Patent Application
20210199722
Usually, a nickel tape or a wire is used as a connecting wire to connect a battery management system with each cell, to enable the battery management system to measure the voltage of each cell and to perform a corresponding protection operation if needed. If the connecting wire and/or related components in the battery management system are abnormal, the measured voltage of each cell will not be accurate, in which case the battery management system may perform the wrong protection operation.
In a conventional method, the voltage value on a capacitor in the battery management system is compared with the cell tap open threshold VCTO, to determine whether the measured voltage of each cell is accurate. However, the conventional method only can determine the inaccuracy of the measured voltage of each cell caused by an abnormal connection. Thus, the conventional method results in an incorrect diagnosis, which will cause the battery management system to perform the incorrect protection operation.
Embodiments in accordance with the present invention provide methods for detecting whether a battery management system is abnormal that addresses the problem with the conventional method discussed above.
In embodiments, a method for detecting whether a battery management system is abnormal, wherein the battery management system comprises a measure unit, a control unit, a first monitoring resistor, a second monitoring resistor, a first capacitor, a first switch and a first balance resistor, where a first cell in a battery pack is coupled to the first monitoring resistor, the second monitoring resistor, the first capacitor, the first switch and the first balance resistor, the method comprising: calculating, using the control unit, a value of a theoretical time constant corresponding to the first cell; determining, a preset range of the theoretical time constant according to the value of the theoretical time constant; controlling, using the control unit, the first switch to successively turn off for a first time period, turn on for a second time period, and turn off for a third time period; controlling, using the control unit, the measure unit to measure a voltage value on the first capacitor at the end of the first time period, to produce a measured voltage value of the first cell; controlling, using the control unit, the measure unit to measure voltage values on the first capacitor at least at one time point in the third time period, to produce measured capacitance voltage values; determining, using the control unit, a value of a measured time constant according to at least one of the measured capacitance voltage values and the measured voltage value of the first cell; and determining, using the control unit, whether the battery management system is abnormal, where the battery management system is abnormal if the value of the measured time constant exceeds the preset range of the theoretical time constant.
In embodiments, a battery management system, includes: a measure unit; a control unit coupled to the measure unit; a first monitoring resistor coupled to the measure unit; a second monitoring resistor coupled to the measure unit; a first capacitor coupled to the measure unit; a first switch coupled to the measure unit; and a first balance resistor coupled to the measure unit, where a first cell in a battery pack is coupled to the first monitoring resistor, the second monitoring resistor, the first capacitor, the first switch, and the first balance resistor, where the battery management system is configured to execute a method including: calculating, using the control unit, a value of a theoretical time constant corresponding to the first cell; determining a preset range of the theoretical time constant according to the value of the theoretical time constant; controlling, using the control unit, the first switch to successively turn off for a first time period, turn on for a second time period, and turn off for a third time period; controlling, using the control unit, the measure unit to measure a voltage value on the first capacitor at the end of the first time period, to produce a measured voltage value of the first cell; controlling, using the control unit, the measure unit to measure voltage values on the first capacitor at least at one time point in the third time period, to produce measured capacitance voltage values; determining, using the control unit, a value of a measured time constant according to at least one of the measured capacitance voltage values and the measured voltage value of the first cell; and determining, using the control unit, whether the battery management system is abnormal, where the battery management system is abnormal if the value of the measured time constant exceeds the preset range of the theoretical time constant.
Features and advantages of embodiments of the present invention will become apparent as the following detailed description proceeds, and upon reference to the drawings, wherein like numerals depict like parts, and in which:
Reference will now be made in detail to the embodiments of the present invention. While the invention will be described in combination with these embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.
Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention.
Some portions of the detailed descriptions that follow are presented in terms of procedures, logic blocks, processing, and other symbolic representations of operations on data bits within a computer memory. These descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. In the present application, a procedure, logic block, process, or the like, is conceived to be a self-consistent sequence of steps or instructions leading to a desired result. The steps are those utilizing physical manipulations of physical quantities. Usually, although not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated in a computing system. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as transactions, bits, values, elements, symbols, characters, samples, pixels, or the like.
