Conversion system and method for parallel input and output of positive and negative battery packs

Abstract

The invention relates to a system and a method for converting parallel input and output of positive and negative assembled batteries, which are applied to a special vehicle powered by the positive and negative assembled batteries, and are characterized in that the positive and negative assembled batteries respectively supply power to positive and negative assembled loads during normal work; the parallel input and output of the positive and negative batteries can be realized by operating the change-over switch on the instrument board, and meanwhile, the load connected with the original negative battery is cut off, so that the safety during parallel connection is ensured, and the influence on the load is avoided; when the original vehicle main switch is independently turned on, the electric equipment on the vehicle can keep the original vehicle electric state unchanged; when the change-over switch and the main switch are switched on simultaneously, only the positive battery pack is kept to supply power to the vehicle, and the safety of series-parallel connection switching of the positive and negative battery packs is ensured through the self-locking design.

Description

Technical Field

[0001] The present invention belongs to the technical field of power distribution management and control of special vehicles, and in particular relates to a system and method for parallel connection of battery packs. Background Art

[0002] In order to meet the power demand of high-power equipment, some special vehicles use a 48V power supply system, which is composed of positive and negative 24V power supplies connected in series. The positive and negative 24V power supplies can respectively power the 24V electrical equipment on the vehicle, and high-power equipment can also be powered by the 48V power supply connected in series. Figure 1 The original vehicle circuit is shown. When the vehicle main switch is not turned on, the negative pole of the positive battery is connected to one end of the J1 contactor contact, and the positive pole of the negative battery is connected to one end of the J2 contactor contact. The J1 and J2 contactors are not energized, and the positive and negative battery groups are both suspended and not output. The main distribution box has no power output. When the main switch is turned on, the J1 and J2 contactor coils are powered by the positive battery group, the contactor contacts are energized, the negative pole of the positive battery group and the positive pole of the negative battery group are connected to the vehicle body, and the vehicle body is connected in series. The main distribution box can provide three power supply systems: -24V, 24V and 48V.

[0003] However, in actual use, it was found that this power supply circuit has the following problems. First, when the vehicle is used in a low-temperature environment, a heating and standby function is added to achieve rapid starting of the vehicle, but the heater is only provided by the positive battery group. Due to the limitation of the capacity of the positive battery group, it cannot support the vehicle's long-term heating and standby conditions, and cannot give full play to the actual power supply capacity of the vehicle; second, the discharge frequency and depth of the positive battery group are greater than those of the negative battery group. After the positive and negative batteries are connected in series, the overall output performance of the battery is also affected to a certain extent; third, when charging the vehicle, the positive and negative batteries need to be charged separately, and the charging time is relatively long. The charging device cannot be used with other models, and the equipment support performance is affected. Summary of the invention

[0004] In view of this, the present invention proposes a system and method for converting the input and output of a positive and negative battery group in parallel. The present invention adds a conversion device, and can safely and conveniently realize the output conversion of the positive and negative battery groups in series and parallel only by using an operating switch.

[0005] The specific technical solutions are as follows:

[0006] A positive and negative battery group parallel input and output conversion system is applied to special vehicles powered by positive and negative battery groups, including an instrument panel, a contactor J1, and a contactor J2. The instrument panel is provided with a main switch, and the main switch controls the contactors J1 and J2. J1 controls the negative electrode of the positive battery group to be connected to the vehicle body, and J2 controls the positive electrode of the negative battery group to be connected to the vehicle body. When the main switch is closed, the positive and negative battery groups are connected in series. A conversion switch is added to the instrument panel for parallel operation of the positive and negative battery groups; a conversion device is added to realize parallel connection of the positive and negative battery groups; the conversion device includes a grid-connected contactor CJ1 1, a grid-connected contactor CJ2, a negative group 1 contactor CJ3, a main switch relay CJ4, and a conversion relay CJ5.

[0007] Furthermore, the main switch relay CJ4 is used to control the grid-connected contactor 1 CJ1 and the grid-connected contactor 2 CJ2, so that the positive and negative battery groups are switched between parallel and series states.

[0008] Furthermore, the switching relay CJ5 is used to control the grid-connected contactor 2 CJ2 and the negative group 1 contactor CJ3, and control the connection state of the positive and negative electrodes of the negative group battery.

[0009] Furthermore, the main switch relay CJ4 and the change-over relay CJ5 are in the form of contacts being connected in series with the same line package.

