What is the difference between fast charging and slow charging of lithium-ion batteries?

October 10, 2020

What is the difference between fast charging and slow charging of lithium-ion batteries?


The purpose of fast charging is to allow the vehicle to be charged to replenish more than 50-60% of the electric energy in a relatively short period of time, but battery technology, power transmission and distribution technology, especially heat dissipation technology cannot do it. At present, most of them are fixed 380V chargers in public parking lots. Special lines can supply higher power and larger current charging. Some are centralized high voltage introduction, converted into direct current, and connected to large battery packs. This can supply a higher charging current and prevent the impact on the grid when connected.

Slow charging is generally called a car charger, which means that the two-stage conversion circuit is built in the car. Since the power car can be plugged in, it is very convenient for home use. It only needs to be connected with 220V AC. The fast charging power is relatively large, generally tens of kW.

1. The difference between fast charging and slow charging is: the conversion circuit in the claw machine is different. The slow charge type converts 5V to 4.2V, and the fast charge type converts 9V (or higher voltage) to 4.2V. Although fast charging can greatly shorten the charging time, it also greatly shortens the cycle life of lithium-ion batteries, while slow charging does less damage to battery equipment.

The charging voltage of lithium-ion batteries has a limit, generally cannot exceed about 4.2V; and fast charging technology even requires 9V or higher. If such a high voltage is directly fed to the battery, the battery cannot stand it. Therefore, there is a special circuit in the claw machine, which is responsible for converting the voltage of 5V or 9V into the voltage that the battery can withstand, which is used for battery charging. Slow charging generally uses an ordinary 5V charger, and the charging power generally does not exceed 5Vx2A=10W. And fast charging often uses a voltage of 9V or higher, and the charging power is at least 9Vx2A=18W.

2. Fast charging and slow charging are relative. Generally, fast charging is high-power DC charging, which is the charging interface of DC charging piles. It converts the AC power of the grid into DC power and transmits it to the fast charging port of new energy vehicles. The electric energy directly enters the battery for charging. , It can fully charge 80% of the battery capacity in half an hour. Slow charge refers to AC charging, which is the charging interface of AC charging pile. The AC power from the grid is input into the slow charging port of the electric vehicle, and the AC power is converted into Direct current, then input the battery to complete the charging, the charging time is generally 7-8h.