Want to ask, what is the efficiency of charging and discharging lithium batteries 5

Research on electric vehicle batteries.

Commonly used types, the charging and discharging characteristics of lithium batteries are as follows:

1) The first stage of constant current should be used for charging, and the voltage should rise to the constant voltage. The use of constant voltage charging can increase the capacity of manganese lithium battery by about 20%.

2) The usable capacity of lithium battery is recommended to be 85% of the nominal capacity when designing, which is safer. It is charged and discharged with a current of 1C, and the usable capacity is 90%. The current is reduced to, typically up to 100%.

3) When the lithium battery is discharged, the discharge capacity of the first cycle is much smaller than the charging capacity. This is because during the first cycle of discharge, the carbon electrode potential drops from the open-circuit potential to the electrochemistry of the process, mainly the surface groups and the solvent.

Restore. Only when the electric potential decreases the thermodynamics of lithium carbon compounds.

potential, before the intercalation reaction of lithium begins. Since the reduction of surface groups and solvents is an irreversible process, with the charge-discharge cycle, the reduction of solvents generates a thick passivation film on the carbon surface, which effectively prevents further reduction of solvents, while lithium ions can carry out electrochemical intercalation and detachment reactions through this electronic insulating film. Therefore, from the second week of cycling, the charging and discharging efficiency quickly approaches 100%.

The first cycle is done before the battery leaves the factory, so users don't have to worry about this issue.

For the first time, there is a loss, and the charging and discharging efficiency behind it is basically in, but the battery has attenuation, and the charging and discharging efficiency of lithium batteries with different cathode materials is a little different!

There is a limit to the number of times a lithium battery can be charged and discharged. In general, the cycle life of lithium batteries is between 300-500 times. Cycle life refers to the number of charge-discharge cycles of a battery between a full charge and a full discharge.

After exceeding this number of times, the capacity of the battery began to decrease, and eventually Luling led to the end of the battery's life.

The cycle life of a lithium battery depends on many factors, including the type of battery, how it is used, temperature, and charge/discharge rate, to name a few. For example, high temperatures can reduce the life of lithium batteries, while low temperatures can extend the life of lithium batteries. In addition, too fast charging and discharging rates can also have an impact on the life of lithium batteries.

In order to prolong the service life of lithium batteries, we can pay attention to some of the following things. First of all, try to avoid keeping the battery in a high or low temperature environment, and keep the operating temperature of the battery between 20-25; secondly, reduce the use of fast charging and fast discharging, and select the appropriate charging and discharging rate; Finally, the deep charging and discharging of the battery is carried out regularly to balance the effect of the battery.

When charging daily, try to keep the lithium battery charge state between 30-80%, and avoid overheating, overcharging or over-discharging. In addition, when lithium batteries are not used for a long time, Ye Xiaomin should follow a certain maintenance process, regularly charge and discharge the battery to ensure the normal use of the battery.

It should be noted that the above mentioned measures cannot completely avoid the aging of lithium batteries or improve the service life of lithium batteries, but they can effectively extend the service life of lithium batteries. Through reasonable use, we can maximize the performance of lithium batteries, prolong the service life of lithium batteries, and reduce environmental pollution. <>

The service life of lithium-ion batteries is only two to three years. Lithium-ion batteries are generally capable of 300 500 charges. It is better to partially discharge the lithium-ion battery, not completely, and try to prevent frequent full discharge.

Once the battery is off the production line, the clock starts moving.

1.Charge q = iδt = p u)·t = 130w = 31621 c (coulomb).

2.Current=6400mA? Mah bar.

q = iδt = = 23040 c

t = w/p = ui/p = =

Explanation: Battery energy e = uit, mah is the unit of charge, and wh is the unit of energy.

t = e/p

The charge-discharge rate of lithium-ion batteries determines how quickly a certain amount of energy can be stored in the battery, or how quickly the energy in the battery can be released.

The positive and negative electrodes and electrolytes will affect the charge-discharge rate performance of lithium batteries. With the increase of the number of charging and discharging times, the capacity of lithium batteries will become less and less, which is directly reflected in the worse and worse performance of lithium batteries.

The charge-discharge rate performance of lithium batteries is directly related to the migration ability of lithium ions at the positive and negative electrodes, electrolytes, and the interface between them, and all factors that affect the migration rate of lithium ions (these influencing factors can also be equivalent to the internal resistance of the battery) will affect the charge-discharge rate performance of lithium-ion batteries.

In addition, the heat dissipation rate inside the battery is also an important factor affecting the performance of the rate, if the heat dissipation rate is slow, the heat accumulated during charging and discharging at the large rate cannot be transferred, which will seriously affect the safety and life of the lithium battery.

