CN108717167A - Batteries of electric automobile self discharge fault judgment method based on equivalent short-circuit internal resistance model - Google Patents

Abstract

The present invention relates to the batteries of electric automobile self discharge fault judgment methods based on equivalent short-circuit internal resistance model, solve the defect that battery failures Diagnostic Strategy can not find battery exception in time compared with prior art.The present invention includes the following steps：The acquisition of electronic vehicle attitude；The acquisition of static condition open-circuit value；The acquisition of electric vehicle power-up state；The acquisition of power-up state open-circuit value；The judgement of battery failures.The present invention can accurately identify the exception in cell operation, accurately identify the voltage change of battery cell, find cell safety problem in time.

Description

Self-discharge fault judgment method of electric vehicle battery based on equivalent short-circuit internal resistance model

technical field

The invention relates to the technical field of electric vehicle batteries, in particular to a method for judging self-discharge faults of electric vehicle batteries based on an equivalent short-circuit internal resistance model.

Background technique

With the rapid growth of the number of electric vehicles, the safety accidents of electric vehicle batteries have begun to increase, and the frequency of battery failures in electric vehicle fire incidents is on the rise. Safety protection at the vehicle and battery pack levels, as well as background monitoring and diagnosis of battery failures are the key to solving electric vehicle safety issues.

The current safety diagnosis strategies for electric vehicle batteries are all based on differential pressure. When the differential voltage of the battery is abnormal, the battery cell has often experienced a serious internal short circuit, and a serious safety accident may occur in a short period of time. At the same time, the fault threshold of the diagnostic strategy based on differential pressure is usually large, and it is impossible to identify subtle safety hazards inside the battery in advance (a large fault threshold causes the battery to be seriously self-discharged when the vehicle reports a fault, which may easily lead to major safety accidents).

Therefore, how to develop an effective and timely electric vehicle battery self-discharge fault judgment method has become an urgent technical problem to be solved.

Contents of the invention

The purpose of the present invention is to solve the defect that the battery fault diagnosis strategy in the prior art cannot detect battery abnormalities in time, and to provide a self-discharge fault judgment method for electric vehicle batteries based on an equivalent short-circuit internal resistance model to solve the above problems.

In order to achieve the above object, the technical scheme of the present invention is as follows:

A method for judging electric vehicle battery self-discharge faults based on an equivalent short-circuit internal resistance model. The equivalent short-circuit internal resistance model includes an equivalent short-circuit internal resistance circuit, and the equivalent short-circuit internal resistance circuit is connected to the open-circuit voltage.

The electric vehicle battery self-discharge fault judgment method includes the following steps:

Acquisition of the state of the electric vehicle, real-time acquisition of the running state of the electric vehicle, waiting for the electric vehicle to be in a static state, the static state of the electric vehicle is that the electric vehicle is in a stop running state and the stop running time reaches 1 hour;

Obtain the value of the open circuit circuit in the static state, and the equivalent short circuit internal resistance circuit obtains the open circuit voltage value OCV1 of the electric vehicle in the static state;

Acquisition of the power-on status of the electric vehicle, real-time acquisition of the running status of the electric vehicle, waiting for the electric vehicle to be in the power-on state, the power-on state is the first power-on trigger after the electric vehicle is in a static state;

Acquisition of the open circuit value in the power-on state, the equivalent short-circuit internal resistance circuit obtains the open-circuit voltage value OCV2 when the electric vehicle is powered on, and records the open-circuit voltage value OCV2 in the power-on state and the open-circuit voltage value in the static state OCV1 time difference t;

Judgment of battery failure, according to the voltage drop of the battery, it is judged whether there is a self-discharge failure in the battery of the electric vehicle.

The judgment of the battery failure includes the following steps:

Calculate the voltage drop difference ΔOCV between the resting state and the power-on state of the battery, and the calculation formula is as follows:

ΔOCV=OCV1-OCV2,

Among them, OCV1 is the open circuit voltage value in the static state, and OCV2 is the open circuit voltage value in the power-on state;

Query and obtain the state of charge values SOC1 and SOC2 corresponding to OCV1 and OCV2 according to the OCV data table at different temperatures of the battery;

For the judgment of the fault type, the battery fault is judged according to the state of charge values SOC1 and SOC2 combined with the open circuit voltage value OCV1 in the static state.

