Vibration-assisted charging of electrified vehicle batteries

Abstract

The present disclosure relates to an electrified vehicle (301, 401, 501), comprising: a battery pack (303, 403, 503), which is suitable for being connected to a power source (311, 411, 511) for charging, wherein the battery pack comprises a plurality of storage batteries; a vibration generating device (305, 415, 517), which is arranged outside the battery pack and is arranged to generate vibrations of the plurality of storage batteries when the vibration generating device is in a vibration operating state; and a control unit (307, 407, 507), wherein the control unit is configured to ensure that the vibration generating device is in a vibration operating state at least for the duration of charging of the battery pack; wherein the vibration generating device is arranged to perform functions other than generating vibrations when in a main operating state. The present disclosure also relates to a method for charging a battery pack of such an electrified vehicle.

Description

Technical Field

[0001] The present invention relates to an electrified vehicle arranged to provide rapid charging of a vehicle battery. The present invention also relates to a method of charging a vehicle battery in such an electrified vehicle. Background Art

[0002] The vehicle industry is experiencing a continuing trend toward electrification, in part to meet the challenges posed by increasingly stringent exhaust emissions regulations. As electric motors are increasingly used as the primary propulsion system in vehicles, larger batteries are required to provide longer all-electric range or "electrical autonomy."

[0003] One factor limiting the more widespread adoption of widely electrified vehicles is the time required to charge larger capacity batteries. For example, fully charging a plug-in hybrid vehicle using a home charger typically takes several hours. Charging times can be shortened by using specific charging infrastructure that can provide higher charging rates. However, the achievable charging rate (C-rate) is limited not only by the availability of infrastructure, but also by the chemistry used in the battery, which fundamentally limits the achievable or optimal charging rate.

[0004] Modern hybrid or fully electrified vehicles typically use lithium-ion batteries. Charging with high C rates depletes the concentration of lithium ions available for insertion near the electrode surface, because lithium ions diffuse so slowly in the electrolyte that a concentration gradient forms near the surface. Even if lithium ions are present in large quantities in the electrolyte, they cannot enter the redox reactions occurring at the electrode. For most electrochemical cells, mass transfer by diffusion is the most dominant process in the electrolyte. Given time, as new lithium ions diffuse to the electrode surface, the concentration gradient that forms disappears and the insertion reaction can proceed.

[0005] The slow diffusion rate of lithium ions in the electrolyte and active materials increases the different polarizations (concentration, ohmic and activation) in the cell. This results in a voltage drop related to the C-rate during charging, leading to an overpotential and related electrolyte degradation, or simply to a loss of capacity because the cut-off voltage will be reached earlier. In addition, long-term charging at high C-rates leads to an increase in the cell temperature and a corresponding increase in temperature-related degradation processes in the cell. Although described here with respect to lithium-ion cells, similar concentration gradients can occur in any electrochemical cell, leading to similar cell degradation and non-ideal capacity issues.

[0006] To address these problems, some approaches have been proposed. For example, hybrid charging protocols are known, in which the battery is quickly charged for a short period of time, to a certain predetermined state of charge (SOC), and then further charged at a slower rate. This protocol gives the concentration gradient time to disappear.

[0007] US 5436548 describes a battery charging and discharging system in different embodiments. The battery charging system includes a power source and a member for vibrating the battery. The vibration member can be located in the battery itself or can be located outside the battery and electrically connected to the power source. The vibration member vibrates the battery during charging to increase the deliverable capacity of the battery. In another embodiment, a battery discharging system is described. Here, the battery is vibrated during discharge to increase the available capacity. In the battery discharging system, the vibration source can be located in the battery packaging itself, or in a load or electrical device powered by the battery.

[0008] There remains a need for improved components and methods for charging vehicle battery packs. Summary of the invention

[0009] The inventors of the present invention have discovered some shortcomings of the components and methods of charging vehicle battery packs in the prior art. As described in the background section, standard fast charging accelerates battery aging and reduces the available capacity of the battery pack. Methods based on fast / slow hybrid charging protocols do not allow for continuous use of high charging rates, nor can they fully charge the battery at high rates, nor can they provide fast charging for the battery at low temperatures where the transfer of lithium ions is even slower, regardless of the charging protocol. Known methods of utilizing vibration components when charging batteries, such as the method in US 5436548, require dedicated vibration components in the battery or electrically connected to the battery power source. Such dedicated vibration components increase the weight and complexity of the battery charging system, thereby increasing cost and reducing the deliverable energy per unit weight, which is a key consideration in the production of electrified vehicles. US 5436548 also discloses a battery discharge system in which the vibration source can be located in a load or electrical device powered by the battery. However, US 5436548 does not envisage the use of such a discharge system during charging of the battery, presumably because if a vibrating member were used during charging it would constitute an undesirable parasitic load on the battery which would discharge the battery simultaneously as it is being charged.

