Battery management system with on-board limited energy excitation real-time ac impedance detection

Abstract

A battery management system (BMS) for detecting battery cells of a battery pack using AC impedance. The BMS controller generates a pulse modulated signal to an on-board excitation regulator of a synchronous buck converter or the like, and performs sweep control of the modulated signal to modulate a capacitor or the like finite energy cell. The capacitor modulated signal is applied as an AC excitation to the terminals of the battery pack. The voltage of the battery pack resulting from synchronous sampling is a response to the AC excitation signal. The AC excitation signal current and the response signal battery voltage are processed, Fourier transformed to yield corresponding Nyquist plots. Curve shifts can indicate aging of the battery cells. The capacitor generating the AC excitation signal draws only minimal energy from the battery pack, so AC impedance detection can be performed in all modes including charging, discharging and idle modes without the need for an external power source.

Description

Technical Field

[0001] This invention relates to a battery management system, and more specifically, to the real-time detection of battery AC impedance. Background Technology

[0002] Large systems such as electric vehicles (EVs) are powered by battery packs, which are managed by a battery management system (BMS) that controls the charging and discharging of the battery packs. The BMS may also have an idle mode, in which the battery pack is disconnected from the charger and load.

[0003] A Battery Management System (BMS) can monitor the health or aging of a battery pack. An auxiliary charger or power source can generate an AC signal that is applied to the battery to measure its impedance. Some of these AC detection systems only operate when power is available and the battery is being charged by the charger in charging mode. More recently, it has also emerged that external power can be used to detect the battery in idle mode.

[0004] While these battery detection systems are useful, there is a desire for a real-time battery detection system that can operate and detect the battery in charging, discharging, and idle modes. For example, it would be desirable to perform AC impedance detection on the battery while the EV is running (discharging mode), charging (charging mode), and when the EV is neither charging nor discharging (idle mode). Such a real-time online detection system could detect battery problems much earlier, without waiting until charging mode. For example, if a battery cell is damaged due to a rock puncturing the battery pack while driving, or if a battery cell is intentionally damaged while the EV is parked and not charging, the battery problem could be detected without waiting for the EV to be connected to the charger.

[0005] During battery testing, the BMS or testing system generates an AC excitation signal and applies it to the battery pack, while simultaneously measuring the battery pack's response to the AC excitation signal. This AC excitation signal can be generated using the charger's energy in charging mode. However, for discharging and idle modes, the charger may not be usable, thus requiring an external power source to generate the AC excitation signal during discharging and idle modes. However, this additional external power source is not desirable.

[0006] Therefore, it is necessary to generate an AC excitation signal without an external power source or charger. The battery pack itself can provide power, but it is undesirable to draw significant energy from the battery pack to generate the AC excitation signal, as this would deplete the battery's capacity. Some AC impedance sensing systems have a large DC component, which results in substantial current consumption. If the battery is used as the power source for this type of AC excitation signal, this large DC component could excessively drain the battery.

[0007] For those skilled in the art, the following technical issues have become the focus of recent development: The need to generate AC excitation signals using energy stored in a battery pack, without drawing large amounts of energy from the battery pack. The need to generate AC excitation signals using limited energy in storage cells so as to draw only limited energy from the battery pack. The need for a real-time AC impedance battery detection system that can operate in all modes, including charging, discharging, and idle. Summary of the Invention

[0008] The objective of this invention is to provide a battery management detector, a battery management AC impedance detector, and a battery management system with AC impedance detection, which draws limited energy from the battery pack to generate an AC excitation signal and can operate in all modes, including charging, discharging, and idle, thereby overcoming the aforementioned shortcomings of the current technology.

[0009] According to a first aspect of the present invention, a battery management detector is provided, characterized in that it comprises: a first battery connection for connecting to a first terminal of a battery pack; a second battery connection for connecting to a second terminal of the battery pack; a first external connector for connecting to a first terminal of an external charger and a first terminal of an external load; a second external connector for connecting to a second terminal of the external charger and a second terminal of the external load; a power switch connected between the second external connector and the second battery connection, the power switch being controlled by a switch signal in an inactive state to disconnect the second external connector from the second battery connection; a controller that, when a charging / discharging mode is activated, sets the switch signal to an active state, such that the power switch connects the second external connector to the second battery connection, and sets the switch signal to the inactive state when an idle mode is activated; and the controller controls the battery detection process during battery detection. The system generates a modulation signal and outputs a pulse modulation signal, wherein the controller changes the frequency of the modulation signal within a set of frequencies; a finite energy unit stores finite energy insufficient to power the battery management detector, wherein the finite energy is sufficient to generate an AC excitation signal; an onboard excitation regulator receives the pulse modulation signal from the controller and uses the pulse modulation signal to drive the finite energy unit, modulating the finite energy unit to generate the AC excitation signal; wherein the modulation of the AC excitation signal has the frequency of the modulation signal; the onboard excitation regulator injects the AC excitation signal into the first battery connection during battery detection; wherein the modulated AC excitation signal injected into the battery pack causes the battery pack to generate a modulation response of a response signal; and a synchronous sampler samples the response signal in the battery pack and detects the modulation response, wherein the AC excitation signal is generated by the finite energy unit.

[0010] According to a second aspect of the present invention, a battery management AC impedance detector is provided, characterized in that it comprises: a first terminal for connection to a first terminal of a battery pack; a second terminal for connection to a second terminal of the battery pack; a power switch for connecting the second terminal to a second external terminal when a switch signal is activated, and isolating the second terminal from the second external terminal when the switch signal is not activated; wherein an external charger can be connected to the second external terminal and the first terminal to charge the battery pack; wherein an external load can be connected to the second external terminal and the first terminal to be powered by the battery pack; a sampler for receiving a battery test voltage from the battery pack; a controller for activating the switch signal during a charge / discharge mode, and deactivating the switch signal when the battery pack is not charging and the external load is not being driven (idle mode); the control The device generates a modulation signal when detecting the battery pack, and the controller performs frequency sweep control within a frequency range to modulate the modulation signal; a capacitor; a synchronous buck converter, which takes a pulse modulation signal as input and drives the capacitor to generate an AC excitation signal having the frequency range of the modulation signal; and a first current sensor located between the synchronous buck converter and the first terminal; wherein the synchronous buck converter drives the AC excitation signal to a first modulated current flowing through the first current sensor; wherein the first modulated current modulates within the frequency range of the modulation signal; wherein the battery pack's response to the first modulated current modulates the battery test voltage; wherein the sampler detects the modulation response of the battery test voltage from the battery pack; and wherein the controller processes the modulation response and modulation excitation of the first modulated current to generate battery impedance data for the battery pack.

