TWM485518U - Monitoring system of battery internal resistance - Google Patents

Description

Battery internal resistance monitoring system

This creation is related to measuring the internal resistance of the battery; in particular, it is a monitoring system for the internal resistance of the battery.

The battery can be regarded as a voltage source connected in series with an internal resistance, and the potential difference (V) that the battery can provide is equal to the voltage source (E) minus the current flowing through the battery (I) multiplied by the internal resistance (r), meaning V=E -Ir. However, the internal resistance of the battery is not a fixed value. When the battery is placed for a long time or as the number of times and time increases, the internal resistance will gradually increase. According to V=E-Ir, we can know the internal resistance of a battery. Gradually rising, the voltage that it can provide will gradually decrease, which means that the battery is gradually aging, and its rated output voltage cannot be provided normally (the power supply capability is reduced). Therefore, by measuring the internal resistance of the battery and observing the change, it can be used as An assessment of the state of use of the battery.

At present, there are two types of conventional internal resistance measurement methods: DC discharge method and AC injection method.

The DC discharge measuring system 100 is shown in FIG. 1. The battery 2 can be regarded as a voltage source E connected in series with an internal resistance ro. The DC discharging method performs instantaneous high-current discharge through the battery 2 in series with a resistor R, and is measured in amperes. 4 Measure the discharge current I of the battery 2, measure the voltage Vro on the battery 2 in voltmeter 6, and calculate the resistance of the battery internal resistance ro by Ohm's law. However, there are some practical applications in the DC discharge method. For example, when detecting the internal resistance of the battery, the battery must be in a static or offline state for detection, and online (on-line) measurement cannot be achieved. Come, it is very inconvenient for the application. Moreover, the large current discharge will cause considerable damage to the battery, which in turn affects the capacity and life of the battery.

AC discharge measuring system 200 shown in Figure 2, through coupling An AC signal source 8 injects a constant AC signal Is into the battery 2, and measures the voltage Vro across the battery 2 in a voltmeter 6 and the phase difference between the two, thereby calculating the internal resistance r0 of the battery 2. The AC injection method does not need to discharge the battery, and the internal resistance of the battery can be detected online, so it does not affect the life and performance of the battery. However, the AC discharge method needs to measure the AC signal Is, the voltage Vro, and the phase difference between the voltage and the current. It can be seen that this method has many interference factors, which in turn affects the accuracy of the battery internal resistance measurement.

In view of this, the purpose of the present invention is to provide a monitoring system for the internal resistance of the battery, which does not cause damage to the battery during measurement, and can accurately measure the internal resistance of the battery.

In order to achieve the above object, the monitoring system for the battery internal resistance provided by the present invention is applied to a first battery pack and a second battery pack, the first battery pack includes at least one first battery, and the second battery pack includes at least A second battery, the detection system includes a loop switching device, a current measuring device, a multiplexer and a signal processor. The circuit switching device is electrically connected to the first battery group and the second battery group, and the circuit switching device is driven to alternately control the first battery group and the second battery group for discharging; the current measuring device And measuring the current of the first and second battery packs when discharged, and converting into a current signal; the multiplexer having at least one first input port, at least one second input port, and an output埠, the first and second output ports are respectively associated with the first and second The battery pack is electrically connected to receive the voltage signals of the first and second batteries; the multiplexer is controlled to output the voltage signals received by one of the first and second input ports to the output port; The signal processing device is electrically connected to the circuit switching device, the current measuring device, and the multiplexer; the signal processing device drives the circuit switching device to alternately discharge the first and second battery groups, and When the first battery pack is discharged, the multiplexer is controlled to output the voltage signal received by the input port corresponding to the first battery to the output port; and when the second battery pack is discharged, the multiplexer is controlled to be the second The voltage signal received by the corresponding input port of the battery is output to the output port; and the current signal output by the current measuring device and the voltage signal outputted from the output port of the multiplexer are received, and the first First, the internal resistance of the second battery.

