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Introduction

In modern logistics and industrial production, forklifts, as key material handling equipment, their efficient and stable operation is of vital importance. Lead-acid batteries, as one of the mainstream power sources for forklifts, are widely used in various types of forklifts. However, the performance of lead-acid batteries is extremely sensitive to temperature. Different temperature environments can significantly affect their key performance indicators such as charging and discharging efficiency, capacity, and lifespan, thereby influencing the normal operation and operating costs of forklifts. An in-depth exploration of the performance variation laws of forklift lead-acid batteries under different temperature environments and the proposal of targeted countermeasures are of great practical significance for ensuring the operational efficiency of forklifts, reducing operating costs and prolonging the service life of batteries.

Performance changes of lead-acid batteries in low-temperature environments

The charging and discharging capacity has decreased significantly

When the ambient temperature drops, the charging and discharging capacity of lead-acid batteries will weaken sharply. Studies show that under low-temperature conditions, the charging capacity may only reach 60% - 70% of that at normal temperature, while the discharging capacity drops to 50% - 60%. This is mainly attributed to the fact that low temperatures significantly increase the viscosity of the electrolyte, slow down the diffusion rate of ions in the electrolyte, and significantly increase the resistance to chemical reactions, which seriously hinders the electrochemical reaction process inside the battery and thus greatly limits the battery's charge and discharge cycle capacity. Generally speaking, the optimal charging and discharging temperature range for lead-acid batteries is 25±5℃. When the temperature drops below 15℃, the battery capacity begins to decline significantly. Moreover, for every 1℃ decrease in temperature, the available capacity of the battery reduces by approximately 0.8%. For instance, in the cold winter outdoors, the lead-acid batteries equipped on forklifts often encounter difficulties in charging. Even after being fully charged, their usage time is significantly reduced, failing to meet the normal operation duration requirements.

The internal resistance of the battery increases

Low temperatures can also cause a significant increase in the internal resistance of batteries. On the one hand, the viscosity of the sulfuric acid solution increases at low temperatures, and the solution resistance increases significantly. On the other hand, the electrode polarization phenomenon intensifies in a low-temperature environment, further increasing the internal resistance of the battery. According to relevant data, when the ambient temperature drops below 0℃, for every 10℃ decrease in temperature, the internal resistance of the battery increases by approximately 15%. The increase in internal resistance leads to an increase in energy loss during the charging and discharging process of the battery, a decrease in charging efficiency, a drop in output voltage during discharging, which affects the normal operation of the forklift motor, resulting in weakened forklift power, difficult starting, and slower running speed, seriously affecting the operational performance and efficiency of the forklift.

Corrosion of the plate grid and the decrease in the utilization rate of active substances

In low-temperature environments, the grid plates of lead-acid batteries are prone to corrosion. This kind of corrosion will cause the plates to deform and the gaps between them to increase, which not only reduces the battery's service life but also lowers its discharge performance and endurance. Meanwhile, at low temperatures, the utilization rate of the active material on the negative electrode is extremely low. The lead on the negative electrode plate is prone to form small-sized grains, and the small holes on the plate are easily frozen and blocked, reducing the contact area between the active material and the electrolyte, which significantly lowers the utilization rate of the active material. What is more serious is that a dense lead sulfate layer may form on the surface of the plates, hindering the continuation of the electrochemical reaction and causing the battery to prematurely stop discharging, which is known as the "passivation" phenomenon.

Risk of electrolyte freezing

At extremely low temperatures, the electrolyte of lead-acid batteries is at risk of freezing. The electrolyte is composed of water and sulfuric acid. Low temperature will increase the freezing point of the electrolyte. When the battery power is low, the sulfuric acid content in the electrolyte relatively decreases, the proportion of water increases, the freezing point further rises, and the possibility of freezing significantly increases. Once the electrolyte freezes, the volume expansion may cause the battery casing to crack and the plates to be damaged, resulting in irreversible and severe damage to the battery and direct scrapping. For instance, when working in outdoor warehouses in extremely cold regions, if the protective measures for the lead-acid batteries of forklifts are not in place, it is very likely that the electrolyte will freeze.

The performance changes of lead-acid batteries in high-temperature environments

The self-discharge rate of the battery increases

High-temperature environments will accelerate the self-discharge process of lead-acid batteries. Self-discharge of a battery refers to the phenomenon where the battery's internal electrochemical reactions occur spontaneously without being connected to an external load, resulting in the gradual loss of electrical energy. Under high-temperature conditions, the chemical reaction rate inside the battery accelerates, and the self-discharge rate significantly increases. Generally speaking, for every 10℃ increase in ambient temperature, the self-discharge rate of batteries approximately doubles. This means that in high-temperature environments, even if the forklift is not used for a long time, the battery power will be drained rapidly. When the forklift needs to be used, there may be a situation where the battery power is insufficient and it cannot be started, affecting the timeliness of operations.

