GB2598375A

GB2598375A - Vehicle traction battery control system

Info

Publication number: GB2598375A
Application number: GB2013577.8A
Authority: GB
Inventors: Nicholls Stephen; Fai Yu Tung; Devenport Richard
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2020-08-28
Filing date: 2020-08-28
Publication date: 2022-03-02
Also published as: DE102021122060A1; GB202013577D0

Abstract

A vehicle traction battery 20 includes first and second cell sets 402, 404, each having a plurality of electrical cells 402a, 402b, 404a, 404b. A switching arrangement (e.g. first and second switches 406, 408), associated with the traction battery, is controlled to electrically connect the first cell set to a traction bus of the vehicle. A temperature of at least of portion of the traction battery is determined and the switching arrangement is controlled to electrically connect the second cell set to the traction bus when the determined temperature exceeds a first threshold temperature. A cooling system may circulate coolant to the first cell set. When a temperature of at least a portion of the first cell set is determined as greater than, or equal to, a second threshold, the cooling system may circulate coolant to the first and second cell sets. The switching arrangement may connect the second cell set to the traction bus in dependence on a monitored temperature of a portion of the first or second cell sets. The switching arrangement may connect one of the cell sets to the traction bus in dependence on first and second parameters (e.g. first and second voltages) respectively associated with the first and second cells sets. When a difference between the first and second parameter values is less than a threshold value, the switching arrangement may connect both cell sets to the traction bus.

Description

VEHICLE TRACTION BATTERY CONTROL SYSTEM

TECHNICAL FIELD

The present disclosure relates to a vehicle traction battery control system and particularly but not exclusively to a control system for controlling a circuit of the traction battery. Aspects of the invention relate to a control system, to an electrical power system for a vehicle, to a method, and to computer software

BACKGROUND

Electric vehicles and hybrid electric vehicles comprise traction motors, and traction batteries for supplying electrical energy to the traction motors. Traction batteries may operate more efficiently when they are within a particular temperature range. In particular, low temperature ambient conditions may lead to a low internal temperature of the battery which can dramatically affect the performance of the battery.

It is known to raise the internal temperature of a traction battery to a desired operating range in one of two ways. The traction battery may be pre-conditioned prior to the drivecycle, however this requires an extemal source of electrical power to be available. Alternatively, heat generated due to internal resistance within the traction battery as electrical power is taken from the battery during the drivecycle may bring the internal temperature of the traction battery up to the desired range.

However, large battery packs may have a large associated thermal inertia, while efforts made to increase the efficiency of the battery packs may reduce the self-heating effect during the drivecycle. Thus, traction batteries may take a long time to reach a desired operating temperature range. Furthermore, in some cases, due to the efficiency of traction batteries under low loads (for example urban drivecycles), insufficient heat may be generated within the battery to raise the intemal temperature to the desired range.

It is an aim of embodiments of the present invention to address one or more of the disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a control system, an electrical power system for a vehicle, a vehicle, a method, and computer software as claimed in the appended claims According to an aspect of the present invention there is provided a control system comprising one or more controllers for a traction battery of a vehicle, the traction battery comprising a first cell set comprising a plurality of electrical cells and a second cell set comprising a plurality of electrical cells, the traction battery being associated with switching means operable to independently connect one or both of the first and second cell sets to a traction bus of the vehicle, the control system comprising:input means for receiving a temperature signal indicative of a temperature of at least a portion of the traction battery, output means for outputting a control signal for controlling the switching means of the traction battery to electrically connect the first cell set to the traction bus, and processing means arranged, in dependence on the temperature signal indicative of the temperature of the at least a portion of the traction battery exceeding a first threshold temperature, to control the output means to output the control signal to cause the switching means associated with the traction battery to electrically connect the second cell set to the traction bus.

According to an embodiment, there is provided the control system as described above, wherein said processing means, said input means for receiving the temperature signal indicative of a temperature of at least a portion of the traction battery and said output means for outputting the control signal for controlling the switching means of the traction battery comprise one or more electronic processors having an electrical input for receiving said temperature signal and an electrical outiout for transmitting said control signal, the control system further comprising an electronic memory device electrically coupled to the one or more electronic processors and having instructions thereon.

Optionally, the processing means may be arranged to control the output means to output a second control signal to a coolant system of the vehicle to cause the coolant system to circulate coolant to one or both of the first cell set and the second cell set Optionally, the processing means may be arranged to control the output means to output the second control signal to the coolant system to cause the coolant system to circulate coolant to the first cell set, and wherein the processing means is arranged, in dependence on the temperature signal indicative of the temperature of the at least a portion of the traction battery exceeding a second threshold temperature, to control the output means to output the second control signal to cause the coolant system to circulate the coolant to the first cell set and the second cell set.

Optionally, the processing means may be configured to determine that the temperature signal indicates that the temperature of the traction battery is below a third threshold temperature, and control the output means to output the control signal to cause the switching means of the traction battery to electrically connect the first cell set to the traction bus of the vehicle and to isolate the second cell set from the traction bus of the vehicle in dependence on the determination that the temperature of the traction battery is below the third threshold temperature.

Optionally, the first threshold temperature and the third threshold temperature may be the same. Alternatively, the first threshold temperature may be greater than the third threshold temperature.

