Charging of electric vehicles and construction machines

Abstract

A method for managing a state of charge of a battery of an electric work vehicle in preparation for returning to work at a return to work time. Data including an expected date and time of the return to work is obtained from an output of a user interface and used to calculate a duration of an expected immobilization of the electric work vehicle. A charging rate is determined based on the duration of the expected immobilization of the work vehicle and a target charge increment. A charging start time is calculated such that at the return to work time, an actual state of charge of the battery is a target operational state of charge value. A temperature of the battery is adjusted such that the battery is at a target temperature at the charging start time. A charging cycle is initiated at the charging start time.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of charging electric vehicles or construction machinery. BACKGROUND

[0002] Electric vehicles or construction machinery can include a battery inside the electric vehicle that is charged with power using an external vehicle charging device. Traditionally, many electric vehicles default to a fast charging scenario, assuming that the operator wants the vehicle to be ready for use as soon as possible. The battery is then kept in a high state of charge until it is used.

[0003] The health of the battery depends on several factors, including the rate at which the battery is charged, the state of charge that the battery is stored at, and the temperature of the battery during charging. Fast charging can increase battery aging, for example due to thermal shock. Many batteries can only undergo a limited number of fast charging cycles before performance degradation occurs to the extent that the battery capacity is limited below an acceptable value. Storing the battery at a high state of charge also increases battery aging.

[0004] It is known to provide a function for the user to select a charging mode based on information about electricity tariffs (US 8,716,978 B2). The lowest power cost can be determined based on a predetermined time period for charging, and the user can choose whether to proceed with fast charging or wait to charge the vehicle at a charging time period with the lowest cost.

[0005] It is known to provide a charging management system that stores the battery at a low state of charge and charges just in time before the electric vehicle is needed, rather than charging immediately and storing the battery at a high state of charge (EP 2 398 670 Al). The vehicle is fixed for a duration and the time it takes to fully charge from the initial state of the battery is used to plan the charging so that the battery is kept in a low state of charge for as long as possible in storage, and the battery reaches the highest charge level just in time before the vehicle is used.

[0006] Storing the battery at a low state of charge is important for long-term battery health, however it is also preferable to use a lower charging rate. In particular in the case of electric work vehicles with long, known fixed cycles, it can be useful to manage the charging so that the state of charge is low and the charging rate is also low.

[0007] Small off-road electrified construction machinery is typically operable between predictable times. For example, such electric work vehicles can be expected to work one shift per day, 5 days a week, and not be used overnight and at weekends. They can also be stored for long periods. SUMMARY

[0008] In light of this background, there is provided: a method for managing a state of charge of a battery of an electric work vehicle, the battery ready to return to work at a return to work time coinciding with an end of a fixed duration, the method comprising:

[0009] a. obtaining data from an output of a user interface, the data comprising an expected date and time of return to work;

[0010] b. using the expected date and time of return to work to calculate an expected fixed duration of the electric work vehicle;

[0011] c. using an initial state of charge value of the battery and a target operational state of charge value of the battery to calculate a target charge delta;

[0012] d. determining a charge rate based on the expected fixed duration of the work vehicle and the target charge delta;

[0013] e. calculating a charge start time based on the charge rate and the target charge delta such that at the return to work time, an actual state of charge of the battery is the target operational state of charge value;

[0014] f. using an initial temperature of the battery and a target temperature of the battery to calculate a target temperature change;

[0015] g. using the target temperature change to calculate a heat exchange start time such that the battery is at the target temperature at the charge start time;

[0016] h. adjusting a temperature of the battery at the heat exchange start time such that the battery is at the target temperature at the charge start time; and

[0017] i. starting a charge cycle at the charge start time such that the battery is at the target operational state of charge at the return to work time.

[0018] In this way, it is possible to manage the charging of an electric work vehicle in a way that combines consideration of long term battery health with return to work requirements. Scheduling the charge in this way allows the battery to be warmed up before charging begins, to prevent thermal shock and extend battery life. The battery can be stored at a low state of charge, and when the vehicle is not needed, the charge rate can be selected to be slower, which slows down battery degradation. Other return to work preparations can also be made. For example, work vehicles often have hydraulic circuits for operating work tools. Cold, viscous hydraulic fluid can cause parasitic losses, which can reduce charge efficiency. It can be advantageous for the hydraulic fluid to be warmed up before the vehicle is ready to return to work, which can be scheduled based on the charge plan.

