18650 lithium battery charging mode and life

The battery itself will have a certain amount of self-leakage, and the protection board will also have a microampere level of power consumption, so in long-term storage, it is necessary to regularly measure the voltage and supplement the charge.

First, constant current charging: this method is still from the previous and the previous circuit, but the high charging current is limited, constant current constant voltage is actually the current limiting voltage, this circuit is more popular, such as Nanfu, and Xinyu flow, full of incomplete cut-off, to trickle floating charge. It is now believed that a long period of small current charging is one of the causes of battery bloating.

Second, high-voltage charging: This charging method does not have a special control circuit, directly using a 5V source (or a series of diode step-down) to charge the battery with a protection board, completely dependent on the high-voltage limit of the protection board. It is characterized by a large current at the beginning, and then gradually reduce, and float at any time.

Third, intelligent charging: this is now considered to be the ideal charging management method, following the charging algorithm mentioned at the beginning of this section, integrated in a small patch IC, the peripheral circuit is simple, stable and reliable, such as TP4054/4055/4056/4057, TP4002/5000, MAX1879 and so on. The important feature of this chip is to monitor the voltage and current at the same time when judging whether it is full, stop charging, or stop charging if the charging current is less than (usually about 50mA); Completely cut off after full, no trickle float charge, but monitor the voltage at any time, and start charging if the battery voltage drops to a certain value.

Fourth, constant voltage charging: this method is similar to one, constant voltage is actually a voltage limit, set a relatively accurate high voltage, and then to the voltage dead charge, less than oath, rivers and lakes said silly charge, this charger if the cut-off voltage is done very accurately, low but safe, if high also have to rely on the protection board, as for the naked battery self-blessing. Common in today's mobile phone universal charge and flashlight direct charge, the cost of this charger is less than one yuan, all made of inferior parts, Taobao retail price from to range, how long can be used is not easy to say.

Now 3.7V 18650 lithium-ion battery general cycle life can reach 500~1000 times, 3.2V 18650 general life can reach more than 2000, of course, the premise is the regular manufacturer of qualified batteries, if it is defective or counterfeit batteries, the life will be very short.

18650 LiFePO4 Battery basic structure

The life of 18650 Lithium Batteries is generally 300 to 500 charge cycles. Assuming that the amount of electricity supplied by a full discharge is Q, if the reduction of electricity after each charging cycle is not considered, the Lithium Battery can supply or supplement 300Q-500Q of electricity in its life. From this, we understand that if you charge it with 1/2 each time, you can charge 600-1000 times; If it is charged with 1/3 each time, it can be charged 900 to 1500 times. In the same way, if the random charge, the number of variable.

In short, no matter how it is charged, the total amount of power added to 300Q ~ 500Q is constant. Therefore, we can also understand that lithium-ion battery life is related to the total charge of the battery, and has nothing to do with the number of charges. There is little difference between deep discharge and shallow discharge and shallow charge on the life of lithium battery.