An oil-to-electricity forklift truck and a method for modifying the same

Abstract

The application discloses an oil-to-electricity forklift and a modification method thereof, which comprises a frame, an electric power system, a hydraulic system and a cooling liquid storage tank arranged on the frame, and further comprises an integrated cooling system, wherein the integrated cooling system comprises a first cooling loop communicated with the electric power system and a second cooling loop communicated with the hydraulic system; the first cooling loop and the second cooling loop are connected with the cooling liquid storage tank, and the second cooling loop is further provided with a heat exchanger. Through functional reconstruction of a fuel tank of an internal combustion forklift, the fuel tank is modified into an integrated cooling liquid storage tank, and a multi-loop cooling architecture serving the three-electricity system and the hydraulic system is constructed with the integrated cooling liquid storage tank as a core. On the premise of minimizing structural changes, two core problems, i.e. heat dissipation of multiple heat sources and vehicle transverse stability, in the process of oil-to-electricity modification are solved.

Description

Technical Field

[0001] This invention relates to the field of forklift modification technology, specifically to a hydraulic-to-electric forklift and its modification method. Background Technology

[0002] Driven by policies promoting energy conservation, emission reduction, and industrial upgrading, converting existing internal combustion forklifts to electric power has become a crucial path for logistics and manufacturing industries to reduce operating costs and achieve green transformation. Users generally expect that the converted electric forklifts should not only possess the advantages of zero emissions and low noise, but also approach or even surpass the original internal combustion models in terms of power performance, operating habits, and usage costs. Therefore, a technological solution that balances performance, cost, and conversion efficiency has urgent market demand and broad application prospects.

[0003] However, conventional conversion solutions for internal combustion forklifts to electric power face significant technical challenges. On one hand, traditional internal combustion forklifts only require two cooling circuits for the engine and hydraulic system; however, after electrification, the addition of a traction motor system, oil pump motor system, high-voltage power battery pack, and the retained hydraulic system necessitates at least four independent cooling circuits, multiplying the heat dissipation requirements and complicating the layout. On the other hand, to control costs, the conversion requires retaining the original frame structure as much as possible. However, simple component replacement often results in unused space in the original fuel tank, disrupting the original left-right weight balance of the frame and reducing the lateral stability of the converted vehicle, posing a safety hazard.

[0004] Existing technologies typically employ a "layered" approach to modification, adding a separate cooling module to the newly added electric drive system, coexisting with the hydraulic cooling system. This results in complex piping, increased costs, and a large space requirement, while failing to address the issue of weight imbalance. Its fundamental flaw lies in the failure to functionally reconfigure and fully utilize the core space of the original chassis—the fuel tank—from a system integration perspective. Therefore, there is an urgent need for an innovative solution for converting fuel-powered forklifts to electric power, capable of simultaneously solving the two core challenges of efficient heat dissipation from multiple heat sources and ensuring overall vehicle stability through systematic thermal management design, while minimizing structural modifications. Summary of the Invention

[0005] In view of this, the present invention provides a gasoline-to-electric forklift and its modification method. By reconfiguring the function of the fuel tank of the internal combustion forklift, it is transformed into an integrated coolant reservoir. Based on this, a multi-loop cooling architecture that serves the three electric systems and the hydraulic system is constructed. Under the premise of minimizing structural changes, the two core problems of heat dissipation from multiple heat sources and lateral stability of the vehicle in the process of gasoline-to-electric conversion are solved in one fell swoop.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention discloses a converted oil-powered forklift, including a frame, on which an electric power system, a hydraulic system, and a coolant reservoir are mounted, and further including an integrated cooling system, the integrated cooling system comprising: An expansion tank, which is connected to the coolant reservoir; The first cooling circuit is connected to the electric power system and is in fluid communication with the expansion tank; The second cooling circuit is connected to the hydraulic system and is equipped with a heat exchanger that exchanges heat with the cooling medium in the coolant reservoir.

[0008] As a further aspect of the present invention: the electric power system includes a traction motor assembly, an oil pump motor assembly, and a high-voltage power battery pack; the first cooling circuit includes a first branch connected to the traction motor assembly, a second branch connected to the oil pump motor assembly, and a third branch connected to the high-voltage power battery pack.

