Non-invasive electric vehicle auxiliary battery parallel safety control device and method

Abstract

This invention relates to the field of automotive battery management technology, specifically to a non-intrusive parallel safety control device and method for auxiliary batteries in electric vehicles. The device includes a three-terminal parallel connection component, a boost converter module, a dual 12V signal detection module, a control module, and a power switch array. The three-terminal component reuses the original vehicle's high-voltage bus, the boost module adapts to the low-voltage auxiliary battery, and uses optocoupler isolation to detect charging and ignition signals. The control module executes electrically independent control logic, only turning on the power switch array during charging and discharging to achieve coordinated operation, and disconnecting it at other times to maintain electrical independence between the main and auxiliary batteries. This application eliminates the safety hazards of long-term parallel connection of new and old batteries without modifying the original vehicle's protocol and circuitry, ensuring the original manufacturer's warranty, and achieving intelligent range expansion and charging management.

Description

Technical Field

[0001] This invention relates to the field of automotive battery management technology, and in particular to a non-intrusive parallel safety control device and method for auxiliary batteries in electric vehicles. Background Technology

[0002] With the rapid development of the new energy vehicle industry, electric commercial vehicles are increasingly widely used in high-frequency scenarios such as logistics and delivery, and taxi operation. As the core power source, the performance of the vehicle's high-voltage power battery directly determines its driving range and operational efficiency. In existing technical solutions, to address the problem of reduced driving range due to battery degradation, the common approach is to modify the original vehicle's battery system or replace it with a larger-capacity battery pack. Some existing technologies increase capacity by directly connecting additional battery packs in parallel, utilizing an additional battery management unit to communicate with the original vehicle's battery management system to coordinate the charging and discharging process; or by directly connecting to the original vehicle's high-voltage bus via physical wiring to replenish and release electrical energy. These solutions can, to some extent, increase the vehicle's total energy reserve and extend the driving range after a single charge.

[0003] However, in existing technologies, the lack of precise timing control over the electrical connection between the main battery and auxiliary battery often results in the old and new batteries being directly connected in parallel for extended periods. This continuous electrical connection can easily lead to circulating current problems caused by inconsistencies in battery internal resistance and open-circuit voltage, potentially causing overcharging or over-discharging safety hazards. Furthermore, existing aftermarket solutions often require deep integration into the original vehicle's communication protocol or modification of the existing circuit architecture, which not only risks voiding the original manufacturer's warranty but also makes it difficult to achieve universal standardized compatibility across different voltage platform models, limiting their large-scale application in the existing market. Summary of the Invention

[0004] The purpose of this invention is to provide a non-intrusive parallel safety control device and method for electric vehicle auxiliary batteries, which solves the technical problems of reduced range of existing electric vehicles due to main battery degradation, and the fact that existing modification schemes easily violate the original vehicle warranty and pose safety hazards due to long-term parallel connection of new and old batteries.

[0005] The first aspect of this application provides a non-intrusive parallel safety control device for an electric vehicle auxiliary battery, comprising: a three-terminal parallel access component, including a first interface for connecting to the high-voltage end of the original vehicle's main battery pack, a second interface for connecting to the vehicle's high-voltage circuit, and a third interface for connecting to the auxiliary power supply circuit, wherein the first interface and the second interface are directly connected in the circuit to reuse the original vehicle's high-voltage bus; a boost converter module, the input end of which is connected to a low-voltage auxiliary battery pack, and the output end of which is connected to the third interface; and a dual 12-volt signal detection module, including an optocoupler isolation circuit, for detecting the 12-volt auxiliary power supply in the charging gun interface respectively. The system includes a source signal and a 12-volt ignition signal from the car key; a control module electrically connected to the boost converter module and the dual 12-volt signal detection module; and a power switch array controlled by the control module, connected between the third interface and the reused original vehicle high-voltage bus, used to realize the circuit connection and disconnection between the high-voltage bus and the boost converter module. The control module is configured to execute electrically independent control logic: controlling the power switch array to conduct only during the discharge and charging phases to achieve cooperative operation, and controlling the power switch array to disconnect during other phases to keep the main battery pack and auxiliary battery pack electrically independent of each other.

[0006] In one optional embodiment, detecting the 12V auxiliary power signal in the charging gun interface includes: detecting the 12V auxiliary power signal in the slow charging interface or detecting the 12V auxiliary power signal in the fast charging interface; the determination logic is that regardless of whether the charging gun is physically inserted, the charging and replenishment process of the auxiliary battery pack is triggered only when a specific level change is detected in the voltage of the 12V auxiliary power pin.

[0007] In one optional embodiment, the boost converter module adopts a four-phase interleaved parallel topology, including four power switch groups with a 90-degree phase difference; four sets of winding inductors electrically connected to each of the power switch groups, wherein the inductors and copper busbars are configured as a low-impedance structure to meet the requirements of high current carrying capacity; and a controller for outputting interleaved PWM signals to control the conduction timing of each of the power switch groups.

[0008] In one optional embodiment, the power switch group uses silicon carbide MOSFET devices; the freewheeling branch of each power switch group uses a silicon carbide Schottky diode or an ideal diode circuit composed of a silicon carbide MOSFET and a control circuit.

[0009] In one optional embodiment, the standby control logic of the dual 12-volt signal detection module is configured as follows: when no 12-volt ignition signal from the car key is detected, the device is in a microampere-level standby state with a monthly power consumption of less than 10 mA; after the ignition signal is detected, the output level of the optocoupler isolation circuit triggers the driving transistor, which in turn sequentially turns on the main switch of the power switch array to achieve a safe power-on logic with low static power consumption.

[0010] In one optional embodiment, the control module includes a charging current intelligent allocation unit, comprising: a high-voltage sampling circuit that acquires the total current analog signal of the charging circuit through a differential amplifier; a digital signal processor that converts the total current analog signal into a digital signal; and the digital signal processor that, without needing to obtain the original vehicle BMS underlying handshake protocol, autonomously regulates the charging current allocation ratio flowing into the main battery pack and the auxiliary battery pack by adjusting the duty cycle of the boost converter module.

[0011] In one optional embodiment, the low-voltage auxiliary battery pack has a voltage specification of 48 volts to 100 volts, and the output voltage of the boost converter module can be dynamically adjusted, with a maximum output voltage of 1000 volts to adapt to 400V, 800V or 1000V vehicle high-voltage platforms; when adapting to a 1000V high-voltage platform, the silicon carbide power devices inside the boost converter module are replaced with 1700V withstand voltage ratings.

[0012] In an optional embodiment, the control module further integrates: an isolated communication circuit, including a CAN communication interface and / or an RS485 communication interface electrically isolated by a common-mode transformer; a watchdog circuit, connected to the reset terminal of the control module, for monitoring the system operating status and resetting in case of abnormality; a temperature detection unit for monitoring the operating temperature of the power devices; and a fan control unit, linked to the temperature detection unit, for adjusting the speed of the cooling fan according to the temperature threshold.

[0013] The second aspect of this application provides a non-intrusive parallel safety control method for electric vehicle auxiliary batteries, applied to a non-intrusive parallel safety control device for electric vehicle auxiliary batteries as described in any one of technical solutions 1-8 of this application, comprising the following steps: S1: The device maintains microampere-level standby power consumption, monitors the 12V ignition signal of the car key through an optocoupler isolation circuit, and after detecting the signal, sequentially turns on the power switch array to complete the power-on process; S2: Real-time acquisition of the original vehicle main battery pack voltage, and estimation of the main battery SOC state based on the cell platform voltage characteristics; S3: When it is determined that the main battery SOC is lower than a preset threshold and the vehicle is in operation, control the low voltage... The auxiliary battery pack is boosted and connected in parallel with the main battery pack to supply power to the vehicle. When the main battery's SOC is determined to be higher than a preset threshold, the circuit is disconnected to maintain electrical independence. S4: The 12-volt auxiliary power signal of the charging gun interface is monitored through an optocoupler isolation circuit. Only when the 12-volt signal is detected to have a level transition that conforms to the charging ready logic is the charging pile determined to be ready for charging. S5: After determining that the charging conditions are ready, without parsing the core handshake communication protocol between the original factory BMS and the charging pile, the total charging current is sampled by hardware and the allocation logic is autonomously adjusted to control the main battery pack and the auxiliary battery pack to charge simultaneously according to the allocation ratio.