The effect of this creation is in the use of two battery resistance alternately The discharge can avoid damage to the battery when measuring the internal resistance of the battery, and the internal resistance of the battery can be accurately measured by the signal processing device.

100‧‧‧DC discharge measuring system

200‧‧‧AC injection measurement system

2‧‧‧Battery

4‧‧‧Ammeter

6‧‧‧voltmeter

8‧‧‧Communication source

Ro‧‧‧ internal resistance

E‧‧‧voltage source

Ro‧‧‧ internal resistance

R‧‧‧resistance

I‧‧‧discharge current

Vro‧‧‧ voltage

Is‧‧‧Communication signal

300‧‧‧Battery internal resistance monitoring system

10‧‧‧Circuit switching device

12‧‧‧First switching element

121‧‧‧First transistor

122‧‧‧First current limiting load

14‧‧‧Second switching element

141‧‧‧second transistor

142‧‧‧Second current-limited load

20‧‧‧ Current measuring device

30‧‧‧Multiple selector

302‧‧‧First Input埠

304‧‧‧Second input埠

306‧‧‧ Output埠

40‧‧‧Signal Processing Unit

42‧‧‧Signal amplification module

44‧‧‧Filter module

441‧‧‧Programmable bandpass filter

442‧‧‧Programmable bandpass filter

46‧‧‧ Analog Digital Converter

48‧‧‧Digital Signal Processing Module

50‧‧‧Digital Analog Converter

B1‧‧‧First battery pack

B11, B12, B13‧‧‧ first battery

B2‧‧‧Second battery pack

B21, B22, B23‧‧‧Second battery

C‧‧‧Filter Capacitor

F‧‧‧Fuse

Figure 1 is a schematic diagram of a DC discharge measurement system.

Figure 2 is a schematic diagram of an AC injection measurement system.

FIG. 3 is a schematic diagram of a monitoring system for battery internal resistance according to a preferred embodiment of the present invention.

In order to explain the present invention more clearly, the preferred embodiment will be described in detail with reference to the accompanying drawings. Referring to FIG. 3, the battery internal resistance monitoring system 300 is a preferred embodiment. In the first battery pack B1 and the second battery pack B2, the battery internal resistance detecting system 300 A primary circuit switching device 10, a current measuring device 20, a multiplexer 30, and a signal processing device 40 are included.

In this embodiment, the first battery pack B1 includes three A battery B11, B12, B13; the second battery pack B2 includes three second batteries B21, B22, B23. The first batteries B11, B12, B13 are connected in series, and the second batteries B21, B22, B23 are also connected in series. In practical applications, the number of the batteries of the first battery pack B1 and the second battery pack B2 is not limited to three, and may be one, two or more.

The circuit switching device 10 is electrically connected to the first battery pack B1 and the second battery pack B2 are driven by the signal processing device 40 to alternately control the first battery pack B1 and the second battery pack B2 for discharging. In this embodiment, the circuit switching device 10 includes a first switching element 12, a second switching element 14, a first wire 16, a second wire 17, and a third wire 18, the first switching element. The first wire 16, the first wire group B1, the second wire 17 and the current measuring device 20 are sequentially connected in series to form a first discharge circuit, and the first switching element 12 includes a first transistor 121. And a first current limiting load 122, the first current limiting load 122 is connected in series with the first transistor 121 to limit the current flowing through. The second switching element 14 sequentially connects the current measuring device 20, the second wire 17, the second battery group B2 and the third wire 18 to form a second discharging circuit, and the second switching element 14 includes a The second transistor 141 and a second current limiting load 142 are connected in series with the second transistor 141 to limit the magnitude of the current flowing therethrough. The first transistor 121 and the second transistor 141 are gold oxide half field effect transistors (MOSFETs) in this embodiment, and the first transistor 121 is controlled by a bias voltage applied to the transistor. The two transistors 141 operate in different working areas, thereby controlling the conduction and deactivation of the first discharge circuit and controlling the conduction and deactivation of the second discharge circuit. Wherein, the first, second, and third wires are used in principle The battery pack can be excited to discharge DC through the load, which can avoid rectifier interference during the line, and generate a low-frequency, sinusoidal AC signal with amplitude of about 0.01C10 to 0.05C10 for measurement by the subsequent circuit.