[0011] According to a third aspect of the present invention, a battery management system (BMS) with AC impedance detection is provided, characterized in that it comprises: a frequency sweeper for adjusting the frequency of a modulation signal within a test frequency range when a battery detection mode is activated; a capacitor; a synchronous buck converter for modulating the capacitor with the pulse modulation signal to generate an AC excitation current injected into a battery pack; a current sensor for sensing the AC current value of the AC excitation current injected into the battery pack; wherein the synchronous buck converter modulates the AC excitation current within the test frequency range; and a sampler for measuring the AC test voltage of a node in the battery pack, the AC test voltage being adjusted according to the response of the battery pack to the AC excitation current. The device includes: a variable; an external connector for connecting to an external charger or external load; a power switch located between the battery pack and the external connector, the power switch being controlled by a switching signal to connect the battery pack to the external connector; and a controller that activates the switching signal in a charging / discharging mode and deactivates the switching signal in an idle mode; wherein the controller activates the sweep frequency generator during the battery detection mode, which can be enabled during both the charging / discharging and idle modes; and wherein the AC current value and the AC test voltage are signal-processed to form an impedance value indicating the health status of the battery pack. Attached Figure Description

[0012] Figure 1 This is a block diagram of a battery management detector with onboard AC impedance battery detection.

[0013] Figure 2 This is a diagram of the AC excitation signal applied to the battery pack.

[0014] Figure 3 yes Figure 1 Waveform of the battery management detector during operation.

[0015] Figures 4A-4F This illustrates the battery detection process where the BMS uses an AC excitation signal to detect the battery's AC impedance.

[0016] Figure 5 A battery-managed AC impedance detector with a finite energy cell, driven by a synchronous buck converter and a capacitor, is shown.

[0017] Figure 6 This highlights the data processing procedures for the AC excitation signal and the battery pack response signal.

[0018] Figure 7 The Nyquist plot is generated by using an onboard excitation regulator with finite energy units to detect the AC impedance of the battery.

[0019] Figure 8 The Nyquist plot is generated by using an onboard excitation regulator with finite energy units to detect the AC impedance of individual battery cells.

[0020] Figure 9 The Nyquist plot is generated by using an onboard excitation regulator with finite energy units to perform AC impedance sensing on the battery pack.

[0021] Figure 10 This illustrates a synchronous buck converter that generates an excitation signal from the energy stored in a capacitor. Detailed Implementation

[0022] This invention relates to improvements in the AC impedance detection of batteries. The following description is presented to enable those skilled in the art to make and use the invention in the context of a particular application and its requirements. Various modifications to the preferred embodiments will be apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments. Therefore, the invention is not intended to be limited to the specific embodiments shown and described, but is to be given the broadest scope consistent with the principles and novel features disclosed herein.

[0023] Figure 1 This is a block diagram of a battery management detector with onboard AC impedance battery detection. The battery pack 40 has a plurality of battery modules or units connected in series between battery terminals B+ (e.g., a first terminal of the battery pack 40) and B- (e.g., a second terminal of the battery pack 40), wherein a battery voltage VB exists between battery terminals B+ and B-. The battery management system (BMS) includes a battery management detector 100. The battery management detector 100 includes a first battery connection for connection to the first terminal of the battery pack; a second battery connection for connection to the second terminal of the battery pack; a first external connector for connection to the first terminal of an external charger and the first terminal of an external load; a second external connector for connection to the second terminal of the external charger and the second terminal of the external load; a power switch connected between the second external connector and the second battery connection; a controller (MCU) 10; a finite energy unit 60; an onboard excitation regulator 50; and a synchronous sampler 22. The finite energy unit may be a capacitor. The capacitor is connected between the first output node of the onboard excitation regulator 50 and the second battery connection. The onboard excitation regulator 50 may be a synchronous buck converter.

[0024] When an external charger is attached to external terminals "+" (e.g., the first external connector) or "-" (e.g., the second external connector), battery pack 40 is charged by battery current IB. When power switch 30 is closed by switch signal SW, battery current IB flows from the + charger terminal through fuse 44 and into battery terminal B+, causing return current to flow from battery terminal B- through power switch 30 to the - external terminal connected to the external charger. The charging mode is when MCU 10 sets switch signal SW to "on" (active state) and the charger is connected to external terminals + and -.

[0025] During discharge mode, for example, when the load of the EV engine is connected to external terminals + and -, MCU 10 sets the switch signal SW to ON to turn on power switch 30. Battery pack 40 provides current to the load, which flows from battery terminal B+ through fuse 44 to external terminal +, then to the load, and from the load through external terminal - and through power switch 30 to battery terminal B-.

[0026] During idle mode, MCU 10 sets the switch signal SW to off (inactive state), thereby disconnecting the power switch 30 and preventing current from flowing from the battery pack 40 to the external terminals.

[0027] The battery management detector 100 further includes a BMS monitor 20. The BMS monitor (also known as a battery monitor) 20 can monitor the battery pack 40, for example, by receiving voltage, current and temperature signals of the battery pack 40.

[0028] The battery management detector 100 further includes an equalization circuit 24. The equalization circuit 24 controls the battery pack 40 and equalizes the voltage of the battery modules or cells within the battery pack 40 using passive or active equalization circuitry. In some systems, the equalization circuit 24 can disconnect or bypass the battery modules or cells in the battery pack 40. Therefore, damaged or aged battery modules or cells can be disconnected in some systems.

[0029] Synchronous sampler 22 samples the overall battery voltage VB and battery current IB, and can also sample internal nodes within the battery pack 40, such as receiving the voltage of internal nodes within the battery pack 40. Compared to the BMS monitor 20, synchronous sampler 22 provides synchronous sampling with higher sampling accuracy and can detect internal voltages within the battery pack 40, such as the voltage of battery modules connected in series between battery pack terminals B+ and B-.

