CN104977534A

CN104977534A - Method for estimating state-of-health of battery and device thereof

Info

Publication number: CN104977534A
Application number: CN201410130918.8A
Authority: CN
Inventors: 施昌沅; 阮宪熙
Original assignee: Hongfujin Precision Industry Shenzhen Co Ltd; Hon Hai Precision Industry Co Ltd
Current assignee: Hongfujin Precision Industry Shenzhen Co Ltd; Hon Hai Precision Industry Co Ltd
Priority date: 2014-04-02
Filing date: 2014-04-02
Publication date: 2015-10-14

Abstract

The invention provides a method for estimating a state-of-health (SOH) of a battery and a device thereof. The method comprises the steps of measuring the internal resistance R of the battery; obtaining the voltage drop value deltaV of the battery according to a relational expression deltaV=R*I between the internal resistance R of the battery and the voltage drop deltaV, wherein I is a lower-limit current value which is preset in a using capacity; computing a lower-limit OCV value of the capacitance at this time according to the voltage drop deltaV; acquiring a lower-limit value SOC-1 of the SOC at this time according to a relationship table between the OCV and the SOC of the battery; and acquiring an SOH value according to a relational expression SOH=100%-SOC-1 between the SOH and the SOC-1 of the state-of-charge (SOC) of the battery at this time. According to the method for estimating the state-of-health of the battery, the SOH value is directly computed through the internal resistance of the battery. The method and the device of the invention have advantages of simple method, relatively low cost and short test time.

Description

The evaluation method of cell health state and device thereof

Technical field

The present invention relates to cell art, particularly relate to a kind of evaluation method of cell health state.

Background technology

At present, because people are to the enhancing of the consciousness of environmental protection and the effective and reasonable utilization of the energy, electric automobile that is efficient, energy-saving and environmental protection becomes the development trend of automobile industry.And the focus of industry research is become as the energy storage device-battery of the energy of electric automobile, and certainly, can the health status (State of Health, SOH) of Measurement accuracy battery, the enforcement for the whole control strategy of electric automobile is particularly important.

In order to show the index of the state of the battery of electric automobile, be used the concept of SOH.SOH is the overall performance of reaction cell and discharges the parameter of ability of electric energy under certain condition, and namely under a certain condition, battery total electricity that can discharge accounts for the ratio of battery active volume of newly dispatching from the factory.Along with the use of battery, have many expendable physical chemical factors and cause cell degradation, so that the health degree of battery declines.At present, the SOH of most battery is judged by the ageing state of battery, and the major parameter that characterizing battery is aging comprises the decay of battery capacity, the increase of the internal resistance of cell.

Due to the parameter that the internal resistance of cell is the SOH maximum effect to battery, exist in prior art to utilize and measure the method that internal resistance carrys out the SOH of estimating battery.There is researcher to propose the relation of the SOH of the charged state of internal resistance, temperature, battery (State of Charge, SOC) and battery to be created as table by experiment, then tabled look-up by the internal resistance value of measurement battery and estimate the SOH of battery.But, the process that the SOH of various factors and battery builds table is just needed a large amount of experimental datas to support, means that a large amount of equipment of needs, time and manpower are to carry out the collection of data, considerably increase cost.

Summary of the invention

In view of above-mentioned condition, be necessary to provide a kind of simple and the evaluation method of lower-cost cell health state and estimating device.

An evaluation method for cell health state, comprising: the internal resistance R measuring battery; According to the internal resistance R of battery and the relational expression of pressure drop Δ V: Δ V=R × I, obtain the voltage drop value Δ V of battery, now I is the lower bound current value I preset in use capacity; Open-circuit voltage (Open Circuit Voltage, the OCV) value of electric capacity lower limit is this moment calculated by pressure drop Δ V value; Relation table according to OCV and the SOC of battery obtains SOC lower limit SOC this moment _-1; And according to the charged state SOC lower limit SOC this moment of SOH and battery _-the relational expression of 1: SOH=100%-SOC _-1, obtain SOH value.

A kind of estimating device of cell health state (SOH), comprising: storer, and it stores the corresponding relation of OCV and SOC.Voltage acquisition unit and current acquisition unit, it measures the voltage and current of battery.Controller, when proposing the request of estimating state of health of battery, this controller by voltage acquisition unit and current acquisition unit the voltage and current to this moment battery measure, and send the voltage and current value of the battery of above-mentioned measurement to processor.Meanwhile, controller by the information transmission of the storage of storer to processor.Processor, by the voltage and current data analysis of battery collected, calculates the internal resistance of battery; The pressure drop Δ V that internal resistance causes is calculated according to the internal resistance of the battery determined; Pressure drop Δ V according to the battery determined calculates lower limit OCV value; From described storer, read the corresponding relation of OCV and SOC, and calculate SOC lower limit SOC this moment according to lower limit OCV value _-1; According to SOC _-1 calculates SOH value.

