Patent Application
20250180664
A daisy-chain communication link can be established among the BMU 108 and the AFEs 104_1-104_n. Through the daisy-chain communication link, the BMU 108 can control the AFEs 104_1-104_n to monitor the statuses of the battery modules 102_1-102_n, and obtain the status information of the battery modules 102_1-102_n. Specifically, the BMU 108 can send a status monitoring command SMC to the AFEs 104_1-104_n through the daisy-chain communication link, and the status monitoring command SMC is set to instruct the AFEs 104_1-104_n to monitor the statuses of the battery modules. In response to the status monitoring command SMC, the AFEs 104_1-104_n can obtain the status information of the battery modules and send the status information to the BMU 108 through the daisy-chain communication link.
In the daisy-chain communication link, the status monitoring command SMC is relayed to the AFEs 104_1-104_n sequentially. Specifically, the BMU 108 sends the status monitoring command SMC to the AFE 104_1. The status monitoring command SMC is forwarded by the AFE 104_1 to the AFE 104_2, which in turn forwards that command to the AFE 104_3, and so on to the AFE 104_n in sequence. Each AFE monitors the status of a respective battery module in response to the status monitoring command SMC, and sends the obtained status information to the BMU 108 through the daisy-chain communication link. For example, the AFE_1 sends its status information to the BMU 108, the AFE 104_2 sends its status information to the AFE 104_1, which sends the status information from the AFE 104_2 to the BMU 108, and so on.
However, there is a propagation delay for each AFE in forwarding the status monitoring command SMC. As a result, the acquisition time of the status information of the battery module acquired by each AFE of the AFEs 104_1-104_n is different, which may lead to inaccuracy when using the status information of the battery modules 102_1-102_n to determine battery statuses such as state-of-charge (SOC) and state-of-health (SOH).
In an embodiment, a battery monitoring device includes a monitoring circuit, a communication port, and a control circuit coupled to the monitoring circuit and the communication port. The monitoring circuit can sense a status of a first battery module. The communication port can receive a sensing command, provided by a battery management unit, through a serial communication link. The serial communication link includes a set of battery monitoring devices that includes the battery monitoring device. The battery monitoring devices are coupled to a set of battery modules that includes the first battery module. Each device of the battery monitoring devices can sense a status of a respective battery module of the battery modules at a sensing time point. The control circuit can start timing of a preset time delay when the control circuit begins executing the sensing command. The control circuit can also control the monitoring circuit to sense the status of the first battery module when the preset time delay expires such that the monitoring circuit senses the status of the first battery module at a time point that is synchronized with the sensing time point. In addition, the control circuit can control the communication port to send information including the status of the first battery module to the battery management unit through the serial communication link.
Features and advantages of embodiments of the claimed subject matter 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 conjunction 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.
Embodiments of the present invention provide a battery monitoring device, a battery monitoring system, and a method for monitoring a battery pack that includes multiple battery modules. The battery monitoring system can include a serial communication link that includes multiple battery monitoring devices and can also include a battery management unit (BMU) that communicates with each of the battery monitoring devices through the serial communication link. Each of the battery monitoring devices can receive a sensing command from the BMU through the serial communication link, set a respective time delay upon receiving or executing the sensing command, and start sensing a status of a respective battery module when the respective time delay expires. As a result, the battery monitoring devices in the serial communication link can sense statuses of the battery modules synchronously, thereby improving the accuracy of determining the statuses such as SOC and/or SOH of the battery modules.
In an embodiment, each of the battery monitoring devices 204_1-204_n can monitor the status(es) (e.g., voltages, temperature, and/or abnormal conditions, etc.) of a respective battery module. Each of the battery monitoring devices 204_1-204_n can include, but is not limited to, an analog front end (AFE). Each battery module of the battery modules 202_1-202_n can include multiple battery cells.
