Backup battery system

Abstract

This invention discloses a backup battery system comprising multiple battery packs. Each battery pack includes a battery module, a pre-charge branch, a main charging branch, a control unit, a positive output terminal, and a negative output terminal. The battery module includes a positive terminal, a negative terminal, and multiple individual battery cells. The on-resistance of the pre-charge branch is greater than that of the main charging branch. The control unit controls the main charging branch and the pre-charge branch to be closed when its corresponding battery pack is charging. It also detects a first voltage between the positive and negative output terminals of its corresponding battery pack, and detects a second voltage of each individual battery cell in its corresponding battery pack. When the first voltage reaches a preset first voltage or the second voltage reaches a preset second voltage, the control unit controls the main charging branch to be open. This invention aims to improve the problem of frequent alarms and protection shutdowns caused by misjudgments, and enhances the compatibility and stability of the backup battery system.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a backup battery system. Background Technology

[0002] With the rapid development of energy storage technology, lithium batteries (such as lithium iron phosphate batteries) are gradually replacing traditional lead-acid batteries in uninterruptible power supply (UPS) systems due to their high energy density, long cycle life, and environmental friendliness. However, most existing UPS systems are designed and optimized for the electrochemical characteristics of lead-acid batteries. When lithium battery packs are directly connected to the system, compatibility issues arise because of the fundamental differences between lead-acid and lithium iron phosphate batteries in their charge / discharge voltage platforms and internal resistance characteristics. For example, with a 96V voltage platform, the float charge voltage platform of lead-acid batteries is typically higher (around 106V), and the equalization charge voltage can even reach 116V; while the full charge voltage of lithium iron phosphate batteries is typically only around 108V. When the UPS uses the original lead-acid battery charging strategy to charge the lithium battery pack, as the battery voltage rises to its protection threshold, the battery management system (BMS) will trigger a protection mechanism to instantly cut off the charging circuit to prevent overcharging. Such instantaneous current surges can cause UPS systems to detect abnormal increases in bus voltage or current interruptions, misinterpreting them as system faults, thus generating alarms or causing direct shutdowns, leading to significant concerns and safety hazards for users. Summary of the Invention

[0003] The main objective of this invention is to propose a backup battery system that aims to improve the problem of frequent alarms and protection shutdowns caused by misjudgments, thereby enhancing the compatibility and stability of the backup battery system.

[0004] To achieve the above objectives, the present invention proposes a backup battery system, the backup battery system comprising: Multiple battery packs, wherein the multiple battery packs are connected in series; The battery pack includes a battery module, a pre-charge branch, a main charging branch, a control unit, a positive output terminal, and a negative output terminal; The battery module includes a positive terminal, a negative terminal, and multiple individual battery cells, each of which is a lithium iron phosphate battery cell. The pre-charge branch is located between the negative terminal and the negative output terminal. The pre-charge branch is connected in parallel with the main charging branch. The on-resistance of the pre-charge branch is greater than that of the main charging branch. The positive terminal is electrically connected to the positive output terminal. Both the positive and negative output terminals are used to connect to a load. The control unit is used to control the main charging branch and the pre-charging branch to be in a closed state when the corresponding battery pack is in a charging state. It is also used to detect the first voltage between the positive output terminal and the negative output terminal in the battery pack corresponding to itself, and to detect the second voltage of each individual cell in the battery pack corresponding to itself; and to control the main charging branch to be in a disconnected state when the first voltage reaches a preset first voltage or the second voltage reaches a preset second voltage.

[0005] In one embodiment, the control unit is further configured to control the pre-charge branch to be in an open state when the first voltage reaches a preset third voltage or the second voltage reaches a preset fourth voltage, wherein the preset third voltage is greater than the preset first voltage and the preset fourth voltage is greater than the preset second voltage.

[0006] In one embodiment, the battery pack further includes a DC miniature circuit breaker, which includes a first trip unit, a first magnetic trip system, a first main contact, a main mechanism, a second main contact, a second magnetic trip system, and a second trip unit connected in series. The first trip unit is electrically connected to the positive terminal, the first main contact is electrically connected to the positive output terminal, the second trip unit is electrically connected to the main charging branch, and the second main contact is electrically connected to the negative output terminal. The main mechanism is used to control the first main contact and the second main contact to disconnect when the first voltage reaches a preset first voltage or the second voltage reaches a preset second voltage and the main charging branch is in a fault state; and to control the first main contact and the second main contact to disconnect when the first voltage reaches a preset third voltage or the second voltage reaches a preset fourth voltage and the pre-charge branch is in a fault state. It is also used to control the closure of the first main contact and the second main contact when the battery pack is in a charging or discharging state.

[0007] In one embodiment, the control unit is further configured to control the first trip unit and the second trip unit to operate when the first voltage is less than a preset discharge voltage and the first voltage is less than a preset operating voltage, so that the main mechanism controls the first main contact and the second main contact to disconnect; Alternatively, the control unit is further configured to control the first trip unit and the second trip unit to operate when the battery pack is in a non-working state for a preset resting time, so that the main mechanism controls the first main contact and the second main contact to disconnect. The battery pack's operating states include charging, discharging, and non-operating states.