[0009] As a further aspect of the present invention: the integrated cooling system further includes a radiator, through which the first branch, the second branch and the third branch all flow.

[0010] Preferably, each branch of the first cooling circuit is in fluid communication with the expansion tank, and the coolant flows through the expansion tank in circulation to achieve heat exchange and medium compensation.

[0011] As a further aspect of the present invention: the radiator includes a first cooling chamber, a second cooling chamber, and a third cooling chamber that are isolated from each other, wherein the first cooling chamber is connected to a first branch, the second cooling chamber is connected to a second branch, and the third cooling chamber is connected to a third branch. Each branch is in fluid communication with an expansion tank, and the coolant circulates through the expansion tank to achieve heat exchange and medium compensation.

[0012] As a further embodiment of the present invention: the first branch is further provided with a first water pump; the second branch is further provided with a second water pump; and the third branch is further provided with a third water pump.

[0013] As a further aspect of the present invention: the heat exchanger is a cooling water tank cover plate disposed on the coolant storage tank, and a cooling channel is formed in the cooling water tank cover plate for the medium in the second cooling circuit to flow through.

[0014] As a further aspect of the present invention, an external cooling module is selectively connected to the coolant storage tank.

[0015] As a further aspect of the present invention: the external cooling module includes a fan, and the heat exchanger is connected to a temperature sensor.

[0016] Secondly, this invention discloses a method for converting a gasoline-powered forklift to electric as described above, comprising the following steps: S1. Provide an internal combustion forklift with a fuel tank and an internal combustion power system; S2. Convert the fuel tank into a coolant reservoir; S3. Remove the internal combustion power system and install an electric power system on the chassis; S4. Configure an integrated cooling system, connecting the first cooling circuit to the electric power system and the second cooling circuit to the hydraulic system, and connecting both the first and second cooling circuits to the coolant reservoir, and installing a heat exchanger on the second cooling circuit.

[0017] As a further aspect of the present invention, step S5 is also included: an external cooling module is installed on the coolant storage tank, and the temperature sensor on the heat exchanger is connected to the fan control unit of the external cooling module.

[0018] As a further aspect of the present invention: In step S2, transforming the fuel tank into a coolant storage tank specifically involves: cleaning the interior of the fuel tank and modifying its sealing to make it suitable for storing cooling media.

[0019] As a further aspect of the present invention: the removal of the internal combustion power system in step S3 includes: removing the engine, gearbox, drive shaft, fuel supply system and associated intake and exhaust systems.

[0020] As a further aspect of the present invention: the configuration of the integrated cooling system in step S4 includes: installing a radiator, a water pump, cooling pipes and the heat exchanger, and connecting the first branch, the second branch and the third branch of the first cooling circuit to the traction motor assembly, the oil pump motor assembly and the high-voltage power battery pack respectively, and all of them connected to the radiator; and connecting the second cooling circuit to the return oil circuit of the hydraulic system and allowing it to flow through the heat exchanger.

[0021] Compared with the prior art, the beneficial effects of the present invention are: This solution offers a novel overall architecture for converted electric forklifts. Its core lies in the innovative modification of the original internal combustion forklift's fuel tank into a coolant reservoir, upon which an integrated multi-loop cooling system is built. This design allows a single coolant reservoir to simultaneously and efficiently serve the cooling needs of multiple heat-generating components of the electric powertrain (traction motor, oil pump motor, high-voltage battery) as well as the traditional hydraulic system. This not only maximizes the utilization of the original frame structure, significantly reducing structural modifications and material costs during the conversion process, but also effectively solves the challenge of heat dissipation layout for multiple heat sources after electrification. Simultaneously, utilizing the original fuel tank's fluid mass and position helps maintain the vehicle's lateral stability after conversion, enabling the entire vehicle to achieve the advantages of zero emissions and low noise while maintaining a user experience and safety performance close to that of the original internal combustion forklift.

