A battery discharge control method and system

Abstract

The application discloses a battery discharge control method and system, and the control method comprises the following steps: a pre-discharge branch is arranged in parallel at both ends of a main discharge branch of a battery, the pre-discharge branch is provided with a switch Q1 and a pre-discharge resistor, and the main discharge branch is provided with a discharge switch Q2; a load is connected, and an end voltage of the load is sampled; in the state that the Q1 is closed and the Q2 is disconnected, it is judged whether the end voltage of the load meets a discharge condition; if the discharge condition is met, the Q1 is disconnected and the Q2 is closed; if the discharge condition is not met, the Q1 and the Q2 are disconnected, and the next time whether the discharge condition is met is judged after an interval pre-discharge waiting time, and the pre-discharge waiting time is accumulated with the increase of the number of times that the discharge condition is not met. The application judges the secondary pre-discharge by arranging the pre-discharge module, reduces the probability of the discharge switch being mistakenly opened, and improves the reliability of the battery; the pre-discharge waiting time is set to be accumulated gradually, so that the pre-discharge resistor is prevented from being burnt out and the product is prevented from being invalid due to the frequent start of the load in the case of load short circuit.

Description

[0001] This application is a divisional application of the invention application filed on November 10, 2022, with application number 202211403887X and invention title "A Battery Pre-Discharge Control System and Control Method". Technical Field

[0002] This invention relates to the field of battery control, and more particularly to a battery discharge control method and system. Background Technology

[0003] In power supply products, battery discharge is typically controlled by a BMS (Battery Management System) that controls the switching on and off of discharge switches (such as MOSFETs, relays, etc.). However, in the event of an external load short circuit, directly closing the discharge switch can cause a large current surge, which can easily damage the switch, leading to battery discharge control failure and potentially serious consequences.

[0004] The existing solution involves setting up a pre-discharge circuit. Before the discharge switch closes, the pre-discharge circuit outputs a small current to the load through a current-limiting resistor. The voltage across the load is used to determine if there is a short circuit. In the event of a short circuit, the discharge switch is not closed, thus protecting the switch and the battery. However, this solution can easily burn out the current-limiting resistor if the load is continuously short-circuited and the device is repeatedly turned on and off, leading to the failure of the power supply / battery product.

[0005] The above background information is provided only to assist in understanding the inventive concept and technical solution of this invention. It does not necessarily belong to the prior art of this patent application, nor does it necessarily provide technical teaching. In the absence of clear evidence that the above information was disclosed before the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0006] The purpose of this invention is to provide a battery discharge control method and system with a two-stage pre-discharge judgment, which can accurately judge the load status in advance, reduce the probability of the discharge switch being turned on erroneously, and improve the reliability of the BMS.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A battery discharge control method includes the following steps:

[0009] A pre-discharge branch is connected in parallel at both ends of the main discharge branch of the battery. The main discharge branch is equipped with a first controllable switch, and the pre-discharge branch is equipped with a second controllable switch and a resistor.

[0010] Connect the load and sample the terminal voltage of the load;

[0011] With the second controllable switch closed and the first controllable switch open, it is determined whether the terminal voltage of the load meets the discharge conditions. If the discharge conditions are met, the second controllable switch is opened and the first controllable switch is closed. If the discharge conditions are not met, the first and second controllable switches are opened, and the next determination of whether the terminal voltage of the load meets the discharge conditions is performed after a pre-discharge waiting time interval. The pre-discharge waiting time accumulates as the number of times the discharge conditions are not met increases.

[0012] The step of determining whether the terminal voltage of the load meets the discharge condition includes: after closing the second controllable switch, waiting for a preset first time threshold and sampling the current first terminal voltage of the load; if the first terminal voltage is greater than a preset first voltage threshold, waiting for a preset second time threshold and sampling the current second terminal voltage of the load, otherwise the discharge condition is not met; if the second terminal voltage is greater than a preset second voltage threshold, the discharge condition is met, otherwise the discharge condition is not met; wherein, the first time threshold is less than the second time threshold, and the first voltage threshold is less than the second voltage threshold.