[0014] In one optional embodiment, the specific method for estimating the SOC state of the main battery based on the cell platform voltage characteristics is as follows: converting the collected total voltage of the main battery pack into the average voltage of a single cell; for lithium iron phosphate batteries, setting the average voltage of a single cell to a preset SOC safety intervention reference threshold; when the single cell voltage drops to or below the reference threshold, it is determined that the SOC of the main battery has fallen out of the full charge range and entered the discharge platform region, triggering the intervention of the auxiliary battery pack.

[0015] Beneficial effects:

[0016] This application provides a non-intrusive parallel safety control device, method, and system for electric vehicle auxiliary batteries. This solution reuses the original vehicle's high-voltage bus via a three-terminal parallel connection component, and combines a boost converter module to adapt the low-voltage auxiliary battery pack to the vehicle's high-voltage platform. A dual 12V signal detection module accurately identifies the vehicle's starting and charging states. Based on this, the control module, according to electrically independent control logic, controls the power switch array to conduct only during the discharging and charging phases to achieve coordinated operation, while disconnecting the circuit during other phases. This ensures that the main battery pack and auxiliary battery pack remain electrically independent during non-operating periods. This phased on / off control mechanism fundamentally eliminates voltage imbalance and circulating current problems caused by long-term direct parallel connection between new and old batteries, effectively avoiding safety hazards such as overcharging and over-discharging. Simultaneously, by using an optocoupler isolation circuit to detect the 12V auxiliary power signal and ignition signal, non-intrusive state perception is achieved without relying on the original vehicle communication protocol. This ensures the effectiveness of the original vehicle warranty and improves the system's anti-interference capability in complex electromagnetic environments. Furthermore, this solution achieves intelligent allocation of charging current through hardware-level current sampling and autonomous duty cycle regulation, ensuring the flexibility and safety of energy management under different operating conditions, significantly improving vehicle range and asset utilization, and possessing high reliability and versatility.

[0017] In summary, this application systematically solves the compliance, safety, and compatibility challenges in the process of increasing the capacity of electric vehicle batteries by constructing a complete technical closed loop of physical non-intrusive connection, phased electrical isolation, and non-protocol intelligent control, providing solid technical support for the revitalization of existing batteries and pre-installation options for new energy commercial vehicles. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0019] Figure 1 This application provides a structural block diagram of a non-intrusive parallel safety control device for electric vehicle auxiliary batteries;

[0020] Figure 2 The structural block diagram of the control module provided in this application;

[0021] Figure 3 The structural block diagram of the intelligent charging current distribution unit provided in this application;

[0022] Figure 4 A single-phase structural block diagram of the boost converter module provided in this application;

[0023] Figure 5 A flowchart of the non-intrusive electric vehicle auxiliary battery parallel safety control method provided in this application.

[0024] Three-terminal parallel access component 1, boost converter module 2, dual 12V signal detection module 3, control module 4, power switch array 5, high voltage sampling circuit 51, digital signal processor 52, isolation communication circuit 53, watchdog circuit 54, temperature detection unit 55, fan control unit 56. Detailed Implementation

[0025] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0026] First embodiment:

[0027] Please see Figures 1-4 This application provides a non-intrusive parallel safety control device for an electric vehicle auxiliary battery, comprising: a three-terminal parallel access component 1, including a first interface for connecting to the high-voltage end of the original vehicle's main battery pack, a second interface for connecting to the vehicle's high-voltage circuit, and a third interface for connecting to the auxiliary power supply circuit, wherein the first interface and the second interface are directly connected in the circuit to reuse the original vehicle's high-voltage bus; a boost converter module 2, whose input end is connected to the low-voltage auxiliary battery pack, and whose output end is connected to the third interface; and a dual 12-volt signal detection module 3, including an optocoupler isolation circuit, for detecting the 12-volt auxiliary power supply in the charging gun interface respectively. The auxiliary power signal and the 12-volt ignition signal of the car key; control module 4, electrically connected to boost converter module 2 and dual 12-volt signal detection module 3; power switch array 5, controlled by control module 4, connected between the third interface and the reused original vehicle high-voltage bus, used to realize the circuit connection and disconnection between the high-voltage bus and boost converter module 2; control module 4 is configured to execute electrically independent control logic: control power switch array 5 to conduct only during the discharge and charging phases to achieve cooperative operation, and control power switch array 5 to disconnect during the remaining phases to keep the main battery pack and auxiliary battery pack electrically independent of each other.

[0028] The first interface of the three-terminal parallel access component 1 is the terminal directly connected to the high voltage positive and negative terminals of the original vehicle main battery pack, used to obtain electrical energy from the main battery or to feed electrical energy back to it; the second interface is the terminal connected to the load terminals such as the vehicle high voltage power distribution unit (PDU) or motor controller, used to provide high voltage drive power to the vehicle; the third interface is the terminal connected to the auxiliary power supply circuit, serving as a channel for energy injection or output from the auxiliary battery pack.

[0029] The first and second interfaces are directly connected in the circuit, meaning that the original DC path between the main battery pack and the vehicle load is maintained inside the device, reusing the original vehicle high-voltage bus. This ensures that the impedance characteristics and electrical performance of the original vehicle high-voltage circuit remain unchanged when the auxiliary system is not connected. This component, together with the boost converter module 2 and the power switch array 5, forms the physical basis for energy flow: when the power switch array 5 is turned on, the third interface is connected, and the energy from the auxiliary battery pack is boosted and flows into the main high-voltage bus formed by the first and second interfaces; when the power switch array 5 is turned off, the third interface is isolated from the main high-voltage bus, the main battery pack still maintains a normal connection with the vehicle load, while the auxiliary battery pack is in a completely electrically independent state.

[0030] The boost converter module 2 refers to a power electronic converter that converts low-voltage DC voltage to high-voltage DC voltage. In this technical solution, its function is to boost the output voltage of a lower-specification low-voltage auxiliary battery pack (such as non-standard or low-voltage standard batteries such as 48V, 64V, or 100V) to a voltage level suitable for the vehicle's high-voltage platform (such as 400V, 800V, or 1000V), thereby achieving voltage matching and parallel operation between the low-voltage small-capacity battery and the high-voltage large-capacity battery system.

[0031] The dual 12V signal detection module 3 refers to the detection circuit unit used to collect and identify external low-level control signals. Specifically, it includes the 12V auxiliary power signal from the charging gun interface (usually provided by the charging pile after it is ready) and the 12V ignition signal from the car key (ACC or ON position signal). The core component of this module includes an optocoupler isolation circuit, which uses an optocoupler to achieve electrical isolation between the high-voltage side control circuit and the low-voltage side signal source, preventing high-voltage interference from entering the low-voltage signal line or vice versa, thus improving the system's electromagnetic interference (EMI) immunity and safety. In the system's linkage, the dual 12V signal detection module 3 acts as the sensing organ of the entire device, monitoring the vehicle's start-up and charging status in real time, and converting the detected level signals into logic level signals recognizable by the control module 4. When the car key ignition signal is detected, it indicates that the vehicle is about to enter the operating state, and this module triggers the control module 4 to wake up and prepare to enter the discharge coordination mode; when the 12V auxiliary power signal from the charging gun is detected, it indicates that the charging pile is connected and ready for charging, and this module triggers the control module 4 to enter the charging coordination mode. If the above signals are not detected, the device remains in a microampere-level standby state. The specific implementation of this module is an optocoupler detection circuit built with discrete components, which is also a digital isolator chip integrating multiple optocoupler inputs. The light-emitting side of the optocoupler is connected in series with a current-limiting resistor to the signal source, and the light-receiving side is connected to a pull-up or pull-down resistor and a comparator to output high and low levels.