[0010] Furthermore, the grid-connected 1 contactor CJ1 and the grid-connected 2 contactor CJ2 are used to realize the grid connection of the positive and negative battery groups, and the negative group 1 contactor CJ3 is used to realize the negative electrode output control of the negative battery group.

[0011] Furthermore, multiple freewheeling diodes are set up, and CJ1, CJ2, CJ3, CJ4, and CJ5 are respectively connected in parallel with the freewheeling diodes to provide a discharge circuit for the self-inductance electromotive force generated by the relay and the contactor when they are turned on or off; an anti-reverse diode is set between the instrument panel and the conversion device to suppress reverse current.

[0012] A method for parallel input and output of positive and negative battery groups. When the main switch is disconnected and the newly added conversion switch is connected separately, the negative battery group is connected in parallel to the two ends of the positive battery group, and the load connected to the original negative battery group is cut off at the same time. The working process is as follows: the main switch relay CJ4 does not work, the contact is normally closed, the conversion switch outputs to the grid connection 1 contactor CJ1, the CJ1 contactor is turned on, and the positive electrode of the negative battery group is connected to the positive electrode of the positive battery group; the conversion switch outputs to the grid connection 2 contactor CJ2, the CJ2 contactor is turned on, and the negative electrode of the positive battery group is connected to the negative electrode of the negative battery group; the conversion switch outputs to the conversion relay CJ5, CJ5 works, the normally closed contact is disconnected, the negative group 1 contactor CJ3 is disconnected, and the negative electrode output of the negative battery group is disconnected; the main switch is disconnected, J1 and J2 are disconnected, the negative electrode of the positive battery group is disconnected from the vehicle body, and the positive electrode of the negative battery group is disconnected from the vehicle body.

[0013] Furthermore, the positive and negative battery groups jointly power the heater.

[0014] Furthermore, when the newly added conversion switch is disconnected and the main switch is turned on alone, the operation of the electrical equipment on the vehicle remains the same as the original vehicle model. The working process is that the main switch outputs to J1, the J1 contactor is turned on, and the negative pole of the positive battery group is connected to the vehicle body; the CJ5 contactor does not work, and the contacts are normally closed, the main switch outputs to the J2 contactor coil, the J2 contactor is turned on, and the positive pole of the negative battery group is connected to the vehicle body; the main switch outputs to CJ3, the CJ3 contactor works, the contacts are turned on, and the negative pole of the negative battery group is output to the distribution box -24V; the main switch outputs to CJ4, the CJ4 contactor works, the contacts are disconnected, and CJ1 and CJ2 are disconnected; the positive pole of the positive battery group is output to the distribution box +24V, the positive and negative battery groups are in series, and the distribution outputs positive and negative 24V.

[0015] Furthermore, when the main switch is turned on and the transfer switch is turned on, the J1 contactor is turned on, and the negative pole of the positive battery group is connected to the vehicle body; the J2 contactor does not work, and the positive pole of the negative battery group is disconnected from the vehicle body; the CJ4 and CJ5 contactors work, and the two contactor contacts are disconnected; CJ1, CJ2, and CJ3 all do not work; the positive pole of the positive battery group is output to the main distribution box, and the negative pole of the negative battery group is disconnected, leaving only the positive battery group to power the vehicle.

[0016] Beneficial Effects

[0017] 1. Through the present invention, when the newly added conversion switch is turned on separately, the negative battery group is connected in parallel to both ends of the positive battery group, and the positive and negative batteries can jointly power the heater, while the load connected to the original negative battery group is cut off, thereby ensuring safety during parallel connection and avoiding the impact on the negative battery group load;

[0018] 2. Through the present invention, when the main switch of the original vehicle is turned on alone, the operation of the electrical equipment on the vehicle can remain unchanged in the same state as the original vehicle model;

[0019] 3. According to the present invention, after the conversion switch or the main switch is turned on separately, when another switch is turned on due to misoperation, both the positive and negative battery groups are disconnected, and the safety of the series-parallel switching of the positive and negative battery groups is ensured by the self-locking design;

[0020] 4. Through the present invention, after the two switches are connected, disconnecting either switch can automatically execute the currently maintained operation to meet the final operation intention of the occupant.

[0021] 5. The newly added control circuit does not affect the working functions and performance of the original vehicle, and can also meet the needs of heating duty and parallel charging. While ensuring the safety of use, it improves the low-temperature starting performance of the whole vehicle, increases the charging rate and guarantees performance.

[0022] 6. The newly added control circuit of the present invention does not affect the working functions and performance of the original vehicle, and can also meet the use requirements of heating duty and parallel unified charging, while ensuring the safety of use, improving the low-temperature starting performance of the whole vehicle, increasing the charging rate and guaranteeing performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Working principle diagram of the positive and negative battery packs of the original vehicle.

[0024] Figure 2 The working principle diagram of positive and negative group parallel input and output can be realized. DETAILED DESCRIPTION

[0025] The present invention provides a system and method for parallel input and output of positive and negative battery groups. The method for parallel input and output of positive and negative battery groups is applied to special vehicles powered by positive and negative battery groups; the special vehicle needs to add a conversion switch on the dashboard for parallel operation of positive and negative battery groups; the special vehicle needs to add a conversion device to realize parallel connection of positive and negative battery groups. The connection relationship between interfaces X1 and X2 in the dashboard and the original circuit remains unchanged, and a new interface X3 is added. Interface X2 outputs a control signal in parallel and is connected to interface X1 of the conversion device together with interface X3, and the switch control signal is output to the conversion device; the new interface X2 in the conversion device is connected to the main distribution box to provide -24V power output; the new interfaces X3, X4, X5, and X6 in the conversion device are respectively connected to the positive and negative poles of the positive and negative battery groups to realize output conversion of the positive and negative battery groups.

[0026] A conversion device is newly added to the dashboard of the original vehicle, which mainly realizes the operation of connecting the positive battery group and the negative battery group in parallel.

[0027] The conversion device includes grid-connected contactor 1 CJ1, grid-connected contactor 2 CJ2, negative group 1 contactor CJ3, main switch relay CJ4, and conversion relay CJ5.

[0028] The main switch relay CJ4 in the conversion device mainly controls the grid-connected contactor CJ1 and the grid-connected contactor CJ2, so that the positive and negative battery groups are switched between parallel and series states.

[0029] The conversion relay CJ5 mainly realizes the control of the grid-connected contactor 2 CJ2 and the negative group 1 contactor CJ3, and controls the connection status of the positive and negative electrodes of the negative group battery;

[0030] The main switch relay CJ4 and the conversion relay CJ5 adopt the form of contacts connected in series with the same coil package, that is, the external connections of the two relays are in the form of their respective contacts connected in series with the coil package of another relay, that is, if one of the contacts is disconnected, the coil package control line of the other relay is also disconnected, which mainly realizes the mutual exclusion of the main switch relay CJ4 and the conversion relay CJ5 to avoid simultaneous operation of the switches, resulting in the positive and negative battery short circuit fault caused by the conversion of the grid 1 contactor CJ1, the grid 2 contactor CJ2, and the negative group 1 contactor CJ3, and can realize the use requirement of only executing the current operation;

[0031] Grid-connected contactor 1 CJ1 and grid-connected contactor 2 CJ2 are mainly used to connect the positive and negative battery groups to the grid;

[0032] Negative group 1 contactor CJ3 is mainly used to control the negative output of the negative group battery to prevent the negative group battery from affecting the -24V load after being connected in parallel;

[0033] The freewheeling diodes D1, D2, D3, D4, and D5 are mainly used to provide a discharge circuit for the self-inductance electromotive force generated when the relays and contactors are turned on or off, so as to avoid the influence of the reverse electromotive force on other circuits or components; the anti-reverse diodes D6 and D7 are mainly used to suppress the reverse current and prevent the reverse current from affecting the control circuit.

[0034] There are two normal working states of this system. First, turn on the conversion switch and turn off the main switch to realize the parallel connection of positive and negative battery groups; second, turn off the conversion switch and turn on the main switch to keep the original car connection state, that is, Figure 1 In addition, considering the actual operation situation, it is possible that both the transfer switch and the main switch are turned on. In order to ensure the safety and stability of the system, the present invention designs a working mode for this extreme situation.

[0035] When the main switch is disconnected and the newly added conversion switch is turned on separately, the negative group battery is connected in parallel to both ends of the positive group battery, and the load connected to the original negative group battery is cut off at the same time; the working process is that the main switch relay CJ4 does not work, the contacts are normally closed, the conversion switch outputs to the grid connection 1 contactor CJ1, the CJ1 contactor is turned on, and the positive electrode of the negative group battery is connected to the positive electrode of the positive group battery; the conversion switch outputs to the grid connection 2 contactor CJ2, the CJ2 contactor is turned on, and the negative electrode of the positive group battery is connected to the negative electrode of the negative group battery; the conversion switch outputs to the conversion relay CJ5, CJ5 works, the normally closed contact is disconnected, the negative group 1 contactor CJ3 is disconnected, and the negative electrode output of the negative group battery is disconnected; the main switch is disconnected, J1 and J2 are disconnected, the negative electrode of the positive group battery is disconnected from the vehicle body, and the positive electrode of the negative group battery is disconnected from the vehicle body.