In the embodiment of
In an embodiment, the battery cells of each battery module 202_1-202_n include rechargeable battery cells such as lithium-ion (Li-ion) battery cells. In other embodiments, the multiple battery cells include other types of rechargeable battery cells such as lead-acid battery cells, nickel-cadmium (NiCd) battery cells, nickel-metal hydride (NiMH) battery cells, sodium battery, or super-capacitors. The battery modules 202_1-202_n can be used in high power application environments, such as electric vehicles (EVs), power walls, and so on. As shown in
As shown in
In an embodiment, the monitoring circuit 212 in each of the battery monitoring devices 204_1-204_n is coupled to a respective battery module of the battery modules 202_1-202_n, and is configured to monitor the status of their respective battery module. To illustrate, taking the kth (k=1, 2, . . . , n) battery monitoring device 204_k as an example, the monitoring circuit 212 in the battery monitoring device 204_k is coupled to the battery module 202_k, and is configured to monitor a status (e.g., a voltage and/or temperature) of the battery module 202_k.
As shown in
In an embodiment, a serial communication link can be established between the BMU 208 and the battery monitoring devices 204_1-204_n. In the example of
As shown in
In an embodiment, the BMU 208 can control, through the linear serial communication link 211, the BJB 210 to monitor a current IBAT flowing through the battery modules 202_1-202_n. For example, in response to a sensing command SC, the BJB_AFE 210_1 of the BJB 210 can monitor the current IBAT of the battery modules 202_1-202_n through the resistive element R0 and send information for the current IBAT of the battery modules 202_1-202_n to the controller 208_2 through the linear serial communication link 211. In addition, the BJB_AFE 210_1 can receive voltage information and/or other status information of the battery modules 202_1-202_n and forward that information to the BMU 208. The BJB_AFE 210_1 can also be referred to as a battery monitoring device 210_1.
In an embodiment, the isolators 206 are used to transmit and receive signals such as, for example, commands provided by the controller 208_2 and information for the statuses of the battery modules 202_1-202_n monitored by the battery monitoring devices 204_1-204_n. More specifically, the isolators 206 can allow the alternating-current (AC) component of the command signals to pass through and can block the direct-current (DC) component of the command signals. As a result, although the battery monitoring devices 204_1-204_n operate with different reference grounds, the isolator 206 can allow adjacently coupled battery monitoring devices to communicate with each other using the AC component of the command signals while isolating the DC component of the command signals from both sides. In an embodiment, each isolator of the isolators 206 includes a capacitor circuit, a transformer, or the like.
As shown in
In an embodiment, a sensing command SC generated by the controller 208_2 can be transmitted in two different (opposite) directions in the looped serial communication link 213: that is, the same command is sent both in the direction of the uplink and in the direction of the downlink. For example, the sensing command SC is represented as an uplink sensing command SC1 and a downlink sensing command SC2. The sensing command SC (uplink sensing command SC1) is transmitted through the uplink of the looped serial communication link 213. The sensing command SC (downlink sensing command SC2) is also transmitted through the downlink of the looped serial communication link 213. Specifically, the uplink sensing command SC1 is transmitted sequentially (e.g., in a daisy-chain communication link) in the order of the Bridge IC 208_1, the BJB 210, and the battery monitoring devices 204_1-204_n. The downlink sensing command SC2 is transmitted sequentially (e.g., as a daisy-chain communication link) in the order of the Bridge IC 208_1, the battery monitoring devices 204_n-204_1, and the BJB 210.
In another embodiment, the sensing command SC includes a first sensing command (e.g., an uplink sensing command SC1) and a second sensing command (e.g., a downlink sensing command SC2) that are not identical. The first sensing command SC1 can be transmitted through the uplink of the looped serial communication link 213, and the second sensing command SC2 can be transmitted through the downlink of the looped serial communication link 213. The first and second commands SC1 and SC2 can be set according to the number of devices in the uplink and the number of devices in the downlink, and according to a propagation delay of each of the devices in the looped serial communication link 213.
Thus, in an embodiment, the sensing command SC can be transmitted through the uplink and downlink of the looped serial communication link 213 in parallel. More specifically, the battery monitoring system 200B can perform a first operation and a second operation in parallel. In the first operation, the Bridge IC 208_1 can transmit the uplink sensing command SC1 to the BJB 210 and a first group of the battery monitoring devices 204_1-204_n through the uplink. In the second operation, the Bridge IC 208_1 can transmit the downlink sensing command SC2 to a second group of the battery monitoring devices 204_1-204_n (e.g., the remainder of the devices that are not in the first group) through the downlink. As a result, the total propagation delay of the sensing command SC reaching all of the battery monitoring devices 204_1-204_n can be reduced, and thus the time for determining battery status such as SOC and/or SOH can be reduced.
