System for calculating maximum power limit value of battery pack

Abstract

A system for calculating a maximum power limit for a battery pack of an electric vehicle includes one or more controllers in electronic communication with the battery pack. A plurality of battery open circuit voltage lookup tables and a plurality of direct current internal resistance (DCIR) lookup tables are stored in a memory of one or more controllers.

Description

Technical Field

[0001] The present disclosure relates to a system for calculating a maximum power limit of a battery pack of an electric transportation vehicle. Background Art

[0002] Electric vehicles are powered by electric motors, which are powered by rechargeable battery packs. The maximum power of the vehicle is limited by the maximum power limit of the battery pack. The maximum power limit of the battery varies over time and depends on a variety of factors, such as, but not limited to, the battery state-of-charge (SOC), the battery's charge and discharge rate (also known as C-rate), and temperature. It should be understood that the amount of available voltage provided by the battery varies as the battery discharges. When the battery's charge level is relatively low, the available voltage is correspondingly lower. Therefore, a battery with a relatively low charge level requires more current to produce the same level of power than a fully charged battery.

[0003] There are several electrochemical-based battery models available for calculating the maximum power limit of a battery. However, the electrochemical-based battery models used to calculate the maximum power limit of a battery require a lot of computing resources and memory.

[0004] Therefore, while current batteries for electric transportation vehicles perform their intended purpose, there remains a need in the art for an improved method for calculating the maximum power limit of a battery. Summary of the invention

[0005] According to several aspects, a system for a battery pack is disclosed, and includes one or more controllers that communicate electronically with the battery pack. Multiple battery open circuit voltage lookup tables and multiple direct current internal resistance (DCIR) lookup tables are stored in a memory of the one or more controllers. The one or more controllers execute instructions to receive the discharge current of the battery pack, the state of charge of the battery pack, and the battery temperature of the battery pack by the one or more controllers. The one or more controllers interpolate values ​​indicating the direct current internal resistance of the battery pack from multiple DCIR lookup tables based on the discharge current, state of charge, and battery temperature of the battery pack. The one or more controllers interpolate values ​​indicating the open circuit voltage of the battery pack from multiple battery open circuit voltage lookup tables based on the state of charge and battery temperature of the battery pack. The one or more controllers calculate a first maximum power limit of the battery pack based on the open circuit voltage, direct current internal resistance, and discharge current of the battery pack.

[0006] In another aspect, the one or more controllers execute instructions to calculate a second maximum power limit for the battery pack based on a voltage of the battery pack, a state of charge of the battery pack, a battery temperature of the battery pack, and a power request indicating an amount of power currently requested from the battery pack.

[0007] In yet another aspect, calculating a second maximum power limit of the battery pack includes determining an estimated discharge current value based on an open circuit voltage of the battery pack and a power request of the battery pack.

[0008] In one aspect, one or more controllers execute instructions to determine an estimated discharge current value based on:

[0009] Estimation I D =Power request / V OCV

[0010] Where V OCV Indicates the open circuit voltage of the battery pack, I D Indicates the discharge current of the battery pack.

[0011] On the other hand, calculating the second maximum power limit of the battery pack includes interpolating a second value indicative of a DC internal resistance of the battery pack from a plurality of DCIR lookup tables based on an estimated discharge current value, a state of charge, and a battery temperature of the battery pack, and calculating the second maximum power limit of the battery pack based on an open circuit voltage, a second DC internal resistance value, and a discharge current of the battery pack.

[0012] In yet another aspect, one or more controllers execute instructions to compare a first maximum power limit and a second maximum power limit of the battery pack and select the maximum power limit having the largest value as a final maximum power limit of the battery pack.

[0013] In one aspect, one or more controllers execute instructions to determine a real-time power of the battery pack based on a real-time voltage of the battery pack and a real-time discharge current of the battery pack.

[0014] In one aspect, one or more controllers execute instructions to compare the real-time power of the battery pack with the final maximum power limit of the battery pack, and in response to determining that the real-time power of the battery pack is greater than the final maximum power limit of the battery pack, generate a control signal instructing the battery pack to reduce the real-time power of the battery pack to the final maximum power limit of the battery pack.

