CN109119706B

CN109119706B - Battery pack and battery module capable of detecting contact point

Info

Publication number: CN109119706B
Application number: CN201710479912.5A
Authority: CN
Inventors: 约翰尼斯·P·M·范拉默恩
Original assignee: Datang NXP Semiconductors Co Ltd
Current assignee: Datang NXP Semiconductors Co Ltd
Priority date: 2017-06-22
Filing date: 2017-06-22
Publication date: 2021-03-26
Anticipated expiration: 2037-06-22
Also published as: CN109119706A

Abstract

Disclosed are a battery pack and a battery module capable of detecting a contact point. The battery pack may include at least a first battery module, a second battery module, a first isolation circuit, and a second isolation circuit. Each battery module includes at least a first battery cell and a second battery cell, and a power connection line for coupling a first electrode of the first battery cell to a second electrode of the second battery cell. The first battery cell includes a monitor. The first isolation circuit and the second isolation circuit provide a voltage transfer path while providing isolation. The monitor includes: a transmitter/receiver in signal communication with the second battery cell via the communication conductor; and a voltage difference detector coupled to the power connection line and the voltage delivery path for detecting a voltage difference between the power connection line and the voltage delivery path, wherein the monitor indicates degradation of the contact point of the power connection line if the detected voltage difference is outside a predetermined threshold range.

Description

Battery pack and battery module capable of detecting contact point

Technical Field

The present invention relates generally to battery packs, and more particularly to a method and apparatus for monitoring in battery packs.

Background

A battery pack formed of a plurality of battery cells connected in series is widely used for a power source, particularly in mobile electric appliances. As is well known, in (hybrid) electric vehicles, a battery pack (battery pack) is used to generate a high voltage to drive a motor. In such batteries, a plurality of battery cells (battery cells) are coupled in series by conductive power connection lines, where each power connection line may electrically couple the positive electrode of one battery cell to the negative electrode of an adjacent battery cell, such as by welding or bolting.

Each component on the current path in the battery pack is preferably designed to have a small resistance to reduce useless power dissipation, especially when the current flowing through the battery cells is large (e.g., several hundred amperes). Typically, the contact point resistance between the power connection line and the battery electrode may be taken into account. Further, the contact resistance will increase if the contact is corroded, loosened, aged, or the like. If the battery current is high, even a contact resistance of only 1 milliohm (1m Ω) will be unacceptable. For example, with a battery current of 100A, it would produce a power dissipation of 10W, which is undesirable. Furthermore, high contact resistance will lead to hot spots, which severely limits the lifetime of the battery cell involved. In the case of severe corrosion, the temperature rise may even lead to fire or explosion.

Accordingly, methods and apparatus for contact point detection in battery packs are desired.

Disclosure of Invention

The invention discloses a battery pack and a battery module capable of detecting a contact point.

In one embodiment, a battery pack is disclosed. The battery pack may include at least a first battery module, a second battery module, a first isolation circuit, and a second isolation circuit. Each battery module includes at least a first battery cell and a second battery cell, and a power connection line coupling a first electrode of the first battery cell to a second electrode of the second battery cell. The first battery cell includes a monitor. The first isolation circuit is coupled to the first battery module and comprises a first transformer, a first resistor and a second resistor, two ends of a first side of the first transformer are coupled to the first battery module, the first resistor and the second resistor are connected between two ends of a second side of the transformer in series, and a connection point of the first resistor and the second resistor is connected to a monitor of one battery unit of the first battery module. The second isolation circuit is coupled to the second battery module and comprises a second transformer, a third resistor and a fourth resistor, two ends of a first side of the second transformer are coupled to the second battery module, a second side of the second transformer is connected with a second side of the first transformer, the third resistor and the fourth resistor are connected between two ends of a second side of the second transformer in series, and a connection point of the third resistor and the fourth resistor is connected to a second electrode of one battery unit of the second battery module. The monitor includes: a transmitter and receiver in signal communication with the second battery cell via a communication conductor; and a voltage difference detector coupled to the power connection line and the communication conductor for detecting a voltage difference between the power connection line and the communication conductor, wherein the monitor indicates degradation of a contact point of the power connection line if the detected voltage difference is outside a predetermined threshold range.