[0008] In one embodiment, the first trip unit is a shunt trip coil, and the second trip unit is a shunt trip coil.

[0009] In one embodiment, the battery pack further includes: An overcurrent protection circuit is provided between the positive terminal and the positive output terminal. The overcurrent protection circuit is used to disconnect the electrical connection between the positive terminal and the positive output terminal when the current in the branch it is in reaches a preset current threshold.

[0010] In one embodiment, the overcurrent protection circuit includes a three-terminal fuse.

[0011] In one embodiment, the discharge rate of the single battery cell is not less than 3C, and the capacity of the single battery cell is 20Ah.

[0012] In one embodiment, the control units of each battery pack are communicatively connected, with the control unit in one battery pack being the master controller and the control units in the other battery packs being slave controllers. The main controller is used to receive battery pack data uploaded by each of the slave controllers; Furthermore, when it is determined, based on the battery pack data of each battery pack, that the first voltage corresponding to any of the battery packs reaches a preset first voltage or the second voltage corresponding to any of the battery packs reaches a preset second voltage, a cut-off control command is output to each of the slave controllers, so that the slave controller controls its corresponding main charging branch to be in a disconnected state.

[0013] In one embodiment, the positive output terminal and / or the negative output terminal include two power connection ports connected in parallel, the power connection ports being used to connect to electrical equipment or charging equipment.

[0014] In practical applications, a "high internal resistance" state is created by using a pre-charge resistor. When fully charged, the main charging branch is disconnected, leaving only the pre-charge branch (pre-charge resistor) operational. Utilizing the current-limiting and voltage-dividing characteristics of the pre-charge resistor, the "high internal resistance, high voltage" float charging characteristics of lead-acid batteries are simulated. This prevents the lithium battery pack from being misjudged as "undervoltage" or "open circuit" by the UPS due to a low voltage platform after full charging, effectively improving the problem of frequent UPS alarms and protection shutdowns caused by misjudgments, and enhancing the compatibility and stability of the backup battery system. Furthermore, compared to traditional pre-charge schemes, this application simultaneously closes the main charging branch and the pre-charge branch at the initial charging stage. Current preferentially flows through the main circuit for high-current charging and discharging, eliminating the "pre-charge delay" stage of waiting for bus voltage balance, shortening system startup time, and improving the response speed and component lifespan of the backup battery system. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of a module of an embodiment of the backup battery system of the present invention; Figure 2 This is a schematic diagram of a module of another embodiment of the backup battery system of the present invention; Figure 3 This is a schematic diagram of another embodiment of the backup battery system of the present invention; Figure 4 This is a detailed circuit diagram of an embodiment of the backup battery system of the present invention; Figure 5 This is a schematic diagram of the electrical connections of an embodiment of the backup battery system of the present invention; Figure 6 This is an electrical connection diagram of another embodiment of the backup battery system of the present invention.

[0017] Explanation of icon numbers: 10. Battery module; 20. Precharge branch; 30. Main charging branch; 40. Control unit; 50. DC miniature circuit breaker; 60. Overcurrent protection circuit.

[0018] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] With the rapid development of energy storage technology, lithium batteries (such as lithium iron phosphate batteries) are gradually replacing traditional lead-acid batteries in uninterruptible power supply (UPS) systems due to their high energy density, long cycle life, and environmental friendliness. However, most existing UPS systems are designed and optimized for the electrochemical characteristics of lead-acid batteries. When lithium battery packs are directly connected to the system, compatibility issues arise because of the fundamental differences between lead-acid and lithium iron phosphate batteries in their charge / discharge voltage platforms and internal resistance characteristics. For example, with a 96V voltage platform, the float charge voltage platform of lead-acid batteries is typically higher (around 106V), and the equalization charge voltage can even reach 116V; while the full charge voltage of lithium iron phosphate batteries is typically only around 108V. When the UPS uses the original lead-acid battery charging strategy to charge the lithium battery pack, as the battery voltage rises to its protection threshold, the battery management system (BMS) will trigger a protection mechanism to instantly cut off the charging circuit to prevent overcharging. Such instantaneous current surges can cause UPS systems to detect abnormal increases in bus voltage or current interruptions, misinterpreting them as system faults, thus generating alarms or causing direct shutdowns, leading to significant concerns and safety hazards for users.

[0021] Therefore, refer to Figure 1 This invention proposes a backup battery system, the backup battery system comprising: Multiple battery packs, wherein the multiple battery packs are connected in series; The battery pack includes a battery module, a pre-charge branch, a main charging branch, a control unit, a positive output terminal, and a negative output terminal; The battery module includes a positive terminal, a negative terminal, and multiple individual battery cells, each of which is a lithium iron phosphate battery cell. The pre-charge branch is located between the negative terminal and the negative output terminal. The pre-charge branch is connected in parallel with the main charging branch. The pre-charge branch includes at least a pre-charge resistor. The positive terminal is electrically connected to the positive output terminal. Both the positive and negative output terminals are used to connect to a load. The control unit is used to control the main charging branch and the pre-charging branch to be in a closed state when the corresponding battery pack is in a charging state. It is also used to detect the first voltage between the positive output terminal and the negative output terminal in the battery pack corresponding to itself, and to detect the second voltage of each individual cell in the battery pack corresponding to itself; and to control the main charging branch to be in a disconnected state when the first voltage reaches a preset first voltage or the second voltage reaches a preset second voltage.