It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present disclosure, discussions utilizing terms such as “acquiring,” “determining,” “controlling,” “measuring,” “averaging,” “calculating,” or the like, refer to actions and processes of a computing system or similar electronic computing device or processor. A computing system or similar electronic computing device manipulates and transforms data represented as physical (electronic) quantities within the computing system memories, registers or other such information storage, transmission or display devices.
In an embodiment, the battery pack includes a cell CELL1, CELL 2, . . . , CELLn, which are coupled in series. The battery management system 100 includes monitoring resistors RF0, RF1, . . . , RFn, capacitors CF1, CF2, . . ., CFn, balance resistors RB1, RB2, . . . , RBn, switches SW1, SW2, . . . , SWn, a measure unit 120, and a control unit 110.
A monitoring resistor RFj (j=1, 2, . . . , n) is coupled to a positive electrode of a cell CELLj or a negative electrode of a cell CELL(j+1). A monitoring resistor RFO is coupled to a negative electrode of a cell CELL1. A capacitor CFj (j=1, 2, . . . , n) is connected between a monitoring resistor RF(j−1) and a monitoring resistor RFj. The monitoring resistors RFO, RF1, RFn and capacitors CF1, CF2, . . . , CFn together form Resistor-Capacitance (RC) filters. The RC filters are operable for filtering out the high frequency components of voltages provided by the cells, thus eliminating unwanted noise components.
The measure unit 120 is coupled to the monitoring resistors RF0, RF1, . . . , RFn, and is operable for measuring voltages of the cells in the battery pack. For example, the measure unit 120 determines a voltage VCELL2 of the cell CELL2 by measuring the difference between a voltage at a node N2 and a voltage at a node N1.
A balance resistor RBj (j=1, 2, . . . , n) is coupled to a switch SWj in series. Both a balance resistor RBj and the switch SWj are operable for balancing a voltage of the cell CELLj. For example, in the discharging process, if a difference between a voltage VCELL2 (e.g., 3V) of the cell CELL2 and a voltage VCELL1 (e.g., 3.4V) of the cell CELL1 is greater than a balance threshold (e.g., 0.1V), then the switch SW1 is turned on and the switch SW2 is turned off, the cell CELL1 discharges and a discharge current flows through a balance resistor RB1. Consequently, the difference between VCELL2 and VCELL1 decreases, until the difference is less than the balance threshold. In an embodiment of the present invention, both the balance resistor RBj and the switch SWj are operable for detecting whether the battery management system 100 is abnormal. A detailed description is given below.
The control unit 110 includes a memory 111 and a microcontroller unit 112. Program codes are written into the microcontroller unit 112. The microcontroller unit 112 is configured to include or execute a timer 113, to enable the microcontroller unit 112 to run the program code according to the time sequence set by the timer 113, thereby realizing the control function and the data processing function. The memory 111 is operable for storing data, such as the theoretical time constant.
Specifically, the control unit 110 controls the switches SW1, SW2, . . . , SWn to turn on/off, controls the measure unit 120 to measure a voltage on the capacitor CFj, and determines the measured time constant. Because the theoretical time constant and the preset range of the theoretical time constant are determined experimentally (e.g., before the battery management system 100 is put into use), they are stored in the memory 111. If the measured time constant is in the preset range of the theoretical time constant, then the control unit 110 determines the battery management system 100 is normal; otherwise, the battery management system 100 is abnormal.
Embodiments according to the present invention are not limited to the configuration of
(1) The Battery Management System 100 is Normal.