[0015] In another aspect, the first maximum power limit and the second maximum power limit of the battery pack are determined based on the following factors:

[0016] Maximum power limit = V OCV *I D -(I D ) 2 R DCIR

[0017] Where V OCV Represents the open circuit voltage of the battery pack, R DCIR Indicates the DC internal resistance of the battery pack, I D Indicates the discharge current of the battery pack.

[0018] In yet another aspect, one or more controllers execute instructions to determine a voltage of the battery pack based on an open circuit voltage, a DC internal resistance, and a discharge current of the battery pack.

[0019] In one aspect, the voltage of the battery pack is determined based on:

[0020] Voltage = V OCV -R DCIR *I D

[0021] Where V OCV Represents the open circuit voltage of the battery pack, R DCIR Indicates the DC internal resistance of the battery pack, I D Indicates the discharge current of the battery pack.

[0022] In another aspect, the plurality of battery open circuit voltage lookup tables are each a one-dimensional lookup table that indicates an open circuit voltage of a battery pack based on a state of charge of the battery pack at a specific temperature.

[0023] In yet another aspect, the plurality of DCIR lookup tables are each a two-dimensional lookup table that indicates a DC internal resistance of the battery pack based on a state of charge and a discharge current of the battery pack at a specific temperature.

[0024] In one aspect, one or more controllers are in electronic communication with one or more current sensors that monitor the discharge current of the battery pack.

[0025] In another aspect, the one or more controllers are in electronic communication with one or more state of charge sensors that monitor the state of charge of the battery pack.

[0026] In yet another aspect, the one or more controllers are in electronic communication with the one or more temperature sensors to monitor the temperature of the batteries of the battery pack.

[0027] In one aspect, a method for calculating a final maximum power limit of a battery pack of an electric vehicle is disclosed. The method includes receiving, by one or more controllers, a voltage of the battery pack, a discharge current of the battery pack, a state of charge of the battery pack, a battery temperature of the battery pack, and a power request indicating the amount of power currently requested from the battery pack. The method includes interpolating a value indicating a DC internal resistance of the battery pack from a plurality of DCIR lookup tables based on the discharge current, the state of charge, and the battery temperature of the battery pack, wherein a plurality of battery open circuit voltage lookup tables and a plurality of DCIR lookup tables are stored in a memory of the one or more controllers. The method includes interpolating a value indicating an open circuit voltage of the battery pack from a plurality of battery open circuit voltage lookup tables based on the state of charge and the battery temperature of the battery pack. The method includes calculating a first maximum power limit of the battery pack based on the open circuit voltage, the DC internal resistance, and the discharge current of the battery pack. The method includes calculating a second maximum power limit of the battery pack based on the voltage of the battery pack, the state of charge of the battery pack, the battery temperature of the battery pack, and the power request. The method includes comparing the first maximum power limit of the battery pack with the second maximum power. Finally, the method includes selecting the maximum power limit with the maximum value as the final maximum power of the battery pack.

[0028] On the other hand, the method also includes determining the real-time power of the battery pack based on the real-time voltage of the battery pack and the real-time discharge current of the battery pack, comparing the real-time power of the battery pack with the final maximum power limit of the battery pack, and in response to determining that the real-time power of the battery pack is greater than the final maximum power limit of the battery pack, generating a control signal that instructs the battery pack to reduce the real-time power of the battery pack to the final maximum power limit of the battery pack.

[0029] In yet another aspect, the method further includes determining the first maximum power limit and the second maximum power limit of the battery pack based on:

[0030] Maximum power limit = V OCV *I D –(I D ) 2 R DCIR

[0031] Where V OCV Represents the open circuit voltage of the battery pack, R DCIR Indicates the DC internal resistance of the battery pack, I D Indicates the discharge current of the battery pack.