[0022] In this embodiment, the control unit can be implemented using a main controller, such as an MCU, DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), PLC, or SOC (System-on-Chip). The main charging branch can be implemented using switching devices such as relays or contactors, or switching transistors such as MOSFETs or IGBTs. The pre-charging branch can be implemented using a pre-charging resistor and the aforementioned switching devices, or a pre-charging resistor and the aforementioned switching transistors. Thus, the presence of the pre-charging resistor makes the on-resistance of the pre-charging branch greater than that of the main charging branch.

[0023] In this embodiment, the positive output terminal (P+) collects the positive voltages of all battery cells and can be connected to the positive DC bus of the UPS. It provides DC voltage to the UPS or receives charging voltage from the UPS. The negative output terminal (P-) can be connected to the return terminal of an external circuit, which is connected to the negative DC bus of the UPS. When the battery pack is charging, current flows from the UPS into the battery module. When the battery pack is discharging, current flows from the battery module into the UPS.

[0024] In this embodiment, the first voltage (total voltage threshold) refers to the total voltage between the positive and negative output terminals of the battery pack. When the total voltage of the entire PACK reaches the preset first voltage (e.g., 105V), it indicates that the battery module is nearly fully charged (for a 96V system, 105V is usually the charging limit voltage). This prevents the total voltage from being too high due to individual cell voltage sampling errors or communication delays, thus directly triggering the UPS overvoltage protection (OVP). The second voltage (individual cell voltage threshold) refers to the voltage of each individual cell within the battery pack. It is understood that although the nominal voltage of lithium iron phosphate is 3.2V, and the fully charged voltage is usually around 3.65V, to ensure long cycle life and safety, a protection value slightly lower than the physical limit is usually set, i.e., the preset second voltage (set to 3.6V here). This prevents any single cell from overcharging. If any cell reaches 3.6V, the system must disconnect the main charging circuit to protect the cell from damage. The preset first and second voltages are set by the developers and stored in advance in the internal or external memory of the control unit.

[0025] In this embodiment, during the normal charging phase, i.e., when the battery pack is charging, the battery pack voltage is low. The control unit keeps both the main charging branch and the pre-charging branch closed. Because the main charging branch is closed, the on-resistance of the pre-charging branch is greater than that of the main charging branch, so almost all the current flows through the main circuit (where the resistance is extremely small), and the pre-charging resistor is short-circuited, allowing the system to charge rapidly with a large current. When the control unit detects that the first voltage reaches a preset first voltage (e.g., 105V) or the second voltage reaches a preset second voltage (e.g., 3.6V), it controls the main charging branch to open while keeping the pre-charging branch closed. At this time, the main circuit is cut off, and the large current cannot flow, leaving only the pre-charging resistor (e.g., 10Ω) connected in series in the charging circuit. Due to the presence of the pre-charging resistor, the current is forced to flow through this resistor. According to Ohm's law, the resistor shares a portion of the voltage; at the same time, the resistor limits the current. For the UPS, it is still outputting voltage, and the current does not instantly drop to zero (it just becomes very small), so no "open circuit" or "disconnected circuit" fault is detected. For a battery, the battery pack terminal voltage (i.e., the first voltage) is equal to the sum of the battery cell voltage (the voltage between the positive terminal B+ and the negative terminal B-) and the voltage drop across the resistor. This allows the output voltage of the battery pack to be "pulled up" to near the charging voltage of the UPS, simulating the "high internal resistance, high voltage" characteristics of lead-acid batteries at the end of charging.

[0026] In this embodiment, compared to the traditional approach of first closing the pre-charge circuit, waiting for the voltage difference to decrease, and then closing the main circuit and disconnecting the pre-charge circuit, this process, although only a few hundred milliseconds, requires optimization in scenarios with extremely high response speed requirements. This application directly and simultaneously closes the main charging branch and the pre-charge branch upon system startup, eliminating intermediate waiting and judgment steps, achieving "full power upon power-on" and a faster response. The main charging branch is only disconnected when a protection threshold is reached (either the first voltage reaches a preset first voltage or the second voltage reaches a preset second voltage), making the control logic easier to implement and reducing the risk of software failures due to complex logic judgments.

[0027] It should be noted that when the battery pack is discharging, the discharge current mainly flows through the charging MOS (main circuit) with extremely low resistance. That is, when both the main charging branch and the pre-charge branch are closed, the current will choose the path with relatively low resistance (i.e., the main charging branch), resulting in less heat generation and efficient battery power supply to the UPS. If the main charging branch is disconnected for some reason (such as misjudgment or interference), and the pre-charge branch is also disconnected at the same time, the battery circuit will be completely broken, and the UPS will instantly shut down. Therefore, this application keeps the pre-charge branch closed even in the discharging state, which is equivalent to leaving a "backup channel" for the system. In the event of a fault disconnection of the main charging branch, the current can still maintain power supply for a few seconds through the pre-charge resistor (although the voltage will drop), giving the control unit time to execute the shutdown action, rather than an instantaneous power outage.