In one aspect, the first isolation circuit further includes a first capacitor, one end of the first capacitor is connected to a connection point between the first resistor and the second resistor, and the other end of the first capacitor is connected to the first electrode of one of the battery cells of the first battery module.

In one aspect, the first isolation circuit further includes a second capacitor and a third capacitor, and two ends of the first side of the first transformer are coupled to the first battery module through the second capacitor and the third capacitor, respectively.

In one aspect, the first isolation circuit further includes a fourth capacitor and a fifth capacitor, and two ends of the first side of the second transformer are coupled to the second battery module through the fourth capacitor and the fifth capacitor, respectively.

In one aspect, the voltage difference detector is configured to detect the voltage difference when the transmitter/receiver is receiving signal communications via the communication conductor.

In one aspect, the signal communication via the communication conductor occurs in a current domain or a voltage domain, and the voltage difference detector detects a DC voltage difference between the power connection line and the communication conductor.

In one aspect, the contact degradation includes at least one of contact corrosion or contact loosening.

In one aspect, the monitor is integrated within the first cell, wherein the voltage difference detector is coupled to a first electrode of the first cell; or the monitor is external to the first battery cell, wherein the voltage difference detector is coupled to the power connection line.

In one aspect, the monitor further comprises a voltage difference detector coupled to another electrode of the first cell.

In another embodiment, a battery module is disclosed that includes at least a first battery cell, a second battery cell, an isolation circuit, and a power connection line for coupling a first electrode of the first battery cell to a second electrode of the second battery cell. The first battery cell includes a monitor. The isolation circuit comprises a transformer, a first capacitor, a first resistor and a second resistor, wherein two ends of a first side of the transformer are coupled to the first battery unit, a second side of the transformer is suitable for being connected with another battery module, the first resistor and the second resistor are connected in series between two ends of the second side of the transformer, and a connection point of the first resistor and the second resistor is connected to a monitor of the first battery unit through a voltage wire. The monitor includes: a transmitter/receiver in signal communication with the second battery cell via a communication conductor; and a voltage difference detector coupled to the power connection line and the communication conductor for detecting a voltage difference between the power connection line and the communication conductor, wherein the monitor indicates degradation of a contact point of the power connection line if the detected voltage difference is outside a predetermined threshold range.

In yet another embodiment, a connection assembly adapted to connect two adjacent battery modules of a battery pack is disclosed, the connection assembly including a first isolation circuit and a second isolation circuit. The first isolation circuit is coupled to a first battery module and comprises a first transformer, a first resistor and a second resistor, two ends of a first side of the first transformer are coupled to the first battery module, the first resistor and the second resistor are connected between two ends of a second side of the transformer in series, and a connection point of the first resistor and the second resistor is connected to a monitor of one battery unit of the first battery module. The second isolation circuit is coupled to a second battery module and comprises a second transformer, a third resistor and a fourth resistor, two ends of a first side of the second transformer are coupled to the second battery module, a second side of the second transformer is connected with a second side of the first transformer, the third resistor and the fourth resistor are connected between two ends of a second side of the second transformer in series, and a connection point of the third resistor and the fourth resistor is connected to a second electrode of one battery unit of the second battery module.

With the present invention, contact point degradation (e.g., corrosion or loosening) or onset of degradation can be detected by the monitor without adding external components or wires to the battery pack. By simply monitoring the voltage difference between the power connection lines and the corresponding communication conductor, the increase in contact point resistance can be measured for each individual power connection line in the battery pack. All the required additional circuitry can be easily integrated into the cell monitor. Such detection is beneficial for improving the performance of the battery pack, extending battery life between recharges, and avoiding potential damage to the battery pack.

Drawings

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below, wherein:

fig. 1 is a top view of an exemplary battery pack according to an embodiment of the present invention;

fig. 2 schematically depicts a functional block diagram of a battery pack with an integrated monitor according to an embodiment of the present invention;

fig. 3A is a block diagram of a battery pack with an integrated monitor according to an embodiment of the present invention;

fig. 3B is a block diagram of a battery pack with an integrated monitor according to another embodiment of the present invention;

fig. 4 is a block diagram of a battery pack having an integrated monitor according to still another embodiment of the present invention;

FIG. 5 is a block diagram of a battery cell with an integrated monitor according to an embodiment of the present invention;

fig. 6 is a block diagram of a battery pack having a plurality of battery modules; and

fig. 7 is a block diagram of a battery pack having an isolation circuit according to an embodiment of the present invention.

