18650 is a standard lithium-ion battery model set by Sony Company in order to save cost. 18(mm) means the diameter of the battery, 65(mm) is the length of the battery, and 0 means the battery is cylindrical. As a lithium-ion battery, 18650 battery has the advantages of light weight, large capacity, no memory effect and no pollution, so it has been widely used in our daily life.
After decades of development, 18650 batteries and other lithium-ion batteries have gradually become the mainstream of the battery industry. 18650 batteries have a large capacity per unit density, so most of them are used in notebook computer batteries. In addition, because of its excellent stability in work, 18650 is widely used in various electronic fields: high-grade strong light flashlight, portable power supply, wireless data transmitter, thermal insulation clothing, shoes, portable instruments and meters, portable lighting equipment, portable printers, industrial equipment industrial equipment, medical equipment, etc.
How many volts does an 18650 battery have
Generally speaking, the standard rated voltage of 18650 battery is 3.6V or 3.7V, and some are 3.65V. And its voltage will change from high to low with the change of charging and discharging. First, to introduce the charge and discharge principle of 18650 lithium battery, when the battery is charged, lithium ion is generated on the positive electrode of the battery, and the generated lithium ion moves to the negative electrode through the electrolyte. The carbon as a negative electrode has a layered structure, which has many micropores. The lithium ions that reach the anode are embedded in the micropores of the carbon layer. The more lithium ions are embedded, the higher the charging capacity. On the contrary, when the battery is discharged, the lithium ion embedded in the negative carbon layer is released and moves back to the positive electrode. The more lithium ions returned to the positive electrode, the higher the discharge capacity. Therefore, what we usually call the capacity of the battery is discharge capacity. And, you should notice that the maximum voltage limit of 18650 battery is 4.2V. It is better not to let the voltage exceed this value, otherwise it may cause safety accidents.
The charging process of 18650 is divided into two stages. The first stage is constant current charging. When the battery voltage is lower than 4.2V, the charger will charge with constant current. When the battery voltage reaches 4.2V, due to the characteristics of lithium battery, if the voltage is higher, it will be damaged. So the battery will enter the constant voltage charging stage. The charger will fix the voltage at 4.2V, and the charging current will gradually decrease. When the current decreases to a certain value, the charger will cut off the charging circuit, the indicator light will be on, and the charging is completed.And the discharge process of the battery is also similar to this.
Is low voltage bad for 18650 battery
Absolutely yes, generally, when the voltage of 18650 battery is lower than 2.5V, the protection circuit will automatically cut off the discharge circuit, and the battery will go into sleep mode. However, the voltage of 18650 batteries which have been stored for a long time may be lower than or even far below 2.5V. At this time, the battery can be said to be in the state of deep discharge. Most of the battery chargers can't charge the battery with a voltage lower than 2.5V, which led to the scrapping of the 18650 battery. But, ‘when there is a will, there is a way’, there are also some ways to save these "scrapped batteries". As long as sufficient power is provided to these batteries, the voltage of the batteries can be increased so that they can continue to be charged normally. Some chargers with voltage rising function can do this easily. Just connect the battery to these chargers (these chargers are usually 5V), and the voltage of the battery will rise slowly and finally return to normal.
The 18650 battery which has been in low voltage, its capacity will continue to decrease. It is because of over discharge leads to the collapse of the carbon structure of the negative electrode, and the collapse will cause the lithium ion can not be inserted in the process of charging; overcharge makes too many lithium ions embedded in the negative carbon structure, and some of the lithium ions can no longer be released. All in all, do not let your 18650 battery voltage lower than 3.0V in the process of using, which can well maintain the cycle life of the battery.
How far can a 18650 battery be discharged
The service time of 18650 battery after charging is uncertain, which should be judged according to the capacity of the battery itself and the discharge efficiency, but the charging time of an 18650 battery is basically stable at 2 to 4 hours. For example, the discharge time of the battery with high capacity will be very long under the condition of low discharge rate, otherwise, the discharge time of the battery with low capacitance will be very short under the condition of high discharge rate.
The battery will have self discharge, which means that the battery will gradually lose power in the process of idle. The 18650 battery, which is belong to lithium-ion battery, has a very low self discharge rate. After charging, it can maintain its limit for several months. However, it should be noticed that in the process of using 18650 battery. It is better to charge the battery after the battery power is less than 10%, otherwise, this will greatly damage the battery cycle life. The life span of most modern 18650 batteries is about 500 cycles, and excessive power abuse can greatly reduce it to 200 cycles, or even 50 cycles.
The 18650 lithium ion battery has a long cycle life and very low maintenance cost in theory. But that doesn't mean we can abuse it. We still need to use it reasonably, avoid overcharge, over discharge and other wrong use methods to maximize the effect of this battery.
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