[0028] In practical applications, a "high internal resistance" state is created by using a pre-charge resistor. When fully charged, the main charging branch is disconnected, leaving only the pre-charge branch (pre-charge resistor) operational. Utilizing the current-limiting and voltage-dividing characteristics of the pre-charge resistor, the "high internal resistance, high voltage" float charging characteristics of lead-acid batteries are simulated. This prevents the lithium battery pack from being misjudged as "undervoltage" or "open circuit" by the UPS due to a low voltage platform after full charging, effectively improving the problem of frequent UPS alarms and protection shutdowns caused by misjudgments, and enhancing the compatibility and stability of the backup battery system. Furthermore, compared to traditional pre-charge schemes, this application simultaneously closes the main charging branch and the pre-charge branch at the initial charging stage. Current preferentially flows through the main circuit for high-current charging and discharging, eliminating the "pre-charge delay" stage of waiting for bus voltage balance, shortening system startup time, and improving the response speed and component lifespan of the backup battery system.

[0029] In another embodiment, the control unit is further configured to control the precharge branch to be in an open state when the first voltage reaches a preset third voltage or the second voltage reaches a preset fourth voltage, wherein the preset third voltage is greater than the preset first voltage and the preset fourth voltage is greater than the preset second voltage.

[0030] In this embodiment, the main charging branch includes a first switching transistor, and the pre-charging branch includes a second switching transistor and a pre-charging resistor. The preset third and fourth voltages can both be set by the developers and stored in advance in the control unit's internal or external memory. (Reference) Figure 4 Taking an example where both the first and second switching transistors are MOSFETs, where ChargeMOS is the first switching transistor, PreChaMOS is the second switching transistor, and PreChaR is the pre-charge resistor. Assume the preset first voltage is 105V, the preset second voltage is 3.6V, the preset third voltage is 110V, and the preset fourth voltage is 3.65V.

[0031] Based on the above embodiments, when the battery pack is charging, the control unit closes the main charging branch (Charge MOS) and the pre-charging branch (PreCha MOS). At this time, the battery module is in a low-charge state, and a large current is used to quickly charge the battery module through the main circuit. As the charging process progresses, the control unit continuously monitors the cell voltage (second voltage) and the battery pack voltage (first voltage). Assume that the second voltage of a certain cell rises to 3.60V (reaching the preset second voltage). At this time, the control unit immediately executes a protection action, controlling the main charging branch to disconnect, controlling the Charge MOS to turn off, cutting off the high-current input channel, and initiating the equalization process. At this time, the PreCha MOS of the pre-charging branch remains on, and the system enters a "trickle-down charging" or "voltage maintenance" state to prevent a sudden voltage drop from causing load power loss. After the main charging branch is disconnected, the control unit continues to monitor the voltage in real time. Assume that the control unit detects that the second voltage of a single cell continues to rise to 3.65V (reaching the preset fourth voltage), or the total battery pack voltage (first voltage) reaches the preset third voltage. At this point, the control unit controls the pre-charge branch to disconnect, that is, controls the PreCha MOS to turn off, thereby terminating the charging process.

[0032] It's important to note that in the current 5-40KVA low-power UPS market, there's a lack of unified standards for DC bus voltage, resulting in a highly fragmented market. Common DC voltage platforms include 96V, 192V, ±96V, ±192V, 384V, and 512V. This diversity leads to significant "adaptation barriers": traditional battery pack designs require independent customization of battery series / parallel connections and BMS parameter settings for each voltage platform. This not only causes a dramatic increase in product SKUs (stock keeping units), raising R&D and production costs, but also poses significant challenges to customer inventory management, logistics, and on-site installation and commissioning, hindering the large-scale promotion of standardized products.

[0033] Therefore, this application proposes a backup battery system comprising multiple battery packs, which can be connected in series or parallel. For example, a single battery pack can be designed for a 96V voltage platform, integrating protection, control, sampling, and communication functions, and can be used independently. Figure 5 and Figure 6 As shown, series and parallel electrical connections can also be made to form standard voltage platform solutions of 96V cascade, 192V, ±96V, ±192V, 384V, and 512V. At the same time, the series voltage platforms can be connected in parallel again to form a high-capacity system to ensure the needs of long-term backup power applications.

[0034] Optionally, the discharge rate of the single cell is not less than 3C, and the capacity of the single cell is 20Ah.

[0035] In this embodiment, the individual battery cell is an automotive-grade cylindrical cell (lithium iron phosphate system) with a nominal capacity of 20Ah. The discharge rate is not less than 3C (possessing extremely strong instantaneous power output capability, suitable for UPS burst loads). Figure 4 As shown, a standard 96V / 20Ah PACK is constructed by connecting 30 battery cells in series. The MOSFETs (switching components used for protection circuits) on its protection board can be selected with a withstand voltage of 650V DC to provide sufficient voltage margin. Thus, when multiple PACKs are connected in series to form a 512V system, the MOSFETs can effectively handle voltage spikes, surges, and full-load conditions, serving as electrical safety assurance for a series-connected system with a maximum rated voltage of 512V, preventing component failure due to overvoltage breakdown.

