Patent Description:
An electric vehicle or construction machine may comprise a storage battery inside the electric vehicle that is charged with power using an external vehicle charging apparatus. Conventionally, many electric vehicles default to a fast charge scenario, assuming that the operator wants the vehicle to be ready for use as soon as possible. The battery is then held at a high state of charge until it is used.

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

It is known to provide functionality for a user to choose a charging mode based on information about the cost of electricity (<CIT>). The lowest cost of power may be determined on the basis of a predetermined time period for charging, and the user can choose whether to proceed with fast charging or to wait to charge the vehicle at the charging period with the lowest cost.

It is known to provide a charging management system that stores the battery at low state of charge and charges just before the electric vehicle is required, rather than charging immediately and storing the battery at a high state of charge (<CIT>). The duration of immobilization of the vehicle and the time taken for a full charge from the initial state of the battery are used to schedule charging such that the battery remains in a low state of charge for as long as possible in storage, and the battery reaches the highest level of charge just before the vehicle is used.

Storing batteries at low state of charge may be important for long-term battery health, however it may also be preferable to use lower charge rates. Particularly in the case of electric work vehicles with long, known periods of immobilization it may be useful to manage charging such that the storage state of charge is low and the rate of charging is also low.

Small off-highway electrified construction machinery may typically be operational between predicable times. For example, such electric work vehicles might be expected to work a single shift in a day, <NUM> days a week and be unused overnight and at weekends. They may also be put into long term storage.

<CIT> relates to a method for preheating a battery of an electrically driven motor vehicle, wherein a charging process and a discharging process of the battery are controlled in such a way that a minimum temperature of the battery is attained at a departure time of the motor vehicle.

<CIT> relates to a controller of a vehicle power supply that decides the charging start time in accordance with a running start scheduled time set for the vehicle and a battery state, controls the operation of at least either of a heater and a blower for a temperature of a battery module to satisfy a predetermined setting temperature condition at the charging start time, and completes charging the battery until the running start scheduled time for the vehicle.

The present invention is defined by the attached independent claims. Other preferred embodiments may be found in the dependent claims.

Against this background, there is provided: a method for managing state of charge of a battery of an electric work vehicle to be ready to return to work at a return to work time that coincides with an end of a duration of immobilization, comprising:.

In this way, it may be possible to manage the charging of an electric work vehicle in such a way that combines considerations of long term battery health with return to work requirements. Scheduling charging in such a way allows the battery to be warmed before charging begins, to prevent thermal shock and prolong battery lifetime. The battery can be stored at a low state of charge and the charge rate can be chosen to be slower when the vehicle is not needed imminently, which slows battery degradation. Other preparation for returning to work may also be carried out. For example, work vehicles often have a hydraulic circuit for operating a work tool. Cold, viscous hydraulic fluid may result in parasitic losses which may reduce charge efficiency. It may be beneficial for the hydraulic fluid to be warmed before the vehicle is ready to return to work, which can be scheduled based on the charging schedule.

In a second aspect there is provided: a battery charging controller for managing state of charge of a battery of an electric work vehicle to be ready to return to work at a return to work time that coincides with an end of a duration of immobilization, the battery charging controller configured to:.

A specific embodiment of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:.

According to an embodiment of this disclosure, there is a method for managing the state of charge of a battery of an electric work vehicle to be ready to return to work at a return to work time that coincides with an end of duration of immobilization. The battery of the electric work vehicle may be connected to an external charging device. The method determines how best to use the duration of immobilization. The method comprises charging the battery and warming the battery before charging, and may additionally comprise one or more of warming hydraulic fluid, performing a service process, warming the cab or another process suitable for readying the vehicle for return to work. There may be a controller for managing the state of charge of the battery.

Referring to <FIG>, various data inputs may be used to determine a charge cycle and calculate the charging schedule. The user enters a date and time at which they expect to return to work, and therefore at which they expect to require the vehicle to be ready to return to work, via the input of a user interface.

The steps which may be involved in using this input to determine the charge cycle and schedule are shown within the dashed line <NUM>. The expected date and time of return to work <NUM> is obtained from an output of the user interface, and at step <NUM> the expected date and time of return to work <NUM> is used to calculate an expected duration of immobilization of the vehicle. At step <NUM> an initial state of charge value <NUM> for the battery and a target state of charge value <NUM> are used to calculate a targeted charge increase. An expected duration of immobilization and the calculated targeted charge increase are used to determine a charge rate at step <NUM>. The charge rate is calculated such that the time it will take to charge the battery is less than the expected duration of immobilization of the vehicle <NUM>. The charge rate may be constant or may vary over time. At step <NUM>, the charge rate and targeted charge increase are used to calculate how long it will take to charge the battery from the initial state of charge value to the targeted state of charge value. The expected duration of immobilization is then used to calculate the start time for charging tC such that the actual state of charge value of the battery will be equal to the target state of charge value <NUM> at or before the return to work time. At step <NUM> an initial temperature of the battery <NUM> and a target temperature of the battery <NUM> are used to calculate a targeted temperature change. The targeted temperature change is used to calculate how long it will take to cool or heat the battery from the initial temperature <NUM> to the target temperature <NUM>. The start time for the heat exchange process tT is then calculated at step <NUM> such that the battery reaches the target temperature <NUM> at or before the start time for charging tC. At the heat exchange start time tT the heat exchange process begins (step <NUM>). At the charging start time tC the battery is at the target temperature <NUM>, and the charging begins at the charge rate associated with the selected charge cycle (step <NUM>). At step <NUM> the vehicle is then ready to return to work, with an actual state of charge value equal to the target state of charge value <NUM>, at the end of the expected duration of immobilization.

