Charge and discharge method of low temperature lithium battery in low temperature environment, using a battery management system to detect the temperature of the battery in real time; using the battery handling system to read a preset rule, the present rule defines a plurality of consecutive temperature scales, each temperature scale corresponds to a charging cutoff Voltage; the battery handling system compares the detected temperature value of the battery with the temperature scale of the temperature scale, and looks at the temperature scale to which the corresponding charging cutoff voltage is obtained; the battery handling system is announced through the control circuit or the charger. The command manipulation charges the lithium battery pack according to the charge cutoff voltage.
The advantages and positive effects of this technology are: through the cooperation of the lithium battery pack and the handling system, the lithium battery pack can be charged and discharged at low-temperature without external heating, and the phenomenon of “lithium crystal branching” does not occur.
Problems with lithium batteries at low temperatures
Under low-temperature conditions, low-temperature lithium batteries have reduced activity of various active substances, the low reaction rate of battery electrodes, low battery function, low actual charge, and shortened battery operation time.
In the process of low-temperature charging, the lithium battery is very likely to cause lithium ions to be separated at the negative electrode, causing lithium metal crystals, that is, “lithium crystal branches” phenomenon. The formation of “lithium crystal branches” will break the barrier of the battery and cause a short circuit between the positive and negative electrodes inside the battery, which poses a safety problem. Lithium metal reacts with the electrolyte to reduce battery activity and accelerate battery life.
Ways to prevent “lithium crystal branches”
In the prior art, when using a lithium battery, in order to prevent the “lithium crystal branch” phenomenon, generally three methods are selected:
To stop the low-temperature charging of lithium batteries
Obviously, I am not satisfied with the demand for lithium batteries in many fields, especially in the current electric vehicle category. Because of its wide application area, especially in the north of China, the winter climate is relatively cold, and the outdoor temperature can reach -30 °C. Grepow’s existing technology has broken through this limitation and can produce the high performance of discharge at low-temperature, the low temperature shaped battery is able to discharge over 60% efficiency @0.2C at -40°C, and discharge over 80 % efficiency @0.2C at -30°C.
To heat the lithium battery
The second is to heat the lithium battery when the lithium battery must be charged in a low-temperature environment, thereby preventing the “lithium crystal” phenomenon from occurring. Although it is better than the first one in the application, its structure is complicated, the control is difficult, and the high failure rate has always affected the application of low-temperature lithium batteries, especially in the field of electric vehicles.
The battery is fully charged by the small current pulse
The third is to fully charge the battery after a small current pulse in a low-temperature environment. In theory, the problem of low-temperature charging and non-injection is improved, and the electron moving speed in the low-temperature state is greater than that in the formation process of lithium-ion relocation speed. However, the positive and negative electrode matching amount is neglected under low-temperature conditions. The safety problem caused by the imbalance is a kind of “relative overcharge phenomenon”.
Lithium battery charge and discharge method
The problem to be dealt with is the charging and discharging method of the lithium battery to prevent the lithium battery from being charged at a low-temperature to separate the lithium metal. Lithium battery low-temperature charging method: the battery handling system detects the temperature of the battery in real-time; the battery handling system reads a preset rule, the present rule defines a plurality of successive temperature scales, and each temperature scale corresponds to a charging cut-off voltage.
Battery charging and discharging method, according to the battery does not attack the “lithium crystal” temperature scale, to determine the appropriate charge cutoff voltage and discharge cutoff voltage; initially under constant current charging, and when the battery voltage rises to the charge cutoff voltage, Constant voltage charging, real-time detection of the battery temperature, followed by the charging process, the battery temperature gradually rises, the battery temperature reaches another temperature scale, then the corresponding charging cut-off voltage also rises, charging according to the new charging cut-off voltage One rule is performed until the battery is fully charged. Together, the battery charging method can further determine an appropriate charging current according to the temperature scale.