Common Causes and Solutions of Lithium Ion (2)


Fourth, the battery loses power after spot welding Afte […]

Fourth, the battery loses power after spot welding
After spot welding, the voltage of the aluminum shell cell is lower than 3.7V. Generally, the over-current of the spot welding causes the internal diaphragm of the cell to break down and short-circuit, which causes the voltage to drop too quickly. Generally, the spot welding position is incorrect. The correct spot welding position should be spot welding at the bottom or marked with "A" or "-" side. Unmarked sides and large sides cannot be spot welded. In addition, some of the spot welding nickel strips have poor weldability, so a large current spot welding must be used, so that the internal high temperature resistant tape can not work, causing an internal short circuit in the cell. Part of the battery power failure after spot welding is also due to the large self-discharge of the battery.
V. Battery explosion
There are several situations in which a battery explosion occurs:
1. Overcharge explosion: The protection circuit is out of control or the detection cabinet is out of control, causing the charging voltage to be greater than 5V, which causes the electrolyte to decompose, a violent reaction occurs inside the battery, the battery internal pressure rises rapidly, and the battery explodes.
2. Overcurrent explosion: The protection circuit is out of control or the detection cabinet is out of control, so that the charging current is too large and lithium ions are too late to be embedded. Lithium metal is formed on the surface of the pole piece, penetrates the diaphragm, and the positive and negative electrodes are directly short-circuited to cause explosion (rarely).
3. Explosion when ultrasonic welding plastic case: When ultrasonic welding the plastic case, the ultrasonic energy is transferred to the battery core due to equipment reasons. The ultrasonic energy is very large, which causes the internal membrane of the battery to melt, and the positive and negative electrodes are directly short-circuited, causing an explosion.
4. Explosion during spot welding: When the current is too large during spot welding, an internal serious short circuit will cause an explosion. In addition, the positive electrode connection piece is directly connected to the negative electrode during spot welding, which will cause the positive electrode and the negative electrode to explode after a short circuit.
5. Over-discharge explosion: Over-discharge or over-current discharge of the battery (above 3C) can easily dissolve and deposit the negative electrode copper foil on the separator and cause the positive and negative electrodes to short-circuit directly to cause an explosion (rarely).
6. Explosion when dropping due to vibration: When the battery core is severely vibrated or dropped, the internal pole pieces of the battery cell will be dislocated, which will directly cause a serious short circuit and explode (rarely).
Low battery 3.6V platform
1. The sampling platform of the testing cabinet is inaccurate or the testing cabinet is unstable, resulting in a low testing platform.
2. Low platform due to low ambient temperature (discharge platform is greatly affected by ambient temperature)
Seven, caused by improper processing
1. Forcibly move the spot welding positive electrode connecting piece to cause the poor contact of the positive electrode of the battery cell, which makes the internal resistance of the battery cell large.
2. The spot welding connection piece is not welded firmly, the contact resistance is large, and the internal resistance of the battery is large.