[0013] Furthermore, based on any one or a combination of the aforementioned technical solutions, the first time threshold is less than 1 second, and the second time threshold is greater than 1 second.

[0014] Furthermore, based on any one or a combination of the aforementioned technical solutions, the first voltage threshold is between 20% and 45% of the battery voltage, and the second voltage threshold is between 55% and 80% of the battery voltage;

[0015] The first time threshold is between 100 and 550 ms, and the second time threshold is between 1.2 and 4 s.

[0016] Furthermore, following any one or a combination of the aforementioned technical solutions, the terminal voltage of the battery is sampled in real time. If the sampled battery voltage value is lower than the nominal battery voltage, the first voltage threshold is between 20% and 27.5% of the sampled battery voltage value, and the second voltage threshold is between 55% and 60% of the sampled battery voltage value; the first time threshold is between 350 and 500 ms, and the second time threshold is between 1.2 and 2 s.

[0017] Furthermore, if any or a combination of the aforementioned technical solutions does not meet the discharge conditions, the cumulative amplitude of the pre-discharge waiting time is determined based on the number of consecutive failures to meet the discharge conditions, and the current cumulative amplitude is greater than or equal to the previous cumulative amplitude.

[0018] Furthermore, following any one or a combination of the aforementioned technical solutions, the cumulative amplitude of the pre-playback waiting time remains unchanged;

[0019] Alternatively, the higher the number of consecutive times the discharge conditions are not met, the greater the cumulative amplitude of the pre-discharge waiting time;

[0020] Alternatively, if the number of consecutive failures to meet the discharge conditions is between 1 and i, the cumulative amplitude of the pre-discharge waiting time is configured as Δt1; if the number of consecutive failures to meet the discharge conditions is between i+1 and i+j, the cumulative amplitude of the pre-discharge waiting time is configured as Δt2, where i and j are positive integers, and Δt1 is less than Δt2.

[0021] Furthermore, following any one or a combination of the aforementioned technical solutions, the battery discharge control method further includes, after the pre-discharge waiting time is accumulated, determining whether the accumulated pre-discharge waiting time exceeds a preset waiting time limit; if so, issuing a prompt signal and / or stopping the pre-discharge action; otherwise, after an interval of the pre-discharge waiting time, performing the next determination on whether the load terminal voltage meets the discharge conditions.

[0022] According to another aspect of the present invention, a battery discharge control system is provided, including a battery, a main discharge branch, a pre-discharge branch, and a control module. The main discharge branch is connected in series with the battery to form a circuit for supplying power to the load. The pre-discharge branch is connected in parallel across the two ends of the main discharge branch. The main discharge branch is equipped with a first controllable switch, and the pre-discharge branch is equipped with a second controllable switch and a resistor.

[0023] The control module is configured with a voltage sampling unit for sampling the terminal voltage of the load, and the control module is configured to control the first controllable switch and the second controllable switch in the following manner:

[0024] In response to a battery discharge demand command, the system controls the second controllable switch to close and the first controllable switch to open; it determines whether the load's terminal voltage meets the discharge conditions. If the discharge conditions are not met, it controls both the first and second controllable switches to open, accumulates the pre-discharge waiting time, updates and saves the accumulated pre-discharge waiting time, and performs the next determination of whether the load's terminal voltage meets the discharge conditions after an interval of the pre-discharge waiting time.

[0025] If the discharge conditions are met, the second controllable switch is disconnected, the first controllable switch is closed, and the pre-discharge waiting time is reset to its initial value.

[0026] Furthermore, following any one or a combination of the aforementioned technical solutions, the control module determines whether the load's terminal voltage meets the discharge conditions through the following steps:

[0027] Wait for a preset first time threshold and sample the current first terminal voltage of the load;

[0028] If the voltage at the first terminal is greater than a preset first voltage threshold, then wait for a preset second time threshold and sample the current voltage at the second terminal of the load; otherwise, the discharge condition is not met.