Detailed Description

The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments of the present invention and is not intended to represent the only exemplary embodiments in which the present invention may be practiced. The detailed description includes specific details to provide a thorough understanding of the exemplary embodiments of the present description. It will be apparent to one skilled in the art that the exemplary embodiments of the present description may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the exemplary embodiments presented herein.

The words "example" or "exemplary" used throughout this application are used for illustration only and not for limitation. Further, it will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. For a reference numeral bearing an alphabetical character designation (such as "202 a" or "202 b"), the alphabetical character designation may distinguish two similar components or elements present in the same figure. Where a reference numeral is intended to encompass all elements having the same reference numeral in all figures, such alphabetic designation may be omitted.

Fig. 1 is a top view of an exemplary battery pack 100 composed of a plurality of battery cells 110. For clarity, battery pack 100 is shown with 8 battery cells 110. It should be understood, however, that a battery pack according to the present invention may have more or fewer battery cells. The battery cells 110 are coupled in series by conductive power connection lines 102, the power connection lines 102 connecting the positive electrode of one battery cell to the negative electrode of an adjacent battery cell. Such power connection wires 102 may be electrically connected to the battery cell electrodes through welded or bolted contact points 104 or the like.

Fig. 2 schematically depicts a block diagram of a battery pack 200 with an integrated monitor 212 according to an embodiment of the invention. The battery pack 200 includes a plurality of battery cells 210 connected in series by power connection lines 202 (e.g., 202a, 202 b). Each cell 210 has a positive electrode a and a negative electrode B. Each terminal of the power connection line 202 may be electrically coupled to a corresponding battery cell electrode through a welded or bolted contact point, or the like.

Fig. 2 also shows an optional switching resistor Rconv in series with the battery cell 210. Optional current monitor 220 may detect a voltage drop across resistor Rconv, which effectively reflects the battery pack current flowing through the series-connected cells 210 and thus may be used for monitoring purposes. The battery pack 200 may further include a battery pack controller 230 to control operation of the battery pack 200 based on the detected measurements and/or input commands. The battery cells 210 (and current monitor 220, if applicable) may communicate with the battery pack controller 230 via the daisy-chained communication conductors 206. Specifically, signals to be communicated between any battery cell 210 and the battery pack controller 230 may pass through other battery cells 210 (or other components, if any) located therebetween.

According to one embodiment of the invention, one or more of the cells 210 may have an integrated monitor 212 for at least contact point detection of the cell 210. Such a monitor 212 may be integrated within the battery cell 210. Alternatively, the monitor 212 may be built into the battery pack 200 and outside of the associated cell 210, preferably as close as possible to the cell being monitored.

According to an embodiment of the invention, the battery cells 210 supply voltages VDD and VSS to the associated monitors 212, wherein the DC level of the communication conductor 206 may be set based on (e.g., equal to) VDD of the communicating monitor 212. During normal conditions, the power connection 202 between each pair of cells 210 has the same (or substantially the same) potential as the connected cell electrode, and thus may serve as a signal ground (VSS) for the respective communication conductor 206. The voltage difference between the power connection 202 and the corresponding communication conductor 206 is approximately equal to 0 or (VDD-VSS), depending on which monitor 212 is transmitting on the communication conductor 206.

However, if the contact point between the power connection line 202 and the cell electrode degrades (e.g., corrodes, loosens, or is otherwise damaged), the contact point resistance between the power connection line 202 and the cell electrode will increase and cause an increased voltage drop. Accordingly, the potential in the current path downstream of the degraded contact point will drop compared to the normal situation and the voltage difference between the power connection line 202 and the respective communication conductor 206 will change. It is therefore possible for the monitor 212 to perform contact point monitoring by monitoring the voltage difference between the power connection lines 202 and the respective communication conductors 206. Specifically, the monitor 212 associated with the battery cell 210 is configured to measure a voltage difference between the power connection line 202 and the respective communication conductor 206, and may compare the detected voltage difference to a threshold value to ascertain whether the contact points are damaged (e.g., corroded, loosened, etc.), as described in more detail below.