As shown in
In this embodiment, the uplink sensing command SC1 and the downlink sensing command SC2 are transmitted in parallel (albeit in different directions) through the looped serial communication link 213. As a result, although each battery monitoring device has a propagation delay T_PD in forwarding the sensing command, the total propagation delay of broadcasting the sensing command to the battery monitoring devices 204_1-204_n can be reduced, and thus the time for determining battery status such as SOC and SOH can be reduced. Moreover, in an embodiment, the uplink sensing command SC1 can be used to instruct the battery monitoring devices 204_1-204_p to monitor the statuses of the battery modules 202_1-202_p, and the downlink sensing command SC2 can be used to instruct the battery monitoring devices 204_(p+1)-204_n to monitor the statuses of the battery modules 202_(p+1)-202_n.
In an embodiment, to further reduce the total propagation delay of the sensing command SC reaching all the battery monitoring devices 204_1-204_n, the value of p is set to a target number (e.g., an integer equal to or close to n/2), which makes the number of battery monitoring devices that receive the uplink sensing command SC1 equal to or just one device different from the number of battery monitoring devices that receive the downlink sensing command SC2. For example, p can be set to 5 if n=11, so that the number of battery monitoring devices (e.g., including the BJB_AFE 210_1 and the battery monitoring devices 204_1, . . . , 204_5) that receive the uplink sensing command SC1 is the same as the number of battery monitoring devices (e.g., including the battery monitoring devices 204_6, . . . , 204_11) that receive the downlink sensing command SC2. For another example, p can be set to 6 if n=12, so that the number of battery monitoring devices that receive the uplink sensing command SC1 is one more than the number of battery monitoring devices that receive the downlink sensing command SC2. For yet another example, p can be set to 5 if n=12, so that the number of battery monitoring devices that receive the uplink sensing command SC1 is one less than the number of battery monitoring devices that receive the downlink sensing command SC2. As a result, the process of receiving the uplink sensing command SC1 by the battery monitoring devices 210_1 and 204_1-204_p and the process of receiving the downlink sensing command SC2 by the battery monitoring devices 204_(p+1)-204_n can be executed in parallel as efficiently as possible, thereby further reducing the total propagation delay of the sensing command SC reaching all the battery monitoring devices 210_1 and 204_1-204_n.
As mentioned in relation to
Specifically, as shown in
In an embodiment, the preset time delays PRE_DLYs for the battery monitoring devices 204_1-204_n are configurable. The preset time delays PRE_DLYs for the battery monitoring devices 204_1-204_n can be configured such that each of the battery monitoring devices start monitoring the statuses of the battery modules 202_1-202_n at or approximately at the same time. The configuration of the preset time delays PRE_DLYs will be described below with reference to
In an embodiment, the battery monitoring devices 204_1-204_n sense the status(es) of their respective battery module synchronously at the time point T_B shown in
In equation (1), PRE_DLYi represents the preset time delay of the battery monitoring device 204_i, n represents the total number of the battery monitoring devices 204_1-204_n in the linear serial communication link 211, P_DLY is equal to or approximately equal to T_PD, and i is an integer representing the position of the battery monitoring device 204_i in the linear serial communication link 211. For example, if the battery monitoring device 204_i is the first device in the serial communication link 211 (next to the BJB 210), then i=1; and if the battery monitoring device 204_i is, for example, the third device in the serial communication link 211, then i=3. In an embodiment, by presetting the time delays PRE_DLY1, PRE_DLY2, . . . , PRE_DLYn for the battery monitoring devices 204_1-204_n, respectively, according to equation (1), the battery monitoring devices 204_1-204_n can sense the status(es) of their respective battery module synchronously (at or approximately at the same time, e.g., at the time point T_B). The phrase “at or approximately at the same time” means that a time difference may exist between the time when a first battery monitoring device senses a status of a first battery module and the time when a second battery monitoring device senses a status of a second battery module (e.g., due to non-ideality of circuit components in the battery monitoring system) and the time difference is negligibly small.
