Perhaps many people will find such a situation, when the electric vehicle battery is charging, you will find that the battery case is very hot. However, many people think this is normal. The battery is allowed to generate a small amount of heat, whether in use or during charging, but it is not allowed to generate abnormal heat. When you touch the battery case with your hands, you can obviously feel very hot, which means that the battery is abnormally hot. In this case, we must not ignore it, because the abnormal heat of the battery is very harmful.
The heat first causes the electrolyte water to evaporate and gradually dry up, and then decreases the charging efficiency, deformation of the plates, increased internal resistance, accelerated oxidation of mechanical parts, burned out plates or separators, and finally manifests in reduced battery capacity and shortened life. Therefore, if you find that the battery is abnormally hot during use or charging, you must not ignore it.
There are two main types of battery heating:
First, it is the heat generated when the battery is discharged, that is, the battery is abnormally heated during use;
2. The battery is hot during charging. The cause of abnormal battery heating is also different in different situations.
1. Cause of battery discharge heating: the discharge is too fast, the battery capacity may be small, and the discharge current exceeds 0.5C for a long time. It is emphasized here that although the battery consumes a certain amount of power after short-distance driving, the battery has a recovery process after stationary, and the electrochemical process of the plate continues, so the voltage will rise, but it does not mean that the capacity will rise. In contrast, during long-distance driving without stopping on the road, the electrification of the plates and the consumption of electrical energy occur simultaneously. There are three situations:
① When the rated voltage of the motor is low, the battery capacity is small, the operating current is too large, the voltage will decrease sharply, and the capacity will be exhausted quickly, which is the most disadvantageous for the battery.
② The electrochemical reaction speed of the battery can only maintain the driving. The battery has no chance of recovery and respite. It is often charged and discharged for the whole cycle, and it will be over-consumed if you pay little attention. When encountering windward uphill, the power consumption is very large, forcing the battery plate to respond sharply. The high heat of the battery case will damage the battery and shorten the life, indicating that the capacity is not surplus.
It is ideal that the electrochemical reaction speed of the battery can calmly supply enough electrical energy. The battery case has no abnormal heat, indicating that the battery capacity is surplus.
Of the three cases, only the last one is ideal for long-distance driving. It should be noted that the battery case is obviously hot, and the internal battery itself is even hotter.
2. Reasons for the heat of battery charging: During the charging process of the battery, part of the electric energy is converted into chemical energy, and part of the electric energy is also converted into thermal energy and other energy. It is normal for the rechargeable battery to heat up, but when the temperature is high, you should check whether the charging current is too large or a short circuit occurs inside the battery.
The relationship between the amount of heat generated and the amount of electrolyte is small. For example, when the sealed battery has a small amount of electrolyte, the internal resistance increases, which will also cause the battery to heat up and the terminal voltage when charging is high. Battery aging, dry electrolyte, and internal short circuits can also cause heat. The charger cannot be constant voltage in the late stage of charging, so that the battery voltage exceeds the allowable value, the temperature will rise, it will swell severely, and the end of life.
During use, try not to place it horizontally or upside down, to prevent a large amount of gas generated in the battery from being discharged from the air release valve, especially when charging, otherwise it may cause the casing to burst.
In short, if the battery is abnormally hot, it must not be ignored, and you should go to a professional maintenance shop for battery maintenance as soon as possible.