[0030] MCU 10 executes various control routines to control BMS monitor 20, synchronous sampler 22, and equalization circuit 24, monitoring signals generated by battery pack 40. MCU 10 also executes a battery detection routine that generates an AC excitation signal applied to battery pack 40 to perform AC impedance detection.

[0031] During or before AC impedance detection, MCU 10 instructs onboard excitation regulator 50 to draw a small amount of energy from battery pack 40 through battery terminals B+, B- to charge finite energy cell 60. This small amount of energy stored in finite energy cell 60 then powers onboard excitation regulator 50 to generate an AC excitation signal. The frequency of this AC excitation signal is controlled by a pulse modulation signal (PWM_OUT) received by onboard excitation regulator 50 from MCU 10, having the frequency of a modulation signal (PWM_IN). During battery detection, MCU 10 generates the modulation signal PWM_IN and varies its frequency within a set of frequencies. Onboard excitation regulator 50 is connected between the first battery connection and the second battery connection, driving the AC excitation signal generated by finite energy cell 60 to the first battery connection. The AC excitation signal is a current injected into the first battery connection.

[0032] The AC excitation signal generated by the onboard excitation regulator 50 is the sensed current I_SEN, controlled by the pulse modulation signal PWM_OUT. The AC excitation signal I_SEN flows to the battery terminal B+ and is superimposed on the charging or discharging current. During idle mode, the AC excitation signal I_SEN is the only current, therefore I_SEN = IB.

[0033] MCU 10 monitors the applied AC excitation current I_SEN and the voltage V_SEN from the finite energy unit 60, and compares this AC excitation signal I_SEN with the response of battery pack 40, such as VB from synchronous sampler 22 or changes in internal voltage. Small AC excitation signals I_SEN superimposed on the DC charging or discharging current cause small and rapid voltage changes, which synchronous sampler 22 can detect.

[0034] The onboard excitation regulator 50 injects the AC excitation signal into the first battery connection during battery detection, wherein the AC excitation signal modulated in the battery pack 40 causes a modulation response (voltage response) of the response signal in the battery pack 40. A synchronous sampler 22 samples and detects the modulation response of the response signal in the battery pack 40. The response signal is the voltage of the battery pack 40. Based on the applied AC excitation signal I_SEN and the voltage response of the battery pack 40, the MCU 10 can plot an impedance diagram of the battery pack 40. This impedance diagram can be used to detect battery problems, such as loose or disconnected internal connectors, or inconsistent battery cells within the battery pack. The impedance diagram can estimate the health condition or aging of the battery modules or cells within the battery pack 40. The battery management detector 100 may further include an AC impedance processor that processes the modulation response of the battery pack 40 and the modulated AC excitation signal to generate an impedance diagram. The impedance diagram is a graph of the imaginary part of impedance relative to the real part of impedance; the impedance diagram is a Nyquist plot. When the AC impedance processor detects a curve shift in the impedance graph, the battery management detector 100 (MCU 10) sends a battery aging signal. The impedance graph is a table of impedance values ​​stored in computer memory.

[0035] Figure 2 This is a diagram of the AC excitation signal applied to the battery pack, showing the effect of the onboard excitation regulator 50. Figure 1 The amplitude-time diagram of the generated AC excitation signal I_SEN is shown. MCU 10 has a PWM modulator. MCU 10 sets the PWM signal to on and drives the modulation signal PWM_IN to the PWM modulator, which generates a pulse modulation signal PWM_OUT with a fixed frequency much higher than the modulation signal PWM_IN, and causes the onboard excitation regulator 50 to generate an AC excitation signal I_SEN with an initial frequency of F0 synchronized with the modulation signal PWM_IN.

[0036] MCU 10 gradually decreases the frequency of the modulation signal PWM_IN, causing the frequency of the AC excitation signal I_SEN to decrease from F0 to the next frequency F1, then to F2, F3, and finally the lowest frequency F4. In a practical system, there can be more than four frequency points, such as 20, 40, 50, etc. The battery pack 40 has different responses to different frequencies F0, F1, F2, ... F4. The voltage VB and current IB of the battery pack are sensed and sampled by the synchronous sampler 22, and the battery impedance at different frequency points can be calculated by MCU 10 according to Ohm's law.

[0037] Figure 3 yes Figure 1Waveform diagram of the battery management detector during operation. In Mode 1, i.e., idle mode, the battery is neither connected to the charger nor to the load, and no AC impedance test is performed. The battery voltage VB remains constant when the switch signal SW is off to disconnect the charger and load. The PWM signal is off, the PWM modulator does not generate the pulse modulation signal PWM_OUT, therefore no AC excitation signal I_SEN is generated. No battery current IB flows.

[0038] In Mode 2, i.e., the charging / discharging mode, the switch signal SW is turned on, connecting battery pack 40 to an external charger or load. Battery current IB flows. Because AC impedance testing is not performed in Mode 2, the PWM modulator does not output pulses, and no AC excitation signal I_SEN is generated. During charging, the battery voltage VB rises, and during discharging, the battery voltage VB falls.

[0039] In Mode 3, i.e., Idle + Detection Mode, the frequency of the control modulation signal PWM_IN decreases over time, and the onboard excitation regulator 50 generates an AC excitation signal I_SEN, the frequency of which also decreases over time. The period of the pulse modulation signal PWM_OUT is much smaller than the period of the AC excitation signal I_SEN, and therefore is not plotted to scale. The switch signal SW is off, thus disconnecting the battery from the load and charger. The only battery current IB comes from the AC excitation signal I_SEN. Due to the presence of the AC excitation signal, the battery voltage VB fluctuates slightly in response, and the MCU 10 detects these VB fluctuations to estimate the health of the battery pack 40 and its internal components.

[0040] In Mode 4, i.e., the charging + detection mode, MCU 10 enables the PWM modulator, controlling the frequency of the modulation signal PWM_IN to decrease over time. The onboard excitation regulator 50 generates an AC excitation signal I_SEN, the frequency of which also decreases over time. The period of the pulse modulation signal PWM_OUT is much smaller than the period of the AC excitation signal I_SEN, and therefore is not plotted to scale. The switch signal SW is turned on, thus connecting the battery to the charger (or, in a similar discharging + detection mode, to the load).

