An integrated vehicle test method for the battery equalization function of a power battery

Abstract

The present invention provides a vehicle integrated test method for the power battery equalization function, which includes the following steps: S1. The vehicle performs dynamic driving discharge to make the power battery reach the lower limit of SOC; S2. The power battery is charged to the equalization start SOC limit value through DC charging; S3. Steps S1 and S2 are repeatedly executed until the cell voltage difference of the power battery is greater than 5 times the equalization start SOC limit value; S4. The power battery is charged to the upper limit of SOC; S5. The vehicle ignition switch is turned on to make the vehicle in the state where the power battery power output contactor is closed, and the power battery is monitored; S6. The vehicle ignition switch is turned off to make the power battery power output contactor disconnected, and the vehicle enters the sleep state, and the cell voltage difference of the power battery is monitored. The test method of the present invention can achieve and expand the unbalanced state of the power battery in a shorter time, and at the same time realize the observation of the continuous changes of the cell voltage and the equalization time during the equalization process.

Description

Technical Field

[0001] The present invention relates to the technical field of power battery detection for electric vehicles, and particularly to an integrated vehicle test method for the power battery equalization function. Background Art

[0002] The power battery in new energy vehicles is composed of many single cells connected in series and parallel. Due to the differences in manufacturing processes of each single cell, the SOC / electricity of the cells will be different during the charging and discharging of the vehicle. If there is no effective equalization function to reduce the differences between the cells, the vehicle cannot be effectively fully charged and fully discharged, and it will affect the service life of the battery. Therefore, an effective battery equalization logic is very important, and it is even more imperative to effectively test and verify the designed equalization logic to ensure the perfection of the function. The existing integrated vehicle test method for the power battery equalization function generally involves statically sleeping the vehicle after it is fully charged after driving, and verifying the function by observing the equalization state when the communication bus is periodically awakened. This method only observes the state of the equalization-related control signals when the vehicle communication bus is awakened, and the observable points are very limited. Moreover, the driving and charging times to reach the unbalanced state are relatively long, and the unbalanced state is not fully expanded, so the equalization state cannot be turned on for a long time, and long-term continuous observation cannot be carried out.

[0003] In view of the above problems, the creator of the present invention finally obtained the present invention through long-term research and practice. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides an integrated vehicle test method for the power battery equalization function, which shortens the time required to reach equalization and realizes long-term continuous observation of the equalization function.

[0005] The technical solution adopted by the present invention is as follows:

[0006] Provide an integrated vehicle test method for the power battery equalization function, including the following steps:

[0007] S1. The vehicle performs dynamic driving discharge to make the power battery reach the SOC lower limit;

[0008] S2. Charge the power battery to the equalization start SOC limit value through DC charging;

[0009] S3. Repeatedly execute steps S1 and S2 until the voltage difference between the cells of the power battery is greater than 5 times the equalization start SOC limit value;

[0010] S4. Charge the power battery to the SOC upper limit;

[0011] S5. Turn on the vehicle ignition switch to make the vehicle in the state where the power battery power output contactor is closed, and monitor the power battery.

[0012] Further, the method further includes step S6: Turn off the vehicle ignition switch to disconnect the power battery power output contactor, make the vehicle enter the sleep state, and monitor the cell voltage difference of the power battery.

[0013] Further, in step S6, the step of turning off the vehicle ignition switch to disconnect the power battery power output contactor, making the vehicle enter the sleep state, and monitoring the cell voltage difference of the power battery specifically includes:

[0014] Turn off the vehicle ignition switch to disconnect the power battery power output contactor, make the vehicle enter the sleep state, maintain this state for 1 hour, and detect the cell voltage difference after equalization and open-circuit voltage correction.

[0015] Further, before step S1, there is also step S0,

[0016] S0. After the vehicle is charged until the power battery reaches the SOC upper limit, immerse the vehicle in an environmental chamber with a temperature of 10°C to 30°C for 16 h.

[0017] Further, in step S1, the vehicle performs dynamic driving discharge to make the power battery reach the SOC lower limit, specifically including:

[0018] S1.1. Dynamically drive the vehicle on a drum test bench and fully throttle accelerate to the vehicle's maximum speed;

[0019] S1.2. Gently step on the brake pedal to activate the maximum kinetic energy recovery until there is no energy recovery;

[0020] S1.3. Repeatedly execute steps S1.1 and S1.2 until the power battery reaches the SOC lower limit.

[0021] Further, in step S4, charging the power battery to the SOC upper limit specifically includes:

[0022] S4.1. Charge the power battery to 10% lower than the SOC upper limit with DC charging;

[0023] S4.2. Use single-phase AC charging to charge the power battery to the SOC upper limit.