In an embodiment, the time delay PRE_DLYn of the battery monitoring device 204_n is preset to be zero, and therefore the battery monitoring devices 204_1-204_n synchronously sense the battery statuses at the time point T_B. However, the invention is not so limited. In another embodiment, the time delay PRE_DLYn may be set to Δt1 (e.g., a relatively short time interval), and therefore the battery monitoring devices 204_1-204_n synchronously sense the battery statuses at the time point T_B+Δt1 (e.g., the time point T_S1 shown in
In equation (2), PRE_DLYi represents the preset time delay of the battery monitoring device 204_i, n represents the total number of the battery monitoring devices 204_1-204_n in the linear serial communication link 211, P_DLY is equal to or approximately equal to T_PD, and i is an integer representing the position of the battery monitoring device 204_i in the linear serial communication link 211. In an embodiment, by presetting the time delays PRE_DLY1, PRE_DLY2, . . . , PRE_DLYn for the battery monitoring devices 204_1-204_n, respectively, according to equation (2), the battery monitoring devices 204_1-204_n can sense the status(es), e.g., voltage, of their respective battery module synchronously, e.g., at time point T_S1.
Furthermore, in an embodiment, the BJB_AFE 210_1 also includes a control circuit that starts a preset time delay PRE_DLY0 when executing the sensing command SC and controls a monitoring circuit to sense a status, e.g., a current IBAT, of the whole battery pack (including the batteries modules 202_1-202_n) when the time delay PRE_DLY0 expires. The time delay PRE_DLY0 can be set such that the BJB_AFE 210_1 senses the battery current IBAT of the battery pack when the battery monitoring devices 204_1-204_n sense the statuses, e.g., voltages, of the battery modules 202_1-202_n. Thus, the current and voltages of the battery modules 202_1-202_n can be sensed synchronously.
For example, if a propagation delay T_PD0 of the BJB_AFE 2101 is equal to or approximately equal to the propagation delay T_PD of the battery monitoring devices 204_1-204_n, and the preset time delays PRE_DLYs of the battery monitoring devices 204_1-204_n are set according to equation (1), then the preset time delay PRE_DLY0 of the BJB_AFE 210_1 can be set to be equal to n*P_DLY. Similarly, if the propagation delay T_PD0 of the BJB_AFE 210_1 is equal to or approximately equal to the propagation delay T_PD of the battery monitoring devices 204_1-204_n, and the preset time delays PRE_DLYs of the battery monitoring devices 204_1-204_n are set according to equation (2), then the preset time delay PRE_DLY0 of the BJB_AFE 210_1 can be set to be equal to n*P_DLY+Δt1. In other embodiments, if a propagation delay T_PD0 of the BJB_AFE 2101 is very different from the propagation delay T_PD of the battery monitoring devices 204_1-204_n, then the preset time delay PRE_DLY0 of the BJB_AFE 210_1 can be set to be equal to T_PD0+(n−1)*P_DLY or to T_PD0+(n−1)*P_DLY+Δt1.
As mentioned above, in the examples of
With reference now to the embodiment of
Equation (2) is still applicable if modified so that the time delay PRE_DLY0 of the battery monitoring device 210_1 is configured to be p*P_DLY+Δt2, the time delay PRE_DLY1 of the battery monitoring device 204_1 is configured to be (p−1)*P_DLY+Δt2, . . . , and the time delay PRE_DLYp of the battery monitoring device 204_p is configured to be Δt2. Δt2 can represent the difference between the time point T_D and the time point T_S2 (
Similarly, the downlink of the looped serial communication link 213 includes the battery monitoring devices 204_(p+1)-204_n. The battery monitoring device 204_n can be considered as the first battery monitoring device in the downlink of the looped serial communication link 213, the battery monitoring device 204_(n−1) can be considered as the second battery monitoring device in the downlink of the looped serial communication link 213, . . . , and the battery monitoring device 204_(p+1) can be considered as the (n−p)th battery monitoring device in the downlink of the looped serial communication link 213. Again, equation (2) is still applicable if the time delay PRE_DLYn of the battery monitoring device 210_n is configured to be (n−p−1)*P_DLY+Δt3, the time delay PRE_DLY(n−1) of the battery monitoring device 204_(n−1) is configured to be (n−p−2)*P_DLY+Δt3, . . . , and the time delay PRE_DLY(p+1) of the battery monitoring device 204_(p+1) is configured to be Δt3. Δt3 can represent the difference between the time point T_E and the time point T_S2 (
The setting of the value of p can cause the time point T_D and the time point T_E to be sequenced differently on the time axis. Specifically, if p+1<n−p, then the time point T_D precedes the time point T_E (as shown in
According to the above embodiments the preset time delay PRE_DLYi of a battery monitoring device 204_i can be determined according to the position of that battery monitoring device 204_i in a serial communication link (e.g., the linear serial communication link 211, the uplink of the looped serial communication link 213, or the downlink of the looped serial communication link 213), and the propagation delay T_PD of the battery monitoring device 204_i.