[0036] In this embodiment, the single module is designed with a capacity of 20Ah, supports maximum 3C discharge, supports backup power duration of less than 20 minutes, and features a low capacity and high power ratio. This solution ensures the user's backup power needs within the time required for the UPS to start up the diesel generator, while also avoiding capacity redundancy, thus improving the cost-effectiveness of the terminal solution.

[0037] Optionally, the control units of each battery pack are connected in communication, with the control unit in one battery pack being the master controller and the control units in the other battery packs being slave controllers. The main controller is used to receive battery pack data uploaded by each of the slave controllers; Furthermore, when it is determined, based on the battery pack data of each battery pack, that the first voltage corresponding to any of the battery packs reaches a preset first voltage or the second voltage corresponding to any of the battery packs reaches a preset second voltage, a cut-off control command is output to each of the slave controllers, so that the slave controller controls its corresponding main charging branch to be in a disconnected state.

[0038] In this embodiment, each battery pack also includes a communication module, and each control unit is connected to the other via the communication module. The communication module can be implemented using a CAN communication module.

[0039] It should be noted that the pre-charge branch, main charging branch, and control unit can be integrated, for example, by integrating the pre-charge branch, main charging branch, and control unit into the battery management system (BMS) of the battery pack.

[0040] In this embodiment, the control units (such as BMS) of all PACKs in the backup battery system are connected in series or parallel via a CAN bus to form a communication link. The master controller can be set in the first PACK (or a specific designated PACK). It is the "brain" of the system, responsible for collecting data from the entire system, making decisions, and issuing global commands. The control units of all other PACKs act as slave controllers. At this time, the master controller acts as the master, and the slave controllers act as slaves. The slave controllers are the "executors," responsible for collecting and uploading data from their respective packets and strictly executing the commands of the master.

[0041] Based on the above embodiments, during normal charging and discharging, refer to Figure 4 Both the charging MOS and pre-charge MOS are closed. When the total voltage (first voltage) of any battery in the system reaches 105V or the voltage of a single cell (second voltage) reaches 3.6V, the charging MOS needs to be disconnected. At this time, the main controller sends the corresponding first control command to the slave controllers of all PACKs in the system, so that each slave controller disconnects its own PACK's charging MOS. At the same time, the main controller also outputs the corresponding shutdown control command to its own PACK's charging MOS to ensure that the voltage of the PACKs under each voltage platform can be evenly distributed. At this time, all current will be current-limited and voltage-boosted through the pre-charge circuit (for example, when the external voltage is 115V, the charging current is 1A). The external UPS will not alarm due to sudden current changes or inconsistencies between internal and external voltages. Assuming that the system consists of two 96V PACKs connected in series, during the charging process, the main charging MOS of PACK 1 (main unit) and PACK 2 (slave unit) are both closed, and high-current charging is performed. Because PACK 2 has a slightly higher internal resistance, its voltage rises faster. PACK 2 detects that the single cell voltage has reached 3.6V. The control unit of PACK 2 immediately transmits this "alarm data" to the control unit of PACK 1 (the master unit) via the CAN bus. Upon receiving the alarm data from the slave unit (PACK 2), the master control unit determines that the system needs to stop high-current charging. The master then broadcasts a "disconnect main charging MOS" command to the bus. Both PACK 1 and PACK 2 simultaneously receive the "disconnect main charging MOS" command and disconnect their respective main charging MOS. At this point, both PACKs enter a current-limiting boost state with the "pre-charge branch on".

[0042] Furthermore, when the total voltage of any battery (first voltage) reaches a preset third voltage (e.g., 112V) or the voltage of a single cell (second voltage) reaches a preset fourth voltage (e.g., 3.65V), the main controller sends a corresponding second control command to the slave controller, so that each slave controller turns off its corresponding precharge MOS. At the same time, the main controller controls its corresponding precharge MOS to turn off.

[0043] By issuing unified commands from the host computer, the asynchronous actions of different battery packs caused by sampling time differences and processing speed differences are improved. In a series circuit, if any cell or pack reaches the safety limit, the entire charging process must stop (or switch to trickle / pre-charge mode). This solution, through host computer data aggregation, can capture the pack that "reaches the preset voltage threshold first" in real time, thereby protecting the entire battery pack from overcharging. In addition, for external devices (such as UPS or charging piles), it only needs to interact with the host computer (reading total voltage, total current, SOC, etc.). The host computer packages and processes data from dozens of packs before reporting, greatly reducing the communication burden on the host computer.

[0044] In one embodiment, reference Figure 2 The battery pack also includes a DC miniature circuit breaker, which includes a first trip unit, a first magnetic trip system, a first main contact, a main mechanism, a second main contact, a second magnetic trip system, and a second trip unit connected in series. The first trip unit is electrically connected to the positive terminal, the first main contact is electrically connected to the positive output terminal, the second trip unit is electrically connected to the main charging branch, and the second main contact is electrically connected to the negative output terminal. The main mechanism is used to control the first main contact and the second main contact to disconnect when the first voltage reaches a preset first voltage or the second voltage reaches a preset second voltage and the main charging branch is in a fault state; and to control the first main contact and the second main contact to disconnect when the first voltage reaches a preset third voltage or the second voltage reaches a preset fourth voltage and the pre-charge branch is in a fault state. It is also used to control the closure of the first main contact and the second main contact when the battery pack is in a charging or discharging state.