[0024] Further, in step S5, turning on the vehicle ignition switch to make the vehicle in the state where the power battery power output contactor is closed, and monitoring the power battery specifically includes:

[0025] Turn on the vehicle ignition switch to make the vehicle in the state where the power battery power output contactor is closed, maintain this state for more than 45 hours, and during this period, monitor the cell voltage of the power battery.

[0026] The beneficial effects of the present invention compared with the prior art are as follows:

[0027] The present invention provides a vehicle integrated test method for the power battery equalization function, which can achieve and expand the unbalanced state of the power battery in a shorter time, and at the same time realize the observation of the continuous changes of the cell voltage and equalization time during the equalization process, so as to realize the continuous and accurate vehicle-level test of the power battery equalization function and effectively verify the battery equalization logic. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0029] Figure 1 The flowchart of the test method according to the embodiment of the present invention is shown;

[0030] Figure 2 An example diagram showing the change of the cell voltage difference of the power battery during the repeated charge and discharge process of the vehicle is shown;

[0031] Figure 3 An example diagram showing the change of the cell voltage difference of the power battery during the high-current DC fast charging process is shown. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The above and other technical features and advantages of the present invention will be described in more detail below with reference to the drawings.

[0033] As Figure 1 shown, a vehicle integrated test method for the power battery equalization function is provided, including the following steps:

[0034] S1. The vehicle performs dynamic driving discharge to make the power battery reach the SOC lower limit;

[0035] S2. The power battery is charged to the equalization start SOC limit value through DC charging (the SOC equalization function of the vehicle can only work when the power battery is charged to be greater than the equalization start SOC limit value);

[0036] S3. Steps S1 and S2 are repeatedly executed until the cell voltage difference of the power battery is greater than 5 times the equalization start SOC limit value;

[0037] S4. The power battery is charged to the SOC upper limit;

[0038] S5. Turn on the vehicle ignition switch to make the vehicle in a state where the power battery power output contactor is closed, and monitor the power battery.

[0039] Through long-term research by the creators of the present invention, it is found that during the lift power and DC charging tests, by repeatedly accelerating and decelerating the vehicle and repeatedly charging and discharging the vehicle, the imbalance between battery cells can be increased, manifested as an increase in the voltage difference between battery cells. DC fast charging with a large current can also maintain and increase the imbalance between battery cells to a certain extent. Refer to Figure 2 、 Figure 3 , Figure 2 Fig. shows an example diagram of the change in the voltage difference between battery cells of the power battery during the repeated charging and discharging process of the vehicle. Figure 3 Fig. shows an example diagram of the change in the voltage difference between battery cells during the DC fast charging of the power battery with a large current.

[0040] The test method of the present invention discharges the power battery to the lower limit of SOC, and then repeatedly performs DC charging and dynamic driving discharge between the lower limit of SOC and the SOC limit value at which the balancing is turned on for the power battery, so as to achieve a greater increase in the imbalance state of the battery cells in the power battery without turning on the balancing function, accelerate the time to reach the imbalance target, realize the expansion of the imbalance state of the power battery in a shorter time, and provide a premise for continuously observing the balance state in a shorter time.

[0041] The test method of the present invention keeps the high-voltage relay of the power battery in a closed state by turning on the ignition switch for a long time, so as to realize the vehicle maintaining communication and allowing the battery to discharge with a small current, thereby realizing the long-term observation of the continuous change of the balancing time and the cell voltage.

[0042] In one embodiment, the test method of the present invention further includes step S6: turn off the vehicle ignition switch to disconnect the power battery power output contactor, make the vehicle enter the sleep state, and monitor the voltage difference between the battery cells of the power battery. Specifically, keep the vehicle in the sleep state for 1 hour, detect the voltage difference between the battery cells after balancing and open-circuit voltage correction, and then finally verify whether the voltage difference between the battery cells reaches the expected balanced state after balancing and open-circuit voltage correction of the battery cells.

[0043] In one embodiment, before step S1, it further includes step S0: after the vehicle is charged until the power battery reaches the upper limit of SOC, immerse the vehicle in an environmental chamber with a temperature of 10°C to 30°C for 16 hours. Through step S0, the power battery is made to reach a fully charged state in preparation for subsequent discharge, and the temperature of the power battery is made to be in the normal temperature range through immersion, so as to verify the most common user usage environment.

[0044] In one embodiment, in step S1, the vehicle performs dynamic driving discharge to make the power battery reach the lower limit of SOC, specifically including:

[0045] S1.1. Dynamically drive the vehicle on a drum test bench, and fully throttle to accelerate the vehicle to its maximum speed.

[0046] S1.2. Gently step on the brake pedal to activate the maximum kinetic energy recovery until there is no energy recovery.

[0047] S1.3. Repeatedly execute steps S1.1 and S1.2 until the power battery reaches the lower limit of SOC.

