Dynamic charging lithium battery performance evaluation index summary

Dynamic charging lithium battery performance evaluation index summary

The lithium-ion battery monomer consists of positive and negative, electrodes, electrolytes, and diaphragms, which constitutes a basic structural unit of battery module and battery pack.. Battery as an electrochemical power supply natural voltage, internal resistance, capacity, energy, power and other characteristic parameters.

In the power lithium-ion battery system, each parameter can characterize the different performance of the system, and the various parameters of the lithium-ion battery this article. The lithium ion battery monomer lithium ion battery monomer consists of positive and negative, electrodes, electrolytes, and membranes, and is a basic structural unit that constitutes a battery module and a battery pack..

Battery as an electrochemical power supply natural voltage, internal resistance, capacity, energy, power and other characteristic parameters. People are important for two aspects, I hope to measure and evaluate the parameters of the battery..

One is to achieve the purpose of active control, for example, the battery cell voltage is inconsistent, so that the system energy storage capacity is lowered, if it can actively adjust the monomer voltage of the two poles, the effect of amplifying system capacity can be enlarged.. The other is for safety reasons, the parameters of the battery have its fixed range, detect battery parameters, implement monitoring their boundaries, can play the use of battery security status.

The voltage monomer voltage is important depends on the type of the monomer positive and negative electrode material, and the general cobalt acid lithium, the three-dimensional positive electrode is fitted with the graphite negative electrode to obtain a full charge voltage of about 4.6V, while lithium iron phosphate can only reach 3.6V.

. The voltage here should be that the potential should be based on the material properties, and the potential value is equal to the battery opening voltage after standing for a long time..

The single-end voltage in the closed loop is the voltage value we detected by the external instrument, and its numerical value is equal to the battery power to reduce the internal resistance of the battery.. The internal resistance of the battery is not constant, which will be changed by a variety of factors, and these will be said in the following section.

. Continuing the voltage, the monomer voltage is changed by the material decision, and it will change with the amount of charge of the charge, and it is a corresponding relationship. Therefore, in many cases, the battery load capacity (SOC) that cannot be directly simply measured is often Speech by battery open circuit.

The degree of activity of the monomer voltage and the internal active substance of the battery is related to the temperature of the active activity, and the high low of the monomer voltage can also be affected within a small range.. The higher the monomer voltage, the more energy containing the battery contains, and therefore, in ensuring safety, improve the single voltage upper limit value is a technical route to improve system energy density.

. Internal lithium-ion battery, lithium ion moves from a polar to another, and the factors that hinder ion movement are commonly formed into internal resistance of lithium-ion batteries..

Its important part includes physical internal resistance of conductive members; an inherent impedance of electrochemical substances such as motor materials, diaphragms, and electrolytes; the interior of the battery is interrupted to lithium ion motion in the battery; these three are commonly constituted Internal resistance. The internal resistance is most sensitive, the internal resistance value can change significantly at different temperatures..

The battery performance decreases at low temperatures, one of its important reasons is caused by the temperature of the battery under low temperature.. The lithium-ion battery is used as a power source, from the outside, the internal resistance is definitely, the better.

. Especially in the case of power applications, small internal resistance is necessary..

The capacity of the capacity of lithium ion battery, the capacity of the measured amount, is the maximum amount of power that can be charged and released within the highest lowest voltage range of the battery.. The capacity of the monomer can be measured by charge and discharge before being mounted on the vehicle.

. Once you get on the bus, the battery capacity can only rely on algorithm estimation..

In the battery management system BMS, accurately estimating that the battery charge state SOC is an important indication of its design level.. The current practice is about the dynamic working conditions, the integral of the circuit current, in the non-working state, the battery is used to open the circuit voltage.

. Other ways, although there are many kinds, but not stability is not too large, and it is not very common to be applied to batch..

The capacity of the monomer is obviously affected by the degree of aging. Everyone understands that when the capacity decays to a limit value is when the battery is eliminated, it can be seen that both have absolute correlation..

Second, the capacity also receives the temperature, low temperature, the activity of active material is decreased, and the ion can be supplied, and the capacity will inevitably fall.. Power here the power, accurately, should be a specific power, is a monomer’s charge and discharge power capacity or unit quality or charge and discharge power capability of unit volume cells.

. Whether the lithium-ion battery can perform high power charge and discharge, this has been decided when it is completed..

It is also a lithium iron phosphate material or a three-dimensional material. It is used to modify the active material structure, the electrolyte properties, and electrode SEI film properties, and the electrode SEI film properties can be adjusted to adjust the active material structure, electrolyte properties, and electrode SEI film properties..

Generally, power performance and energy density often cannot coexist, the same material, pursue high power, then partially sacrifices the energy density. Once the battery is produced, its reasonable maximum charge and discharge current has been determined, in addition to adjusting the battery heat dissipation conditions, it is possible to change its maximum charge and discharge power, and there is almost no further adjustment..

In addition to the power, there are several parameters that are more equivalent to unit quality or volume.. The specific capacity, the capacity of energy volume is the capacity of the capacity, the mass ratio capacity is the capacity divided by mass.

. From this extending, the battery cost is brought to the unit capacity, that is, discuss the price from the battery charge and discharge capacity: battery cell capacity cost performance is the price specific capacity, that is, the battery can be released by the unit price..

However, this is generally used in this way.. Similarly, the battery monomer is more energy than the energy of energy, that is, the energy of the unit, the energy that can be discharged; the volume ratio energy, the energy that the unit volume of battery or active material can be released; the price of energy prices It is a relatively universal way in the industry, talking about battery price, how much is 1KWH.

The lithium-ion battery module battery module is combined in parallel with a number of battery cells, which is an element that constitutes a battery pack.. Battery modules are rarely evaluated separately in actual operation, and occasionally, their voltage values ​​are detected.

. In fact, people tend to see modules as a big battery. Different, the module has a monomer consistency problem, and its internal battery voltage difference is the focus of the balanced function.

. The performance of the battery module is often subject to the minimum battery cells in the battery module, and it is important to reflect this indicator of the capacity..

At the time of charging, the monomer with high voltage is first full; when discharging, the battery low is first.. And it is likely that these two batches are not the same.

. Therefore, the consistency of the module internal battery parameters has an decisive impact on the performance of the module..

Consistency, a parameter of the module level than the monomer. This parameter will be filtered by the module to ensure that the cells will be filtered through various means; the module production is completed, the consistency is an important indicator of its acceptance; during operation, it can only rely on BMS equalization. guarantee.

Lithium-ion battery system battery pack is generally constructed in series by modules. In addition to all parameters of the inheritance module, the battery pack determines the voltage platform of the electric vehicle power system, it is a very important parameter..

There are still several indicators involved in the battery pack to be continuously monitored.. Battery pack output positive and negative pair resistance, system leakage current, high voltage interlock signal, maximum temperature, system maximum temperature difference, system maximum temperature rise rate, system maximum single voltage, etc.

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