[0029] If the voltage at the second terminal is greater than the preset second voltage threshold, then the second controllable switch is controlled to open and the first controllable switch is controlled to close; otherwise, the discharge condition is not met. Wherein, the first time threshold is less than the second time threshold and the first voltage threshold is less than the second voltage threshold.

[0030] Furthermore, following any one or a combination of the aforementioned technical solutions, the system further includes a storage module, and the control module is further configured to:

[0031] The accumulated pre-playback waiting time is stored in the storage module;

[0032] After controlling the second controllable switch to open and the first controllable switch to close, the pre-playing waiting time is reset to the initial value and stored in the storage module;

[0033] And after accumulating the pre-discharge waiting time, determine whether the accumulated pre-discharge waiting time exceeds the preset waiting time limit. If so, drive the alarm to issue a prompt signal and / or stop the pre-discharge action; otherwise, after the pre-discharge waiting time interval, perform the next judgment on whether the terminal voltage of the load meets the discharge conditions.

[0034] The beneficial effects of the technical solution provided by this invention are as follows:

[0035] a. By adding a pre-discharge module and setting a two-stage pre-discharge judgment, the load status can be accurately judged in advance, reducing the probability of the discharge switch being opened falsely and improving the reliability of the BMS;

[0036] b. Set a pre-discharge waiting time and accumulate it to avoid frequent power-on when the load is short-circuited, which could burn out the pre-discharge resistor;

[0037] c. Store the set parameters in the storage module to avoid control logic failure due to data loss after an unexpected power outage. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application 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 recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A schematic diagram of the framework of a battery discharge control system provided for an exemplary embodiment of the present invention;

[0040] Figure 2 A schematic diagram of the circuit structure of a battery discharge control system provided as an exemplary embodiment of the present invention;

[0041] Figure 3 A basic flowchart of a battery discharge control method provided for an exemplary embodiment of the present invention;

[0042] Figure 4 A schematic diagram illustrating the specific process of a battery discharge control method provided in an exemplary embodiment of the present invention. Detailed Implementation

[0043] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0044] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, apparatus, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0045] In one embodiment of the present invention, a battery discharge control system is provided, such as... Figure 1As shown, the system includes a battery, a main discharge branch, a pre-discharge branch, a control module, and a storage module. The main discharge branch is connected in series with the battery to form a power supply loop for the load. The pre-discharge branch is connected in parallel across the two ends of the main discharge branch. In a specific embodiment, as shown... Figure 2 As shown, the main discharge branch is equipped with a first controllable switch, such as a MOS switch Q2, and the pre-discharge branch is equipped with a resistor R1 and a second controllable switch, such as a MOS switch Q1.

[0046] The control module MCU is configured with a terminal voltage V for the load. o The voltage sampling unit performs sampling, and the control module is configured to perform sampling via, for example... Figure 3 The following method controls the on / off state of MOS switches Q1 and Q2:

[0047] When a load is connected, in response to the battery discharge demand command, control Q1 to close and Q2 to open. At this time, the main discharge branch is open, and the battery supplies power to the load through the resistor R1 of the pre-discharge branch.

[0048] The system determines whether the load's terminal voltage meets the discharge conditions. If it does, Q1 is disconnected and Q2 is closed, entering normal discharge mode, where the battery, main discharge branch, and load form a path. If the discharge conditions are not met, Q1 and Q2 are disconnected, and after a pre-discharge waiting time, the system checks whether the load's terminal voltage meets the discharge conditions again. The pre-discharge waiting time accumulates as the number of times the discharge conditions are not met increases. In this embodiment, the load's terminal voltage can be sampled from both ends of the load. Let the sampled battery voltage at one end (i.e., the battery positive terminal and discharge positive terminal) be V1, and the sampled voltage at the other end (i.e., the discharge negative terminal) be V2. The voltage difference between these two ends is defined as the load's terminal voltage.