The current measuring device 20 is configured to measure the first and second storage The current when the battery packs B1 and B2 are discharged is converted into a current signal. The first discharge circuit and the second discharge circuit respectively inject current into the current measuring device 20 from two different directions. In practice, the current measuring device 20 can employ a shunt, which is a resistor capable of passing a very large current. When a current flows through the shunt, a millivolt-level voltage is generated at both ends thereof to constitute a current. The current signal is converted into a current in the processing circuit of the latter stage to complete the measurement of the large current.

The multiplexer 30 has three first outputs 埠 302, three A second output port 304 and an output port 306. Each of the first input ports 302 is electrically connected to the positive and negative poles of the first battery B11, B12, B13, and each of the second input ports 304 is connected to the positive and negative poles of the second battery B21, B22, B23. Electrically connected to receive voltage signals of the first batteries B11, B12, B13 and the second batteries B21, B22, B23. The multiplexer 30 is controlled by the signal processing device 40, and the voltage signals received by one of the first and second input ports 302, 304 are output to the output port 306. In practical applications, the number of the first and second input ports 302, 304 is matched with the number of the first batteries B11, B12, B13 and the second batteries B21, B22, B23.

The signal processing device 40 and the circuit switching device 10. The current measuring device 20 and the multiplexer 30 are electrically connected. The signal processing device 40 controls the first transistor 121 of the first switching element 12 and the second transistor 141 of the second switching element 14 to be turned on to separately control the first and second battery packs. B1 and B2 are alternately discharged, and the multiplexer 30 is controlled to discharge the first battery pack B1 when the first battery pack B1 is discharged. The voltage signal received by the corresponding input port 302 of the battery is output to the output port 306; and the voltage received by the multiplexer 30 corresponding to the input port 304 of the second battery B2 is also controlled when the second battery pack B2 is discharged. The signal is output to the output port 306; and the current signal outputted by the current measuring device 20 and the voltage signal output from the output port 306 of the multiplexer 30 are received, and the first and second batteries are calculated accordingly. Internal resistance.

In more detail, the signal processing device 40 includes sequential coupling A signal amplification module 42 , a filter module 44 and a digital signal processing module 48 are connected. The signal amplifying module 42 is electrically connected to the current measuring device 20 and receives the current signal. The signal amplifying module 42 is also connected to the multiplexer 30 to receive the voltage signal output by the output port 306, and respectively The signal is amplified and transmitted to the filter module 44. Between the signal amplifying module 42 and the current measuring device 20, the signal amplifying module 42 and the output 埠 306 of the multiplexer 30 are respectively coupled with a plurality of filter capacitors C, the filter capacitors C can filter out the noise existing in the current signal and the voltage signals of the batteries, for example, can eliminate the surge generated by the first and second discharge circuits when the first and second switching elements 12 and 14 are opened and closed .

The filter module 44 is to be amplified from the signal amplification module 42 The current signal and the voltage signal are filtered, and a sample current signal and a sample voltage signal are output to the digital signal processing module 48. In this embodiment, the filter module 44 includes two programmable band pass filters 441 and 442. The programmable band pass filters 441 and 442 are controlled by the digital signal processing module 48 and can specify a specific frequency band. The signal passes and filters out signals from other frequency bands. Since the first discharge circuit and the second discharge circuit respectively inject current from the opposite directions to the current measuring device 20 to form two opposite polarity current signals, the programmable band pass filter 441 is further The reverse current signal can be converted to a positive current signal.