Optionally, the input means may be arranged to receive a first signal indicative of a first parameter value associated with the first cell set of the traction battery, and receive a second signal indicative of a second parameter value associated with the second cell set of the traction battery, and the processing means may be arranged to control the output means to output the control signal to cause the switching means of the circuit to electrically connect one of the first and second cell sets to the traction bus of the vehicle in dependence on the first and second parameter values.

Optionally, the processing means may be arranged to determine, in dependence on the first and second parameter values, a greater of the first and second parameter values, and control the output means to output the control signal to cause the switching means of the circuit to electrically connect one of the first and second cell sets to the traction bus of the vehicle in dependence on the determination of which of the first and second parameter values is greater.

Optionally, the first and second parameter values may comprise a first voltage of the first cell set of the traction battery and a second voltage of the second cell set of the traction battery, and wherein the processing means may be arranged to control the output means to output the control signal to cause the switching means of the circuit to electrically connect to the traction bus of the vehicle the cell set of the first and second cell set corresponding to the one of the first and second voltages determined to be greater.

Optionally, the processing means may be arranged to determine that a difference between the first parameter value and the second parameter value is less than or equal to a threshold value, and control the output means to output the control signal to cause the switching means of the circuit to electrically connect to the traction bus of the vehicle the first cell set and the second cell set in dependence on determining that the difference between the first parameter value and the second parameter value is less than or equal to the threshold value.

Optionally, the first and second parameter values may comprise a first voltage of the first cell set of the traction battery and a second voltage of the second cell set of the traction battery and the processing means may be arranged to, in dependence on determining that the difference between the first voltage and the second voltage is greater than the threshold value, control the output means to output the control signal to cause the switching means of the circuit to electrically connect to the traction bus of the vehicle one of the first and second cell sets corresponding to the one of the first and second voltages determined to be greater.

Optionally, the first and second parameters may comprise one of: a first voltage of the first cell set of the traction battery and a second voltage of the second cell set of the traction battery; a first temperature associated with the first cell set of the traction battery and a second temperature associated with the second cell set of the traction battery; or a first time in use value associated with the first cell set of the traction battery and a second time in use value associated with the second cell set of the traction battery.

Optionally, the temperature signal indicative of a temperature of at least a portion of the traction battery may comprise a temperature signal indicative of a temperature of at least a portion of the first cell set and the processing means may be arranged to control the output means to output the control signal to cause the switching means of the circuit to electrically connect the second cell set to the traction bus of the vehicle in dependence on the temperature of the first cell set.

Optionally, the temperature signal indicative of a temperature of at least a portion of the traction battery may comprise a temperature signal indicative of a temperature of at least a portion of the second cell set and the processing means may be arranged to control the output means to output the control signal to cause the switching means of the circuit to electrically connect the second cell set to the traction bus of the vehicle in dependence on the temperature of the second cell set.

Optionally, the input means may be arranged to receive a signal indicating that an external source of electrical power is available and the processing means may be arranged, in dependence on the temperature signal indicating that the temperature of at least a portion of the traction battery is below the first threshold temperature, to control the output means to output a pre-conditioning signal to cause a pre-conditioning means to raise the temperature of the traction battery using the external source of power.

According to another aspect of the invention, there is provided an electrical power system for a vehicle comprising a control system as described above, the electrical power system comprising a traction battery comprising a first cell set comprising a plurality of electrical cells, a second cell set comprising a plurality of electrical cells, and switching means operable to independently connect one or both of the first and second cell sets to a traction bus of the vehicle.

Optionally, the control system may further comprise a temperature sensing means for determining the temperature of at least a portion of the traction battery and outputting the temperature signal.

Optionally, the electrical power system may further comprise a traction bus arranged to provide electrical power to one or more traction motors.

According to yet another aspect of the invention, there is provided a vehicle comprising the control system or the electrical power system as described above.

According to a yet another aspect of the in invention, there is provided a method of controlling a circuit for a traction battery of a vehicle, the traction battery comprising a first cell set comprising a plurality of electrical cells and a second cell set comprising a plurality of electrical cells, the method comprising controlling switching means of the circuit to electrically connect the first cell set of the traction battery to a traction bus of the vehicle, determining a temperature of at least a portion of the traction battery, and controlling the switching means of the circuit to electrically connect the second cell set to the traction bus of the vehicle in dependence on the determined temperature of the at least a portion of the traction battery.

Optionally, controlling the switching means of the circuit to electrically connect the second cell set of the traction battery to the traction bus of the vehicle in dependence on the determined temperature of the at least a portion of the traction battery may comprise controlling the switching means in response to determining that the temperature of the traction battery is greater than a first threshold temperature.

Optionally, the may comprise controlling a cooling system to circulate coolant to one or both of the first cell set and the second cell set.

Optionally, the method may comprise controlling a cooling system to circulate coolant to the first cell set, monitoring a temperature of at least a portion of the first cell set, determining that the temperature of the at least a portion of the first cell set is greater than or equal to a second threshold temperature, and controlling the cooling system to circulate coolant to the first cell set and the second cell set in dependence on the determination that the temperature of the first cell set is greater than the second threshold temperature.

Optionally, the method may comprise monitoring a temperature of at least a portion of the first cell set, and controlling the switching means of the circuit to electrically connect the second cell set to the traction bus of the vehicle based on the temperature of the first cell set.