[0045] The first trip unit is a shunt trip coil, and the second trip unit is a shunt trip coil.

[0046] In this embodiment, the DC miniature circuit breaker acts as the "physical master switch" of the battery pack. Unlike soft protection that relies on electronic switches (such as MOSFETs), the circuit breaker achieves physical isolation through mechanical action, which can completely cut off the current and prevent the battery pack from overcharging, over-discharging, or short-circuiting accidents when electronic components fail.

[0047] In this embodiment, both the first and second trip units are shunt trip coils. A shunt trip unit is an electrical operating mechanism that generates electromagnetic force when its coil is energized, driving the linkage mechanism inside the circuit breaker and triggering a trip. Under normal operating conditions, the shunt trip coil is de-energized and does not affect the circuit breaker's closing. When the BMS detects a serious fault (such as overvoltage, temperature runaway, or communication interruption), the BMS sends a trigger signal (energization) to the shunt trip coil, causing the coil to activate instantaneously, forcing the circuit breaker to trip and disconnecting the corresponding main contacts.

[0048] In this embodiment, the first and second magnetic tripping systems are mainly composed of electromagnets (sowaries) to handle sudden high-current short-circuit faults. When an extremely large short-circuit current (usually several times or even tens of times the rated current) occurs in the circuit, an extremely strong magnetic field is generated inside the electromagnet coil. This magnetic field instantly attracts the internal iron core, directly impacting the tripping mechanism of the circuit breaker. This action is entirely based on physical electromagnetic principles, with an extremely fast response speed (milliseconds). It requires no external control signals and can interrupt the fault current before the electronic protection circuit even has time to react, protecting downstream equipment and lines from damage.

[0049] In this embodiment, the first main contact and the second main contact are the key contact components in the circuit breaker that carry the operating current. When the circuit breaker is closed, the first and second main contacts are in a conductive state, allowing the battery pack to charge and discharge normally; when the circuit breaker is open, the main contacts quickly separate under the action of spring force, forming a clear physical break point, ensuring that the circuit is completely broken and there is no risk of leakage current.

[0050] In this embodiment, the main mechanism receives mechanical force from the trip unit (shunt trip or magnetic trip), and through the linkage transmission system, controls the synchronous closing and opening of the first main contact and the second main contact in a unified manner, ensuring that the positive and negative circuits can be cut off simultaneously under any triggering conditions, thus avoiding the safety hazards caused by single-pole disconnection.

[0051] In this embodiment, when the battery pack is in a normal charging and discharging state, the DC miniature circuit breaker is in a closed state, and current flows through the main contacts. When the system detects a fault requiring emergency disconnection, such as when the charging MOS and pre-charge MOS are out of control, the shunt trip unit operates, achieving protection through the shunt miniature circuit breaker; or, in the event of a short circuit, the magnetic trip system operates, and the main mechanism is released, forcibly disconnecting the first and second main contacts, thereby achieving comprehensive physical isolation protection for the battery pack.

[0052] Optionally, the control unit is further configured to control the first trip unit and the second trip unit to operate when the first voltage is less than the preset discharge voltage and the first voltage is less than the preset operating voltage, so that the main mechanism controls the first main contact and the second main contact to disconnect. Alternatively, the control unit is further configured to control the first trip unit and the second trip unit to operate when the battery pack is in a non-working state for a preset resting time, so that the main mechanism controls the first main contact and the second main contact to disconnect. The battery pack's operating states include charging, discharging, and non-operating states.

[0053] In this embodiment, the preset operating voltage refers to the minimum voltage at which the load (such as a UPS) can operate normally. The preset discharge voltage refers to the cutoff voltage at which the battery pack is allowed to discharge (usually lower than the preset operating voltage). The preset operating voltage and preset discharge voltage are set by the R&D personnel and stored in advance in the memory of the control unit.

[0054] In this embodiment, if the BMS detects that the battery pack is discharging and the voltage is continuously dropping, and the current first voltage is lower than the preset operating voltage, the UPS may have already stopped working or triggered an alarm. If the current first voltage continues to drop below the preset discharge voltage (e.g., the battery's chemical safety threshold), and discharge continues, the battery cells will face the risk of over-discharge and failure. At this point, the BMS's MCU immediately sends a trigger signal (energizes) to the first and second trip units of the DC miniature circuit breaker. The main mechanism activates, forcibly opening the first and second main contacts. Thus, the battery pack is physically disconnected from the load, the voltage stops dropping, and the battery cells are protected.

[0055] Understandably, the control unit also has a built-in timing function to monitor the duration of the battery pack in a non-working state (i.e., neither charging nor discharging, but idle). The preset idle time is set by the R&D personnel and stored in the control unit's memory in advance. In this embodiment, if the control unit has detected that the battery pack is in a non-working state (idle mode) and the idle time reaches the preset idle time (e.g., 30 minutes), although the battery is not outputting anything, the BMS circuitry and the micro-circuit interrupter coil may have slight static power consumption, which can lead to cell depletion (over-discharge caused by self-discharge) over a long period. In order to conserve the remaining power and enter deep sleep mode, the control unit controls the first and second trip units to operate. The DC micro-circuit interrupter executes the disconnect command, and the main contacts separate. In this way, the battery pack enters "open-circuit sleep mode". At this time, except for a very small amount of physical leakage, the battery pack is completely isolated from the outside, maximizing the battery pack's storage life.

