Do I need to charge the battery for 12 hours the first three times?

The answer is that you don’t need to charge for 12 hours.

　　 Early cell phone Ni-MH batteries required replenishment and trickle charging. It may take about 5 hours to reach the most perfect full charge, but it does not require 12 hours. The constant current and constant voltage charging characteristics of lithium-ion batteries determine that its deep charging time does not need 12 hours.

　　 For lithium-ion batteries, some people may ask, since the current of the lithium-ion battery gradually decreases during the constant voltage stage, is it true that deep charging is done when the current is as small as infinitely small. I once drew the curve of current reduction versus time in the constant voltage stage, and performed multiple curve fittings on it. I found that this curve can be approached to zero current by a function of 1/x. The actual test is due to the existence of the lithium-ion battery itself. The self-discharge phenomenon, this zero current can never be reached.

Take a 600mAh battery as an example, set the cut-off current to 0.01C (ie 6mA), and its 1C charging time does not exceed 150 minutes, then set the cut-off current to 0.001C (ie 0.6mA), and its charging time may be 10 hours- --Because of the accuracy of the instrument, it has not been accurately obtained, but the capacity obtained from 0.01C to 0.001C is calculated to be only 1.7mAh, which is less than three-thousandths of it in exchange for more than 7 hours. Capacity has no practical meaning.

　　 What's more, there are other charging methods, such as the pulse charging method to make the lithium-ion battery reach the limit voltage of 4.2V. It does not cut off the minimum current judgment stage at all. Generally, it is 100% fully charged after 150 minutes. Many mobile phones use pulse charging.

　　 Someone once used the mobile phone to display the full charge and then used the cradle to charge to confirm the fullness of the mobile phone. This test method is not rigorous.

　　First of all, the green light displayed on the charger is not a basis for detecting whether it is fully charged or not.

　　★★The only ultimate way to check whether a lithium-ion battery is fully charged or not is to test the voltage of the lithium-ion battery when it is not charging (nor discharging).

The real purpose of the so-called constant voltage phase current reduction is to gradually reduce the additional voltage generated by the charging current on the internal resistance of the battery. When the current is as small as 0.01C, such as 6mA, this current is multiplied by the internal resistance of the battery (usually at 200 Within milliohms) is only 1mV, and it can be considered that the voltage at this time is the battery voltage in the no-current state.

　　Secondly, the reference voltage of the mobile phone is not necessarily equal to the reference voltage of the cradle charger. The mobile phone thinks that the fully charged battery is on the cradle, but the cradle does not think it is fully charged, but continues to charge.