Optionally, the method may comprise monitoring a temperature of at least a portion of the second cell set, and controlling the switching means of the circuit to electrically connect the second cell set to the traction bus of the vehicle based on the temperature of the first cell set.

Optionally, the method may comprise monitoring a first parameter value associated with the first cell set of the traction battery, monitoring a second parameter value associated with the second cell set of the traction battery and controlling the switching means of the circuit to electrically connect one of the first and second cell sets to the traction bus of the vehicle in dependence on the first and second parameter values.

Optionally, the method may comprise determining that a difference between the first parameter value and the second parameter value is less than a threshold value, and controlling the switching means of the circuit to electrically connect the first cell set and the second cell set to the traction bus of the vehicle in dependence on determining that a difference between the first parameter value and the second parameter value is less than the threshold value.

According to yet another aspect of the invention, there is provided Computer software which, when executed by a computer, is arranged to perform any method described herein. Optionally, the computer software is stored on a computer readable medium The computer software may be tangibly stored on a computer readable medium.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates a vehicle in accordance with an embodiment of the invention; Figure 2 illustrates an example of a traction battery, a traction motor and a control system in accordance with embodiments; Figure 3A illustrates an example of a control system comprising a controller in accordance with embodiments; Figure 3B illustrates an example of a non-transitory computer readable medium storing instructions in accordance with embodiments; Figure 4 illustrates an example of a circuit in accordance with embodiments; Figure 5 illustrates an example of a method in accordance with embodiments; Figure 6 illustrates an example of a further method in accordance with embodiments; and Figure 7 illustrates an example of a still further method in accordance with embodiments.

DETAILED DESCRIPTION

Figure 1 illustrates an example of a vehicle 10 in Mich embodiments of the invention can be implemented. In some, but not necessarily all examples, the vehicle 10 is a passenger vehicle, also referred to as a passenger car or as an automobile. In other examples, embodiments of the invention can be implemented for other applications, such as industrial vehicles.

The vehicle 10 may be an electric vehicle (EV) or a hybrid electric vehicle (HEV). If the vehicle 10 is an HEV, the vehicle 10 may be a plug-in HEV or a mild HEV. If the vehicle 10 is a plug-in HEV, the vehicle 10 may be a series HEV or a parallel NEV. In a parallel HEV, a traction motor and an internal combustion engine are operable in parallel to simultaneously provide tractive torque. In a series HEV, the internal combustion engine generates electricity and the traction motor exclusively provides tractive torque.

Figure 2 illustrates a system 200 comprising a traction battery 20 (battery' herein) and a control system 26 for the EV or HEV 10, which may be supplied together or separately. Figure 2 also illustrates a traction motor 28 which could optionally be part of the system 200.

The battery 20 may be a high voltage battery, particularly if the vehicle 10 is an EV or a plug-in HEV. High voltage traction batteries provide nominal voltages in the hundreds of volts, as opposed to traction batteries for mild HEVs which provide nominal voltages in the tens of volts. The battery 20 may have a voltage and capacity to support electric only driving for sustained distances requiring continuous battery power.

The battery 20 may have a capacity of several kilowatt-hours, to maximise range. The capacity may be in the tens of kilowatt-hours, or even over a hundred kilowatt-hours.

The battery 20 comprises a positive terminal 22 and a negative terminal 24. The terminals 22, 24 may be configured for connection to a high voltage bus 27. The high voltage bus 27 may be configured to supply energy from the battery 20 to power electronics, such as an inverter (not shown), and onwards to the traction motor 28. Battery 20 may further comprise sensor 21. For example, sensor 21 may be a temperature sensor to measure an internal temperature of at least a portion of the traction battery 20.

The high voltage bus 27 may also comprise charging circuitry, for connecting a charging port (not shown) and/or a generator to the battery 20.

Although one battery 20 is shown, the vehicle 10 could comprise additional traction batteries.

The illustrated traction motor 28 may be configured to output tractive torque directly or indirectly to one or more wheels of the vehicle 10. The traction motor 28 may also be configured to operate as a regenerative brake generator for converting kinetic energy of the vehicle 10 to electrical energy for the battery 20.

Although one traction motor 28 is shown, the vehicle 10 could comprise additional traction motors, for the same or different wheels of the vehicle 10.

Figure 3A illustrates how the control system 26 may be implemented. The control system 26 of Figure 3A illustrates a controller 30. In other examples, the control system 26 may comphse a plurality of controllers on-board and/or off-board the vehicle 10.

The controller 30 of Figure 3A includes at least one electronic processor 32; and at least one electronic memory device 34 electrically coupled to the electronic processor and having instructions 36 (e.g. a computer program) stored therein, the at least one electronic memory device 34 and the instructions 36 configured to, with the at least one electronic processor 32, cause any one or more of the methods described herein to be performed.

According to an example implementation, the controller 30 of Figure 3A is a battery management system (BMS). The BMS may be internal to or external from a protective housing of the battery 20.

Figure 3B illustrates a non-transitory computer-readable storage medium 38 comprising the instructions 36 (computer software).

Figure 4 illustrates a battery 20 comprising an example of a circuit 400 described herein. In some examples, the battery 20 of Fig 4 may be the battery 20 of Fig 2, for a vehicle 10 such as the vehicle 10 of Fig 1.