[0041] The battery current IB is the sum of the charging current flowing into the battery and the AC excitation signal I_SEN. The charging current is the DC current that shifts the AC excitation signal I_SEN upward, as shown in the waveform of IB.

[0042] The battery voltage VB shifts upwards during charging and is then slightly modulated by the AC excitation signal I_SEN. MCU 10 detects these VB fluctuations and internal battery nodes to estimate the health of battery pack 40 and its internal components. Battery management detector 100 further includes a BMS monitor 20 for receiving monitoring signals from battery pack 40. When the monitoring signal indicates a problem with the battery pack, MCU 10 responds by executing an alarm routine that causes MCU 10 to turn off the switch signal SW and stop modulating the modulation signal PWM_IN.

[0043] Figures 4A-4F This illustrates the battery detection process where the BMS uses an AC excitation signal to detect the battery's AC impedance. Figure 4A During operation, the BMS reads battery information (step 202). This battery information can be stored in the battery pack 40 or in a memory device on the BMS, where the battery management detector 100 is read by the MCU 10. This battery information may include the battery cell structure or arrangement within the battery pack 40, voltage or current limits, initial AC impedance, charge / discharge cycles, and current information such as voltage, current, temperature, high / low temperature alarms, overvoltage / undervoltage alarms, overcurrent alarms, short circuits, or various other faults. The read battery information may include individual fault alarms or general fault indications generated by the battery pack 40.

[0044] When the battery pack 40 detects or reports a fault (step 208), the alarm subroutine 220 is activated to handle the alarm, which may involve setting the switch signal SW and the PWM signal to the off state.

[0045] When the fault ends or no fault is detected (step 208), the BMS waits for a mode change command or request from the user or a higher-level system (step 210). At this time, it is in idle mode, and the switch signal SW and PWM signal are off. The mode change request is parsed to determine which mode is requested. When the request is for charging or discharging mode (step 210), the charging / discharging mode routine 240 is activated. Figure 4B When the request is for a charging or discharging mode with online detection (step 210), the charging / discharging + online detection mode routine 280 is activated. Figure 4D-4F When the request is for an idle mode with online detection (step 210), the idle + online detection mode routine 260 is activated. Figure 4C ).

[0046] exist Figure 4BIn step 243, the charging / discharging mode routine 240 is activated. The current limit value ILIM for battery pack 40 is set. MCU 10 sets the switch signal SW to ON to turn on power switch 30, enabling battery pack 40 to be charged by an external charger or to drive an external load. MCU 10 sets the PWM signal to OFF (step 246), and does not output the pulse modulation signal PWM_OUT. The battery current IB is read (step 242), for example, using synchronous sampler 22.

[0047] When the battery current IB exceeds the current limit ILIM (step 244), the alarm subroutine 220 is activated. Figure 4A To prevent high battery current IB from damaging the battery pack 40, the BMS waits for charging and discharging to complete when the battery current IB does not exceed the current limit (step 244). After charging and discharging are complete (step 248), the charging / discharging mode ends, and the setting switch signal SW is turned off (step 252). The process loops back to... Figure 4A Step 210 in the process.

[0048] exist Figure 4C In step 262, the idle + online detection mode routine 260 is activated. The sweep parameters of the modulation signal PWM_IN are initialized. These parameters may include the starting maximum frequency, the ending minimum frequency, and the frequency step size. MCU 10 keeps the switch signal SW off to idle the battery pack 40, but turns on the PWM signal (step 266). MCU 10 drives the modulation signal PWM_IN at the starting maximum frequency, causing the onboard excitation regulator 50 to drive AC power with the highest frequency of the modulation signal PWM_IN to the limited energy unit 60. This sweep excitation (step 270) continues at the highest frequency for a period of time, for example, 3 cycles. At the end of the time period, the frequency is detected, and if the frequency is not the ending minimum frequency (step 268), the frequency of the modulation signal PWM_IN is decreased by one frequency step (step 274).

[0049] Then, MCU 10 drives the modulation signal PWM_IN at a new, lower frequency, and onboard excitation regulator 50 drives the finite energy unit 60, which in turn excites battery pack 40 at a lower frequency. Battery voltage VB, battery current IB, and internal node voltages can be read via synchronous sampler 22.

[0050] The frequency sweep excitation (step 270) continues at the lower frequency for the specified time period until the frequency is detected again (step 268) and drops again (step 274) to sweep an even lower frequency. After several cycles, the frequency of the modulation signal PWM_IN sweeps down to the lowest ending frequency. Then, after the frequency sweep excitation at this lowest frequency (step 270), the minimum frequency is detected (step 268), and the frequency sweep cycle exits. MCU 10 sets the PWM signal to off (step 272), and the idle + online detection mode routine 260 ends.

[0051] exist Figure 4D In the process, the charging / discharging + online detection mode routine 280 is activated. The current limit value ILIM of battery pack 40 is set (step 283). The parameters for sweeping the modulation signal PWM_IN are initialized (step 282). MCU 10 sets the switch signal SW to the ON state to turn on the power switch 30, enabling battery pack 40 to be charged by an external charger or to drive an external load. MCU 10 sets the PWM signal to the ON state and begins pulse delivery of the pulse modulation signal PWM_OUT (step 286). The battery current IB is read (step 288). When the battery current IB exceeds the current limit value ILIM (step 284), the alarm subroutine 220 is activated. Figure 4A To prevent high battery current IB from damaging the battery pack 40.

[0052] When the battery current IB does not exceed the current limit (step 284), the charging / discharging + online detection mode routine 280 is in... Figure 4E Continued.

[0053] MCU 10 drives the modulation signal PWM_IN at the highest starting frequency, causing the onboard excitation regulator 50 to drive AC power to the limited energy unit 60 at the highest frequency of the modulation signal PWM_IN. The frequency sweep excitation (step 270) lasts for one time period. After this time period, when charging and discharging are complete but the minimum ending frequency has not yet been reached (step 310), MCU 10 sets the switch signal SW to the off state, and power switch 30 disconnects the battery pack 40 from the external charger or load (step 314). Then, the frequency of the modulation signal PWM_IN decreases by one frequency step (step 278), returning to the frequency sweep excitation at a lower frequency (step 270).

