CN107748329A - Charge states of lithium ion battery monitoring method, monitoring device and monitoring modular - Google Patents

Abstract

The invention provides a method for monitoring the state of charge of a lithium-ion battery, comprising the following steps: providing a volume limiting device, a pressure sensor, and a battery pressure-SOC characteristic curve; performing a charge-discharge cycle on the lithium-ion battery to be tested, while passing the volume limit The device limits the volume of the lithium-ion battery to be tested to a fixed value; the pressure sensor obtains the volume between the volume limiting device and the lithium-ion battery to be tested at the time point to be measured during the charging and discharging cycle. a first pressure; and substituting the first pressure into the battery pressure-SOC characteristic curve to obtain the SOC value of the lithium-ion battery to be tested at the time point to be tested. The invention also provides a lithium-ion battery charge state monitoring device and a monitoring module.

Description

Lithium-ion battery state of charge monitoring method, monitoring device and monitoring module

technical field

The invention relates to the field of lithium ion battery management, in particular to a method, device and module for monitoring the state of charge of a lithium ion battery.

Background technique

The remaining capacity of the lithium-ion battery, also known as the State of Charge (SOC) of the lithium-ion battery, is one of the important parameters of the state of the lithium-ion battery, which can provide a basis for the control and management of electric vehicles. Ensure that the SOC is maintained within a reasonable range, prevent overcharge or overdischarge from damage to the lithium-ion battery, make the use of the lithium-ion battery more reasonable, improve the service life of the lithium-ion battery, give full play to the power performance of the lithium-ion battery system, and reduce the The cost of maintaining Li-ion battery systems.

At present, the SOC estimation methods of lithium-ion batteries mainly include: discharge experiment method, open circuit voltage method, ampere-hour measurement method, fuzzy neural network method and Kalman filter method. These methods all need to measure the voltage of the lithium-ion battery, and estimate the remaining capacity of the lithium-ion battery through the voltage. Among them, the discharge experiment method and the open circuit voltage method cannot carry out online monitoring of the SOC of the lithium-ion battery in operation, and the SOC estimation results of the ampere-hour calculation method are usually not accurate enough, and the fuzzy neural network method and the Kalman filter method need to analyze the lithium-ion battery data. With modeling, the method is more complicated. The higher the estimation accuracy required by these methods, the more difficult it is to realize, the more complex the calculations required, and the higher the requirements for the lithium-ion battery management system.

Contents of the invention

Based on this, it is necessary to provide a simple and accurate lithium-ion battery state-of-charge monitoring method, monitoring device and monitoring module that can be used online.

A method for monitoring the state of charge of a lithium-ion battery, comprising the following steps:

Provide volume limiting device and pressure sensor, as well as battery pressure-SOC characteristic curve;

performing a charge-discharge cycle on the lithium-ion battery to be tested, while limiting the volume of the lithium-ion battery to be tested to a fixed value by the volume limiting device;

Obtaining a first pressure between the volume limiting device and the lithium-ion battery to be tested at a time point to be measured during the charge-discharge cycle through the pressure sensor; and

Substituting the first pressure into the battery pressure-SOC characteristic curve to obtain the SOC value of the lithium-ion battery to be tested at the time point to be tested.

In one of the embodiments, the volume limiting device limits the size of the lithium-ion battery along the stacking direction of the electrode sheets.

In one of the embodiments, the volume limiting device includes at least one pressure plate, which is used to set the size of the lithium-ion battery along the stacking direction of the electrode sheet to a fixed value during the charging and discharging cycle, and the pressure sensor It is arranged between the lithium ion battery and the pressure plate.

In one of the embodiments, the electrode sheets of the lithium-ion battery are stacked in the same direction, the pressing plate is flat, and the electrode sheets of the lithium-ion battery are arranged in parallel with the pressing plate; or The electrode sheet of the lithium-ion battery is arranged in a winding manner to form a cylindrical lithium-ion battery, and the pressing plate is cylindrical and coaxially arranged on the periphery of the lithium-ion battery.

In one of the embodiments, the volume limiting device makes the lithium-ion battery subject to an initial pressure before the charge-discharge cycle.

In one of the embodiments, the battery pressure-SOC characteristic curve is obtained through the following steps:

Carrying out a charge-discharge cycle to the standard lithium-ion battery, while limiting the volume of the standard lithium-ion battery to a fixed value through the volume limiting device;

Obtaining the second pressure between the volume limiting device and the standard lithium-ion battery at multiple time points during the charge-discharge cycle and the SOC value of the standard lithium-ion battery through the pressure sensor; and

Fitting the obtained second pressure and the SOC value of the standard lithium-ion battery to obtain the battery pressure-SOC characteristic curve.