Fig. 3A is a block diagram of a battery pack with an integrated monitor 212 in a single-sided monitoring configuration in an embodiment of the invention. Illustratively, two battery cells 210-1 and 210-2 in a battery pack are shown and are connected to each other at nodes C and D by power connection 202 b. Monitors 212-1 and 212-2 are integrated into the battery cells 210-1 and 210-2, respectively. Note that line segment BC or AD represents the electrode of the corresponding battery cell 210. Other battery cells in the battery pack may be similarly configured.

The monitors 212 may each include digital circuitry 326, with the digital circuitry 326 being used to perform analysis on the detected measurements or to control the operation of the battery cells 210 based on these measurements and/or commands from the battery pack controller 230 (see fig. 2). A transmitter/receiver (TRx) 328 may also be provided in signal communication over communication conductors 206. For example, the TRx 328 may receive information from the digital circuitry 326 and communicate the information to other battery cells 210 and/or to the battery pack controller 230 via the communication conductor 206. Additionally, the TRx 328 may receive signals from other battery cells 210 and/or the battery pack controller 230 via the communication conductors 206 and pass them to the digital circuitry 326.

According to an embodiment of the invention, each monitor 212 may include a voltage difference detector 312 on at least one electrode side of the associated battery cell 210 for measuring a voltage difference between the power connection line 202 (e.g., 202a, 202b, 202c …) and the corresponding communication conductor 206 (e.g., 206a, 206b, 206c …). As mentioned above, such voltage differences reflect the contact point condition between the power connection line 202 and the battery cell electrodes. As shown in fig. 3A, the voltage difference detector 312 is coupled to the negative electrode of the associated battery cell 210.

Communication over communication conductor 206 may be in the current domain or the voltage domain. If the communication is in the current domain, the receiving side acts as a virtual ground for the associated voltage difference detector 312, which voltage difference detector 312 is able to perform a DC measurement directly between the power connection line 202 and the communication conductor 206. On the other hand, if the communication is in the voltage domain, the voltage difference measurement may be made while the output of the transmitter is at ground potential. In addition, filtering or timing may be employed to separate the DC voltage difference between the power connection lines and the communication conductor from the communication signal on the communication conductor 206. Even when no information needs to be conveyed on communication conductor 206, digital circuitry 326 may instruct Trx 328 to transmit dummy signals on communication conductor 206 for voltage difference measurement purposes based on the scheduled timing. Since each monitor 212 (and in particular digital circuit 326) knows what communications are being made on communication conductor 206, digital circuit 326 is able to control voltage difference detector 312 to perform voltage difference measurements at the appropriate times.

When the monitor 212 is located in the battery cell 210, the battery cell 210 supplies voltages VDD and VSS from the positive electrode a and the negative electrode B, respectively, to the monitor 212. Under normal conditions, when TRx 328-1 receives signal communications from battery cell 210-2 over communication conductor 206b, voltage difference detector 312-1 will detect a 0 (or small) voltage difference between power connection line 202b and communication conductor 206 b. Otherwise, if the contact point C (or D) between the power connection line 202B and the associated cell electrode degrades and thus has an increased resistance, there will be an increased voltage drop across the degraded contact point, resulting in a drop in the potential on the negative electrode B of the cell 210-1. Thus, when TRx 328-1 receives on communication conductor 206b, voltage difference detector 312-1 will detect a change in voltage difference between power connection line 202b and communication conductor 206 b. If the detected voltage difference (e.g., its absolute value) exceeds a predetermined threshold range (e.g., exceeds a predetermined threshold), the voltage difference detector 312-1 may issue a signal to indicate that the contact point of the power connection line 202b is degraded. For example, the voltage difference detector 312-1 may send an alarm signal to TRx 328-1, which TRx 328-1 in turn communicates to the battery pack controller 230.

Similarly, when TRx 328-2 receives signal communications on communication conductor 206c, voltage difference detector 312-2 in battery unit 210-2 may monitor the contact point condition of power connection line 202c by measuring the voltage difference between power connection line 202c and communication conductor 206 c. In the same way, it is possible to monitor all contact points between the power connection lines 202 and the associated cell electrodes in the battery pack.