The battery 20 illustrated in Figure 4 comprises a first cell pack 402 and a second cell pack 404. Embodiments of the invention may be practiced with three, four or more cell packs.

The first cell pack 402 corresponds to a first cell set of a plurality of cells 402a, 402b. A series string of two cells 402a, 402b is shown in Fig 4, but more cells could be provided in the string, in other examples.

The first cell pack 402 may be a supplied module (pack') housing the first set of cells 402a, 402b. Altematively, the first set of cells 402a, 402b may not be supplied as a pack, and just as a cell set 402a, 402b. Although the term cell pack is used in the description below, just cell sets could be used instead, depending on implementation.

The individual cells of the first cell pack 402 may have equal or unequal nominal voltages. The cells of the first cell pack 402 may be interconnected in a single series string as illustrated, in parallel strings, or in a combination of parallel and series strings.

The nominal voltage of the first cell pack 402 may be in the hundreds of volts. In some examples, the nominal voltages of each of the cell packs is from the range 300-600 volts. In a specific example, the nominal voltage may be 400 volts to one significant figure. The nominal voltage is defined as the voltage between a positive terminal of the last cell of the string and a negative terminal of the first cell of the string.

The second cell pack 404 corresponds to a second cell set a plurality of cells 404a, 404b.

By design, the nominal voltage of the second cell pack 404 may be the same as the nominal voltage of the first cell pack 402.

The second cell pack 404 may have the same components as the first cell pack 402, in the same arrangement. Alternatively, the second cell pack 404 could have a different number of cells and/or the cells could be interconnected differently.

Each cell pack may comprise one or more sensors 21 for monitoring certain parameters of the cell pack. Such sensors 21 may be configured to provide indications of measured parameter values to the control system 26, or another control system, for controlling connection of one or more of the cell packs to the terminals 22, 24.

For example, temperature sensors may be provided for measuring a temperature associated with the cell packs 402, 404, such as an internal temperature of the cell pack. Similarly, voltage sensors may be provided for measuring the voltage of each cell, or between the first and last cells of a string.

The circuit 400 is configured to connect a positive terminal ++ of the first cell pack 402 to the positive terminal 22 of the battery 20. The circuit 400 is configured to connect a positive terminal ++ of the second cell pack 404 to the positive terminal 22 of the battery 20. The circuit 400 is configured to connect a negative terminal --of the first cell pack 402 to the negative terminal of the battery 20. The circuit 400 is configured to connect a negative terminal --of the second cell pack 404 to the negative terminal of the battery 20.

In particular, the circuit 400 of Figure 4 is configured to selectively allow one of the first cell pack 402 and the second cell pack 404 or both the first and second cell packs 402, 404 to be connected between the positive terminal 22 and negative terminal 24 of the traction battery 20. This may be achieved by the provision of switching means associated with the traction battery 20.

The switching means of Figure 4 comprises a first switch 406 and a second switch 408. The switches may be relays, for automatic operation. The switches may be single pole single throw switches or could be merged while providing equivalent functionality.

First switch 406 is located to control interconnection of the positive terminal ++ of one of the cell packs with the positive terminal 22 of the battery 20. In Fig 4, but not necessarily in all examples, first switch 406 is between the second cell pack 404 and the positive terminal 22 of the battery 20.

Second switch 408 controls interconnection of the negative terminal of other of the cell packs with the negative terminal of the battery 20. In Fig 4, second switch 408 is between the first cell pack 402 and the negative terminal 24. The first cell pack 402 may be connected to the negative terminal regardless of the state of the second switch 408.

Thus, the switching means, such as first and second switches 406, 408, allow the traction battery to be operated in 'half-pack' modes in which just one of the two cell packs is operational, or in a full pack mode in which both battery packs are connected to the terminals 22, 24 of the battery 20. In a first half-pack mode, the switching means electrically disconnects the first cell pack 402 without electrically disconnecting the second cell set. The first cell pack 402 is open-circuit and the second cell pack 404 is closed-circuit. In Fig 4, only the second cell pack 404 is operational in the first half-pack mode. In a second half-pack mode, the switching means electrically disconnects the second cell pack 404 without electrically disconnecting the first cell set. The first cell pack 402 is closed-circuit and the second cell pack 404 is open-circuit. In Fig 4, only the first cell pack 402 is operational in the second half-pack mode. While in the full mode the switching means connects both the first and second cell packs 402, 404 to the terminals of the battery 20.

Other switch topologies that allow for the selective connection of either one or both of the battery packs to the terminals of the battery 20 may be used in battery circuits of embodiments. For example, both switches may be coupled between the positive terminals ++ of the cell packs and the positive terminal 22 of the battery 20 or between the negative terminals --of the cell packs and the negative terminals 24 of the battery 20.

In the absence of preconditioning of the traction battery 20, at the beginning of a drivecycle the battery 20 may be at or about ambient temperature. However, ambient temperature may often be outside the desired range of operating temperatures for the battery 20. In particular, during winter months at higher latitudes, the battery 20 may begin a drivecycle significantly below a desired operating temperature range. As discussed above, operating a battery outside of the desired temperature range may result in reduced performance and/or efficiency.