[0010] The inventors have identified a need for a means for charging a battery pack for an electrified vehicle that would allow for extended charging times at high C-rates, even at lower temperatures, and that would not require the use of a vibrating means specifically designed to facilitate charging of the battery.

[0011] It is therefore an object of the present invention to provide a method for charging a battery pack of an electrified vehicle that addresses one or more of these issues, thereby helping to overcome or at least alleviate some of the above-mentioned disadvantages.

[0012] This object is achieved by an electrified vehicle as disclosed in the appended claims.

[0013] Electrified vehicles include:

[0014] - a battery pack adapted to be connectable to a power source for charging, wherein the battery pack comprises a plurality of accumulator cells.

[0015] - a vibration generating device arranged outside the battery pack and arranged to generate vibrations of the plurality of storage batteries when the vibration generating device is in a vibrating operating state; and

[0016] - a control unit, wherein the control unit is configured to ensure that the vibration generating device is in a vibrating operating state at least for the duration of the charging of the battery pack.

[0017] Therein, the vibration generating means is arranged to perform a function other than generating vibrations when in the primary operating state.

[0018] Electrified vehicles accelerate mass transfer in batteries by adding motion to the system during charging, providing convective mass transfer, making mass transfer less dependent on the slow diffusion of ions. By increasing motion, the charge rate is not limited by concentration gradients. This allows not only repeated rapid charging, but also rapid charging at lower temperatures where diffusion rates are further slowed.

[0019] An electrified vehicle utilizes a vibration generating device that is arranged to perform a function other than generating vibrations when in a primary operating state. Such further functions may be, for example, assisting in propelling the vehicle, assisting in steering the vehicle, or assisting in improving the road characteristics of the vehicle. By utilizing such a vibration generating device that already has an existing function in the electrified vehicle, the charging of the battery pack may be improved while avoiding, to a certain extent, the added weight, cost and complexity of known solutions.

[0020] The primary operating state may be a vibrating operating state, that is, the vibration generating means may generate vibrations when performing its primary function. For example, an internal combustion engine tends to generate a certain degree of vibration when operating. This enables the battery to be vibrated in a simple, robust and cost-effective manner, as the means for doing so already exist to some extent and generate vibrations as a by-product of its normal operation.

[0021] The main operating state may generate substantially no vibrations. This allows accurate control of the vibrations of the battery, since the vibrations of the vibration generating device do not occur unintentionally, but only through the purposeful use of the vibrating operating state.

[0022] The vibration generating device may be arranged to have a secondary operating state, the secondary operating state being a vibrating operating state, the secondary operating state being configured to provide a greater level of vibration of the plurality of batteries relative to the primary operating state. This means that where the primary operating state generates vibrations, a greater amount of vibration is generated in the secondary operating state, whereas where no vibrations are generated in the primary operating state, the secondary operating state acts to generate vibrations. This allows a greater degree of control over the vibrations to which the batteries are subjected.

[0023] The electrified vehicle may further comprise a mechanical link arranged to be actuated when the vibration generating device is in the secondary operating state so as to generate vibrations of the plurality of batteries. This allows conveniently vibrating the batteries by a device that may normally generate a mechanical output but not necessarily vibrations.

[0024] The vibration generating means may be an internal combustion engine. Since internal combustion engines tend to vibrate to some extent when in use, this allows the battery to be vibrated in a simple, robust and cost-effective manner, since the means for vibrating already exist and generate vibrations as a byproduct of their normal operation. Furthermore, since the internal combustion engine is fed with a separate energy source (fuel), it does not constitute a parasitic load on the battery or the charging equipment when charging the battery.

[0025] The vibration generating device may be one or more electric motors or one or more actuators in an active suspension system or a power steering system. Such components are capable of generating precisely controlled vibrations of the battery.

