Use of lead-acid batteries in construction machinery

1. Selection of electrolyte

(1) Capacity

During the operation of construction machinery, the battery is working, and it is normal for the electrolyte to be consumed continuously. Keeping track of the electrolyte level is a basic work to ensure the normal operation of the battery. Under normal circumstances, distilled water should be added once every half a month. When the battery electrolyte level drops quickly, the regulator limit voltage should be checked to see if it is too high. If it is too high, the battery will often be in an overcharged state, causing the water in the electrolyte to evaporate too quickly. At this time, the limit voltage should be adjusted in time. When the battery electrolyte level is lower than the specified value, distilled water should be added; remember not to add electrolyte, let alone concentrated sulfuric acid. Only when the battery is overturned due to a malfunction and the original electrolyte is lost, can the electrolyte be added, and its density must be the same as the density of the original electrolyte in the battery.

When adding electrolyte to the battery, the height of the liquid level in each cell must be 10~15mm higher than the plate. You can use a glass tube with an inner diameter of 3~5mm for testing, that is, insert one end of the glass tube into the battery, place it vertically on the protective plate, and then block the upper end with your fingers to remove the glass tube. The height of the liquid level in the tube is the height of the electrolyte level above the plate; you can also use clean bamboo or wood chips to detect, and it is absolutely forbidden to use metal wire to detect. The monitoring period is: 10~15 days in winter and 5~7 days in summer.

When electrolyte is added to a new battery, the internal material will absorb some electrolyte, and the electrolyte level and density will decrease after a period of time. Therefore, electrolyte with circular density should also be added to the specified level.

(2) Density

Accurately measuring the electrolyte density of a battery is an important basis for analyzing its actual capacity. The electrolyte density increases with charging and decreases with discharging. It is an important indicator of the technical status of the battery. Tests have shown that a decrease in electrolyte density of 0.01g/cm3 is equivalent to a 5% power consumption of the battery. During use, the battery must maintain a charging rate of 75%, that is, when the electrolyte density drops by 0.05g/cm3, the battery must be charged.

Generally speaking, the electrolyte density in the range of 1.27~1.29g/cm3 is the best parameter for obtaining sufficient capacity. If the electrolyte density is small, the energy of the plate will not be fully released, and the electrolyte will be close to water, which is not conducive to the maximum function of the battery. If the electrolyte density is too high, although it has certain benefits for the capacity of the battery, it will aggravate the corrosion of the plate and affect the service life of the battery. Due to different battery use conditions, different electrolyte densities need to be selected.

2. Battery charging and discharging

(1) Initial charging of a new battery

When ordinary lead-acid batteries are used for the first time, they need to be charged. The quality of the charge directly affects the capacity and life of the battery, so it must be done carefully. The method is as follows:

① Inspection before charging. Before the initial charging, the battery and its accessories should be thoroughly inspected to see if the container is cracked or if any accessories are missing, and they should be cleaned.

② Fill the electrolyte. Inject the electrolyte of the specified density according to the instructions, and use a 0~3V DC voltage meter to check whether the medium single-cell battery has reverse polarity.

③Charge. Connect the charger and battery correctly. The charging process is divided into two stages. The charging current of the first stage is about 1/4~1/6 of the rated capacity C20. Charge until bubbles are released from the electrolyte and the single cell voltage reaches 2.4V. Reduce the current by half and enter the second stage. Charge until bubbles emerge from the electrolyte and the density and voltage remain stable for 2~3 hours. The total charging time is about 60~70 hours. The electrolyte temperature must be measured frequently during the charging process. When the temperature exceeds 40°C, the charging current should be halved, but the charging time should be extended. When the temperature exceeds 45°C, the charging should be stopped immediately and the charging should be resumed when the temperature drops below 40°C. During the initial charging process, except for special circumstances, it is not allowed to be interrupted within 20 hours.

④ Adjust the electrolyte density and liquid level. When the battery is close to being fully charged, the electrolyte density and liquid level must be adjusted. When the density is higher than the specified value, a portion of the electrolyte should be properly removed and a certain amount of distilled water should be added. Otherwise, an electrolyte with a density of 1.40g/cm3 should be added to make the liquid level reach the specified value, and then charge for another 30 minutes. If it still does not meet the requirements, it should be adjusted several times until it is adjusted properly.

If a new battery does not reach the rated capacity after the first charge, it should be charged and discharged in cycles. That is, discharge at a 20h discharge rate (i.e., a current of 1/20 of the rated capacity) until the single cell voltage drops to 1.75V, and then recharge with normal current. Generally, after three charge and discharge cycles, the battery capacity can reach 100%.

(2) Normal charging of the battery

The battery is normally charged under the following conditions:

① The battery on the machine shows low power.

② The battery is discharged at a low current for a long time.

③The battery has been left indoors for more than one month.

④ The electrolyte consumption is large or the water evaporates too much, so a large amount of distilled water is added.

⑤ After the battery has been overhauled, the plates are exposed to the air for a long time.

⑥ The battery discharge exceeds 25% in winter and exceeds 50% in summer.

(3)Battery balanced charging

When there are differences in the terminal voltage, electrolyte density, capacity, etc. of each cell of the battery, the balanced charging method can be used to eliminate the differences. First, charge with the normal charging method, and after the terminal voltage of the battery stabilizes, stop charging for 1 hour, and then charge with 1/20 current of C20, charge for 2 hours, and stop for 1 hour. Repeat 3 times until bubbles are seen to be generated violently at the beginning of charging of each cell of the battery.