In one of the embodiments, the standard lithium-ion battery is the lithium-ion battery to be tested itself, or has the same specifications and parameters as the lithium-ion battery to be tested.

A lithium-ion battery state of charge monitoring device, comprising a volume limiting device and a pressure sensor, the volume limiting device is used to limit the volume of the lithium-ion battery, and the pressure sensor is used to measure the volume of the volume limiting device and the lithium ion pressure between cells.

In one of the embodiments, the volume limiting device limits the size of the lithium-ion battery along the stacking direction of the electrode sheets.

In one of the embodiments, it also includes a monitoring module and an output module;

The monitoring module includes a pressure acquisition module, an SOC calculation module and a storage module;

The pressure acquisition module is used to obtain the pressure data between the volume limiting device and the lithium-ion battery, and transmit it to the SOC calculation module;

The storage module is used to store the battery pressure-SOC characteristic curve;

The SOC calculation module is used to read the battery pressure-SOC characteristic curve from the storage module, and calculate the corresponding lithium-ion battery SOC value according to the pressure data and the battery pressure-SOC characteristic curve;

The output module is used to output the SOC value of the lithium-ion battery obtained by the calculation module in real time.

A lithium-ion battery state of charge monitoring module, including a monitoring module and an output module;

The monitoring module includes a pressure acquisition module, an SOC calculation module and a storage module;

The pressure acquisition module is used to obtain the pressure data obtained by the pressure sensor and transmit it to the SOC calculation module;

The storage module is used to store the battery pressure-SOC characteristic curve;

The SOC calculation module is used to read the battery pressure-SOC characteristic curve from the storage module, and calculate the corresponding lithium-ion battery SOC value according to the pressure data and the battery pressure-SOC characteristic curve;

The output module is used to output the SOC value of the lithium-ion battery obtained by the calculation module in real time.

A method for monitoring the state of charge of a lithium-ion battery, comprising the following steps:

Provide displacement sensor and battery displacement-SOC characteristic curve;

Perform charge and discharge cycles on the lithium-ion battery to be tested;

Obtaining the first displacement of the surface of the lithium-ion battery to be tested due to volume change at the time point to be measured during the charge-discharge cycle through the displacement sensor; and

Substituting the first displacement into the battery displacement-SOC characteristic curve to obtain the SOC value of the lithium-ion battery to be tested at the time point to be tested.

In one of the embodiments, the displacement sensor measures the dimensional change of the lithium-ion battery along the stacking direction of the electrode sheets.

In one of the embodiments, the battery displacement-SOC characteristic curve is obtained through the following steps:

Charge and discharge a standard lithium-ion battery;

Obtaining the second displacement of the surface of the standard lithium-ion battery due to volume change and the SOC value of the standard lithium-ion battery at multiple time points during the charge-discharge cycle through a displacement sensor; and

Fitting the obtained second displacement and the SOC value of the standard lithium-ion battery to obtain the battery displacement-SOC characteristic curve.

A lithium-ion battery state of charge monitoring module, including a monitoring module and an output module;

The monitoring module includes a displacement acquisition module, an SOC calculation module and a storage module;

The displacement acquisition module is used to obtain the displacement data of the surface of the lithium-ion battery due to the volume change, and transmit it to the SOC calculation module;

The storage module is used to store the battery displacement-SOC characteristic curve;

The SOC calculation module is used to read the battery displacement-SOC characteristic curve from the storage module, and calculate the corresponding lithium-ion battery SOC value according to the displacement data and the battery displacement-SOC characteristic curve;

The output module is used to output the SOC value of the lithium-ion battery obtained by the calculation module in real time.

A method for monitoring the state of charge of a lithium-ion battery, comprising the following steps:

Provide volume sensor and battery volume-SOC characteristic curve;

Perform charge and discharge cycles on the lithium-ion battery to be tested;

Obtaining the first volume of the lithium-ion battery to be tested at the time point to be measured during the charging and discharging cycle by the volume sensor; and

Substituting the first volume into the battery volume-SOC characteristic curve to obtain the SOC value of the lithium-ion battery to be tested at the time point to be tested.

In one of the embodiments, the battery volume-SOC characteristic curve is obtained through the following steps:

Charge and discharge a standard lithium-ion battery;

Obtaining the second volume of the standard lithium-ion battery and the SOC value of the standard lithium-ion battery at multiple time points during the charge-discharge cycle through a volume sensor; and

Fitting the obtained second volume and the SOC value of the standard lithium-ion battery to obtain the battery volume-SOC characteristic curve.