[0032] In one aspect, a system for calculating a maximum power limit of a battery pack of an electric vehicle. The system includes one or more controllers in electronic communication with the battery pack. A plurality of battery open circuit voltage lookup tables and a plurality of DCIR lookup tables are stored in a memory of the one or more controllers. The one or more controllers execute instructions to receive, through the one or more controllers, a discharge current of the battery pack, a voltage of the battery pack, a state of charge of the battery pack, a battery temperature of the battery pack, and a power request indicating the amount of power currently requested from the battery pack. The one or more controllers interpolate values ​​indicating a DC internal resistance of the battery pack from the plurality of DCIR lookup tables based on the discharge current, state of charge, and battery temperature of the battery pack. The one or more controllers interpolate values ​​indicating an open circuit voltage of the battery pack from the plurality of battery open circuit voltage lookup tables based on the state of charge and battery temperature of the battery pack. The one or more controllers calculate a first maximum power limit of the battery pack based on the open circuit voltage, DC internal resistance, and discharge current of the battery pack. The one or more controllers calculate a second maximum power limit of the battery pack based on the voltage of the battery pack, the state of charge of the battery pack, the battery temperature of the battery pack, and the power request. The one or more controllers compare the first maximum power limit of the battery pack with the second maximum power, and select the maximum power limit with the maximum value as the final maximum power limit of the battery pack. The one or more controllers determine the real-time power of the battery pack according to the real-time voltage of the battery pack and the real-time discharge current of the battery pack, and compare the real-time power of the battery pack with the final maximum power limit of the battery pack, and in response to determining that the real-time power of the battery pack is greater than the final maximum power limit of the battery pack, generate a control signal, the control signal instructing the battery pack to reduce the real-time power of the battery pack to the final maximum power limit of the battery pack.

[0033] Further areas of applicability will become apparent from the description provided herein.It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

[0035] Figure 1 A schematic diagram of a transportation vehicle including the disclosed system for calculating a maximum power limit of a battery pack in electronic communication with one or more controllers is shown according to an exemplary embodiment;

[0036] Figure 2 is a process flow diagram illustrating a method for calculating a first maximum power limit value of a battery pack based on a discharge current, a state of charge, and a battery temperature of the battery pack according to an exemplary embodiment;

[0037] Figure 3is a process flow diagram illustrating a method for calculating a second maximum power limit of a battery pack based on a voltage, a state of charge, and a battery temperature of the battery pack according to an exemplary embodiment; and

[0038] Figure 4 is a diagram showing a method for performing a Figure 2 The method shown determines the first maximum power limit and the Figure 3 The method shown is a process flow chart of a method for determining a second maximum power limit and determining a final maximum power limit of a battery pack. DETAILED DESCRIPTION

[0039] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

[0040] refer to Figure 1 , an electric vehicle 10 is shown including the disclosed system 12 for calculating the maximum power limit of a battery pack 14. The battery pack 14 provides power to one or more electric motors 16 that drive the electric vehicle 10. It should be understood that the electric vehicle 10 can be any type of vehicle, such as, but not limited to, a car, a truck, a sport utility vehicle, a van, or an RV. Figure 1 In the non-limiting embodiment shown, the electric vehicle 10 is shown as a fully electric vehicle that receives all of its power from one or more electric motors 16. However, it should be understood that the electric vehicle 10 may also be powered by an electric motor in combination with an internal combustion engine, which is referred to as a plug-in hybrid electric vehicle. Figure 1 The battery pack 14 is shown as a secondary battery for an electric vehicle, but Figure 1 This is merely exemplary in nature and the system 12 is not limited to electric vehicles. For example, in another embodiment, the system 12 can be used as part of a power tool, an electric lawn mower, or an electric off-road vehicle.

[0041] The system 12 includes a battery pack 14 and one or more controllers 20 in electronic communication with the battery pack 14. The one or more controllers 20 are in electronic communication with one or more voltage sensors 22, one or more current sensors 24, one or more state of charge (SOC) sensors 26, and one or more temperature sensors 28. The one or more voltage sensors 22 monitor the voltage of the battery pack 14 in real time, the one or more current sensors 24 monitor the discharge current of the battery pack 14 in real time, the one or more state of charge sensors 26 monitor the state of charge of the battery pack 14 in real time, and the one or more temperature sensors 28 monitor the battery temperature of the battery pack 14 in real time.