[0054] When charging or discharging is not complete and the minimum ending frequency has not been reached (step 312), the frequency of the modulation signal PWM_IN is reduced by one frequency step (step 276), and the battery current IB is read (step 288). Figure 4D This is compared with ILIM (step 284), so that when the battery current IB exceeds the current limit ILIM, the alarm subroutine 220 can be invoked. Figure 4A In other cases, the frequency sweep excitation (step 270) is performed at a lower frequency, and the above process is repeated as the frequency of the modulation signal PWM_IN decreases repeatedly.

[0055] When the frequency of the modulation signal PWM_IN reaches the minimum ending frequency ( Figure 4E Step 312) but charging or discharging is not yet complete. Figure 4F In step 320), MCU 10 turns off the PWM signal to stop outputting the pulse modulation signal PWM_OUT (step 324), and BMS continues charging / discharging mode routine 240.

[0056] When the frequency of the modulation signal PWM_IN reaches the minimum end frequency (step 312) and charging or discharging is completed (step 320), the MCU 10 turns off the PWM signal to stop outputting the pulse modulation signal PWM_OUT, and turns off the switch signal SW (step 322) to make the BMS idle.

[0057] Figure 5 A battery management AC impedance detector (BMS) driven by a synchronous buck converter and using a capacitor as the finite energy unit is shown. When detecting the battery pack 40, the MCU 10 generates a modulation signal PWM_IN and outputs a pulse modulation signal PWM_OUT. The MCU 10 modulates the modulation signal PWM_IN by sweeping the frequency within a frequency range. The BMS with the AC impedance detector 110 has a synchronous buck converter 52 that receives the pulse modulation signal PWM_OUT from the MCU 10 and excites the capacitor 62 at the frequency of the modulation signal PWM_IN. During AC impedance detection, the voltage V_SEN of the capacitor 62 is stepped down by the synchronous buck converter 52, driving the AC excitation signal I_SEN to the battery terminal B+ to excite the battery pack 40. The AC excitation signal I_SEN is an AC signal generated by driving the capacitor 62 and has the frequency of the modulation signal PWM_IN.

[0058] MCU 10 monitors V_SEN and the AC excitation signal I_SEN, which is the stimulus applied to battery pack 40 during AC impedance sensing. MCU 10 also uses BMS monitor 20 and synchronous sampler 22 to monitor the battery pack 40's response to this stimulus. For example, the response of battery pack 40 can be determined by small AC variations in the overall battery voltage VB or the voltage at internal nodes within battery pack 40. The battery current IB and voltage VB, or the voltage at internal nodes within battery pack 40, are monitored by synchronous sampler 22.

[0059] The power switch 30 is composed of gallium nitride (GaN) transistors 32 and 34 controlled by the switching signal SW. GaN transistors can handle very large currents and have a fast switching speed.

[0060] During charging mode, capacitor 62 is also charged while the external charger charges battery pack 40. Capacitor 62 stores sufficient charge to generate an AC excitation signal within a swept frequency range via synchronous buck converter 52. Capacitor 62 is a 1mF / 100V capacitor.

[0061] Capacitor 62 can be pre-charged by battery pack 40. When the PWM signal is enabled and MCU 10 drives the DC signal to the modulation signal PWM_IN, capacitor 62 is pre-charged to DC voltage via synchronous buck converter 52. Then, capacitor 62 operates with a small AC voltage / current ripple, generating an AC excitation signal I_SEN via synchronous buck converter 52. Synchronous buck converter 52 generates the AC excitation signal I_SEN and injects it into battery pack 40 without drawing energy from battery pack 40.

[0062] Figure 6 The data processing procedures for the AC excitation signal and the battery pack response signal are highlighted. An AC excitation signal (e.g., current I_SEN) is applied to the battery pack 40, causing a time-varying response (e.g., battery voltage VB) in the battery pack 40. The response signal is the voltage of the battery pack. In one embodiment, the response signal is the voltage of an internal node within the battery pack, located between the first battery connection and the second battery connection and having a voltage different from that of the first and second battery connections.

[0063] The capacitive nature of battery pack 40 introduces a 90-degree phase shift in the response voltage relative to the AC excitation signal current. This phase shift can be described using an imaginary number as the imaginary part of the impedance Z.

[0064] The AC impedance processor includes discrete samplers 621 and 622; Fourier transforms 641 and 642; an impedance calculator 300; and a plotter 660. Both the excitation and response waveforms are processed by the discrete samplers 621 and 622 to generate data values, which are then processed by the Fourier transforms 641 and 642 to generate frequency sequences in the frequency domain. The excitation frequency sequence is derived from the current values, while the response frequency sequence is derived from the voltage values.

[0065] The impedance calculator 300 uses Ohm's law to calculate the impedance Z = V / I at each frequency. The real and imaginary parts of the impedance are plotted as a Nyquist plot by the plotter 660. The impedance calculator 300 can be run by a digital signal processor (DSP) or other processor.

[0066] Synchronous sampler 22 synchronously samples the excitation current I_SEN and voltage response VB at each sampling moment. After Fourier transform, the amplitude and phase data of the excitation and response at different frequencies can be found. Then, the amplitude and phase angle of the voltage response VB and the excitation current I_SEN can be used to calculate the complex impedance Z, expressed in real and imaginary parts.

[0067] Figure 7 This is a Nyquist plot generated by AC impedance sensing of the battery using an onboard excitation regulator with finite energy units. The imaginary and real parts of each impedance value are plotted, forming curve 502. Each data point corresponds to a frequency. Higher frequency data points are on the left, and lower frequencies are on the right.

[0068] At higher frequencies, impedance reflects the ohmic resistance of the battery electrolyte. At mid-frequency frequencies, impedance is affected by SEI capacitance and electron transfer rate. At lower frequencies, impedance reflects the diffusion process of conductive ions in the electrode material.

[0069] The shape of curve 502 varies with the electrochemical response of the battery's electrochemical cells and the differences in the battery's internal resistance and capacitance. As the battery ages and wears, the shape of 502 will change.