[0032] Control module 4 is electrically connected to dual 12V signal detection module 3 to receive isolated vehicle status signals; it is also electrically connected to boost converter module 2 to send PWM drive signals or communication commands to adjust boost parameters; and it is electrically connected to power switch array 5 to output drive signals to control the on / off state of the high-voltage circuit. During system linkage, control module 4 determines whether the system is currently in a discharging, charging, or idle phase based on the signal type (ignition signal or charging signal) fed back by dual 12V signal detection module 3, combined with internal algorithms (such as voltage sampling and SOC estimation), and outputs corresponding control commands accordingly. For example, upon receiving an ignition signal and determining that the main battery is low on power, control module 4 turns on power switch array 5 and starts boost converter module 2, allowing the auxiliary battery to provide power; upon receiving a charging signal, control module 4 turns on power switch array 5 and adjusts boost module parameters to allow the auxiliary battery to participate in charging; when there is no signal or the vehicle is off and not charging, control module 4 disconnects power switch array 5, electrically isolating the main and auxiliary batteries.

[0033] Power switch array 5 refers to a switch group composed of one or more power switching devices, used to perform physical connection and disconnection operations of the high-voltage circuit. It is controlled by control module 4 and connected in series between the third interface (auxiliary power supply circuit) and the reused original vehicle high-voltage bus (i.e., the direct connection between the first and second interfaces). This component functions as a valve for the flow of high-voltage energy, directly determining whether the auxiliary battery pack forms an electrical circuit with the main battery pack and the vehicle load. In system linkage, the action of power switch array 5 directly responds to the conduction or disconnection commands issued by control module 4. When control module 4 determines that coordinated operation (discharging or charging) is required, it drives power switch array 5 to close. At this time, the output terminal of boost converter module 2 is connected to the high-voltage bus, allowing energy to flow bidirectionally. When control module 4 determines that electrical independence is required (such as when the vehicle is parked or not charging), it drives power switch array 5 to open. At this time, the auxiliary battery pack is completely disconnected from the high-voltage bus, eliminating the static circulating current caused by voltage difference and avoiding the risk of overcharging and over-discharging. The power switch array 5 is specifically composed of a single high-voltage metal-oxide-semiconductor field-effect transistor (MOSFET), or a series-parallel combination of multiple MOSFETs or insulated-gate bipolar transistors (IGBTs) to meet different voltage and current carrying requirements.

[0034] Control module 4 specifies that it only outputs a signal to control the power switch array 5 to conduct during two specific time periods: the discharge phase (when the vehicle is running and the main battery needs recharging) and the charging phase (when an external charging station is connected and recharging is permitted). This allows the main battery pack and the auxiliary battery pack to work in parallel and collaboratively through the boost converter module 2. In all other phases (such as when the vehicle is off and parked, charging is incomplete, or in a fault state), control module 4 controls the power switch array 5 to be disconnected, forcing the main battery pack and the auxiliary battery pack to remain electrically independent. This logic, through time-dimensional isolation, fundamentally solves the long-term circulating current problem caused by poor battery consistency in traditional parallel solutions.

[0035] The core innovation of this application lies in constructing a non-intrusive parallel safety control architecture based on physical three-way access, low-voltage boost adapter, dual-signal optocoupler triggering, and independent electrical timing control. This architecture achieves seamless physical layer access without altering the original vehicle wiring through a three-terminal parallel access component 1. The boost converter module 2 solves the voltage matching problem between the low-voltage auxiliary battery and the high-voltage vehicle platform. Dual 12V signal detection modules 3 enable accurate perception and anti-interference identification of external operating conditions. Through the independent electrical control logic executed by the control module 4, the parallel connection between the main and auxiliary batteries is creatively limited to necessary charging and discharging periods, with forced electrical isolation at other times. This design approach abandons the traditional mode of relying on communication protocol handshakes or long-term direct parallel connection, instead adopting a pure hardware signal triggering and timing isolation mechanism. This effectively solves the safety hazards caused by the parallel connection of new and old batteries while ensuring original factory warranty and avoiding regulatory risks.

[0036] The working process and principle of this application are as follows: After the device is powered on, it first enters a microampere-level standby state. The dual 12V signal detection module 3 continuously monitors the car key ignition signal and the 12V auxiliary power signal of the charging gun. When the user inserts the key or presses the start button, generating a 12V ignition signal, the optocoupler isolation circuit is turned on, sending a high-level trigger signal to the control module 4. The control module 4 is awakened, and it collects the main battery pack voltage. If it determines that the main battery SOC is lower than a preset threshold (such as entering the plateau voltage zone), it outputs a drive signal to turn on the power switch array 5 and starts the boost converter module 2 to boost the power of the low-voltage auxiliary battery pack to the bus voltage, so that it can supply power to the vehicle load together with the main battery pack. When the vehicle is turned off, the ignition signal disappears, or the main battery SOC returns to a high level, the control module 4 turns off the power switch array 5 and cuts off the auxiliary circuit. When a user connects to a charging station and the station outputs a 12V auxiliary power signal, the optocoupler isolation circuit is activated again. Control module 4 determines that the charging phase has begun, activates the power switch array 5, and adjusts the boost converter module 2 to operate in reverse or bypass mode (or only as a path), allowing charging current to flow simultaneously into the main battery pack and the auxiliary battery pack (or through specific allocation logic). Once charging is complete or the charging gun is removed, the 12V signal disappears, and control module 4 immediately shuts off the power switch array 5, returning the two battery packs to an electrically independent state. Throughout the entire process, the main and auxiliary battery packs are only connected when necessary for energy exchange; otherwise, they are completely isolated, eliminating static circulating current.

[0037] Assume the application scenario is an electric logistics vehicle with severely reduced driving range. The original vehicle is equipped with a 400V high-voltage platform, and the main battery pack capacity has decreased to 60% of its original design. The owner has installed the device described in this application and a 64V / 50Ah low-voltage auxiliary battery pack.

[0038] During installation, technicians connect the three-terminal parallel connection component 1 in series to the high-voltage wiring harness between the original vehicle battery pack and the high-voltage distribution box. No wire cutting or connector modification is required. The first interface connects to the battery pack side, the second interface to the load side, and the third interface is reserved. The 64V auxiliary battery pack is then connected to the input terminal of the boost converter module 2.

[0039] While the vehicle is parked, the device remains in a dormant state with extremely low monthly power consumption. When the driver inserts the key to start the vehicle, the ignition switch outputs a 12V signal. The optocoupler inside the device detects this transition, instantly waking up the control module 4. The module reads the main battery voltage as 360V (corresponding to low SOC), then turns on the SiCMOSFET group in the power switch array 5 and activates the four-phase interleaved boost circuit, boosting the 64V auxiliary battery voltage to above 360V. At this point, the auxiliary battery begins to output power to the motor controller, working in conjunction with the original vehicle battery to drive the truck, significantly extending the driving range on a single charge.

[0040] When the truck arrives at the logistics park and plugs in the DC fast charging gun, the charging pile's CC / CP pins establish communication and output a 12V auxiliary power supply. The device's optocoupler detects this signal, and the control module 4 confirms that charging has started, keeps the power switch array 5 on, and controls the boost module to allow the charging current to be diverted into the auxiliary battery pack for recharging.

[0041] When charging is complete and the charging gun is disconnected, or when the driver turns off the engine and gets out of the vehicle, the 12V signal disappears. Within milliseconds, the control module 4 shuts off the power switch array 5, completely disconnecting the auxiliary battery pack from the 400V high-voltage bus. Even if the main battery voltage recovers slightly due to self-recovery, or fluctuates due to temperature changes, because the physical circuit has been disconnected, there is no current exchange between the two batteries, ensuring safety during long-term parking.

