3.7 volt 18650 lithium battery

Analysis of the causes and solutions to the seven common problems in the use of 3.7 volt 18650 lithium battery

With the rapid development of science and technology, the scope of use and role of 3.7 volt 18650 lithium battery have long been self-evident. However, in our daily lives, lithium manganese battery accidents are always emerging and troubling us from time to time. The following is an analysis of the causes and solutions to common lithium manganese battery problems, hoping to help everyone. 1. Inconsistent voltage, some are low 1. Low voltage caused by large self-discharge The self-discharge of the battery cell is large, which makes its voltage drop faster than others. The low voltage can be eliminated by checking the voltage after storage; 2. Uneven charge causes low voltage After the battery is tested, the contact resistance or the charging current of the detection cabinet is inconsistent, causing the battery cell to be unevenly charged. The voltage difference is very small when stored for a short time (12 hours), but the voltage difference is large when stored for a long time. This low voltage does not have a quality problem and can be solved by charging. In production, the voltage is measured after being stored for more than 24 hours after charging. 2. The internal resistance is too large 1. Caused by differences in testing equipment. If the detection accuracy is not enough or the contact electrode cannot be eliminated, the displayed internal resistance will be too large. The AC bridge method principle should be used to test the internal resistance instrument; 2. The lithium manganese battery has been stored for too long, resulting in excessive capacity loss, internal passivation, and increased internal resistance. This can be solved by charging and discharging activation; 3. The internal resistance is large due to abnormal heating. The battery is abnormally heated during processing (spot welding, ultrasound, etc.), causing the diaphragm to thermally close and the internal resistance to increase seriously. 3. Lithium manganese battery expansion 1. Lithium manganese battery expansion during charging When charging, lithium manganese battery will naturally expand, but generally not more than 0.1mm, but overcharging will cause electrolyte decomposition, internal pressure increase, and lithium manganese battery expansion; 2. Expansion during processing is generally caused by abnormal processing (such as short circuit, overheating, etc.), resulting in excessive internal heat and electrolyte decomposition, and lithium manganese battery expansion; 3. Expansion during circulation When the battery is cycled, the thickness will increase with the increase of the number of cycles, but it will basically not increase after more than 50 cycles. Generally, the normal increase is 0.3~0.6mm, and the aluminum shell is more serious. This phenomenon is caused by normal battery reaction. However, if the shell thickness is increased or the internal material is reduced, the expansion phenomenon can be appropriately reduced. 4. The battery has power loss after spot welding. The voltage of the aluminum shell battery is lower than 3.7V after spot welding. Generally, it is because the spot welding current is too large to cause the internal diaphragm of the battery 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 at the bottom or on the side marked with "A" or "-". The side and large surface without marking cannot be spot welded. In addition, some spot welding nickel strips have poor weldability, so a large current must be used for spot welding, which makes the internal high-temperature resistant tape unable to work, causing a short circuit inside the battery cell. The battery power loss after spot welding is also partly due to the large self-discharge of the battery itself. 5. Battery explosion Battery explosion generally occurs in the following situations: 1. The overcharge explosion protection circuit is out of control or the detection cabinet is out of control, causing the charging voltage to be greater than 5V, causing the electrolyte to decompose, 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 detection cabinet is out of control, causing the charging current to be too large, causing the lithium ions to not be embedded in time, and lithium metal is formed on the surface of the electrode, penetrating the diaphragm, and the positive and negative electrodes are directly short-circuited to cause an explosion (rarely occurs); 3. Explosion during ultrasonic welding of plastic shells When ultrasonic welding of plastic shells, the ultrasonic energy is transferred to the battery due to equipment reasons. On the core, the ultrasonic energy is so large that the internal diaphragm of the battery melts, the positive and negative electrodes are directly short-circuited, and an explosion occurs; 4. Explosion during spot welding When the current is too large during spot welding, a serious internal short circuit occurs, resulting in an explosion. In addition, during spot welding, the positive electrode connector is directly connected to the negative electrode, causing a direct short circuit between the positive and negative electrodes and an explosion; 5. Over-discharge explosion Battery over-discharge or over-current discharge (above 3C) can easily dissolve the negative electrode copper foil and deposit it on the diaphragm, causing a direct short circuit between the positive and negative electrodes and an explosion (rarely occurs); 6. Explosion during vibration and drop The internal electrode of the battery cell is misaligned when the battery cell vibrates violently or falls, causing a direct serious short circuit and explosion (rarely occurs). 6. Low 3.6V platform of the battery 1. The test platform is low due to inaccurate sampling of the test cabinet or instability of the test cabinet; 2. The platform is low due to too low ambient temperature (the discharge platform is greatly affected by the ambient temperature). 7. Improper processing causes 1. Moving the spot welding positive electrode connector with force causes poor contact between the positive electrode of the battery cell, resulting in a large internal resistance of the battery cell; 2. The spot welding connector is not welded firmly, and the contact resistance is large, resulting in a large internal resistance of the battery. In short, when choosing lithium-manganese battery products, you should choose high-quality lithium-manganese battery products produced by professional lithium-manganese battery manufacturers to effectively avoid problems.

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