A lithium-ion battery state of charge monitoring module, including a monitoring module and an output module;

The monitoring module includes a bit volume acquisition module, an SOC calculation module and a storage module;

The volume acquisition module is used to obtain the volume data of the lithium-ion battery and transmit it to the SOC calculation module;

The storage module is used to store the battery volume-SOC characteristic curve;

The SOC calculation module is used to read the battery volume-SOC characteristic curve from the storage module, and calculate the corresponding lithium-ion battery SOC value according to the volume data and the battery volume-SOC characteristic curve;

The output module is used to output the SOC value of the lithium-ion battery obtained by the calculation module in real time.

In the present invention, the volume change of the lithium-ion battery or parameters capable of reflecting the volume change of the lithium-ion battery, such as pressure change or displacement change, are used as the basis for SOC estimation. The characteristic curve is established in advance by comparing the volume change, pressure change or displacement change of the lithium-ion battery with the SOC value of the lithium-ion battery. In the actual use of lithium-ion batteries, there is no need to measure the voltage of lithium-ion batteries. Real-time SOC monitoring can be realized by monitoring volume changes, pressure changes or displacement changes. It has the characteristics of simple and direct, and can monitor the SOC value of lithium-ion batteries in real time and accurately. , which greatly simplifies the complexity of the battery management system.

Description of drawings

1 is a flowchart of a method for monitoring the state of charge of a lithium-ion battery according to a first embodiment of the present invention;

2 is a schematic structural view of a lithium-ion battery state-of-charge monitoring device according to a first embodiment of the present invention;

3 is a schematic structural view of a lithium-ion battery charge state monitoring device according to another embodiment of the present invention;

4 is a block diagram of a lithium-ion battery state-of-charge monitoring module according to the first embodiment of the present invention;

5 is a test curve of the voltage and the second pressure of the lithium-ion battery in the charging and discharging process according to the first embodiment of the present invention;

FIG. 6 is a battery pressure-SOC characteristic curve obtained by fitting the voltage and the second pressure according to FIG. 5;

7 is a flowchart of a method for monitoring the state of charge of a lithium-ion battery according to the second embodiment of the present invention;

8 is a schematic structural diagram of a lithium-ion battery state-of-charge monitoring device according to a second embodiment of the present invention;

FIG. 9 is a block diagram of a lithium-ion battery charge state monitoring module according to a second embodiment of the present invention;

10 is a flowchart of a method for monitoring the state of charge of a lithium-ion battery according to the third embodiment of the present invention;

FIG. 11 is a block diagram of a lithium-ion battery state-of-charge monitoring module according to a third embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The "state of charge" (SOC) mentioned in the description of the present invention represents the ratio of the electric quantity that the lithium-ion battery has when it has been used for a period of time to the electric quantity that the lithium-ion battery has when it is fully charged, and the value range is 0 to 1. , when SOC=0, it means that the lithium-ion battery is fully discharged, and when SOC=1, it means that the lithium-ion battery is fully charged.

Please refer to FIG. 1 and FIG. 2, the first embodiment of the present invention provides a method for monitoring the state of charge of a lithium-ion battery, including:

S11, providing the volume limiting device 10, the pressure sensor 20, and the battery pressure-SOC characteristic curve;

S12, performing a charge-discharge cycle on the lithium-ion battery 30 to be tested, while limiting the volume of the lithium-ion battery 30 to be tested to a fixed value through the volume limiting device 10;

S13, using the pressure sensor 20 to obtain the first pressure between the volume limiting device 20 and the lithium-ion battery 30 to be tested at the time point to be measured during the charge-discharge cycle; and

S14. Substitute the first pressure into the battery pressure-SOC characteristic curve to obtain the SOC value of the lithium-ion battery 30 to be tested at the time point to be tested.

The first embodiment of the present invention also provides a lithium-ion battery charge state monitoring device, including a volume limiting device 10 and a pressure sensor 20, the volume limiting device 10 is used to limit the volume of the lithium-ion battery, and the pressure sensor 20 is used to measure the volume limit The pressure between the device 10 and the lithium-ion battery, the lithium-ion battery 30 can be a lithium-ion battery 30 to be tested or a standard lithium-ion battery 30 used to establish a battery pressure-SOC characteristic curve.