The judgment of described fault type comprises the following steps:

The calculation formula of the state of charge difference ΔSOC is as follows:

ΔSOC=SOC1-SOC2,

Among them, SOC1 is the state of charge value corresponding to OCV1, and SOC2 is the state of charge value corresponding to OCV2;

The calculation formula of current short-circuit value I is as follows:

I=ΔSOC/t,

Wherein, t is the time difference between the open circuit voltage value OCV2 in the power-on state and the open circuit voltage value OCV1 in the static state;

The calculation formula of resistance short-circuit value R is as follows:

R=OCV1/I;

Determination of the fault type,

If the resistance short-circuit value R is greater than 100 ohms, it means that the battery self-discharge is in the normal range;

If the resistance short-circuit value R is in the range of 50 ohms to 100 ohms, it means that the battery self-discharge is in a slight state;

If the resistance short-circuit value R is less than 50 ohms, it means that the battery self-discharge is in a serious state.

Beneficial effect

Compared with the prior art, the electric vehicle battery self-discharge fault judgment method based on the equivalent short-circuit internal resistance model of the present invention can accurately identify abnormalities in the battery operation process, accurately identify battery cell voltage changes, and timely discover battery safety problems . The invention can detect the slight voltage change of the monomer in advance, notify the owner of the vehicle for maintenance in time, and minimize the hidden danger of major safety failures.

Description of drawings

Fig. 1 is a method sequence diagram of the present invention.

Detailed ways

In order to have a further understanding and understanding of the structural features of the present invention and the achieved effects, the preferred embodiments and accompanying drawings are used for a detailed description, as follows:

A method for judging electric vehicle battery self-discharge faults based on an equivalent short-circuit internal resistance model according to the present invention, wherein the equivalent short-circuit internal resistance model includes an equivalent short-circuit internal resistance circuit. The equivalent short-circuit internal resistance circuit is a traditional circuit structure, which is composed of a voltage source, polarization internal resistance, short-circuit internal resistance and AC resistance in series, and the equivalent short-circuit internal resistance circuit is connected to the open circuit voltage of the electric vehicle battery in the traditional way on the OCV.

As shown in Figure 1, the electric vehicle battery self-discharge fault judgment method includes the following steps:

The first step is to obtain the status of electric vehicles.

Obtain the running status of the electric vehicle in real time, and wait for the electric vehicle to be in a stationary state. The static state of the electric vehicle is that the electric vehicle is in a stopped state and the stoppage time reaches 1 hour. In practical applications, the driving habits of electric vehicles can be obtained through the intelligent control chip, and the driving habits can be used to form the default of the static state.

The second step is to obtain the value of the open circuit circuit in the static state, and the equivalent short circuit internal resistance circuit obtains the open circuit voltage value OCV1 of the electric vehicle in the static state.

The third step is to obtain the power-on state of the electric vehicle. Obtain the running status of the electric vehicle in real time, wait for the electric vehicle to be in the power-on state, and the power-on state is the first power-on trigger after the electric vehicle is in a static state.

The fourth step is to obtain the value of the open circuit circuit in the power-on state.

The equivalent short-circuit internal resistance circuit obtains the open circuit voltage value OCV2 when the electric vehicle is powered on, and records the time difference t between the open circuit voltage value OCV2 when the electric vehicle is powered on and the open circuit voltage value OCV1 when the vehicle is at rest.

The fifth step is to judge the battery failure. According to the voltage drop of the battery, it is judged whether there is a self-discharge failure in the battery of the electric vehicle. Among them, the specific steps for judging the battery failure are as follows:

(1) Calculate the voltage drop difference ΔOCV between the static state and the power-on state of the battery, and the calculation formula is as follows:

ΔOCV=OCV1-OCV2,

Among them, OCV1 is the open circuit voltage value in the static state, and OCV2 is the open circuit voltage value in the power-on state.

(2) Obtain the state of charge values SOC1 and SOC2 corresponding to OCV1 and OCV2 according to the OCV data table at different temperatures of the battery. Here, the OCV data table is a basic data table provided by various battery manufacturers, and is a data table established according to battery characteristics, reflecting the corresponding relationship between OCV and SOC at different temperatures.

(3) Judgment of the type of fault, according to the state of charge values SOC1 and SOC2 combined with the open circuit voltage value OCV1 in the static state to judge the battery fault.

A. Calculation of state of charge difference ΔSOC, the calculation formula is as follows:

ΔSOC=SOC1-SOC2,

Wherein, SOC1 is the state of charge value corresponding to OCV1, and SOC2 is the state of charge value corresponding to OCV2.