[0048] As Figure 2 shown, repeatedly charging and discharging the vehicle by repeatedly accelerating and decelerating the vehicle can increase the imbalance between the battery cells, manifested as an increase in the voltage difference between the battery cells.

[0049] In one embodiment, in step S4, charging the power battery to the upper limit of SOC specifically includes:

[0050] S4.1. Charge the power battery to 10% lower than the upper limit of SOC using DC charging.

[0051] S4.2. Use a single-phase AC mode2 charging cable to charge the power battery to the upper limit of SoC.

[0052] Charging the power battery to a high SOC through rapid DC charging in step S4.1 further increases the imbalance between the battery cells. Changing from DC charging to single-phase AC charging in step S4.2 stabilizes and calms the chemical changes in the battery cells after large-current discharge and charging.

[0053] In one embodiment, in step S5, turn on the vehicle ignition switch to make the vehicle in the state where the power battery power output contactor is closed, and monitor the power battery, specifically including:

[0054] Turn on the vehicle ignition switch to make the vehicle in the state where the power battery power output contactor is closed, and maintain this state for more than 45 hours. During this period, monitor the cell voltage of the power battery.

[0055] Keeping the ignition switch on for a long time makes the high-voltage relay of the power battery in the closed state, enabling the vehicle to maintain communication and allowing the battery to discharge with a small current, and observing the estimated equalization time and the continuous change of the cell voltage.

[0056] The vehicle integration test method for the power battery equalization function of the present invention can be used for the test and verification of the power battery vehicle-level equalization function of all new energy vehicle models with DC fast charging and equalization functions, and can also be applied to the battery test of lithium battery energy storage devices that require multiple lithium battery cells to be connected in series.

[0057] The above are only the preferred embodiments of the present invention, which are illustrative rather than restrictive to the present invention. The structures and connection manners of various components in the present invention can all be changed. Any equivalent transformation and improvement made on the basis of the technical solution of the present invention should not be excluded from the protection scope of the present invention.

Claims

1. An integrated vehicle test method for the equalization function of power batteries, characterized in that, It includes the following steps: S1. Dynamically drive the vehicle to discharge, so that the power battery reaches the lower limit of SOC; S2. Charge the power battery to the balanced start SOC limit value through DC charging; S3. Repeatedly execute steps S1 and S2 until the cell voltage difference of the power battery is greater than 5 times the balanced start SOC limit value; S4. Charge the power battery to the upper limit of SOC; S5. Turn on the vehicle ignition switch to make the vehicle in the state where the power battery power output contactor is closed, and monitor the power battery; 2. The vehicle integration test method for the power battery equalization function according to claim 1, wherein, It also includes step S6: Turn off the vehicle ignition switch to make the power battery power output contactor disconnect, so that the vehicle enters the sleep state, and monitor the cell voltage difference of the power battery; 3. The vehicle integration test method for the battery equalization function of a power battery according to claim 2, wherein, For step S6, the step of turning off the vehicle ignition switch to make the power battery power output contactor disconnect, so that the vehicle enters the sleep state, and monitor the cell voltage difference of the power battery specifically includes: Turn off the vehicle ignition switch to make the power battery power output contactor disconnect, so that the vehicle enters the sleep state, maintain this state for 1 hour, and detect the cell voltage difference after equalization and open-circuit voltage correction; 4. The vehicle integration test method for the power battery equalization function according to claim 1, wherein, Before step S1, it also includes step S0; S0. After the vehicle is charged until the power battery reaches the upper limit of SOC, immerse the vehicle in an environmental chamber with a temperature of 10°C to 30°C for 16 h; 5. The vehicle integration test method for the battery equalization function as described in claim 1, characterized in that, For step S1, the vehicle dynamically drives to discharge, so that the power battery reaches the lower limit of SOC, specifically including: S1.

1. Dynamically drive the vehicle on a drum test bench, and fully throttle to accelerate to the maximum vehicle speed; S1.

2. Gently step on the brake pedal to activate the maximum kinetic energy recovery until there is no energy recovery; S1.

3. Repeatedly execute steps S1.1 and S1.2 until the power battery reaches the lower limit of SOC; 6. The vehicle integration test method for the power battery equalization function according to claim 1, characterized in that For step S4, charge the power battery to the upper limit of SOC, specifically including: S4.

1. Charge the power battery to 10% lower than the upper limit of SOC through DC charging; S4.

2. Use single-phase AC charging to charge the power battery to the upper limit of SOC; 7. The vehicle integration test method for the power battery equalization function according to claim 1, wherein, For step S5, turn on the vehicle ignition switch to make the vehicle in the state where the power battery power output contactor is closed, and monitor the power battery, specifically including: Turn on the vehicle ignition switch to make the vehicle in the state where the power battery power output contactor is closed, maintain this state for more than 45 hours, and during this period, monitor the cell voltage of the power battery;

Images