[0019] In a second aspect, there is provided: a battery charge controller to manage a state of charge of a battery of an electrically powered work vehicle preparing to return to work at a return to work time coinciding with an end of a fixed duration, the battery charge controller configured to:

[0020] a. receive first data from a user interface, wherein the first data indicates a date and time of an expected return to work;

[0021] b. receive second data comprising an initial state of charge value of the battery;

[0022] c. receive third data comprising an initial temperature of the battery;

[0023] d. calculate an expected fixed duration using the first data;

[0024] e. calculate a target charge delta using the second data and a target operating state of charge of the battery;

[0025] f. determine a charge rate based on the expected fixed duration of the work vehicle, the target charge delta, and data indicative of a health of the battery;

[0026] g. calculate a charge start time based on the charge rate and the target charge delta such that at the return to work time, an actual state of charge of the battery is the target operating state of charge value;

[0027] h. calculate a target temperature change using the third data and a target temperature of the battery;

[0028] i. calculate a heat exchange start time using the target temperature change such that the battery is at the target temperature prior to the charge start time;

[0029] j. adjust a temperature of the battery at the heat exchange start time such that the battery is at the target temperature at the charge start time; and

[0030] k. start a charge cycle at the charge start time such that the battery is at the target operating state of charge at the return to work time. BRIEF DESCRIPTION OF DRAWINGS

[0031] A specific embodiment of the present application will now be described, by way of example only, with reference to the attached drawings in which:

[0032] Figure 1 A process for determining a charge rate and managing a state of charge of a battery according to an embodiment of the present application is shown.

[0033] Figure 2 A process for determining a charge rate, managing a state of charge of a battery, and warming a hydraulic fluid according to an embodiment of the present application is shown.

[0034] Figure 3A process for determining a charging rate and managing a state of charge of a battery, where the battery can be stored in a storage charge state, is shown in accordance with an embodiment of the application.

[0035] Figure 4 A process for determining a charging rate and managing a state of charge of a battery, where the battery can be charged if a target charge increment is above a threshold, is shown in accordance with an embodiment of the application.

[0036] Figure 5 A process for determining a charging rate and managing a state of charge of a battery, where a service process can be performed, is shown.

[0037] Figure 6 A process for determining a charging rate and managing a state of charge of a battery, where the battery can be stored in a storage charge state, or the battery can be charged if a target charge increment is above a threshold, is shown in accordance with an embodiment of the application. DETAILED DESCRIPTION

[0038] In accordance with an embodiment of the application, a method is provided for managing a state of charge of a battery of an electric work vehicle in preparation for returning to work coincident with the end of a fixed duration. The battery of the electric work vehicle can be connected to an external charging device. The method determines how to best use the fixed duration. The method includes charging the battery and warming up the battery prior to charging, and can additionally include one or more of warming up hydraulic fluid, performing a service process, warming up a cab, or another process suitable for preparing the vehicle for returning to work. There can be a controller for managing the state of charge of the battery.

[0039] REFERENCE Figure 1Various data inputs can be used to determine the charge cycle and to calculate the charge plan. The user inputs through the user interface the date and time they expect to return to work and thus the date and time they expect to require the vehicle to be ready to return to work. The steps involved in using this input to determine the charge cycle and plan are shown within dashed line 100. The expected date and time of return to work 111 is obtained from the user interface output and at step 110 the expected date and time of return to work 111 is used to calculate the expected duration of the immobilization of the vehicle. At step 120 the initial state of charge value 121 and the target state of charge value 122 of the battery are used to calculate the target charge increment. At step 130 the charge rate is determined using the expected duration of immobilization and the calculated target charge increment. The charge rate is calculated so that the time taken to charge the battery is less than the expected duration of immobilization of the vehicle 121. The charge rate can be constant or can vary over time. At step 140 the charge rate and the target charge increment are used to calculate how long it will take to charge the battery from the initial state of charge value to the target state of charge value. The expected duration of immobilization is then used to calculate the start time of charging t C so that the actual state of charge value of the battery will equal the target state of charge value 122 at or before the time of return to work. At step 150 the initial temperature of the battery 151 and the target temperature of the battery 152 are used to calculate the target temperature change. The target temperature change is used to calculate the time taken to cool or heat the battery from the initial temperature 151 to the target temperature 152. The start time of the heat exchange process t T is then calculated at step 160 so that the battery reaches the target temperature 152 at or before the start time of charging t C . At the start time of heat exchange t T the heat exchange process begins (step 170). At the start time of charging t C the battery is at the target temperature 152 and charging begins at the charge rate associated with the selected charge cycle (step 180). At step 190 the vehicle is then ready to return to work at the end of the expected duration of immobilization with an actual state of charge value equal to the target state of charge value 122.