In order to increase the available range of electrical vehicles, such as vehicle 10, there has been a trend to increase the installed battery capacity. However, larger batteries may experience a lower internal resistive heating effect for a given current, and may therefore take longer to attain the desired operating temperature range based on this resistive heating. This may be a particular problem when the vehicle 10 is used for relatively short or low speed journeys, such as may occur with urban drivecycles, resulting in the battery 20 taking a very long time, or even never, attaining the desired internal temperature, leading to a reduced performance of the vehicle drivetrain available to the user.

According to described embodiments, during a first stage of a drivecycle, the control circuit 26 of a traction battery 20, as illustrated in Figure 4, may be used to connect only one cell pack of the battery 20 to the terminals 22, 24, and to disconnect the other cell pack. For example, first cell pack 402 may be connected to both terminals 22, 24 of the battery 20 by closing second switch 408, while first switch 406 is open to isolate the positive terminal of the secondary battery pack 404 from the positive terminal 22.

During this first stage of the drivecycle, all electrical power used by the traction motor 28 is drawn from the first battery pack 402, resulting in a higher load being experienced by the first battery pack 402 than would be expected in the full pack mode of operation in which both battery packs 402, 404 are connected to the terminals of the battery 20, e.g. for a given current demand, the connected battery pack would supply substantially double the current in a half-pack mode than it would in a full pack mode. As the internal resistance of the battery packs is relatively fixed, the increase in current draw on the connected battery pack in a half-pack mode leads to increased internal resistive heating power in that pack, thereby bringing that connected battery pack, e.g. first battery pack 402, up to the desired operating temperature more quickly.

As discussed above, sensing means may be provided to determine a internal temperature of battery 20. For example, one or more temperature sensors may be embedded in each battery pack 402, 404 to allow the operating temperature of the battery 20 to be monitored. The control system 26 includes input means to receive an indication of a temperature signal indicative of a temperature of at least a portion of the battery 20.

While the vehicle 10 is operating in the half-pack mode, the control system 26 may monitor a temperature of the battery 20 based on the received temperature signal. When the monitored temperature exceeds a first threshold value, it may be assumed that the battery 20 has attained the desired temperature, and therefore the enhanced heating effect provided by half-pack operation is no longer required. Therefore, the processing means 30 of the control system 26 is arranged in dependence on the temperature signal indicative of the temperature of the at least a portion of the traction battery 10 exceeding the first threshold temperature, to control output means to output the control signal to cause the switching means associated with the traction battery 20 to electrically connect the second cell set 404 to the traction bus 27. That is, once the predetermined temperature, which may be a desired operating temperature, has been reached a second phase of the drivecycle is entered in which the switching means 406, 408 of the traction battery 20 are controlled to resume full pack operation.

Thus, embodiments may provide a vehicle 10 in which the traction battery 20 attains its desired operating temperature range more quickly, mitigating the negative effects associated with operation of a battery at low temperatures.

Vehicle 10 may be provided with a coolant system (not shown) to manage heat produced by vehicle components. For example, in order to avoid the traction battery 20 overheating the cooling system may provide a supply of coolant to the traction battery to absorb heat energy generated in the battery 20. The coolant may then pass through a radiator to cool the coolant before being recirculated around the coolant system.

During the first phase of the drivecycle, in which the traction battery 20 is operated in half-pack mode, the coolant system may circulate coolant through both the first battery pack 402 and second battery pack 404. Thus, heat generated in the connected battery pack during the first phase of the drivecycle may be conducted to the other battery pack in order to increase the temperature of both battery packs of the traction battery 20.

In some embodiments, the control system 26 may be arranged to monitor a temperature of the connected battery pack, e.g. first battery pack 402, and to control the output means to output the control signal to cause the switching means of the circuit 400 to electrically connect the second cell set 404 to the traction bus 27, once the temperature of the connected battery pack 402 exceeds the threshold temperature.

In some embodiments, control system 26 may be arranged to monitor the temperature of the disconnected battery pack, e.g. second battery pack 404, and to control output means to output the control signal to cause the switching means of the circuit 400 to electrically connect the second cell set 404 to the traction bus 27 of the vehicle 10 in dependence on the temperature of the second cell set 404. Thus, the vehicle 10 enters full pack operation when the disconnected battery pack reaches the threshold temperature.

In some implementations, the coolant system may be configured to initially circulate coolant to the connected battery pack, e.g. first battery pack 402, and not to the disconnected battery pack 404, to facilitate more rapid warming of the first battery pack 402. The processing means 30 of the control system 26 may then be arranged, in dependence on the temperature signal indicative of the temperature of the at least a portion of the traction battery 20 exceeding a second threshold temperature, to control the output means to output the second control signal to cause the coolant system to circulate the coolant to the first cell set 402 and the second cell set 404. Thus, once the connected battery pack has attained a predetermined internal temperature, heat is transferred through the coolant system to the disconnected battery pack to condition the isolated battery pack ready for operation in the full pack mode.

According to some embodiments, the control system 26 may only initiate half-pack operation during a first phase of the drivecycle if an indicated temperature of the traction battery 20 is below a predetermined threshold temperature. For example, in the case that the traction battery 20 retains sufficient temperature from a previous drivecycle, the control system 26 may determine that half-pack operation is not appropriate to attain the desired operating temperature range, and may therefore begin the drivecycle in the full pack mode.

