What's wrong with the battery bulge?
During the use of the battery, the problem of swelling and cracking, or even explosion, may occur, whether it is a new battery or an old battery. The main reasons for battery inflation are as follows:
The vent on the tank filler cap is blocked
During the charging process of the battery, especially at the end of the charging process, a large amount of explosive gas will be generated inside the battery. If the vent on the battery filler cap is blocked at this time, these gases will not be discharged in time, so they will accumulate in the battery shell, and the pressure will increase, finally the battery will bulge.When the charging current of the battery is too high or the charging time is too long, the temperature of the electrolyte will increase rapidly, and a large amount of gas will be generated, which will loosen and fall off the active substances on the battery plate, causing the battery to swell.
The battery plate is vulcanized
During the charging process of high current, the cell voltage and electrolyte temperature of the battery with vulcanized plates will rise rapidly, and the bubbles will be generated early and violently, which will easily cause the battery to swell.The motor is started continuously for too long
When starting the electric vehicle motor, the battery shall provide a large current (generally 20~40A) to the motor in a very short time. Such a large starting current will inevitably cause severe chemical reaction in the battery. If the battery plate is accompanied by slight sulfurization, it will inevitably lead to a sudden rise in the temperature of electrolyte and generate a large amount of gas. Once these gases cannot be discharged in time, they will easily cause explosion. If the starter is used continuously for a long time, it will aggravate the generation of gas and increase the possibility of battery cracking.The lug and pole of the battery inner plate are not firmly welded with the bus bar. When the lug and pole of the battery inner plate are welded with the bus bar, they must be firmly welded and integrated to meet the needs of the battery during heavy current discharge. Otherwise, in case of large current discharge, the welding point will be ignited and ablated due to too thin contact point or poor contact, which will cause sparks and ignite the explosive gas generated by the battery, causing the explosion of the battery.
The viscosity of electrolyte is too high
When the temperature is too low, the electrolyte viscosity is high, the speed of penetration into the plate pores is slow, the internal resistance increases, and the voltage drop consumed in the internal resistance during discharge is also large, which will cause the electrolyte temperature to rise rapidly, produce a lot of gas, and increase the gas pressure inside the battery. If the battery is discharged excessively at this time, the temperature of electrolyte will rise faster, and more gas will be generated, which will increase the gas pressure inside the battery and easily lead to battery expansion and cracking. In addition, the explosive gas generated during the charging process of the battery will also cause an explosion immediately in case of open fire, causing the battery to expand and crack. Therefore, the charging room must be well ventilated and fireworks are strictly prohibited.Electrolyte dries up
After the battery is used for a long time, it will lose water, which will cause the electrolyte to dry up. At this time, overcharge will cause the battery to bulge, and even burst in serious cases. In case of water loss of the battery, distilled water can be added properly to the battery. The amount of added water and the operation method can be carried out according to the battery operation manual.
With the increase of battery cycles, the water content gradually decreases. As a result, the following conditions occur in the battery:
The oxygen "channel" becomes smooth, and the oxygen generated by the positive pole can easily reach the negative pole through the "channel";
The heat capacity is reduced. Water has the largest heat capacity in the battery. After water loss, the heat capacity of the battery is greatly reduced, and the heat generated makes the temperature of the battery rise quickly;
As the AGM separator in the battery shrinks after water loss, the adhesion between it and the negative plate becomes poor, the internal resistance increases, and the heat generated during charging and discharging increases. After the above process, the heat generated inside the battery can only be dissipated through the wall of the battery box. If the heat dissipation is less than the calorific value, the temperature rises. When the temperature rises, the overpotential of battery gas evolution decreases, and the amount of gas evolution increases. A large amount of oxygen from the positive electrode reacts on the negative electrode surface through the "channel", generating a large amount of heat, which makes the temperature rise rapidly, forming a vicious cycle, namely the so-called "thermal runaway". When the final temperature reaches above 80 ℃, the battery shell is deformed.
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