As mentioned above, each of the battery modules 202_1-202_n (hereinafter, battery module 202) can include multiple battery cells, and a respective battery monitoring device (hereinafter, battery monitoring device 204) of the devices 204_1-204_n can monitor statuses of the battery cells. In an embodiment, the monitoring circuit 212 of the battery monitoring device 204 can perform a first sensing operation on each battery cell of the multiple battery cells at a first time point to obtain first sensing data and perform a second sensing operation on each battery cell at a second time point to obtain second sensing data. The monitoring circuit 212 can further generate information indicating the status of the battery module 202 according to the first sensing data and the second sensing data. The control circuit 216 of the battery monitoring device 204 can further control the communication port 214 to send information indicating the status of the battery module 202 to the BMU 208 via the serial communication link (e.g., including the linear serial communication link 211 or the looped serial communication link 213). This embodiment will be illustrated below in combination with
In an embodiment, the time interval between the time point T1 and the time point T(2M) includes a middle time point, e.g., (T1+T(2M)/2, which can be referred to as the central or middle sensing time point of the first battery cell BAT1. The central or middle sensing time point of the first battery cell BAT1 can be represented by TC in
The first sensing data of the battery cell BATj (j=1, 2, . . . , M) can include the first sensed voltage of the battery cell BATj monitored at the time point Tj, and the second sensing data of the battery cell BATj can include a second sensed voltage of the battery cell BATj monitored at the time point T(2M+1−j). In a relatively stable situation (e.g., when a charging current or a discharging current of the battery module 202 is relatively stable or unchanged), an average value of the first sensed voltage and the second sensed voltage of a battery cell BATj in the battery module 202 can represent a voltage of the battery cell BATj at the central time point TC. The battery monitoring device 204 can calculate an average value of the first sensed voltage and the second sensed voltage of each of the battery cells BAT1-BATM. The calculated average values can represent the voltages of the battery cells BAT1-BATM at the central time point TC. Thus, the voltages of the battery cells BAT1-BATM can be considered to be synchronously sensed at the central time point TC. As a result, the accuracy of monitoring the statuses of the battery cells BAT1-BATM can be further improved.
In the embodiment of
At step 702, a battery monitoring device 204_i (i=1, 2, . . . , n) of a set of battery monitoring devices 204_1-204_n receives a sensing command SC transmitted by a battery management unit 208 via a serial communication link (e.g., 211 or 213). The serial communication link includes the battery monitoring devices 204_1-204_n.
At step 704, the battery monitoring device 204_i starts the timing of a preset time delay PRE_DLY when the battery monitoring device 204_i begins executing the sensing command SC.
At step 706, the battery monitoring devices 204_1-204_n sense statuses of the battery modules 202_1-202_n at a sensing time point. More specifically, the battery monitoring device 204_i senses a status of the battery module 202_i when the preset time delay PRE_DLY expires such that the battery monitoring device 204_i senses the status of the battery module 202_i at a time point that is synchronized with the abovementioned sensing time point.
At step 708, the battery monitoring device 204_i sends information including the status of the battery module 202_i to the battery management unit 208 through the serial communication link.
Accordingly, embodiments according to the present invention provide battery monitoring systems. In an embodiment, the battery monitoring system includes multiple monitoring devices capable of synchronously sensing statuses of battery modules by setting time delays for the start time points of their sensing processes. Thus, the accuracy of determining statuses such as the state-of-charge (SOC) and the state-of-health (SOH) of the battery modules can be improved. In an embodiment, the monitoring device (or each of the monitoring devices) can further sense a voltage of each cell of battery cells in a battery module twice during a preset period to obtain two voltages and can calculate an average value of the two voltages. As such, the monitoring device can provide a set of average values representing a set of cell voltages of the battery cells measured synchronously at a time point (e.g., the abovementioned middle time point TC or T′C). This can further improve the accuracy of determining the SOC and SOH of the battery modules.
