Now electric vehicle batteries are mainly lithium batteries and lead-acid batteries, lithium batteries with its high energy density, small size, light weight, long life electric vehicle lithium battery suppliers and other advantages in the market share is getting higher and higher, but there are many people in the use of lithium batteries there are some misunderstandings, especially charging this, accidentally will cause irreparable damage to lithium batteries!
Incorrect charging conditions or methods will be more likely to damage the lithium battery and reduce the life of the lithium battery. For example: lithium battery charging overtemperature, electrolyte interface (SEI) mode begins to decompose and heat → electrolyte → positive electrode begins thermal decomposition, resulting in gas out and rapid temperature rise → more serious will cause battery explosion. Lithium battery charging overvoltage, lithium metal precipitation, solvent electric vehicle lithium battery price is oxidized, the temperature rises, resulting in a vicious cycle, battery fire, explosion. It can be seen that the poor charging method of electric vehicle lithium batteries will have a serious impact on battery characteristics.
Therefore, about how to charge lithium batteries, let's take a look at the following questions.
First, how to prevent lithium battery overcharge and overdischarge
Because lithium-ion batteries have a high energy ratio, it is necessary to control the phenomenon that the battery cannot be overcharged and over-discharged. Overdischarge will lead to the recovery of the active substance is difficult, if then directly into the rapid charge mode (high current), which will damage the battery, affecting the service life with the possibility of invisible hazards.
Although lithium-ion batteries are currently equipped with protective plates in applications, under normal circumstances, the probability of over-discharge will be very small, but there is no more accurate protection, in the following cases may bring hidden dangers of over-discharge.
1. The protection board fails.
2, long-term placement (5%~10%/ month) self-discharge rate.
Therefore, if there is a more accurate system to monitor and let the owner understand the battery situation in the first time, it is the best way to control the overdischarge of lithium batteries.
Second, how to control the charging current
Taking a single lithium-ion battery as an example, its charging method includes constant current and constant voltage charging, although the charging of large current will shorten the charging time, but it will also cause the battery life cycle to shorten and capacity to reduce, so the appropriate constant current value should be selected for charging.
The following is the relationship between the different current charging and battery capacity of a lithium battery cell, and it can be seen in the following figure that after about 500 charging and discharging cycles, the battery capacity of the small current charging is significantly greater than the battery capacity of the large current charging.
Third, how to control the voltage of constant voltage charging?
As a high energy density battery, overcharge has a great harm to lithium batteries, it may make him expand and leak, more serious will occur spontaneous combustion and explosion, and overcharge is easy to cause the electrolytic substances in the battery to accelerate the reaction and cause the battery life to be shortened, so the accurate constant voltage charging value is very important for lithium-ion batteries.
In order to fully charge, it is necessary to ensure that the accuracy of the constant voltage value and the termination voltage value is within 1%. Taking lithium-ion cobaltate batteries as an example, it is best to be as close as possible to 4.2V, but not more than 4.2V, this high-precision voltage charging method can reduce the dissolution of cobalt, stabilize the layered structure of LiCoO2, so that its coating does not phase change, improve cycle performance, and maintain high capacity.
So even a slight overvoltage will cause two phenomena to change: (a) the initial capacity of the battery will increase; (b) Reduced battery cycle life.
Fourth, why do we need intelligent lithium dog electric vehicle battery management system?
In fact, the battery is very sensitive, charge/discharge, charging current, voltage, temperature, etc. exceed a certain critical value, it is easy to cause permanent damage, as mentioned above, so it is important to control and detect it. Then the intelligent lithium dog electric vehicle battery management system can do this very well, the above variables can be monitored in real time, charge/discharge, charging current, voltage, temperature and other than the battery charging safe range value will remind the owner through the mobile phone battery charging is currently in a bad state, need to make relevant adjustments. This effectively protects the charging safety of the lithium battery and extends the service life of the battery.
In addition, the intelligent lithium dog system can also achieve cell balance, short circuit protection, charging/full charge/low power reminder, etc., to protect the electric vehicle battery! In addition to the above functions, the intelligent lithium dog system also comes with GPS positioning function, which is also very good at preventing electric vehicle theft, so it is necessary to install the intelligent lithium dog system for electric vehicle batteries!