[0040] At step 130 the charge rate is determined based on the target battery increment and the expected duration of immobilization. In one embodiment the charge rate can be slower than the charge rate used for fast charging. The charge rate can be calculated to benefit the battery health and so that the state of charge of the battery at or before the time of return to work equals the target state of charge 122. In a particular embodiment the charge cycle can be selected to have the slowest charge rate for which it is still possible to charge the battery to have a state of charge value equal to the target state of charge value at the time of return to work at the end of the duration of immobilization.

[0041] refer to Figure 2 In the embodiment described in [ 21 ], there is an additional step of warming the hydraulic fluid 210 . The work vehicle may include a hydraulic circuit for achieving movement of a machine work tool. Viscous hydraulic fluid results in parasitic power losses, so warming the hydraulic fluid to reduce its viscosity before the vehicle returns to service increases charging efficiency. Warming the hydraulic fluid can be performed so that the hydraulic fluid is at a target operating temperature when the vehicle returns to service. In embodiments of the present invention, warming the hydraulic fluid can occur while the battery is being charged using electricity from an external charging device.

[0042] See also Figure 3 In the illustrated embodiment, there are additional provisions for storing the electric vehicle at a low state of charge if the fixed duration is expected to be longer than a storage threshold. Storing the battery at a low state of charge is beneficial for long-term battery health, however it requires additional charging cycles, i.e., charging or discharging to the storage state of charge and then recharging it, which can be detrimental to long-term battery health. Therefore, there is a minimum length of storage time at which the benefits of storage at a low state of charge outweigh the adverse effects of the additional charging cycles. This minimum time is used as the storage threshold against which the fixed duration is compared in step 310. If the fixed duration is expected to be less than the storage threshold, the charging process is similar to Figure 1 or Figure 2 The process shown. The initial state of charge value 121 of the battery is used to calculate the target charging increment, and until the charging start time t C If the fixed duration is longer than the stored threshold, the target charge increment is calculated using the stored state of charge value 321 at step 120. After the charge rate is determined and the parameters are calculated at step 130, the battery is discharged (or charged) to the stored state of charge value at step 330 and held there until the charge start time t C In an embodiment of the present invention, the fixed duration may be compared to the storage threshold once (at step 310, before calculating the target battery increment), however, for clarity, the comparison is shown again at step 320 to clearly illustrate the two different parts of the process based on the comparison results. In a specific embodiment, the storage state of charge value may be between 40% and 50% of full capacity.

[0043] refer to Figure 4 There is an option to not charge the battery if the initial state of charge value is close to the target state of charge. At step 410, the calculated target charge increment is compared with the charge threshold. If the target charge increment is lower than the charge threshold, no charging is performed. The battery or hydraulic fluid can be warmed up before returning to work. At step 450, the initial temperature 451 and the target temperature 452 of the battery can be used to calculate the target temperature increment of the battery. Then, at step 460, the heat exchange start time t is calculated.T and at the heat exchange start time t T The temperature is adjusted (step 470) so that the battery is at the target temperature at or before the return to work time. In the case where the target charge increment is above the charge threshold, then the charging process can be performed in a similar manner to Figure 1 the charging process shown in Figure 1 . Where the steps are the same as in steps

[0044] In embodiments of the application, the method can further comprise performing a service process before the return to work time. There can be a predetermined list of service processes, including a duration of each service process, a length of the service process, and a length of time since the service process was last performed. The method can further comprise deciding whether to perform one or more service processes. The decision as to whether to perform a service process can depend on the expected duration of the vehicle's immobilisation, the duration of the service process, and the length of time since the service process was last performed.