In one embodiment, the volume limiting device 10 includes at least one pressing plate 12 for setting the size of the lithium-ion battery 30 in at least one direction to a fixed value during charge and discharge cycles. The pressure sensor 20 is provided between the lithium ion battery 30 and the pressure plate 12 . Preferably, the volume limiting device 10 includes two spaced pressure plates 12, and the distance between the two pressure plates 12 is a fixed value during the charge-discharge cycle, so that the lithium-ion battery 30 is perpendicular to the The dimension in the direction of the platen 12 is a fixed value. The volume limiting device 10 may further include a side plate 14 disposed between the two pressure plates 12 and together with the pressure plates 12 to form a cavity, in which the lithium-ion battery 30 is disposed. The distance between the two pressing plates 12 can be adjusted by bolts to suit lithium-ion batteries 30 of different sizes, but the distance is fixed during the charging and discharging cycles. The volume limiting device 10 may further include a uniform plate 16 disposed between the lithium-ion battery 30 and the pressure sensor 20 , and one surface of the uniform plate 16 is bonded to the surface of the lithium-ion battery 30 for uniform pressure distribution.

Preferably, the volume limiting device 10 limits the size of the lithium ion battery 30 along the stacking direction of the electrode sheets 32 . For example, in the embodiment of FIG. 2 , the electrode sheets 32 of the lithium-ion battery 30 are stacked in the same direction, and the pressing plate 12 is flat, so the electrode sheets 32 of the lithium-ion battery 30 can be arranged substantially parallel to the pressing plate 12 .

Please refer to Fig. 3, in another embodiment, the electrode piece 32 of lithium-ion battery 30 is coiled arrangement, forms cylindrical lithium-ion battery 30, and the pressure plate 30 of volume limiting device 10 can be cylindrical, coaxial arrangement on the periphery of the lithium-ion battery 30 .

Preferably, the volume limiting device 10 makes the lithium-ion battery 30 subject to an initial pressure before the charge-discharge cycle, and the pressure sensor 20 can detect the initial pressure value. During the charge-discharge cycle, the pressure varies with the volume of the lithium-ion battery 30 And change. The same initial pressure is preferably applied to the standard lithium-ion battery 30 and the lithium-ion battery 30 to be tested.

The first embodiment of the present invention also provides a lithium-ion battery charge state monitoring module, including a monitoring module 40 and an output module 50 . Please refer to FIG. 4 , in one embodiment, the monitoring module 40 includes a pressure acquisition module 412 , an SOC calculation module 414 and a storage module 416 . The pressure obtaining module 412 is used to obtain the pressure data between the volume limiting device 10 and the lithium-ion battery 30 , such as the pressure data of the first pressure, and transmit it to the SOC calculation module 414 . The storage module 416 is used for storing the battery pressure-SOC characteristic curve. The SOC calculation module 414 is used to read the battery pressure-SOC characteristic curve from the storage module 416, and calculate the corresponding lithium-ion battery SOC value according to the pressure data and the battery pressure-SOC characteristic curve. The output module 50 is used to output the SOC value of the lithium-ion battery obtained by the calculation module 414 in real time.

The device for monitoring the state of charge of the lithium-ion battery according to the first embodiment of the present invention may further include the state-of-charge monitoring module for the lithium-ion battery.

The first embodiment of the present invention also provides a method for establishing a battery pressure-SOC characteristic curve, including:

S111, performing a charge-discharge cycle on the standard lithium-ion battery 30, while limiting the volume of the standard lithium-ion battery 30 to a fixed value through the volume limiting device 10;

S112, obtain the second pressure between the volume limiting device 10 and the standard lithium-ion battery 30 and the SOC of the standard lithium-ion battery 30 at multiple time points during the charge-discharge cycle through the pressure sensor 20; and

S113, using the obtained second pressure and SOC to fit and obtain a battery pressure-SOC characteristic curve.

The standard lithium-ion battery 30 may be the lithium-ion battery 30 to be tested itself, or have the same characteristics as the lithium-ion battery 30 to be tested in terms of the variation of SOC with the volume of the lithium-ion battery during charging and discharging. For example, the standard lithium-ion battery 30 and the lithium-ion battery 30 to be tested can be lithium-ion batteries 30 with the same specifications and parameters, for example, at least one or all of the lithium-ion battery material, structure, capacity and size are the same. In a preferred embodiment, the standard lithium-ion battery 30 is the lithium-ion battery 30 to be tested itself or the lithium-ion battery 30 of the same batch and the same specifications as the lithium-ion battery 30 to be tested. After the lithium-ion battery 30 to be tested is assembled and leaves the factory, The battery pressure-SOC characteristic curve can be established as a standard lithium-ion battery 30 during one charge-discharge cycle, and the battery pressure-SOC characteristic curve established for the lithium-ion battery 30 can be used in subsequent use.