[0042] Through the above technical solution, this application achieves the following beneficial effects: Because the three-terminal parallel access component 1 is directly connected to the original vehicle's high-voltage bus without touching the communication protocol, truly non-intrusive installation is achieved, ensuring the effectiveness of the original vehicle warranty and avoiding regulatory risks associated with modifications; Because the boost converter module 2 is designed to boost the low-voltage auxiliary battery to adapt to the high-voltage platform, the standardization and low-cost production of the auxiliary battery pack are achieved, and it can flexibly adapt to different voltage levels of vehicle models; Because a dual 12V signal opto-isolation detection trigger logic is constructed, the vehicle's start-up and charging status can be accurately identified, and opto-coupler isolation effectively suppresses high-voltage side interference, improving the reliability of signal detection; Because an independent electrical control logic is executed, the power switch array 5 is only turned on during the charging and discharging stages, thus eliminating the long-term circulating current caused by voltage inconsistencies between new and old batteries at the source, avoiding safety hazards such as overcharging and over-discharging, and extending the battery system's lifespan; Because the entire system does not require parsing the original BMS underlying protocol, the technical threshold and adaptation difficulty are reduced, enabling the solution to be quickly promoted and applied to various existing new energy commercial vehicles, effectively revitalizing operating assets depreciated due to battery degradation.

[0043] Furthermore, detecting the 12V auxiliary power signal in the charging gun interface includes: detecting the 12V auxiliary power signal in the slow charging interface or detecting the 12V auxiliary power signal in the fast charging interface; the determination logic is that regardless of whether the charging gun is physically inserted, the auxiliary battery pack charging process is triggered only when a specific level change is detected in the voltage of the 12V auxiliary power pin.

[0044] Detecting the 12V auxiliary power signal in the slow charging interface or the 12V auxiliary power signal in the fast charging interface refers to the system connecting to the preset 12V auxiliary power pin in the AC slow charging interface (such as a 7-pin interface) or DC fast charging interface (such as a 9-pin interface) that conforms to the national standard definition via the dual 12V signal detection module 3. This 12V auxiliary power pin is typically configured on the charging pile side to output a high-level signal from the internal control unit of the charging pile after the user completes identity authentication, swipes the card for payment, or the background system confirms the charging command. This application embodiment does not impose special limitations on this; the specific pin definition is adapted and adjusted according to the actual specifications of charging standards (such as GB / T, CCS, CHAdeMO, etc.) of different countries or regions. This technical feature, in conjunction with the optocoupler isolation circuit in the dual 12V signal detection module 3, converts the 12V control signal under external high-voltage conditions into a logic level recognizable by the low-voltage side, thereby obtaining charging preparation status information under the premise of electrical isolation.

[0045] The decision logic is that regardless of whether the charging gun is physically inserted, the charging process for the auxiliary battery pack is triggered only when a specific level transition is detected on the 12V auxiliary power supply pin. This means that the state machine inside the control module 4 is configured to ignore simple mechanical connection states (i.e., insertion of the charging gun) and specifically monitor the dynamic change of the voltage signal from low to high (or from high to low, depending on the specific circuit design). For example, when the charging gun is inserted but no card swiping operation is performed, the 12V auxiliary power supply pin may remain at the default low level or in a floating state, without a level transition, and the system determines that it is not ready. Only when the user completes the operation and the charging pile outputs 12V, causing a sudden change in the pin voltage, does the system recognize it as a valid charging start event. This technical feature, in conjunction with the boost converter module 2 and the power switch array 5, ensures that the power loop is closed and the charging of the auxiliary battery pack is initiated only when it is confirmed that the external charging energy is truly available and authorized, avoiding invalid standby power consumption or potential circuit impact caused by misjudging the insertion status. As an optional implementation, a specific level transition is set such that the voltage value crosses a preset threshold (e.g., jumps from 0V to above 10V) within milliseconds. This is also based on slope detection within a certain time window, and the embodiments of this application do not impose any special limitations on this.

[0046] Furthermore, the boost converter module 2 adopts a four-phase interleaved parallel topology, including four power switch groups with a phase difference of 90 degrees; four sets of winding inductors electrically connected to each power switch group, the inductors and copper busbars are configured as a low-impedance structure to meet the requirements of high current carrying capacity; and a controller for outputting interleaved PWM signals to control the conduction sequence of each power switch group.

[0047] The boost converter module 2 employs a four-phase interleaved parallel topology, which refers to a multi-phase DC-DC converter circuit architecture. This architecture uses multiple identical conversion units (i.e., phases) operating in parallel, with the switching actions of each unit staggered by a specific phase angle. In this application, the function of this topology is to boost the voltage of the low-voltage auxiliary battery pack to the voltage level required by the vehicle's high-voltage platform, while simultaneously using multi-phase interleaving technology to cancel the ripple components of the input and output currents. This structure works in conjunction with the low-voltage auxiliary battery pack and the third interface in the aforementioned embodiment: low-voltage power is input to this module, boosted, and then fed into the reused original vehicle high-voltage bus via the third interface. Through this coordination, the module can achieve smooth high-current output without significantly increasing the size of the filter components, reducing electromagnetic interference to the original vehicle high-voltage bus.

[0048] Four power switch groups with a 90-degree phase difference refer to four independently controlled semiconductor switching devices. Each group is responsible for the energy transfer of one phase, and the conduction times of adjacent groups of switches are electrically delayed by 90 degrees (i.e., one-quarter of a switching cycle). The specific implementation of these power switch groups is determined according to the actual situation; for example, it may be a silicon carbide MOSFET device group or a gallium nitride HEMT device group. This application does not impose any special limitations on this. In the system linkage, these four power switch groups are connected one-to-one with four winding inductors and are turned on and off in turn under the unified scheduling of the controller. This coordination results in the total input current and total output current being composed of the superposition of four sub-currents. Due to the phase difference, the peaks and valleys of the fluctuations of the four sub-currents fill each other, thereby significantly reducing the overall current ripple amplitude and alleviating the thermal stress of individual switches.

[0049] The four sets of winding inductors electrically connected to each power switch group refer to four magnetic energy storage elements, which are connected in series or coupled in the power switch group circuit of the corresponding phase. They are used to store magnetic field energy when the switch is turned on and release energy to maintain continuous current when it is turned off. The inductance, saturation current, and DC resistance parameters of these winding inductors are set according to the boost ratio, switching frequency, and allowable ripple coefficient. For example, they are iron-silicon-aluminum magnetic winding groups or nanocrystalline magnetic core windings. This application does not make any special limitations on this. In terms of functional coordination, these four sets of winding inductors and the aforementioned power switch groups together constitute four Boost boost units. The alternating magnetic field energy generated by them is converted into stable high-voltage DC current through subsequent circuits. The low impedance design minimizes copper and iron losses of the inductors under high current conditions, ensuring the thermal stability of the module under high power density.

[0050] Furthermore, the power switching transistor groups adopt silicon carbide MOSFET devices; the freewheeling branch of each power switching transistor group adopts silicon carbide Schottky diodes or ideal diode circuits composed of silicon carbide MOSFETs and control circuits.

[0051] The freewheeling branch is a circuit branch that provides a continuous current path for the inductor current during the power switch's off period. In this application, it is used to maintain current continuity and prevent voltage spikes. This freewheeling branch uses a silicon carbide Schottky diode. Silicon carbide Schottky diodes have extremely low forward voltage drop and almost zero reverse recovery charge, meaning that the reverse recovery loss generated during current commutation is extremely low. Alternatively, the freewheeling branch can also use an ideal diode circuit composed of a silicon carbide MOSFET and a control circuit. The ideal diode circuit monitors the voltage polarity in real time through the control circuit and actively controls the on / off state of the silicon carbide MOSFET, simulating the unidirectional conductivity of a diode, while further reducing the on-state voltage drop by utilizing the low on-resistance of the MOSFET. In this application, the freewheeling branch works closely with the power switch group; when the power switch group is turned off, the freewheeling branch immediately turns on, releasing the energy stored in the winding inductor to the output terminal. Using silicon carbide Schottky diodes offers advantages such as simple structure and high reliability. Employing ideal diode circuits further reduces conduction losses and improves system efficiency under heavy loads. The specific implementation of the freewheeling branch is selected based on actual cost and efficiency requirements; for example, it could be an independent silicon carbide Schottky diode or a combination of silicon carbide MOSFETs controlled by a driver chip. This application does not impose any special limitations on this implementation.