[0056] It should be noted that both the first and second trip units are used as shunt trip coils. Unlike the control unit controlling the MOSFET, controlling the trip unit only requires a single pulse signal to trigger a mechanical trip. By simultaneously triggering the trip units on both the positive and negative sides, it is ensured that the first and second main contacts open at the same time, avoiding potential electrical hazards caused by single-pole disconnection.

[0057] By introducing a DC miniature circuit breaker for tripping control, a safety protection mechanism is added to the battery pack. When the voltage drops below the safety threshold, it is forcibly disconnected to prevent over-discharge; when idle time is too long, it is forcibly disconnected to prevent static power loss. This improves the battery pack's lifespan, thereby enhancing the reliability and stability of the backup battery system.

[0058] In another embodiment, reference Figure 3 The battery pack also includes: An overcurrent protection circuit is provided between the positive terminal and the positive output terminal. The overcurrent protection circuit is used to disconnect the electrical connection between the positive terminal and the positive output terminal when the current in the branch it is in reaches a preset current threshold.

[0059] The overcurrent protection circuit includes a three-terminal fuse.

[0060] In this embodiment, since the three-terminal fuse is located in the positive main circuit, once it blows, both the discharge and charging circuits of the entire battery pack are physically cut off. When the battery pack experiences an external short circuit or severe overload, the current flowing through the three-terminal fuse instantly exceeds the preset current threshold. The large current generates a large amount of heat in a very short time, directly melting the internal alloy metal molten element, physically cutting off the circuit, and preventing the battery from catching fire or exploding due to high current discharge. When the battery pack is charging and the voltage rises abnormally (overcharge risk), but the main charging MOSFET fails to turn off in time (e.g., MOSFET breakdown failure), the current flows through the heating terminal (third terminal) of the three-terminal fuse. The internal heating resistor heats up, and the heat is transferred to the adjacent alloy metal molten element, causing the molten element to melt. In this way, the circuit can also be forcibly cut off through "thermal conduction," reducing the risk of thermal runaway due to overcharging.

[0061] refer to Figure 4 The 30 cells in the PACK are connected in series and then pass through the charging MOSFETs of the BMS protection board (a pre-charge branch consisting of a parallel pre-charge MOSFET and a pre-charge resistor), and then through a DC miniature circuit breaker to output the negative terminal; the positive terminal passes through a controllable three-terminal fuse and the DC miniature circuit breaker before being output. The DC miniature circuit breaker has a shunt trip function, which can trigger a trip to protect the battery system in the event of a fault or alarm.

[0062] Based on the above embodiments, this application proposes a triple charging protection mechanism and a dual discharging protection mechanism. The charging protection mechanisms are as follows: Level 1 protection for the charging MOSFET and pre-charging MOSFET; Level 2 protection for the DC power interrupter (which provides protection when the charging MOSFET and pre-charging MOSFET are uncontrolled); and Level 3 protection for the three-terminal fuse (which controls the blowing of the three-terminal fuse to provide protection in case of a shunt trip fault). Similarly, the discharging protection mechanisms are as follows: Level 1 protection for the DC power interrupter (which disconnects when the discharge voltage is too low and below the UPS operating voltage or when the battery cell is depleted due to prolonged idling); and Level 2 protection for the three-terminal fuse (which controls the blowing of the three-terminal fuse to provide protection in case of a shunt trip fault).

[0063] By constructing a triple charging protection mechanism and a dual discharging protection mechanism, the battery pack's safety is effectively protected, significantly improving the reliability and safety of the backup battery system. During charging, the first-level protection is achieved collaboratively by the charging MOSFET and the pre-charging MOSFET, enabling precise on / off control during normal charging and discharging. When a MOSFET malfunctions and becomes uncontrolled, the second-level protection's DC mini-circuit breaker provides mechanical circuit-breaking protection independent of the BMS software through shunt tripping, reducing the risk of overcharging. If the shunt tripping function fails simultaneously, the third-level protection's three-terminal fuse will blow based on overcurrent or overvoltage triggering, forming an irreversible physical disconnect and completely blocking the charging circuit. During discharging, the first-level protection is dominated by the DC mini-circuit breaker, which promptly disconnects the circuit when low voltage or prolonged inactivity may lead to cell depletion, preventing battery over-discharge damage. When the DC mini-circuit breaker trips, the second-level protection's three-terminal fuse acts as a final line of defense. Thus, the multi-level and multi-dimensional protection architecture not only achieves seamless connection from software control to hardware execution, and from recoverable protection to irreversible circuit breaking, but also reduces the risk of a single point of failure through redundant design.

[0064] Optionally, the positive output terminal and / or the negative output terminal include two power connection ports connected in parallel, which are used to connect to electrical equipment or charging equipment.