Preferably, the standard lithium-ion battery 30 and the lithium-ion battery 30 to be tested use the same volume limiting device 10 , and the limited volumes of the standard lithium-ion battery 30 and the lithium-ion battery 30 to be tested are the same fixed value.

The charging and discharging cycle in the process of establishing the battery pressure-SOC characteristic curve and the charging and discharging cycle of the lithium-ion battery 30 to be tested during actual use may be the same or different, preferably the charging and discharging conditions are the same. In a preferred embodiment, both the standard lithium ion battery 30 and the lithium ion battery 30 to be tested are charged and discharged by a constant current method, and the charging current and the discharging current are respectively the same.

In step S112, the SOC values of the standard lithium-ion battery 30 at multiple time points can be obtained by existing methods, for example, the voltage and/or current of the standard lithium-ion battery 30 can be monitored during the charging and discharging process to obtain multiple The voltage and/or current at the time point is estimated by the discharge test method, open circuit voltage method, ampere-hour measurement method, fuzzy neural network method or Kalman filter method to estimate the SOC value of the lithium-ion battery 30 . Since the establishment of the battery pressure-SOC characteristic curve is carried out before the actual use of the lithium-ion battery 30, and only needs to be performed once, the SOC value of the lithium-ion battery 30 can be estimated by an estimation method as accurate as possible, so that the battery pressure-SOC characteristic curve Curves are as accurate as possible.

The battery pressure-SOC characteristic curve is the curve obtained by the pressure sensor 20 as the pressure changes with the SOC value. The pressure and the SOC value have a one-to-one correspondence relationship in time. Then it is the SOC of the standard lithium-ion battery 30 at the corresponding time point. In step S113, the battery pressure-SOC characteristic curve can be obtained by an existing curve fitting method, such as least square method or interpolation method. The number of multiple time points depends on the required accuracy of the curve fitting, and the more the computing resources allow, the better.

During the charge and discharge process of the lithium ion battery, lithium ions are inserted into or extracted from the electrode active material, causing a reversible volume change of the electrode sheet 32. Through research, it has been found that the volume change has a corresponding relationship with the SOC value of the lithium ion battery. When the lithium ion battery is charged The volume increases, and the volume decreases when discharged. In the first embodiment of the present invention, the external pressure of the lithium-ion battery is caused by limiting the volume of the lithium-ion battery. The pressure change can be directly monitored by the pressure sensor 20, and the corresponding lithium-ion battery can be obtained through the battery pressure-SOC characteristic curve. SOC value, that is, during the charging and discharging process of the lithium-ion battery 30 to be tested, there is no need to perform the SOC value estimation step, and simple, effective and accurate online monitoring of the SOC value can be realized, which greatly simplifies the complexity of the lithium-ion battery management module. degree and computation.

Please refer to Fig. 5, in one embodiment, the initial pressure applied to the lithium-ion battery 30 by the volume limiting device 10 is 1kgf/cm ² , the lithium-ion battery is charged and discharged at a constant current, and the voltage of the lithium-ion battery is measured at the same time, which can It can be seen that the voltage of the lithium-ion battery has a time-corresponding relationship with the pressure measured by the pressure sensor 20, the pressure increases during charging, and the pressure decreases during discharging, and the reversible changes in the process of multiple charge-discharge cycles prove that the use of lithium-ion batteries The volume change of the battery 30 during charging and discharging can reflect the SOC value of the lithium-ion battery at that time. Please refer to Figure 6, the measured lithium-ion battery voltage is used to estimate the lithium-ion battery SOC value, and the battery pressure-SOC characteristic curve can be obtained by fitting. Using the battery pressure-SOC characteristic curve, the SOC value of the lithium-ion battery at the time point to be measured can be obtained through the first pressure.

Please refer to FIG. 7 and FIG. 8, the second embodiment of the present invention provides a method for monitoring the state of charge of a lithium-ion battery, including:

S21, providing the displacement sensor 60 and the battery displacement-SOC characteristic curve;

S22, performing a charge-discharge cycle on the lithium-ion battery 30 to be tested;

S22, using the displacement sensor 60 to obtain the first displacement of the surface of the lithium-ion battery 30 to be tested at the time point to be measured during the charging and discharging cycle due to the volume change; and

S24. Substitute the first displacement into the battery displacement-SOC characteristic curve to obtain the SOC value of the lithium-ion battery 30 to be tested at the time point to be tested.

