A Brief Analysis of Common Faults of Batteries

1. Plate vulcanization

  A layer of poorly conductive, white, coarse-grained lead sulfate is produced on the battery plate. During normal charging, it cannot be completely converted into lead and lead dioxide. This phenomenon is called "lead sulfate hardening" or "sulfide" for short. Coarse-grained lead sulfate blocks the pores of the plates, making it difficult for the electrolyte to penetrate and increasing the internal resistance, thus reducing the battery capacity. Sufficient power cannot be supplied during startup, and the engine cannot start.

      The plate vulcanization has the following phenomena during charging: the voltage rises rapidly during charging, "boiling" occurs prematurely, and the electrolyte temperature quickly rises to above 40°C. When in use, the capacitance is significantly insufficient and the voltage drops rapidly. The methods to eliminate plate vulcanization are as follows:

      1. Overcharging method (applicable to slight vulcanization). Overcharge is performed continuously using the second-stage charging current of the initial charge. When the electrolyte produces a large number of bubbles and the specific gravity reaches about 1.28, it is ready for use. It is best to overcharge individual batteries with sulfide separately to remove the sulfide.

  2. Small current overcharging method (suitable for heavier vulcanization). Discharge the battery to the end voltage at a 10-hour discharge rate. Pour out the electrolyte, add distilled water, and continue charging with the second-stage charging current of the initial charge. When the specific gravity of the electrolyte rises to about 1.15, discharge again at a 10-hour discharge rate. to the termination voltage. Then use the original charging current to overcharge until the specific gravity of the electrolyte no longer rises. Adjust the specific gravity of the electrolyte to 1.28 and discharge it to the end voltage at a 10-hour discharge rate. If the battery capacity reaches 80% of the rated capacity, it can be used. If the capacity is still very small, you can repeat the above method until the battery performance returns to normal.

  3. Water treatment method (applicable to severe sulfurization). After charging the battery, discharge it at a 10-hour discharge rate until the voltage of each cell drops to 1.8v. Then pour out the electrolyte from the battery, add distilled water immediately, let it sit for 1-2 hours, and then charge it with 1/2 of the second stage charging current value until the specific gravity of the electrolyte reaches 1.12. Reduce the charging current by 1/5 and continue charging until a large number of bubbles begin to appear on the positive and negative plates and the specific gravity of the electrolyte no longer increases. Charging can be stopped. Then use 1/5 of the 10-hour discharge rate to discharge for 1.5-2 hours. Repeat several times until all plates return to normal and you can use them.

  2. Self-discharge

      The phenomenon that the battery gradually consumes power when it is not working is called self-discharge. Self-discharge cannot be completely avoided. It is generally considered normal to consume 1%-2% of its own capacity every day. If it exceeds this value, it is abnormal self-discharge.

  Reasons for self-discharge:

  1. If there are impurities in the plate material or electrolyte, a potential difference will occur between the impurities and the plate or between different impurities, forming a closed "local battery" to generate current and discharge the battery.

  2. The partition is broken, causing a local short circuit.

  3. There is electrolyte or water on the battery cover, which forms a path between the positive and negative electrodes to discharge.

  4. The active material falls off, causing the plate to short-circuit and cause discharge.

  5. When the battery is stored for a long time, the sulfuric acid in the electrolyte sinks, causing the upper part to have a smaller specific gravity and the lower part to have a larger specific gravity, causing self-discharge.

      To reduce self-discharge, the electrolyte must be kept pure, and the battery cover should always be kept clean during use to avoid short circuits. If the electrolyte is impure, the battery needs to be discharged with a current of 1/10 of the nominal capacity until the single cell voltage is 1.7 volts, then pour out the electrolyte, clean it with distilled water, and then replace it with pure electrolyte for charging.

  3. Detachment of active substances

  Reasons for detachment of active substances:

  1. The initial charging current is too large. Because the reduction of the active material of the plate starts from the grid with the best conductivity, the lead sulfate is rapidly reduced there during high-current charging, so the lead sulfate far away from the grid has no time to react chemically. Due to the larger volume of lead sulfate, It is large, so it has poor adhesion to the reduced active material inside, so it is easy to fall off from the plate.

  2. The current at the end of charging is too large. This will produce a large number of bubbles, which will violently impact the surface of the electrode plate, causing a large amount of reduced, relatively soft lead dioxide to fall off.

  3. Frequent overcharging. Although the overcharging current is not large, the lead sulfate on the plate has been reduced to lead dioxide and lead at this time, and all the charging current is used on the electrolyte. Although there are not too many bubbles generated at this time, it also affects the plate. The impact on the surface causes the active material to fall off.

  4. The discharge current is too large. At this time, the chemical reaction is intense, which will cause the plate to warp, causing the active material to fall off.

      As the active material falls off, the plates will be short-circuited, causing the battery to discharge itself. The battery must be disassembled and repaired.

  4. Single cell short circuit

      The phenomenon is that the starting ability is suddenly lost; when starting, electrolyte sprays out from the short-circuited cell. The reason is: after a single cell is short-circuited, the battery resistance increases, the voltage decreases, and it cannot supply strong current. At the same time, high temperature is generated at the short-circuit point, which causes the electrolyte to be heated rapidly and ejected.

  Common causes of failure:

  1. Active substances fall off.

  2. The electrolyte used contains impurities

  The inspection method is to use a thin wire to ignite the positive and negative electrodes of each grid. A single grid with no spark or weak spark is a short circuit. After confirmation, the first aid method can be to use thick wire to short-circuit the positive and negative poles of the short-circuited cell. However, this method can only be used in summer. In winter, a larger starting current is required. This method cannot start and needs to be sent for repair.

HZFD-200 Battery Discharge Tester