Field of invention

The invention relates to an energy storage system for use in an electrical vehicle.

The invention also relates to an electrical vehicle.

The invention also relates to a portable rechargeable energy storage unit for storing electrical charge. Technical Background

A problem with prior art electrical vehicles is that it is difficult for users who do not have access to dedicated or private parking spaces to recharge their vehicle. Furthermore, a car needs to stay connected to a charging station when charging, which puts restriction on the usability of the car.

There exist a number of different prior art documents related to different battery configurations.

One such document is DE102009014386A1 , wherein energy storage for supplying energy to traction network of electric vehicle is described. The energy storage has a battery unit coupled to a network by a converter, wherein the converter is implemented as two mono-directional converters having opposite energy transfer directions.

Another such document is EP2894058A1 , wherein a portable compound battery system is described. The system comprises at least one or more portable high energy battery sets, a load information centre, a fixed high power battery set and a variable output power compound battery

management module, wherein the portable high energy battery sets convert the output voltage by means of the variable output power compound battery management module including a variable output power DC/DC converter and then parallel with the high fixed high power battery set.

Another document is EP2372864A1 . The system described therein has a controller for driving operation of an electric motor e.g. brushless direct current motor, and a set of power type accumulators e.g. lithium type accumulators or nickel-metal hydride type accumulators, for powering the motor. A base receives a set of energy type accumulators in a removable manner. A direct current converter links the set of energy type accumulators to the set of power type accumulators. A central control unit controls the direct current converter.

Another document is US2013282472A1 , wherein methods and systems for providing charge options to drivers of electric vehicles are provided. One method includes receiving data concerning charge providing availability from charge locations and receiving a request from processing logic of an electric vehicle, the request identifying a desire to obtain charge. The method includes determining a current location of the electric vehicle and determining identification of charge locations in proximity to the electric vehicle. The method further includes determining any sponsored rewards offered by the charge locations and communicating to the electric vehicle a path to one of the charge locations, where the path is identified with a sponsored reward offered at the charge location if the path is selected and charge is obtained. The method can be processed by a server and paths are communicated to vehicles to alert drivers of the electric vehicles of rewards and discounts if charge is determined from certain locations. Summary of invention

It is an object of the invention to provide an improved energy storage system for an electrical vehicle.

This object has been achieved by an energy storage system for use in an electrical vehicle, the energy storage system comprising

a first, a second and a third rechargeable storage unit for storing electrical charge,

wherein the first rechargeable storage unit is selectably connectable in series with either the second or the third rechargeable storage unit, and

wherein the second and the third rechargeable storage unit are selectably connectable to an electrical motor, and

wherein, when the first rechargeable storage unit is connected in series with the second rechargeable storage unit, the third rechargeable storage unit is connected to the electrical motor, or vice versa, thereby allowing one of the second or third rechargeable storage units to be charged by the first rechargeable storage unit while the other of the second or third rechargeable storage units drives the electrical motor. By having the first rechargeable storage unit connected in series to a second rechargeable storage unit, while the third rechargeable storage unit is powering the motor, a more efficient system is provided. The same

advantages may be achieved if the first rechargeable storage unit is connected to the third rechargeable unit while the second rechargeable storage unit is powering the motor.

Using the present inventive concept, the motor may operate at a nominal voltage level since only one rechargeable storage unit is connected to the motor at any given time. This solution therefore alleviates the problem of having to adjust the voltage to the nominal voltage level of the motor between the following cases: one voltage level using a second/third energy storage unit and one voltage level using a first energy storage unit serially connected to a second/third energy storage unit. The problem may be solved using a converter, but adds weight and cost as well as sacrificing energy efficiency of the vehicle and the energy storage system.

There are various other advantages to using the presented solution. For example, by having a first rechargeable storage unit selectably connected to the second and third rechargeable storage unit, optimisation of the charging and discharging of the different energy storage units may be achieved. For example, it may be desirable to wear out one energy storage unit faster than the other. Furthermore, the first rechargeable storage unit may be used to keep the second and third rechargeable storage units at a desired energy level.

