Lead-acid battery common failure mode and whether it can be repaired
1. Water loss (repairable)
During the charging process of the battery, electrolysis of water occurs, generating oxygen and hydrogen, so that the water is lost in the form of hydrogen and oxygen, so it is also called gassing. Water plays a very important role in the electrochemical system of batteries. The reduction of water quantity will reduce the ion activity of the participating reactions, leading to an increase in the internal resistance of the battery, which will intensify the home and eventually lead to a decrease in battery capacity.
The cause of this phenomenon: the battery case is broken; the safety valve is not tightly sealed; the charging voltage is too high; overcharge.
2. Sulfation (repairable)
The battery is placed on the TV, and lead sulfate is produced in the positive and negative electrodes. The positive electrode is easily converted into lead dioxide during charging due to the oxidation of oxygen. The negative electrode is different, and it is stored in long-term loss, often over-discharged, and long-term. In the presence of factors such as insufficient charging, a layer of dense and hard lead sulfate layer is gradually formed on the surface of the negative electrode, which not only greatly reduces the solubility of the electrolyte itself, but also makes it difficult to participate in the reaction, and at the same time blocks the contact channel between the electrolyte and the deep active material, thereby causing The battery capacity has dropped.
The cause of this phenomenon: long-term under-shock state; not discharged in time after discharge, long-term shelving; frequent deep discharge; safety valve sealing is not strict。
3. Plate softening (unrepairable)
The plate is a multi-void material, and has a much larger specific surface area than the plate itself。 During the repeated charge and discharge cycles of the battery, as the alternating materials of the plates alternate, the plate graduality will gradually In the appearance, the surface of the positive electrode plate is gradually softened from the beginning to become a paste, and the surface area is lowered, which causes a decrease in battery capacity。 Large current charge and discharge, over-discharge will accelerate the softening of the plate。
The cause of this phenomenon: charging and discharging is too frequent; excessive battery impurities。
4。 Grid corrosion (unrepairable)
The battery's skeleton grid oil and lead alloy is made. Although it has strong corrosion resistance, it will still cause metal corrosion when it is immersed in the acidic electrolyte for a long time, so that the board is cracked or even broken, resulting in capacity. Decline.
The cause of this phenomenon: the battery is overcharged for a long time, and the battery is used at high temperatures for a long time.
5. Short circuit (not repairable)
The positive and negative plates should be separated by a partition, but if there is slag or dendrite penetration, the positive and negative plates are connected, and the stroke is short-circuited。 A serious short circuit can cause the cell voltage to become zero。 Negatively connected substances themselves have a large electrical resistance, such as dendrites, which do not immediately cause the cell voltage to become zero, but a faster self-discharge, commonly known as a soft short circuit。
The cause of this phenomenon: battery quality problems.
6. Open circuit (not repairable)
Generally occurring in the bus bar welding and pole column welding and terminal welding stages, the form of expression is usually not a complete circuit, but a virtual welding, which is a large internal resistance in the virtual welding, resulting in a decrease in battery capacity. The battery is not soldered when soldered, and there are cracks. During use, this area will produce simple clothing, which will increase the crack speed at a faster speed.
The cause of this phenomenon: battery quality problems; severe vibration; excessive discharge current。
7. Thermal runaway (not repairable)
Definition: When the lead-acid battery is charged, both current and temperature rise and promote each other.
Conditions: Less electrolyte, charging current, especially at the end of the current。
Reason: The current is relatively large at the end of charging, the temperature of the electrolyte is increased, and the potential of hydrogen and oxygen is decreased. The formation and precipitation of gas increase the gas composite channel, and the decomposition current for decomposing water increases synchronously. Both of them promote water decomposition. accelerate. The rate at which the high temperature and high pressure gas is generated is the sum of the exhaust speed of the heavy rain safety valve and the gas recombination speed, so that the internal temperature of the battery rises rapidly.
Results: The increase in temperature and the increase in current promote each other。 The internal temperature of the battery can be as high as 120 ° C or higher, and the ABS shell (ABS melting point is 160 ° C) is softened, so that the battery expands。
Prevention: Use constant voltage current limit for charging and limit normal charging time。
8。 Innocent effect (not repairable)
A theoretical explanation for the difficulty in charging and the capacity reduction of deep lead and lead-calcium alloy positive-plate lead-acid batteries after deep discharge.
It is considered that the dense, poorly permeable film in the lead-free lead or lead-calcium alloy grid corrosion product forms a barrier layer, resulting in poor battery charging acceptance or even failure.
9. Appearance expansion and damage (not repairable)
For the battery expansion caused by improper use of transportation or damage caused by heat loss, in addition to taking precautionary measures, once it is formed, there is no way to use it. It is recommended to scrap.
10. Normal use reaches battery life (not repairable)
For normal use, the battery that has reached the battery life is basically the end of normal life. It is likely to be caused by the previous failure modes. It is of little value for the repair of such batteries. The capacity is also reduced quickly and easily after repairing in time. Caused by customer misunderstanding, it is recommended to scrap.