Thus, the processing means 30 of the control system 26 may be configured to determine that the temperature signal indicates that the temperature of the traction battery 20 is below a third threshold temperature and control the oupciut means to output the control signal to cause the switching means of the traction battery 20 to electrically connect the first cell set 402 to the traction bus 27 of the vehicle 10 and to isolate the second cell set 404 from the traction bus 27 of the vehicle 10 in dependence on the determination that the temperature of the traction battery 20 is below the third threshold temperature.

In order to determine which battery pack of the first and second battery packs 402, 404 to connect to the terminals 22, 24 of the traction battery 20 when entering a half-pack mode, the control system 26 may monitor one or more parameters associated with the battery packs 402, 404. For example, the control system 26 may determine which battery pack 402, 404 has the highest voltage/charge level in order to reduce any imbalance caused by using only one battery pack to supply the traction motor 28. Similarly, the control system 26 may determine the initial temperatures, or time in use, associated with the battery packs and determine which battery pack to connect based on a determination of which battery pack has a higher associated initial temperature or longest time in use.

In some embodiments, the control system 26 may receive indications of voltage levels of the battery packs 402, 404. The control system 26 may compare an indicated voltage level of the first battery pack 402 with an indicated voltage level of the second battery pack 404 to determine whether a difference between the voltage levels of the battery packs is less than a threshold voltage. When resuming full-pack operation, for example once the traction battery 20 reaches the desired operating temperature range, it may be undesirable to connect both battery packs to the terminals 22, 24 of the battery 20 if the difference between the voltages of the first and second cell packs 402, 404 is too great as, for example this could result in the undesirable flow of current between the battery packs as the voltage equalizes and/or place excessive stress on the switching means when operated with a significant voltage drop across them. Thus, full-pack operation may only be resumed when the voltage difference between the battery packs 402, 404 is below the threshold amount.

In the case that a voltage differential between the battery packs 402, 404 is determined to be above the threshold amount when the first threshold internal battery temperature has been reached, the control system 26 may be configured to control the switching means to disconnect the battery pack having the lowest associated voltage from the traction bus 27 and connect the battery pack having the highest associated voltage. As electrical power is then drawn from the battery pack having the highest voltage, the voltage of this battery pack will gradually decline until the voltages are within the threshold amount and the full pack mode of operation can then be entered.

Figures 5 to 7 illustrate various control methods that may be performed by the control system 26 and applied to the switching means of the circuit 400 as described above.

Figure 5 illustrates a method 500 of controlling a circuit of a traction battery 20 comprising a first cell set 402 comprising a plurality of electrical cells 402a, 402b and a second cell set 404 comprising a plurality of electrical cells 404a, 404b, such as that illustrated in Figure 4. The method 500 comprises controlling 502 a switching means of the circuit 400 to electrically connect the first cell set 402 of the traction battery 20 to a traction bus 27 of the vehicle 10, determining 504 a temperature of at least a portion of the traction battery 20, and controlling 506 the switching means to electrically connect the second cell set 404 to the traction bus 27 of the vehicle 10 in dependence on the determined temperature of the at least a portion of the battery 20.

The method 500 of Figure 5 may further comprise controlling the switching means to electrically connect the second cell set 404 to the traction bus 27 of the vehicle 10 in response to determining that the temperature of the traction battery 20 is greater than a first threshold temperature.

Figure 6 illustrates a method 600 of controlling a circuit 400 of a traction battery 20 in conjunction with a coolant system of a vehicle 10. The method comprises circulating 602 coolant to a first cell set 402 of the traction battery 20, electrically connecting 604 the first cell set 402 to the traction bus 27; determining 606 whether a temperature of the first cell set 402 is greater than a second threshold temperature; and if so circulating 608 coolant to the first and second cell sets 402, 404 of the traction battery 20; determining 610 whether the temperature of the second cell set 404 is greater than a third threshold temperature; and if so electrically connecting 612 the second cell set 404 to the traction bus 27.

Figure 7 illustrates a method 700 of controlling a circuit of a traction battery 20 comprising a first cell set comprising a plurality of electrical cells and a second cell set comprising a plurality of electrical cells, such as that illustrated in Figure 4. The method comprises monitoring 702 a first parameter value associated with the first cell set 402 of the traction battery 20, monitoring 704 a second parameter value associated with the second cell set 404 of the traction battery 20, and controlling the switching means of the circuit to electrically connect 706 one of the first and second cell sets 402, 404 to the traction bus of the vehicle 10 in dependence on the first and second parameter values.

According to the method of Figure 7, the first and second parameters may comprise one of: a first voltage of the first cell set of the traction battery and a second voltage of the second cell set of the traction battery; a first temperature associated with the first cell set of the traction battery and a second temperature associated with the second cell set of the traction battery; or a first time in use value associated with the first cell set of the traction battery and a second time in use value associated with the second cell set of the traction battery.