[0026] The electrified vehicle may be a hybrid vehicle. A hybrid vehicle may include both a battery that needs to be charged and an internal combustion engine that can be used to generate vibrations. Therefore, the present invention is easily applicable to such a vehicle.

[0027] Each battery may include a liquid electrolyte. Liquid electrolyte batteries are mature, the mass transfer characteristics of the electrolyte are well modeled, and are known to be easily improved by the present invention. Each battery may be of the lithium ion type. Lithium ion batteries are commonly used in electrified vehicles.

[0028] According to the attached claims, the above object is also achieved by a method for charging a battery pack of an electrified vehicle. The battery pack comprises a plurality of storage batteries, and the electrified vehicle comprises a vibration generating device. The vibration generating device is arranged outside the battery pack and is arranged to generate vibrations of the plurality of storage batteries when in a vibration operating state, and is arranged to perform a function other than generating vibrations when in a main operating state.

[0029] The method comprises the following steps:

[0030] - arranging the battery pack to be connected to a power source for charging;

[0031] - charging the battery pack during a period of time; and

[0032] The vibration-generating device is operated in a vibrating operating state at least for the duration of the charging of the battery pack.

[0033] As described above, by vibrating the secondary battery using the vibration generating device during charging, the charging performance of the battery is improved.

[0034] The vibration generating device may be operable in a secondary operating state, which is a vibrating operating state, for at least the duration of charging of the battery pack.

[0035] When the vibration generating device is an internal combustion engine, the internal combustion engine can be operated without propelling the electrified vehicle for the duration of the charging of the battery pack. This allows charging from a fixed external charging device (such as a charging station) while using the internal combustion engine as the vibration generating device.

[0036] The vibration generating device can be operated in a vibrating operating state for a plurality of time periods during the duration of the charging of the battery pack. This allows the charging of the battery pack to be improved while avoiding excessive vibration of the battery pack, vibrating only temporarily when insufficient mass transfer results in unsatisfactory charging performance.

[0037] The vibration generating device may be operated in a vibrating operating state for a total period of at least 30% of the duration of the battery pack's charge, such as at least 50% of the duration of the battery pack's charge, or such as at least 70% of the duration of the battery pack's charge, or such as at least 90% of the duration of the battery pack's charge. By vibrating the battery for a suitable period of time during charging, charging may be improved while avoiding excessive vibration of the battery and other vehicle components.

[0038] Further objects, advantages and novel features of the present invention will become apparent to those skilled in the art from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] For a more complete understanding of the present invention and its further objects and advantages, the following detailed description should be read in conjunction with the accompanying Figure 1 In the accompanying drawings, like reference numerals designate similar items in the various figures, and wherein:

[0040] Figure 1 Schematically shows the achievable capacity of a battery at different charging rates.

[0041] Figure 2 is a flow chart schematically illustrating a method of charging a battery pack of an electrified vehicle.

[0042] Figure 3 An electrified vehicle according to one embodiment of the present invention is schematically illustrated.

[0043] Figure 4 An electrified vehicle according to another embodiment of the present invention is schematically illustrated.

[0044] Figure 5 An electrified vehicle according to yet another embodiment of the present invention is schematically illustrated. DETAILED DESCRIPTION

[0045] The present disclosure is directed to an electric vehicle including a battery pack, a vibration generating device, and a control unit.

[0046] Electrified vehicles

[0047] By electrified vehicle is meant any vehicle that uses an electric motor to propel the vehicle to some extent. This includes fully electric vehicles, such as battery electric vehicles, and hybrid electric vehicles, such as plug-in hybrid vehicles, full hybrid vehicles, and mild hybrid vehicles. The electrified vehicle may preferably be a plug-in vehicle, such as a battery electric vehicle or a plug-in hybrid vehicle. The vehicle may be any type of vehicle, including but not limited to heavy vehicles (such as trucks or buses), light commercial vehicles, motor vehicles, and motorcycles.

