What can be done to improve the consistency of power lithium batteries?

The battery in the process of charging and discharging voltage is the comprehensive reflection of battery state of thermodynamics and kinetics, both affected by the influence of battery production process conditions in various processes, and the battery charge and discharge current, temperature, time, and in the process of using in the process of accidental factors resulting in individual batteries in the battery voltage value can't be exactly the same.

Improvement measures

1, the production process measures, battery companies control the consistency of all kinds of materials;Monitoring the rheological properties of paste, not size, length of time guarantee pulp during coating rheological property is the same;Coating parameter monitoring, especially the lithium iron phosphate slurry, due to the lithium iron phosphate grains finer, pulp processing performance is poor, should be paid attention to during coating coater go slow speed;The reasonable of pulp viscosity detection;A visual inspection of pole piece;To eliminate defective pole piece;Pole piece weighing;Liquid injection before and after the poor quality of the battery;To temperature;Humidity control;Establish standards for all kinds of raw materials, in strict accordance with the standard of raw material inspection and storage;The consistency of the production process control;Consistency for fine control of production process;The technological process according to statistical process control (SPC);To ensure that every process within the prescribed limits of tolerance;To ensure that the process capability index, which follow the production parameters of normal distribution.

2, set of process measures, ensure the battery pack with unified specification, type of battery, ensure the quality of the battery factory especially the consistency of the initial voltage filter condition: voltage;Internal resistance.Battery into data;Consistency evaluation method has a lot of, at present the most commonly used is very poor coefficient method, the standard deviation coefficient method and threshold method.Combining with clustering analysis, use the set time interval by each testing point form the shape of the battery charge and discharge curves for scientific classification, distance, area, so as to determine the consistency of the battery.

In capacity or voltage threshold, on the basis of the charge and discharge curve shape curve, the distance between curve to calculate the area and so on, can reflect curve consistent parameters selection decision.Matching curve is close to in the process of charging and discharging, smaller relative distance, curve around the area is lesser, smaller batteries to match differences between groups, so as to realize the optimal consistent with group.

3, battery balanced management, from the point of view of battery management system, in the process of the battery pack using testing single battery parameters, especially the electric cars stopped or driving voltage distribution in the process, master single cell inconsistency development regularity in battery, the battery parameters of extreme adjust or change, in order to make sure the battery parameters not consistency increases with time.As far as possible to avoid the battery charging, prevent battery deep discharge.

Ensure the battery good use environment, keep constant temperature, reduce vibration, ensure that water, dust and other pollution batteries column.On energy management and strategy at the same time, the introduction of practical battery and energy management system, formulate reasonable battery equilibrium strategies, active intervention and reduce the inconsistency of the battery.

4 battery, battery thermal management process, the difference of the factors such as internal resistance, battery arrangement will appear in the process of charging and discharging its temperature and environmental temperature difference, this will directly lead to the output performance differences.The battery thermal management function is keeping the working temperature of the battery pack in the battery, the optimal operating temperature range.Ensure the battery temperature condition between consistent, thus to ensure the consistency of the battery parameters.(battery in different temperature condition is different, the life of a temperature rise every 10 ℃ its degradation speed is double)

5 in energy management, control strategy, the output power to allow the case, try to reduce the depth of the battery discharge.Lithium ion batteriesIn the depth of discharge under the condition of consistency, the service life of the battery pack can also be reduced.As far as possible to prevent the battery deep discharge at the same time, avoid the battery charging.After the system has the equalization circuit can prevent individual battery charging, appropriate to reduce charging termination voltage, can prolong the cycle life of the battery pack.

6, other daily maintenance process, use process for the measurement of low capacity of the battery for maintenance charge, to restore its performance.Maintenance interval time of the battery pack for small current charging, promote the balanced and performance of the battery pack itself.Use environment, ensure the battery good use environment, reduce vibration, avoid water, dust and other pollution batteries column.The content, generally it is difficult to use in the car, to be used also need battery system and the controller to achieve.

Conclusion: to improve the consistency of the battery is a system engineering, need battery design, production, quality control, application and maintenance aspects of mutual consideration.

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