Further, as the second and third rechargeable storage units are separated, the units may be of different types, such as having one unit optimised for power and one unit optimised for energy density.

The first rechargeable storage unit may be removable and portable allowing the first rechargeable storage unit to be removed and carried to an electrical outlet. A portable first rechargeable storage unit allows for charging outside the proximity of the vehicle. For example, the first rechargeable storage unit may be charged in the office, residence, public areas etc.

Furthermore, the number of visits to a charging station may be reduced by using a portable energy storage unit. A portable first rechargeable storage unit may also be used to power other electrical products such as

entertainment systems or electrical tools. Additionally, the portable first rechargeable storage unit may replace units in other cars that may have stranded due to low power. The first rechargeable storage unit for storing electrical charge may be a rechargeable battery.

The second and third rechargeable storage units for storing electrical charge may be rechargeable batteries.

The second rechargeable storage unit may be configured to optimize output efficiency for providing a long range for an electrical vehicle and the third rechargeable storage unit is configured to provide a high power output.

The decision of which energy storage unit to draw power from may be based on various factors such as driver behaviour, road conditions, traffic, distance, speeds etc.

The first rechargeable storage unit may be chargeable in a mains outlet, preferably in a two phase mains outlet for home use. A user may conveniently charge the first rechargeable storage unit at her home or in the office. The voltage of the first rechargeable storage unit may further match the voltage of a home outlet alleviating the need for extra converters. In this case, the second and third rechargeable storage units would treat the first rechargeable storage unit as a normal outlet.

The first rechargeable storage unit may be configured to operate at a voltage lower than the operating voltage of the second and third rechargeable storage units. For example, a lower nominal voltage of the first rechargeable storage unit may result in a safer battery.

The first rechargeable storage unit may be configured to have a maximum stored energy being less than 50%, preferably less than 25%, of a maximum stored energy of the second rechargeable storage unit. A relative small first rechargeable storage unit enables faster charging and lighter weight.

The invention also relates to an electrical vehicle comprising an energy storage system according to the above.

The invention also relates to a portable rechargeable storage unit for storing electrical charge, the portable rechargeable storage unit being configured to be removable from an energy storage system of an electrical vehicle and to be portable, thereby allowing the portable rechargeable storage unit to be removed and carried to an electrical outlet, wherein the portable rechargeable storage unit is configured to be connected in series with a rechargeable storage unit installed in the electrical vehicle thereby allowing the portable rechargeable storage unit to charge the rechargeable storage unit installed in the electrical vehicle. Brief description of the drawings

The invention will by way of example be described in more detail with reference to the appended schematic drawings, which shows a presently preferred embodiment of the invention.

Figure 1 discloses an energy storage system.

Figure 2 discloses a portable rechargeable storage unit forming part of the energy storage system of figure 1 .

Figure 3 discloses the motor of the electrical vehicle powered by a second battery or the second battery being charged by regenerative braking.

Figure 4 discloses the motor of the electrical vehicle powered by a third battery or the third battery being charged by regenerative braking.

Figure 5 discloses the portable battery charging the third battery, or vice versa.

Figure 6 discloses the portable battery being charged via the on-board charger.

Figure 7 discloses the portable battery being charged by regenerative braking or the electrical vehicle being driven by power from the portable battery.

Detailed description of preferred embodiments

The energy storage system 1 for use in an electrical vehicle is schematically shown in figure 1 . The system 1 comprises in short first a portable rechargeable storage unit 4, a second rechargeable storage unit 2 and a third rechargeable storage unit 3. The storage units 2, 3, 4 are configured to store electrical charge. The storage units 2, 3, 4 are preferably rechargeable batteries. The second and third batteries 2, 3 are typically arranged to be fixed in the vehicle, but may be removable. However, in the preferred design are they not easily removable and portable to the same extent as the portable battery 4. Typically, the second and third batteries 2, 3, are significantly larger and comparably stationary. The portable battery 4 may e.g. be configured to store a maximum energy of 2kWh. The second and third batteries 2, 3, may e.g. be configured to store a maximum energy of 8kWh. However, it may be noted that other combinations of maximum energies are contemplated. It may e.g. be noted that the second and third batteries 2, 3, do not need to have the same maximum energy. The system 1 further comprises a control unit 5. The control unit 5 preferably has the hardware components and systems to support and enable the functional content of the system 1 . The control unit 5 preferably also has the software functions and algorithms to support and enable the functional content of the system 1 .