Alternatively, as shown in fig. 3B, the voltage difference detector 312 may be coupled to the positive electrode a of the associated battery cell 210. Normally, when TRx 328-2 receives a signal communication on communication conductor 206b, voltage difference detector 312-2 in battery cell 210-2 will detect a normal voltage difference (e.g., VDD-VSS for battery cell 210-1) between power connection line 202b and communication conductor 206 b. Otherwise, if the contact point C (or D) between the power connection line 202b and the associated cell electrode degrades and thus has an increased resistance, the potential (VDD) on the positive electrode a of the cell 210-1 will drop. Accordingly, the voltage difference detector 312-2 will detect a change in voltage difference between the power connection line 202b and the communication conductor 206 b. If the detected voltage difference is outside of a predetermined threshold range (e.g., below a predetermined threshold), the voltage difference detector 312-2 may issue a signal to indicate that the contact point of the power connection line 202b is degraded.

Similarly, voltage difference detector 312-1 in battery cell 210-1 may monitor the contact point condition of power connection line 202a by measuring the voltage difference between power connection line 202a and communication conductor 206 a. As above, by each monitor 212 having a voltage difference detector 312 on the positive electrode a or negative electrode B of the associated cell 210, it is possible to monitor all contact points between the power connection line 202 and the associated cell electrode in the battery pack.

Fig. 4 is a block diagram of a battery pack having an integrated monitor 212 according to another embodiment of the present invention. Fig. 4 is similar to fig. 3, except that the monitor 212 is built external to the associated cell 210. Accordingly, the designation of nodes a and B represents the battery cell electrodes a and B and their contact points with the power connection line 202. In this configuration, the battery cells 210 supply voltages VDD and VSS from the power connection lines 202 coupled to the positive and negative electrodes a and B, respectively, to the associated monitors 212. Additionally, a voltage difference detector 312 may be coupled to the power connection line 202.

As above, if a degraded contact point (e.g., node a or B of battery cell 210-1) causes a potential drop, voltage difference detector 312-1 will detect a change in voltage difference between power connection line 202B and communication line 206B when TRx 328-1 transmits on communication line 206B. The voltage difference between power connection line 202b and communication conductor 206b implicitly reflects the voltage across battery cell 210-1. If the detected voltage difference is outside of a predetermined threshold range (e.g., below a predetermined threshold), the voltage difference detector 312-1 may issue a signal to indicate degradation of the contact point of the battery cell 210-1 with the

power connection line

202a or 202 b. Each battery cell 210 may be similarly detected.

Alternatively, if the voltage difference detector 312 is coupled to the power connection line 202 and the corresponding communication conductor 206 on the positive electrode a of the associated battery cell 210, the degraded contact point a (or B) of the battery cell 210-1 causes the potential on the power connection line 202a to drop. When TRx 328-2 receives on communication conductor 206b, voltage difference detector 312-2 in battery cell 210-2 will detect a change in voltage difference between power connection line 202b and communication conductor 206 b. If the detected voltage difference is outside of a predetermined threshold range (e.g., below a predetermined threshold), the voltage difference detector 312-2 may issue a signal to indicate degradation of the contact point of the battery cell 210-1 with the

power connection line

202a or 202 b. Each battery cell 210 may be similarly detected.

Fig. 5 is a block diagram of battery cells in a battery pack with an integrated monitor according to a double-sided monitoring configuration in an embodiment of the present invention. Specifically, the monitor 212 may include a voltage difference detector 312 on both electrode sides of the battery cell 210. For example, voltage difference detector 312a is coupled to power connection line 202a and corresponding communication conductor 206a, and voltage difference detector 312b is coupled to power connection line 202b and corresponding communication conductor 206 b. The

voltage difference detectors

312a and 312b operate similarly to the aforementioned voltage difference detector 312 coupled to the positive electrode side and the negative electrode side, respectively. Although the monitor 212 is shown as being integrated within the battery cell 210, the monitor 212 may also be constructed external to the battery cell 210 in a similar manner as shown in fig. 4. Having two voltage difference detectors in each monitor enables monitoring of the power connection line 202 and corresponding communication conductor 206 at all times regardless of the direction of signal communication on the communication conductor 206, thereby providing redundancy to meet high automotive safety requirements (e.g., ASIL), which is desirable in automotive applications.

Optionally, the monitor 212 may further include an ADC 322 for monitoring the voltage across the battery cell 210, a temperature sensor 324 for continuously monitoring the temperature within the battery cell 210, a pressure sensor (not shown), and other sensors for measuring other parameters of the battery cell 210. Digital circuitry 326 may receive and analyze various measurements to determine the state of health of the battery cells over time, and control the operation of battery cells 210 based on these measurements or commands from battery pack controller 230.

