As the Lithium battery charging process diagram shows:

In the above figure, the abscissa is time and the ordinate is the voltage of the lithium battery.

Due to the particularity of lithium batteries, over-voltage or under-voltage will cause the battery to be scrapped, so the battery protection circuit is to measure the voltage of the lithium battery, and then judge whether the lithium battery is in a normal state based on the voltage to avoid over-voltage or under-voltage.

The charging current of the lithium battery is shown in the pink line above.

The charging of lithium batteries is divided into three stages, namely constant current pre-charging, high current constant current charging and constant voltage charging. When the voltage is lower than 3.0V, the charger will pre-charge the lithium battery with a current of 100mA. This is the CC Pre-charge stage in the above picture. Called constant current pre-charge stage. The purpose is to slowly recover the over-discharged lithium battery. It’s a protective measure. Qualified chargers will have this charging stage.

Then came the ones related to the problem. When the voltage of the lithium battery is higher than 3.0V, it enters the second stage, the high current constant current charging stage (C C Fast charge). Since the lithium battery has undergone the first stage of pre-charging, its state has been relatively stable.

Therefore, in the second stage, the charging current can be appropriately increased. According to different batteries, the current can range from 0.1C to 3-6C, where C refers to the battery capacity, such as a 1000mAh lithium battery, 0.1C is Refers to a current of 100mA. In this charging stage, the standard charging recommended by the country is to charge with a current of 0.1C, which is the standard charging. However, since the standard charging standard was proposed very early, it was proposed more than ten years ago. At that time, because lithium battery technology was far less stable than it is now (high-current charging is not allowed), there was such a standard. The only advantage of using standard charging is that the charging process is stable and the chance of explosions is very small; the disadvantage is that it takes time.

Fast charging refers to charging with a current greater than 0.1C at this stage. If the lithium battery capacity is 1000mAh, then the standard charging current is 100mA, as long as the charging current is greater than 100mA, it can be defined as fast charging. However, as far as the current level of lithium batteries and the level of charge and discharge management chips are concerned, charging with 1C current becomes easier. So fast charging is not as dangerous as imagined.

Generally, the charging current of fast charging is 0.2~1C, so fast charging is still safe. Due to improvements in recent years, current chargers are basically fast-charging types. The last stage of lithium battery charging is the constant voltage charging stage. In this stage, when the voltage of the lithium battery is detected to be 4.2V, the charger enters the constant voltage charging mode. At this stage, the charging voltage is constant at 4.2V, and the charging current is increasing. The smaller (slowly full, the current will definitely become smaller).

When the charging current is less than 100mA, it is judged that the battery is full and the charging circuit is cut off. The characteristics of this stage can also explain why after the mobile phone indicates that it is fully charged, unplug the USB cable and plug it in again, the mobile phone displays to continue charging. In addition, what needs to be said is that the above charging is the most ideal charging process for single-cell lithium batteries. The current qualified lithium battery charge and discharge protection boards all work in this way.

There are generally two types of batteries for battery cars: lead-acid batteries and lithium batteries. These batteries are composed of several batteries (the lead-acid battery type is composed of 6 or 8 series and parallel; the lithium battery type is composed of several lithium batteries in series and parallel). When it comes to the charging method of the battery pack, there is another big problem here, which is the problem of battery balance. It can only be said that most of the current battery car batteries do not have battery balance management, so this leads to the life of the battery pack is far less than the life of a single battery, which also explains why the battery of the electronic car is not durable and is scrapped in about a year.

It also explained that the current dilemma of the development of electric vehicles is the limitation of battery pack technology. Simply put, the conclusion is: fast charging refers to a charging method with a charging current greater than 0.2C. This charging method has a very small impact on the life and stability of a single lithium battery; but if it is for the battery pack of a battery car , Fast charge is an act of exchanging time for battery life. The last thing to say is: using the standard charger to charge the battery car is recommend; but for those charging stations that are fully charged in 10 minutes, it should be noted that using these charging stations will definitely greatly affect the battery life. In addition, for battery packs, battery balancing is more important.