The corrosion of the positive plate intensifies and water loss accelerates

High temperatures will significantly accelerate the corrosion process of the positive plates of lead-acid batteries. The lead dioxide on the positive plate undergoes a more intense chemical reaction with sulfuric acid at high temperatures, accelerating the corrosion rate of the plates and gradually damaging the plate structure, thereby shortening the service life of the battery. Meanwhile, high temperature accelerates the evaporation of water in the electrolyte, causing severe water loss in the electrolyte. The reduction of moisture will lead to an increase in the concentration of the electrolyte, further accelerating the corrosion of the positive plate and forming a vicious cycle. In addition, water loss from the electrolyte may also cause the battery to dry up internally, affecting the normal progress of electrochemical reactions and reducing battery performance.

Risk of thermal runaway

In high-temperature environments, if the battery does not dissipate heat well, there is also a risk of thermal runaway. When the rate at which heat is generated inside a battery exceeds the rate at which it dissipates heat to the environment, the battery temperature will continue to rise, further accelerating the rate of electrochemical reactions and resulting in more heat generation, thus forming a vicious cycle. Once thermal runaway occurs, the battery temperature may rise sharply, causing serious safety accidents such as smoke, fire and even explosion, posing a great threat to the safety of personnel and equipment. For instance, during the high-temperature period of summer, if forklifts operate continuously at high intensity for a long time and the battery cooling system malfunctions, it is prone to cause thermal runaway.

The battery capacity rose initially but declined more rapidly in the later stage

In the early stage of high temperature, due to the accelerated rate of electrochemical reactions, the capacity of lead-acid batteries may experience a brief increase. However, as time goes by, various damages caused by high temperatures to batteries gradually accumulate, such as plate corrosion, water loss, and active material shedding, which can lead to a rapid decline in battery capacity, and the rate of decline is much faster than that in a normal temperature environment. Batteries that are exposed to high-temperature environments for a long time will have their overall service life significantly shortened. Frequent battery replacement not only increases operating costs but also affects the continuity and stability of forklift operations.

The interaction between the working environment of forklifts and the characteristics of lead-acid batteries

The influence of forklift operations in different indoor and outdoor locations

Forklifts often need to shuttle between different indoor and outdoor locations for operations. The indoor environment is relatively stable, and the temperature is regulated by air conditioners and other equipment, so the performance of lead-acid batteries is relatively stable. However, outdoors, especially under extreme temperature conditions, the battery performance will be significantly affected. In the cold winter outdoors, low temperatures lead to a decline in battery performance and a reduction in the operational efficiency of forklifts. In the hot summer outdoors, high temperatures will accelerate the aging and performance decline of batteries. In addition, environmental factors such as humidity and dust both indoors and outdoors can also affect batteries. A humid environment may cause corrosion of the battery casing and electrodes, and excessive dust may affect battery heat dissipation, further interfering with battery performance.

The power demand and battery power supply capacity of forklifts during operation

During the operation of a forklift, it needs to frequently perform operations such as starting, accelerating, and transporting heavy objects, which requires a large amount of power and changes frequently. In low-temperature environments, the power supply capacity of lead-acid batteries decreases, making it difficult to meet the instantaneous high power demands of forklifts. This results in slow starting, weak acceleration, and insufficient power when handling heavy objects. In high-temperature environments, although the battery may provide relatively high power initially, as its performance deteriorates rapidly, unstable power supply will gradually occur, affecting the normal operation of forklifts. In severe cases, insufficient power supply may even lead to equipment failure, damage to goods or cause safety accidents.

The impact of frequent starts and stops of forklift operations on battery life

The frequent start-stop characteristics of forklift operations have a significant impact on the lifespan of lead-acid batteries. Each time the battery starts up, it needs to provide a large current instantaneously, which will accelerate the wear of the battery plates and the shedding of active materials. In a low-temperature environment, the internal resistance of the battery increases, and the current impact during startup causes more severe damage to the battery. In a high-temperature environment, the heat generated by frequent starts and stops accumulates, accelerating the chemical reactions inside the battery and also shortening its lifespan. Frequent and long-term start-stop operations will cause the battery to enter the decline period prematurely, reduce the overall cycle life of the battery, and increase the operating costs of the enterprise.

Measures to deal with different temperature environments

Coping strategies for low-temperature environments

Preheating and insulation measures: Before charging, preheat the lead-acid battery. You can use a dedicated battery preheating device, such as a heating pad or a hot air gun, to heat the battery and raise its temperature to a suitable range for charging. Generally, it is recommended to heat the battery to above 5℃ to enhance its charging acceptance capacity and enable it to charge more electricity in winter. During the operation of forklifts, insulation measures can be taken for the battery, such as installing an insulation cover for the battery, wrapping the battery with heat insulation materials, reducing the loss of battery heat, maintaining a stable internal temperature of the battery, and slowing down the rate of battery performance decline.

Optimize charging strategy: In winter when the temperature is low, appropriately extend the charging time. Generally, it is recommended to charge for 8 to 10 hours, or perform a float charge of about 2 hours after the charger turns green. However, it should be noted that the total charging time should not exceed 12 hours to prevent overcharging from damaging the battery. At the same time, choose a charger suitable for low-temperature environments. Such chargers can automatically adjust charging parameters according to the temperature, such as increasing the charging voltage and reducing the charging current, to avoid undercharging or overcharging caused by low temperatures, ensuring that the battery can be fully charged and is safe and reliable.

