Lithium ion battery is a kind of secondary battery, which can achieve the effect of charging and discharging by moving lithium ion back and forth between the positive and negative electrodes.And compared with other secondary batteries, lithium ion battery has the advantages of high energy density, large discharge capacity and long cycle life, so lithium ion batteries are widely used in mobile phones, computers, new energy vehicles and other industries.
However, many nonprofessionals have biased cognition of lithium ion battery, which are mostly reflected in the deviation of battery voltage, use method and capacitance. And some unscrupulous manufacturers will also produce shoddy lithium-ion batteries in order to save costs. Understanding the characteristics of these lithium ion batteries is also an important prerequisite to help us use them properly and purchase qualified lithium-ion batteries.
What is nominal lithium ion battery voltage
In fact, the voltage of lithium ion battery is constantly changing in the process of charging and discharging (it will also slowly self discharge when it is idle). The voltage of the battery will continue to increase during charging, otherwise, it will continue to decrease while discharging.And the maximum and minimum voltage of Li-ion battery during charging and discharging are about 4.2V and 3V respectively.
To be precise, the nominal voltage of a lithium ion battery refers to the potential difference of the lithium ion battery when it is discharged, it's also like the middle of the maximum and minimum voltage of a battery. The nominal voltage of a normal lithium ion battery is about 3.7V, while the maximum voltage and minimum voltage during discharge are generally 4.2V and 3V. This means that when the discharge voltage is between 4.2V to 3.7V and 3.7V to 3V, the voltage drop is very large. In the process of discharge, the discharge time is the longest when the voltage is 3.7V, which accounts for about 3/4 of the total discharge time. It can be said that the best period in the discharge process of lithium ion battery is the period at nominal voltage.
Due to the advantages of the discharge abilities of lithium ion batteries, many manufacturers will mark the nominal voltage of lithium ion batteries on their products, so as to gain competitive advantages with other types of batteries in the market( Compared with secondary batteries such as nickel cadmium batteries, lithium-ion batteries have more prominent advantages). Therefore, the nominal voltage can also be used to measure the discharge capacity of the battery.
Is it better to keep lithium ion batteries charged
Absolutely not, many people are used to charging the battery on the charger after the battery is fully charged, so as to keep the battery full, but doing so will cause damage to the battery and bring security risks. Firstly, the overcharge resistance of lithium ion battery is weaker than that of other secondary batteries. When the lithium ion battery is overcharged, the voltage of the battery will rise and exceed the maximum voltage limit, which will cause irreversible changes in the structure of the positive active material of the battery and make the electrolyte decomposition ineffective. These chemical changes will produce a large amount of gas and heat energy, which makes the temperature and internal pressure of the battery increase rapidly, and lead to shell rupture, leakage, even combustion and explosion.
There is an old saying that "take precautions against burning." Although most lithium ion batteries are equipped with a protection board (a control circuit) to prevent overcharge, over discharge and overheating, it is better not to fully charge or discharge the battery. Compared with full charging and discharging, shallow discharges and recharges have less pressure on the battery, which will give battery a long cycle life.
Therefore, do not keep the lithium ion battery charging state all the time, especially when the battery is full. If you do this, the aging speed of the battery will be accelerated, and the protection board may fail (especially for cheap lithium ion batteries, businesses will use simple circuit boards in order to save costs). And the harm of overcharge caused by fail of the protection board must be noticed.
What is the relationship between voltage and capacity of lithium ion battery
A normal lithium-ion battery has a working voltage of about 3V to 4.2V, a nominal voltage of about 3.7V and a capacity of 2200mAh to 2600mAh. Actually, the voltage and power of lithium ion battery are dynamically related. When discharging, the current of the battery will flow out, and the voltage will continue to drop. Therefore, the battery power can be calculated by measuring the voltage. This method is similar to measuring the water volume through the water level, but it is very complicated to use this method to measure the electric quantity.
To site a case, under normal circumstances, when the voltage of lithium ion battery is 4.2V, the battery capacity can be estimated as 100%, and when the voltage reaches 3.82v, the battery voltage can be regarded as reaching 50%.
The voltage of all lithium-ion batteries is similar, but the capacitance and discharge efficiency of different types of lithium-ion batteries are different. Generally, when purchase lithium-ion batteries, the top lithium-ion batteries often have the advantages of high capacity and high discharge efficiency.
To draw a conclusion, lithium ion battery’s nominal voltage is about 3.7V, which is the milestone of voltage change when discharge. And when your lithium ion battery is fully charge, please stop recharging, otherwise it will damage the cycle life of battery or bring potential safety hazard to user. Moreover, by looking for the rule and calculation, the real-time voltage of the lithium ion battery can also be used as an indicator to measure the battery power.
As the mainstream of battery industry, lithium ion battery has many advantages such as high efficiency, low pollution and high safety. And it is also a required course for consumers to understand the structure and principle of lithium ion battery, and learn how to use it properly and give full play to the maximum value of battery.
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