[0052] Furthermore, the standby control logic of the dual 12V signal detection module 3 is configured such that when no 12V ignition signal from the car key is detected, the device is in a microampere-level standby state with a monthly power consumption of less than 10 mA. After the ignition signal is detected, the output level of the optocoupler isolation circuit triggers the driving transistor, which in turn turns on the main switch of the power switch array 5 step by step to achieve a safe power-on logic with low static power consumption.

[0053] The microampere-level standby state refers to the low-power operation mode of the dual 12-volt signal detection module 3 when it does not receive a valid trigger signal. In this state, except for the necessary signal monitoring circuits, other functional units inside the device, such as the boost converter module 2 and the power switch array 5, are all in a shut-off or dormant state. This state is designed to address the technical problem of the auxiliary battery running out of power due to excessive static power consumption of the control device during long-term vehicle parking. The monthly power consumption in the microampere-level standby state is set according to actual conditions, for example, less than 10 mAh, or even lower; this application does not impose any special limitations on this. This low-power characteristic allows the auxiliary battery pack to retain sufficient power to support system wake-up even after the vehicle has been parked for 2 to 3 months, ensuring the availability of the device.

[0054] An optocoupler isolation circuit is a circuit component used to electrically isolate the 12-volt ignition signal generated by a car key and convert it into a control level. Its input is connected to the vehicle's ignition signal line, and its output is connected to the subsequent drive circuit. When the car key is turned to the ignition position, generating a 12-volt voltage signal, the LED inside the optocoupler isolation circuit conducts and illuminates, causing the phototransistor to conduct, thus generating a corresponding level transition at the output. This level transition serves as a trigger signal to initiate the subsequent power-on process. The use of the optocoupler isolation circuit not only achieves electrical isolation between the high-voltage side and the low-voltage control side, improving the system's anti-interference capability and safety, but also ensures that the system only exits standby mode when a clear physical ignition action is detected.

[0055] A driver transistor is a semiconductor switching device that receives the output signal from an optocoupler isolation circuit and amplifies the current. Its base or gate is connected to the output terminal of the optocoupler isolation circuit, and its collector or drain is connected to the control terminal of the power switch array 5. When the optocoupler isolation circuit outputs a high level, the driver transistor conducts, amplifying the small control current into a drive current sufficient to drive the main switch of the power switch array 5. The driver transistor here performs signal amplification and primary drive functions, and is a key link in converting weak detection signals into strong driving capabilities. Depending on the actual design requirements, the driver transistor can be a single-stage structure or a multi-stage Darlington transistor structure; this application does not impose any special limitations on this.

[0056] The main switch in power switch array 5 refers to a high-power switching device connected in series in the main path of the auxiliary power supply circuit, used to control the connection and disconnection between the entire auxiliary battery pack and the vehicle's high-voltage bus. This main switch is controlled by the output signal of the drive transistor. In standby mode, the main switch is off, cutting off the high-current circuit and thus ensuring extremely low static power consumption. When the drive transistor is triggered to conduct, the main switch receives the drive signal and gradually turns on, connecting the high-voltage circuit. The type of main switch is determined according to actual conditions, such as MOSFET, IGBT, or other types of power semiconductor devices; this application embodiment does not impose any special limitations on this.

[0057] Furthermore, the control module 4 is equipped with a charging current intelligent distribution unit, including: a high-voltage sampling circuit 51, which collects the total current analog signal of the charging circuit through a differential amplifier; a digital signal processor 52, which converts the total current analog signal into a digital signal; and a digital signal processor 52, which, without needing to obtain the original vehicle BMS underlying handshake protocol, autonomously regulates the charging current distribution ratio flowing into the main battery pack and the auxiliary battery pack by adjusting the duty cycle of the boost converter module 2.

[0058] During the charging phase, once the charging gun is inserted and a connection is established, the high-voltage sampling circuit 51 monitors the analog signal of the total current flowing through the charging circuit in real time and transmits this signal to the digital signal processor 52. The digital signal processor 52 digitizes the received analog signal to obtain the current real-time total current value. Subsequently, based on the allocation strategy pre-stored in the memory (e.g., setting the auxiliary battery pack to occupy 30% of the total current) and the current voltage state of the auxiliary battery pack, the digital signal processor 52 calculates the target output power required by the boost converter module 2. Then, by adjusting the duty cycle of the PWM signal output to the boost converter module 2, the digital signal processor 52 changes the equivalent input impedance or output current capability of the boost converter module 2, thereby guiding the charging current to be distributed to the main battery pack and the auxiliary battery pack according to a predetermined ratio. If a fluctuation in the total current is detected, the digital signal processor 52 immediately recalculates and adjusts the duty cycle to maintain a constant allocation ratio. The entire process is completed in a closed loop within the device, without any data interaction with the vehicle's BMS.

[0059] Furthermore, the low-voltage auxiliary battery pack has a voltage specification of 48 volts to 100 volts, and the output voltage of the boost converter module 2 can be dynamically adjusted, with a maximum output voltage of 1000 volts to adapt to 400V, 800V or 1000V vehicle high-voltage platforms; when adapting to a 1000V high-voltage platform, the silicon carbide power devices inside the boost converter module 2 are replaced with 1700V withstand voltage rating.

[0060] Furthermore, the control module 4 also integrates: an isolation communication circuit 53, including a CAN communication interface and / or an RS485 communication interface electrically isolated by a common-mode transformer; a watchdog circuit 54, connected to the reset terminal of the control module 4, used to monitor the system operating status and reset in case of abnormality; a temperature detection unit 55, used to monitor the operating temperature of the power devices; and a fan control unit 56, linked with the temperature detection unit 55, to adjust the cooling fan speed according to the temperature threshold.

[0061] The isolation communication circuit 53 refers to a circuit component that enables data exchange between the control module 4 and external devices or networks and provides electrical isolation. In this solution, the isolation communication circuit 53 is positioned to establish a secure communication link, preventing damage to the internal control chip from external high-voltage interference or ground potential differences. It includes a CAN communication interface and / or an RS485 communication interface electrically isolated via a common-mode transformer. The common-mode transformer is a magnetic element that provides a differential signal transmission path and suppresses common-mode noise. The CAN communication interface is a physical interface conforming to the Controller Area Network (CAN) protocol, and the RS485 communication interface is a physical interface conforming to the serial communication standard. The isolation communication circuit 53 is electrically connected to the processor in the control module 4, and the common-mode transformer electrically isolates the internal logic level from the external bus level, forming a signal transmission channel. In specific implementations, the isolation communication circuit 53 can be constructed using a CAN transceiver with integrated isolation function in conjunction with a common-mode transformer, or it can be constructed using a digital isolator chip in conjunction with a traditional transceiver. This application does not impose any special limitations on this embodiment. Through the above coordination, the isolated communication circuit 53 can stably transmit data in the complex electromagnetic environment of the vehicle, avoiding communication interruption or hardware damage caused by ground loop current or surge impact.

[0062] The watchdog circuit 54 is a hardware circuit used to monitor the operating status of the control system software and perform a reset operation when an anomaly occurs. In this solution, the watchdog circuit 54 is positioned to provide a self-recovery mechanism for system faults, ensuring the long-term reliability of the device. It is connected to the reset pin of the control module 4, which is a dedicated reset pin for the control chip. The watchdog circuit 54 is electrically connected to the control module 4. When the control module 4 is operating normally, the software needs to periodically send a feed signal to the watchdog circuit 54 to reset the timer. If the software crashes or malfunctions, causing the feed signal to be missing, the watchdog circuit 54 will output a reset pulse to the reset pin after the timeout, forcing the control module 4 to restart. In specific implementations, the watchdog circuit 54 is an independent external watchdog chip, or it is a watchdog module integrated inside the microcontroller. Its timeout period is set according to the actual situation, for example, it could be hundreds of milliseconds or several seconds; this embodiment does not impose any special limitations on this. Through the above cooperation, the watchdog circuit 54 can monitor the system operating status in real time and automatically trigger a reset when a program anomaly is detected, restoring the system to its initial operating state.

