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In the industrial field, forklifts, as important handling equipment, the performance of their power source, lead-acid batteries, directly affects work efficiency. When lead-acid batteries experience deep discharge, how to effectively repair them has become a concern for many users. This article will provide you with a detailed introduction to the repair methods for deep discharge of lead-acid batteries in forklifts.
1. The Impact of Deep Discharge on Lead-Acid Batteries of Forklifts
After deep discharge, a large amount of lead sulfate crystals will form on the surface of the plates of lead-acid batteries. These crystals are large in volume and hard in texture, which will hinder the normal chemical reaction between the electrolyte and the plates, resulting in an increase in the internal resistance of the battery and a decrease in capacity. Long-term deep discharge may also cause sulfation of the plates, seriously shortening the battery's service life.
2. Preparations Before Repair
Tool preparation: Tools such as a hydrometer, multimeter, charger, distilled water, protective gloves, and goggles need to be prepared. A hydrometer is used to measure the density of the electrolyte, a multimeter detects the battery voltage, a charger charges the repaired battery, distilled water is used to replenish the moisture in the electrolyte, and protective equipment ensures operational safety.
Battery inspection: Use a multimeter to measure the total voltage of the battery pack and the voltage of each individual battery, and record the data. Under normal circumstances, the full charge voltage of a single lead-acid battery is approximately 2.1-2.2V, and the total voltage is determined by the number of battery packs connected in series. If the single-cell voltage is lower than 1.75V, it indicates that there might be a problem with the battery. Meanwhile, measure the density of the electrolyte with a hydrometer. The normal density is 1.28g/cm³ (at 25℃). If the density is too low, it may be due to water loss in the electrolyte or sulfation of the battery.
3. Repair Methods for Deep Discharge of Lead-Acid Batteries in Forklifts
Balanced charging repair method
Principle: During the use of lead-acid batteries, the charging and discharging degrees of each individual battery may be inconsistent, resulting in some batteries being undercharged. Balanced charging increases the charging voltage to ensure that each individual battery is fully charged, eliminating voltage differences between batteries and restoring the overall performance of the battery.
Operation steps: Use a dedicated forklift battery balancing charger and connect it correctly to the battery pack. Set the charger parameters. Generally, the charging voltage should be 0.5 to 1V higher than the normal charging voltage. The charging current should be selected based on the battery capacity, usually being 1/10 to 1/20 of the battery capacity. After starting charging, closely observe the voltage and current changes of the battery pack as well as the temperature of each individual battery. During the charging process, the battery will gradually heat up, but the temperature should not exceed 45℃. If the temperature is too high, charging should be paused or the charging current reduced. When the voltage of all individual batteries reaches 2.4-2.5V and remains stable, and the charging current drops to a very small level, stop charging and let the batteries stand for 1-2 hours. Then measure the voltage of each individual battery again. If the voltage difference is within 0.05V, it indicates that the equalization charging effect is good. If the difference is still significant, the above charging process can be repeated.
Deep discharge and liquid addition repair method
Principle: For batteries with sulfated plates due to long-term shallow discharge, deep discharge is carried out to enable as much lead sulfate on the plates as possible to participate in chemical reactions. Then, an appropriate amount of electrolyte is added to improve the internal chemical environment of the battery and restore its capacity.
Operation steps: First, connect the battery to the load and perform deep discharge. The motor that comes with the forklift can be used as the load to keep the forklift working until it cannot be started. At this point, the battery voltage usually drops to 10.5-11V. Open the battery's liquid filling hole cover and check the electrolyte level. If the liquid level is too low, add distilled water or special lead-acid battery replenishment liquid to bring the liquid level to the specified height (generally 10-15mm above the plates). After adding the liquid, let the battery stand for 1 to 2 hours to allow the liquid to fully penetrate. Connect the battery to the charger and start charging. The charging current can be selected at 1/10 to 1/15 of the battery capacity. The charging time depends on the battery capacity and the degree of discharge, usually taking 8 to 12 hours. During the charging process, measure the density of the electrolyte and the voltage of each individual cell every 1-2 hours. Stop charging when the density of the electrolyte recovers to 1.26-1.28g /cm³ and the voltage of each individual cell reaches 2.1-2.2V and stabilizes.
Pulse repair technology repair method
Principle: By using high-frequency pulse current to periodically impact the battery plates, the lead sulfate crystals on the surface of the plates gradually decompose under the pulse effect, restoring the active material of the plates, reducing the internal resistance of the battery, and increasing the battery capacity.
Operation steps: Purchase a dedicated lead-acid battery pulse repair device, connect it correctly to the battery pack, and make sure the positive and negative terminals are not reversed. According to the battery capacity and sulfation degree, set the parameters of the pulse repair instrument, such as pulse frequency, pulse width, and repair time, etc. Generally speaking, the pulse frequency can be set between 100 and 500Hz, the pulse width between 10 and 100μs, and the repair time is 6 to 12 hours. Start the pulse repair instrument and begin the repair process. During the repair process, observe the working status indicator light of the repair instrument to ensure the normal operation of the equipment. After the repair is completed, connect the battery to the charger and perform a full charge to activate the battery's performance.
5. Precautions during the Repair Process
Safety precautions: The electrolyte in lead-acid batteries is sulfuric acid solution, which is corrosive. During operation, it is essential to wear protective gloves and goggles to prevent the electrolyte from splashing onto the skin and eyes. In case of accidental contact with the electrolyte, rinse immediately with plenty of water and seek medical attention promptly.
Environmental requirements: The restoration work should be carried out in a well-ventilated, dry place away from fire sources and flammable materials. Because lead-acid batteries produce hydrogen during charging and repair, when hydrogen mixes with air in a certain proportion, it may explode upon encountering an open flame.
Avoid overcharging and overdischarging: During the repair charging process, strictly follow the specified charging parameters to prevent overcharging from causing the battery to heat up, bulge or even get damaged. At the same time, during the use of the repaired battery, excessive discharge should also be avoided. When the forklift's power indicator approaches low power, it should be charged in time.
5. Frequently Asked Questions
Question: After the lead-acid battery of my forklift was repaired, the battery level dropped rapidly after a period of use. What's going on?
Answer: There might be the following reasons. One is that the repair is not thorough. There are still problems such as sulfation inside the battery, which leads to the capacity not being fully restored. The above-mentioned repair methods can be adopted again for processing, or different repair methods can be tried. The second reason is that the forklift has leakage faults, such as short circuits in the circuit and controller malfunctions, which lead to abnormal battery power consumption. A comprehensive inspection of the electrical system of the forklift is required to fix the leakage problem. Thirdly, the battery itself is approaching the end of its service life, and the active material on the plates has fallen off severely. Even if it is repaired, its performance is difficult to maintain for a long time. In this case, it is recommended to consider replacing the battery with a new one.
Question: What are the requirements for the distilled water added when repairing lead-acid batteries of forklifts?
Answer: High-purity distilled water must be used. Tap water or other water containing impurities must not be used. Minerals, microorganisms and other impurities in tap water can enter the battery interior, undergo chemical reactions with the electrolyte, accelerate the corrosion of the plates and reduce the battery performance. The pH value of distilled water should be close to 7, neutral, and the lower the electrical conductivity, the better. When purchasing distilled water, choose products made by regular manufacturers and check whether the relevant indicators on the product label meet the requirements.