I, the voltage is not consistent, individual low
1. Large self-discharge causes low voltage
The large self-discharge of the cell makes its voltage drop faster than others. The voltage drop can be eliminated by checking the voltage after storage.
2. Uneven charge causes low voltage
When the battery is charged after detection, the battery core is charged unevenly due to the inconsistent contact resistance or the charging current of the detection cabinet. In a short time of storage (12 hours), the voltage difference is very small, but the long-term storage voltage difference is large, this low voltage has no quality problems, can be solved by charging. In production after charging storage for more than 24 hours to measure the voltage.
II, the internal resistance is too large
1. Test equipment difference
If the detection accuracy is not enough or can not eliminate the contact electric group, will cause the display of internal resistance is too large, should use the AC bridge method principle to test the internal resistance instrument detection.
2. Storage time is too long
Lithium-ion battery storage is too long, resulting in large capacity loss, internal passivation, internal resistance becomes larger, which can be solved by charging and discharging activation.
3. Large internal resistance caused by abnormal heat
The cell in the processing (spot welding, ultrasonic, etc.) makes the battery abnormal heat, so that the diaphragm thermal closure phenomenon, the internal resistance seriously increased.
III, lithium battery expansion
1. Lithium-ion batteries expand while charging
Lithium battery is charging, lithium battery will naturally produce expansion, but generally not more than 0.1mm, but overcharging will cause electrolyte decomposition, internal pressure increases, lithium battery expansion.
2. Expand during processing
Generally, there are processing abnormalities (such as short circuit, overheating, etc.) caused by excessive internal heating electrolyte decomposition, lithium battery expansion.
3. Expand during the cycle
During the cycle, the thickness of the battery will increase with the increase of the number of cycles, but it does not increase after more than 50 weeks. Generally, the normal increase is 0.3~ 0.6mm, and the aluminum shell is more serious. This phenomenon is caused by normal battery reactions. However, if the thickness of the shell is increased or the internal material is reduced, the expansion phenomenon can be alleviated appropriately.
IV, the battery after spot welding power down phenomenon
After spot welding, the voltage of aluminum shell cell is lower than 3.7V, generally because the spot welding current is too large, which causes the breakdown of the inner diaphragm of the cell and short circuit, resulting in too fast voltage drop.
Generally, the spot welding position is not correct. The correct spot welding position should be at the bottom or on the side marked with "A" or "-". The side and large sides can not be spot welded without marks. In addition, some are spot welding nickel belt weldability is too poor, so must use a large current spot welding, resulting in the internal high-temperature resistant tape can not work, resulting in the internal short circuit of the electric core.
After spot welding, the battery is partially due to the larger self-discharge of the battery itself.
V, battery explosion
Battery explosion generally has the following situations:
1. Overcharge explosion
Protection line out of control or detection cabinet out of control so that the charging voltage is greater than 5V, resulting in electrolyte decomposition, the violent reaction inside the battery, battery pressure rapidly rise, battery explosion.
2. Overflow explosion
Protection line out of control or detection cabinet out of control so that the charging current is too large to cause lithium ions embedded, and in the surface of the electrode sheet lithium metal, through the diaphragm, the positive and negative electrode direct short circuit resulting in explosion (rarely).
3. Explosion when ultrasonic welding plastic shell
When ultrasonic welding plastic shell, due to equipment reasons, the ultrasonic energy is transferred to the battery core. The ultrasonic energy will make the inner diaphragm of the battery melt, and the positive and negative electrodes will directly short circuit, resulting in an explosion.
4. Explosion during spot welding
Spot welding current is too large, resulting in serious internal short circuits and explosions. In addition, the positive electrode connection plate is directly connected with the negative electrode during spot welding, making the positive and negative electrodes explode after a direct short circuit.
5. Over-discharge explosion
Battery over-discharge or discharge (above 3C) is easy to cause the negative copper foil to dissolve and deposit on the diaphragm so that the positive and negative direct short circuit to produce explosion (rarely).
6. Explosion when vibration falls
The core in the violent vibration or fall caused by the dislocation of the core internal pole, direct serious short circuit, and explosion (rarely).
VI. Low battery 3.6V platform
1. Inaccurate sampling of the testing cabinet or unstable testing cabinet results in a low test platform.
2. Low ambient temperature causes low platform (discharge platform is greatly affected by ambient temperature)
Seven, improper processing caused
(1) forcibly moving the spot welding positive electrode connecting piece causes bad contact of the positive electrode of the cell, so that the internal resistance of the cell is large.
(2) the spot welding joint is not welded firmly, the contact resistance is large so that the internal resistance of the battery is large.