[0063] The temperature detection unit 55 is a sensing component used to collect real-time operating temperature data of the power devices. In this solution, the temperature detection unit 55 functions to provide temperature feedback for thermal management strategies, preventing damage to the power devices due to overheating. It monitors the operating temperature of the power devices, which are heat-generating components such as power switching transistors or freewheeling diodes in the boost converter module 2. The temperature detection unit 55 is positioned near the power devices or directly attached to their surface, acquiring temperature information through heat conduction and converting it into an electrical signal for transmission to the control module 4. In specific implementations, the temperature detection unit 55 can be a negative temperature coefficient thermistor (NTC), a positive temperature coefficient thermistor (PTC), or a digital temperature sensor such as the DS18B20. Its installation location is determined based on the heat dissipation structure layout, and this embodiment does not impose any special limitations on this. Through the above coordination, the temperature detection unit 55 can accurately reflect the real-time temperature rise of the power devices, providing data support for subsequent fan speed adjustment.

[0064] The fan control unit 56 is an execution circuit that adjusts the speed of the cooling fan based on temperature detection results. In this solution, the fan control unit 56 is positioned to implement dynamic heat dissipation control, balancing heat dissipation efficiency with energy consumption and noise. It is linked with the temperature detection unit 55, receiving temperature signals from the unit and adjusting the cooling fan speed according to a preset temperature threshold. The fan control unit 56 is electrically connected to the cooling fan, changing the fan speed via pulse width modulation (PWM) signals or voltage regulation. In specific implementations, the fan control unit 56 is a MOSFET driver circuit and a dedicated fan driver chip. Its adjustment strategy is both segmented speed regulation and continuous linear speed regulation. For example, the fan stops when the temperature is below a first threshold, operates at low speed when the temperature is between the first and second thresholds, and operates at full speed when the temperature is above the second threshold. This embodiment does not impose any special limitations on this. Through the above coordination, the fan control unit 56 can dynamically adjust the heat dissipation intensity according to the actual heat generation of the power device, reducing energy consumption and noise at low temperatures and low loads, and ensuring sufficient heat dissipation at high temperatures and high loads.

[0065] Second Embodiment

[0066] Please see Figure 5 This invention provides a non-intrusive parallel safety control method for auxiliary batteries in electric vehicles, comprising the following steps:

[0067] The S1 device maintains a microampere-level standby power consumption and monitors the 12-volt ignition signal of the car key through an optocoupler isolation circuit. After detecting the signal, it sequentially turns on the power switch array to complete the power-on process.

[0068] Microampere-level standby power consumption refers to the extremely low static current of the control module and detection circuit when not in operation, typically less than 10 mA / h per month, ensuring that the auxiliary battery pack does not run out of power during long-term vehicle parking (e.g., weeks or months). The optocoupler isolation circuit is a core component of the dual 12V signal detection module. Its input is connected to the ignition signal line of the car key, and its output is connected to the logic judgment unit of the control module. It utilizes photoelectric conversion characteristics to achieve electrical isolation between the low-voltage ignition signal and the high-voltage control circuit, effectively suppressing the impact of vehicle electromagnetic interference on the control logic. Step-by-step conduction means that the power-on process is not an instantaneous full-load connection. Instead, the optocoupler output level first triggers the front-stage driver transistor, then the driver transistor turns on the intermediate-stage switch, and finally the intermediate-stage switch controls the main switch of the power switch array to close. This step-by-step start-up mechanism avoids the large current surge at power-on, improving system reliability. For example, when the driver inserts the key and turns it to the ON position, the original vehicle circuit outputs a 12V high-level signal. This voltage signal is converted into a logic high-level signal after optocoupler isolation and sent to the digital signal processor. The processor then issues timing control commands, sequentially lighting up each stage of the drive circuit within milliseconds, ultimately connecting the high-voltage circuit between the main battery pack and the auxiliary battery pack. Through this triggering method based on a physical ignition signal, the device can achieve instant wake-up without continuously polling the high-voltage bus, significantly reducing standby power consumption.

[0069] S2 collects the original vehicle's main battery pack voltage in real time and estimates the main battery's SOC state based on the cell platform voltage characteristics.

[0070] Real-time data acquisition is accomplished through a high-voltage sampling circuit. This circuit uses a differential amplifier to directly measure the analog total voltage signal between the positive and negative terminals of the main battery pack and converts it into a digital signal, which is then transmitted to a digital signal processor. Cell-based voltage plateau characteristic estimation refers to inverse estimation that does not rely on complex coulomb integration methods or precise SOC data released by the original manufacturer's BMS, but rather utilizes the plateau region characteristics of lithium batteries (especially lithium iron phosphate batteries) with gradual voltage changes within a specific state of charge range. Specifically, the system converts the acquired total voltage into the average voltage of a single cell and compares this average voltage with a preset voltage-SOC mapping table. For example, for a lithium iron phosphate cell with a nominal voltage of 3.2V, when its average single-cell voltage is between 3.25V and 3.35V, the corresponding main battery SOC is typically in the 20% to 80% plateau region; when the voltage is higher than 3.45V, the SOC is determined to be in the high-saturation region; and when the voltage is lower than 3.10V, the SOC is determined to be in the low-depletion region. By monitoring whether the voltage drops out of the full charge range and enters the discharge plateau region, the system can determine the remaining energy state of the main battery in a low-cost and highly reliable manner, thereby providing a basis for subsequent intervention decisions.

[0071] When S3 determines that the main battery SOC is lower than the preset threshold and the vehicle is in operation, it controls the low-voltage auxiliary battery pack to be boosted and connected in parallel with the main battery pack to supply power to the vehicle; when it determines that the main battery SOC is higher than the preset threshold, it disconnects the circuit to maintain electrical independence.

[0072] The preset threshold is a critical point set based on the battery's chemical characteristics, for example, the voltage value corresponding to SOC=80%. The vehicle's running status is confirmed by the continuously detected ignition signal. The low-voltage auxiliary battery pack typically uses a standardized specification of 48V to 100V, and its output voltage is much lower than the vehicle's high-voltage bus voltage (such as 400V or 800V), therefore it must be boosted by a voltage boosting module. The boosting module uses a four-phase interleaved parallel topology, adjusting the duty cycle of the power switches to convert the low-voltage DC to a high-voltage DC that matches the current main battery pack voltage. Parallel coordination means that when the boosted voltage matches the main battery pack voltage, the control module drives the power switch array to close, allowing both power sources to jointly supply power to the motor inverter load. At this time, the total output current is the sum of the main battery current and the auxiliary battery current. Disconnecting the circuit to maintain electrical independence means that when the main battery has sufficient charge (SOC above the threshold) or the vehicle is off, the power switch array is in the off state, and the main battery pack and auxiliary battery pack are completely electrically isolated, with no current exchange. For example, when the system detects that the main battery cell voltage drops to 3.28V (corresponding to approximately 75% SOC) and the ignition signal remains, it immediately initiates the boost process and closes the high-voltage switch, allowing the auxiliary battery to begin outputting power to slow the rate of voltage drop in the main battery. Conversely, if the main battery voltage is detected to rise back to 3.40V (indicating that recharge recovery or reduced load has led to an increase in SOC), the parallel circuit is immediately disconnected. This dynamic on / off control strategy eliminates the long-term parallel circulating current problem caused by inconsistencies in internal resistance and capacity between new and old batteries, ensuring the safety and lifespan of the battery pack.

