge cycle refers to the process in which a battery discharges from a fully charged state to a specified terminal voltage and then charges back to a fully charged state. Cycle life is an important indicator for measuring the service life of batteries, and it is directly related to the operating costs of forklifts. Generally speaking, the longer the cycle life, the longer the battery's service life will be, and the fewer times the battery needs to be replaced during the forklift's usage cycle, thereby reducing maintenance costs and downtime. For enterprises that frequently use forklifts, choosing batteries with a long cycle life can significantly enhance economic benefits.

Factors affecting cycle life: There are numerous factors influencing the cycle life of lead-acid batteries in forklifts. First is the depth of charge and discharge, that is, the extent to which the battery discharges each time. Deep discharge can cause significant damage to the battery plates, accelerate the sulfation of the plates and the shedding of active substances, thereby shortening the battery's cycle life. Therefore, in practical use, it is necessary to avoid over-discharging the battery as much as possible and maintain an appropriate depth of discharge. Generally, it is recommended to control the depth of discharge between 50% and 70%. Secondly, the charging method and the control of charging voltage and current also have a significant impact on the cycle life. Overcharging can cause excessive gas to be produced inside the battery, leading to problems such as plate corrosion and water loss, and reducing the battery's lifespan. Undercharging, however, will prevent the lead sulfate on the battery plates from being completely converted. Long-term accumulation will cause sulfation of the plates. In addition, the ambient temperature during use also has a significant impact on the cycle life. High-temperature environments will accelerate the chemical reactions inside the battery, intensifying the aging and corrosion of the plates. Low-temperature environments will reduce the capacity and charging and discharging performance of batteries, increase the internal resistance of batteries, and also affect the cycle life. Generally speaking, the optimal operating temperature range for lead-acid batteries in forklifts is between 20℃ and 30℃.

Internal resistance

The concept and function of internal resistance: Internal resistance refers to the hindrance to the flow of current within the lead-acid battery of a forklift, with the unit being milliohm (mΩ). The internal resistance of a battery consists of two parts: ohmic internal resistance and polarization internal resistance. The ohmic internal resistance is mainly composed of the resistances of components such as the battery plates, electrolyte, and connecting strips. Polarization internal resistance is the resistance caused by the polarization phenomenon resulting from chemical reactions on the electrode surface during the charging and discharging process of the battery. Internal resistance is an important parameter for evaluating battery performance, as it directly affects the charging and discharging efficiency and output power of the battery. When a battery discharges, its internal resistance causes a certain voltage drop inside the battery, resulting in the voltage output from the battery to the external circuit being lower than the actual electromotive force of the battery. The greater the internal resistance, the greater the voltage drop, the smaller the power that the battery can output, and the worse the power performance of the forklift.

The relationship between internal resistance and battery health: As the battery is used and ages, its internal resistance will gradually increase. This is because during the charging and discharging process, the battery plates will undergo corrosion, the shedding of active substances and other phenomena, and the concentration and performance of the electrolyte will also change. All these will lead to an increase in the internal resistance of the battery. Therefore, by monitoring the changes in the internal resistance of the battery, the health condition of the battery can be judged to a certain extent. When the internal resistance of a battery increases to a certain extent, it indicates that the battery has experienced relatively severe aging or malfunction and requires timely maintenance or replacement. Generally speaking, when the internal resistance of the battery increases to 1.5 to 2 times its initial value, the battery's performance has significantly declined and may not be able to meet the normal working requirements of the forklift. At present, some advanced battery management systems can monitor the internal resistance of batteries in real time and issue early warnings promptly based on changes in internal resistance, reminding users to inspect and maintain the batteries.

Comprehensive consideration and practical application

When actually choosing and using lead-acid batteries for forklifts, it is necessary to comprehensively consider all the above performance parameters and make reasonable configurations in combination with the specific usage scenarios and working requirements of the forklift. At the same time, it is necessary to pay attention to the maintenance and care of the battery, strictly control the charging and discharging conditions, regularly check parameters such as the density and liquid level of the electrolyte and the internal resistance of the battery, and promptly identify and solve problems to extend the service life of the battery and improve the overall performance and operational efficiency of the forklift.