The displacement sensor 60 is used to measure the displacement of the surface of the lithium-ion battery 30 due to the volume change. The lithium-ion battery 30 can be a lithium-ion battery 30 to be tested or a standard lithium-ion battery 30 used to establish a battery displacement-SOC characteristic curve. Preferably, the displacement sensor 60 measures the dimensional change of the lithium-ion battery 30 along the stacking direction of the electrode sheets 32 . In one embodiment, the electrode sheets 32 of the lithium-ion battery 30 are stacked in the same direction, and the lithium-ion battery 30 has opposite first and second surfaces in the stacking direction of the electrode sheets 30, and the position of the first surface is fixed, for example It can be arranged on the base 62 , the second surface can move freely during charging and discharging, and the displacement sensor 60 is arranged on the second surface for sensing the moving distance of the second surface in the stacking direction of the electrode sheets 30 .

The second embodiment of the present invention also provides a lithium-ion battery charge state monitoring module, including a monitoring module 40 and an output module 50 . Please refer to FIG. 9 , in one embodiment, the monitoring module 40 includes a displacement acquisition module 422 , an SOC calculation module 424 and a storage module 426 . The displacement acquisition module 422 is used to obtain the displacement data of the surface of the lithium-ion battery 30 due to the volume change, preferably obtain the dimensional change of the lithium-ion battery 30 along the stacking direction of the electrode sheet 32 , and send it to the SOC calculation module 424 . The storage module 426 is used for storing the battery displacement-SOC characteristic curve. The SOC calculation module 424 is used to read the battery displacement-SOC characteristic curve from the storage module 426, and calculate the corresponding lithium-ion battery SOC value according to the displacement data, such as the displacement data of the first displacement, and the battery displacement-SOC characteristic curve . The output module 50 is used to output the SOC value of the lithium-ion battery obtained by the calculation module 424 in real time.

The device for monitoring the state of charge of a lithium-ion battery according to the second embodiment of the present invention may further include the state-of-charge monitoring module for a lithium-ion battery.

The second embodiment of the present invention also provides a method for establishing a battery displacement-SOC characteristic curve, including:

S121, performing a charge-discharge cycle on the standard lithium-ion battery 30;

S122, using the displacement sensor 60 to obtain the second displacement of the surface of the standard lithium ion battery 30 due to the volume change and the SOC value of the standard lithium ion battery 30 at multiple time points during the charging and discharging cycle; and

S123, using the obtained second displacement and SOC value to fit and obtain a battery displacement-SOC characteristic curve.

The second embodiment is basically the same as the first embodiment, except that the displacement generated on the surface of the lithium-ion battery 30 during the charging and discharging process is used to reflect the volume change of the lithium-ion battery 30 .

Please refer to FIG. 10 , the third embodiment of the present invention provides a method for monitoring the state of charge of a lithium-ion battery, including:

S31, providing the volume sensor 70 and the battery volume-SOC characteristic curve;

S32, performing a charge-discharge cycle on the lithium-ion battery 30 to be tested;

S33, using the volume sensor 70 to obtain the first volume of the lithium-ion battery 30 to be measured at the time point to be measured during the charging and discharging cycle; and

S34. Substitute the first volume into the battery volume-SOC characteristic curve to obtain the SOC value of the lithium-ion battery 30 to be tested at the time point to be tested.

The third embodiment of the present invention also provides a lithium-ion battery charge state monitoring module, including a monitoring module 40 and an output module 50 . Please refer to FIG. 11 , in one embodiment, the monitoring module 40 includes a volume acquisition module 432 , an SOC calculation module 434 and a storage module 436 . The volume acquisition module 432 is used to acquire the volume data of the lithium-ion battery 30 and send it to the SOC calculation module 424 . The storage module 426 is used for storing the battery volume-SOC characteristic curve. The SOC calculation module 424 is used to read the battery volume-SOC characteristic curve from the storage module 426, and calculate the corresponding lithium-ion battery SOC value according to the lithium-ion battery volume and the battery volume-SOC characteristic curve. The output module 50 is used to output the SOC value of the lithium-ion battery obtained by the calculation module 424 in real time.

The device for monitoring the state of charge of a lithium-ion battery according to the third embodiment of the present invention may further include the state-of-charge monitoring module for a lithium-ion battery.

The third embodiment of the present invention also provides a method for establishing a battery volume-SOC characteristic curve, including:

S121, performing a charge-discharge cycle on the standard lithium-ion battery 30;

S122, obtain the second volume of the standard lithium-ion battery 30 and the SOC value of the standard lithium-ion battery 30 at multiple time points during the charging and discharging cycle through the volume sensor 70; and

S123, using the obtained second volume and the SOC value to fit and obtain a battery volume-SOC characteristic curve.