[0036] When the newly added conversion switch is disconnected and the main switch is turned on alone, the operation of the electrical equipment on the vehicle remains the same as the original vehicle model. The working process is as follows: the main switch outputs to J1, the J1 contactor is turned on, and the negative pole of the positive battery group is connected to the vehicle body; the CJ5 contactor does not work, and the contacts are normally closed, the main switch outputs to the J2 contactor coil, the J2 contactor is turned on, and the positive pole of the negative battery group is connected to the vehicle body; the main switch outputs to CJ3, the CJ3 contactor works, the contacts are turned on, and the negative pole of the negative battery group is output to the distribution box -24V; the main switch outputs to CJ4, the CJ4 contactor works, the contacts are disconnected, and CJ1 and CJ2 are disconnected; the positive pole of the positive battery group is output to the distribution box +24V, the positive and negative battery groups are in series, and the distribution outputs positive and negative 24V.

[0037] When the main switch is turned on and the transfer switch is turned on, the J1 contactor is turned on, and the negative pole of the positive battery is connected to the vehicle body; the J2 contactor does not work, and the positive pole of the negative battery is disconnected from the vehicle body; the CJ4 and CJ5 contactors work, and the two contactor contacts are disconnected; CJ1, CJ2, and CJ3 do not work; the positive pole of the positive battery is output to the main distribution box, and the negative pole of the negative battery is disconnected, leaving only the positive battery to power the vehicle.

[0038] The following is an explanation of the various states according to the order of switch actions:

[0039] Step 1: Close the dashboard main switch, the positive pole of the positive battery group is output to the J1 contactor coil, the J1 contactor is energized, and the negative pole of the positive battery group is connected to the vehicle body; the positive pole of the positive battery group is output to the J2 contactor coil through the diode D6 and the closed contact of the conversion relay CJ5, the J2 contactor is energized, and the positive pole of the negative battery group is connected to the vehicle body; the positive pole of the positive battery group is output to the negative group 1 contactor coil CJ3 through the diode D6, CJ3 is energized, and the negative pole of the negative battery group is output to the distribution box, and the distribution box outputs both +24V and -24V. This can achieve the original vehicle main switch power-on function remains unchanged.

[0040] Step 2: Disconnect the main switch of the dashboard, J1, J2 and CJ3 will not work, and the positive battery group will not be connected with the negative battery group. Turn on the conversion switch, and the positive electrode of the positive battery group will be output to the coils of parallel contactor CJ1 and parallel contactor CJ2 through diode D7 and the closed contact of the main switch relay CJ4. CJ1 and CJ2 will be attracted, and the positive electrode of the positive battery group will be connected with the positive electrode of the negative battery group, and the negative electrode of the positive battery group will be connected with the negative electrode of the negative battery group. The positive and negative batteries will be output in parallel to the main distribution box +24V, and -24V will not be output. The positive and negative battery group heating and parallel charging functions can be realized, and the influence of the negative battery group on the -24V electrical equipment after parallel connection can be shielded.

[0041] Step 3: Turn on the main switch of the dashboard and then the conversion switch. The positive pole of the positive battery is output to the coil of the conversion relay CJ5 through the diode D7. CJ5 is disconnected, the J2 contactor is disconnected, and the positive pole of the negative battery is disconnected from the vehicle body; the negative contactor CJ3 is disconnected, and the negative pole of the negative battery is disconnected from the -24V output of the main distribution box. The contacts of contactors CJ1, CJ2, and CJ3 are all disconnected. At this time, the J1 contactor is energized, and only the positive battery of the vehicle is output to the main distribution box, which can avoid the short-circuit fault of the series-parallel conversion of the positive and negative batteries.

[0042] Step 4: Turn on the transfer switch and then the main switch. The positive pole of the positive battery is output to the coil of the main switch relay CJ4 through the diode D6. CJ4 is disconnected, and the parallel contactors CJ1 and CJ2 are disconnected. The positive pole of the positive battery is disconnected from the positive pole of the negative battery, and the negative pole of the negative battery is disconnected from the negative pole of the positive battery. The contacts of contactors CJ1, CJ2, and CJ3 are all disconnected. At this time, the J1 contactor is energized, and only the positive battery of the vehicle is output to the main distribution box, which can avoid the short-circuit fault of the series-parallel conversion of the positive and negative batteries.