[0049] In a specific embodiment, such as Figure 4 As shown, in the initial state, both Q1 and Q2 are in the off state. In response to the battery discharge demand command, after a pre-discharge waiting time t, Q1 is controlled to close and Q2 is controlled to open. In this embodiment, the initial value of t is 0s.

[0050] After closing Q1, wait for a preset first time threshold t1, and then sample the load terminal voltage V. o ;

[0051] If the current terminal voltage of the load is V o Not greater than the preset first voltage threshold V o1 If V o Greater than V o1 If so, continue execution:

[0052] After waiting for the preset second time threshold t2, the terminal voltage V of the load is sampled. o ;

[0053] If the current terminal voltage of the load is V o Not greater than the preset second voltage threshold V o2 If V o Greater than V o2 If the discharge condition is met, the pre-discharge branch can be disconnected and the main discharge branch can be connected, i.e., Q1 is disconnected and Q2 is closed, and the pre-discharge waiting time t is reset to zero and the reset pre-discharge waiting time t is stored in the storage module.

[0054] This invention employs a two-stage pre-discharge detection mechanism to improve the accuracy and reliability of load anomaly detection results and reduce the probability of the discharge switch erroneously opening under abnormal load conditions. The two-stage pre-discharge detection consists of a first detection after a millisecond-level time following the closure of Q1 and a second detection after a second-level time. Its detection mechanism is based on the following two scenarios, as determined through experimentation:

[0055] Scenario 1: The load terminal voltage is detected as qualified several hundred milliseconds after the pre-discharge circuit is turned on; however, the terminal voltage is detected as unqualified several seconds after the pre-discharge circuit is turned on, such as 2 seconds later.

[0056] Scenario 2: The load terminal voltage detected several hundred milliseconds after the pre-discharge circuit is turned on is unqualified, but the load terminal voltage detected several seconds after the pre-discharge circuit is turned on is qualified.

[0057] Neither of these two scenarios has been disclosed in existing technology.

[0058] The above-mentioned qualified standard refers to the critical range of the load terminal voltage of a qualified and non-abnormal load of the same specification after the same pre-discharge circuit is connected for a preset time. This critical range can be obtained through multiple tests. If there are obvious noise points in the test results, they need to be eliminated. Then, the test value after eliminating the noise points can be used to determine the qualified range.

[0059] In this embodiment, the first time threshold t1 is between 100 and 550 ms, and the second time threshold t2 is between 1.2 and 4 s. Waiting for t1 is used to determine whether there is a short circuit at the load end, which can effectively limit the overload power of the pre-discharge resistor when the load is short-circuited; the first voltage threshold V o1 Between 20% and 45% of the battery voltage, the second voltage threshold V o2 Between 55% and 80% of the battery voltage; a second assessment effectively improves the accuracy of the assessment results.

[0060] In one specific embodiment, the battery voltage is a fixed value, such as the terminal voltage of a fully charged battery, or the rated voltage (also known as the nominal voltage);