[0042] A plurality of battery open circuit voltage lookup tables 30 and a plurality of direct current internal resistance (DCIR) lookup tables 32 are stored in the memory of one or more controllers. The plurality of battery open circuit voltage lookup tables 30 are each a one-dimensional lookup table that indicates the open circuit voltage of the battery pack 14 based on the state of charge of the battery pack 14 at a specific temperature. It should be understood that a unique battery open circuit voltage lookup table 30 is provided for a specific battery temperature. The plurality of DCIR lookup tables 32 are each a two-dimensional lookup table that indicates the direct current internal resistance of the battery pack 14 based on the state of charge of the battery pack 14 and the discharge current of the battery pack 14 at a specific temperature, wherein a unique DCIR lookup table 32 is provided for a specific battery temperature. As described below, the one or more controllers 20 calculate the maximum power limit of the battery pack 14 of the electric transportation vehicle 10 based on the state of charge of the battery pack 14, the temperature of the battery pack 14, and one of the voltage of the battery pack or the discharge current of the battery pack 14 based on the interpolated values ​​from the plurality of battery open circuit voltage lookup tables 30 and the plurality of DCIR lookup tables 32.

[0043] A method of calculating a first maximum power limit of the battery pack 14 based on the discharge current, the state of charge, and the battery temperature will now be described. Figure 2 is a process flow diagram illustrating a method 200 for calculating a first maximum power limit of a battery pack 14 based on a discharge current. Figure 1 and Figure 2 , the method 200 may begin at block 202. In block 202, the one or more controllers 20 receive the discharge current of the battery pack 14 from the one or more current sensors 24, the state of charge of the battery pack 14 from the one or more state of charge sensors 26, and the battery temperature of the battery pack 14 from the one or more temperature sensors 28. The method 200 may then proceed to block 204.

[0044] In block 204 , the one or more controllers 20 interpolate values ​​indicative of the DC internal resistance of the battery pack 14 from the plurality of DCIR lookup tables 32 based on the discharge current, the state of charge, and the battery temperature of the battery pack 14 . The method 200 may then proceed to block 206 .

[0045] In block 206 , the one or more controllers 20 interpolate values ​​indicative of the open circuit voltage of the battery pack 14 from the plurality of battery open circuit voltage lookup tables 30 based on the state of charge and battery temperature of the battery pack 14 . The method 200 may then proceed to block 208 .

[0046] In block 208 , the one or more controllers 20 determine the battery pack 14 based on its open circuit voltage, DC internal resistance R DCIR and the discharge current, determine the voltage of the battery pack 14. In one embodiment, the voltage of the battery pack is determined based on Equation 1 as follows:

[0047] Voltage = VOCV –R DCIR *I D Equation 1

[0048] Where V OCV represents the open circuit voltage of the battery pack 14, R DCIR represents the DC internal resistance of the battery pack 14, I D represents the discharge current of the battery pack 14. The method 200 may then proceed to block 210.

[0049] In block 210, the one or more controllers 20 calculate a first maximum power limit of the battery pack 14 based on the open circuit voltage, DC internal resistance, and discharge current of the battery pack 14. In one embodiment, the first maximum power limit of the battery pack 14 is determined based on Equation 2, as shown below:

[0050] Maximum power limit = V OCV *I D – (I D ) 2 R DCIR Equation 2

[0051] Method 200 may then terminate.

[0052] A method of calculating the second maximum power limit of the battery pack 14 based on the voltage, state of charge, and battery temperature will now be described. Figure 3 is a process flow diagram illustrating a method 300 for calculating a second maximum power limit of the battery pack 14 based on voltage. Figure 1 and Figure 3 , the method 300 may begin at block 302. In block 302, the one or more controllers 20 receive the voltage of the battery pack 14 from the one or more voltage sensors 22, the state of charge of the battery pack 14 from the one or more state of charge sensors 26, the battery temperature of the battery pack 14 from the one or more temperature sensors 28, and send a power request to the battery pack 14. The power request represents the amount of power currently requested from the battery pack 14 by the one or more controllers 20. The method 300 may then proceed to block 304.

[0053] In block 304, the one or more controllers 20 interpolate an open circuit voltage V of the battery pack 14 from the plurality of battery open circuit voltage lookup tables 30 based on the state of charge of the battery pack 14 and the battery temperature. OCV The method 300 may then proceed to block 306 .