[0045] Referring to Figure 5 , there is an example of a process that includes a service process. In the case where the service process is appropriate (e.g. based on the expected duration of the vehicle's immobilisation, the duration of the service process, and the length of time since the service process was last performed). At step 510, the duration of the service process is used to calculate a service process start time t S for the service process at step 520. At step 530, it can be determined whether the service process is appropriate, and in the case where the service process is appropriate, at step 540, the service process is performed at the service process start time t S . If at step 510 it is determined that the service process is not appropriate, then the process can continue as per the process in Figure 1 . The service process can be performed before the heat exchange start time, before the charge start time, after the vehicle is ready to return to work, or at another time before the return to work time.

[0046] In embodiments of the application, the method can further comprise performing one or more other processes to prepare the vehicle to return to work, such as warming up the cab of the vehicle.

[0047] Figure 3 and Figure 4 the processes shown in Figure 3 may be combined so that if the target charge increment is below the charge threshold but the expected duration of the immobilisation is longer than the storage threshold, then the battery can be discharged to the storage charge state value, and the process continues as per Figure 6An example of this process is shown in FIG. 5. In the case where the expected duration of the fix is found to be longer than the storage threshold at step 310, then at step 120 the stored state of charge value 321 can be used to calculate the target charge delta. In the case where the expected duration of the fix is found to be shorter than the storage threshold at step 310, then at step 120 the initial state of charge value 121 of the battery can be used to calculate the target charge delta. The target charge delta can then be compared to the charge threshold at step 410.

[0048] In the case where the target charge delta is greater than the charge threshold, the process can proceed similarly to Figure 3 The same steps as Figure 3 FIG. 5, with like reference numerals. The charge rate is determined at step 130, and the charge start time can be calculated at step 140. The target temperature change is calculated at step 150, and the heat exchange start time is calculated at step 160. In the case where the duration of the fix is shorter than the storage threshold at step 320, then the next step 170 can be to adjust the temperature at the heat exchange start time t T The battery is heated or cooled to the target temperature 152. At the charge start time t C , the battery is at the target temperature 152 and charging begins at the charge rate until the state of charge value equals the target state of charge 122. The vehicle is then ready to return to work at the return to work time at step 190. In the case where the duration of the fix is longer than the storage threshold at step 320, there can be an additional step 330 where the actual state of charge of the battery is adjusted to equal the stored state of charge value 321. The state of charge of the battery can remain at the stored state of charge value 321 until the charge start time t C .

[0049] In the case where the target charge delta is less than the charge threshold at step 410, the duration of the fix can be compared to the storage threshold at step 620. In the case where the duration of the fix is longer than the storage threshold, the battery can be stored at a state of charge equal to the stored state of charge, so the process continues in the same way as where the target charge delta was found to be greater than the charge threshold at step 410, by determining the charge rate at step 130. In the case where the duration of the fix is shorter than the storage threshold, no discharging or charging can occur and only the temperature is adjusted. The target temperature change can be calculated at step 650 using the initial temperature 651 and the target temperature 652, and the heat exchange start time t T can be calculated at step 660. At the heat exchange start time t T , the temperature can be adjusted (step 670), and the vehicle is ready to return to work at the return to work time (step 190).

[0050] In certain embodiments, Figure 1 the processes shown in FIGS. 5 and 6 can be combined in various combinations.

[0051] In an embodiment of the present invention, the battery temperature may be obtained by measuring the temperature of the battery fluid.The heat exchange process may use a liquid heat exchanger to heat or cool the battery fluid.

[0052] In certain embodiments, the method may further include obtaining data indicative of battery health. The data indicative of battery health may include a state of charge value and temperature of the battery during charging, and in subsequent charging cycles, this data may be used at step 130 to determine a charge rate or decide whether to perform a service procedure. In this manner, if the data indicative of battery health indicates that the battery's performance has degraded, the selected charging cycle may be adjusted.

