With the development of battery technology, the study of the maximum charging current of batteries is becoming increasingly important. During charging, exceeding the upper limit of the current that the battery can withstand will not only cause adverse reactions, but may also cause irreversible damage.

This article will discuss battery charging strategies and optimization of charging methods to improve efficiency to charge and battery performance.

## 1. Brief introduction to the principle of battery charging

After the battery is discharged, direct current is used to pass through the battery in the opposite direction to the discharge current to restore its working capacity, a process called battery charging.

When the battery is charged, the cathode of the it is connected to the cathode of the power supply, the anode of the battery is connected to the anode of the power supply, and the charging power supply voltage must be higher than the total electromotive force of the batteries. There are two charging methods: constant current charging and constant voltage charging.

## 2. What is the battery maximum charging current

The maximum battery charging current refers to the minimum current value that the batteries can charge under maximum conditions. In general, the standard charging current is 0.1C or 0.3C-0.4C. For example, a 1000mAh battery has a standard charging current of 100mA and a maximum of 400mA1. It should be noted that the maximum charging current cannot exceed 30% of the rated capacity current value.

For example, the maximum charging current of a 100AH battery cannot exceed 30A. When cycling charging, there should be a limit to the maximum voltage supplied by the charger. The charging voltage of a 6V battery is 7.2-7.5V, the charging voltage of a 12v battery is 14.6-16.8V, and the maximum charging current is not greater than 30% A of the rated capacity value (for example, the maximum charging current of a 2AH battery cannot be greater than 2×0.3=0.6 amperes).

It is appropriate to use a 10-hour charging rate (for example, a 2AH battery is 0.2 amperes), if the charging current is too large, the battery is easy to heat up, causing the plate to fall off, break, short circuit and cause explosion, combustion and other accidents.

## 3. Charging current change process

As far as the maximum charging current of the lithium battery in the fast charging stage is concerned, as a dynamic process, the optimal charging current of the lithium battery is actually divided into three stages.

● Optimal current when precharged

When the initial or no charge voltage of the lithium battery is below the precharge threshold, it must first pass through a precharge stage. For a single lithium-ion battery, this threshold is usually 3.0V. At this stage, the precharge current is about 10% of the current of the next stage, the constant current charging stage.

● Optimal current for constant current charging

The so-called constant current is that the current is constant, the voltage gradually increases, and the fast charging stage is entered. Most of the constant charging current is set between 0.4-0.6C, which can be understood as 0.5C. That is, it can be fully charged in about two hours without considering other factors. The reason why 0.5C was chosen is because this current balances charging time and charging safety.

● Charging current during constant voltage charging

As far as a single lithium-ion battery is concerned, when the batteries reach a certain voltage value, that is to say, enter a constant voltage charge. This voltage value is usually 4.2V.

At this stage, the voltage does not change, the current decreases; this current reduction is a sequential process of decreasing. Most lithium battery protection uses 0.01C as the termination current, which means that the charging process enters the end state. After charging, the charging current drops to zero.

## 4. How to see the maximum charging current

Because lithium-ion batteries are customizable, their capacity and volume are proportional, so we can see lithium-ion batteries of various capacities and voltages. The capacity of lithium-ion batteries, we can see in the appearance of lithium-ion batteries, such as 800mAh, 1200mAh, etc.

Looking at this unit of capacity, you can actually see some deep meaning. For example, the lithium-ion battery labeled 800mAh means that if the battery supplies power to the device, the current required by the device is 800mA, then the battery will be consumed in 1 hour.

When we want to understand the battery more deeply, the battery manufacturer will give the maximum discharge current and maximum allowable charging current of the battery. However, the numbers given are often 0.5C, 1C, 3C. At this point, we have to figure it out ourselves. The calculation process is not very complicated.

The specific calculation method is as follows: For example, a battery with a nominal capacity of 800mAh, the maximum allowable charging current is 0.5C, then its allowable maximum charging current is 800 plus 0.5=400mA; The maximum allowable discharge current is 2C, then its maximum allowable discharge current is 800 plus 2=1600mA, that is, 1.6A.

## 5. How to calculate the lithium battery charging current

The maximum charging current that lithium batteries can accept is usually 1C or even smaller. Lithium battery charging current is generally marked on the charger. You see, lithium batteries usually use the charging mode of constant current and then constant voltage. When charging to the charger limit voltage, it will be trickle charging, so the charging time is also added to about 1 hour.

If you want to calculate the charging time, then divide the battery capacity by the charging current, plus conversion loss, and finally add an hour is almost the same. The can generally use a charge and discharge current of 1C or higher (15C), so they are more suitable as power batteries.

That is, the battery charging time is equal to the ratio of nominal capacity to maximum charging current. However, because the lithium battery will generate internal impedance when charging, so the charging time should consider the factors to overcome this impedance.

## 6. What is the maximum allowable charging current of the phone battery

Today, a 5.2v battery is used to charge the mobile phone battery, and the current measured with a multimeter has reached 2A, and within a minute, the mobile phone battery has a fever. Ask how much charging the current cell phone battery allows. It depends on the capacity of your phone.

The general standard charging current is 0.1C, and the maximum charging current is 0.3C-0.4C. For example, a 1000mAh battery has a standard charging current of 100mA and a maximum of 400mA. It is recommended to charge with standard charging current, high current charging will shorten battery life, and even have the risk of explosion.

Your 2A charging current is too large, do not use such a large, charging for a long time is likely to explode! What is the meaning of this value First of all, you must understand that the discharge capacity of the battery is not infinite, not that the capacity is large enough. Therefore, when choosing a battery, it is necessary to judge according to the power consumption of the device.

## 7. Optimal charging current for lithium batteries

The best charging current for lithium batteries. How to calculate the maximum charging current of lithium batteries? Lithium battery charging current and voltage are dynamically changing, which is determined by the chemical substance of the lithium battery itself. Therefore, it is necessary to configure the performance of the charging IC according to the charging characteristics of the lithium battery itself to achieve the correct, safe and efficient use of the lithium battery.

The maximum charging current of lithium batteries is determined according to the capacity. The higher the current, the less likely the battery is to be fully charged. This is done to protect the normal use of lithium batteries, because overcharge and overdischarge will cause lithium batteries to leak or fail their functions, or even explode.

The core of the best and maximum charging current of lithium batteries is the current design during constant current charging, and it should be emphasized here that most portable lithium batteries are better designed for 0.5C charging. For example, the conventional capacity of 18650 battery is 1800-2600mAh, and 1A charging can be selected, while the rate type is 1200-1500mAh, and the charging current of 0.5C is 0.7A.

The maximum charging current of lithium batteries is strictly determined by the structure of the batteries. Therefore, the various lithium battery manufacturers are not consistent in this regulation, some are set to 0.6C, and the maximum provision for portable lithium batteries is 1C.

## 8. Conclusion

Maximum charging current is a key factor affecting charging efficiency and battery life. In the design of brake energy recovery control systems, appropriate charging strategies and optimal charging methods should be adopted according to battery characteristics. Understanding the characteristics of the power battery, including the impact of rated capacity, voltage range, and temperature on charging performance, is critical to designing the maximum charge current.

Flexibly applying constant current, constant voltage and intelligent charging strategies, maximum charging current can be dynamically adjusted according to the actual situation to improve charging efficiency and system performance. At the same time, through the application of fast charging technology and intelligent charging control systems, the charging method can be further optimized to achieve a more efficient charging process.