In one embodiment, the voltage difference detector 312 described above may be implemented with a comparator configured to compare the measured voltage difference (or its absolute value) with a predetermined threshold. Once the measured voltage difference exceeds the threshold, the comparator may trigger to signal either the digital circuit 326 or the battery pack controller 230. The threshold range (or threshold) may be programmable or configurable to optimize the system for different applications and usage scenarios. Such a threshold range (or threshold) may be determined based on a normal range (or normal value) and an appropriate margin. By way of example and not limitation, assuming a normal contact has a typical resistance of 0.1 milliohms and the battery current has a peak of 200A, the result is a peak contact voltage of 20mV in the "normal" range. An appropriate threshold for the comparator may be set at 40mV, which will allow for double contact resistance. The margin may depend on the specific application and the overall constraints imposed on the battery.

In another embodiment, the voltage difference detector 312 described above may be implemented with a Schmitt trigger (Schmitt trigger). Schmitt triggers are a class of comparators with built-in trigger voltages and hysteresis. In this manner, the voltage difference between each power connection line and its associated communication conductor can be measured at all times regardless of the direction of signal communication on communication conductor 206.

In an alternative embodiment, the voltage difference detector 312 may be implemented with an analog-to-digital converter (ADC) to sense the voltage difference between the power connection line 202 and the communication conductor 206. The ADC may convert the measured voltage difference to a digital value and send it to digital circuitry 326 for processing. In this case, digital circuitry 326 may include a comparator or software routine to determine whether the voltage difference is above or below a threshold. The advantage of digitization is that the measured "contact" voltage can be divided by the battery current, so that the contact resistance can be measured with the desired accuracy. In some applications, the ADC 322 may be time division multiplexed to alternately convert the battery cell voltage or the measured voltage difference. Accordingly, the voltage difference detector 312 may be eliminated.

The information detected by the voltage difference detector 312, as well as other measurements monitored by the monitor 212, may be communicated to the battery pack controller 230 via the TRx 328 and the daisy-chained communication conductor 206. As an option, an OK/NOK signal indicating that the voltage across the power connection line contact is below/above a threshold may be communicated to the battery controller 230. Alternatively, the monitor 212 may communicate the measured voltage difference to the battery pack controller 230, and the battery pack controller 230 may then determine whether the power connection line contact points are operating properly. Additionally, the transmitted signal may include an identifier corresponding to the detected contact point, such that degraded contact points can be accurately located.

If a degraded contact point is detected (e.g., due to corrosion, loose contact points, etc.), appropriate action may be taken. For example, the battery pack controller 230 may alert a user (e.g., a car driver) that the battery pack should be checked or serviced. Additionally or alternatively, the battery pack controller 230 may automatically shut down the battery pack when a sharp increase in contact point resistance is detected during charging or discharging to protect the battery cells/battery pack from damage. Because the battery pack controller 230 is able to identify where degraded contact points are located, the user or technician can make corrections very quickly and accurately. For example, loose bolts may be tightened, or corroded joints may be replaced, before the battery catastrophically degrades.

Large-sized battery packs are generally composed of a number of battery modules (battery modules). The communication wires between the battery modules may be very long (up to several meters) and there is typically a transformer across the communication wires. These transformers help suppress external interference of these communication wires. Fig. 6 is a block diagram of a battery pack having a plurality of battery modules, and referring to fig. 6, the battery pack 600 illustratively includes a battery module M and a battery module M +1 (M is a positive integer), which are denoted by

reference numerals

620 and 640, respectively. Each

battery module

620 or 640 may include one or

more battery cells

621, 622 or 641, 642. Each cell may have a monitor 624 or 644. The details of these

battery units

621, 622 or 641, 642 and their

monitors

623, 624 or 643, 644 have been described in detail in the previous embodiments and will not be further described here. Both ends of the communication wire 626 between the

battery modules

620 and 640 are provided with transformers to suppress interference. However, the transformer not only suppresses interference but also blocks a dc voltage on the power connection line 630 between the battery modules. To this end, the present application incorporates a path in the isolation circuit that is capable of conducting a dc voltage.