The digital signal processing module 48 is electrically connected to the second analogy An analog-to-digital converter (ADC) 46 and a digital-to-analog converter (DAC) 50, the binary-to-digital converter 50 receives the output of the digital signal processing module 48. The control signal is converted into an AC pulse signal having a frequency less than 1000 Hz, and is transmitted to the first transistor 121 and the second transistor 141 to control the conduction and the turn-off of the first and second discharge circuits, that is, the first 1. The discharge of the second battery pack B1, B2 is not. The second analog-to-digital converter 46 receives the sampled current signal and the sampled voltage signal and converts them into corresponding digital signals, and the digital signal processing module 48 further digitizes the sampled current signal and the sampled voltage signal. The signal performs a Fast Fourier Transform (FFT) to calculate a spectral distribution of the sampled current signal and the sampled voltage signal, and extracts the sampled current signal and the sampled voltage signal of a specific frequency from the spectrum distribution, The internal resistance of the first battery and the second battery is calculated. The filter module 44 and the fast Fourier transform system are set for the use environment of the online monitoring, so as to avoid the noise interference caused by the external charging circuit charging the first and second battery packs B1 and B2, so that the measured inner The resistance produces an error.

With the above structure, the author will be further explained later. The operating sequence of the internal resistance of the batteries of the first and second battery packs B1, B2 is measured. First, the digital signal processing module 48 outputs the AC pulse signal through a digital analog converter 50. In this embodiment, a 70 Hz AC pulse signal is applied to the first transistor 121 to turn on the first discharge circuit. The first battery B11, B12, B13 of the first battery pack B1 is discharged, and at the same time, the digital signal processing module 48 also controls the multiplexer 30 to be connected to the first battery B11. The voltage signal measured by the first output port 302 is transmitted to the signal processing device 40 via the output port 306, and the current measuring device 20 measures that the current signal from the first discharging circuit is also transmitted to the signal. Signal processing device 40, the signal processing device 40 The internal resistance of the first battery B11 is measured.

After the internal resistance of the first battery B11 is measured, the digital position The signal processing module 48 outputs the AC pulse signal to the second transistor 141 through another digital analog converter 50 to turn on the second discharge circuit (at this time, the digital signal processing module does not transmit the signal to the first a transistor 121, so that the first discharge circuit is in an off state), the second batteries B21, B22, B23 are discharged, and at the same time, the digital signal processing module 48 controls the multiplexer 30 to The voltage signal measured by the second output port 304 connected to the second battery B21 is transmitted to the signal processing module 40 via the output port 306, and the current measuring device 20 measures the first signal. The current signal of the discharge circuit is also transmitted to the signal processing device 40, and the signal processing device 40 measures the internal resistance of the second battery B21.

After measuring the internal resistance of the second battery B21, it is sequentially replaced The first battery B12, the second battery B22, the first battery B13, and the second battery B23 are measured, and then the first battery B11 is measured to continuously monitor the internal resistance of the batteries B11 to B23. . In other words, the signal processing device 40 selects one of the voltage signals received by the first input port 302 to output to the output port 306 when the first battery pack B1 is discharged, and selects the first input port 302 each time the battery is discharged. Different from the first input port 302 selected during the previous discharge; the signal processing device 40 selects to output the voltage signal received by one of the second input ports 304 to the output port 306 when the second battery pack B2 is discharged. And the second input port 304 selected at each discharge is different from the second input port 304 selected last time, so as to achieve the purpose of monitoring the internal resistance of the battery.

In addition, the monitoring system 300 in this embodiment further includes plural Fuse F, the fuses F are respectively disposed between the first battery pack B1 and the first current limiting load 122, between the current measuring device 20 and the first and second battery packs B1, B2, and the second battery pack B2 and the second current limiting load Between 142, each of the first batteries B11, B12, B13 and each of the second batteries B21, B22, B23 and the first input port 302 of the multiplexer 30 and each of the second input ports 304 . The fuses F can be used to prevent the first and second transistors 121, 141 and the multiplexer 30 from being damaged when the current is too large.