[0073] S4 monitors the 12V auxiliary power signal of the charging gun interface through an optocoupler isolation circuit. It determines that the charging pile is ready to charge only when it detects a level transition of the 12V signal that conforms to the charging ready logic.

[0074] The charging gun interface includes a national standard slow charging interface (7 pins) or a fast charging interface (9 pins). Both interfaces define a 12V auxiliary power pin (such as the CC / CP-related auxiliary power supply in slow charging or the low-voltage auxiliary power supply line in fast charging). The optocoupler isolation circuit also serves a dual purpose of signal acquisition and high-voltage isolation here, with its input connected across the 12V auxiliary line of the charging gun. The level transition of the charging ready logic refers to the process by which the charging pile officially outputs a stable 12V auxiliary voltage, or the transition of this voltage from zero to one, after completing user authentication (such as card swiping or QR code scanning) and establishing initial communication with the vehicle. The system does not parse complex CAN bus handshake messages; it only captures this specific voltage step signal through hardware circuitry. For example, when the user inserts the charging gun but has not paid, the voltage of the charging gun's auxiliary pin is 0V or floating low; when the user completes the payment operation, the internal relay of the charging pile engages, and the voltage of the auxiliary pin instantly jumps to a 12V high level. After detecting this rising edge transition, the optocoupler sends a charging ready flag bit to the control module. Through this purely hardware-level signal feature recognition, the device can accurately determine whether external charging energy is truly available, avoiding the situation where the charging process is mistakenly started simply by inserting the charging gun, and achieving accurate perception of charging status without protocol dependence.

[0075] After determining that charging conditions are met, the S5 uses hardware sampling to obtain the total charging current without parsing the core handshake communication protocol between the original BMS and the charging pile, and autonomously adjusts the allocation logic to control the main battery pack and auxiliary battery pack to charge simultaneously according to the allocation ratio.

[0076] Not parsing the core handshake communication protocol between the original vehicle BMS and the charging pile means that this method completely bypasses the complex interactive messages on the CAN bus (such as charging demand messages, charger maximum output capacity messages, etc.), and does not attempt to disguise communication between the original vehicle BMS and the charging pile, thus avoiding the legal and technical risks of protocol cracking. Hardware sampling to obtain the total charging current is achieved through a Hall current sensor or shunt connected in series in the charging circuit, directly measuring the total current flowing into the vehicle's high-voltage bus. Autonomous control and allocation logic refers to the digital signal processor calculating the target charging current value required by the auxiliary battery according to a preset strategy (such as prioritizing the charging of the auxiliary battery, proportionally distributing the charge, or allocating based on temperature limits), and changing its equivalent input impedance by adjusting the PWM duty cycle of the boost converter module, thereby controlling the current flowing into the auxiliary battery pack. Since the main battery pack is directly connected to the high-voltage bus, its charging current is naturally determined by the total current minus the auxiliary battery current. For example, if the hardware sampling measures a total output current of 100A from the charging pile, and the system is set to charge the auxiliary battery at 30A, the control module adjusts the boost module to absorb 30A of current, while the remaining 70A automatically flows into the main battery pack. During this process, regardless of the current request from the original BMS, this device achieves independent control of the auxiliary battery through physical current shunting. This blind control mode ensures that the auxiliary battery can utilize the charging pile resources for rapid charging without affecting the normal operation and safety monitoring of the original vehicle's charging system, achieving truly non-intrusive parallel charging.

[0077] This application constructs a complete non-intrusive battery energy management system through the synergistic effect of the above steps. First, the aforementioned microampere-level standby and optocoupler ignition triggering mechanism solves the pain point of auxiliary battery depletion during long-term parking, ensuring the system is always ready without consuming the main vehicle's power. Second, combining the above with the above, the system uses the cell platform voltage characteristics to replace complex protocol communication to determine SOC, realizing an intelligent strategy where the auxiliary battery only intervenes to discharge when the main battery's power is insufficient. This avoids the safety hazards caused by parallel connection of new and old batteries and maximizes the lifespan of the main battery. Third, the above method of identifying the charging status by detecting the physical transition of the charging gun's 12V signal eliminates dependence on the original manufacturer's charging protocol, enabling the device to adapt to various brands and protocols of electric vehicles. Finally, the aforementioned hardware current sampling and autonomous allocation logic cleverly utilizes Kirchhoff's current law to achieve synchronous charging of the dual battery packs without interfering with the original vehicle's BMS operation. The entire process, from power-on wake-up and discharge coordination to charging and replenishment, is based on physical signal perception and hardware closed-loop control. It does not require modification of the vehicle software or cracking of communication protocols. While ensuring compliance with the original factory warranty of the vehicle, it effectively solves the range anxiety problem caused by battery degradation in operating vehicles, and significantly improves the asset value and operating efficiency of the vehicle.

[0078] Furthermore, this application also provides a specific implementation method for estimating the main battery's SOC state based on the cell platform voltage characteristics, including:

[0079] The total voltage of the main battery pack is converted into the average voltage of a single cell.

[0080] The total voltage of the main battery pack is obtained by converting an analog signal acquired in real time by a high-voltage sampling circuit into a digital value using a digital signal processor (DSP). The average voltage of a single cell refers to the arithmetic mean of the voltages of all cells connected in series within the main battery pack, and its calculation formula is: ,in The total voltage of the battery pack was collected. This refers to the number of cells connected in series within the battery pack. This conversion process does not require obtaining individual cell voltage balancing data from the Battery Management System (BMS); it relies solely on external total voltage monitoring. For example, for a lithium iron phosphate battery pack with a nominal voltage of 400V, if it consists of 120 cells connected in series, when the total voltage is collected at 390V, the calculated average voltage of each cell is 3.25V. This total voltage conversion method allows for the rapid acquisition of key parameters characterizing the overall energy state of the battery without intruding on the original vehicle communication protocol, providing a unified data benchmark for subsequent threshold determination.

[0081] For lithium iron phosphate batteries, the average voltage of a single cell is set to a preset SOC safety intervention reference threshold.

[0082] The preset SOC safety intervention reference threshold is a critical voltage value pre-set based on the discharge curve characteristics of lithium iron phosphate (LFP) batteries. Because the open-circuit voltage of LFP batteries changes very little within the SOC range of 20% to 80%, forming a clear voltage plateau, while the voltage changes more drastically in the fully charged state (SOC>80%) and the depleted state (SOC<20%). Therefore, this threshold is usually selected as the voltage value corresponding to the starting point of the voltage plateau region to distinguish whether the battery has entered the stable discharge region from the high-voltage fully charged region. For example, for common LFP cells, this reference threshold can be set to 3.25V or 3.28V. When the average voltage of a single cell is higher than this threshold, it indicates that the main battery is still in the high-capacity range and no auxiliary battery intervention is required; when the voltage is close to or lower than this threshold, it means that the main battery has entered the main discharge stage. This threshold setting avoids misjudgments caused by individual battery differences, ensuring that the auxiliary battery only starts when necessary, thereby optimizing the energy efficiency management of the dual-battery system.

[0083] When the voltage of a single cell drops to or below the reference threshold, it is determined that the main battery's SOC has fallen out of the full charge range and entered the discharge platform region, triggering the intervention of the auxiliary battery pack.

[0084] The determination process is completed by the logic operation unit within the control module continuously executing comparison operations. Once the average voltage of the individual battery cell is detected... Less than or equal to the preset reference threshold The control module generates a trigger signal, instructing the power switch array to conduct, enabling the low-voltage auxiliary battery pack to be boosted and connected in parallel with the main battery pack. The system first acquires the total voltage and converts it into the average voltage of each cell, then compares it with a preset threshold. When the curve trend shows that the voltage drops below the threshold line, the process branch points to the trigger intervention state. This logic utilizes the unique voltage plateau characteristics of lithium iron phosphate batteries, accurately identifying the battery capacity status without the need for complex ampere-hour integration algorithms. Through this voltage triggering mechanism, the circulating current impact that may occur when new and old batteries are directly connected in parallel at full charge is effectively avoided, while ensuring timely replenishment of power when the main battery is low, significantly improving the reliability of the vehicle's range.