Fig. 7 is a block diagram of a battery pack having an isolation circuit according to an embodiment of the present invention. Referring to fig. 7, the same reference numerals as in fig. 6 are used for convenience. The battery pack 600 illustratively includes a battery module M and a battery module M +1 (M is a positive integer), which are labeled with

reference numerals

620 and 640, respectively. It is understood that the illustrated battery modules may be only a portion of the battery pack 600. Each

battery module

620 or 640 may include one or

more battery cells

621, 622 or 641, 642. Each cell may have a

monitor

623, 624 or 643, 644. The details of these

battery units

621, 622 or 641, 642 and their

monitors

623, 624 or 643, 644 have been described in detail in the previous embodiments and will not be further described here. In the example of fig. 7, taking battery module 620 as an example, it includes a first battery cell 641 and a second battery cell 642. Within each battery module, the individual battery cells are also coupled to one another by power connection lines. For example, in battery module 620, power connection line 628 couples a first electrode (shown as a positive electrode) of first cell 641 to a second electrode (shown as a negative electrode) of second cell 642. The respective battery modules, such as

battery modules

620 and 640, are coupled to each other by power connection lines 630.

Isolation circuits are arranged between each battery module and are used for coupling communication wires of the adjacent battery modules. For example, a first isolation circuit 625 is coupled to one end of battery module 620, i.e., battery cell 622. The first isolation circuit 625 includes a first transformer T1, a first resistor R1, and a second resistor R2. Both ends of the first side of the first transformer T1 are coupled to the battery module 620, more specifically, the end battery cells 622. The first resistor R1 and the second resistor R2 are connected in series between two ends of the second side of the transformer T2. The junction of the first resistor R1 and the second resistor R2 is coupled to the monitor 624 of the battery cell 622. In addition, a second isolation circuit 627 is connected to one end of the battery module 640, i.e., the battery cell 641. The second isolation circuit 625 may include a second transformer T1, a third resistor R3, and a fourth resistor R4. Both ends of the first side of the second transformer T2 are coupled to the battery module 640, more specifically, the end cell 641. The second side of the second transformer T2 is connected to the second side of the first transformer T2. The third resistor R3 and the fourth resistor R4 are connected in series between two ends of the second side of the second transformer T2, and a connection point of the third resistor R3 and the fourth resistor R4 is connected to a second electrode (negative electrode in the figure) of one of the battery cells 641 of the battery module 640 via a voltage conductor.

Monitor 624 is connected to a voltage input of first capacitor C1 for input to voltage difference detector 312 (e.g., fig. 3A or 3B) instead of the previous input through the communication conductor. In this example, the voltage transfer of adjacent cells of adjacent battery modules is transmitted through the path of the power connection 630, the resistors R3 and R4, the communication conductor 626, the resistors R1, R2, and the voltage conductor. Monitor 624 introduces voltage through the extra pins and voltage conductors rather than through communication conductor 626 in order to avoid common mode interference from the latter. Common mode interference is present in the pin of the monitor 624 to which the first transformer T1 is connected. This connection may increase susceptibility to communication interference.

As shown in fig. 7, the first isolation circuit 625 may further include a first capacitor C1, one end of the first capacitor C1 is connected between the first resistor R1 and the second resistor R2, and the other end of the first capacitor C1 is connected to a first electrode (positive electrode in the figure) of one of the battery cells 622 of the battery module 620. The first capacitor C1 provides isolation of the voltage input from the power supply terminals of the monitor 624.

In an embodiment, the first isolation circuit 625 may further include a second capacitor C2 and a third capacitor C3, and both ends of the first side of the first transformer T1 are coupled to the battery module 620, more specifically, the battery cells 624 at the ends thereof, through the second capacitor C2 and the third capacitor C3, respectively. The second capacitor C2 and the third capacitor C3 provide further isolation of interfering signals.

In an embodiment, the second isolation circuit 627 further includes a fourth capacitor C4 and a fifth capacitor C5, and two ends of the first side of the second transformer T2 are coupled to the battery module 640, more specifically, the battery cell 641 at an end thereof, through the fourth capacitor C4 and the fifth capacitor C5, respectively.

In one embodiment, the first isolation circuit 625 may be physically part of the battery module 620 and the second isolation circuit 627 may be physically part of the battery module 640. In another embodiment, the first and

second isolation circuits

625 and 627 may be integrated into one connection assembly for connecting adjacent battery modules.