In summary, the battery internal resistance monitoring system 300 of the present invention has the following features:

1. Safe and reliable: no equipment is connected in the main working circuit of the battery pack. The measuring circuit is designed with finite current resistance and fuse. The measuring circuit is designed for high impedance. The working circuit of the battery pack is safe and independent of the measuring circuit. Impact and replace battery monitoring equipment when the battery pack is working online.

2. Low discharge current: The high-impedance design makes the battery discharge current small and does not lose battery life.

3. Strong anti-interference: It is suitable for on-line measurement of battery packs, filtering with band-pass filter, and converting analog signals into digital signals for processing, which can effectively eliminate the influence of DC charging device ripple on measurement.

4. High monitoring accuracy: the signal is processed by the operational amplifier, band-pass filter and digital signal, so that the monitoring system of the internal resistance of the battery is more accurate than the traditional DC discharge method and AC injection method, which can accurately reflect the battery. The aging condition, in turn, reaches the prediction of battery life.

The above is only a preferred embodiment of the present invention, and equivalent changes to the scope of the present application and the scope of the patent application are intended to be included in the scope of the present patent.

300‧‧‧Battery internal resistance monitoring system

10‧‧‧Circuit switching device

12‧‧‧First switching element

121‧‧‧First transistor

122‧‧‧First current limiting load

14‧‧‧Second switching element

141‧‧‧second transistor

142‧‧‧Second current-limited load

16‧‧‧First wire

17‧‧‧Second wire

18‧‧‧ Third wire

20‧‧‧ Current measuring device

30‧‧‧Multiple selector

302‧‧‧First Input埠

304‧‧‧Second input埠

306‧‧‧ Output埠

40‧‧‧Signal Processing Unit

42‧‧‧Signal amplification module

44‧‧‧Filter module

441‧‧‧Programmable bandpass filter

442‧‧‧Programmable bandpass filter

46‧‧‧ Analog Digital Converter

48‧‧‧Digital Signal Processing Module

50‧‧‧Digital Analog Converter

B1‧‧‧First battery pack

B11, B12, B13‧‧‧ first battery

B2‧‧‧Second battery pack

B21, B22, B23‧‧‧Second battery

C‧‧‧Filter Capacitor

F‧‧‧Fuse

Claims (11)