The third embodiment is basically the same as the first embodiment, except that the volume change of the lithium-ion battery 30 during charging and discharging is directly measured.

The pressure sensor 20 , the displacement sensor 60 and the volume sensor 70 in the above embodiments may be existing sensors as long as they can measure pressure, displacement and volume.

In the embodiments of the present invention, the volume change of the lithium-ion battery or parameters capable of reflecting the volume change of the lithium-ion battery, such as pressure change or displacement change, are used as the basis for SOC estimation. The characteristic curve is established in advance by comparing the volume change, pressure change or displacement change of the lithium-ion battery with the SOC value of the lithium-ion battery. In the actual use of lithium-ion batteries, there is no need to measure the voltage of lithium-ion batteries. Real-time SOC monitoring can be realized by monitoring volume changes, pressure changes or displacement changes. It has the characteristics of simple and direct, and can monitor the SOC value of lithium-ion batteries in real time and accurately. , which greatly simplifies the complexity of the battery management system.

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (18)

1. A method for monitoring the state of charge of a lithium-ion battery, comprising the following steps: Provide volume limiting device and pressure sensor, as well as battery pressure-SOC characteristic curve; performing a charge-discharge cycle on the lithium-ion battery to be tested, while limiting the volume of the lithium-ion battery to be tested to a fixed value by the volume limiting device; Obtaining a first pressure between the volume limiting device and the lithium-ion battery to be tested at a time point to be measured during the charge-discharge cycle through the pressure sensor; and Substituting the first pressure into the battery pressure-SOC characteristic curve to obtain the SOC value of the lithium-ion battery to be tested at the time point to be tested. 2 . The method for monitoring the state of charge of a lithium-ion battery according to claim 1 , wherein the volume limiting device limits the size of the lithium-ion battery along the stacking direction of the electrode sheets. 3 . 3. The method for monitoring the state of charge of a lithium-ion battery according to claim 2, wherein the volume limiting device includes at least one pressing plate for placing the lithium-ion battery along the electrodes during the charge-discharge cycle. The dimension in the stacking direction of the sheets is a fixed value, and the pressure sensor is provided between the lithium ion battery and the pressure plate. 4. The method for monitoring the state of charge of a lithium-ion battery according to claim 3, wherein the electrode sheets of the lithium-ion battery are stacked in the same direction, the pressing plate is flat, and the lithium-ion battery The electrode sheet is arranged in parallel with the pressing plate; or the electrode sheet of the lithium ion battery is wound and arranged to form a cylindrical lithium ion battery, and the pressing plate is cylindrical and coaxially arranged on the The periphery of the Li-ion battery. 5. The method for monitoring the state of charge of a lithium-ion battery according to claim 1, wherein the volume limiting device makes the lithium-ion battery subject to an initial pressure before the charge-discharge cycle. 6. The lithium-ion battery state of charge monitoring method according to claim 1, wherein the battery pressure-SOC characteristic curve is obtained by the following steps: Carrying out a charge-discharge cycle to the standard lithium-ion battery, while limiting the volume of the standard lithium-ion battery to a fixed value through the volume limiting device; Obtaining the second pressure between the volume limiting device and the standard lithium-ion battery at multiple time points during the charge-discharge cycle and the SOC value of the standard lithium-ion battery through the pressure sensor; and Fitting the obtained second pressure and the SOC value of the standard lithium-ion battery to obtain the battery pressure-SOC characteristic curve. 7. The lithium-ion battery state of charge monitoring method according to claim 1, wherein the standard lithium-ion battery is the lithium-ion battery to be tested itself, or has the same specifications as the lithium-ion battery to be tested and parameters. 8. A lithium-ion battery state of charge monitoring device, characterized in that it includes a volume limiting device and a pressure sensor, the volume limiting device is used to limit the volume of the lithium-ion battery, and the pressure sensor is used to measure the volume limit pressure between the device and the Li-ion battery. 9 . The device for monitoring the state of charge of a lithium-ion battery according to claim 8 , wherein the volume limiting device limits the size of the lithium-ion battery along the stacking direction of the electrode sheets. 