Additionally, in an embodiment, the BMU 208 can periodically send a sensing command SC to the battery modules to acquire/obtain multiple sets of data over multiple cycles or time frames, and each set of the data is acquired/obtained in a respective cycle/time frame of these multiple cycles/time frames. The BMU 208 can analyze the multiple sets of data, based on electrochemical impedance spectroscopy (EIS) and a fast Fourier transform (FFT), to generate impedance spectrums. The impedance spectrums of the battery modules can be used to determine or estimate the SOC and SOH of the battery modules. The impedance spectrums of the battery modules may also be used to estimate the internal temperature of each of the battery modules to further improve the accuracy of determining the SOC of the battery modules.
In an embodiment, the EIS provides a technique of transforming a resistance timing diagram (e.g., a time-domain graph) to an impedance spectrum (e.g., a frequency-domain graph). In an embodiment, the FFT technology provides a methodology of performing the transformation.
In an embodiment, as mentioned above, the current and voltages of the battery modules 202_1-202_n can be sensed synchronously, and they can be sensed periodically. The BMU 208 can acquire/obtain a current value IBATA and voltage values V1A, V2A, . . . , and VnA (hereinafter, a first dataset) of the battery modules 202_1-202_n that are measured synchronously in a first cycle/time frame, and acquire/obtain a current value IBATB and voltage values V1B, V2B, . . . , VnB (hereinafter, a second dataset) of the battery modules 202_1-202_n that are measured synchronously in a second cycle/time frame after the first cycle/time frame. The BMU 208 can estimate internal resistances of the battery modules 202_1-202_n based on the first and second datasets.
By way of example, the battery module 202_1 includes multiple battery cells and an internal resistance R1. Thus, in the first cycle or time frame, the voltage V1A of the battery module 202_1 can be given by: V1A=VCELLSA+IBATA*R1, where VCELLSA represents the total voltage of the battery cells in the battery module 202_1. In the second cycle or time frame, the voltage V1B of the battery module 202_1 can be given by: V1B=VCELLSB+IBATB*R1, where VCELLSB represents the total voltage of the battery cells in the battery module 202_1. In an embodiment, the time gap between the first and second cycles (or time frames) is relatively short, and therefore the battery cells' total voltage is relatively stable, e.g., VCELLSB=VCELLSA. Accordingly, the internal resistance R1 of the battery module 202_1 can be calculated as follows: R1=(V1B−V1A)/(IBATB−IBATA). Similarly, the internal resistances R2, R3, . . . , Rn of the battery modules 202_2-202_n can be calculated as follows: R2=(V2B−V2A)/(IBATB−IBATA), R3=(V3B−V3A)/(IBATB−IBATA), . . . , Rn=(VnB−VnA)/(IBATB−IBATA).
Accordingly, the BMU 208 can measure the battery current IBAT and the battery voltages V1, V2, . . . , and Vn of the battery modules 202_1-202_n periodically such that the BMU 208 can calculate/obtain multiple values of the internal resistance of the battery module 202_1, multiple values of the internal resistance of the battery module 202_2, . . . , and multiple values of the internal resistance of the battery module 202_n. The BMU 208 can further apply the fast Fourier transform to the multiple values of the internal resistance to generate an impedance spectrum of each of the battery modules 202_1-202_n. In an embodiment, an impedance spectrum of a battery module can have a particular pattern in a particular situation. For example, when the battery module is in an idle state (or in a sleep mode), the impedance spectrum of the battery module may include a first pattern. When the battery module is in a fast-charging mode, the impedance spectrum of the battery module may include a second pattern. When the battery module is switching from a sleep mode to an active mode, the impedance spectrum of the battery module may include a third pattern. As a result, the BMU 208 can determine whether a battery module is in a healthy state by analyzing a real-time impedance spectrum of the battery module. Moreover, in an embodiment, information in an impedance spectrum of a battery module may indicate the internal temperature and/or an SOC of the battery module. Accordingly, the BMU 208 may improve the estimation of the SOC of the battery module based on the real-time impedance spectrum. Detailed explanations will be provided in combination with
According to the Fourier theorem, any periodic function can be represented as a sum of sinusoidal functions (sines and cosines) with different frequencies, amplitudes, and phase shifts. Non-periodic functions can also be represented by a series of sinusoidal components using the fast Fourier transform.