[0054] In block 306, the one or more controllers 20 determine an estimated discharge current value based on the open circuit voltage of the battery pack 14 determined in block 304 and the power request of the battery pack 14, wherein the power request represents the amount of power currently requested from the battery pack 14. Specifically, the estimated discharge current value is determined by Equation 3, as shown below:

[0055] Estimation I D = Power request / V OCV Equation 3

[0056] The method 300 may then proceed to block 308 .

[0057] In block 308 , the one or more controllers 20 interpolate a second value indicative of the DC internal resistance of the battery pack 14 from the plurality of DCIR lookup tables 32 based on the estimated discharge current value, the state of charge, and the battery temperature of the battery pack 14 . The method 300 may then proceed to block 310 .

[0058] In block 310 , one or more controllers 20 determine the open circuit voltage V of the battery pack 14 based on the open circuit voltage V OCV 、DC internal resistance R DCIR and the estimated discharge current value, determine the estimated voltage of the battery pack 14. In one embodiment, the estimated voltage of the battery pack 14 is determined based on Equation 4, as shown below:

[0059] Estimated voltage = V OCV – R DCIR *I D Equation 4

[0060] The method 300 may then proceed to decision block 312 .

[0061] In decision block 312, the one or more controllers 20 compare the estimated voltage of the battery pack 14 to the minimum rated voltage of the battery pack 14. It should be appreciated that the value of the minimum rated voltage of the battery pack 14 is stored in a memory of the one or more controllers 20. In response to determining that the estimated voltage is not equal to the minimum rated voltage, the method 300 returns to block 306. Otherwise, the method 300 may proceed to block 314.

[0062] In block 314, in response to determining that the estimated voltage of the battery pack 14 is equal to the minimum rated voltage of the battery pack 14, the one or more controllers 20 calculate a second maximum power limit of the battery pack 14 based on the open circuit voltage, the DC internal resistance, and the discharge current of the battery pack 14. In one embodiment, the second maximum power limit of the battery pack 14 is determined based on Equation 2 as described above. The method 300 may then terminate.

[0063] Figure 4 is shown for Figure 2The method 200 shown in FIG. 2 determines the first maximum power limit value and the Figure 3 The second maximum power limit determined by the method 300 is shown as a process flow chart of a method 400 for determining a final maximum power limit of the battery pack 14. Figure 1 and Figure 4 , the method 400 may begin at block 402. In block 402, the one or more controllers 20 compare the first maximum power limit value and the second maximum power limit value of the battery pack 14 and select the maximum power limit value with the largest value as the final maximum power limit value of the battery pack 14. The method 400 may then proceed to block 404.

[0064] In block 404, the one or more controllers 20 determine the real-time power of the battery pack 14 based on the real-time voltage of the battery pack 14 and the real-time discharge current of the battery pack 14. Figure 1 As shown, one or more voltage sensors 22 monitor the real-time voltage of the battery pack 14 , and one or more current sensors 24 monitor the real-time discharge current of the battery pack 14 . The method 400 may then proceed to decision block 406 .

[0065] In decision block 406, the one or more controllers 20 compare the real-time power of the battery pack 14 to the final maximum power limit of the battery pack 14. In response to determining that the real-time power of the battery pack 14 is less than or equal to the final maximum power limit of the battery pack 14, the method 400 may terminate. Otherwise, the method 400 proceeds to block 408.

[0066] In block 408, in response to determining that the real-time power of the battery pack 14 is greater than the final maximum power limit of the battery pack 14, the one or more controllers 20 generate a control signal instructing the battery pack 14 to reduce the real-time power of the battery pack to the final maximum power limit of the battery pack. The method 400 may then terminate.

[0067] Referring generally to the accompanying drawings, the disclosed system for calculating the maximum power limit of a battery pack has various technical effects and benefits. Specifically, the system includes one or more controllers that store a plurality of battery open circuit voltage lookup tables indicating the open circuit voltage of the battery pack and a plurality of DCIR lookup tables indicating the DC internal resistance of the battery pack. It should be understood that the lookup tables require significantly less computing resources and memory than existing methods currently available for calculating the maximum power limit of a battery pack.