[0048] Battery Pack

[0049] A battery pack in an electrified vehicle is typically used to power a propulsion motor in the electrified vehicle. The battery pack typically includes a plurality of battery modules, wherein each module includes a plurality of individual batteries. The battery pack also typically includes a controller, such as a battery and thermal management system, and a housing for encapsulating all of the battery pack components. The battery pack is adapted to be connectable to a power source for charging. The power source may be an external power source, such as a charging station, or an internal power source, such as a generator. The battery pack may use any battery chemistry, such as lithium-ion batteries or nickel-metal hydride batteries, but preferably may be of the lithium-ion type. The battery may use a solid or liquid electrolyte, but liquid electrolytes are preferred, in part due to the wide commercial availability and the ease with which convective mass transfer can be induced in liquid electrolytes.

[0050] Vibration generating device

[0051] The vibration generating device is arranged outside the battery pack. The so-called vibration generating device refers to a device that serves as a source of mechanical energy that causes the battery pack / battery to vibrate. That is, the vibration generating device does not simply transmit externally generated vibrations, such as road vibrations, and therefore, the vehicle tires, suspension and chassis should not be considered as vibration generating devices. Merely transmitting externally generated vibrations will result in a system with very limited practicality (e.g., requiring vehicle movement), and it is likely that sufficient vibration will not be generated even under the most favorable circumstances. The vibration generating device is arranged to perform functions other than generating vibrations when in the main operating state, and is arranged to generate vibrations of the multiple batteries when in the vibration operating state.

[0052] By "arranged to generate a function other than vibration when in the primary operating state" is meant a device that satisfies existing requirements in an electrified vehicle over and above the function of generating vibrations of the plurality of batteries when the device is operating. For example, the primary function of the vibration generating device may be to assist in propelling the vehicle, assist in steering the vehicle, or assist in maintaining good handling of the vehicle. The term "in addition to" is intended to include "in addition to" and "together", i.e., the vibration generating device may generate vibrations when in the primary operating state, but does not necessarily generate vibrations.

[0053] By "arranged to generate vibrations of the plurality of batteries when in a vibrating operating state" is meant that the vibration generating device causes the batteries to vibrate when in a vibrating operating state. It should be noted that the vibration generating device itself does not necessarily vibrate when in a vibrating operating state, although it can do so. For example, the vibration generating device itself can vibrate and transmit the vibrations to the batteries via other vehicle components (such as the chassis). However, it is also conceivable that the vibration generating device can generate motion, such as reciprocating motion or rotational motion, which can be converted into vibrating motion of the batteries via a connecting rod.

[0054] For example, the vibration generating device may be selected from a list including, but not limited to, an internal combustion engine, an electric propulsion motor, an actuator in an active suspension system, or an actuator in a power steering system. The actuator may be a hydraulic, electro-hydraulic, or electric actuator.

[0055] The vibration generating device may generate vibrations as a side effect of its primary function in a primary operating state. For example, an internal combustion engine inevitably generates a certain degree of vibration whenever it is running. Such a vibration generating device may be arranged to have a secondary operating state, whereby an enhanced degree of vibration is generated. For example, in the case of an internal combustion engine, it is well known that the vibrations generated are greater during engine stopping and / or starting, or whenever the engine is not burning unequally on all cylinders, so a secondary operating state may be provided which exploits this effect during the charging of the battery.

[0056] Alternatively, the vibration generating device generally does not produce significant vibrations in the main operating state. For example, this is the case with actuators in power steering or active suspension systems. In this case, the vibration generating device can be arranged to provide a secondary operating state, whereby the vibration of the storage battery is generated. This can be achieved by utilizing the vibration generating device to generate relatively non-specific vibrations of at least a portion of the vehicle, such as by using an active suspension actuator during charging to vibrate the portion of the vehicle closest to the battery pack. However, the specific vibration of the battery pack, a single battery module or a single storage battery can be achieved by arranging a connecting rod that can be actuated during the charging of the battery between the vibration generating device and the battery pack / module / battery. The connecting rod can be, for example, a mechanical connecting rod between the vibration generating device and the battery pack / module / battery. The mechanical connecting rod can be arranged to be actuated only when the vibration generating device is in the secondary operating state, thereby potentially avoiding obstructing the function of the vibration generating device in its main operating state.

[0057] Control unit

[0058] The control unit is configured to ensure that the vibration generating device is in a vibrating operating state at least for the duration of the charging of the battery pack. The control unit may also be configured to monitor and regulate the charging of the battery pack.

