The charging modes of electric vehicles mainly include fast charging and slow charging, and the use of fast charging and slow charging in electric vehicles has little impact on battery life. This is because in the process of fast charging of the vehicle, only when the power is at 30-80%, the charging current and power will reach the highest value, and when the power exceeds 80%, the current, power and voltage of the vehicle charging will also be greatly reduced, so the charging setting is conducive to prolonging the service life of the power battery. The slow charging adopts the constant current charging method, the charging current during the slow charging period is relatively small, and the current change is also very stable, which will not have much impact on the battery life. At the same time, whether it is fast charging or slow charging, when the electric vehicle is fully charged, it will automatically cut off the power and stop charging to prevent the battery from overcharging.
1. The difference between fast charging and slow charging
1. Fast charging
Fast charging is high-power DC charging, generally using a special off-board DC charger for charging, this charger is installed in a fixed charging place, connected with the AC input power supply, and the DC output terminal is connected with the charging interface of the electric vehicle that needs to be charged, which can meet the requirements of high-power fast charging of electric vehicles; Fast charging puts forward higher requirements for the voltage resistance and protection of the power battery pack; The charging current is large, ten times or even dozens of times that of the conventional charging current.
merit
0.5h can fully charge 80% of the capacity of the battery, after exceeding 80%, in order to protect the safety of the battery, the charging current becomes smaller, and the charging time to 100% will be longer.
shortcoming
Due to the characteristics of high charging voltage and high current, at the cost of reducing the number of battery charging and discharging cycles, it will cause certain damage to the battery and reduce the service life of the battery.
2. Slow charging
Slow charging is the use of on-board AC chargers for charging, conventional charging piles are mostly slow charging, such charging stations are generally distributed in residential areas or near workplaces. Home or office charging belongs to slow charging, plugged in the 220V AC socket to charge, because the battery is not able to accept AC charging, so first convert the 220V AC power to DC power and then boost to the charging voltage of the battery, such as 500V DC, and then use the 500V DC power to charge the battery.
merit
The charging current and power of slow charging are relatively small, which is good for battery life, and the charging cost is low when the electricity consumption is low.
shortcoming
The charging time is too long, generally it takes 5~8h.
2. The impact of fast charging and slow charging on the life of power batteries
In general, slow charging of electric vehicles will last longer than fast charging. In the case of fast battery charging, it will accelerate the polarization of the battery cell and affect the battery life. In addition, fast charging will increase the battery temperature, and lithium precipitation will reduce the critical temperature. Under internal and external conditions, it is easy to lead to thermal runaway, causing spontaneous combustion of the battery, and causing potential safety hazards to the vehicle. The main reasons are as follows:
1. Fast charging will accelerate the polarization of the battery cell. Polarization is when a large current flows through the battery, and the electrode deviates from the equilibrium electrode potential. Fast charging, as an inducement of high current, is one of the main causes of battery polarization. At present, most plug-in hybrid models on the market are power lithium batteries, although they can withstand higher charging and discharging power, but the factors affecting battery life are still there;
2. Fast charging will lead to lithium precipitation. The battery is relatively hot in the fast charging state. I believe you should have a general understanding of mobile phone fast charging, in the state of fast charging, the temperature of the positive electrode is much higher than that of the negative electrode, and the maximum temperature difference can reach more than 10 degrees.
Although the battery thermal management system of car companies requires the temperature difference to be less than 2 degrees. However, when the cathode temperature is too low, lithium precipitation can still occur, and lithium precipitation will greatly reduce the critical temperature (i.e., the maximum withstand temperature of the battery). As a result, fast charging increases the battery temperature, and lithium precipitation lowers the critical temperature.
Under internal and external conditions, it is easy to lead to thermal runaway, which is what we often call spontaneous combustion of batteries. In addition, the lithium precipitation process leads to a decrease in lithium ions, which ultimately leads to a decrease in battery capacity, which in turn affects battery life.
However, this situation is not too much to worry about. This condition is not irreversible (with the exception of lithium iron phosphate batteries). After a short break in the battery after a quick charge, the lithium metal will turn back to lithium-ion and the critical temperature will return to normal. Generally speaking, the life of new energy slow charging is longer than that of fast charging. Fast charging is not impossible, but it is recommended to practice daily slow charging and emergency fast charging to minimize the damage of fast charging to the battery.
However, according to the actual use of the car owner data, the battery life of new energy vehicles using fast charging and slow charging, there is no obvious difference in comparison, the current new energy vehicles are used ternary lithium batteries and lithium iron phosphate batteries, the life of the two batteries is 2000 times and more than 1000 times of charge and discharge cycles, and the actual service life can exceed 8 years.
A 2020 BYD Han EV owner said that his pure electric car has traveled nearly 40,000 kilometers since it was purchased in 2020, and most of the time it was charged with fast charging, but basically there is no battery life attenuation, and the actual range of the vehicle now fully charged is almost the same as the full battery range when the vehicle was first bought in 2020.
In fact, most of the new energy vehicle owners are mainly fast charging, the efficiency is much faster than slow charging, the impact on battery life is actually minimal, even if the battery pack really has abnormal life attenuation, it can also be replaced by the manufacturer's warranty, now most of the new energy models of the battery pack are the first owner of the lifetime warranty, or 8 years 160,000 kilometers of warranty.
3. The impact of bad charging habits on battery life
In fact, what really has an impact on battery life is bad charging habits, which are as follows:
1. Not charging in time: electric vehicles should be charged in time before the power is less than 20%, otherwise the battery will be overdischarged, which will directly affect the service life of the battery;
2. Frequent full charge: Frequently filling the battery of an electric vehicle will also lead to overcharging the battery, which will reduce the life and capacity of the battery over time;
3. Non-standard charging: If you often use air conditioning and other electrical equipment when charging the vehicle, it will increase the load inside the power battery and shorten the life of the battery.