BACKGROUND

[0001] This disclosure relates generally to the field of battery management, and more particularly to battery management systems.

[0002] Batteries are used in many applications to provide energy to loads. A typical conventional battery usually consists of multiple cells connected in series to form a battery module. Cells are used cumulatively in the battery to provide a desired output voltage. Depending upon the power requirements and available internal spaces of the loads, multiple batteries are sometimes used.

[0003] However, conventional battery deployments have some operating disadvantages. For example, the current drawn from the batteries may exceed the battery's designed current limit, and over-discharging of the battery is caused, which would no doubt reduce operation lifetime of the battery.

[0004] Therefore, in the view of the foregoing, it is desirable to provide an improved battery management system to solve at least one of problems above-mentioned.

BRIEF DESCRIPTION

[0005] In one aspect of embodiments of the present disclosure, a battery management system is provided. The battery management system comprises a battery module having a positive output terminal and a negative output terminal. The battery module comprises at least two branch circuits which are connected in parallel between the positive output terminal and the negative output terminal. Each of the at least two branch circuits comprises at least two battery cells which are connected in series between the positive output terminal and the negative output terminal. Each battery cell comprises a battery, a current limitingdevice for preventing the battery from over-discharging, and a bypass device for bypassing the battery when a fault occurs in the battery. [0006] In another aspect of embodiments of the present disclosure, a battery management system is provided. The battery management system comprises a plurality of battery cells. Each of the plurality of battery cells comprises a battery, a current limiting device for preventing the battery from over-discharging, and a bypass device for bypassing the battery when a fault occurs in the battery.

DRAWINGS

[0007] These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

[0008] FIG. 1 is a schematic diagram of a battery management system in accordance with an embodiment of the present disclosure; and

[0009] FIG. 2 is a schematic diagram of a battery management system in accordance with another embodiment of the present disclosure.

DETAILED DESCRIPTION

[0010] Embodiments of the present disclosure will be described hereinbelow with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the disclosure in unnecessary detail.

[0011] Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terms "first", "second", and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Also, the terms "a" and "an" do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. The term "or" is meant to be inclusive and mean either or all of the listed items. The use of "including," "comprising" or "having" and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms "connected" and "coupled" are not restricted to physical or mechanical connections or couplings, and can include electrical connections or couplings, whether direct or indirect. In addition, Terms indicating specific locations, such as "top", "bottom", "left", and "right", are descriptions with reference to specific accompanying drawings. Embodiments disclosed in the present disclosure may be placed in a manner different from that shown in the figures. Therefore, the location terms used herein should not be limited to locations described in specific embodiments.

[0012] FIG. 1 illustrates a schematic diagram of a battery management system 100 in accordance with an embodiment of the present disclosure. As shown in FIG. 1, the battery management system 100 in accordance with an embodiment of the present disclosure may include a battery module 1. The battery module 1 has a positive output terminal "+" and a negative output terminal

[0013] In one implementation, the battery module 1 may include at least two branch circuits 1 1. The at least two branch circuits 11 are connected in parallel between the positive output terminal "+" and the negative output terminal The seven branch circuits 1 1 are shown as an illustrative example in FIG. 1.

[0014] Each of the at least two branch circuits 1 1 may include at least two battery cells 12. The at least two battery cells 12 are connected in series between the positive output terminal "+" and the negative output terminal In this embodiment, the number of the battery cells 12 in each branch circuit 11 are shown to be two in FIG. 1, but the number of the battery cells 12 of the present disclosure should be not limited herein.

[0015] Each battery cell 12 includes a battery 13, a current limiting device 14 and a bypass device. The current limiting device 14 can prevent the battery 13 from over- discharging. For example, the current limiting device 14 may include a fuse 14 connected in series with the battery 13. The bypass device can bypass the battery 13 when the battery 13 is in a fault condition. The bypass device may for example include a first diode Di. The first diode Di is connected in parallel with the fuse 14 and the battery 13. For example, when one battery 13 gets open-circuit failures, the impedance of open-circuit battery 13 becomes quite large. In this condition, the first diode Di is triggered to bypass the open- circuit battery 13. The current will flow through the first diode Di and the open-circuit battery 13 is bypassed. Each battery cell 12 may further include a first resistor Ri. The first resistor Ri is connected in parallel with the fuse 14 and the battery 13 and is configured for cell voltage balancing.

[0016] The current limiting device including the fuse 14 and the bypass device including the first diode Di can guarantee the continuity and redundancy of battery operation under different fault conditions of the battery 13. The first resistor Ri can ensure voltage balancing for the battery cells 12 connected in series.

[0017] In addition, each branch circuit 11 may further include a second diode D ₂ . In each branch circuit 11, the second diode D ₂ is connected in series with the at least two battery cells 12. The second diode D ₂ can prevent reverse connection of the corresponding branch circuit 11.

[0018] With continued reference to FIG. 1, in another implementation, the battery module 1 of the battery management system 100 may include a plurality of battery cells 12. Each of the plurality of battery cells 12 includes a battery 13, a current limiting device 14 for preventing the battery 13 from over-discharging, and a bypass device for bypassing the battery 13 when a fault occurs in the battery 13. The current limiting device 14 may for example include a fuse 14 connected in series with the battery 13. The bypass device may for example include a first diode Di connected in parallel with the fuse 14 and the battery 13.

[0019] The plurality of battery cells 12 comprises at least two battery cells 12 which are connected in parallel and at least two battery cells 12 which are connected in series.