The system 1 is further connected to (or may alternatively be said to include a charger 6). The charger 6 may be an on-board charger. The charger 6 may be a one-directional charger for charging the batteries 2, 3, 4 of the system 1 . The charger 6 may alternatively be a bi-directional charger. The bi- directional charger 6 may thus be used not only to charge the batteries 2, 3, 4 but also to charge a separate chargeable storage unit (not shown) for storing electrical charge or to provide electrical power to any kind of electrical apparatus. Thereby the electrical vehicle may be used as an accumulator of electrical charge.

The system 1 is designed to drive an electrical load 7, such as one or more electrical driving motor(s) 7 of an electrical vehicle. The system 1 is also designed to provide electrical power to other electrical systems of the electrical vehicle. It may be noted that there may be various electrical components between the control unit 5 and the motor 7. One such electrical component may e.g. be an inverter. Also or as an alternative, the motor 7 may comprise various electrical components, such as an inverter.

The system 1 further comprises a first converter 8. The first converter 8 is connected between the portable battery 4 and the control unit 5. The system 1 further comprises a second converter 9. The second converter 9 is connected between the control unit 5. The first and second converters 8, 9 preferably each comprise an inverter. The converters 8 and 9 are

schematically shown as separate units. However, the first converter 8 may be integrally formed with the battery 4.

The portable rechargeable storage unit 4 will now be described in more detail. The portable rechargeable storage unit 4 may be embodied as a battery pack comprising one or more rechargeable battery cells. In this embodiment the rechargeable storage unit 4 is configured to store electrical charge chemically, and to transfer the stored electrical charge to an external electrical circuit, for instance one containing the electric load 7. It is however possible to implement the portable rechargeable storage unit 4 in any way suitable for transfer of energy to an external electrical circuit. This description will exemplify the rechargeable storage unit 4 as a battery pack comprising one or more rechargeable battery cells, and the description will henceforth refer to the portable rechargeable storage unit 4 as a "battery pack 4". The battery pack 4 may be connected electrically to a first DC/DC converter 8 of the energy storage system 1 . This connection may be by way of an electrical socket similar to ones used as mains outlets in home use, by a proprietary electrical socket designed for the purpose, a IEC 60320 compliant connection or any other suitable locking or non-locking electrical connection. The battery pack may be mounted inside a casing in order to protect it from dirt and humidity. The battery pack may be provided with one or more carrying straps to facilitate carrying the disconnected battery pack to an electrical outlet for charging. Such carrying straps may of course also be fixed or removable. The battery pack 4 comprises one or more electrical connectors suitable for connecting the battery pack 4 with an external charging source, such as a wall socket, USB source or other source of electrical energy.

The battery pack 4 is preferably configured to be removable from the energy storage system 1 without the use of tools. The battery pack 4 may however comprise a locking mechanism to secure it to the energy storage system 1 when connected, and also to counteract theft of the battery pack 4. Such a locking mechanism may be implemented in many ways, and may require a key to unlock.

We refer now to figure 2 for further description of the battery pack 4. The battery pack 4 comprises a rechargeable energy storage module 42, comprising one or more electrochemical ly chargeable energy storage cells. The energy storage cells may be Lithium-Ion batteries or any other rechargeable electrochemical energy storage cells. The rechargeable energy storage module 42 is connected to a DC/DC converter 43, which converts the voltage of the power from the rechargeable energy storage module 42 to a voltage suitable for use with the electrical load 7. The DC/DC converter 43 also converts the voltage of power received from charging to voltage suitable for charging the rechargeable energy storage module 42. The DC/DC converter may be of any kind suitable for the voltage ranges handled by the energy storage system 1. The DC/DC converter 43 is connected to an inverter 44, which converts direct current to alternating current or vice versa. The inverter 44 is connected to the energy storage system 1 by way of an electrical connection terminal 8. The electrical connection terminal 8 may be formed as an integral unit comprising further electrical equipment, such as measuring equipment for current, voltage or other electrical properties, or electrical equipment for determining the state of charge or state of health of the rechargeable energy storage module 42.