The embodiments described above provide various advantages. Degradation of the contact points (such as corrosion or loosening) can be detected by the cell monitor. By simply monitoring the voltage difference between the power connection lines and the corresponding communication conductor, an increase in contact point resistance can be detected for each individual power connection line in the battery pack. All the required additional circuitry can be easily integrated into the cell monitor. Such detection is beneficial for improving the performance of the battery pack, extending battery life between recharges, and avoiding potential damage to the battery pack. Additionally, contact point detection can be combined with other measurements (such as voltage, temperature, pressure, etc.) without the addition of external components or wiring. Also, the embodiments can transfer a direct current voltage between the battery modules isolated from each other, thereby being suitable for a large-sized battery pack including a plurality of battery modules.

It is believed that aspects of the present invention are applicable to a variety of different types of devices, systems and apparatuses involving batteries and/or battery control, including those involving automotive applications. While the invention is not necessarily so limited, various aspects of the invention may be appreciated through an example discussion using this context.

Although the present invention has been described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A battery pack, comprising:

at least a first battery module and a second battery module, each battery module comprising:

at least a first battery cell and a second battery cell;

a power connection line for coupling a first electrode of the first battery cell to a second electrode of the second battery cell; wherein the first battery cell comprises a monitor;

a first isolation circuit coupled to the first battery module, the first isolation circuit including a first transformer, a first resistor, and a second resistor, both ends of a first side of the first transformer being coupled to the first battery module, the first resistor and the second resistor being connected in series between both ends of a second side of the transformer, a connection point of the first resistor and the second resistor being connected to a monitor of one of the battery cells of the first battery module via a voltage wire;

a second isolation circuit coupled to the second battery module, wherein the second isolation circuit includes a second transformer, a third resistor and a fourth resistor, two ends of a first side of the second transformer are coupled to the second battery module, a second side of the second transformer is connected to a second side of the first transformer, the third resistor and the fourth resistor are connected in series between two ends of the second side of the second transformer, and a connection point of the third resistor and the fourth resistor is connected to a second electrode of one battery cell of the second battery module;

wherein the monitor comprises:

a transmitter and receiver in signal communication with the second battery cell via a communication conductor; and

a voltage difference detector coupled to the power connection line and the communication conductor for detecting a voltage difference between the power connection line and the communication conductor, wherein the monitor indicates degradation of a contact point of the power connection line if the detected voltage difference is outside a predetermined threshold range.

2. The battery pack of claim 1, wherein the first isolation circuit further comprises a first capacitor, one end of the first capacitor is connected to a connection point between the first resistor and the second resistor, and the other end of the first capacitor is connected to the first electrode of one of the battery cells of the first battery module.

3. The battery pack of claim 1, wherein the first isolation circuit further comprises a second capacitor and a third capacitor, and wherein two ends of the first side of the first transformer are coupled to the first battery module through the second capacitor and the third capacitor, respectively.

4. The battery pack of claim 1, wherein the first isolation circuit further comprises a fourth capacitor and a fifth capacitor, and wherein two ends of the first side of the second transformer are coupled to the second battery module through the fourth capacitor and the fifth capacitor, respectively.

5. The battery pack of claim 1, wherein the voltage difference detector is configured to detect the voltage difference when the transmitter and receiver are receiving signal communications via the communication conductor.

6. The battery pack of claim 1, wherein the signal communication via the communication conductor occurs in a current domain or a voltage domain, and the voltage difference detector detects a DC voltage difference between the power connection line and the communication conductor.

7. The battery of claim 1, wherein the contact degradation comprises at least one of contact corrosion or contact loosening.

8. The battery pack of claim 1, wherein:

the monitor is integrated within the first cell, wherein the voltage difference detector is coupled to a first electrode of the first cell; or

The monitor is external to the first battery cell, wherein the voltage difference detector is coupled to the power connection line.

9. A battery module, comprising:

at least a first battery cell and a second battery cell;

the isolation circuit comprises a transformer, a first capacitor, a first resistor and a second resistor, wherein two ends of a first side of the transformer are coupled to the first battery unit, a second side of the transformer is suitable for being connected with another battery module, the first resistor and the second resistor are connected between two ends of the second side of the transformer in series, and a connection point of the first resistor and the second resistor is connected to a monitor of the first battery unit through a voltage lead;

wherein the monitor comprises: