Battery module insulation detection short circuit prevention circuit

Abstract

The utility model relates to a battery module insulation detection short circuit prevention circuit, which comprises a battery cluster, an external circuit and a casing ground PE, the battery cluster is composed of a plurality of battery modules connected in series, and the battery cluster is communicated with the external circuit to form a loop; the external circuit is connected to the case ground PE; the outer surface of each battery module is coated with a metal shell, and a high-resistance resistor RP is connected in series between the metal shell of each battery module and the case ground PE. According to the utility model, the high-resistance resistor RP is connected in series between the metal shell of each battery module and the shell ground PE, so that the total impedance of an electric leakage loop is greatly increased by introducing the high-resistance resistor RP, and a low-impedance short-circuit path between the battery cells is blocked through the high-resistance characteristic. Even if the plurality of battery modules leak electricity, the leakage current only flows to the PE through the RP resistor, and a direct loop is not formed among the battery cells, so that the short circuit of the battery cells is avoided, and a loop large current cannot be formed among the battery cells of the leakage battery module. And the risk that the battery module is burnt is effectively reduced.

Description

Technical Field

[0001] This utility model belongs to the field of battery management technology, and specifically relates to a short-circuit protection circuit for battery module insulation detection. Background Technology

[0002] In insulation testing of battery clusters, traditional insulation testing typically connects the battery module casing directly to the housing ground (PE), such as... Figure 1 As shown, when a single battery module leaks current, the insulation detection circuit can determine the fault by detecting the leakage current. However, if two or more battery modules leak current simultaneously, the leakage current will form a short-circuit loop through the external PE line (Rx→PE→Ry), causing a large current to flow through the cells of the leaking battery module, resulting in a short circuit between the cells and generating a large current, thus posing a risk of battery module burnout. Furthermore, when the cells of the leaking battery module short-circuit, the large current generated will rapidly produce Joule heat inside the battery module, causing the cell temperature to rise sharply. When the temperature exceeds a critical value, it may trigger a chain reaction such as electrolyte decomposition and separator melting, ultimately causing thermal runaway and even open flames. Therefore, the danger is extremely high.

[0003] Due to the low impedance characteristics of the short-circuit path, the direct connection of the PE line means that the equivalent resistance of the leakage circuit is determined solely by the leakage resistances Rx and Ry. These leakage resistances are typically small (especially in humid or polluted environments, they can be as low as several hundred ohms), making it impossible to effectively suppress the short-circuit current. Furthermore, traditional solutions do not incorporate any current-limiting components (such as high-resistance resistors or fuses), leaving the leakage current entirely dependent on the natural limitation of the leakage resistance. However, the leakage resistance is uncontrollable and can dynamically change due to environmental factors, making it difficult to guarantee safety. Insulation testing relies on the grounding path, which itself becomes a source of short-circuit risk. Existing solutions cannot dynamically block dangerous currents during testing, creating a contradictory situation where "testing itself is a risk."

[0004] Therefore, there is an urgent need for a protection solution that can prevent the formation of a large current loop between the cells of a leaky battery module. Utility Model Content

[0005] The purpose of this invention is to provide a short-circuit protection circuit for insulation detection of battery modules, which can significantly improve safety and reliability in scenarios with multiple battery modules leaking current, prevent the formation of a large current loop between the cells of the leaking battery module, and effectively reduce the risk of the battery module being burned out.

[0006] This invention provides a short-circuit protection circuit for battery module insulation detection, including a battery cluster, an external circuit, and a housing ground (PE). The battery cluster consists of several battery modules connected in series and forms a loop with the external circuit. The external circuit is connected to the housing ground (PE). Each battery module is covered with a metal casing, and a high-resistance resistor RP is connected in series between the metal casing of each battery module and the housing ground (PE). By connecting the high-resistance resistor RP in series between the metal casing of each battery module and the housing ground (PE), the total impedance of the leakage circuit is significantly increased. The high resistance characteristic blocks the low-impedance short-circuit path between the battery cells. Even if multiple battery modules leak, the leakage current flows only to the PE through the RP resistor, without forming a direct loop between the battery cells, thus avoiding short circuits between the cells. Therefore, it fundamentally changes the path characteristics of the leakage current, thereby significantly improving safety and reliability in multi-battery module leakage scenarios.

[0007] Preferably, the external circuit includes, in sequence, a resistor R1, a switch K1, a resistor R2, a resistor R3, a switch K2, and a resistor R4. A branch circuit is connected between resistors R2 and R3 and then to the chassis ground. This branch circuit, connected to the battery holder's metal casing, creates multiple loops in the external circuit, facilitating the acquisition of data from each loop under different connection states and enabling rapid detection.

[0008] Preferably, resistor R2 is connected to analog-to-digital converter ADC1, and resistor R3 is connected to analog-to-digital converter ADC2. The leakage resistance value can be quickly calculated using analog-to-digital converters ADC1 and ADC2.

[0009] This utility model has the following technical effects:

[0010] 1. By connecting a high-resistance resistor RP in series between the metal casing of each battery module and the PE (protected earth) of the casing, the total impedance of the leakage circuit is significantly increased due to the introduction of the high-resistance resistor RP. This high resistance characteristic blocks the low-impedance short-circuit path between the cells. Even if multiple battery modules leak, the leakage current flows only to PE through the RP resistor, without forming a direct loop between the cells, thus preventing short circuits and preventing the formation of a large current loop between the cells of the leaking battery module. This fundamentally changes the path characteristics of the leakage current, thereby significantly improving safety and reliability in multi-battery module leakage scenarios and effectively reducing the risk of battery module burnout.

[0011] 2. The structure of connecting the external circuit to the metal shell of the battery holder through the branch circuit makes it possible to form multiple loops, which facilitates the acquisition of corresponding data under different connection states of each loop and realizes rapid detection.

[0012] 3. The leakage resistance value can be quickly calculated using analog-to-digital converters ADC1 and ADC2. Attached Figure Description

[0013] Figure 1 This is a circuit block diagram for traditional insulation testing.

[0014] Figure 2 This is the circuit block diagram for Example 1;

[0015] Figure 3 This is the circuit block diagram for Example 2. Detailed Implementation

[0016] To make the objectives, technical solutions and advantages of this utility model clearer, the following detailed description of this utility model is provided in conjunction with the accompanying drawings.

[0017] Example 1

[0018] like Figure 2 As shown, a battery module insulation detection and short-circuit protection circuit includes a battery cluster, an external circuit, and a housing ground (PE). The battery cluster consists of several battery modules connected in series and forms a loop with the external circuit. The external circuit is connected to the housing ground (PE). Each battery module is covered with a metal casing, and a high-resistance resistor RP is connected in series between the metal casing of each battery module and the housing ground (PE). By connecting the high-resistance resistor RP in series between the metal casing of each battery module and the housing ground (PE), the total impedance of the leakage circuit is significantly increased. The high resistance characteristic blocks the low-impedance short-circuit path between the battery cells. Even if multiple battery modules leak, the leakage current flows only to the PE through the RP resistor and does not form a direct loop between the battery cells, thus avoiding short circuits between the cells. Therefore, the path characteristics of the leakage current are fundamentally changed, thereby significantly improving safety and reliability in multi-battery module leakage scenarios.

[0019] The external circuit is sequentially equipped with resistor R1, switch K1, resistor R2, resistor R3, switch K2, and resistor R4. A branch circuit is connected between resistors R2 and R3 and then to the chassis ground. This branch circuit, connected to the battery holder's metal casing, creates multiple loops in the external circuit, facilitating the acquisition of data from each loop under different connection states and enabling rapid detection.

[0020] Example 2

[0021] like Figure 3 As shown, this embodiment, based on embodiment 1, connects analog-to-digital converter ADC1 to resistor R2 and analog-to-digital converter ADC2 to resistor R3. The leakage resistance value is quickly calculated using analog-to-digital converters ADC1 and ADC2.

[0022] The leakage resistance value can be calculated using the unbalanced bridge method and an alarm can be uploaded. The calculation method is as follows:

[0023] When a point (point C) in the battery pack leaks current from the metal casing of the battery module, there is a resistance Rx, and the resistance value of the resistance Rx is denoted as Rx.

[0024] A and D are the positive and negative terminals of the battery cluster, respectively. The voltage of the battery cluster is denoted as U, and the voltage between A and C is denoted as Uc. AC The voltage between C and D is denoted as U. CD The resistance value of resistor R1 is denoted as R1, the resistance value of resistor R2 is denoted as R2, the resistance value of resistor R3 is denoted as R3, the resistance value of resistor R4 is denoted as R4, and the resistance value of the large resistance resistor RP is denoted as RP.

[0025] When switch K1 is closed and switch K2 is open, the voltage sampled by the upper bridge arm of analog-to-digital converter ADC1 is recorded as U. R2 ,but

[0026]

[0027] When switch K1 is open and switch K2 is closed, the voltage sampled by the lower bridge arm of analog-to-digital converter ADC2 is recorded as U. R3 ,but

[0028]

[0029] And U AC +U CD =U(3),

[0030] R1=R4,R2=R3 (4),

[0031] Combining (1), (2), (3), and (4), we can obtain:

[0032] Solving

[0033] Resistors R1 and R4 are both 5MΩ, resistors R2 and R3 are both 3kΩ, the large-value resistor RP is 2MΩ, and the total voltage U is 1300V. R2 +U R3 =0.4V;

[0034] Substituting into ⑤, we can solve for:

[0035] In summary, based on the acquired ADC value, the resistance of resistor Rx can be calculated to be 2.747 MΩ.

[0036] The embodiments described above are merely preferred embodiments of the present utility model and are not intended to limit the scope of the present utility model. Various modifications and improvements made to the technical solutions of the present utility model by those skilled in the art without departing from the spirit of the present utility model should fall within the protection scope defined by the claims of the present utility model.

Claims

1. A short-circuit protection circuit for insulation detection of a battery module, characterized in that: It includes a battery cluster, an external circuit, and a chassis ground. The battery cluster consists of several battery modules connected in series and is connected to the external circuit to form a loop. The external circuit is connected to the chassis ground. The battery modules are covered with a metal casing, and a large-value resistor RP is connected in series between the metal casing of each battery module and the chassis ground PE.

2. The battery module insulation detection and short-circuit protection circuit according to claim 1, characterized in that, The external circuit is provided with resistor R1, switch K1, resistor R2, resistor R3, switch K2, and resistor R4 in sequence. A branch circuit is connected between resistor R2 and resistor R3 and then connected to the chassis ground.

3. The battery module insulation detection and short-circuit protection circuit according to claim 2, characterized in that, The resistor R2 is connected to the analog-to-digital converter ADC1, and the resistor R3 is connected to the analog-to-digital converter ADC2.

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