[0068] A controller may refer to an electronic circuit, a combinational logic circuit, a field programmable gate array (FPGA), a processor (shared, dedicated, or group) that executes code, or a combination of some or all of the above, for example, in a system on a chip. In addition, the controller may be based on a microprocessor, for example, a computer having at least one processor, memory (RAM and / or ROM), and associated input and output buses. The processor may operate under the control of an operating system residing in the memory. The operating system may manage computer resources so that computer program code embodied as one or more computer software applications (such as applications residing in the memory) may have instructions executed by the processor. In an alternative embodiment, the processor may execute the application directly, in which case the operating system may be omitted.

[0069] The description of the disclosure is merely exemplary in nature, and variations that do not depart from the gist of the disclosure are intended to be within the purview of the disclosure; such variations should not be regarded as a departure from the spirit and scope of the disclosure.

Claims

1. A system for a battery pack, the system comprising: One or more controllers in electronic communication with the battery pack, wherein a plurality of battery open circuit voltage lookup tables and a plurality of DCIR lookup tables are stored in a memory of the one or more controllers, and wherein the one or more controllers execute instructions to: receiving, by the one or more controllers, a discharge current of the battery pack, a state of charge of the battery pack, and a battery temperature of the battery pack; interpolating a value indicative of a direct current internal resistance of the battery pack from the plurality of DCIR lookup tables based on a discharge current, a state of charge, and a battery temperature of the battery pack; interpolating a value indicative of an open circuit voltage of the battery pack from the plurality of battery open circuit voltage lookup tables based on a state of charge of the battery pack and a battery temperature; and A first maximum power limit value of the battery pack is calculated based on the open circuit voltage, the DC internal resistance and the discharge current of the battery pack.

2. The system of claim 1 , wherein the one or more controllers execute instructions to: A second maximum power limit for the battery pack is calculated based on a voltage of the battery pack, a state of charge of the battery pack, a battery temperature of the battery pack, and a power request indicating an amount of power currently requested from the battery pack.

3. The system of claim 2, wherein calculating the second maximum power limit of the battery pack comprises: An estimated discharge current value is determined based on an open circuit voltage of the battery pack and a power request of the battery pack.

4. The system of claim 3, wherein the one or more controllers execute instructions to: The estimated discharge current value is determined based on the following factors: Estimation I D =Power request / V OCV Where V OCV represents the open circuit voltage of the battery pack, I D Represents the discharge current of the battery pack.

5. The system of claim 3, wherein calculating the second maximum power limit of the battery pack comprises: interpolating a second value indicative of a DC internal resistance of the battery pack from the plurality of DCIR lookup tables based on the estimated discharge current value, a state of charge of the battery pack, and a battery temperature; as well as A second maximum power limit value of the battery pack is calculated based on the open circuit voltage of the battery pack, the second value of the DC internal resistance, and the discharge current.

6. The system of claim 2, wherein the one or more controllers execute instructions to: comparing a first maximum power limit of the battery pack to a second maximum power limit; and The maximum power limit value having the largest value is selected as the final maximum power limit value of the battery pack.

7. The system of claim 6, wherein the one or more controllers execute instructions to: The real-time power of the battery pack is determined based on the real-time voltage of the battery pack and the real-time discharge current of the battery pack.

8. The system of claim 7, wherein the one or more controllers execute instructions to: comparing the real-time power of the battery pack with a final maximum power limit of the battery pack; and In response to determining that the real-time power of the battery pack is greater than the final maximum power limit of the battery pack, a control signal is generated, the control signal instructing the battery pack to reduce the real-time power of the battery pack to the final maximum power limit of the battery pack. 9 . The system of claim 1 , wherein the plurality of battery open circuit voltage lookup tables are each a one-dimensional lookup table indicating an open circuit voltage of the battery pack based on a state of charge of the battery pack at a specific temperature.

10. The system of claim 1, wherein the plurality of DCIR lookup tables are two-dimensional lookup tables indicating a DC internal resistance of the battery pack based on the state of charge of the battery pack and the discharge current at a specific temperature.

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