[0070] Figure 8 This is a Nyquist plot generated by AC impedance sensing of individual battery cells using an onboard excitation regulator with finite energy units. The imaginary and real parts of each impedance value are plotted. Curve 504 represents a new battery cell, while curve 506 represents an older battery cell. Compared to curve 504 for a new battery, curve 506 for an older battery is shifted to the right. The aging or wear condition of the detected battery can be estimated by the shift of its curve relative to the new battery curve. While aging estimates may not be precise, even a rough estimate of battery aging can be useful.

[0071] Figure 9 The Nyquist plot is generated by AC impedance sensing of the battery pack using an onboard excitation regulator with finite energy units. The imaginary and real parts of each impedance value are plotted. The synchronous sampler 22 can sample the voltages of several internal nodes between battery modules connected in series within the battery pack 40. The voltage from each internal node can be sampled and processed individually to form one of the curves 601-608.

[0072] Curves 601-608 correspond to different battery modules in the battery pack. Specifically, compared to curves 601, 602, 603, 605, 606, 607, and 608, curve 604 shifts to the right more significantly. This rightward shift of curve 604 indicates that the battery module forming curve 604 is more severely aged than the other battery modules. The BMS can instruct battery pack 40 to disconnect the battery module corresponding to curve 604. The lifespan of battery pack 40 can be increased by disconnecting the aged battery modules within battery pack 40.

[0073] Figure 10 This diagram illustrates a synchronous buck converter that generates an excitation signal from the energy stored in a capacitor. When the PWM signal is enabled, capacitor 62 is first pre-charged. The capacitor 62 is pre-charged using a limited current drawn from battery pack 40 by the synchronous buck converter. The voltage of capacitor 62 is sampled and fed back to MCU 10 as V_SEN. Pre-charging stops after V_SEN reaches a preset value controlled by MCU 10. Subsequently, capacitor 62 supplies energy for the synchronous buck converter 52 to generate the excitation current I_SEN.

[0074] Capacitor 62 is directly driven by synchronous buck converter 52. When the PWM signal is enabled, MCU 10 enables PWM modulator 810, where the modulation signal PWM_IN controls the duty cycle of the pulse modulation signal PWM_OUT generated by PWM modulator 810.

[0075] The synchronous buck converter 52 has a switch 802 that is closed by an inverter 806 to conduct current when the pulse modulation signal PWM_OUT is low, and closed by a switch 804 to conduct current when the pulse modulation signal PWM_OUT is high. A filter 808, such as an inductor, can be a current filter that carries an excitation current I_SEN between the battery terminal B+ of the battery pack 40 and switches 802 and 804. The negative battery terminal B_ is connected to switch 804 and capacitor 62, and switch 802 drives the upper terminal of capacitor 62 to generate a voltage V_SEN.

[0076] When switch 802 is closed and switch 804 is open, capacitor 62 supplies the excitation current I_SEN to the battery terminal B+ of battery pack 40 through switch 802 and current filter 808. When switch 802 is open and switch 804 is closed, capacitor 62 is disconnected from synchronous buck converter 52. The excitation current I_SEN continues to be supplied to battery terminal B+ through switch 804 and current filter 808. Switches 802 and 804 are one-way switches.

[0077] The following describes alternative embodiments. For example, other circuitry that can be used with the onboard excitation regulator 50 may include a synchronous buck converter 52, a buck-boost converter, a half-bridge, a full-bridge, a multilevel flyback converter, a bidirectional DC-DC / DC-AC converter, or any circuitry capable of generating a variable frequency excitation signal. The onboard excitation regulator 50 may be connected between terminals B+ and B- of the battery pack 40 to draw power directly from the battery pack 40, or a power controller mounted on a printed circuit board (PCB) of a BMS with a battery management detector 100 may draw power from terminals B+ and B- of the battery pack 40 and then provide local power from the battery pack 40 or from an external charger during charging mode to the onboard excitation regulator 50, the MCU 10, and other components.

[0078] MCU 10 draws power from terminals B+ and B-. This power is obtained from battery pack 40 when performing AC detection without connecting an external charger, or from an external charger during charging mode. MCU 10 continuously consumes power. The onboard excitation regulator 50 does not consume battery power because it transfers AC current between battery pack 40 and capacitor 62 after pre-charging. Capacitor 62 is used to store the limited energy drawn from battery pack 40 during pre-charging. The energy stored in capacitor 62 is almost entirely lost.

[0079] Capacitor 62 may be a device such as a supercapacitor or a standard capacitor. Synchronous sampler 22 may have one or more analog-to-digital converters (ADCs) to accurately measure the voltage or current in battery pack 40.

[0080] A calibration table can be constructed through aging cycle testing of new batteries, with repeated AC impedance measurements performed during battery aging to plot battery curves on a Nyquist plot or similar datasheet. The state of health (SOH) of the battery can be estimated from the curves obtained from this aging of the battery. Battery pack 40 can be represented using various models, such as parallel and series networks of capacitors and resistors. Various electrochemical impedance spectroscopy (EIS) models can be used to interpret curve shifts on the Nyquist plots obtained by BMS. A Bode plot can also be used.

[0081] Although the plotting of the imaginary and real parts of the impedance values ​​has been described, this plotting can be done by tabulating the impedance data in computer memory, without needing to create a human-readable graph. The graph can be various data tables in different formats and arrangements in computer memory. The BMS can detect curve shifts by the impedance values ​​at the intersection points of the curve and the straight line, rather than detecting the entire curve. Different intersection values ​​can be used to detect curve shifts.

[0082] The time interval between different frequencies should be long enough for the components inside the battery pack 40 to reach a stable state, thus resonating with the applied AC excitation signal. The duration can be several dozen cycles of the AC excitation signal I_SEN, which can be set by the MCU 10.

[0083] Although the modulation signal PWM_IN has been described, this modulation signal PWM_IN can have various wave shapes and forms, such as square, rectangular, triangular, sine and other shapes, and can have various duty cycles and phases.