In the time period from t1 to t2 (where the time period from t1 to t2 is the first time period T1 of
In the time period from t2 to t3 (where the time period from t2 to t3 is the second time period T2 of
In the time period from t3 to t4 (where the time period from t3 to t4 is the third time period T3 of
In the present embodiment, time t31, time t32, . . . , time t3n are selected in the time period from t3 to t4, and the measure unit 120 respectively measures voltage values V1, V2, . . . , Vn, on the capacitor CFj at time t31, time t32, . . . , time t3n, to determine (V1, Δt1), (V2, Δt2), . . . , (Vn, Δtn), where Δt1 represents the length of time between time t3 and time t31, Δt2 represents the length of time between time t3 and time t32, . . . , and Δtn represents the length of time between time t3 and time t3n. In the time period from t3 to t4, the monitoring resistors RFj, RF(j−1) and the capacitor CFj form a RC circuit, and the theoretical time constant τ=Δi/ln[K/(VCELLj−Vi)], where K represents a coefficient, i=1, 2, . . . , n. (V1, Δt1), (V2, Δt2), . . . , (Vn, Δtn) are substituted in the above equation to determine the coefficient K and the theoretical time constant τ. In the present embodiment, K=VCELLj−VE.
The preset range of the theoretical time constant τ is determined by an allowable limit of error. For example, if the theoretical time constant τ is equal to A and the allowable limit of error is ±1/5, the preset range of the theoretical time constant τ=A±1/5. In addition, each RC circuit is located in a different position in the battery management system 100, so the theoretical time constant τ corresponding to each RC circuit is not equal.
(2) The Battery Management System 100 is Abnormal.
Abnormities include an abnormal connection and an abnormal component. If the two terminals of the cell CELLj are not properly connected to the battery management system 100 (e.g., broken or degraded or not operating satisfactorily), then the connection between the battery management system 100 and the cell CELLj is referred to herein as an abnormal connection. If any of the capacitor CFj, the monitoring resistor RFj, and the monitoring resistor RF(j−1) is inoperative (e.g., a leakage current of the capacitor CFj, the resistance values of the monitoring resistor RFj, and/or the monitoring resistor RF(j−1) are increased/decreased), then this condition is referred to herein as an abnormal component.
For example, if the connection between the battery management system 100 and the cell CELLj is broken, then the capacitor CFj cannot be charged in the time period from t3 to t4 and the voltage value on the capacitor CFj remains unchanged from time t3. Therefore, under ideal conditions, if the connection between the battery management system 100 and the cell CELLj is broken, then the voltage value on the capacitor CFj remains unchanged in the time period from t3 to t4.
For example, if a leakage current flows through the capacitor CFj, then the voltage value on the capacitor CFj is less than VE at time t3 and cannot be recovered to VCELLj at time t4. For example, if the resistance value RRFj of the monitoring resistor RFj and/or the resistance value RRF(j−1) of the monitoring resistor RF(j−1) are increased, then the voltage value on the capacitor CFj can decrease to a voltage value near VE at time t3 and cannot be recovered to VCELLj at time t4. For example, if the resistance value RRFj of the monitoring resistor RFj and/or the resistance value RRF(j−1) of the monitoring resistor RF(j−1) are decreased, then the voltage value on the capacitor CFj can decrease to a voltage value near VE at time t3 and can be recovered to VCELLj before time t4. Therefore, if one or more components among the capacitor CFj, the monitoring resistor RFj, and the monitoring resistor RF(j−1) cannot work effectively, then the variation curve of the voltage values on the capacitor CFj in the time period from t3 to t4 will deviate from the curve of
In summary, if any of the above abnormities has occurred in the battery management system 100, then the variation curve of the voltage values on the capacitor CFj in the time period from t3 to t4will deviate from the
In step 401, when the battery management 100 is normal, the control unit 110 controls the switch SWj to turn off in the time period from t1 to t2, turn on in the time period from t2 to t3, and turn off in the time period from t3 to t4, where t2−t1=T1, t3−t2=T2, and t4−t3=T3.
In step 402, the control unit 110 controls the measure unit 120 to measure the voltage value on the capacitor CFj at time t2, to produce the voltage VCELLj of the cell CELLj.