For purposes of this disclosure, it is to be understood that the controller(s) 30 described herein can each comprise a control unit or computational device having one or more electronic processors. A vehicle 10 and/or a system thereof may comprise a single control unit or electronic controller or alternatively different functions of the controller(s) may be embodied in, or hosted in, different control units or controllers. A set of instructions could be provided which, when executed, cause said controller(s) or control unit(s) to implement the control techniques described herein (including the described method(s)). The set of instructions may be embedded in one or more electronic processors, or alternatively, the set of instructions could be provided as software to be executed by one or more electronic processor(s). For example, a first controller may be implemented in software run on one or more electronic processors, and one or more other controllers may also be implemented in software run on one or more electronic processors, optionally the same one or more processors as the first controller. It will be appreciated, however, that other arrangements are also useful, and therefore, the present disclosure is not intended to be limited to any particular arrangement. In any event, the set of instructions described above may be embedded in a computer-readable storage medium (e.g., a non-transitory computer-readable storage medium) that may comprise any mechanism for storing information in a form readable by a machine or electronic processors/computational device, including, without limitation: a magnetic storage medium (e.g., floppy diskette); optical storage medium (e.g., CD-ROM); magneto optical storage medium; read only memory (ROM); random access memory (RAM); erasable programmable memory (e.g., EPROM and EEPROM); flash memory; or electrical or other types of medium for storing such information/instructions.

It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

As used here 'module refers to a unit or apparatus that excludes certain parts/components that would be added by an end manufacturer or a user.

As used here, 'connected' means 'electrically interconnected' either directly or indirectly. Electrical interconnection does not have to be galvanic. Where the control system is concerned, connected means operably coupled to the extent that messages are transmitted and received via the appropriate communication means.

The term 'current' means electrical current. The term Voltage' means potential difference. The term 'series' means electrical series. The term 'parallel' means electrical parallel. 'Active and 'operational' generally mean closed circuit. The term power' means electrical power. The term 'charging' means electrical recharging of the battery.

The blocks illustrated in Figures 5, 6 or 7 may represent steps in a method 500, 600, 700 and/or sections of code in a computer program 36 configured to control an electrical power circuit as described above to perform the method steps. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some steps to be omitted or added in other examples. Therefore, this disclosure also includes computer software that, when executed, is configured to perform any method disclosed herein, such as that illustrated in Figures 5, 6 and 7. Optionally the computer software 36 is stored on a computer readable medium, and may be tangibly stored.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.

Features described in the preceding description may be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