[0065] In this embodiment, two identical power connection ports are provided on the positive (and / or negative) output terminals of the battery pack. These two ports are internally directly connected (parallel) and electrically form the same node. They are both directly connected to the main circuit inside the battery pack (after passing through the protection circuit). When users need to build a larger capacity battery system (e.g., connecting two 96V battery packs in parallel to form a 96V / 40Ah system), the traditional method requires an additional "parallel box" or complex copper busbar adapter cables to connect the positive and negative terminals of the two battery packs together, and then connect the load. This wiring is complex and prone to errors. (Reference) Figure 5 and Figure 6This application connects one port of battery pack A to the load (or UPS), and uses a jumper cable to directly connect the second port of battery pack A to the corresponding port of battery pack B. This process is repeated to connect multiple battery packs in parallel. Thus, no external parallel box is needed; the battery packs can be connected in parallel using their own ports, simplifying on-site installation and increasing mobility and convenience.

[0066] The above description is merely an optional embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A backup battery system, characterized in that, The backup battery system includes: Multiple battery packs, wherein the multiple battery packs are connected in series; The battery pack includes a battery module, a pre-charge branch, a main charging branch, a control unit, a positive output terminal, and a negative output terminal; The battery module includes a positive terminal, a negative terminal, and multiple individual battery cells, each of which is a lithium iron phosphate battery cell. The pre-charge branch is located between the negative terminal and the negative output terminal. The pre-charge branch is connected in parallel with the main charging branch. The on-resistance of the pre-charge branch is greater than that of the main charging branch. The positive terminal is electrically connected to the positive output terminal. Both the positive and negative output terminals are used to connect to a load. The control unit is used to control the main charging branch and the pre-charging branch to be in a closed state when the corresponding battery pack is in a charging state. It is also used to detect the first voltage between the positive output terminal and the negative output terminal in the battery pack corresponding to itself, and to detect the second voltage of each individual cell in the battery pack corresponding to itself; and to control the main charging branch to be in a disconnected state when the first voltage reaches a preset first voltage or the second voltage reaches a preset second voltage.

2. The backup battery system as described in claim 1, characterized in that, The control unit is further configured to control the pre-charge branch to be in a disconnected state when the first voltage reaches a preset third voltage or the second voltage reaches a preset fourth voltage, wherein the preset third voltage is greater than the preset first voltage and the preset fourth voltage is greater than the preset second voltage.

3. The backup battery system as described in claim 1, characterized in that, The battery pack also includes a DC miniature circuit breaker, which includes a first trip unit, a first magnetic trip system, a first main contact, a main mechanism, a second main contact, a second magnetic trip system, and a second trip unit connected in series. The first trip unit is electrically connected to the positive terminal, the first main contact is electrically connected to the positive output terminal, the second trip unit is electrically connected to the main charging branch, and the second main contact is electrically connected to the negative output terminal. The main mechanism is used to control the first main contact and the second main contact to disconnect when the first voltage reaches a preset first voltage or the second voltage reaches a preset second voltage and the main charging branch is in a fault state; and to control the first main contact and the second main contact to disconnect when the first voltage reaches a preset third voltage or the second voltage reaches a preset fourth voltage and the pre-charge branch is in a fault state. It is also used to control the closure of the first main contact and the second main contact when the battery pack is in a charging or discharging state.

4. The backup battery system as described in claim 3, characterized in that, The control unit is further configured to control the first trip unit and the second trip unit to operate when the first voltage is less than the preset discharge voltage and the first voltage is less than the preset operating voltage, so that the main mechanism controls the first main contact and the second main contact to disconnect. Alternatively, the control unit is further configured to control the first trip unit and the second trip unit to operate when the battery pack is in a non-working state for a preset resting time, so that the main mechanism controls the first main contact and the second main contact to disconnect. The battery pack's operating states include charging, discharging, and non-operating states.

5. The backup battery system as described in claim 3, characterized in that, The first trip unit is a shunt trip coil, and the second trip unit is a shunt trip coil.

6. The backup battery system as described in claim 1, characterized in that, The battery pack also includes: An overcurrent protection circuit is provided between the positive terminal and the positive output terminal. The overcurrent protection circuit is used to disconnect the electrical connection between the positive terminal and the positive output terminal when the current in the branch it is in reaches a preset current threshold.

7. The backup battery system as described in claim 6, characterized in that, The overcurrent protection circuit includes a three-terminal fuse.

8. The backup battery system as described in claim 1, characterized in that, The discharge rate of the single battery cell is not less than 3C, and the capacity of the single battery cell is 20Ah.

9. The backup battery system as described in any one of claims 1 to 8, characterized in that, The control units of each battery pack are connected in communication, with the control unit in one battery pack being the master controller and the control units in the other battery packs being slave controllers. The main controller is used to receive battery pack data uploaded by each of the slave controllers; Furthermore, when it is determined, based on the battery pack data of each battery pack, that the first voltage corresponding to any of the battery packs reaches a preset first voltage or the second voltage corresponding to any of the battery packs reaches a preset second voltage, a cut-off control command is output to each of the slave controllers, so that the slave controller controls its corresponding main charging branch to be in a disconnected state.

10. The backup battery system as described in any one of claims 1 to 8, characterized in that, The positive output terminal and / or the negative output terminal include two power connection ports connected in parallel, which are used to connect to electrical equipment or charging equipment.

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