The evaluation method of the health status of above-mentioned battery and device thereof by measuring the internal resistance of battery, and directly by the OCV of internal resistance and battery relation so that estimate the SOH battery this moment.Simply, eliminate the process setting up the various factors of battery and the relation table of SOH, the test duration is short and cost is lower for the evaluation method of cell health state of the present invention and device thereof.

Accompanying drawing explanation

The voltage of battery and the relation curve of electric current when Fig. 1 is electric discharge.

Fig. 2 is the process flow diagram of the evaluation method of cell health state of the present invention (SOH).

Fig. 3 is the relation table of OCV and the SOC of the battery of the evaluation method of the battery SOH shown in Fig. 2.

Fig. 4 is the structured flowchart of battery SOH estimating device of the present invention.

Main element symbol description

The estimating device of cell health state	200
		Storer	210
Voltage acquisition unit	220
		Current acquisition unit	230
Controller	240
		Processor	250

Following embodiment will further illustrate the present invention in conjunction with above-mentioned accompanying drawing.

Embodiment

Below in conjunction with drawings and the embodiments, the evaluation method of a kind of cell health state (SOH) provided by the invention and device thereof are described in further detail.

Refer to Fig. 1, battery capacity is the key factor that battery can keep maximum charge.Brand-new battery capacity is approximately the capacity that manufacturer indicates.But, determine the use capacity that battery has after charging, thus to make battery can perform its predetermined function be vital.Battery uses in the setting of capacity, lower voltage limit 204 is down to 0% foundation as the charged state (SOC) of battery generally can be set, wherein the first curve 201 is open-circuit voltage (OCV) value of battery and the relation curve of electric current, the relation curve that second curve 202 is the lower terminal voltage of battery specific currents electric discharge and electric current, the 3rd curve 203 be after cell degradation specific currents discharge under terminal voltage and the relation curve of electric current.But the excessive or internal resistance of cell of battery discharge procedure electric current rises and voltage all can be caused to conflict ahead of time lower voltage limit, makes to use capacity to decline.In the setting of electric current, can provide the power of target in order to ensure battery in use capacity, therefore can set lower current, once conflict to lower voltage limit 204 under the electric discharge situation being less than or equal to this lower current, the SOC being considered as battery reaches 0%.The present invention, by the relation by OCV and SOC, utilizes the direct estimating battery SOH of the internal resistance of battery.

Refer to Fig. 2, the evaluation method of a kind of battery SOH of the present invention, comprises the following steps:

S101: the internal resistance R measuring battery.Preferably, utilize simple voltage acquisition unit and current acquisition unit, measure magnitude of voltage and the current value of battery.Then, the internal resistance R value of described battery is calculated according to the measured value of voltage and current.Be appreciated that the internal resistance of battery can also utilize AC impedence method to measure, but be not limited thereto.

S102: utilize the internal resistance R of above-mentioned acquisition to be multiplied by the lower bound current value I preset in use capacity and draw the pressure drop Δ V that internal resistance causes.

S103: the pressure drop Δ V of above-mentioned acquisition is added with lower voltage limit V and obtains electric capacity lower limit OCV value this moment.

S104: please refer to Fig. 3, data set up the relation table of OCV and the SOC of battery by experiment.

S105: the relation table that the lower limit OCV value of acquisition substitutes into above-mentioned OCV and SOC can be obtained lower limit SOC value and a SOC _-1 value.

S106: deduct SOC by 100% _-1 value can obtain SOH value this moment, that is:

SOH =100%－SOC _—1。

So just complete the estimation of battery SOH.

Refer to Fig. 4, a kind of estimating device 200 of cell health state, comprises storer 210, voltage acquisition unit 220, current acquisition unit 230, controller 240 and processor 250.

Storer 210, it stores the relation table of OCV and SOC.

Voltage acquisition unit 220 and current acquisition unit 230, it measures the voltage and current of tested battery.Usually, the internal resistance of battery is the summation of the impedance such as direct current resistance, diffusion resistance, and is difficult to detect in real time.Therefore, be suitable for measuring simple direct current resistance component.Preferably, at short notice tested battery is carried out to the measurement of internal resistance, but consider the computing time of hardware and other information, Measuring Time is set to one second.

