Explain in detail the causes and treatment measures of common problems with lithium batteries

The voltage is inconsistent, and some are low. Large self-discharge causes low voltage. The self-discharge of the cell is large, so that its voltage drops faster than others. The low voltage can be eliminated by checking the voltage after storage. 2. Uneven charging causes low voltage. When the battery is charged after the test, the battery cells are not evenly charged due to inconsistent contact resistance or the charging current of the test cabinet. The measured voltage difference is very small during short-term storage (12 hours), but the voltage difference is large during long-term storage. This low voltage has no quality problems and can be handled by charging. Stored for more than 24 hours to measure the voltage after being charged during processing. The internal resistance is too large. The difference in test equipment causes that if the test accuracy is not enough or the contact resistance cannot be eliminated, the display internal resistance will be too large. The AC bridge method principle should be used to detect internal resistance. 2. Long storage time Lithium battery storage is too long, resulting in excessive capacity loss, internal passivation, and internal resistance increase, which can be dealt with by charging and discharging activation. 3. Abnormal heating causes a large internal resistance cell in production (spot welding, ultrasonic, etc.), which makes the battery abnormally heated, causing the diaphragm to thermally close, and the internal resistance is severely increased. Lithium battery expansion Expansion of Lithium Batteries When Lithium Batteries are charged, Lithium Batteries will naturally swell, but generally no more than 0.1mm, but overcharging will cause electrolyte analysis, internal pressure increases, and Lithium batteries swell. 2. Expansion during production is generally due to abnormal production (such as short circuit, overheating, etc.) caused by excessive internal heating, electrolyte analysis, and lithium battery expansion. 3. When the expanded battery is cycled, the thickness will increase as the number of cycles increases, but it will 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 It is caused by normal battery reaction. However, if the thickness of the shell is increased or the internal materials are reduced, the expansion phenomenon can be appropriately reduced. Battery power-down phenomenon after spot welding The voltage of the aluminum shell battery cell after spot welding is lower than 3.7V, which is generally caused by the excessive spot welding current that causes the internal diaphragm of the battery cell to break down and short-circuit, causing the voltage to drop too fast. Generally, it is caused by incorrect spot welding position. The correct spot welding position should be spot welding on the bottom or marked A or side. Spot welding is not allowed on the side and large surface without marking. In addition, some spot-welded nickel strips have poor weldability, so they have to use high-current spot welding, so that the internal high-temperature-resistant tape cannot be used, resulting in a short circuit inside the battery core. Part of the battery power loss after spot welding is due to the large self-discharge of the battery itself. Batteries explode and battery explodes generally in the following situations: 1. The overcharge explosion protection circuit is out of control or the test cabinet is out of control so that the charging voltage is greater than 5V, causing electrolyte analysis, a violent reaction occurs inside the battery, the internal pressure of the battery rises rapidly, and the battery explodes. 2. The overcurrent explosion protection circuit is out of control or the test cabinet is out of control, so that the charging current is too large and the lithium ions are too late to be embedded, and lithium metal is formed on the surface of the pole piece, penetrates the diaphragm, and the positive and negative poles are directly short-circuited and cause an explosion (rarely). 3. Explosion during ultrasonic welding of plastic case. When ultrasonic welding of plastic case is caused by the device, the ultrasonic energy is transferred to the battery core. The large ultrasonic energy causes the internal diaphragm of the battery to melt, and the positive and negative electrodes are directly short-circuited and an explosion occurs. 4. Explosion during spot welding. Excessive current during spot welding caused severe internal short-circuit explosion. In addition, during spot welding, the positive electrode connecting piece was connected straight to the negative electrode, causing the positive and negative poles to explode after a straight short-circuit. 5. Over-discharge explosion. Battery over-discharge or over-current discharge (above 3C) will easily dissolve and deposit the negative electrode copper foil on the separator, causing the positive and negative electrodes to be directly short-circuited and explode (rarely). 6. When the battery is dropped due to vibration, the internal pole piece of the battery is misaligned due to severe vibration or drop, and the battery is severely short-circuited and exploded (rarely). Low battery 3.6V platform 1. The detection platform is low due to the inaccurate sampling of the test cabinet or the unstable test cabinet. 2. Low ambient temperature causes low platform (discharge platform is greatly affected by ambient temperature) caused by improper production 1. Move the positive electrode connecting piece of the spot welding forcefully to cause poor contact of the positive electrode of the battery core, which makes the internal resistance of the battery core large. 2. The spot welding connection piece is not firmly welded, and the contact resistance is large, which makes the battery internal resistance large. Statement: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete the previous article: BMS lithium battery protection function and purchase Method analysis