[0043] Step 5: Turn on the transfer switch and then the main switch, and then turn off the main switch. The main switch relay CJ4 changes from the disconnected state to the attracted state, and the contactors CJ1 and CJ2 are turned on. The positive pole of the positive battery group is connected to the positive pole of the negative battery group, and the negative pole of the positive battery group is connected to the negative pole of the negative battery group; the J1 contactor changes from the attracted state to the disconnected state, and the negative pole of the positive battery group is disconnected from the vehicle body. The positive and negative battery groups are output in parallel to the main distribution box +24V. The transfer switch operation function can be executed, and the short-circuit fault of the series-parallel connection conversion of the positive and negative battery groups can be avoided. When one of the operations is turned off, it can be automatically converted to the current operation that is still maintained, realizing the heating and parallel charging functions of the positive and negative battery groups.

[0044] Step 6: Turn on the transfer switch and then the main switch, then turn off the transfer switch, the transfer relay CJ5 changes from the disconnected state to the attracted state, the contactor CJ3 is attracted, and the negative pole of the negative battery group is output to the -24V of the main distribution box; the J1 and J2 contactors are attracted, the positive pole of the negative battery group is connected to the negative pole of the positive battery group through the vehicle body, and the distribution box outputs +24V and -24V. The main switch operation function can be executed, and the short-circuit fault of the series-parallel connection conversion of the positive and negative battery groups can be avoided. When one of the operations is turned off, it can automatically switch to the current operation that is still maintained to achieve +24V, -24V output.

[0045] Step 7: Turn on the main switch and then the transfer switch, then turn off the transfer switch, the transfer relay CJ5 changes from the disconnected state to the attracted state, the contactor CJ3 is attracted, the negative pole of the negative battery group is output to the -24V of the main distribution box; the J1 and J2 contactors are attracted, the positive pole of the negative battery group is connected to the negative pole of the positive battery group through the vehicle body, and the distribution box outputs +24V and -24V. The main switch operation function can be executed, and the short-circuit fault of the series-parallel connection conversion of the positive and negative battery groups can be avoided. When one of the operations is turned off, it can automatically switch to the current operation that is still maintained to achieve +24V, -24V output.

[0046] Step 8: Turn on the main switch and then the transfer switch, and then turn off the main switch. The main switch relay CJ4 changes from the disconnected state to the attracted state, and the contactors CJ1 and CJ2 are turned on. The positive pole of the positive battery group is connected to the positive pole of the negative battery group, and the negative pole of the positive battery group is connected to the negative pole of the negative battery group; the J1 contactor changes from the attracted state to the disconnected state, and the negative pole of the positive battery group is disconnected from the vehicle body. The positive and negative battery groups are output in parallel to the main distribution box +24V. The transfer switch operation function can be executed, and the short-circuit fault of the series-parallel connection conversion of the positive and negative battery groups can be avoided. When one of the operations is turned off, it can be automatically converted to the current operation that is still maintained, realizing the heating and parallel charging functions of the positive and negative battery groups.

[0047] The present invention is applied to special vehicles powered by positive and negative battery groups. By adding a conversion switch and a conversion device, the conversion switch on the dashboard is operated without changing the original vehicle operation, function and performance to achieve parallel input and output of the positive and negative battery groups. When the two switches work at the same time, the current operation can be automatically executed to avoid short-circuit faults in the process of battery series and parallel connection, and the parallel connection of the negative battery group will not affect the original -24V electrical equipment.

Claims

1. A positive and negative battery parallel input and output conversion system, applied to special vehicles powered by positive and negative batteries, including a dashboard, a contactor J1, a contactor J2, wherein: The dashboard is provided with a main switch, which controls contactors J1 and J2. J1 controls the negative electrode of the positive battery group to be connected to the vehicle body, and J2 controls the positive electrode of the negative battery group to be connected to the vehicle body. When the main switch is closed, the positive and negative battery groups are connected in series. It is characterized in that a conversion switch is added on the dashboard for parallel operation of the positive and negative battery groups; a conversion device is added to realize parallel connection of the positive and negative battery groups; the conversion device includes grid-connected contactor 1 CJ1, grid-connected contactor 2 CJ2, negative group 1 contactor CJ3, main switch relay CJ4, and conversion relay CJ5.