The charge rate is determined at step <NUM> based on the targeted charge increase and the expected duration of immobilization. In an embodiment, the charge rate may be slower than a charge rate used for fast charging. The charge rate may be calculated to benefit battery health and such that the state of charge of the battery is equal to the target state of charge <NUM> at or before the return to work time. In a certain embodiment, the charge cycle may 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 return to work time at the end of the duration of immobilization.

Referring to the embodiment described in <FIG>, there is an additional step <NUM> of warming hydraulic fluid. Work vehicles may comprise a hydraulic circuit for effecting movement of a machine work tool. Viscous hydraulic fluid results in parasitic power losses so warming the hydraulic fluid to reduce its viscosity prior to the vehicle returning to work increases charge efficiency. The warming of the hydraulic fluid may be carried out such that the hydraulic fluid is at target operational temperature at the return to work time of the vehicle. In an embodiment of the disclosure, the warming of the hydraulic fluid may take place during charging of the battery using power from the external charging device.

Referring to the embodiment shown in <FIG>, there is the additional provision to store the electric vehicle at a low state of charge if the expected duration of immobilization is longer than a storage threshold value. Storing a battery at a low state of charge is beneficial for long-term battery health, however it entails an extra charge cycle of charging or discharging to a storage state of charge and then recharging it which may be detrimental to long term battery health. There is therefore a minimum length of storage time for which the benefits of storing at a low state of charge outweigh the adverse effects of the extra charge cycle. This minimum time is used as a storage threshold value to which the duration of immobilization is compared at step <NUM>. If the duration of immobilization is expected to be less than the storage threshold, the process of charging is similar to that shown in <FIG> or <FIG>. The initial state of charge value <NUM> of the battery is used to calculate the targeted charge increase and the battery is not charged or discharged until the charging start time tC. If the duration of immobilization is longer than the storage threshold, the storage state of charge value <NUM> is used to calculate the targeted charge increase at step <NUM>. After the charge rate has been determined at step <NUM> and the parameters calculated, the battery is discharged (or charged) to the storage state of charge value at step <NUM> and is held there until the charging start time tC. In an embodiment of the disclosure the duration of immobilization may be compared to the storage threshold value once (at step <NUM>, before calculating the targeted charge increase), however for clarity the comparison is shown again at step <NUM> to show clearly the two parts where the process differs depending on the result of the comparison. In a certain embodiment the storage state of charge value may be between <NUM> % and <NUM> % of full capacity.

With reference to <FIG>, there is an option to not charge the battery if the initial state of charge value is close to the target state of charge. The calculated targeted charge increase is compared to a charge threshold at step <NUM>. If the targeted charge increase is lower than the charge threshold then charging does not take place. The battery or hydraulic fluid may be heated before the return to work time. The initial temperature <NUM> and target temperature <NUM> of the battery may be used to calculate the targeted temperature increase of the battery at step <NUM>. The heat exchange start time tT is then calculated at step <NUM>, and the temperature is adjusted at the heat exchange start time tT (step <NUM>) such that the battery is at the target temperature at or before the return to work time. In the event that the targeted charge increase is higher than the charge threshold then the charging process may be carried out in a similar way to that shown in <FIG>. Where the steps are the same as those in <FIG>, the same reference numerals are used.

In an embodiment of the disclosure, the method may further comprise performing a service process before the return to work time. There may be a pre-determined list of service processes comprising the duration of each service process, the length of service process and the length of time since it was last performed. The method may further comprise deciding whether to perform one or more of the service processes. The decision as to whether to perform a service process may depend on the expected duration of immobilization of the vehicle, the duration of a service process and the length of time since the service process was last performed.