As mentioned above, the current and voltages of the battery modules 202_1-202_n can be sensed synchronously and periodically. In the example of
In an embodiment, the BMU 208 can apply the fast Fourier transform on the internal resistance values R1P, R2P, R3P, etc., of the battery module 202_i to generate information for an impedance spectrum of the battery module 202_i. In
In an embodiment, as used herein, the phrase “apply the fast Fourier transform on the internal resistance values” and the like mean applying the fast Fourier transform algorithm on the internal resistance values to generate a result of the algorithm, and the result includes information for the impedance spectrum. For example, an algorithm module (e.g., represented by computer-readable instructions) for the fast Fourier transform can be stored in a storage unit (e.g., a non-transitory computer storage media) of the BMU 208. The BMU 208 can execute the algorithm module based on the internal resistance values or, in other words, can input the internal resistance values to the algorithm module. As a result, the BMU 208 can obtain the information for the impedance spectrum from the algorithm module.
As mentioned above, the impedance spectrum of the battery module 202_i can have a particular pattern in a particular situation. If the battery module 202_i is in a healthy state, then the information for the real-time impedance spectrum will match pre-stored information for the impedance spectrum. More specifically, in an embodiment, before mass-producing the battery modules, a testing process is performed on samples of the battery modules. The testing process may include measuring the current and voltage of a sample of the battery modules (hereinafter, a battery-module sample) in different situations, e.g., different operation modes, different SOCs, different temperatures, etc. The testing process may further include generating information (hereinafter, after-testing information) for impedance spectrums for the battery-module sample based on the measurement results. In an embodiment, the after-testing information may be pre-stored a storage unit (e.g., a non-transitory computer storage media). The BMU 208 can acquire the after-testing information from the storage unit.
Accordingly, in an embodiment, if the real-time information for the impedance spectrum of a battery module does not match the pre-stored information for the impedance spectrum, then the BMU 208 may determine that a fault or a potential fault is present in the battery module. In an embodiment, a first impedance spectrum does not match a second impedance spectrum when a difference between the first impedance spectrum and the second impedance spectrum is greater than a preset threshold or is outside of a predetermined standard.
In addition, in the testing process, an impedance spectrum versus SOC database may be generated by mapping the impedance spectrum to the SOC of the battery-module sample. Similar to the after-testing information, the impedance spectrum versus SOC database may be stored in an abovementioned storage unit. As a result, the BMU 208 may determine an SOC of the battery module by comparing the real-time information for the impedance spectrum with the information in the impedance spectrum versus SOC database.
Moreover, in the testing process, an impedance spectrum versus temperature database may be generated by mapping the impedance spectrum to the internal temperature of the battery-module sample. The impedance spectrum versus temperature database may be stored in the abovementioned storage unit. As a result, the BMU 208 may determine the internal temperature of the battery module by comparing the real-time information for the impedance spectrum with the information in the impedance spectrum versus temperature database. The determined internal temperature value can be used to further improve the accuracy of determining the SOC of the battery module.
Furthermore, as mentioned above, the current and voltages of the battery modules 202_1-202_n can be sensed synchronously and periodically. Thus, the BMU 208 can generate a set of impedance spectrums respectively corresponding to the battery modules 202_1-202_n, and the impedance spectrums can represent statuses of the battery modules 202_1-202_n at the same time or in the same time frame. In an embodiment, the BMU 208 may compare the impedance spectrums with each other to determine whether a fault (or a potential fault) is present in a battery module of the battery modules 202_1-202_n. For example, if the BMU 208 identifies an impedance spectrum that is very different from the other impedance spectrums, then the BMU 208 may determine that a fault (or a potential fault) is present in the battery module corresponding to that impedance spectrum.
Accordingly, an embodiment according to the present invention provides a battery monitoring system that synchronously and periodically measures/senses a battery current and battery voltages of a set of battery modules. Based on the synchronously and periodically measured current and voltages, the battery monitoring system can calculate multiple sets of values for the internal resistances of the battery modules, and apply a fast Fourier transform to the internal resistance values to generate information for impedance spectrums of the battery modules. The battery monitoring system may further analyze the impedance spectrums to determine, for example, an SOC, an SOH, and/or internal temperature of the battery modules. Furthermore, in an embodiment, the battery monitoring system may compare the impedance spectrums with each other to determine whether a fault (or a potential fault) is present in a battery module of the battery modules.
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.