[0084] Although the current I_SEN is described as an AC excitation signal and the voltage as a response, the AC excitation signal can be a modulated voltage applied to B+, and the response can be the current flowing through the battery pack 40. The response can be a voltage obtained from an internal node within the battery pack 40 or from the battery terminal B+, or it can be an internal current sensed through the battery pack 40, and can also be various combinations thereof. A BMS with a battery management detector 100 can detect the responses of several nodes and then combine these responses or analyze each response individually. For example, the battery pack 40 consists of several battery modules connected in series, and the battery pack 40 can detect the node voltages between the internal battery modules, and these internal voltages are sensed by a synchronous sampler 22. The voltage of each internal node can be determined according to… Figure 6 The data is processed as shown and plotted as separate curves on the Nyquist plot. Curves 601-608 represent the different battery modules within battery pack 40. Minor offsets between curves may be due to differences in series resistance to B- between the series-connected battery modules.

[0085] The synchronous sampler 22, BMS monitor 20, MCU 10, equalization circuit 24, onboard excitation regulator 50, and finite energy unit 60 can be implemented in various ways. The MCU 10 can execute instructions to complete... Figures 4A-4F The process can be performed in a manner that includes both hardware and software components. Some steps can utilize a hardware engine, and instructions can be a combination of firmware, software, and hardware logic. A digital signal processor (DSP) or other processor can be invoked by the MCU 10 to perform more complex processing, such as... Figure 6 The Fourier transform is shown. The MCU 10 can also be integrated with a DSP.

[0086] For the same excitation current I_SEN, the individual battery cells within battery pack 40 may behave differently and exhibit different voltage responses. Synchronous sampler 22 can measure the internal node voltages of battery pack 40. The entire battery pack, composed of battery cells connected in series, has the same frequency of response. Battery pack 40 may contain several battery modules connected in series, and each battery module may contain several battery cells connected in series, parallel, or in various combinations. Other structures are also possible.

[0087] One embodiment of the power switch 30 has been shown, using a pair of gallium nitride (GaN) transistors. Many other switching embodiments and techniques can be used instead. The position of the power switch 30 can be repositioned to connect to the positive terminal of an external charger / load instead of the negative terminal.

[0088] Unlike battery pack 40, which has only one power switch 30 on its B-terminal power return line, different independent power switches can be used: one between the B-node and the external charger's B-node, and another between the B-node and the external load's B-node. The MCU 10 can then select the charger switch for charging mode and the load switch for discharging mode. Although charging / discharging... Figures 4A-4F During the process, it is shown as a combined node, but this process can have separate charging and discharging modes, and can have or not have online detection. There are a total of 4 modes, not... Figures 4A-4F The two modes shown.

[0089] For various reasons, other components can be added at various nodes, such as resistors, inductors, capacitors, fuses, filters, switches, transistors, etc. A PCB implementing a BMS with a battery management detector 100 typically includes other components, such as filter capacitors, buffers, power controllers or regulators, clock generators, etc. For example, an AC drive current sensor is used to sense the current value of the AC drive signal injected into the first battery connection (the MCU 10 uses the AC drive current sensor to sample the AC drive signal); a battery current sensor is used to sense the battery current flowing from the first battery connection to the second battery connection (the MCU 10 compares the battery current sensed by the battery current sensor with a current limit value and activates the alarm routine when the battery current exceeds the current limit value); a first current sensor located between the synchronous buck converter and the first terminal senses the AC current value of the AC drive current injected into the battery pack.

[0090] Although a downward frequency sweep has been described, it can be replaced by an upward frequency sweep. The frequency step size can be changed. The frequency can be changed from the list of discrete frequencies to perform the sweep.

[0091] The background section may contain background information about the problems or circumstances surrounding the invention, rather than a description of prior art by others. Therefore, the inclusion of material in the background section does not constitute an admission of prior art by the applicant.

[0092] Any methods or processes described herein are implemented by machines or computers and are intended to be performed by machines, computers, or other devices, and are not intended to be performed by humans alone without such machine assistance. Tangible results may include reports on display devices or other machine-generated displays, such as computer monitors, projection devices, audio generating devices, and associated media devices, and may include hard-copy printouts, also machine-generated. Computer control of other machines is another tangible result.

[0093] The foregoing description of embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible based on the foregoing description. It is intended that the scope of the invention be limited not by this detailed description, but by the appended claims.

Claims

1. A battery management detector, characterized by, comprising: a first battery connection for connecting to a first terminal of a battery pack; a second battery connection for connecting to a second terminal of the battery pack; a first external connector for connecting to a first terminal of an external charger and a first terminal of an external load; a second external connector for connecting to a second terminal of the external charger and a second terminal of the external load; a power switch connected between the second external connector and the second battery connection, the power switch controlled by a switch signal in an inactive state to disconnect the second external connector from the second battery connection; a controller to place the switch signal in an active state when a charge / discharge mode is activated, causing the power switch to connect the second external connector to the second battery connection, and to place the switch signal in the inactive state when an idle mode is activated; a modulating signal (PWM_IN) generated by the controller during battery detection, outputting a pulse modulating signal (PWM_OUT), wherein the controller varies a frequency of the modulating signal within a set of frequencies; a limited energy unit storing a limited amount of energy insufficient to power the battery management detector, wherein the limited amount of energy is sufficient to generate an alternating excitation signal; an on-board excitation regulator receiving the pulse modulating signal from the controller and driving the limited energy unit with the pulse modulating signal, modulating the limited energy unit to generate the alternating excitation signal; wherein the modulation of the alternating excitation signal has a frequency of the modulating signal; the on-board excitation regulator injecting the alternating excitation signal into the first battery connection during battery detection; wherein the modulated alternating excitation signal injected into the battery pack causes the battery pack to generate a modulated response of a response signal; and a synchronous sampler sampling the response signal in the battery pack and detecting the modulated response, wherein the alternating excitation signal is generated by the limited energy unit, the limited energy unit is a capacitor, the capacitor connected between a first output node of the on-board excitation regulator and the second battery connection.

2. The battery management detector of claim 1, wherein, a second output node of the on-board excitation regulator is directly connected to the first battery connection; wherein the modulation of the capacitor forms the alternating excitation signal.

3. The battery management detector of claim 1, wherein, the on-board excitation regulator is a synchronous buck converter.

4. The battery management detector of claim 3, wherein, the controller modulates the modulating signal when battery detection is requested during the charge / discharge mode; wherein the controller modulates the modulating signal when battery detection is requested during the idle mode; wherein the online battery detection is executable during charging of the battery pack, during discharging of the battery pack, and when the battery pack is idle.