With reference to <FIG>, there is an example of a process including a service process. In the event that a service process is appropriate (for example, based on the expected duration of immobilization of the vehicle, the duration of a service process and the length of time since the service review was last performed). At step <NUM>, a duration of the service process is used to calculate a service process start time tS for the service process at step <NUM>. At step <NUM>, it may be decided whether a service process is appropriate and in the event that a service process is appropriate the service process is performed at the service process start time tS at step <NUM>. In the event that a service process is determined not to be appropriate at step <NUM>, the process may continue in line with the process in <FIG>. The service process may be performed before the heat exchange start time, before the charging start time, after the vehicle is ready to return to work, or at another time before the return to work time.

In an embodiment of the disclosure, the method may further comprise performing one or more other processes to ready the vehicle to return to work, for example warming the cab of the vehicle.

The processes shown in <FIG> and <FIG> may be combined, such that if the targeted charge increase is lower than the charge threshold but the expected duration of immobilization is longer than the storage threshold, the battery may be discharged to the storage state of charge value and the process may continue in line with <FIG>. An example of such a process is shown in <FIG>. In the event that the expected duration of immobilization is found to be longer than the storage threshold at step <NUM>, the storage state of charge value <NUM> may be used to calculate the targeted charge increase at step <NUM>. In the event that the expected duration of immobilization is found to be shorter than the storage threshold at step <NUM>, the initial state of charge value <NUM> of the battery may be used to calculate the targeted charge increase at step <NUM>. The targeted charge increase may then be compared of the charge threshold at step <NUM>.

In the event that the targeted charge increase is larger than the charge threshold, the process may proceed similarly to <FIG>. Reference numerals are the same for steps which are the same as <FIG>. The charge rate is determined at step <NUM>, and the charging start time is calculated at step <NUM>. The targeted temperature change is calculated at step <NUM>, and the heat exchange start time is calculated at step <NUM>. In the event that the duration of immobilization is shorter than the storage threshold at step <NUM>, the next step <NUM> may be to heat or cool the battery to the target temperature <NUM> at the heat exchange start time tT. At the charging start time tC the battery is at the target temperature <NUM> and charging begins at the charge rate until the state of charge value is equal to the target state of charge <NUM>. The vehicle is then ready to return to work at the return to work time, at step <NUM>. In the event that the duration of immobilization is longer than the storage threshold at step <NUM>, there may be an additional step <NUM> in which the actual state of charge of the battery is adjusted to be equal to the storage state of charge value <NUM>. The state of charge of the battery may be maintained at the storage state of charge value <NUM> until the charging start time tC.

In the event that at step <NUM> the targeted charge increase is smaller than the charge threshold, the duration of immobilization may be compared to the storage threshold at step <NUM>. In the event that the duration of immobilization is longer than the storage threshold, the battery may be stored with a state of charge equal to the storage state of charge so the process continues in the same way as if the targeted charge increase was found to be larger than the charge threshold at step <NUM>, by determining a charge rate at step <NUM>. In the event that the duration of immobilization is shorter than the storage threshold, it may be that no discharging or charging takes place and only the temperature is adjusted. The targeted temperature change is calculated at step <NUM> using an initial temperature <NUM> and a target temperature <NUM>, and the heat exchange start time fT is calculated at step <NUM>. At the heat exchange start time tT the temperature is adjusted (step <NUM>) and the vehicle is ready to return to work at the return to work time (step <NUM>).

In certain embodiments, the processes shown in <FIG> may be combined in various combinations.

In an embodiment of the disclosure the battery temperature may be obtained by measuring the temperature of the battery fluid. The heat exchange process may heat or cool the battery fluid using a liquid heat exchanger.

Claim 1:
A method for managing state of charge of a battery of an electric work vehicle to be ready to return to work at a return to work time (<NUM>) that coincides with an end of a duration of immobilization, comprising:
a. obtaining data from the output of a user interface, wherein the data comprises an expected date and time of return to work (<NUM>); and
b. using the expected date and time of return to work (<NUM>) to calculate an expected duration of immobilization of the electric work vehicle;
c. using an initial state of charge value (<NUM>) of the battery and a target operational state of charge value (<NUM>) of the battery to calculate a targeted charge increase and comparing the targeted charge increase to a charge threshold, wherein in an event that the targeted charge increase is smaller than the charge threshold the targeted charge increase is zero;
d. determining a charge rate based on the expected duration of immobilization of the work vehicle and the targeted charge increase;
e. calculating a charging start time based on the charge rate and the targeted charge increase, such that at the return to work time (<NUM>) an actual state of charge of the battery is the target operational state of charge value (<NUM>);
f. using an initial temperature (<NUM>) of the battery and a target temperature (<NUM>) of the battery to calculate a targeted temperature change;
g. using the targeted temperature change to calculate a heat exchange start time such that the battery is at the target temperature (<NUM>) at the charging start time;
h. adjusting the temperature of the battery at the heat exchange start time such that the battery is at the target temperature (<NUM>) at the charging start time; and
i. starting the charge cycle at the charging start time such that the battery is at the target operational state of charge (<NUM>) at the return to work time.