[0061] In another specific embodiment, the battery voltage is a variable, representing the current terminal voltage of the battery when the circuit is open, i.e., the battery voltage sampling value V1 of the aforementioned positive / discharge positive terminal. Accordingly, the system is also configured with a circuit for sampling the battery voltage to sample the battery's terminal voltage in real time. This is to investigate whether different discharge levels of the same battery affect the voltage threshold (V1) used to determine whether the discharge conditions are met. o1 V o2 In experiments setting the standard for the battery voltage, and in experiments investigating whether different discharge levels of the same battery affect the set standard for waiting times t1 and t2 used to determine whether the discharge conditions are met, it was found that when the real-time terminal voltage of the battery is lower than the nominal voltage, even under normal loads, it takes longer to reach 45% of the battery voltage in the first detection stage of the secondary pre-discharge detection compared to when it is higher than the nominal voltage. In the second detection stage, some abnormal loads can also raise the load voltage to 55% of the battery voltage after waiting for 4 seconds. Based on these experimental results, in this embodiment, if the sampled battery voltage value is lower than the nominal battery voltage, the first voltage threshold V... o1 The second voltage threshold V is set to 20% to 27.5% of the current battery voltage sample value. o2 The time threshold is set to 55% to 60% of the current battery voltage sampling value; the first time threshold is between 280 and 500 ms, and the second time threshold is between 1.2 and 2 s. In a further specific embodiment, the rated voltage of the battery pack is 48V, and the resistance of the prevention resistor R1 is between 10 and 30 ohms. When the sampled battery voltage is 47.5V, the first voltage threshold V is set. o1 The voltage is set to 11.8V, and the first voltage threshold V is set. o2The voltage is 27.3V. The first time threshold t1 is set to 450ms, and the second time threshold t2 is set to 1.3s. This embodiment of the invention, through experimental verification, obtains a threshold setting strategy where, when the real-time battery voltage is lower than the nominal battery voltage, and when it is higher than the nominal voltage, the selectable threshold range includes a lower first voltage threshold, a lower second voltage threshold, and a second time threshold, and a higher first time threshold. Here, "lower" and "higher" are defined as follows: for a range with a lower critical value a and an upper critical value b, if the set threshold is less than a + (ba) / 3, then the threshold belongs to a smaller set value within that range; if the set threshold is greater than a + (ba)*2 / 3, then the threshold belongs to a larger set value within that range. This threshold setting method is less prone to false detections and helps to further improve the accuracy and reliability of load anomaly detection results. In addition to storing the pre-amplification waiting time t in the storage module (which can use SPI Flash, which communicates with the control module MCU), the control module can also store the current first voltage threshold V. o1 Second voltage threshold V o2 The set values ​​of the first time threshold t1 and the second time threshold t2 are also stored in the storage module. When the real-time battery voltage changes, the control module updates the set values ​​in the storage module.

[0062] The two-stage pre-discharge detection and judgment mechanism adopted in this invention is defined as follows: if any detection result indicates that the discharge condition is not met, a pre-discharge wait is required to avoid frequent power-on during a load short circuit, which could burn out the pre-discharge resistor. On one hand, the pre-discharge wait time t accumulates with the number of times the discharge condition is not met. For example, if the discharge condition is not met the first time, a 10-second wait is required before the next judgment to determine if the discharge condition is met. If the condition is still not met, a 12-second wait (accumulated amplitude of 2 seconds) is required for a third judgment. The control module stores the accumulated pre-discharge wait time t in the storage module, preventing data loss and control logic failure due to unexpected power outages.

[0063] The pre-amplification waiting time t and the accumulated amplitude can be implemented in different ways:

[0064] Method 1: The amplitude accumulated during the pre-amplification waiting time t remains constant each time;

[0065] Method 2: The higher the number of consecutive times the discharge conditions are not met, the greater the cumulative amplitude of the pre-discharge waiting time t.

[0066] Method 3: Increase the cumulative amplitude of each iteration in a stepwise manner as the number of consecutive failures to meet the discharge conditions increases. For example, for the first 4 consecutive failures to meet the discharge conditions, the cumulative amplitude of each iteration of the pre-discharge waiting time t is 3s; for the 5th to 10th consecutive failures to meet the discharge conditions, the cumulative amplitude of each iteration of the pre-discharge waiting time t is 10s; and from the 11th consecutive failure to meet the discharge conditions onwards, the cumulative amplitude of each iteration of the pre-discharge waiting time t is 30s.

[0067] In one embodiment, a waiting time limit T (e.g., 5 minutes) is set for the pre-discharge waiting time t. When t accumulates to exceed the upper limit T, the next judgment on whether the discharge condition is met will not be performed. That is, after the pre-discharge waiting time is accumulated, the control module judges whether the accumulated pre-discharge waiting time t exceeds the preset waiting time limit T. If it does, the alarm will be driven to issue a prompt signal and / or the pre-discharge action will be stopped. If the limit T is not reached, the next judgment on whether the load terminal voltage meets the discharge condition will be performed after an interval of the accumulated pre-discharge waiting time t.

