Maintenance-free liquid battery common repair problems and solutions

1. The maintenance-free battery (hereinafter referred to as the battery) basically does not generate air bubbles during charging, and can be in a sealed state, eliminating the need for maintenance work such as adding acid. However, it is impossible for the battery to not produce gas at all during the charging and discharging process. In order to release the gas, the battery cannot be completely sealed. Pry off the plastic cover on the upper part 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, resulting in a decrease in battery capacity. In severe cases, the battery will dry out and cannot be charged and discharged. For this type of battery, most of the capacity of the battery can be restored by simply adding distilled or purified water to the battery and performing several charge-discharge cycles. Example: a 12V7.2Ah battery, which is not used for a long time, discharges after charging to 14V, and the short-circuit current is only more than 300 mA. Open the top cover to check, the liquid is nearly dry, inject distilled water and perform charge-discharge cycles twice, the capacity is restored 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 complete discharge, the specific gravity at 15°C drops to 1.11. Generally, the specific gravity rises during charging, and the specific gravity after fully charged is 1.25~1.26 in summer and 1.27~1.28 in winter. Because the battery is in a sealed state, when using it, you can only judge whether it has been fully charged or discharged according to the voltage of the battery. 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 semi-discharged state for a long time, the battery will be vulcanized. The vulcanized battery cannot be eliminated by adding distilled water and conventional charging. Only when the concentration of sulfuric acid in the electrolyte is charged, the vulcanization can be eliminated.

If the vulcanization of the battery is not serious and the capacity does not decrease much, the battery can be charged 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), use a syringe to draw out the electrolyte in the battery, and then inject distilled water to dilute the electrolyte. After charging for 1 to 2 hours, draw out the electrolyte, inject distilled water, and repeat the above operations until the specific gravity of the extracted electrolyte no longer increases significantly (generally 2 to 3 times). At this time, try to draw out the reverse electrolyte, and then inject sulfuric acid with a specific gravity of 1.25~1.28 according to the ambient temperature. 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 meet the standard. Note that the electrolyte injected into the battery should not be too much. After the sponge-like material in the battery is fully absorbed with the electrolyte, the excess electrolyte is drawn out, and the repair work is completed. Example: A Sony BP60 3Ah battery was used as a power source for 3/4-inch cameras in the 1980s, and the battery was severely vulcanized. After repairing with the above method, the capacity is restored to 2.2Ah.

3. Some battery connection bridges or the external lead wires of the battery 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 by finding the broken part. Using the above method of plated copper coins, use a multimeter to find the battery with abnormal voltage or small output current, and the breaking point is on the battery. After finding it, open a hole in the plastic cover at the break. The size of the hole should be enough to allow a soldering iron to penetrate into the break for welding, but it should not be too large. After welding, check that the connection is normal, close the opened 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 with low voltage and high current. If the active material falls off (indicated by the brown material in the withdrawn electrolyte), it means that the battery life has ended, and this type of battery does not need to be repaired. However, if only one or two of the batteries have expired, these two batteries can be short-circuited, and the remaining batteries can still be used as lower-voltage batteries.