5. The battery management detector of claim 3, wherein, further comprising: an alternating impedance processor detecting the modulated response from the battery pack and the modulated alternating excitation signal to generate an impedance plot; wherein the impedance plot is a plot of impedance imaginary part versus impedance real part, the impedance plot is a Nyquist plot.

6. The battery management detector of claim 5, wherein, sending a signal of battery aging when the alternating impedance processor detects a curve shift in the impedance plot.

7. The battery management detector of claim 5, wherein, the alternating impedance processor further comprising: a first discrete sampler for sampling the AC excitation signal to produce a sampled AC excitation signal; a first transformer for performing a Fourier transform on the sampled AC excitation signal to produce an excitation sequence in the frequency domain; a second discrete sampler for sampling the response signal to produce a sampled response signal; a second transformer for performing a Fourier transform on the sampled response signal to produce a response sequence in the frequency domain; an impedance calculator for dividing the response sequence by the excitation sequence for each frequency in the frequency sequence to produce real and imaginary parts of an impedance value; a plotter for plotting the real and imaginary parts of the impedance value onto the impedance plot; wherein the impedance plot is a table of impedance values stored in computer memory.

8. The battery management detector of claim 5, wherein, the on-board excitation regulator is connected between the first battery connection and the second battery connection; wherein the on-board excitation regulator drives the AC excitation signal produced by the limited energy unit onto the first battery connection.

9. The battery management detector of claim 5, wherein, the AC excitation signal is a current injected into the first battery connection; wherein the response signal is a voltage of the battery pack.

10. The battery management detector of claim 9, wherein, the response signal is a voltage of an internal node within the battery pack, the internal node being between the first battery connection and the second battery connection and having a voltage different from the first battery connection and the second battery connection.

11. The battery management detector of claim 4, wherein, further comprising: a fuse connected between the first external connector and the first battery connection.

12. The battery management detector of claim 4, wherein, further comprising: a battery monitor for receiving a monitor signal of the battery pack; wherein the controller executes an alarm routine in response to the monitor signal indicating that the battery pack is problematic, the alarm routine causing the controller to place the switch signal in the inactive state and causing the controller to stop modulating the modulation signal.

13. The battery management detector of claim 12, wherein, further comprising: an AC excitation current sensor for sensing a current value of the AC excitation signal injected into the first battery connection; wherein the controller samples the AC excitation signal using the AC excitation current sensor.

14. The battery management detector of claim 13, wherein, further comprising: a battery current sensor for sensing a battery current flowing from the first battery connection to the second battery connection; wherein the controller compares the battery current sensed by the battery current sensor to a current limit value and activates the alarm routine when the battery current exceeds the current limit value.

15. A battery management AC impedance detector, comprising: comprising: a first terminal for connecting to a first terminal of a battery pack; a second terminal for connecting to a second terminal of the battery pack; a power switch for connecting the second terminal to a second external terminal when a switch signal is activated and isolating the second terminal from the second external terminal when the switch signal is not activated; wherein an external charger is able to connect to the second external terminal and the first terminal to charge the battery pack; wherein an external load is able to connect to the second external terminal and the first terminal to be powered by the battery pack; a sampler for sampling a battery test voltage of the battery pack; a controller to set the switch signal to an active state during a charge / discharge mode and to set the switch signal to an inactive state during an idle mode, wherein in the idle mode the battery pack is not charging and is not driving the external load; the controller to generate a modulating signal (PWM_IN) when the battery pack is detected, to output a pulse modulating signal (PWM_OUT), and to sweep the modulating signal over a frequency range; a capacitor; a synchronous buck converter to be inputted with the pulse modulating signal, to drive the capacitor to generate an alternating excitation signal having the frequency range of the modulating signal, and the capacitor to be connected between the synchronous buck converter and the second terminal; and a first current sensor between the synchronous buck converter and the first terminal; wherein the synchronous buck converter drives the alternating excitation signal as a first modulated current to flow through the first current sensor; wherein the first modulated current is modulated over the frequency range of the modulating signal; wherein the response of the battery pack to the first modulated current is to modulate the battery test voltage; wherein the sampler detects the modulated response of the battery test voltage from the battery pack; wherein the controller processes the modulated response of the first modulated current and the modulated alternating excitation signal to generate battery impedance data of the battery pack.

16. The battery management AC impedance detector of claim 15, wherein, further comprising: a PWM modulator in the controller to generate the pulse modulating signal (PWM_OUT) as a pulse width modulated output signal in response to a modulating signal (PWM_IN) from the controller.

17. A battery management system (BMS) with alternating current impedance detection, characterized by, comprising: a sweeper to adjust the frequency of a modulating signal over a test frequency range when a battery detection mode is activated; a capacitor; a synchronous buck converter to modulate the capacitor with a pulse modulating signal to generate an alternating excitation current to be injected into a battery pack, and the capacitor to be connected between the synchronous buck converter and the battery pack; a current sensor to sense an alternating current value of the alternating excitation current injected into the battery pack; wherein the synchronous buck converter modulates the alternating excitation current over the test frequency range; a sampler to measure an alternating test voltage at an internal node in the battery pack, the alternating test voltage to vary in response to the battery pack to the alternating excitation current; an external connector for connection to an external charger or an external load; a power switch between the battery pack and the external connector, the power switch to be controlled by a switch signal to connect the battery pack to the external connector; and a controller to set the switch signal to an active state during a charge / discharge mode and to set the switch signal to an inactive state during an idle mode; wherein the controller activates the sweeper during a battery detection mode, the battery detection mode to be activated during the charge / discharge mode and to be activated during the idle mode; ​ wherein the AC current value and the AC test voltage are signal processed to form an impedance value indicative of a state of health of the battery pack.

18. The BMS with AC impedance detection of claim 17, wherein, The synchronous buck converter further comprises: a current filter connected between a first terminal of the battery pack and a first buck node; a first unidirectional switch connected between the first buck node and a first terminal of the capacitor; and a second unidirectional switch connected between the first buck node and a second terminal of the battery pack; wherein a second terminal of the capacitor is connected to the second terminal of the battery pack; wherein the first unidirectional switch is enabled to conduct current when the pulse modulation signal is in a first state; wherein the second unidirectional switch is enabled to conduct current when the pulse modulation signal is not in the first state.

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