10. The lithium-ion battery state of charge monitoring device according to claim 8, further comprising a monitoring module and an output module; The monitoring module includes a pressure acquisition module, an SOC calculation module and a storage module; The pressure acquisition module is used to obtain the pressure data between the volume limiting device and the lithium-ion battery, and transmit it to the SOC calculation module; The storage module is used to store the battery pressure-SOC characteristic curve; The SOC calculation module is used to read the battery pressure-SOC characteristic curve from the storage module, and calculate the corresponding lithium-ion battery SOC value according to the pressure data and the battery pressure-SOC characteristic curve; The output module is used to output the SOC value of the lithium-ion battery obtained by the calculation module in real time. 11. A lithium-ion battery state of charge monitoring module, characterized in that it includes a monitoring module and an output module; The monitoring module includes a pressure acquisition module, an SOC calculation module and a storage module; The pressure acquisition module is used to obtain the pressure data obtained by the pressure sensor and transmit it to the SOC calculation module; The storage module is used to store the battery pressure-SOC characteristic curve; The SOC calculation module is used to read the battery pressure-SOC characteristic curve from the storage module, and calculate the corresponding lithium-ion battery SOC value according to the pressure data and the battery pressure-SOC characteristic curve; The output module is used to output the SOC value of the lithium-ion battery obtained by the calculation module in real time. 12. A method for monitoring the state of charge of a lithium-ion battery, comprising the following steps: Provide displacement sensor and battery displacement-SOC characteristic curve; Perform charge and discharge cycles on the lithium-ion battery to be tested; Obtaining the first displacement of the surface of the lithium-ion battery to be tested due to volume change at the time point to be measured during the charge-discharge cycle through the displacement sensor; and Substituting the first displacement into the battery displacement-SOC characteristic curve to obtain the SOC value of the lithium-ion battery to be tested at the time point to be tested. 13 . The method for monitoring the state of charge of a lithium-ion battery according to claim 12 , wherein the displacement sensor measures the dimensional change of the lithium-ion battery along the stacking direction of the electrode sheets. 14 . 14. The lithium-ion battery state of charge monitoring method according to claim 12, wherein the battery displacement-SOC characteristic curve is obtained by the following steps: Charge and discharge a standard Li-ion battery; Obtaining the second displacement of the surface of the standard lithium-ion battery due to volume change and the SOC value of the standard lithium-ion battery at multiple time points during the charge-discharge cycle through a displacement sensor; and Fitting the obtained second displacement and the SOC value of the standard lithium-ion battery to obtain the battery displacement-SOC characteristic curve. 15. A lithium-ion battery state of charge monitoring module, characterized in that it includes a monitoring module and an output module; The monitoring module includes a displacement acquisition module, an SOC calculation module and a storage module; The displacement acquisition module is used to obtain the displacement data of the surface of the lithium-ion battery due to the volume change, and transmit it to the SOC calculation module; The storage module is used to store the battery displacement-SOC characteristic curve; The SOC calculation module is used to read the battery displacement-SOC characteristic curve from the storage module, and calculate the corresponding lithium-ion battery SOC value according to the displacement data and the battery displacement-SOC characteristic curve; The output module is used to output the SOC value of the lithium-ion battery obtained by the calculation module in real time. 16. A method for monitoring the state of charge of a lithium-ion battery, comprising the following steps: Provide volume sensor and battery volume-SOC characteristic curve; Perform charge and discharge cycles on the lithium-ion battery to be tested; Obtaining the first volume of the lithium-ion battery to be tested at the time point to be measured during the charging and discharging cycle by the volume sensor; and Substituting the first volume into the battery volume-SOC characteristic curve to obtain the SOC value of the lithium-ion battery to be tested at the time point to be tested. 17. The lithium-ion battery state of charge monitoring method according to claim 16, wherein the battery volume-SOC characteristic curve is obtained by the following steps: Charge and discharge a standard Li-ion battery; Obtaining the second volume of the standard lithium-ion battery and the SOC value of the standard lithium-ion battery at multiple time points during the charge-discharge cycle through a volume sensor; and Fitting the obtained second volume and the SOC value of the standard lithium-ion battery to obtain the battery volume-SOC characteristic curve. 18. A lithium-ion battery state of charge monitoring module, characterized in that it includes a monitoring module and an output module; The monitoring module includes a bit volume acquisition module, an SOC calculation module and a storage module; The volume acquisition module is used to obtain the volume data of the lithium-ion battery and transmit it to the SOC calculation module; The storage module is used to store the battery volume-SOC characteristic curve; The SOC calculation module is used to read the battery volume-SOC characteristic curve from the storage module, and calculate the corresponding lithium-ion battery SOC value according to the volume data and the battery volume-SOC characteristic curve; The output module is used to output the SOC value of the lithium-ion battery obtained by the calculation module in real time.