[0068] In one embodiment of the present invention, there may be multiple resistors in the pre-discharge branch to prevent the pre-discharge function from failing when one of the resistors R1 is short-circuited; or, the terminal voltage of the resistor R1 in the pre-discharge branch may be sampled to analyze whether the resistor R1 is damaged by the sampling result of the terminal voltage of the resistor R1.

[0069] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0070] The above description is only a specific embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A battery discharge control method, characterized in that, Includes the following steps: A pre-discharge branch is connected in parallel at both ends of the main discharge branch of the battery. The main discharge branch is equipped with a first controllable switch, and the pre-discharge branch is equipped with a second controllable switch and a resistor. Connect the load and sample the terminal voltage of the load; With the second controllable switch closed and the first controllable switch open, it is determined whether the terminal voltage of the load meets the discharge conditions. If the discharge conditions are met, the second controllable switch is opened and the first controllable switch is closed. If the discharge conditions are not met, the first and second controllable switches are opened, and the next determination of whether the terminal voltage of the load meets the discharge conditions is performed after a pre-discharge waiting time interval. The pre-discharge waiting time accumulates as the number of times the discharge conditions are not met increases. The step of determining whether the terminal voltage of the load meets the discharge condition includes: after closing the second controllable switch, waiting for a preset first time threshold and sampling the current first terminal voltage of the load; if the first terminal voltage is greater than a preset first voltage threshold, waiting for a preset second time threshold and sampling the current second terminal voltage of the load, otherwise the discharge condition is not met; if the second terminal voltage is greater than a preset second voltage threshold, the discharge condition is met, otherwise the discharge condition is not met; wherein, the first time threshold is less than the second time threshold, and the first voltage threshold is less than the second voltage threshold.

2. The battery discharge control method according to claim 1, characterized in that, The first time threshold is less than 1 second, and the second time threshold is greater than 1 second.

3. The battery discharge control method according to claim 1, characterized in that, The first voltage threshold is between 20% and 45% of the battery voltage, and the second voltage threshold is between 55% and 80% of the battery voltage; The first time threshold is between 100 and 550 ms, and the second time threshold is between 1.2 and 4 s.

4. The battery discharge control method according to claim 3, characterized in that, The battery terminal voltage is sampled in real time. If the sampled battery voltage value is lower than the battery nominal voltage, the first voltage threshold is between 20% and 27.5% of the sampled battery voltage value, and the second voltage threshold is between 55% and 60% of the sampled battery voltage value. The first time threshold is between 350 and 500 ms, and the second time threshold is between 1.2 and 2 s.

5. The battery discharge control method according to claim 1, characterized in that, If the discharge conditions are not met, the cumulative amplitude of the pre-discharge waiting time is determined based on the number of consecutive times the discharge conditions are not met, and the current cumulative amplitude is greater than or equal to the previous cumulative amplitude.

6. The battery discharge control method according to claim 5, characterized in that, The cumulative amplitude of the pre-playback waiting time remains unchanged; Alternatively, the higher the number of consecutive times the discharge conditions are not met, the greater the cumulative amplitude of the pre-discharge waiting time; Alternatively, if the number of consecutive failures to meet the discharge conditions is between 1 and... i Then the cumulative amplitude of the pre-playback waiting time is configured as Δ t 1 If the number of consecutive times the discharge condition is not met is between i +1 to i+j Then the cumulative amplitude of the pre-playback waiting time is configured as Δ t 2 ,in, i, j For positive integers, △ t 1 Less than △ t 2 .

7. The battery discharge control method according to any one of claims 1 to 6, characterized in that, The method also includes determining whether the accumulated pre-discharge waiting time exceeds a preset waiting time limit after the pre-discharge waiting time has been accumulated. If so, a prompt signal is issued and / or the pre-discharge action is stopped; otherwise, the pre-discharge waiting time is intermittent before determining whether the load terminal voltage meets the discharge conditions.

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