“…lithium battery caught fire, and exploded…” No, not another one! This is what we say or hear someone else say when there’s news about yet another battery accident. As widely used as lithium-ion battery, it’s not uncommon that similar incidents happen every now and then. So in here in this post, we share with you some of the most commonly seen root causes to lithium-ion battery accident and their solutions. Hope our post help you with what you need.
Symptom 1: Low voltage
If the voltage is below 2V, the internal structure of lithium battery will be damaged, and the battery life will be affected.
Root cause 1: High self-discharge, which causes low voltage.
Solution: Charge the bare lithium battery directly using the charger with over-voltage protection, but do not use universal charge. It could be quite dangerous.
Root cause 2: Uneven current. Due to contact resistance or detection of charge, the current is inconsistent caused by the uneven charge of the cell. In the short-term storage (12 hours), the voltage difference is very small, but the voltage difference is large when stored for a long time.
Solution: This low voltage has nothing to do with quality issues and can be solved by charging.
Symptom 2: Large internal resistance
Root cause 1: Detecting equipment differences. If the detection accuracy is not enough or the contact resistance cannot be eliminated, it will show that the internal resistance is too large.
Solution: The internal resistance should be tested by the principle of AC (Alternating Current) bridge method.
Root cause 2: Too long storage time. Lithium batteries are stored for too long, resulting in excessive capacity loss, internal passivation, and increased internal resistance.
Solution: It can be solved by charging and discharging activation.
Root cause 3: Abnormal heat. When the battery is processed (spot welding, ultrasonic, etc.), the battery is abnormally heated, causing the thermal closure of the diaphragm and sharply increased internal resistance.
Solution: Manufacturers should pay special attention to welding procedure. The battery should be carefully tested to control product quality.
Symptom 3: Lithium battery expansion
Case 1: Lithium battery expands when charging.
When charging lithium battery, it will naturally expand, but generally not more than 0.1 mm. However, overcharging will cause electrolyte decomposition, increase internal pressure, and finally lithium batteries expansion.
Solution: Don’t overcharge, especially don’t charge for more than 12 hours at a time.
Case 2: Lithium battery expands when processing.
Generally, there is processing abnormalities (such as short circuit, overheating, etc.), resulting internal overheating, electrolyte decomposition and battery expansion.
Solution: Manufacturers should strictly control the battery processing process and the workshop environment to avoid short circuit and overheating.
Case 3: Lithium battery expands during circulation.
As the battery circulates, the thickness increases as the number of cycles increases. However, after more than 50 weeks, it will not increase any more. Generally, the normal increase is 0.3 to 0.6 mm.
Solution: This is a normal battery reaction. Increasing the thickness of the casing or reducing the internal material can reduce the expansion.
Symptom 4: Battery loss after spot welding
Root cause 1: Incorrect spot welding location.
Solution: The correct spot welding position should be at the bottom or marked “A” or “-” side. Unmarked sides and large surface can’t be spot welded.
Root cause 2: Too large spot welding current. Some spot-welded nickel strips are poorly made, so it requires a large current to spot weld, which comes with high temperature, which then causes a short circuit inside the battery.
Solution: Using spot-welded nickel strips of good quality is what manufacturers should do.
Root cause 3: Large self-discharge. Partly, the loss is due to the large self-discharge of the battery itself.
Solution: Manufacturers should check electrolyte suitability and assembly problems, while controlling the dust-free workshop environment.
Symptom 5: Battery explosion
Root cause 1: Overcharge
If the protection circuit or the detection cabinet is out of control, the charging voltage will be greater than 5V, causing the electrolyte decomposition, violent reaction inside the battery, rapid rise of internal pressure of the battery. Eventually the battery explodes.
Root cause 2: Large ultrasonic energy
When welding the plastic shell with ultrasonic, whose energy is so powerful that it melts the inner diaphragm of the battery, the positive and negative electrodes have short circuit directly, thus with the explosion.
Root cause 3: The battery explodes when welding
Because of the large current, short circuit of the positive and negative electrode happens when spot welding, thus with the explosion.
Do you have any other problems? How did you work it out? If you have any ideas, please contact us or leave a comment. We’d be very happy to hear from you.