What are the reasons for battery bulging?

a) The vent hole on the liquid filling cover of the battery is blocked or not unblocked. During the charging process, especially at the end of charging, a large amount of explosive gas will appear inside the battery. If the vent hole on the liquid filling cover of the battery is blocked or not If it is unblocked, these gases cannot be discharged in time, so they are accumulated in the battery case, the pressure is getting higher and higher, and finally the battery is swollen. b) The battery charging current is too large or the charging time is too long. When the battery charging current is too large or the charging time is too long, the electrolyte temperature will rise rapidly and a large amount of gas will appear, which will loosen the active material on the battery plate, resulting in The battery is swollen. c) Sulfuration of the battery plate. During the high-current charging process, the cell voltage and electrolyte temperature will increase rapidly, and the bubbles will appear early and violently, which can easily cause the battery to swell. d) Continue to start the motor for too long. When starting the electric vehicle motor, the battery must supply a large current (generally 20~40A) to the motor in a short period of time. Such a large starting current will inevitably cause a violent chemical reaction inside the battery If the battery plate is accompanied by mild vulcanization, it will inevitably cause the electrolyte temperature to rise sharply and a large amount of gas will appear. Once these gases cannot be discharged in time, they may easily cause an explosion. If the starter continues to be used for too long, it will aggravate the appearance of gas and increase the possibility of battery expansion and cracking. e) Welding of the battery inner electrode plate tabs and poles to the bus bar is not firm. When the battery inner plate tabs and poles are welded to the bus bar, they must be welded firmly and integrated to meet the requirements of the battery for high-current discharge. . Otherwise, when the high current discharges, the welding place will cause sparking and ablation due to the contact point is too thin or the contact is poor, so it will cause sparks, which will ignite the explosive gas from the battery and cause the battery to explode. f) The viscosity of the electrolyte is too high. When the temperature is too low, the viscosity of the electrolyte will be high, the speed of penetrating into the pores of the electrode plate will be slow, the internal resistance will increase, and the voltage drop on the internal resistance consumed during discharge will also be large, which will cause the electrolyte temperature It rises rapidly, and a large amount of gas appears, which increases the gas pressure inside the battery. If the battery is over-discharged at this time, the temperature of the electrolyte will rise faster and more gas will appear, which will increase the gas pressure inside the battery, which will easily cause the battery to burst. In addition, the explosive gas that appears during the charging of the battery, if it encounters an open flame, will immediately cause an explosion, causing the battery to burst. Therefore, the charging room must be well ventilated, and fireworks are strictly prohibited. g) Dry electrolyte The battery will lose water after long time use, and the electrolyte will dry up. At this time, overcharging will cause the battery to bulge, and in severe cases, it will burst. If the battery loses water, you can add distilled water to the battery appropriately. The amount and operation method can be based on the battery's instruction manual. As the number of battery cycles increases, the water content gradually decreases. As a result, the battery has the following conditions: (1) The oxygen channel becomes unblocked, and the oxygen emerging from the positive electrode can easily reach the negative electrode through the channel; (2) The heat capacity decreases, and the battery The largest medium heat capacity is water. After the water is lost, the heat capacity of the battery is greatly reduced, and the heat that appears makes the temperature of the battery rise quickly; (3) The AGM separator in the battery shrinks after the loss of water, causing it to contact the negative electrode. The adhesion of the board deteriorates, the internal resistance increases, and the heat generation increases during charging and discharging. After the above process, the heat generated inside the battery can only be dissipated through the wall of the battery tank. If the heat dissipation is less than the calorific value, the temperature will rise. The rise in temperature reduces the overpotential for gas evolution of the battery and increases the amount of gas evolution. A large amount of oxygen in the positive electrode reacts on the surface of the negative electrode through the channel. Above 80°C, deformation of the battery shell will occur. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Lithium battery charging and fast charging precautions