[0022] This method provides a conversion approach for converting fuel-powered forklifts to electric power. Starting with a standard internal combustion forklift, it systematically solves the structural adaptation, spatial reconfiguration, and thermal management challenges associated with switching from internal combustion to electric power through three core logical steps: fuel tank modification, power replacement, and system integration. By transforming the fuel tank into the core of the integrated cooling system—the coolant reservoir—this method enables the efficient implementation of subsequent complex multi-loop cooling layouts. The entire process is clearly defined and highly operable, effectively controlling conversion costs and shortening the operation cycle while ensuring conversion quality and overall vehicle performance. It provides a reliable technical implementation path for large-scale, standardized fuel-to-electric conversion projects, greatly promoting the green reuse of internal combustion forklifts. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the electric forklift converted from gasoline in this invention; Figure 2 This is a schematic diagram of the electric power system in this invention; Figure 3 This is a diagram of the cooling piping of the integrated cooling system in this invention; Figure 4 This is a schematic diagram of the hydraulic system in this invention; Figure 5 This is a schematic diagram of the external cooling module in this invention; Figure 6 This is a schematic diagram of the coolant storage tank in this invention; Figure 7 This is a schematic diagram of the structure of the fuel-powered forklift before the modification. In the diagram, 1-chassis, 2-electric powertrain system, 21-traction motor assembly, 22-oil pump motor assembly, 23-high-voltage power battery pack, 3-hydraulic system, 31-return oil filter, 32-steering gear assembly, 33-tilt cylinder, 34-multi-way valve assembly, 35-gear pump, 4-integrated cooling system, 41-radiator, 42-first water pump, 43-second water pump, 44-third water pump, 5-heat exchanger, 51-cooling channel, 6-external cooling module, 61-heat dissipation fins, 62-fan, 7-coolant reservoir, 8-instrument panel, 9-drive axle, 10-steering axle, 11-engine, 12-intake system, 13-fuel system, 14-exhaust system, 15-transmission system, 16-engine cooling system, 17-torque converter cooling system. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only 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 are within the scope of protection of the present invention.

[0025] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed during use. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0026] This embodiment provides a modified electric forklift, which is made from an oil-powered vehicle. Figure 7The forklift shown is a modified version of a conventional fuel-powered forklift. The frame 1 serves as the load-bearing base, and its hydraulic system 3, along with the instrument panel 8, drive axle 9, and steering axle 10 driven by this system, will be directly reused in the modification, forming the basis of this invention. The core power unit of this fuel-powered forklift is an internal combustion engine (engine 11), which draws in air through the intake system 12, mixes it with fuel supplied by the fuel system 13, and burns the resulting exhaust gas through the exhaust system 14. The power output from the engine 11 is transmitted to the drive axle 9 through the transmission system 15 (including a torque converter, gearbox, and drive shaft), ultimately driving the wheels. The thermal management system of the fuel-powered forklift primarily serves two heat sources: a cooling system 16 that provides forced-circulation water cooling for the engine 11 itself; and a torque converter cooling system 17 that dissipates heat from the working fluid of the hydraulic system 3. Its energy storage units are a fuel tank (located on the left, to be modified) and a hydraulic oil tank (located on the right, associated with the hydraulic system 3), located on opposite sides of the frame 1. In general, traditional internal combustion forklifts have a mechanical powertrain centered on the engine and two relatively independent cooling circuits.

[0027] Modified oil-to-electric forklifts, such as Figure 1-6 As shown, the converted electric forklift includes a frame 1, on which an electric power system 2, a hydraulic system 3, and a coolant reservoir 7 are mounted. It also includes an integrated cooling system 4, which comprises a first cooling circuit connected to the electric power system 2 and a second cooling circuit connected to the hydraulic system 3. Both the first and second cooling circuits are connected to the coolant reservoir 7, and the second cooling circuit also includes a heat exchanger 5. The first cooling circuit is indirectly connected to the coolant reservoir 7 via an expansion tank integrated on the coolant reservoir 7. By converting the original internal combustion forklift's fuel tank into a coolant reservoir 7 and constructing an integrated cooling system 4 containing the first and second cooling circuits, the single coolant reservoir 7 can simultaneously serve the cooling needs of both the electric power system 2 and the hydraulic system 3. This maximizes the utilization of the original frame 1 structure, solves the problem of multi-heat source heat dissipation layout after conversion to electric power with minimal modifications, and helps maintain the lateral weight balance of the modified vehicle. The instrument panel 8, drive axle 9, and steering axle 10 were all directly reused during the modification process without any structural changes. This maximized the inheritance of the mature components and layout of the original internal combustion forklift, significantly reducing the complexity and cost of modification, and ensuring the continuity of driver operating habits and basic vehicle performance.