A battery internal resistance monitoring system is applied to a first battery pack and a second battery pack, the first battery pack includes at least one first battery, and the second battery pack includes at least one second battery; the monitoring system The method includes: a first circuit switching device electrically connecting the first battery group and the second battery resistance, the circuit switching device being driven to alternately control the first battery group and the second battery group to discharge; Measuring device for measuring the current of the first and second battery packs when discharged, and converting into a current signal; a multiplexer having at least one first input port and at least one second input port And an output port, the first and second output ports are electrically connected to the first and second battery groups respectively to receive voltage signals of the first and second batteries; the multiplexer is controlled to be the first 1. The voltage signal received by one of the second input ports is output to the output port; and a signal processing device is respectively associated with the circuit switching device and the current measuring device And the multiplexer is electrically connected; the signal processing device drives the circuit switching device to alternately discharge the first and second battery groups, and controls the multiplexer to be the first when the first battery pack is discharged The voltage signal received by the corresponding input port of the battery is output to the output port; when the second battery pack is discharged, the multiplexer is controlled to output the voltage signal received by the input port corresponding to the second battery to the output port; Receiving the current signal output by the current measuring device and the output from the multiplexer The voltage signal outputted by 埠 is used to calculate the internal resistance of the first and second batteries. The monitoring system of the internal resistance of the battery according to claim 1, wherein the number of the at least one first battery and the at least one second battery are respectively plural, the first batteries are connected in series, and the second batteries are connected in series. The number of the at least one first input port and the at least one second input port are respectively plural; the signal processing device selects one of the voltage signals received by the first input port to output to the first battery pack when discharging The output 埠, and the first input 选择 selected at each discharge is different from the first input 选择 selected at the previous discharge; the signal processing device selects one of the second inputs when the second battery pack is discharged The received voltage signal is output to the output port, and the selected second input port is different from the previous selected second input port. The monitoring system of the internal resistance of the battery according to claim 1, wherein the circuit switching device comprises a first switching element, a second switching element, a first wire, a second wire and a third wire, the first The switching element sequentially connects the first wire, the first battery group, the second wire and the current measuring device to form a first discharging circuit; the second switching element sequentially connects the current measuring device, the first The two wires, the second battery group, and the third wire have formed a second discharge circuit; the signal processing device separately controls the first switching element, and the second switching element is turned on to respectively make the first battery The group and the second battery pack are discharged. The monitoring system of the internal resistance of the battery according to claim 3, wherein the first switching element comprises a first transistor and a first current limiting load, the first transistor Connected to the first current limiting load, the first transistor is controlled by the signal processing device to turn on or off the first discharging circuit, the first current limiting load is used to limit current flowing through the first transistor; The second switching element includes a second transistor and a second current limiting load. The second transistor is coupled to the second current limiting load, and the second transistor is controlled by the signal processing device to turn on or off the second transistor. a second discharge circuit for limiting current flow through the second transistor. The battery internal resistance monitoring system of claim 4, wherein the first transistor and the second transistor are metal oxide half field effect transistors (MOSFETs). The monitoring system of the internal resistance of the battery according to claim 1, wherein the current measuring device comprises a shunt, the shunt converting the current discharged by the first battery pack or the second battery pack into a voltage to constitute the current Signal. The monitoring system for the internal resistance of the battery according to claim 1 includes a plurality of filter capacitors, a portion of the filter capacitor is electrically connected between the current measuring device and the signal processing device, and another portion of the filter capacitor is electrically connected to the filter capacitor. The output of the multiplexer is connected to the signal processing device; the filter capacitors filter out the noise of the current signal and the voltage signals of the first and second batteries. The monitoring system of the internal resistance of the battery according to claim 1, wherein the signal processing device comprises a signal amplifying module, a filtering module and a digital signal processing module coupled in sequence; the signal amplifying module receives the The current signal and the voltage signal outputted by the output port are respectively amplified and transmitted to the filter module. The filter module filters the amplified current signal and the voltage signal, and outputs a sampled current signal and a sample. Voltage signal to the number a bit signal processing module; the digital signal processing module receives the sampled current signal and the sampled voltage signal to calculate an internal resistance value of the first battery and the second battery. The monitoring system of the internal resistance of the battery according to claim 8, wherein the filter module is a programmable band pass filter, and the programmable band pass filter is controlled by the digital signal processing module to enable the current signal and the The signal in a specific frequency band of the voltage signal passes, and the other frequency band signals are filtered out. The monitoring system of the internal resistance of the battery according to claim 8, comprising an analog-to-digital converter (ADC) coupled between the filter module and the digital signal processing module, the analogy The digital converter receives the sampled current signal and the sampled voltage signal respectively, and converts the signal into a corresponding digital signal, and the digital signal processing module performs fast Fourier transform on the sampled current signal and the digital signal of the sampled voltage signal (Fast Fourier) Transform, FFT), to calculate a spectral distribution of the sampled current signal and the sampled voltage signal, extracting the sampled current signal and the sampled voltage signal of a specific frequency from the spectrum distribution, thereby calculating the first battery and The internal resistance of the second battery. The battery internal resistance monitoring system of claim 1 includes a plurality of fuses, and a portion of the fuse is electrically connected between the circuit switching device and the first and second battery packs, and a portion of the fuse is electrically connected to the fuse The first and second batteries are coupled between the first input port and the second input port of the multiplexer.