Use cold-resistant batteries or additives: Select lead-acid batteries with good cold resistance. These batteries have undergone special treatment on the electrolyte, plate grid, etc. during the design and manufacturing process, enabling them to maintain good fluidity and corrosion resistance at low temperatures. For instance, some batteries adopt special lead paste formulas and grid alloys, which can effectively enhance the performance of the batteries in low-temperature environments. In addition, an appropriate amount of cold-resistant additives, such as ethylene glycol, can also be added to the electrolyte to lower its freezing point, reduce the risk of electrolyte freezing, and improve the battery's performance at low temperatures.

Regular maintenance and inspection: Conduct comprehensive maintenance and inspection of lead-acid batteries on a regular basis, including checking the concentration of the electrolyte and the height of the liquid level to ensure that the electrolyte is at a normal level. If the electrolyte is found to be insufficient, distilled water should be replenished in time. However, it is important to do so when the battery is fully charged and the ambient temperature is suitable to ensure that the electrolyte is well mixed and prevent the electrolyte from freezing due to improper water addition. At the same time, check whether the battery terminals are loose or corroded, and promptly clean the oxide on the surface of the terminals to ensure a firm connection, reduce resistance, and guarantee the normal charging and discharging of the battery. In addition, regularly perform deep discharge and charge maintenance on the battery to activate the active substances inside the battery and restore part of its capacity.

Coping strategies for high-temperature environments

Heat dissipation and cooling measures: Equip the lead-acid batteries of forklifts with effective heat dissipation devices, such as installing fans in the battery compartment to accelerate air flow through forced ventilation and remove the heat generated by the batteries. When operating in high-temperature environments, the intensity and frequency of forklift operations can be appropriately reduced to prevent excessive heat generated by the battery's continuous high-current discharge for a long time. If conditions permit, park the forklift in a cool and well-ventilated area to reduce the impact of direct sunlight on the battery. For some large forklifts or those that operate for long periods in high-temperature environments, it is also advisable to install an air conditioning refrigeration system to cool down the battery, ensuring that the battery's working temperature remains within an appropriate range. Generally, it is recommended that the battery's working temperature does not exceed 40℃.

Control charging time and temperature: In high-temperature environments, strictly control the charging time of the battery to avoid overcharging. High temperatures can accelerate the self-discharge and chemical reactions of batteries, and overcharging can cause the battery to heat up more intensely, further damaging the battery. When the battery is fully charged, charging should be stopped in time. At the same time, monitor the battery temperature during the charging process. If the temperature is too high, you can pause the charging and resume it when the battery temperature drops. The battery temperature can be monitored in real time by a temperature sensor, and the charging parameters can be automatically adjusted through the charging control system to ensure a safe and efficient charging process.

Regular water replenishment and maintenance: Regularly check the liquid level of the electrolyte. As the electrolyte loses water rapidly at high temperatures, if the liquid level is found to be too low, distilled water should be replenished in a timely manner. However, it should be noted that the replenishment should not be too fast to avoid excessive changes in the electrolyte concentration, which may affect the battery performance. At the same time, regularly inspect the battery to check if the positive plates are corroded and if the active substances have fallen off, etc., to promptly identify and address potential battery issues. Clean the battery casing to remove surface dust and dirt, ensuring good heat dissipation of the battery and preventing excessive battery temperature due to dust accumulation affecting heat dissipation.

Adjust the battery usage method: During high-temperature periods, try to avoid prolonged and high-intensity continuous operations by forklifts. Arrange the operation time reasonably and leave sufficient time for the battery to dissipate heat. If the forklift is equipped with multiple sets of batteries, a rotational use method can be adopted to allow the batteries sufficient cooling and recovery time, reducing the damage caused by high temperatures and continuous use to the batteries. In addition, in high-temperature environments, appropriately reducing the traveling speed and load of the forklift and decreasing the output power demand of the battery can help lower battery heat generation and extend the battery's service life.

Conclusion

Different temperature environments have complex and significant influences on the performance of forklift lead-acid batteries. In a low-temperature environment, the battery's charging and discharging capacity decreases, its internal resistance increases, the plate grid corrodes, and there is a risk of the electrolyte freezing. In high-temperature environments, the self-discharge rate of batteries increases, the corrosion of positive plates intensifies, there is a risk of thermal runaway, and capacity decline accelerates. The working environment and operational characteristics of forklifts further interact with battery performance, influencing the actual usage effect and lifespan of the batteries. By taking targeted measures such as preheating and insulation, heat dissipation and cooling, optimizing charging strategies, regular maintenance and inspection, as well as reasonable selection and use of batteries, the performance of lead-acid batteries in forklifts under different temperature environments can be effectively improved, the service life of the batteries can be prolonged, the efficient, stable and safe operation of forklifts can be ensured, and the operating costs of enterprises can be reduced. Provide reliable support for the smooth operation of logistics and industrial production activities. In the future, with the continuous development of technology, it is expected that forklift batteries with better performance and stronger temperature adaptability can be developed to meet the growing demands of industrial applications.