CLAIMS1. A control system comprising one or more controllers for a traction battery of a vehicle, the traction battery comprising a first cell set comprising a plurality of electrical cells and a second cell set comprising a plurality of electrical cells, the traction battery being associated with switching means operable to independently connect one or both of the first and second cell sets to a traction bus of the vehicle, the control system comprising: input means for receiving a temperature signal indicative of a temperature of at least a portion of the traction battery; output means for outputting a control signal for controlling the switching means of the traction battery to electrically connect the first cell set to the traction bus; and processing means arranged, in dependence on the temperature signal indicative of the temperature of the at least a portion of the traction battery exceeding a first threshold temperature, to control the output means to output the control signal to cause the switching means associated with the traction battery to electrically connect the second cell set to the traction bus.
2. The control system according to claim 1, wherein the processing means is arranged to control the output means to output a second control signal to a coolant system of the vehicle to cause the coolant system to circulate coolant to one or both of the first cell set and the second cell set.
3. The control system according to claim 2, wherein the processing means is arranged to control the output means to output the second control signal to the coolant system to cause the coolant system to circulate coolant to the first cell set; and wherein the processing means is arranged, in dependence on the temperature signal indicative of the temperature of the at least a portion of the traction battery exceeding a second threshold temperature, to control the output means to output the second control signal to cause the coolant system to circulate the coolant to the first cell set and the second cell set.
4. The control system according to any preceding claim, wherein the processing means is configured to: determine that the temperature signal indicates that the temperature of the traction battery is below a third threshold temperature; and control the output means to output the control signal to cause the switching means of the traction battery to electrically connect the first cell set to the traction bus of the vehicle and to isolate the second cell set from the traction bus of the vehicle in dependence on the determination that the temperature of the traction battery is below the third threshold temperature.
The control system according to any preceding claim, wherein: the input means is arranged to: receive a first signal indicative of a first parameter value associated with the first cell set of the traction battery, and receive a second signal indicative of a second parameter value associated with the second cell set of the traction battery; and the processing means arranged to: control the output means to output the control signal to cause the switching means of the circuit to electrically connect one of the first and second cell sets to the traction bus of the vehicle in dependence on the first and second parameter values.
6. The control system of claim 5, wherein the processing means is arranged to: determine, in dependence on the first and second parameter values, a greater of the first and second parameter values; and control the output means to output the control signal to cause the switching means of the circuit to electrically connect one of the first and second cell sets to the traction bus of the vehicle in dependence on the determination of which of the first and second parameter values is greater.
7. The control system according to claim 7, wherein the first and second parameter values comprise a first voltage of the first cell set of the traction battery and a second voltage of the second cell set of the traction battery, and wherein the processing means is arranged to control the output means to output the control signal to cause the switching means of the circuit to electrically connect to the traction bus of the vehicle the cell set of the first and second cell set corresponding to the one of the first and second voltages determined to be greater.
8. The control system according to claim 5, wherein the processing means is arranged to: determine that a difference between the first parameter value and the second parameter value is less than or equal to a threshold value; and control the output means to output the control signal to cause the switching means of the circuit to electrically connect to the traction bus of the vehicle the first cell set and the second cell set in dependence on determining that the difference between the first parameter value and the second parameter value is less than or equal to the threshold value.
9. The control system according to claim 8, wherein the first and second parameter values comprise a first voltage of the first cell set of the traction battery and a second voltage of the second cell set of the traction battery and wherein the processing means is arranged to: in dependence on determining that the difference between the first voltage and the second voltage is greater than the threshold value, control the output means to output the control signal to cause the switching means of the circuit to electrically connect to the traction bus of the vehicle one of the first and second cell sets corresponding to the one of the first and second voltages determined to be greater.
10. The control system of any of claims 5, 6 and 8, wherein the first and second parameters comprise one of: a first voltage of the first cell set of the traction battery and a second voltage of the second cell set of the traction battery; a first temperature associated with the first cell set of the traction battery and a second temperature associated with the second cell set of the traction battery; or a first time in use value associated with the first cell set of the traction battery and a second time in use value associated with the second cell set of the traction battery.
11. The control system according to any preceding claim, wherein the temperature signal indicative of a temperature of at least a portion of the traction battery comprises a temperature signal indicative of a temperature of at least a portion of the first cell set; and wherein the processing means is arranged to control the output means to output the control signal to cause the switching means of the circuit to electrically connect the second cell set to the traction bus of the vehicle in dependence on the temperature of the first cell set.
12. The control system according to any of claims Ito 10, wherein the temperature signal indicative of a temperature of at least a portion of the traction battery comprises a temperature signal indicative of a temperature of at least a portion of the second cell set; and wherein the processing means is arranged to control the output means to output the control signal to cause the switching means of the circuit to electrically connect the second cell set to the traction bus of the vehicle in dependence on the temperature of the second cell set.
13. An electrical power system for a vehicle comprising the control system of any preceding claim, the electrical power system comprising: a traction battery comprising a first cell set comprising a plurality of electrical cells, a second cell set comprising a plurality of electrical cells, and switching means operable to independently connect one or both of the first and second cell sets to a traction bus of the vehicle.
14. The electrical power system according to claim 13, the control system comprising: a temperature sensing means for determining the temperature of at least a portion of the traction battery and outputting the temperature signal.
15. The electrical power system according to any of claims 13 to 14, the electrical power system comprising a traction bus arranged to provide electrical power to one or more traction motors.
16. A vehicle comprising the control system according to any of claims 1 to 12, or the electrical power system according to any of claims 13 to 15.
17. A method of controlling a circuit for a traction battery of a vehicle, the traction battery comprising a first cell set comprising a plurality of electrical cells and a second cell set comprising a plurality of electrical cells, the method comprising: controlling switching means of the circuit to electrically connect the first cell set of the traction battery to a traction bus of the vehicle; determining a temperature of at least a portion of the traction battery; and controlling the switching means of the circuit to electrically connect the second cell set to the traction bus of the vehicle in dependence on the determined temperature of the at least a portion of the traction battery.
18. The method according to claim 17, wherein controlling the switching means of the circuit to electrically connect the second cell set of the traction battery to the traction bus of the vehicle in dependence on the determined temperature of the at least a portion of the traction battery comprises controlling the switching means in response to determining that the temperature of the traction battery is greater than a first threshold temperature.
19. The method according to claim 17 or claim 18, comprising: controlling a cooling system to circulate coolant to the first cell set; monitoring a temperature of at least a portion of the first cell set; determining that the temperature of the at least a portion of the first cell set is greater than or equal to a second threshold temperature; and controlling the cooling system to circulate coolant to the first cell set and the second cell set in dependence on the determination that the temperature of the first cell set is greater than the second threshold temperature.
20. The method of any of claims 17 to 19, comprising: monitoring a temperature of at least a portion of the first cell set; and controlling the switching means of the circuit to electrically connect the second cell set to the traction bus of the vehicle based on the temperature of the first cell set.
21. The method of any of claims 17 to 19, comprising: monitoring a temperature of at least a portion of the second cell set; and controlling the switching means of the circuit to electrically connect the second cell set to the traction bus of the vehicle based on the temperature of the second cell set.
22. The method of any of claims 17 to 21, comprising: monitoring a first parameter value associated with the first cell set of the traction battery; monitoring a second parameter value associated with the second cell set of the traction battery; and controlling the switching means of the circuit to electrically connect one of the first and second cell sets to the traction bus of the vehicle in dependence on the first and second parameter values.
23. The method of claim 22, comprising: determining that a difference between the first parameter value and the second parameter value is less than a threshold value; and controlling the switching means of the circuit to electrically connect the first cell set and the second cell set to the traction bus of the vehicle in dependence on determining that a difference between the first parameter value and the second parameter value is less than the threshold value.
24. The method of claim 22 or 23, wherein the first and second parameters comprise one of: a first voltage of the first cell set of the traction battery and a second voltage of the second cell set of the traction battery; a first temperature associated with the first cell set of the traction battery and a second temperature associated with the second cell set of the traction battery; or a first time in use value associated with the first cell set of the traction battery and a second time in use value associated with the second cell set of the traction battery.
25. Computer software which, when executed by a computer, is arranged to perform a method according to any of claims 17 to 24; optionally the computer software is stored on a computer readable medium.