Method for evaluating self-discharge consistency of lithium iron phosphate battery

A lithium iron phosphate battery and evaluation method technology, applied in the direction of measuring electricity, measuring electrical variables, measuring devices, etc., can solve the problems of poor voltage consistency, different rebound degree and speed, etc., achieve good voltage consistency, improve self- Efficiency of discharge rate and ease of data analysis

Active Publication Date: 2012-06-20
HEFEI GUOXUAN HIGH TECH POWER ENERGY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, due to polarization, the battery voltage rebounds after discharge, and the degree and rate of voltage rebound between different batteries are different, resulting in poor voltage consistency before the battery discharge state is put on hold, and the voltage after being put on hold is even higher than the voltage before being put on hold. There is also a phenomenon that the voltage difference is a negative value, so this method of using the discharge state voltage difference to evaluate the consistency of the battery also has drawbacks.

Method used

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  • Method for evaluating self-discharge consistency of lithium iron phosphate battery
  • Method for evaluating self-discharge consistency of lithium iron phosphate battery
  • Method for evaluating self-discharge consistency of lithium iron phosphate battery

Examples

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Embodiment 1

[0022] Embodiment 1: The present invention provides a method for evaluating the self-discharge consistency of a lithium iron phosphate battery by using the voltage difference at a lower state of charge. The technical solution is: a method for evaluating the self-discharge consistency of a lithium iron phosphate battery, comprising the following steps:

[0023] (1) After discharging multiple batteries, perform constant current charging to the specified voltage; the specified voltage is 2.8V-3.2V, preferably 2.9-3.1V, and the state of charge of the battery corresponding to this voltage is relatively low, about 3% -20% as in figure 1 , and then carry out constant voltage charging at the specified voltage until the cut-off current is 0.01C-0.03C;

[0024] (2) Measure the open circuit voltage OCV1 after the battery is charged;

[0025] The measurement time of OCV1 in this step is 2-24 hours, preferably 8-16 hours after the battery is charged.

[0026] (3) Put the battery in a hi...

Embodiment 2

[0033] Charge 1000 lithium iron phosphate batteries with a rated capacity of 10Ah at a constant current and constant voltage at a current of 3500mA after discharge. The cut-off current is 200mA; measure 0CV1 8 hours after the battery is charged; then place the battery in a high-temperature environment of 35°C for 10 days; measure the open-circuit voltage OCV2 of the battery after being placed in a high-temperature environment; calculate the voltage drop of the battery ΔV=OCV1- OCV2 or the voltage drop K=(OCV1-OCV2) / t per unit time; calculate the average value X and standard deviation s of ΔV or K values ​​of 1000 batteries, and delete all those exceeding the control limit of [X-3s, X+3s] point, re-analyze until all points are within the control limit range; according to the control upper limit finally determined by the above steps, set the upper limit of the specification of the ΔV or K value, and judge that the self-discharge of the battery with the value of ΔV or K within the...

Embodiment 2-3

[0035] Embodiment 2-3 adopts the same processing steps as Embodiment 1, and its specific processing parameters are shown in Table 1.

[0036] Table 1

[0037]

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Abstract

The invention discloses a method for evaluating self-discharge consistency of a lithium iron phosphate battery. The method mainly comprises the following steps of: measuring open circuit voltage after the battery is charged and open circuit voltage after the battery is laid at high temperature under the conditions of constant voltage and constant current; calculating the voltage drop of the battery, a mean value and a standard difference; and determining the upper control limit of the voltage drop to determine that the battery has high self-discharge consistency under the condition that the voltage drop does not surpass an upper specification limit. By the method for evaluating the self-discharge consistency of the lithium iron phosphate battery, evaluation accuracy, high production operability and obvious practical meaning are achieved, and the grouping consistency of the lithium iron phosphate battery is effectively improved.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to a method for evaluating the self-discharge consistency of lithium iron phosphate batteries. technical background [0002] Lithium-ion batteries have become the most important energy storage devices in the development of electric vehicles due to their high energy density, long cycle life, and environmental protection. In the actual process of applying lithium-ion batteries to electric vehicles, it is first necessary to combine multiple single cells in series / parallel to obtain a high-voltage, high-energy battery pack. Due to the short plate effect, the consistency of the performance of the single battery has become a decisive factor affecting the performance of the battery pack. At present, lithium-ion batteries need to be screened for performance consistency of single batteries before being assembled into groups, and batteries with good consistency are combined int...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R31/36
Inventor 贺狄龙刘爱菊马冬梅张羽
Owner HEFEI GUOXUAN HIGH TECH POWER ENERGY
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