In step 403, the control unit 110 controls the measure unit 120 to measure the voltage values on the capacitor CFj at least at one time point in the time period from t3 to t4, to produce measured capacitance voltage value(s). The control unit 110 determines a theoretical time constant according to at least one measured capacitance voltage value and the measured voltage value VCELLj of the cell CELLj. In an embodiment, the theoretical time constant is an experimentally determined value. Methods for determining the measured time constant are described in conjunction with the embodiments in
In step 404, a preset range of the theoretical time constant is determined according to the theoretical time constant. Both the theoretical time constant and the preset range of the theoretical time constant are stored in the memory 111 of the control unit 110.
In step 405, when detecting whether the battery management system 100 is abnormal, the control unit 110 controls the switch SWj to turn off in the time period from t5 to t6, turn on in the time period from t6 to t7, and turn off in the time period from t7 to t8, where t6−t5=t2−t1=T1, t7−t6=t3−t2=T2, and t8−t7=t4−t3=T3.
In step 406, the control unit 110 controls the measure unit 120 to measure the voltage value on the capacitor CFj at time t6, to produce the voltage VCELLj of the cell CELLj.
In step 407, the control unit 110 controls the measure unit 120 to measure the voltage values on the capacitor CFj at least at one time point in the time period from t7 to t8, to produce measured capacitance voltage values. The control unit 110 determines a measured time constant according to at least one measured capacitance voltage and the measured voltage value of the cell CELLj. Methods for determining the measured time constant are described in conjunction with the embodiments in
In step 408, the control unit 110 determines whether the measured time constant is in the preset range of the theoretical time constant. If yes, then step 408 is followed by step 410; otherwise, step 408 is followed by step 409.
In step 409, the control unit 110 determines that the battery management system 100 is abnormal, and generates an alarm to alert the users.
In step 410, the control unit 110 determines that the battery management system 100 is normal.
In step 411, the control unit 110 determines whether all of the cells are detected. If yes, then step 411 is followed by step 413; otherwise, step 411 is followed by step 412.
In step 412, the battery management system 100 starts to detect the next cell, and the method returns to step 405.
In step 413, the detection process of
Methods for determining the theoretical time constant are similar to the methods for determining the measured time constant.
In step 601, the control unit 110 controls the switch SWj to turn off in the time period from t5 to t6, turn on from t6 to t7, and turn off in the time period from t7 to t8, where t6−t5=t2−t1=T1, t7−t6=t3−t2=T2, and t8−t7=t4−t3=T3.
In step 602, the control unit 110 controls the measure unit 120 to measure the voltage value on the capacitor CFj at time t6, to produce the voltage VCELLj of the cell CELLj.
In step 603, the control unit 110 controls the measure unit 120 to measure the voltage value V1 on the capacitor CFj at time t71 in the time period from t7 to t8, to determine (V1, Δt1), where Δt1 is the length of time between t1 and t71.
In step 604, the control unit 110 determines the measured time constant according to the equation τ=Δt1/ln[K/(VCELLj−V1)]. In the present embodiment, K=VCELLj−VE.
In step 701, the control unit 110 controls the switch SWj to turn off in the time period from t5 to t6, turn on in the time period from t6 to t7, and turn off in the time period from t7 to t8, where t6−t5=t2−t1=T1, t7−t6=t3−t2=T2, and t8−t7=t4−t3=T3.
In step 702, the control unit 110 controls the measure unit 120 to measure the voltage values on the capacitor CFj at time t6, to produce the voltage VCELLj of the cell CELLj.
In step 703, the control unit 110 controls the measure unit 120 to measure the voltage value V1 on the capacitor CFj at time t71 in the time period from t7 to t8, to determine (V1, Δt1), where Δt1 is the length of time between t7 and t71.
In step 704, the control unit 110 controls the measure unit 120 to measure the voltage value V2 on the capacitor CFj at time t72 in the time period from t7 to t8, to determine (V2, Δt2), where Δt2 is the length of time between t7 and t72, and Δt2 is not equal to Δt1.