[0028] Integrated cooling system 4 Figure 3As shown, the integrated cooling system mainly includes a radiator 41, a first water pump 42, a second water pump 43, a high-voltage power battery pack 23 (including a battery housing), a traction motor assembly 21, an oil pump motor assembly 22, and a third water pump 44. The radiator 41 has three independent cooling chambers: upper, middle, and lower. The traction motor assembly 21 integrates a traction motor, a traction controller, and built-in cooling channels. The oil pump motor assembly 22 integrates an oil pump motor, a pump controller, and built-in cooling channels. The high-voltage power battery pack 23 has built-in cooling channels and temperature control elements in its battery housing. The integrated cooling system 4 has three branches: a first branch consisting of the upper cooling chamber of the radiator 41, the first water pump 42, the traction motor assembly 21, and connecting pipes connected in series; a second branch consisting of the middle cooling chamber of the radiator 41, the second water pump 43, the oil pump motor assembly 22, and connecting pipes connected in series; and a third branch consisting of the lower cooling chamber of the radiator 41, the third water pump 44, the high-voltage power battery pack 23, and connecting pipes connected in series.

[0029] Hydraulic system 3 such Figure 4 As shown, it mainly includes a hydraulic oil tank, a return oil filter 31, a steering gear assembly 32, a tilting cylinder 33, a multi-way valve assembly 34, a gear pump 35, and hydraulic pipelines. The key modification in this application is the addition of a hydraulic oil heat exchange system, the core of which is the heat exchanger 5. Before the modification, the hydraulic system return oil could return directly to the oil tank or be cooled by an independent radiator; after the modification, the return oil flows through the heat exchanger 5, exchanges heat with the coolant in the coolant reservoir 7, and then returns to the hydraulic oil tank. The specific structure of the heat exchanger 5 is as follows... Figure 6 As shown, its main body is a cooling water tank cover plate installed on the upper part of the coolant reservoir 7, and a cooling channel 51 is formed inside for hydraulic oil to flow through. To enhance heat dissipation, the outer wall of the cooling channel 51 may be provided with heat dissipation fins. The hydraulic oil cooling circuit of the hydraulic system 3 is connected in series with the hydraulic oil tank, gear pump 35, multi-way valve assembly 34, steering gear assembly 32, and heat exchanger 5, and finally returns to the hydraulic oil tank.

[0030] Furthermore, a temperature sensor can be installed on the cooling channel 51 of the heat exchanger 5 to monitor the heat exchange status.

[0031] Furthermore, such as Figure 4 As shown, the outer surface of the coolant reservoir 7 can be reserved with a standard interface for installing an external cooling module 6 under high-temperature and heavy-load conditions to enhance the heat dissipation capacity of the entire system, such as... Figure 5 As shown, the external cooling module 6 may include a mounting bracket, heat sink fins 61, and a fan 62. The heat sink fins 61 are attached to the outer wall of the coolant reservoir 7, and the fan 62 provides forced air cooling to the heat sink fins 61. The vehicle controller can automatically control the start and stop of the fan 62 based on the temperature sensor signal on the heat exchanger 5, thereby achieving intelligent thermal management.

[0032] On the other hand, this embodiment provides a method for converting a conventional internal combustion forklift into an electric forklift, the purpose of which is to provide a standardized and reusable process for efficiently converting a conventional internal combustion forklift into an electric forklift with an integrated cooling system. The steps of this method will be described in detail below with reference to the accompanying drawings.

[0033] S1. Vehicle Preparation and Assessment First, a structurally sound internal combustion forklift to be modified must be provided. This forklift should have a complete frame (1), a fuel tank located on the left side of the frame, an internal combustion power system centered on the engine (including the gearbox, drive shaft, etc.), a complete hydraulic system (3), and basic components such as the instrument panel, drive axle, and steering axle. Before modification, the vehicle's condition must be assessed, with a focus on confirming that the frame (1) has no structural damage and that the fuel tank's volume and installation method meet the requirements for subsequent modifications.