[0085] This application constructs a low-cost, high-reliability battery state estimation and intervention mechanism through the synergistic effect of the aforementioned technical features. By converting the total voltage of the main battery pack into the average voltage of individual cells and setting a safe intervention reference threshold based on the unique voltage plateau characteristics of lithium iron phosphate batteries, the system can accurately determine whether the main battery has dropped out of its full-charge range without parsing the complex communication protocol of the original vehicle's BMS. When the voltage of an individual cell drops to or below the threshold, the auxiliary battery pack is immediately triggered to intervene. This not only utilizes the physical characteristic of lithium iron phosphate batteries' stable voltage in the plateau region to avoid estimation errors but also fundamentally solves the safety hazards caused by directly connecting new and old batteries in parallel due to inconsistent initial voltages. With this voltage plateau-based adaptive judgment logic, the auxiliary battery only operates in the discharge plateau region where the main battery truly needs support, extending the lifespan of the auxiliary battery and maximizing the utilization of the vehicle's range, ultimately achieving a non-intrusive and safe capacity expansion technical effect.

[0086] The above-disclosed embodiments are merely one or more preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art will understand that all or part of the processes for implementing the above embodiments and equivalent variations made in accordance with the claims of this application are still within the scope of this application.

Claims

1. A non-intrusive parallel safety control device for auxiliary batteries in electric vehicles, Its features are, Includes: a three-terminal parallel access component, including a first interface for connecting to the high-voltage end of the original vehicle's main battery pack, a second interface for connecting to the high-voltage circuit of the whole vehicle, and a third interface for connecting to the auxiliary power supply circuit. The first interface and the second interface are directly connected in the circuit to reuse the original vehicle's high-voltage bus. The boost converter module has its input terminal connected to the low-voltage auxiliary battery pack and its output terminal connected to the third interface. The dual 12V signal detection module includes an optocoupler isolation circuit for detecting the 12V auxiliary power signal in the charging gun interface and the 12V ignition signal of the car key, respectively. The control module is electrically connected to the boost converter module and the dual 12V signal detection module; A power switch array, controlled by the control module, is connected between the third interface and the reused original vehicle high-voltage bus, and is used to realize the circuit connection and disconnection between the high-voltage bus and the step-up conversion module. The control module is configured to execute electrically independent control logic: controlling the power switch array to turn on only during the discharge and charging phases to achieve cooperative operation, and controlling the power switch array to turn off during the remaining phases to keep the main battery pack and auxiliary battery pack electrically independent of each other.

2. The non-intrusive parallel safety control device for electric vehicle auxiliary batteries as described in claim 1, characterized in that, Detecting the 12-volt auxiliary power signal in the charging gun interface includes: The system detects the 12V auxiliary power signal in the slow charging port or the 12V auxiliary power signal in the fast charging port. The decision logic is that regardless of whether the charging gun is physically inserted, the auxiliary battery pack charging process is only triggered when a specific level change is detected in the voltage of the 12V auxiliary power pin.

3. The non-intrusive parallel safety control device for electric vehicle auxiliary batteries as described in claim 1, characterized in that, The boost converter module adopts a four-phase interleaved parallel topology, including four power switch groups with a phase difference of 90 degrees; four sets of winding inductors electrically connected to each of the power switch groups, wherein the inductors and copper busbars are configured as a low-impedance structure to meet the requirements of high current carrying capacity; and a controller for outputting interleaved PWM signals to control the conduction timing of each of the power switch groups.

4. The non-intrusive parallel safety control device for electric vehicle auxiliary batteries as described in claim 3, characterized in that, The power switching transistor group adopts silicon carbide MOSFET devices; the freewheeling branch of each power switching transistor group adopts silicon carbide Schottky diode or an ideal diode circuit composed of silicon carbide MOSFET and control circuit.

5. The non-intrusive parallel safety control device for electric vehicle auxiliary batteries as described in claim 1, characterized in that, The standby control logic of the dual 12V signal detection module is configured as follows: when no 12V ignition signal from the car key is detected, the device is in a microampere-level standby state with a monthly power consumption of less than 10 mA; after the ignition signal is detected, the output level of the optocoupler isolation circuit triggers the driving transistor, which in turn turns on the main switch of the power switch array step by step to achieve a safe power-on logic with low static power consumption.

6. The non-intrusive parallel safety control device for auxiliary batteries in electric vehicles as described in claim 1, characterized in that, The control module includes a charging current intelligent allocation unit, comprising: The high-voltage sampling circuit acquires the analog signal of the total current in the charging circuit through a differential amplifier; A digital signal processor converts the total current analog signal into a digital signal; The digital signal processor, without needing to obtain the original vehicle BMS underlying handshake protocol, autonomously regulates the charging current distribution ratio flowing into the main battery pack and the auxiliary battery pack by adjusting the duty cycle of the boost converter module.

7. The non-intrusive parallel safety control device for auxiliary batteries in electric vehicles as described in claim 1, characterized in that, The low-voltage auxiliary battery pack has a voltage specification of 48 volts to 100 volts. The output voltage of the boost converter module can be dynamically adjusted, with a maximum output voltage of 1000 volts to adapt to 400V, 800V or 1000V vehicle high-voltage platforms. When adapting to a 1000V high-voltage platform, the silicon carbide power devices inside the boost converter module are replaced with 1700V withstand voltage rating devices.

8. The non-intrusive parallel safety control device for electric vehicle auxiliary batteries as described in claim 1, characterized in that, The control module also integrates: Isolated communication circuitry, including a CAN communication interface and / or an RS485 communication interface electrically isolated via a common-mode transformer; A watchdog circuit, connected to the reset terminal of the control module, is used to monitor the system's operating status and reset it in case of an anomaly. Temperature detection unit is used to monitor the operating temperature of power devices; The fan control unit is linked with the temperature detection unit to adjust the cooling fan speed according to the temperature threshold.

9. A non-intrusive parallel safety control method for an electric vehicle auxiliary battery, applied to the non-intrusive parallel safety control device for an electric vehicle auxiliary battery as described in any one of claims 1-8, characterized in that, Includes the following steps: S1: The device maintains a microampere-level standby power consumption and monitors the 12-volt ignition signal of the car key through an optocoupler isolation circuit. After detecting the signal, the power switch array is turned on step by step to complete the power-on process. S2: Real-time acquisition of the original vehicle's main battery pack voltage, and estimation of the main battery's SOC state based on the cell platform voltage characteristics; S3: When the main battery SOC is determined to be lower than the preset threshold and the vehicle is in operation, the low-voltage auxiliary battery pack is controlled to be boosted and connected in parallel with the main battery pack to supply power to the vehicle; when the main battery SOC is determined to be higher than the preset threshold, the circuit is disconnected to maintain electrical independence. S4: Monitor the 12V auxiliary power signal of the charging gun interface through the optocoupler isolation circuit, and determine that the charging pile is ready to charge only when the 12V signal undergoes a level transition that conforms to the charging ready logic. S5: After determining that the charging conditions are met, without parsing the core handshake communication protocol between the original BMS and the charging pile, the hardware samples and obtains the total charging current, and autonomously adjusts the allocation logic to control the main battery pack and auxiliary battery pack to charge simultaneously according to the allocation ratio.

10. The non-intrusive parallel safety control method for auxiliary batteries in electric vehicles as described in claim 9, characterized in that, The specific method for estimating the SOC state of the main battery based on the cell platform voltage characteristics is as follows: The total voltage of the main battery pack is converted into the average voltage of a single cell. For lithium iron phosphate batteries, the average voltage of a single cell is set to a preset SOC safety intervention reference threshold. When the voltage of a single cell drops to or below the reference threshold, it is determined that the main battery's SOC has fallen out of the full charge range and entered the discharge platform region, triggering the intervention of the auxiliary battery pack.

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