Some chargers use cheap ways to achieve, in the control accuracy is not good enough, easy to cause abnormal battery charging, or even damage the battery. When choosing a charger, try to choose a big brand of 18650 lithium ion battery charger, quality and after-sales guarantee, prolong the service life of the battery. Brand guarantee 18650 lithium ion battery charger has four protection: short circuit protection, over current protection, over voltage protection, battery reverse connection protection and so on. Overcharge protection: When the charger overcharges the lithium ion battery, it is necessary to terminate the charging state in order to guard against the increase of internal pressure caused by the rise of temperature.
Therefore, the protection device should monitor the battery voltage. When it reaches the battery overcharge voltage, it activates the overcharge protection function and stops charging. Overdischarge protection: In order to guard against the overdischarge state of lithium ion batteries, when the lithium ion battery voltage is lower than its overdischarge voltage test point, that is, the overdischarge protection is activated, the discharge is stopped, and the battery is kept in the standby mode of low static current. Overcurrent and short circuit protection: When the discharge current of a lithium-ion battery is too high or short circuit occurs, the protection device activates the overcurrent protection function.
Lithium ion battery charge control is divided into two stages, the first stage is constant current charge, when the battery voltage is lower than 4.2V, the charger will charge at a constant current. The second stage is the constant voltage charging stage, when the battery voltage is 4.2 V, due to the lithium ion battery characteristics, again if the voltage is high, will damage, the charger voltage will be fixed in 4.2 V, the charging current will be reduced gradually, when the current decreases to a certain value (usually 1/10 set current), to cut off the charging circuit, a complete charging indicator, charging is complete.
Excessive charging and discharging of lithium-ion batteries can cause permanent damage to the positive and negative terminals. Excessive discharge will lead to the collapse of the carbon lamellae structure of the negative electrode, and the collapse will cause the insertion of lithium ions during the charging process. Overcharging causes too many lithium ions to become embedded in the carbon structure of the cathode, and some of them can no longer be released.
Charging principle of 18650 lithium ion battery
Lithium-ion batteries work on the principle of charge and discharge. When the battery is charged, lithium ions are generated on the positive electrode of the battery, and the resulting lithium ions travel through the electrolyte to the negative electrode. The carbon as the negative electrode is layered and has many micropores. The lithium ions that reach the negative electrode are embedded in the pores of the carbon layer. The more lithium ions embedded in the carbon layer, the higher the charging capacity.
In the same way, when a battery is discharged (as we do when we use it), the lithium ions embedded in the carbon layer of the negative electrode break out and move back to the positive electrode. The more lithium ions returned to the positive electrode, the higher the discharge capacity. What we usually call the battery capacity refers to the discharge capacity.
It is not difficult to see that in the charge and discharge process of lithium ion battery, lithium ion is in the positive electrode → The cathode & rarr; The state of motion of the positive pole. If we take the lithium-ion battery figuratively as a rocking chair, the two ends of the rocking chair are the two poles of the battery, and the lithium ion is like an excellent athlete, running back and forth between the two ends of the rocking chair. So the experts gave lithium-ion batteries another cute name: rocking chair batteries.