In step 705, the control unit 110 determines the measured time constant τ according to the equation τ=(Δt2−Δt1)/ln[(V1−VCELLj)/(V2−VCELLj)].
In step 801, the control unit 110 controls the switch SWj to turn off in the time period from t5 to t6, turn on in the time period from t6 to t7, and turn off in the time period from t7 to t8, where t6−t5=t2−t1=T1, t7−t6=t3−t2=T2, and t8−t7=t4−t3=T3.
In step 802, the control unit 110 controls the measure unit 120 to measure the voltage value on the capacitor CFj at time t6, to produce the voltage VCELLj of the cell CELLj.
In step 803, the control unit 110 controls the measure unit 120 to measure the voltage value V1 on the capacitor CFj at time t71 in the time period from t7 to t8, to determine (V1, Δt1), where Δt1 is the length of time between t7 and t71.
In step 804, the control unit 110 controls the measure unit 120 to measure the voltage value V2 on the capacitor CFj at time t72 in the time period from t7 to t8, to determine (V2, Δt2), where Δtn is the length of time between t7 and t72, and Δt2 is not equal to Δt1.
In step 805, this process continues until the control unit 110 controls the measure unit 120 to measure the voltage value Vn on the capacitor CFj at time t7n in the time period from t7 to t8, to determine (Vn, Δtn), where Δtn is the length of time between t7 and t7n. In the embodiment, Δt1, Δt2, . . . , Δtn are not equal to each other. In other embodiments, Δtn≠Δ(tn−1), . . . , Δt3≠Δt2, Δt2≠Δt1. Here, two adjacent time periods are not equal.
In step 806, the control unit 110 determines a first time constant τ1 according to the equation τ1=(Δt2−Δt1)/ln[(V1−VCELLj)/(V2−VCELLj)].
In step 807, the control unit 110 determines a second time constant T2 according to the equation τ2=(Δt3−Δt2)/ln[(V2−VCELLj)/(V3−VCELLj)].
In step 808, this process continues until the control unit 110 determines a (n−1)th time constant Δ(n−1) according to the equation Δ(n−1)=(Δtn−Δt(n−1))/ln[(V(n−1)−VCELLj)/(Vn−VCELLj)].
In step 809, the control unit 110 averages τ1, τ2, . . . , τ(n−1) to determine the measured time constant. In other embodiments, other methods can be used to calculate τ1, τ2, . . . , τ(n−1) to determine the measured time constant.
In step 901, the control unit 110 controls the switch SWj to turn off in the time period from t5 to t6, from t7 to t8, and from t9 to t10, and turn on in the time period from t6 to t7 and from t6 to t9, where t6−t5=t2−t1=T1, t7−t6=t3−t2=T2, and t8−t7=t4−t3=T3.
In step 902, the control unit 110 controls the measure unit 120 to measure the voltage value on the capacitor CFj at time t6, to produce the voltage VCELLj of the cell CELLj.
In step 903, the control unit 110 controls the measure unit 120 to measure the voltage value V1 on the capacitor CFj at time t71 in the time period from t7 to t8, to determine (V1, Δt1), where Δt1 is the length of time between t7 and t71.
In step 904, the control unit 110 controls the measure unit 120 to measure the voltage value V2 on the capacitor CFj at time t72 in the time period from t9 to t10, to determine (V2, Δt2), where Δt2 is the length of time between t9 and t72, and Δt2 is not equal to Δt1.
In step 905, the control unit 110 determines the measured time constant τ according to the equation τ=(Δt2−Δt1)/ln[(V1−VCELLj)/(V2−VCELLj)].
In step 1101, the control unit 110 controls the switch SWj to turn off in the time period from t5 to t6, from t7 to t8, from t9 to t10, and from t(5+2n) to t(6+2n), and turn on in the time period from t6 to t7, from t8 to t9, and from t10 to t11, n=3, 4, . . . , where t6−t5=t2−t1=T1, t7−t6=t3−t2=T2, and t8−t7=t4−t3=T3.