The inverter 44 may also be connected to a first power input and output device 45, configured to receive AC power from a wall socket and provide the inverter 44 with said AC power. The inverter 44 may be

configured to operate within a voltage range suitable for use with a national power grid of the location where the inverter 44 is to be used. Otherwise, the power input and output device 45 may be formed as an integral unit comprising necessary components to transform the voltage of the alternating electrical current from the wall socket to a voltage range where the inverter 44 is configured to operate. The inverter may e.g. be configured to operate with a voltage of 1 10V or 220V.

The inverter 44 is further connected to a second power input and output device 46, configured to receive DC power from a USB connection and provide said DC power to the converter 44.

The inverter 44 is further connected to a third power input and output device 47 configured to receive electrical power from the converter 8. This power may e.g. be generated by regenerative braking, and may be either DC or AC power depending on the regenerative braking system used. In the case of AC power, this may be fed directly to the inverter 44. In the case that the regenerative braking system generates DC power, this may instead be fed directly to the DC/DC converter 43 for charging of the battery.

The second and third rechargeable storage units 2, 3 may be embodied as a battery pack comprising one or more rechargeable battery cells. In such an embodiment the rechargeable storage units 2, 3 are configured to store electrical charge chemically, and to transfer the stored electrical charge to an external electrical circuit, for instance one containing the electric load 7. The energy storage cells may be Lithium-Ion batteries or any other rechargeable electrochemical energy storage cells. It is however possible to implement the portable rechargeable storage units 2, 3 in any way suitable for transfer of energy to an external electrical circuit. The second and third rechargeable storage units 2, 3 may operate at a nominal voltage of 380VDC.

The portable battery 4 may operate at a nominal voltage of 380VDC. This would facilitate the use of the portable battery 4 as direct source of power for driving the motor 7. Alternatively, the portable battery 4 may operate at a lower nominal voltage, such as 1 10V or 220V. This would facilitate the charging of the battery 4 in a mains outlet. In such an instance the battery 4 would primarily be designed to charge the second or third battery 2, 3 and not be used to directly power the motor 7.

In figures 3-7, various scenarios are depicted. In the various scenarios the components involved are depicted in solid lines and the other components are depicted in dashed lines.

Figure 3 discloses the motor 7 of the electrical vehicle powered by a second battery 2 or the second battery 2 being charged by regenerative braking.

Figure 4 discloses the motor 7 of the electrical vehicle powered by a third battery 3 or the third battery 3 being charged by regenerative braking.

Figure 5 discloses the portable battery 4 charging the third battery 3, or vice versa. Of course there is a corresponding set of scenarios where the portable battery 4 charges the second battery 2, or vice versa.

Figure 6 discloses the portable battery being charged via the on-board charger.

Figure 7 discloses the portable battery being charged by regenerative braking or the electrical vehicle being driven by power from the portable battery.

It may be noted that some of the scenarios may occur simultaneously.

The electrical vehicle may e.g. be driven by power from the second battery 2 as indicated in figure 3 while the third battery 3 is charged by the portable battery 4. Of course there may be a corresponding scenario where the electrical vehicle may e.g. be driven by power from the third battery 3 as indicated in figure 4 while the second battery 2 is charged by the portable battery 4. This allows for the electrical vehicle to be driven by one of the batteries 2 or 3 while the other battery 3 or 2 is charged by the portable battery 4.

It is contemplated that there are numerous modifications of the embodiments described herein, which are still within the scope of the invention as defined by the appended claims.

The portable energy storage unit may for instance be a non- rechargeable energy storage unit. Such a non-rechargeable energy storage unit may e.g. be suitable for long term keeping to be used in case of emergency. Such a non-rechargeable energy storage unit may e.g. be smaller and store less energy than the rechargeable energy storage unit described above.