Claims

1. A method for managing the state of charge of a battery of an electric work vehicle in preparation for returning to work at a return to work time coinciding with the end of a fixed duration, comprising: a. obtaining data from the output of the user interface, wherein the data includes an expected date and time of return to work; b. calculating the expected fixed duration of the electric work vehicle using the expected date and time of return to work; c. calculating a target charge increment using the initial state of charge value of the battery and the target operational state of charge value of the battery, and comparing the target charge increment with a charge threshold, wherein if the target charge increment is less than the charge threshold, the target charge increment is zero; d. determining a charge rate based on the expected fixed duration of the work vehicle and the target charge increment, such that the charge rate is the slowest charge rate that charges the battery to the target operational state of charge value at the end of the fixed duration; e. Calculating a charging start time based on the charging rate and the target charging increment so that, at the return-to-work time, the actual state of charge of the battery is the target operational state of charge value; f using the initial temperature of the battery and the target temperature of the battery to calculate the target temperature change; g. Using the target temperature change to calculate the heat exchange start time, so that the battery is at the target temperature at the start time of charging; h. adjusting the temperature of the battery at the start time of the heat exchange so that the battery is at the target temperature at the start time of charging; and i. Starting a charging cycle at the charging start time so that the battery is at the target operational state of charge value at the return to service time.

2. The method according to claim 1, wherein The electric work vehicle includes a hydraulic circuit for effecting movement of a machine work tool, and wherein the method further includes warming hydraulic fluid in the hydraulic circuit such that the hydraulic fluid is at a target hydraulic fluid temperature at the return-to-work time.

3. The method according to claim 1, wherein The method step (b) further comprises comparing the expected fixed duration to a stored threshold value and, if the expected fixed duration is longer than the stored threshold value, using a stored state of charge value as the initial state of charge in step (c).

4. The method according to claim 3, wherein: The method further includes adjusting the state of charge of the battery to the stored state of charge value after step (g).

5. The method according to claim 3, wherein The stored state of charge value is between 40% and 50%.

6. The method according to claim 1, wherein The method further includes performing a service procedure prior to the return to work time.

7. The method according to claim 1, wherein The method further includes obtaining data indicative of battery health.

8. The method according to claim 1, wherein The charging start time may be further based on external factors that vary over the expected fixed duration, wherein the external factors include one or more of the following: a. Electricity charges; and b. Ambient temperature.

9. A battery charge controller for managing the state of charge of a battery of an electric work vehicle in preparation for return to work at a return to work time coinciding with the end of a fixed duration, the battery charge controller being configured to: a. receiving first data from a user interface, wherein, The first data indicates an expected return to work date and time; b. receiving a second data including an initial state of charge value of the battery; c. receiving a third data including an initial temperature of the battery; d. calculating the expected duration of the fixation using the first data; e. calculating a target charge increment using the second data and the target operational state of charge value of the battery, and comparing the target charge increment with a charge threshold, wherein if the target charge increment is less than the charge threshold, the target charge increment is zero; f. determining a charge rate based on the expected fixed duration of operation of the vehicle, the target charge increment, and data indicative of battery health, such that the charge rate is the slowest charge rate that charges the battery to the target operational state of charge value at the end of the fixed duration; g. Calculating a charging start time based on the charging rate and the target charging increment so that at the return-to-work time, the actual state of charge of the battery is the target operating state of charge value; h. using the third data and the target temperature of the battery to calculate the target temperature change; i. Using the target temperature change to calculate the heat exchange start time, so that the battery is at the target temperature before the charging start time; j. adjusting the temperature of the battery at the start time of the heat exchange so that the battery is at the target temperature at the start time of the charge; and k. Starting a charging cycle at the charging start time so that the battery is at the target operational state of charge value at the return to service time.

10. The battery charge controller according to claim 9, wherein: The electric work vehicle includes a hydraulic circuit for effecting movement of a machine work tool, and wherein the controller is further configured to warm hydraulic fluid in the hydraulic circuit such that the hydraulic fluid is at a target hydraulic fluid temperature at the return-to-work time.

11. The battery charge controller according to claim 9, further configured to receive fourth data, wherein: The fourth data comprises a stored state of charge value, and wherein the battery charge controller is further configured to compare the expected fixed duration with a stored threshold value and, if the expected fixed duration is longer than the stored threshold value, use the stored state of charge value as the second data comprising an initial state of charge value.

12. The battery charge controller according to claim 11, wherein: The controller is further configured to adjust the state of charge of the battery to the stored state of charge value after step (i).

13. The battery charging controller according to any one of claims 9 to 12, wherein: The controller is further configured to perform a service procedure prior to the return to service time.

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