In step 1102, the control unit 110 controls the measure unit 120 to measure the voltage value V1 on the capacitor CFj at time t71 in the time period from t7 to t8, to determine (V1, Δt1), where Δt1 is the length of time between t7 and t71.
In step 1103, the control unit 110 controls the measure unit 120 to measure the voltage value V2 on the capacitor CFj at time t72 in the time period from t9 to t10, to determine (V2, Δt2), where Δt2 is the length of time between t9 and t72, and Δt2 is not equal to Δt1.
In step 1104, this process continues until the control unit 110 controls the measure unit 120 to measure the voltage value Vn on the capacitor CFj at time t7n in the time period from t(5+2n) to t(6+2n), to determine (Vn, Δtn), where Δtn is the length of time between t(5+2n) and t7n. In an embodiment, Δt1, Δt2, . . . , Δtn are not equal to each other. In other embodiments, two or more of Δt1, Δt2, . . . , Δtn can be equal.
In step 1105, based on (V1, Δt1), (V2, Δt2), . . . , (Vn, Δtn), the control unit 110 uses the least square method to fit the variation curve of the voltage value on the capacitor CFj, to determine the measured time constant. In other embodiments, other methods can be used to fit the variation curve of the voltage value on the capacitor CFj based on (V1, Δt1), (V2, Δt2), . . . , (Vn, Δtn), to determine the measured time constant.
The first stage 1210 includes steps 1201 and 1202.
In step 1201, the control unit 110 determines a theoretical time constant corresponding to the first cell CELL1, when the battery management system 100 is normal.
In step 1202, a preset range of the theoretical time constant is determined according to the theoretical time constant.
The second stage 1220 includes steps 1203 through 1207.
In step 1203, the control unit 110 controls the first switch SW1 to successively turn off for a first time period T1, turn on for a second time period T2, and turn off for a third time period T3.
In step 1204, the control unit 110 controls the measure unit 120 to measure a voltage value on the first capacitor CF1 at the end of the first time period T1, to produce a measured voltage value of the first cell CELL1.
In step 1205, the control unit 110 controls the measure unit 120 to measure voltage values on the first capacitor CF1 at least at one time point in the third time period T3, to produce measured capacitance voltage values.
In step 1206, the control unit 110 determines a value of a measured time constant according to at least one measured capacitance voltage value and the measured voltage value of the first cell CELL1.
In step 1207, the control unit 110 determines that the battery management system 100 is abnormal, if the value of the measured time constant exceeds the preset range of the theoretical time constant.
As mentioned above, embodiments according to the present invention pertain to methods for detecting whether a battery management system is abnormal. The method can accurately detect whether the battery management system is abnormal (e.g., the connection between the battery management system and a cell CELLj is degraded or broken, the RRFj and/or the RRF(j−1) are increased/decreased, or a leakage current of the capacitor CFj), thereby improving the detection accuracy.
While the foregoing description and drawings represent embodiments of the present invention, it will be understood that various additions, modifications, and substitutions may be made therein without departing from the spirit and scope of the principles of the present invention as defined in the accompanying claims. One skilled in the art will appreciate that the invention may be used with many modifications of form, structure, arrangement, proportions, materials, elements, and components and otherwise, used in the practice of the invention, which are particularly adapted to specific environments and operative requirements without departing from the principles of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims and their legal equivalents, and not limited to the foregoing description.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202110175863.2 | Feb 2021 | CN | national |
This application is a continuation-in-part application of the co-pending U.S. application, Ser. No. 15/959,064, titled “Open Cell Detection Method and Open Cell Recovery Detection Method in A Battery Management System,” filed on Apr. 20, 2018, which is hereby incorporated by reference in its entirety. This application also claims priority to Chinese Patent Application No. 202110175863.2, titled “Detecting Whether a Battery Management System is Abnormal,” filed on Feb. 9, 2021, with the National Intellectual Property Administration of the People's Republic of China (CNIPA).
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15959064 | Apr 2018 | US |
| Child | 17204759 | US |
