What are the methods for repairing lead-acid batteries?
1. The maintenance-free battery (hereinafter referred to as the battery) basically does not produce air bubbles when charging, and can be sealed in a sealed state, eliminating the need for maintenance work such as adding acid. However, it is impossible for the battery to not generate gas at all during the charging and discharging process. In order to release the gas, the battery cannot be completely sealed. Pry open the plastic cover on the top of the battery, you can see that each small battery has a filling hole covered with a rubber cap, and the water in the battery can evaporate through the rubber cap. Even if the battery is not in use, the water will evaporate, causing the battery capacity to decrease. In severe cases, the battery will dry out and cannot be charged and discharged. For this kind of battery, as long as you add distilled water or purified water to the battery and perform several charge-discharge cycles, most of the battery's capacity can be restored. For example: a 12V7.2Ah battery, the use time is not long, after charging to 14V and then discharging, the short-circuit current is only more than 300 milliamperes. Open the upper cover and check that the liquid is almost dry. Fill in distilled water and perform charge and discharge cycles twice. The capacity has recovered to 84% and it can work normally.
2. When the battery is discharged, the concentration of sulfuric acid and the specific gravity of the electrolyte decrease. After the battery is completely discharged, the specific gravity at 15°C drops to 1.11. In general, the specific gravity increases during charging, and the specific gravity after fully charged in summer is 1.25 to 1.26, and in winter it is 1.27 to 1.28. Because the battery is in a sealed state, you can only judge whether it has been charged or discharged according to the voltage of the battery during use. When the 6V and 12V batteries are fully charged, the voltages are 6.8V-7V and 13.6V-14V, respectively. When fully discharged, the voltages of the 6V and 12V batteries are 5.3V and 10.6V, respectively. If the battery is over-discharged or in a half-discharged state for a long time, the battery will be vulcanized. The vulcanized battery cannot be eliminated by adding distilled water and conventional charging methods. Only when the electrolyte concentration of sulfuric acid is low can the vulcanization be eliminated.
If the vulcanization of the battery is not serious and the capacity drops little, you can charge the battery for a long time with a small current (0.05A or less). If the vulcanization of the battery is serious, it can be charged to the highest voltage (6V battery is charged to 7V, 12V battery is charged to 14V), the electrolyte in the battery is drawn out with a syringe, and then distilled water is injected to dilute the electrolyte. After charging for 1 to 2 hours, draw out the electrolyte, inject distilled water, and repeat the above operation until the specific gravity of the extracted electrolyte no longer rises significantly (usually 2~3 times are sufficient). At this time, try to draw out the reverse electrolyte, and then inject sulfuric acid with a specific gravity of 1.25 to 1.28 according to the ambient temperature, and then fully charge the battery after it is discharged. Check the specific gravity of the electrolyte. If the specific gravity is small, the electrolyte can be drawn out again and injected with sulfuric acid to make the specific gravity of the electrolyte reach the standard. Note that the amount of electrolyte injected into the battery should not be too much. After the sponge-like substance in the battery is filled with the electrolyte, the excess electrolyte is drawn out, and the repair work is completed. Example: A Sony BP603Ah battery was used as a power supply for 3/4-inch video cameras in the 1980s, and the battery was severely vulcanized. After repairing with the above method, the capacity was restored to 2.2Ah.
3. Some battery connection bridges or battery leads to the outside are broken (in most cases, the positive and negative lead wires are broken), and the battery cannot work. A deformed battery can only be repaired if the broken part is found. Using the above method of inserting copper-plated coins, use a multimeter to find a battery with an abnormal voltage or a small output current, and the breaking point is on the battery. After finding it, open a hole in the plastic cover at the fracture. The size of the hole is such that the soldering iron can be inserted into the fracture for welding. It should not be too large. After welding, check that the connection is normal, seal the open hole with plastic or epoxy resin, and then use the above method to revive, the battery can be put into work again.
4. If there is a short-circuit fault inside the battery, the short-circuit point can be burned out with low-voltage and high-current. If the active material falls off (shown as a brown substance in the extracted electrolyte), it means that the battery life is over and this type of battery does not need to be repaired. But if only one or two of the batteries have reached the end of their life, the two batteries can be short-circuited, and the remaining batteries can still be used as lower-voltage batteries.
Two points of explanation
1. Impurities (especially iron ions) are very harmful to the battery, which will cause the battery to self-discharge and shorten its life. Therefore, pay attention to purity when injecting sulfuric acid and water.
2. The hydrometer is an indispensable tool for repairing the battery, but the commercially available hydrometer requires more electrolyte for measurement and is difficult to use. The author made a miniature simple hydrometer with the pen core of the gel pen and the cap of the ballpoint pen: put the hydrometer in pure water and record the position of the hydrometer on the water surface. This is the scale position of the specific gravity of 1.00; then the specific gravity Put the meter into a sulfuric acid solution with a known concentration (dilute sulfuric acid is available at battery stores or repair shops, but ask them to accurately measure the specific gravity of sulfuric acid, such as 1.28). Note the hydrometer at the liquid level; The length of the specific gravity of 1.00 to 1.28 is engraved on the paper, and the scale between 1.00 to 1.28 is divided into 28 equal parts to complete the hydrometer.