For consumers, the most concerning topic when purchasing new energy vehicles is their range. Now, with the continuous upgrading of technology, the range of ordinary electric vehicles is also increasing, reaching the level of 400-500 kilometers. In addition to battery life, another factor that affects consumers' decision to purchase a car is the charging speed.
Usually, cars are labeled with "slow charging time" and "fast charging time", with fast charging time being the biggest competitive point among major car companies. The shorter the fast charging time, the better sales and higher attention. Since fast charging is so good, why slow charging? Although fast charging can shorten the charging time, it also causes significant damage to the battery. Isn't it surprising that fast charging is actually harmful to batteries? Today, let's talk about this topic.
The difference between slow and fast charging of car batteries:
Firstly, before addressing this issue, let's understand the difference between slow charging and fast charging. We all know that slow charging uses alternating currents, and the time to fully charge is usually 6-8 hours. In this charging mode, the battery suffers the least damage. Compared to slow charging, fast charging is an emergency charging method that uses high-power direct current (also known as AC fast charging). This direct current charging voltage is generally greater than the battery voltage, and a large number of current ions will flow from the positive pole to the negative pole of the battery at a very fast and efficient speed, thus completing the process of fast charging.
The principle of fast charging is similar to a small bottle that is supposed to be filled with the smallest amount of water. To reduce time, if you open it to the maximum, of course, you can fill a lot at once. However, such a large amount of water also has a significant impact on the bottle. In other words, in the case of long-term rapid charging, the actual voltage that the battery bears is very high, and in such a high voltage state, the battery will definitely be affected.
What is the impact on fast charging of Lead–acid batteries and ternary lithium batteries?
After discussing the difference between slow charging and fast charging, we still need to have an understanding of the battery. At present, the batteries of electric vehicles are generally lithium batteries and lead-acid batteries, and different batteries have different power generation mechanisms and sensitivity to rapid charging.
For example, when charging lead-acid batteries, the internal electrolyte will gradually react and decrease, ultimately leading to a gradual decrease in battery capacity and a decrease in battery endurance. Although slow charging can also lead to a decrease in battery capacity, the slower speed also causes minimal damage.
Having finished talking about lead-acid batteries, let's take a look at the new energy vehicles on the market now. Most of them use ternary lithium batteries, which are characterized by light weight and high power. But there is also a certain disadvantage, that is, if Thermal runaway occurs in the use process, it is easy to cause fire and explosion. To put it bluntly, when the vehicle is fast charging, it will momentarily input a relatively large amount of current into the battery, which will affect the battery's restoring ability. As the battery's restoring ability decreases, the battery decay rate of the car will increase, which in turn affects the battery's endurance and overall performance.
At the same time, the charging and discharging rate of lithium batteries is also a matter of concern. The battery with a Nameplate capacity of 100Ah is charged and discharged with 20A, and the charge and discharge rate is 0.2C. Generally speaking, the charging current of lithium batteries is set between 0.2C and 1C. The higher the current, the faster the charging. However, at the same time, the more severe the heating phenomenon of the battery, and even lead to spontaneous combustion.
The role of the BMS Battery management system on batteries:
Although there are certain hazards to fast-charging batteries, we don't have to worry too much. Because, in order to reduce the damage of fast charging to the battery, engineers have invented a very important component - the BMS power management system. For electric vehicles, BMS is the core component of fast charging, and its main function is to intelligently manage and maintain each battery cell, prevent overcharging and discharging, extend battery life, and monitor battery status
Simply put, BMS adopts intelligent control algorithms to adjust the charging current pulse width, interval time, and discharge current pulse based on the current state of the battery, modulate appropriate current and voltage to complete charging, reduce the damage to the battery caused by fast charging as low as possible, so the damage can be ignored within a limited time.
Generally speaking, any battery that uses fast charging will damage the battery. However, if the battery density, material, temperature, and Battery management system of the electric vehicle is well designed, the damage will be within a reasonable range. In order to prolong the battery life, try to use fast charging as little as possible and avoid overcharging. To protect the battery, it is better to charge more slowly.
At the end of the article, I would like to share with you a little knowledge on extending battery life. If conditions permit, we try to use slow charging to minimize battery damage. Occasionally traveling on weekends or driving long distances, using fast charging two to three times a week is not a bad thing. In addition, if conditions permit, it is best to ensure that the vehicle is fully charged once a month, in order to facilitate the long-term battery life.
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