The larger the C number, the faster the power can be released, sometimes a large current is needed when playing model aircraft (such as take-off, sudden acceleration, etc.), if the battery C number is small, the performance in this area is poor, the power is insufficient, the larger the C number, the more expensive the general model aircraft should specify the C number, and mobile phone lithium batteries, 18650 and other batteries can not be used to play with models, because the battery generally has overcurrent and low voltage protection.

Rate C refers to the current value required when the battery discharges its rated capacity within a specified time, and it is equal to the multiple of the rated capacity of the battery in terms of data value

For example, a 1200mAh battery represents 240mA (1200mAh rate), and 1c represents 1200mA

The discharge rate of the battery superscript is the maximum discharge rate given by the factory. We can judge the maximum current that the battery can withstand when it continues to work based on the C value.

For example, if a 2000mAh 3C battery is used, then we can know that the maximum current that this battery can withstand in 1 hour is 6000mA

For example, if the theoretical specific capacity of Fe3O4 is 924 mAh g, then for Fe3O4 lithium batteries, 1C is equal to 924 mA g. This c-value is not fixed and depends on the battery material.

The higher this value when charging and discharging, the faster the battery is charged and discharged. However, when charging and discharging at high current density, the specific capacity of the battery will generally decrease, and the higher the c, the more obvious it is. So, in the case of ensuring the battery capacity, of course, the bigger the c, the better.

1.Acquired factors that lead to the self-discharge rate of lithium power batteries.

In different use environments, application states and life stages, the self-discharge rate of lithium power batteries will also be different.

1) Temperature. The higher the ambient temperature, the higher the activity of the electrochemical materials of the lithium power battery, and the more intense the reaction of the cathode materials, anode materials, and electrolytes of the lithium power battery, resulting in more capacity loss in the same time period. The chemical self-discharge of lithium power batteries is more significant at high temperatures, and it is more effective to use high-temperature storage to judge the self-discharge of lithium power batteries.

2) External short circuit. The external short circuit of the lithium power battery placed in the open circuit is mainly affected by the degree of air pollution and air humidity. This is the reason why lithium power batteries will strictly require the laboratory environment and humidity range when conducting self-discharge characteristic test experiments.

High air humidity can lead to an increase in electrical conductivity, while air pollution mainly refers to the fact that pollutants may contain conductive particles, which will increase the conductivity of the air.

3) Charge. By comparing the influence of lithium battery charge on the self-discharge rate, the general trend is that the higher the charge of lithium power battery, the higher the self-discharge rate. That is, the higher the charge of the lithium power battery, the higher the positive potential and the lower the negative potential.

In this way, the stronger the positive oxidation and the stronger the negative reduction, the more intense the side reaction.

4) Time. The longer the lithium power battery loses efficiency with the same power and capacity, the more power and capacity will be lost. However, the self-discharge performance is generally used as an indicator for the comparison of different lithium battery cells, that is, under the same preconditions and at the same time, the comparison is made, so the role of time can only be said to affect the "self-discharge amount".

The physical micro-short circuit of lithium power battery has an obvious relationship with time, and long-term storage is more effective for judging physical self-discharge.

5) Circulation. The cycle will cause the internal micro-short circuit melting of the lithium power battery, so that the physical self-discharge will be reduced, so if the self-discharge of the lithium power battery is mainly physical self-discharge, the self-discharge after the cycle will be significantly reduced; If the self-discharge of lithium power battery is mainly chemical self-discharge, there is no obvious change in self-discharge after cycling.

2.The impact of self-discharge on lithium power battery modules.

After the storage of lithium power batteries with inconsistent self-discharge for a period of time, the SOC will have a large difference, which will greatly affect the capacity and safety of the lithium power battery module. The research on the self-discharge of lithium power batteries is helpful to improve the overall level of lithium power battery packs, obtain higher life, and reduce the defective rate of products. The impact of self-discharge on the lithium power battery module is as follows:

1) The self-discharge of lithium power battery will lead to the reduction of the capacity of lithium power battery module during the storage process.

2) The self-discharge of metal impurities of lithium power batteries will lead to the blockage of the aperture of the separator, and even puncture the separator to cause local short circuits, endangering the safety of the lithium power battery module.

3) Due to the inconsistent self-discharge of lithium power battery cells, the SoC of the cells in the lithium power battery module will be different after storage, resulting in the performance of the lithium power battery module deteriorating. And it is easy to lead to the overcharging and over-discharging of the battery cells in the lithium power battery module.

Every day the voltage drops volts, and milliamps are lost every day.

Different active substances, the size of the battery's charge is different, and the self-discharge rate is not the sameFor lithium cobalt oxide with a small self-discharge, the measurement standard has a parameter called "k value", k value = voltage drop 1000 days between tests. The meaning of the K value is the value of the average daily voltage drop, and the K value is generally less than when the initial test voltage is used.

For example, when the initial voltage of a lithium battery is 100 days, its voltage drop = k value Number of days between tests 1000=

That is, voltage =

The voltage drops every day.