[0059] Battery vibration

[0060] Vibration of a battery pack, battery module or battery can be detected using one or more sensors, such as accelerometers such as piezoelectric or MEMS accelerometers. Alternatively, during charging, vibration of the battery can be detected indirectly by observing the effect on the charging behavior of the battery pack.

[0061] Figure 1The achievable capacity (% capacity - y axis) of a battery at various charging rates (C x axis) is schematically shown. The charging rate C is the rate required to charge or discharge a battery relative to its maximum capacity. 1C is the rate required to discharge or charge a battery in one hour, so if a battery has a capacity of 50 ampere hours, 1C is a rate of 50 amperes and 2C is a rate of 100 amperes. Line 101 shows the typical charging behavior in a battery with only diffusive mass transfer in the electrolyte (i.e. a battery at rest). Line 103 shows the typical charging behavior of a battery with both diffusive and convective mass transfer mechanisms in the electrolyte (i.e. a battery that is vibrating). From Figure 1 It can be seen that for both the vibrating (line 103) and non-vibrating (line 101) cells, the maximum capacity is only achieved at low C-rates. For lithium-ion cells with liquid electrolytes, this is typically in the range of about 0.5 or lower. In the non-vibrating cell (line 101), the available capacity drops quite quickly as the C-rate increases. However, in the vibrating cell (line 103), the drop in available capacity as the C-rate increases is less pronounced, i.e., at higher C-rates, the vibrating cell shows better charging performance than the non-vibrating (stationary) cell.

[0062] Method for charging a battery pack

[0063] Figure 2 The flowchart schematically shows a method for charging a battery pack of an electrified vehicle. When charging the battery pack, the following steps are performed:

[0064] - Arranging the battery pack to be connected to a power source for charging (S201);

[0065] - charging the battery pack during a period of time (S202); and

[0066] - operating the vibration generating means in a vibrating operating state (S203) at least for the duration of the charging of the battery pack.

[0067] The power source may be an external power source, such as a charging station for an electrified vehicle, or it may be an internal power source, such as a generator for a series hybrid vehicle. If the power source is an internal power source, the battery pack may be permanently or semi-permanently arranged to be connected to the power source.

[0068] Once the battery pack is arranged to be connected to the power source, charging can begin. As mentioned above, for a battery pack charged at a rate of 1C, the nominal charging duration is 1 hour, for a charging rate of 0.5C, the nominal charging duration is 2 hours, and so on.

[0069] The control unit is active during the charging duration to ensure that the vibration generating device is in a vibrating operating state for at least some periods of time during charging. This may require the control unit to start the vibrating operating state, for example by switching on the internal combustion engine. However, in some cases, the vibrating operating state may already be in progress, for example in the case of a series hybrid vehicle, whereby the internal combustion engine is operated to charge the battery pack.

[0070] The vibration generating device may be in a vibrating operating state substantially throughout the duration of charging, such as at least 90% of the duration of charging of the battery pack. However, it may be sufficient to vibrate the battery in a shorter proportion of the duration of charging, such as at least 70%, at least 50%, or at least 30%. During charging, the battery may be vibrated in a single time period, or the vibration may be performed in multiple time periods, such as a fixed number of times and duration per charge or a fixed number of times and duration per unit time. Thus, the total time period is the sum of the individual vibration time periods.

[0071] The control unit may also be arranged to monitor the charging characteristics of the battery pack and control the vibration of the accumulator based on the charging characteristics of the battery pack. In this way, the accumulator needs to be vibrated only when the charging characteristics indicate that a substantial concentration gradient has formed in the electrolyte of the battery.

[0072] Charging can be performed at a variable rate using vibration and a combination of fast and slow charging schemes. Charging can be performed for a fixed period of time, or charging can be stopped when a specified current or voltage limit is reached.

[0073] The present invention will now be further illustrated with reference to the illustrated embodiments.

[0074] Figure 3 An electrified vehicle according to one embodiment of the present invention is schematically shown. The electrified vehicle 301 is a hybrid vehicle, comprising a battery pack 303, an internal combustion engine 305, a control unit 307, and an electric motor 309. The battery pack 303 is connected to a charging station 311 via a power line 313. During charging, the internal combustion engine 305 is periodically started, operated, and stopped by the control unit 307 to generate vibrations. These vibrations are propagated through the vehicle to the battery pack 303, thereby vibrating the storage cells within the battery pack 303. During this process, the vehicle transmission (not shown) can be decoupled from the drivetrain to operate the internal combustion engine 305 without propelling the vehicle 301.