B. Calculation of current short-circuit value I, the calculation formula is as follows:

I=ΔSOC/t,

Wherein, t is the time difference between the open circuit voltage value OCV2 in the power-on state and the open circuit voltage value OCV1 in the static state;

C. Calculation of resistance short-circuit value R, the calculation formula is as follows:

R=OCV1/I;

D. Determination of the fault type. Here, the short circuit value of the resistance is calculated by using the ratio of the voltage value to the current value, and the self-discharge situation is judged by the short circuit value of the resistance. A large resistance value indicates that the self-discharge is normal and harmless to the human body; a small resistance value indicates that the self-discharge is abnormal, that is, a large current value indicates that the self-discharge is abnormal and harmful to the human body.

If the resistance short-circuit value R is greater than 100 ohms, it means that the battery self-discharge is in the normal range;

If the resistance short-circuit value R is in the range of 50 ohms to 100 ohms, it means that the battery self-discharge is in a slight state;

If the resistance short-circuit value R is less than 50 ohms, it means that the self-discharge of the battery is in a serious state, and a power-on alarm is performed to notify the driver.

The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments. What are described in the above-mentioned embodiments and the description are only the principles of the present invention. Variations and improvements, which fall within the scope of the claimed invention. The scope of protection required by the present invention is defined by the appended claims and their equivalents.

Claims (3)

1. a kind of batteries of electric automobile self discharge fault judgment method based on equivalent short-circuit internal resistance model, equivalent short circuit internal resistance mould Type include it is equivalent short circuit in resistance circuit, it is equivalent short circuit in resistance circuit be attempted by open-circuit voltage, which is characterized in that

Batteries of electric automobile self discharge fault judgment method includes the following steps：

11) acquisition of electronic vehicle attitude obtains electric vehicle operating status in real time, and electric vehicle is waited for be in static condition, Electric vehicle static condition is that electric vehicle is in run-stopping status and the time out of service reaches 1 hour；

12) acquisition of static condition open-circuit value, it is equivalent short circuit in resistance circuit obtain electric vehicle static condition when open circuit Voltage value OCV1；

13) acquisition of electric vehicle power-up state obtains electric vehicle operating status in real time, waits for electric vehicle to be in and powers on shape State, power-up state are that electric vehicle is in after static condition and powers on triggering for the first time；

14) acquisition of power-up state open-circuit value, it is equivalent short circuit in resistance circuit obtain electric vehicle power-up state when open circuit Voltage value OCV2, and record open-circuit voltage values OCV2 when obtaining power-up state and open-circuit voltage values when acquisition static condition The time difference t of OCV1；

15) judgement of battery failures judges that batteries of electric automobile whether there is self discharge failure according to battery pressure drop situation.

2. the batteries of electric automobile self discharge breakdown judge side according to claim 1 based on equivalent short-circuit internal resistance model Method, which is characterized in that the judgement of the battery failures includes the following steps：

21) the pressure drop difference Δ OCV of battery standing state and power-up state is calculated, calculation formula is as follows：

Δ OCV=OCV1-OCV2,

Wherein, open-circuit voltage values when OCV1 is static condition, open-circuit voltage values when OCV2 is power-up state；

22) the state of charge SOC1 corresponding to OCV1 and OCV2 is obtained according to the OCV tables of data inquiry under battery different temperatures And SOC2；

23) judgement of fault type, open-circuit voltage values OCV1 when according to state of charge SOC1 and SOC2 combination static condition Judge battery failures.

3. the batteries of electric automobile self discharge breakdown judge side according to claim 2 based on equivalent short-circuit internal resistance model Method, which is characterized in that the judgement of the fault type includes the following steps：

31) calculating of state-of-charge difference DELTA SOC, calculation formula are as follows：

Δ SOC=SOC1-SOC2,

Wherein, SOC1 is the state of charge corresponding to OCV1, and SOC2 is the state of charge corresponding to OCV2；

32) calculating of short circuit current value I, calculation formula are as follows：

I=Δ SOC/t,

Wherein, the time of open-circuit voltage values OCV2 and the open-circuit voltage values OCV1 when acquisition static condition when t is power-up state Difference；

33) calculating of resistive short value R, calculation formula are as follows：

R=OCV1/I；

34) determination of fault type,

If resistive short value R is more than 100 ohm, indicate that self-discharge of battery is in normal interval state；

If resistive short value R is located at 50 ohm to 100 ohm sections, indicate that self-discharge of battery is in mild state；

If resistive short value R is less than 50 ohm, indicate that self-discharge of battery is in severe conditions.