When proposing the request of health status of estimating battery, this controller 240 by voltage acquisition unit 220 and current acquisition unit 230 voltage and current to this moment battery measure, and send the voltage and current value of the battery of above-mentioned measurement to processor 250.Meanwhile, controller 240 by the information transmission of the storage of storer 210 to processor 250.

Processor 250 is for calculating the internal resistance R of battery by the voltage and current data analysis of the battery collected; The pressure drop Δ V caused by the internal resistance of battery is calculated according to the internal resistance R of the battery determined; Pressure drop Δ V according to the battery determined calculates lower limit OCV value; From described storer, read the corresponding relation of OCV and SOC, and calculate SOC lower limit SOC this moment according to lower limit OCV value _-1; According to SOC _-1 calculates SOH value.

Please again consult Fig. 2 and Fig. 4, now by the evaluation method of battery SOH of the present invention, be applied to the estimating device of battery SOH.When asking the estimation of SOH, controller 240 measures voltage and the electric current of battery by voltage acquisition unit 220 and current acquisition unit 230.After this controller 240 is by measured magnitude of voltage and current value, transfers to processor 250.Magnitude of voltage measured by processor utilizes and current value calculate the internal resistance R(S101 of battery).

When after the internal resistance R completing battery, processor 250 calculates the pressure drop Δ V of battery, and then calculates lower limit OCV value (S102, S103).

Meanwhile, the corresponding relation of OCV and the SOC of storer 210 is transferred to processor 250 by controller 240.Processor 250 calculates corresponding lower limit SOC value by lower limit OCV value.And then by processor 250 by SOC lower limit SOC this moment _-1 calculates SOH value, completes the estimation (S105, S106) of the battery SOH based on SOH estimation request.

The evaluation method of above-mentioned battery SOH and device thereof by measuring the internal resistance of battery, and directly by the OCV of internal resistance and battery relation so that estimate the SOH of the battery this moment.Simply, eliminate the process of the relation table of various factors and the battery SOH setting up battery, the test duration is short and cost is lower for the evaluation method of battery SOH of the present invention and device thereof.

In addition, those skilled in the art also can do other change in spirit of the present invention, and certainly, these changes done according to the present invention's spirit, all should be included in the present invention's scope required for protection.

Claims

1. an evaluation method for cell health state, the method comprises:

Measure the internal resistance R of battery;

According to the internal resistance R of battery and the relational expression of pressure drop Δ V: Δ V=R × I, obtain the voltage drop value Δ V of battery, now I is the lower bound current value I preset in use capacity;

The OCV value of electric capacity lower limit is this moment calculated by pressure drop Δ V value;

Relation table according to OCV and the SOC of battery obtains SOC lower limit SOC this moment _-1; And

According to the charged state SOC lower limit SOC this moment of SOH and battery _-the relational expression of 1: SOH=100%-SOC _-1, obtain SOH value.

2. the evaluation method of cell health state as claimed in claim 1, is characterized in that: described internal resistance of cell value is calculated by the magnitude of voltage and current value measuring battery.

3. the evaluation method of cell health state as claimed in claim 1, is characterized in that: the described lower limit of electric capacity this moment OCV value to be added with the lower voltage limit V of this battery by this pressure drop Δ V and to draw.

4. the evaluation method of cell health state as claimed in claim 1, is characterized in that: the relation table of described OCV and SOC is as follows:

5. an estimating device for cell health state, comprising:

Storer, it stores the relation table of OCV and SOC;

Voltage acquisition unit and current acquisition unit, it measures the voltage and current of battery;

Controller, when proposing the request of estimating state of health of battery, this controller by voltage acquisition unit and current acquisition unit the voltage and current to this moment battery measure, and send the voltage and current value of the battery of above-mentioned measurement to processor; Meanwhile, controller by the information transmission of the storage of storer to processor;

Processor, by the voltage and current data analysis of battery collected, calculates the internal resistance of battery; The pressure drop Δ V that internal resistance causes is calculated according to the internal resistance of the battery determined; Pressure drop Δ V according to the battery determined calculates lower limit OCV value; From described storer, read the corresponding relation of OCV and SOC, and calculate SOC lower limit SOC this moment according to lower limit OCV value _-1; According to SOC _-1 calculates SOH value.

6. the estimating device of cell health state as claimed in claim 5, is characterized in that: the relation table of OCV and the SOC stored in described storer is as follows:

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