[0034] S2. Structural Modification: The fuel tank is converted into a coolant reservoir 7. Specifically, the original fuel tank is thoroughly cleaned internally to completely remove fuel residue and impurities. Subsequently, according to the sealing and corrosion protection requirements of the stored coolant (usually an ethylene glycol aqueous solution), the interior of the tank undergoes necessary processing, such as applying a special lining or coating. Simultaneously, necessary functional interfaces are modified or added to the tank body: a flat, sealed interface is opened at the top for installing the heat exchanger 5 (i.e., the coolant tank cover); inlets, outlets, and vents for connection to the cooling circuit are pre-installed on the side walls or top; standardized mechanical and electrical interfaces for installing the external cooling module 6 are pre-installed on the outer side wall. After completing the internal modification and interface addition, it is reinstalled and fixed in its original position on the frame 1. At this point, its function has changed from a "fuel tank" to the aforementioned coolant reservoir 7.

[0035] S3. Powertrain Replacement: The internal combustion system is removed and an electric system is installed. Specifically, the entire mechanical transmission assembly, including the engine, gearbox, and driveshaft, is safely removed; the associated fuel supply system (fuel pump, fuel lines, filter) and intake and exhaust systems (air filter, intake manifold, exhaust manifold, muffler) are also removed. After cleaning and emptying the engine compartment, a brand-new electric powertrain 2 is installed on the chassis 1 using modified or newly manufactured mounting brackets. This system includes at least a traction motor assembly 21 (including the motor and electronic control), a fuel pump motor assembly 22, and a high-voltage power battery pack 23, with all high-voltage and low-voltage electrical connections completed.

[0036] S4. Integrated Cooling System: Configure an integrated cooling system 4, specifically as follows: (1) A radiator 41 is installed at the rear of the frame 1. The radiator 41 is preferably an integrated structure with multiple independent cooling chambers. Then, a first water pump 42, a second water pump 43 and a third water pump 44 are installed on the planned cooling pipes. The heat exchanger 5 (cooling water tank cover) is sealed and installed on the top interface of the coolant reservoir 7.

[0037] (2) Connecting the first cooling circuit (three-electric cooling circuit): Connect the outlet of the first cooling chamber of the radiator 41 to the inlet of the first water pump 42. Connect the outlet of the first water pump 42 to the coolant inlet of the traction motor assembly 21. Connect the coolant outlet of the traction motor assembly 21 to the return outlet of the first cooling chamber of the radiator 41, forming the first branch serving the traction motor. Similarly, using the second water pump 43, establish a circulation between the second cooling chamber of the radiator 41 and the oil pump motor assembly 22, forming the second branch. Using the third water pump 44, establish a circulation between the third cooling chamber of the radiator 41 and the cooling channel of the battery box of the high-voltage power battery pack 23, forming the third branch. The above three branches are connected to the expansion tank through corresponding branch and collection pipes to achieve fluid circulation, so that the coolant storage tank 7 becomes the compensation and injection center of the entire coolant circuit through the expansion tank.

[0038] (3) Connecting the second cooling circuit (hydraulic oil cooling circuit): Modify the return oil pipeline of the original hydraulic system 3. Connect the return oil pipeline to the hydraulic oil inlet of the heat exchanger 5, so that the high-temperature hydraulic oil returning from the hydraulic actuators (such as the steering gear and cylinder) is forced to flow through the cooling channel 51 inside the heat exchanger 5. The other side of the cooling channel 51 is in close proximity to the coolant in the coolant reservoir 7, and heat exchange occurs through the metal wall. The cooled hydraulic oil flows out from the outlet of the heat exchanger 5 and returns to the hydraulic oil tank.