2. A positive and negative battery parallel input and output conversion system according to claim 1, characterized in that: The main switch relay CJ4 is used to control the grid-connected contactor 1 CJ1 and the grid-connected contactor 2 CJ2, so that the positive and negative battery groups can be switched between parallel and series states.

3. A positive and negative battery parallel input and output conversion system according to claim 1, characterized in that: The transfer relay CJ5 is used to control the grid-connected contactor 2 CJ2 and the negative group 1 contactor CJ3, and to control the connection status of the positive and negative poles of the negative group battery.

4. A positive and negative battery parallel input and output conversion system according to claim 1, characterized in that: The main switch relay CJ4 and the changeover relay CJ5 adopt the form of contacts being connected in series with the same line package.

5. A positive and negative battery parallel input and output conversion system according to claim 1, characterized in that: Grid-connected 1 contactor CJ1 and grid-connected 2 contactor CJ2 are used to realize the grid connection of positive and negative battery groups, and negative group 1 contactor CJ3 is used to realize the negative electrode output control of the negative battery group.

6. A positive and negative battery parallel input and output conversion system according to any one of claims 1 to 5, characterized in that: A plurality of freewheeling diodes are arranged, and CJ1, CJ2, CJ3, CJ4, and CJ5 are respectively connected in parallel with the freewheeling diodes to provide a discharge circuit for the self-inductance electromotive force generated by the relays and contactors when they are turned on or off; an anti-reverse connection diode is arranged between the instrument panel and the conversion device to suppress reverse current.

7. A method for parallel input and output of positive and negative battery packs, characterized in that: When the main switch is disconnected and the newly added conversion switch is turned on separately, the negative group battery is connected in parallel to both ends of the positive group battery, and the load connected to the original negative group battery is cut off at the same time; the working process is that the main switch relay CJ4 does not work, the contacts are normally closed, the conversion switch outputs to the grid connection 1 contactor CJ1, the CJ1 contactor is turned on, and the positive electrode of the negative group battery is connected to the positive electrode of the positive group battery; the conversion switch outputs to the grid connection 2 contactor CJ2, the CJ2 contactor is turned on, and the negative electrode of the positive group battery is connected to the negative electrode of the negative group battery; the conversion switch outputs to the conversion relay CJ5, CJ5 works, the normally closed contact is disconnected, the negative group 1 contactor CJ3 is disconnected, and the negative electrode output of the negative group battery is disconnected; the main switch is disconnected, J1 and J2 are disconnected, the negative electrode of the positive group battery is disconnected from the vehicle body, and the positive electrode of the negative group battery is disconnected from the vehicle body.

8. A method for parallel input and output of positive and negative battery packs according to claim 7, characterized in that: The positive and negative battery groups together power the heater.

9. A method for parallel input and output of positive and negative battery packs according to claim 7, characterized in that: When the newly added conversion switch is disconnected and the main switch is turned on alone, the operation of the electrical equipment on the vehicle remains the same as the original vehicle model. The working process is as follows: the main switch outputs to J1, the J1 contactor is turned on, and the negative pole of the positive battery group is connected to the vehicle body; the CJ5 contactor does not work, and the contacts are normally closed, the main switch outputs to the J2 contactor coil, the J2 contactor is turned on, and the positive pole of the negative battery group is connected to the vehicle body; the main switch outputs to CJ3, the CJ3 contactor works, the contacts are turned on, and the negative pole of the negative battery group is output to the distribution box -24V; the main switch outputs to CJ4, the CJ4 contactor works, the contacts are disconnected, and CJ1 and CJ2 are disconnected; the positive pole of the positive battery group is output to the distribution box +24V, the positive and negative battery groups are in series, and the distribution outputs positive and negative 24V.

10. The method for parallel input and output of positive and negative battery packs according to any one of claims 7-8, characterized in that: When the main switch is turned on and the transfer switch is turned on, the J1 contactor is turned on, and the negative pole of the positive battery is connected to the vehicle body; the J2 contactor does not work, and the positive pole of the negative battery is disconnected from the vehicle body; the CJ4 and CJ5 contactors work, and the two contactor contacts are disconnected; CJ1, CJ2, and CJ3 do not work; the positive pole of the positive battery is output to the main distribution box, and the negative pole of the negative battery is disconnected, leaving only the positive battery to power the vehicle.

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