Some principles of lithium battery charging

1. What is the most suitable current for lithium-ion battery charging?

Lithium-ion battery charging requires constant current charging, that is, the current is constant, and the battery voltage gradually increases with the charging process. When the battery terminal voltage reaches 4.2 v (4.1 v), the constant current charging is changed to constant voltage charging, that is, the voltage is constant. The current is gradually reduced according to the saturation degree of the cell, and as the charging process continues to decrease, when it is reduced to 0.01 degrees Celsius, the charging is considered to be terminated. (C is a representation of the battery's nominal capacity against the current, such as the battery is 1000 mah capacity, 1 C is the charging current 1000 mA, pay attention to the horse instead of ah, 0.01 degrees Celsius is 10). Why do you think that 0.01 degrees Celsius is the end of charging: this is stipulated in the national standard GB / t18287 - 2000 and is also discussed. In the past, people generally ended with 20 mA. The Ministry of Posts and Telecommunications industry standard code / t998 - 1999 also stipulated that regardless of the battery capacity, the stop current is 20 mA. The 0.01 degree Celsius specified by the national standard helps to make the charging more full, which is beneficial to the manufacturer. In addition, the national standard stipulates that the charging time does not exceed 8 hours, that is to say, even if it has not reached 0.01 degrees Celsius, the 8th hour is reached, and the charging is considered to be over. (Battery with no problem in quality should reach 0.01 degrees Celsius in 8 hours, battery with poor quality, etc. is meaningless.) The best charging rate for lithium ion or lithium polymer battery pack is 1 c, which means one The 1000 mah battery pack is quickly charged at 1000 mA. Charging at this rate allows for the shortest charging time without compromising battery performance and shortening the life of the battery pack. For a battery pack with an increasing capacity, to achieve such a satisfactory charging rate, it is inevitable to increase the charging current value.

2. What is the most suitable voltage for lithium-ion battery charging?

Lithium-ion battery nominal voltage 3.7 v (3.6 v), charge cut-off voltage 4.2 v (4.1 v, according to the battery brand has a different design) How to distinguish the battery is 4.1 v or 4.2 v: consumers can not be distinguished, This depends on the product specifications of the battery manufacturer. Some brands of batteries are 4.1 v and 4.2 v common, such as tuberculosis (Toshiba), domestic manufacturers are basically 4.2 v. What happens when you charge a 4.1 v battery to 4.2 v: It will increase the battery capacity, feel good, and increase the standby time, but it will shorten the battery life. For example, the original 500 times, reduced to 300 times. By the same token, overcharging a 4.2 volt battery will also shorten the life. Lithium-ion batteries are very delicate. Since there is a protective board inside the battery, can we rest assured: No, because the cut-off parameter of the protection board is 4.35 v (this is still good, the difference is 4.4 to 4.5 v), the protection board is in case of a failure, If you overcharge each time, the battery will decay quickly.

3. What is the battery specification of the Apple iPhone?

Apple iPhone's battery specification is nominal voltage 3.7 v, charge cutoff voltage 4.2 v, battery capacity 1400 mah, according to what we said above, the best charging rate 1 c, need to reach 1400 mA current to start charging, the voltage is 3.7 v, after the voltage reaches 4.2 v, the constant voltage charging starts, until it reaches 0.01 degrees Celsius, the horse is 14 to stop charging.

4. What is the voltage and current of the usb interface and the charger?

The current of the usb interface is 500 mA, and the voltage is + 5 v. If you turn on HWinfo during charging, you can also see that ExternalPower is a 500 mAh charger designed for the iPhone. I think everyone understands the voltage. White, what can be inserted into the power socket, do not need to say it again? Use the charger to charge, open HWinfo can see the ExternalPower one is 1000 mA, when you use usb When charging, the voltage is + 5 v, and the current is only 500 mA. We know in the answers to questions 1 and 2 that this method will increase the battery capacity, which is very cool to use, but will shorten the battery life. When using the charger to charge, you may ask, are you not saying that the optimal speed is 1 c? The iPhone should be 1400 mAh charging current, right, no mistake, but the country has a rule, the national standard The specified low-rate charging is 0.2 degrees Celsius (arbitration charging system), and the iPhone's 1400 mAh capacity battery is 280 mA. In theory, the smaller the battery, the better the battery. But you can't charge for a battery for 3 days. (Capacity mAh = current horse × time h) So Apple chose 0.7 degrees Celsius, most of the batteries are between 0.5 and 0.8 c. 5 you can choose! It is obvious that someone uses usb to charge, it feels longer, but that is At the expense of battery life.

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