Author ：Iflowpower – Portable Power Station Supplier
First, a lithium-ion battery that is too energy is too energy, encounter accidents, causes thermal out of control, and the internal radical response in the battery. In a short period of time, too many energy is nowhere to release, it is very risky. Especially in safety skills, management can not develop, every battery capacity should be restrained.
Secondly, the energy wrapped up by the lithium-ion battery housing, once presented accidents, firefighters, fire extinguishing agents can not touch, strength is not from the heart, can only isolate the scene when the attack is, the battery is back, the energy burning is stopped. Of course, for safety reasons, the lithium-ion battery at the time has planned multiple safety techniques. Take a cylindrical battery as an example.
Safety valve, when the internal reaction of the battery exceeds normal size, the temperature rises, and accompanied by the generation of sub-reverb gas, the pressure arrives at the planned value, the safety valve is actively opened, discharged from the pressure. When the safety valve is opened, the battery is completely invalid. Thermistor, some batches are equipped with a thermistor.
Once an overflow is present, after reaching a certain temperature, the resistance has slightly increased, the circuit current drops, the further increase of the temperature of the obstruction. The fuse, the battery is equipped with a fuse having an overflow-fuse function, once the overcurrent risk, the circuit is disconnected, and the attack of the warming.
At this time, it is necessary to face a problem and commonality. Our daily experience is that the two dry batteries, the positive and negative is connected, and the flashlight can glow, and whoever does not work together. And the large-scale use of the lithium-ion battery, the situation is not so simply.
Lithium-ion battery parameters do not share the capacity, internal resistance, and open voltage. The uncommon battery string is used together, it will present the following problem. 1) The capacity loss, the cell monomer constitutes a battery pack, the capacity is in line with the principle of the wooden bucket, the capacity of the worst the battery decides the entire battery package.
In order to prevent the battery over-filled, the logic of the battery is allowed to: discharge, when the lowest monomer voltage reaches the discharge cutoff voltage, the entire battery pack stops discharge; when charging, when the highest monomer voltage touches the charging cutoff , Stop charging. Take two batteries in series. One battery capacity 1c, another capacity as long as 0.
9c. Series relationship, two batteries pass the same giant current. When charging, the battery with small capacity must be fully overflow, reaching the charging deadline, the system no longer continues to charge.
When discharge is discharged, the battery is small, and it must first put the light, and the system can be used, and the system should stop discharge. In this way, the battery cells with small capacity are always overcharged, and the battery having a large capacity has always been used in part capacity. The total capacity of the entire battery pack is in a portion of the idle state 2) Lost, similar, the battery pack, the battery core is determined by the shortest amount of life.
Very large, the shortest battery, the shortest battery, is the small battery cell. Small capacity battery, each time is full of overproduction, extensive, greatly arrived at the number of birthday. End of the number of batches of battery cells, a set of soldered batches, followed by the world.
3) Internal resistance increases, different internal resistance, flowing through the same current, the internal resistance of the electric cell is more compared. The battery temperature is too high, and the constitutional deterioration speed is accelerated, and the internal resistance will further increase. Internal resistance and temperature rise, constitute a pair of negative feedback, so that high internal resistance battery is deteriorated.
The above three parameters are not completely independent, and the internal resistance of the degree of aging is relatively large, and the capacity attenuation is more. Separately explain, just want to express it clearly of their respective influence. How to deal with the failure of the unsocvisible cells, it is made in the process of processing, deepened during the application process.
The battery in the same battery pack is weak, and it is weak. The degree of discretity between the arguments between the unit cells, and increases the degree of aging. At that time, the engineer could not work together with the monomer battery.
Monomer battery sorting, after the group, it is time to handle, and a small number of non-common time battery processing is balanced. 1) Size of different batches of batches, theoretically do not put together. Even if the same batch is selected, put the parameters in a battery pack in a battery pack, in the same battery pack.
The purpose of the sorting is to select a battery similar to the parameters. The method of sorting has been discussed for many years, the primary division of static sorting and dynamic sorting two categories. Static sorting, selection of characteristic parameters such as the open circuit voltage, internal resistance, capacity of the battery, select policy parameters, introduced statistical algorithms, set selection specification, and finally divide the same batch of electric cores into several groups.
Dynamic selection is the selection of the characteristics exhibited during the charge and discharge process. Some select the constant current constant pressure charging process, and some of the pulse shock charge and discharge process, some compare itself between the charging and discharge curve relation. The dynamic combination is selected, and the preliminary grouping is made with static selection.
On this basis, the dynamic selection is performed, which is more than the group, but the accuracy is higher, but the cost will rise accordingly. This is a small manifestation of a dynamic lithium-ion battery processing scale. Large-scale shipments make manufacturers to make more sorted sorting, getting a battery pack.
If the output is too small, there are too many packets, and a batch cannot be equipped with a battery pack, and the good method cannot be displayed. 2) Thermal shall not be the same as the internal resistance, and the heat is not the same. The joining of the thermal system can adjust the temperature difference of the entire battery pack to keep it in a smaller scale.
Generate more thermal cells, still temperatures, but will not pull the distance from other cells, and the level of deterioration will not present significant distance. 3) Equilibrium the uncompair of the module, some electrical core end voltage, always in advance, arrive at the control threshold, resulting in small capacity. In order to solve this problem, the battery handling system BMS planned a balanced function.
A certain core is the first to reach the charging cutoff voltage, and the rest of the electric core voltage is significantly lag, the BMS starts charging equalization, or the access resistance, the part of the high voltage cell, or transfer the energy transfer, put it Low voltage battery. Thus, the charging deadline is released, the charging process resumes, and the battery pack is charged into more power.
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