[0075] Figure 4An electrified vehicle according to another embodiment of the present invention is schematically shown. The electrified vehicle 401 is a battery electric vehicle comprising a battery pack 403, a control unit 407 and an electric motor 409. The electrified vehicle further comprises an active suspension comprising an electromechanical actuator 415. The battery pack 403 is connected to a charging station 411 via a power line 413. During charging, the electromechanical actuator 415 is systematically actuated by the control unit 407 to generate vibrations. These vibrations are propagated through the vehicle to the battery pack 403, thereby vibrating the storage cells within the battery pack 403.

[0076] Figure 5 An electrified vehicle according to another embodiment of the present invention is schematically shown. The electrified vehicle 501 is a battery electric vehicle, comprising a battery pack 503, a control unit 507 and an electric motor 509. The electric vehicle also comprises a power steering device, which comprises an electromechanical actuator 517. During charging, a mechanical link 519 couples the electromechanical actuator 517 to the housing of the battery pack 503. The battery pack 503 is connected to a charging station 511 via a power cord 513. During charging, the electromechanical actuator 517 is periodically actuated by the control unit 507 to generate motion, which is transmitted to the housing of the battery pack 503 by the mechanical link 519, thereby vibrating the storage cells within the battery pack 503.

Claims

1. An electrified vehicle (301, 401, 501), comprising: - a battery pack (303, 403, 503) adapted to be connectable to a power source (311, 411, 511) for charging, wherein the battery pack comprises a plurality of storage batteries; - a vibration generating device (305, 415, 517) arranged outside the battery pack and arranged to generate vibrations of the plurality of storage batteries when the vibration generating device is in a vibration operating state; and - a control unit (307, 407, 507), wherein the control unit is configured to ensure that the vibration generating device is in a vibration operating state at least for the duration of charging of the battery pack; wherein the vibration generating device is arranged to perform functions other than generating vibrations, the vibration generating device having a primary operating state and a secondary operating state, wherein the primary operating state substantially generates no vibrations, and the secondary operating state is a vibration operating state.

2. The electrified vehicle according to claim 1, wherein: The electrified vehicle further comprises a mechanical link (519) between the battery pack (303, 403, 503) and the vibration generating device, which is arranged to be actuated when the vibration generating device (517) is in the secondary operating state so as to generate vibrations of the plurality of storage batteries.

3. The electrified vehicle according to claim 2, wherein: The vibration generating means is one or more electric motors.

4. The electrified vehicle according to claim 1 or 2, wherein: The vibration generating device is one or more actuators in an active suspension system (415) or a power steering system (517).

5. The electrified vehicle according to any one of claims 1 to 3, wherein: Electrified vehicles are hybrid vehicles.

6. The electrified vehicle according to any one of claims 1 to 3, wherein: Each battery includes a liquid electrolyte.

7. The electrified vehicle according to any one of claims 1 to 3, wherein: Each battery is of the lithium-ion type.

8. A method for charging a battery pack (303, 403, 503) of an electrified vehicle (301, 401, 501), wherein: The battery pack includes a plurality of storage batteries, and the electrified vehicle includes a vibration generating device (305, 415, 517), which is arranged outside the battery pack and is arranged to generate vibrations of the plurality of storage batteries when in a vibration operation state, the vibration generating device having a primary operation state and a secondary operation state, the primary operation state substantially generating no vibration, the secondary operation state being a vibration operation state, wherein the method comprises the following steps: - arranging the battery pack to be connected to a power source (311, 411, 511) for charging; - charging the battery pack during a time period; and - operating the vibration generating device in the vibration operation state for at least the duration of the charging of the battery pack.

9. The method according to claim 8, wherein: The vibration generating device operates in a vibrating operating state for a plurality of time periods during the duration of the battery pack charging.

10. The method according to claim 8 or 9, wherein: The vibration generating device operates in the vibration operating state for a total time period of at least 30% of the duration of the battery pack's charge, such as at least 50% of the duration of the battery pack's charge, such as at least 70% of the duration of the battery pack's charge, such as at least 90% of the duration of the battery pack's charge.

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