Everyone has heard that there are two differences between fast charging and slow charging in electric vehicles, and they all know that fast charging is much faster than slow charging, but what is the essential difference between them?

　　The concept of fast charge and slow charge: fast charge and slow charge are relative concepts. Generally, fast charge is high-power DC charging, which can fully charge 80% of the battery capacity in half an hour. Slow charge refers to AC charging, and the charging process takes 6-8 hours.

　　The voltage of fast charge DC charging is generally greater than the battery voltage. For example, if the battery voltage of BYD Qin is 400V DC, the DC charging voltage should be above 500V, and Qin’s power is 13KWH, then its charging current should be 32.5A, that is, the power of fast charging is P =UI=500V*32.5A=16.25KW.

　　Slow charging is charging by plugging into the 220V AC outlet of the home. Because the battery cannot accept AC charging, the slow charging is to convert 220V AC to DC and then boost it to the charging voltage of the battery, such as 500V DC, and then use this A direct current of 500V charges the battery.

　　It can be concluded that the maximum charging power of slow charging is about P=UI=220V*10A=2.2KW. It can be seen that the 16.25KW of fast charge is much larger than the 2.2KW of slow charge, so we can find that fast charge is much faster than slow charge.

　　The advantages and disadvantages of slow charging: small current, long charging time, low charger and installation cost; can make full use of power trough period for charging, reduce charging cost; can deep charge the battery, improve battery charging and discharging efficiency, and extend battery life.

　　Household slow-charging AC: Since the 220V AC sockets in general households are 10A and 16A, the charging current for slow-charging is generally less than 10A for safety, and it is calculated according to the 10A standard.

　　The advantages and disadvantages of fast charging: fast charging of the battery pack in a short period of time, fast charging speed; higher charging equipment installation requirements and costs, higher current and voltage, greater impact on the battery in a short period of time, long-term fast charging affects battery life.

　　The hazards of fast charging: The fast charging of lithium batteries is at the expense of the cycle life of the battery, because the battery is a device that generates electricity through electrochemical reactions. The charging is a reverse chemical reaction, and the fast charging will input the battery in an instant High current, frequent use of fast charging mode will reduce the battery's ability to restore and reduce the number of cycles of battery charging and discharging.

　　To put it simply, fast charging has high requirements for the quality of the battery, and the reaction conditions of the battery under high current are too harsh and severe, and it deviates far from the equilibrium state. There is a greater loss in the life of the battery, and the safety factor will be significantly reduced. Therefore, Do as little as possible when not necessary. And slow charging can avoid these problems.