[0039] S5. Install an external cooling module: Install an external cooling module 6 onto the pre-set interface on the outside of the coolant reservoir 7, ensuring good contact between the module's heat dissipation fins and the outer wall of the reservoir. Simultaneously, install a temperature sensor on the wall of the cooling channel 51 of the heat exchanger 5. Finally, perform system integration: Connect the signal output of the temperature sensor to the vehicle's control unit (VCU), and also connect the fan drive control terminal of the external cooling module 6 to the VCU. Thus, the VCU can intelligently control the fan's start / stop and speed based on real-time monitored coolant / hydraulic oil temperatures, achieving on-demand heat dissipation and optimizing energy consumption while ensuring cooling performance.

[0040] Finally, perform debugging: After completing all modification steps, add coolant to the coolant reservoir 7 and purge air from the pipelines, then replenish hydraulic oil. Conduct comprehensive system function tests, including verification of the electrical system, the circulation of each cooling circuit, the operation of the hydraulic system, and the intelligent temperature control function (if applicable), to ensure that the modified forklift fully meets the design requirements.

[0041] By implementing the above standardized steps, this modification method can systematically solve key problems in the electrification of internal combustion forklifts, such as power replacement, heat dissipation system reconstruction and integration, and efficiently produce high-performance oil-to-electric forklifts.

[0042] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0043] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A converted oil-powered forklift, comprising a frame (1), wherein an electric power system (2), a hydraulic system (3), and a coolant reservoir (7) are mounted on the frame (1), characterized in that, It also includes an integrated cooling system (4), which comprises: An expansion tank, which is integrated into the coolant reservoir (7); The first cooling circuit is connected to the electric power system (2) and is in fluid communication with the expansion tank; The second cooling circuit is connected to the hydraulic system (3) and is equipped with a heat exchanger (5) for heat exchange with the cooling medium in the coolant reservoir (7).

2. The electric forklift converted from gasoline to electric as described in claim 1, characterized in that, The electric power system (2) includes a traction motor assembly (21), an oil pump motor assembly (22), and a high-voltage power battery pack (23); the first cooling circuit includes a first branch connected to the traction motor assembly (21), a second branch connected to the oil pump motor assembly (22), and a third branch connected to the high-voltage power battery pack (23).

3. The electric forklift converted from gasoline to electric as described in claim 2, characterized in that, The integrated cooling system (4) also includes a radiator (41), which constitutes the heat dissipation core of the expansion tank. The first branch, the second branch and the third branch all flow through the radiator (41).

4. The electric forklift converted from gasoline to electric as described in claim 3, characterized in that, The radiator (41) includes a first cooling chamber, a second cooling chamber and a third cooling chamber that are isolated from each other, wherein the first cooling chamber is connected to a first branch, the second cooling chamber is connected to a second branch, and the third cooling chamber is connected to a third branch.

5. The electric forklift converted from gasoline to electric as described in claim 3 or 4, characterized in that, The first branch is also equipped with a first water pump (42); the second branch is also equipped with a second water pump (43); and the third branch is also equipped with a third water pump (44).

6. The electric forklift converted from gasoline to electric as described in claim 1, characterized in that, The heat exchanger (5) is a cooling water tank cover plate installed on the coolant storage tank (7), and a cooling channel (51) is formed in the cooling water tank cover plate for the medium in the second cooling circuit to flow through.

7. The electric forklift converted from gasoline to electric as described in claim 1, characterized in that, An external cooling module (6) is selectively connected to the coolant storage tank (7).

8. The electric forklift converted from gasoline to electric as described in claim 7, characterized in that, The external cooling module (6) includes a fan, and the heat exchanger (5) is connected to a temperature sensor.

9. The method for converting a gasoline-powered forklift to electric as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Provide an internal combustion forklift with a fuel tank and an internal combustion power system; S2. Convert the fuel tank into a coolant reservoir; S3. Remove the internal combustion power system and install an electric power system on the chassis; S4. Configure an integrated cooling system, connecting the first cooling circuit to the electric power system and the second cooling circuit to the hydraulic system, and connecting both the first and second cooling circuits to the coolant reservoir, and installing a heat exchanger on the second cooling circuit.

10. The modification method according to claim 9, characterized in that, It also includes step S5: installing an external cooling module on the coolant reservoir and connecting the temperature sensor on the heat exchanger to the fan control unit of the external cooling module.

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