[0020] Each battery cell 12 may further include a first resistor Ri. The first resistor Ri is connected in parallel with the fuse 14 and the battery 13. The first resistor Ri of each battery cells 12 can ensure voltage balancing for the at least two battery cells 12 which are connected in series.

[0021] The battery management system 100 may further include at least two second diodes D ₂ for preventing reverse connection of the at least two battery cells 12 which are connected in parallel.

[0022] FIG. 2 illustrates a schematic diagram of a battery management system 200 in accordance with another embodiment of the present disclosure. As shown in FIG. 2, the battery management system 200 in accordance with another embodiment of the present disclosure may include the battery module 1 as shown in FIG.1, and may further include a self-driven matching circuit 2. The battery module 1 is coupled to a discharge circuit 3 via the self-driven matching circuit 2. The discharge circuit 3 is for example a boost converter in this embodiment. However, the discharge circuit 3 should be not limited to the boost converter, and may also include a buck converter, a buck-boost converter and other converters. The self-driven matching circuit 2 may be used for over-discharging control of the battery module 1. When the battery module 1 is in a normal operation, a discharge current from the battery module 1 flows through the self-driven matching circuit 2 to the discharge circuit 3, and when the battery module 1 is in an over-discharging condition, the self-driven matching circuit 2 is open circuit and no current flows through the self-driven matching circuit 2 from the battery module 1.

[0023] The self-driven matching circuit 2 may include a second resistor R ₂ , a third resistor R ₃ , a fourth resistor R ₄ , a first transistor Qi and a second transistor Q ₂ . The second resistor R ₂ and the third resistor R ₃ are connected in series between the positive output terminal "+" and the negative output terminal The first transistor Qi is a PN type transistor and has a body diode D ₃ . For example, the first transistor Qi is a N-channel Metal-Oxide-Semiconductor Field-Effect Transistor (simply called as MOS). A gate electrode g of the first transistor Qi is connected with a connection point of the second resistor R ₂ and the third resistor R ₃ . A source electrode s of the first transistor Qi is connected to the negative output terminal and the source electrode s of the first transistor Qi is grounded. The fourth resistor R ₄ is coupled between the positive output terminal "+" and a drain electrode d of the first transistor Qi. The second transistor Q2 is a P P type transistor and has a body diode D ₄ . For example, the second transistor Q2 is a P-channel Metal-Oxide-Semiconductor Field-Effect Transistor (simply called as PMOS). A gate electrode g of the second transistor Q2 is connected with the drain electrode d of the first transistor Qi, a source electrode s of the second transistor Q2 is connected with the positive output terminal "+" and a drain electrode d of the second transistor Q2 is connected to the discharge circuit 3. The types of the first transistor Qi and the second transistor Q2 should be not limited herein. In another embodiment, the first transistor Qi and the second transistor Q2 can be both silicon type, gallium nitride or silicon carbide type N-channel Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) and P-channel Metal- Oxide- Semi conductor Field-Effect Transistor (MOSFET).

[0024] Hereinafter, how the self-driven matching circuit 2 of the present disclosure realizes the over-discharging protection for the battery module 1 will be explained in detail in combination with FIG. 2.

[0025] With continued reference to FIG. 2, the first transistor Qi is MOS and the second transistor Q2 is PMOS, the second resistor R2 and the third resistor R3 make up a voltage divider. When a voltage provided by the battery module 1 (called as a battery voltage VIN) drops, the voltage at point Ai, i.e. a gate voltage VGI of the first transistor Qi, will reduce. With further reduction of the battery voltage VIN, when the gate voltage VGI of the first transistor Qi will drop to be less than a threshold voltage VGS(th)i of the first transistor Qj, the first transistor is turned off. The voltage at point A2, i.e. a gate voltage VG2 of the second transistor Q2 will increase step by step through the fourth resistor R ₄ . When a voltage difference between the gate voltage VG2 of the second transistor Q2 and the battery voltage VIN is larger than a threshold voltage VGS(th)2 of the second transistor Q2, that is, (VG2- VIN) > VGS(th)2, the second transistor Q2 is turned off.

[0026] Thus, when the battery voltage VIN is under a protect voltage VUCP of the battery module 1 , both the first transistor Qi and the second transistor Q2 are turned off. The battery module 1 is disconnected from the boost converter 3. The battery module 1 can't output the battery voltage VIN. [0027] Therefore, the self-driven matching circuit 2 can prevent the battery 13 from over current discharging or provide under voltage protection. By selecting proper control parameters, the battery 13 can work in a health and durable condition.

[0028] The current limiting device 14 including the fuse and the self-driven matching circuit 2 of the present disclosure can realize an effective over-discharging protection for the battery module 1.

[0029] The battery management system 100, 200 can use a robust mechanical package, and such the robust mechanical package design can allow the battery management system 100, 200 to survive in a harsh environment like high temperature, high pressure and high vibration.

[0030] The battery management system 100, 200 of the present disclosure enables an effective, robust and long lifetime operation of the battery 13, particularly in the harsh environments. The battery management system 100, 200 of the present disclosure can have high efficiency, robust structure, simple circuit, low power consumption, and compact size.

[0031] While the disclosure has been illustrated and described in typical embodiments, it is not intended to be limited to the details shown, since various modifications and substitutions can be made without departing in any way from the spirit of the present disclosure. As such, further modifications and equivalents of the disclosure herein disclosed may occur to persons skilled in the art using no more than routine experimentation, and all such modifications and equivalents are believed to be within the spirit and scope of the disclosure as defined by the following claims.