CN114167286A - Lithium battery thermal runaway detection method and system based on internal resistance trend difference - Google Patents
Lithium battery thermal runaway detection method and system based on internal resistance trend difference Download PDFInfo
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 37
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 36
- 238000001514 detection method Methods 0.000 title claims abstract description 8
- 238000000034 method Methods 0.000 claims abstract description 36
- 230000008859 change Effects 0.000 abstract description 7
- 230000008569 process Effects 0.000 description 4
- 238000005259 measurement Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229910000733 Li alloy Inorganic materials 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000001989 lithium alloy Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- 239000011255 nonaqueous electrolyte Substances 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
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Abstract
The embodiment of the invention provides a lithium battery thermal runaway detection method and system based on an internal resistance trend difference, and belongs to the technical field of lithium batteries. The method comprises determining a current time; acquiring the voltage and the current of a single battery in the battery pack at the current moment; calculating the internal resistance of the single battery at the current moment according to a formula (1); according to the technical scheme, the voltage and the current of the single battery are obtained, the internal resistance trend difference is obtained according to the voltage and the current of the single battery, the value of the internal resistance trend difference is judged, and when the internal resistance trend value exceeds a controllable range, the single battery is judged to be in a thermal runaway state; the internal resistance trend value can accurately feed back the internal resistance change of the single battery, and the state of the single battery can be accurately judged according to the internal resistance change, so that the accurate identification capability of the lithium battery in the thermal runaway state is improved.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a lithium battery thermal runaway detection method and system based on an internal resistance trend difference.
Background
A lithium battery is a type of battery using a nonaqueous electrolyte solution, using lithium metal or a lithium alloy as a positive/negative electrode material. The lithium battery has the advantages of large storage capacity, no memory, more times of charging and discharging, light weight, recoverability, small pollution and the like, so the lithium battery is widely applied to electric automobiles.
However, in the use process of the lithium battery, generally, the judgment is performed by rapidly increasing the temperature, and when thermal runaway occurs, the temperature of the battery slowly increases; if the temperature of the battery rises rapidly, the thermal runaway of the lithium battery is completely caused, irretrievable loss is caused, and even serious consequences are caused.
Disclosure of Invention
The embodiment of the invention aims to provide a lithium battery thermal runaway detection method and system based on an internal resistance trend difference, and the method and system can accurately detect and judge the thermal runaway state of a lithium battery.
In order to achieve the above object, an aspect of the embodiments of the present invention provides a method for detecting thermal runaway of a lithium battery based on an internal resistance trend difference, including:
determining the current moment;
acquiring the voltage and the current of a single battery in the battery pack at the current moment;
calculating the internal resistance of the single battery at the current moment according to the formula (1),
wherein ,
the internal resistance of the single battery at the current moment, t is the current moment, and t-1 is the last time of the current momentTime, n represents the nth cell in the battery pack, Vn(t) is the voltage of the single cell at time t, Vn(t-1) is the voltage of the single cell at t-1, In(t) is the current of the single cell at time t, In(t-1) is the current of the single cell at t-1;
calculating the internal resistance trend difference of the nth battery according to the formula (2),
wherein ,
is the internal resistance trend difference of the nth battery,
the initial internal resistance value of the nth battery;
judging whether the internal resistance trend difference is larger than 0;
under the condition that the internal resistance trend difference is judged to be larger than 0, the thermal runaway of the battery is judged;
and under the condition that the internal resistance trend difference is judged to be less than or equal to 0, judging that the thermal runaway of the battery does not occur.
Optionally, the method further comprises:
calculating the effective value of the internal resistance trend difference according to a formula (3),
wherein ,ΔRthdThe effective value of the internal resistance trend difference is obtained;
calculating the internal resistance trend difference according to the formula (4),
judging whether the internal resistance trend difference is larger than or equal to the effective value;
under the condition that the internal resistance trend difference is judged to be larger than or equal to the effective value, the thermal runaway of the battery is judged;
and under the condition that the internal resistance trend difference is judged to be smaller than the effective value, judging that the thermal runaway of the battery does not occur.
Optionally, the method further comprises:
calculating the total internal resistance trend difference of the battery according to the formula (5),
wherein d (t) is the total tendency difference of the internal resistance of the battery,
the internal resistance trend difference of the kth battery is obtained;
judging whether the total internal resistance trend difference of the battery is larger than or equal to a threshold value alarm value;
under the condition that the total internal resistance trend difference of the battery is judged to be larger than or equal to a threshold value alarm value, judging that the thermal runaway of the battery occurs;
and under the condition that the total internal resistance trend difference of the battery is smaller than the threshold value alarm value, judging that the thermal runaway of the battery does not occur.
Optionally, the threshold alarm value comprises a first threshold alarm value and a second threshold alarm value, and the method further comprises:
judging whether the total internal resistance trend difference of the battery is larger than or equal to the first threshold alarm value;
under the condition that the total internal resistance trend difference of the batteries is judged to be larger than or equal to the first threshold value alarm value, judging whether the total internal resistance trend difference of the batteries is larger than or equal to the second threshold value alarm value;
under the condition that the total internal resistance trend difference of the battery is judged to be larger than or equal to the second threshold value alarm value, judging that the thermal runaway of the battery occurs, and outputting a serious alarm;
under the condition that the trend difference of the total internal resistance of the battery is judged to be smaller than the second threshold value alarm value, judging that the thermal runaway of the battery occurs, and outputting a slight alarm;
and under the condition that the total internal resistance trend difference of the battery is judged to be smaller than the first threshold value alarm value, judging that the thermal runaway of the battery does not occur.
In another aspect, the present invention provides a system for detecting thermal runaway of a lithium battery based on an internal resistance trend difference, where the system includes:
the voltage sensor is arranged on each battery of the battery pack in parallel to acquire the voltage of each battery;
the current sensor is arranged on a loop of the battery pack so as to obtain the current of each battery;
and the controller is connected with the voltage sensor and the current sensor.
Optionally, the controller is to:
determining the current moment;
acquiring the voltage and the current of a single battery in the battery pack at the current moment;
calculating the internal resistance of the single battery at the current moment according to the formula (1),
wherein ,
the internal resistance of the single battery at the current moment, t is the current moment, t-1 is the last moment of the current moment, n represents the nth battery in the battery pack, Vn(t) is the voltage of the single cell at time t, Vn(t-1) is the voltage of the single cell at t-1, In(t) is the current of the single cell at time t, In(t-1) is the current of the single cell at t-1;
calculating the internal resistance trend difference of the nth battery according to the formula (2),
wherein ,
is the internal resistance trend difference of the nth battery,
the initial internal resistance value of the nth battery;
judging whether the internal resistance trend difference is larger than 0;
under the condition that the internal resistance trend difference is judged to be larger than 0, the thermal runaway of the battery is judged;
and under the condition that the internal resistance trend difference is judged to be less than or equal to 0, judging that the thermal runaway of the battery does not occur.
Optionally, the controller is to:
calculating the effective value of the internal resistance trend difference according to a formula (3),
wherein ,ΔRthdThe effective value of the internal resistance trend difference is obtained;
calculating the internal resistance trend difference according to the formula (4),
judging whether the internal resistance trend difference is larger than or equal to the effective value;
under the condition that the internal resistance trend difference is judged to be larger than or equal to the effective value, the thermal runaway of the battery is judged;
and under the condition that the internal resistance trend difference is judged to be smaller than the effective value, judging that the thermal runaway of the battery does not occur.
Optionally, the controller is to:
calculating the total internal resistance trend difference of the battery according to the formula (5),
wherein d (t) is the total tendency difference of the internal resistance of the battery,
the internal resistance trend difference of the kth battery is obtained;
judging whether the total internal resistance trend difference of the battery is larger than or equal to a threshold value alarm value;
under the condition that the total internal resistance trend difference of the battery is judged to be larger than or equal to a threshold value alarm value, judging that the thermal runaway of the battery occurs;
and under the condition that the total internal resistance trend difference of the battery is smaller than the threshold value alarm value, judging that the thermal runaway of the battery does not occur.
Optionally, the threshold alarm values comprise a first threshold alarm value and a second threshold alarm value, and the controller is configured to:
judging whether the total internal resistance trend difference of the battery is larger than or equal to the first threshold alarm value;
under the condition that the total internal resistance trend difference of the batteries is judged to be larger than or equal to the first threshold value alarm value, judging whether the total internal resistance trend difference of the batteries is larger than or equal to the second threshold value alarm value;
under the condition that the total internal resistance trend difference of the battery is judged to be larger than or equal to the second threshold value alarm value, judging that the thermal runaway of the battery occurs, and outputting a serious alarm;
under the condition that the trend difference of the total internal resistance of the battery is judged to be smaller than the second threshold value alarm value, judging that the thermal runaway of the battery occurs, and outputting a slight alarm;
and under the condition that the total internal resistance trend difference of the battery is judged to be smaller than the first threshold value alarm value, judging that the thermal runaway of the battery does not occur.
In yet another aspect, the present invention provides a computer readable storage medium having stored thereon instructions for reading by a machine to cause the machine to perform a method as described in any one of the above.
According to the technical scheme, the method and the system for detecting the thermal runaway of the lithium battery based on the internal resistance trend difference provided by the invention have the advantages that the voltage and the current of a single battery are obtained, the internal resistance trend difference is obtained according to the voltage and the current of the single battery, the value of the internal resistance trend difference is judged, and when the internal resistance trend value exceeds a controllable range, the single battery is judged to be in the thermal runaway state; the internal resistance trend value can accurately feed back the internal resistance change of the single battery, and the state of the single battery can be accurately judged according to the internal resistance change, so that the accurate identification capability of the lithium battery in the thermal runaway state is improved.
Additional features and advantages of embodiments of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the embodiments of the invention without limiting the embodiments of the invention. In the drawings:
FIG. 1 is a flow chart of a method for detecting thermal runaway of a lithium battery based on a trend difference in internal resistance according to one embodiment of the invention;
FIG. 2 is a flow chart of comparing the trend difference of internal resistance with an effective value in a method for detecting thermal runaway of a lithium battery based on the trend difference of internal resistance according to an embodiment of the invention;
fig. 3 is a flowchart of battery pack thermal runaway state determination in a method for lithium battery thermal runaway detection based on internal resistance trend difference according to an embodiment of the invention;
fig. 4 is a flowchart of battery pack thermal runaway level determination in a method for detecting thermal runaway of a lithium battery based on internal resistance trend difference according to an embodiment of the invention.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration and explanation only, not limitation.
Fig. 1 is a flowchart of a method for detecting thermal runaway of a lithium battery based on an internal resistance trend difference according to an embodiment of the present invention. In fig. 1, the method may include:
in step S10, the voltage and current of the single battery in the battery pack at the present time are acquired. Before monitoring the state of the single battery, the current moment needs to be confirmed, and the voltage and the current of the single battery at the current moment are acquired. In this embodiment of the present invention, the voltage and current of a single battery can be acquired in real time using a voltage sensor and a current sensor, respectively.
In step S11, the battery internal resistance of the single battery at the present time is calculated according to the formula (1),
wherein ,
the internal resistance of a single battery at the current moment, t is the current moment, t-1 is the previous moment of the current moment, n represents the nth battery in the battery pack, Vn(t) is the voltage of a single cell at time t, Vn(t-1) is the voltage of a single cell at t-1, In(t) is the current of a single cell at time t, InAnd (t-1) is the current of the single battery under t-1.
In step S12, the internal resistance trend difference of the nth battery is calculated according to the formula (2),
wherein ,
is the internal resistance trend difference of the nth battery,
is the initial internal resistance value of the nth battery.
In step S13, it is determined whether or not the internal resistance trend difference is greater than 0. And if the internal resistance changes, the state of the single battery is unstable.
In step S14, if it is determined that the internal resistance trend difference is greater than 0, it is determined that thermal runaway of the battery has occurred. If the absolute value of the internal resistance trend difference is larger than 0, the internal resistance of the single battery is changed, namely the single battery is in a thermal runaway state.
In step S15, if it is determined that the internal resistance trend difference is equal to or less than 0, it is determined that thermal runaway of the battery has not occurred. If the internal resistance trend difference is 0, the internal resistance of the single battery is not changed, namely the single battery is not in a thermal runaway state.
In steps S10 to S15, the voltage and the current of a single battery in the battery pack at the current time are obtained, the battery internal resistance of the single battery is obtained according to the voltage and the current, the internal resistance trend difference of the single battery is calculated according to the battery internal resistance, the internal resistance trend difference is compared with 0, if the internal resistance trend difference is greater than 0, the single battery is in a thermal runaway state, otherwise, the single battery is not in the thermal runaway state. In actual use of the existing lithium battery, the temperature curve of the lithium battery is measured by a temperature sensor for judgment, and if the temperature curve of the lithium battery suddenly rises, the lithium battery is in a thermal runaway state. However, when the temperature curve of the lithium battery rises rapidly, thermal runaway of the lithium battery occurs completely, irretrievable loss is caused, and even serious consequences are caused. In the embodiment of the invention, the state of the lithium battery in normal operation can be accurately judged by acquiring the current voltage and current of the single battery and calculating the internal resistance trend difference of the single battery. Normally, the internal resistance of the single battery is in a constant state, but if the internal resistance of the single battery changes, the single battery is in an unstable state, and the single battery can be judged to be in a thermal runaway state. The method for judging the state of the single battery through the internal resistance trend difference can improve the accurate recognition capability of the lithium battery in the thermal runaway state.
In this embodiment of the present invention, in order to avoid the thermal runaway early warning error caused by the measurement error, it is necessary to eliminate the influence of the measurement error on the internal resistance trend difference. In particular, the method may comprise the steps as shown in fig. 2. In this fig. 2, the method may further include:
in step S20, an effective value of the internal resistance trend difference is calculated according to the formula (3),
wherein ,ΔRthdThe effective value of the internal resistance trend difference. In this embodiment of the invention, the effective value Δ R is used to avoid failure of thermal runaway prediction for individual cells after the cycle life of the cell has increasedthdIs generally set to the initial internal resistance of a single battery
2 times of the total weight of the powder.
In step S21, it is determined whether or not the internal resistance trend difference is equal to or greater than the effective value. The effective value eliminates the influence of the rise of the cycle life of the battery on the thermal runaway state of the single battery, and the obtained internal resistance trend difference of the single battery is compared with the effective value, so that the thermal runaway state of the single battery can be accurately judged.
In step S22, when it is determined that the internal resistance trend difference is equal to or greater than the effective value, it is determined that thermal runaway of the battery has occurred. The effective value eliminates the influence of the rise of the cycle life of the battery on the thermal runaway state of the single battery, and at the moment, if the internal resistance trend difference is greater than or equal to the effective value, the single battery is in an unstable state, namely the single battery is in the thermal runaway state.
In step S23, if it is determined that the internal resistance trend difference is smaller than the effective value, it is determined that thermal runaway of the battery has not occurred. If the internal resistance trend difference is smaller than the effective value, the internal resistance trend difference is in a controllable range, and the single battery is not out of control, namely the single battery is not in a thermal runaway state.
In steps S20 to S23, in order to avoid a thermal runaway warning error caused by a measurement error, an effective value of the internal resistance trend difference of the single battery cell is set, and the effective value is compared with the internal resistance trend difference. If the internal resistance trend difference is larger than or equal to the effective value, the single battery is in a thermal runaway state, and if the internal resistance trend difference is smaller than the effective value, the single battery is not in the thermal runaway state. The effective value is compared with the internal resistance trend difference, so that the influence of the cycle life rise of the battery on the thermal runaway state of the single battery can be eliminated, and the accuracy of judging the thermal runaway state of the single battery is improved.
In this embodiment of the present invention, in order to monitor the thermal runaway state of the total battery pack, it is necessary to calculate and determine the thermal runaway state of the battery pack. In particular, the method may comprise the steps as shown in fig. 3. In this fig. 3, the method may further include:
in step S30, the total internal resistance tendency difference of the battery is calculated according to the formula (5),
wherein d (t) is the total tendency difference of the internal resistance of the battery,
is the internal resistance trend difference of the kth battery. Summing the internal resistance trend differences of each battery to obtain the total electricityThe tendency of resistance in the pool is poor.
In step S31, it is determined whether the total internal resistance trend difference of the battery is greater than or equal to a threshold alarm value. And setting a threshold alarm value of the total internal resistance trend difference of the battery, wherein the threshold alarm value is used for comparing with the total internal resistance trend difference of the battery to be used as a judgment standard for judging whether the battery is in a thermal runaway state.
In step S32, in the case where it is determined that the total internal resistance trend difference of the battery is greater than or equal to the threshold alarm value, it is determined that thermal runaway of the battery occurs. If the total internal resistance trend difference of the batteries is larger than or equal to the threshold value alarm value, the total internal resistance trend difference of the batteries is over large, namely the internal resistance of the battery pack is changed too much, and the battery pack is in a thermal runaway state.
In step S33, in the case where it is determined that the total internal resistance trend difference of the battery is smaller than the threshold alarm value, it is determined that thermal runaway of the battery does not occur. If the total internal resistance trend difference of the battery is smaller than the threshold value alarm value, the total internal resistance trend difference of the battery is in a controllable range, namely the internal resistance of the battery pack changes in the controllable range, and the battery pack is not in a thermal runaway state.
In steps S30 to S33, a total trend difference of the internal resistance of the battery is calculated, the total trend difference of the internal resistance of the battery is compared with a threshold alarm value, if the total trend difference of the internal resistance of the battery is greater than the threshold alarm value, it is indicated that the total trend difference of the internal resistance of the battery exceeds a controllable state, the internal resistance change of the battery pack exceeds a controllable range, the battery pack is in a thermal runaway state, otherwise, the battery pack is not in the thermal runaway state. By adopting the mode of setting threshold value alarm, the thermal runaway state of the battery pack can be effectively judged.
In this embodiment of the invention, the threshold alarm value may comprise a first threshold alarm value d in order to increase the accuracy of the alarmthd1And a second threshold alarm value dthd2And a second threshold alarm value dthd2Greater than a first threshold alarm value dthd1. In particular, the method may comprise the steps as shown in fig. 4. In this fig. 4, the method may further include:
in step S40, a total battery internal resistance tendency difference is acquired.
In step S41, it is determined whether the total internal resistance trend difference of the battery is greater than or equal to a first threshold alarm value. And comparing the total internal resistance trend difference of the battery with a first threshold alarm value to judge whether the battery pack is in a thermal runaway state.
In step S42, in the case where it is determined that the total internal resistance trend difference of the battery is greater than or equal to the first threshold alarm value, it is determined whether or not the total internal resistance trend difference of the battery is greater than or equal to the second threshold alarm value. When the total internal resistance trend difference of the battery is determined to be greater than or equal to the first threshold value alarm value, the battery pack is in a thermal runaway state, but whether the thermal runaway state of the battery pack is serious or not is determined, the total internal resistance trend difference of the battery is required to be compared with the second threshold value alarm value.
In step S43, if it is determined that the total internal resistance trend difference of the battery is greater than or equal to the second threshold alarm value, it is determined that thermal runaway of the battery occurs, and a serious alarm is output. If the total internal resistance trend difference of the battery is larger than or equal to the second threshold value alarm value, the battery pack is in a serious thermal runaway state, and a serious alarm is output to prompt a worker to take corresponding emergency measures.
In step S44, if it is determined that the total internal resistance trend difference of the battery is smaller than the second threshold alarm value, it is determined that the thermal runaway of the battery occurs, and a light alarm is output. If the total internal resistance trend difference of the battery is smaller than the second threshold value alarm value, the battery pack is in a slight thermal runaway state, and a slight alarm is output to prompt a worker to take corresponding emergency measures.
In step S45, if it is determined that the total internal resistance trend difference of the battery is smaller than the first threshold warning value, it is determined that the thermal runaway of the battery does not occur. If the total internal resistance trend difference of the battery is smaller than the first threshold value alarm value, the battery pack is not in a thermal runaway state.
In steps S40 to S45, the total trend difference of the internal resistance of the battery is compared with a first threshold value, and if the total trend difference of the internal resistance of the battery is smaller than the first threshold value, it indicates that the battery pack is operating normally and the battery pack is not in the thermal runaway state. If the total internal resistance trend difference of the battery is greater than or equal to a first threshold alarm value and less than a second threshold alarm value, the battery pack is in a slight thermal runaway state; and if the total internal resistance trend difference of the batteries is greater than or equal to a second threshold alarm value, indicating that the battery pack is in a serious thermal runaway state. The thermal runaway state of the battery pack can be graded by setting the first threshold alarm value and the second threshold alarm value, so that the working personnel can take corresponding treatment measures according to the grade of the thermal runaway state, and the loss caused by the thermal runaway of the battery pack is reduced.
On the other hand, the invention also provides a system for detecting the thermal runaway of the lithium battery based on the internal resistance trend. In particular, the system may include a voltage sensor, a current sensor, and a controller.
The voltage sensor is arranged on each battery of the battery pack in parallel to acquire the voltage of each battery; the current sensor is arranged on a loop of the battery pack to acquire the current of each battery; the controller is connected with the voltage sensor and the current sensor and is used for executing the method.
In yet another aspect, the invention also provides a computer-readable storage medium that may store instructions for reading by a machine to cause the machine to perform a method as any one of the above.
According to the technical scheme, the method and the system for detecting the thermal runaway of the lithium battery based on the internal resistance trend difference provided by the invention have the advantages that the voltage and the current of a single battery are obtained, the internal resistance trend difference is obtained according to the voltage and the current of the single battery, the value of the internal resistance trend difference is judged, and when the internal resistance trend value exceeds a controllable range, the single battery is judged to be in the thermal runaway state; the internal resistance trend value can accurately feed back the internal resistance change of the single battery, and the state of the single battery can be accurately judged according to the internal resistance change, so that the accurate identification capability of the lithium battery in the thermal runaway state is improved.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in the process, method, article, or apparatus that comprises the element.
The above are merely examples of the present application and are not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (10)
1. A lithium battery thermal runaway detection method based on internal resistance trend difference is characterized by comprising the following steps:
determining the current moment;
acquiring the voltage and the current of a single battery in the battery pack at the current moment;
calculating the internal resistance of the single battery at the current moment according to the formula (1),
wherein ,
the internal resistance of the single battery at the current moment, t is the current moment, t-1 is the last moment of the current moment, n represents the nth battery in the battery pack, Vn(t) is the voltage of the single cell at time t, Vn(t-1) is the voltage of the single cell at t-1, In(t) is the power of the single battery at the time tFlow, In(t-1) is the current of the single cell at t-1;
calculating the internal resistance trend difference of the nth battery according to the formula (2),
wherein ,
is the internal resistance trend difference of the nth battery,
the initial internal resistance value of the nth battery;
judging whether the internal resistance trend difference is larger than 0;
under the condition that the internal resistance trend difference is judged to be larger than 0, the thermal runaway of the battery is judged;
and under the condition that the internal resistance trend difference is judged to be less than or equal to 0, judging that the thermal runaway of the battery does not occur.
2. The method of claim 1, further comprising:
calculating the effective value of the internal resistance trend difference according to a formula (3),
wherein ,ΔRthdThe effective value of the internal resistance trend difference is obtained;
calculating the internal resistance trend difference according to the formula (4),
judging whether the internal resistance trend difference is larger than or equal to the effective value;
under the condition that the internal resistance trend difference is judged to be larger than or equal to the effective value, the thermal runaway of the battery is judged;
and under the condition that the internal resistance trend difference is judged to be smaller than the effective value, judging that the thermal runaway of the battery does not occur.
3. The method of claim 1, further comprising:
calculating the total internal resistance trend difference of the battery according to the formula (5),
wherein d (t) is the total tendency difference of the internal resistance of the battery,
the internal resistance trend difference of the kth battery is obtained;
judging whether the total internal resistance trend difference of the battery is larger than or equal to a threshold value alarm value;
under the condition that the total internal resistance trend difference of the battery is judged to be larger than or equal to a threshold value alarm value, judging that the thermal runaway of the battery occurs;
and under the condition that the total internal resistance trend difference of the battery is smaller than the threshold value alarm value, judging that the thermal runaway of the battery does not occur.
4. The method of claim 3, wherein the threshold alarm value comprises a first threshold alarm value and a second threshold alarm value, the method further comprising:
judging whether the total internal resistance trend difference of the battery is larger than or equal to the first threshold alarm value;
under the condition that the total internal resistance trend difference of the batteries is judged to be larger than or equal to the first threshold value alarm value, judging whether the total internal resistance trend difference of the batteries is larger than or equal to the second threshold value alarm value;
under the condition that the total internal resistance trend difference of the battery is judged to be larger than or equal to the second threshold value alarm value, judging that the thermal runaway of the battery occurs, and outputting a serious alarm;
under the condition that the trend difference of the total internal resistance of the battery is judged to be smaller than the second threshold value alarm value, judging that the thermal runaway of the battery occurs, and outputting a slight alarm;
and under the condition that the total internal resistance trend difference of the battery is judged to be smaller than the first threshold value alarm value, judging that the thermal runaway of the battery does not occur.
5. The utility model provides a lithium cell thermal runaway detection's system based on internal resistance trend difference which characterized in that, the system includes:
the voltage sensor is arranged on each battery of the battery pack in parallel to acquire the voltage of each battery;
the current sensor is arranged on a loop of the battery pack so as to obtain the current of each battery;
and the controller is connected with the voltage sensor and the current sensor.
6. The system of claim 5, wherein the controller is to:
determining the current moment;
acquiring the voltage and the current of a single battery in the battery pack at the current moment;
calculating the internal resistance of the single battery at the current moment according to the formula (1),
wherein ,
the internal resistance of the single battery at the current moment, t is the current moment, t-1 is the last moment of the current moment, n represents the nth battery in the battery pack, Vn(t) is the voltage of the single cell at time t, Vn(t-1) is the voltage of the single cell at t-1, In(t) is the current of the single cell at time t, In(t-1) is the current of the single cell at t-1;
calculating the internal resistance trend difference of the nth battery according to the formula (2),
wherein ,
is the internal resistance trend difference of the nth battery,
the initial internal resistance value of the nth battery;
judging whether the internal resistance trend difference is larger than 0;
under the condition that the internal resistance trend difference is judged to be larger than 0, the thermal runaway of the battery is judged;
and under the condition that the internal resistance trend difference is judged to be less than or equal to 0, judging that the thermal runaway of the battery does not occur.
7. The system of claim 5, wherein the controller is to:
calculating the effective value of the internal resistance trend difference according to a formula (3),
wherein ,ΔRthdThe effective value of the internal resistance trend difference is obtained;
calculating the internal resistance trend difference according to the formula (4),
judging whether the internal resistance trend difference is larger than or equal to the effective value;
under the condition that the internal resistance trend difference is judged to be larger than or equal to the effective value, the thermal runaway of the battery is judged;
and under the condition that the internal resistance trend difference is judged to be smaller than the effective value, judging that the thermal runaway of the battery does not occur.
8. The system of claim 5, wherein the controller is to:
calculating the total internal resistance trend difference of the battery according to the formula (5),
wherein d (t) is the total tendency difference of the internal resistance of the battery,
the internal resistance trend difference of the kth battery is obtained;
judging whether the total internal resistance trend difference of the battery is larger than or equal to a threshold value alarm value;
under the condition that the total internal resistance trend difference of the battery is judged to be larger than or equal to a threshold value alarm value, judging that the thermal runaway of the battery occurs;
and under the condition that the total internal resistance trend difference of the battery is smaller than the threshold value alarm value, judging that the thermal runaway of the battery does not occur.
9. The system of claim 8, wherein the threshold alarm value comprises a first threshold alarm value and a second threshold alarm value, and wherein the controller is configured to:
judging whether the total internal resistance trend difference of the battery is larger than or equal to the first threshold alarm value;
under the condition that the total internal resistance trend difference of the batteries is judged to be larger than or equal to the first threshold value alarm value, judging whether the total internal resistance trend difference of the batteries is larger than or equal to the second threshold value alarm value;
under the condition that the total internal resistance trend difference of the battery is judged to be larger than or equal to the second threshold value alarm value, judging that the thermal runaway of the battery occurs, and outputting a serious alarm;
under the condition that the trend difference of the total internal resistance of the battery is judged to be smaller than the second threshold value alarm value, judging that the thermal runaway of the battery occurs, and outputting a slight alarm;
and under the condition that the total internal resistance trend difference of the battery is judged to be smaller than the first threshold value alarm value, judging that the thermal runaway of the battery does not occur.
10. A computer-readable storage medium having stored thereon instructions for reading by a machine to cause the machine to perform the method of any of claims 1 to 4.
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