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18650 lithium battery charging and discharging

Author: Source: Datetime: 2016-11-24 15:48:57

According to industry standards, for lithium batteries, the capacity is generally the nominal minimum capacity, this capacity is a group of cells, at 25 degrees at room temperature, with full cc/cv0.5c, and after standing for a long time (12 hours). With 0.2C constant current discharge to 3.0V (a standard is 2.75V, but has little effect on 3V to 2.75V down very quickly without much capacity), the release of capacity value, due to a number of battery must have individual differences, the actual capacity of the battery discharge capacity of the lowest value. That is to say, the actual capacity of this batch of any battery should be greater than or equal to the nominal capacity. The batteries also can be used in solar power generator.


1, 18650 lithium battery charging process

 Battery charging

Some chargers use inexpensive program to achieve, in the control accuracy is not good enough, easy to cause the battery to charge the abnormal, or even damage the battery. Choose the time to choose a large brand charger 18650 lithium-ion battery charger, quality and after-sales service to ensure that the extension of the battery life. Brand protection 18650 lithium ion battery charger has four heavy protection: short circuit protection, over current protection, overvoltage protection, battery reverse protection function, etc.. Over charging protection: when the charger for lithium ion battery over charging, in order to prevent the temperature rise caused by the internal pressure rise, need to terminate the state of charge.


To this end, the protective device to monitor the battery voltage, when it reaches the battery over charging voltage, that is, the activation of the charging protection function, suspend the charge. Over discharge protection: to prevent over discharge state of lithium ion battery, when the battery voltage is lower than the lithium ion discharge voltage detection point, namely activation over discharge protection, stop the discharge, and keep the battery in a low quiescent current standby mode. Over current and short circuit protection: when the discharge current of the lithium ion battery is too large or short circuit, the protection device will activate the over current protection function. So regarding the lifepo4 batteries, it always with BMS together to use in solar power generator.


Lithium battery charging control is divided into two phases, the first phase is constant current charging, the battery voltage is less than 4.2V, the charger will be charged with a constant current. The second stage is the stage of constant voltage charging, when the battery voltage reaches 4.2V, the lithium battery characteristics, if the voltage is high, it will damage the charger will voltage fixed at 4.2V, the charging current gradually decreases, when the current is reduced to a certain value (usually 1/10 set current), cut off the charging circuit, charging indicator light, charging is completed.


Excessive discharge of lithium ion batteries will cause permanent damage to the positive and negative. Excessive discharge lead to negative carbon layer structure collapse, the collapse caused by lithium ion cannot be inserted into the charging process; excessive charging the lithium ion embedded carbon anode structure, resulting in part of lithium ion cannot be released.


2, 18650 lithium battery charging principle


The working principle of lithium ion battery is the principle of charge and discharge. When the battery is charged, the positive electrode of the battery is formed by the lithium ion generation, and the lithium ion is generated to move to the cathode through the electrolyte. As a negative electrode, the carbon is layered structure, it has a lot of micro holes, to reach the anode of lithium ion is embedded into the micro hole in the carbon layer, the more embedded lithium ion, the higher the charge capacity.


Similarly, when the battery discharge (which we use the battery), lithium ions in the cathode carbon layer prolapse, and back to the cathode movement. Back to the positive electrode of the lithium ion, the higher the discharge capacity. What we usually say is that the battery capacity is the discharge capacity. The battery can be used in solar backup generator.


It is not difficult to see that in the charge and discharge process of lithium ion battery, the lithium ion is in the state of movement from the anode to the cathode. If we put the lithium-ion battery figuratively as a rocking chair, rocking chair is arranged at two ends of the two poles of the battery, and the lithium ion is a excellent athlete, running back and forth in both ends of the rocking chair. Therefore, the experts gave lithium ion battery a cute name rocking chair battery.

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