Analysis of common damages of electric vehicle batteries

Date:Apr 11, 2019

First of all, we have to clarify that the several damages we have mentioned here are to exclude the external damage of the battery (such as: battery bulging, battery leakage, pole break, etc.), then we use more reasonable The statement should be: several cases of battery failure.

Battery failure: The battery is not working or the battery is seriously degraded.

The most common causes of battery failure:

1. Battery dehydration

2. Battery curing

3. Battery positive plate softening

4. Battery thermal runaway

5. Battery short circuit

6. Battery open circuit

In particular, it is important to note that in the various failures of the battery, it can only be said that one of the reasons is dominant, because any of the above six cases will bring out other failure conditions. For example, it is like a person having a cold, a stuffy nose, a runny, a cough, a headache, etc., but the cough is the most powerful. Repairing the battery is like giving a doctor.

A detailed analysis of the six conditions that led to battery failure:

1. Battery dehydration

The battery is hot when charging. At this time, although the battery bulging phenomenon has not occurred, the water loss is already very serious. If it is not repaired or repaired, it will cause the battery to be vulcanized, which will lead to the thermal runaway of the battery and the vicious battery failure of the positive plate softening, and may even cause the battery to be scrapped.

What causes the battery to lose water:

Battery dehydration is the most common and most common failure of battery failure. At the same time, battery dehydration is the source of most battery failure.

So how is the water in the battery lost?

In the charging process, in order to meet the 6-8 hours of full charge requirements, the charger has to set the charging voltage higher, this higher voltage far exceeds the battery's gassing voltage. A part of the water is discharged by the safety method during the high-voltage charging process (discharged by gas, mainly hydrogen and oxygen, which are the main gases of water).

After the water is dehydrated, the specific gravity of the acid in the electrolyte gradually increases, which causes the vulcanization phenomenon of the battery to increase, and the capacity of the battery is gradually reduced. The vulcanization of the battery increases the water loss of the battery, and the water loss increases the vulcanization. As a result of the vicious cycle, the capacity of the battery is lost, and the battery working capacity is drastically reduced or even not working.

2. Battery curing

First, we should know what is battery vulcanization. A layer of white hard crystals is formed on the surface of the internal negative plate of the battery, and it can not be peeled off after charging. This is sulfation, which is what we call battery vulcanization. Vulcanization is like applying a film to the internal lead plate of the battery, so that the lead plate in the battery cannot work (the reflection area of charging and discharging of the negative plate is reduced), resulting in battery failure. This type of battery failure is the most common, and it can be said that 70% to 80% of batteries have this problem.

When the battery is vulcanized, how will the battery behave:

After the battery is vulcanized, the charging time is shortened. Normally, the battery is fully charged for 6-8 hours, and the vulcanized battery is fully charged in 2 to 3 hours; bubbles are generated prematurely during charging, and even a charge has bubbles (the ear sticks to the battery) You can hear the "beep" sound; the battery is hot; when the vulcanization is severe, the battery may not be charged. “A full charge, one run is light” is a typical feature of battery vulcanization.

What causes the battery to vulcanize:

1. The battery is not fully charged for a long time, or it is not charged in time after discharge. (A lot of inferior charging will make the battery charge insufficient, the charger shows that the battery is fully charged, in fact, the battery is not full)

2. Long-term discharge or low-current deep discharge.

3. After the battery is used up, it will be idle for a long time without charging.

4. The concentration of acid in the electrolyte is too high, the composition is impure, and the outside temperature changes drastically.

3. Battery positive plate softening

Intuitively, during the charging process, the electrolyte is extracted. If the electrolyte is red or black, it is even muddy, indicating that the positive plate has softened.

What causes the positive plate to soften:

1. High current discharge. Especially when manned, brought, uphill, and started, the battery discharge current can reach tens of amps, which is several times the normal discharge current.

2. Deep discharge. For example, often use the virtual voltage inside the battery to work.

3. Battery positive plate gassing (from this point we can see that the gas evolution of the positive plate is caused by water loss and vulcanization of the battery, that is, the loss of water and vulcanization of the battery will lead to the softening of the positive plate of the battery).

4. High current charging.

Fourth, the battery is out of control

The situation of thermal runaway is as follows:

When charging the battery, especially at the end of charging, the charger does not turn green, and the colleague's battery is extremely hot. (When the heat is severe, the internal gas pressure of the battery is too high, which will cause the battery case to be deformed and damaged by heat until the battery is scrapped.) This is the battery that we often see is charged.

What caused the battery to run out of control:

1. Battery dehydration

2. Single grid is behind (one of the six individual grids inside the battery has a low voltage)

3. The charging voltage is too high

4. Oxygen cycle usually (oxygen precipitated from the positive electrode plate acts directly on the negative electrode plate, and the resulting one cannot be discharged in time to form thermal runaway)

Five. Battery short circuit

Several cases of battery short circuit performance:

1. The positive and negative plates of the battery are directly contacted or overlapped by other conductive ignorance.

2. Measure the open circuit voltage of the battery, which is only about 10.5V~10.7V.

3. When deep discharge, touch the battery by hand, the battery is out of heat, and a certain point in the local is particularly hot.

4. When charging, the voltage rises very slowly, always keeps a low value, and the electrolyte temperature rises very quickly.

What is causing the battery to be shorted:

1. More lead sulfate is accumulated in the separator inside the battery.

2. The active material on the plate is detached and deposited too much, so that the lower edge or the side edge of the positive and negative plates are in contact with the deposition material, causing the positive and negative plates to be connected.

3. The "lead flow" formed during the welding of the pole group is not removed or there is a "lead bean" between the positive and negative plates during the assembly, and the separator is damaged during the charging and discharging process, causing the positive and negative electrodes of the separator to be short-circuited.

4. The battery that is stored over time and has no regular maintenance. When recharging, the plate starts to produce a short circuit of the crystal branches.

Six. Battery open circuit

Open battery is a rare battery failure situation, the main performance is that the charge is not charged, measuring the terminal voltage of the open circuit, can reach about 13V, but there is no current output. Some open-circuit battery terminals have a voltage of 0 V. Discharge with the bulb, the bulb does not illuminate, and the battery is internally ignited in severe cases. If the positive and negative poles are short-circuited with wires, there is no star spark. The battery voltage can be detected first by a multimeter. If it is zero, the short-circuit ignition detection is used. If there is no spark, it can be judged that the battery is open.

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