Battery system comprising first and second battery cell units and method for charging and heating said battery system

Abstract

The disclosure relates to a battery system. The battery system comprises a first battery cell unit and a second battery cell unit, each one comprising a respective current regulator arrangement configured to control charging of a respective battery cell unit. The battery system further comprises a control arrangement. The control arrangement is configured to selectively control charging of the first and second battery cell units, by controlling the current regulator arrangement of the first battery cell unit to charge the first battery cell unit, and simultaneously by controlling the current regulator arrangement of the second battery cell unit to heat said second battery cell unit. The heating is performed by a pulsed charging cycle, preferably wherein the pulsed charging cycle is delivered by pulses having a frequency of 1 Hz – 1 MHz, preferably 10 Hz – 100 kHz. The disclosure further relates to a computer program and a computer-readable medium.

Description

[0001] BATTERY SYSTEM AND METHOD FOR CHARGING A BATTERY SYSTEM

[0002] TECHNICAL FIELD

[0003] The present disclosure relates generally to battery systems and methods to charge such battery systems. In a first aspect, the disclosure relates to a battery system comprising a control arrangement configured to simultaneously charge a first battery cell unit and heat, by a pulsed charging cycle, a second battery cell unit. In a second aspect, the disclosure relates to methods for selectively controlling charging of a first battery cell unit and a second battery cell unit in a battery system. In further aspects, the present disclosure relates to a computer program, a computer-readable medium, and an electrified vehicle comprising said battery system or a generator set comprising said battery system.

[0004] BACKGROUND

[0005] In the strive to reduce global emissions, more and more combustion engines are being replaced with battery driven, or partially battery driven, electrical motors in order to produce the required energy. This has led to the development of energy storage devices, for instance battery systems for electrified, or partially electrified, vehicles or mobile generators that can efficiently deliver the required energy when desired.

[0006] Energy storage devices are generally built up from many electrochemical cells, sometimes also referred to as battery cells, to achieve desired capacity. The electrochemical cells can store or release energy through electrochemical reactions. An energy storage device used for powering a vehicle may comprise one or more battery packs. In case the energy storage device comprises a plurality of battery packs, these may be connected in series and / or in parallel. Each battery pack may typically comprise a plurality of battery modules connected in series and / or in parallel. A battery module typically comprises multiple electrochemical cells connected in series and / or parallel, the multiple electrochemical cells being partly or fully encased in a mechanical structure. Other configurations of energy storage devices are also possible, if desired. For example, it is also possible to arrange individual electrochemical cells in a battery pack, without the use of modules.

[0007] The service life of a battery system is an essential factor when considering the total life cost of the system and its environmental impact. For obvious reasons, it is desirable that a battery system has a long service life as possible to diminish the global usage of battery components and avoid replacement of battery systems. Thus, there is a desire to reduce aging of such battery systems so as to prolong the service life thereof. There are many mechanisms that affect aging and thus the service life of a battery system. For example, the service life is affected by how the energy storage device is charged.

[0008] It is known that charging of a battery system in cold temperatures can be challenging for the service life of a batter system. Unfortunately, if current is passed through a battery cell, e.g. charging a cell, at low temperatures undesired electrochemical reactions can occur which decrease the service life. A common solution is to heat the battery system before charging by using an external or internal heating source. However, this can be both time consuming and energy consuming. Another solution has been to limit the amount of current that is used for charging at cold temperatures, thus increasing charging times.

[0009] There remains a need for improved battery systems allowing for faster and more efficient charging. More specifically, there remains a need for improved battery systems allowing for faster and more efficient charging even at cold temperatures without negatively affecting the service life of the battery cells within the battery system.

[0010] SUMMARY

[0011] It is an object of the present invention to overcome, or at least alleviate, at least some of the above-mentioned problems and drawbacks. The object is achieved by the subject-matter of the appended independent claim(s).

[0012] According to a first aspect, the present disclosure relates to a battery system. The battery system comprises a first battery cell unit and a second battery cell unit, wherein the first battery cell unit and the second battery cell unit each comprise a respective current regulator arrangement configured to control charging of a respective battery cell unit. The battery system further comprises a control arrangement. The control arrangement is configured to selectively control charging of the first and second battery cell units, by controlling the current regulator arrangement of the first battery cell unit to charge the first battery cell unit, and simultaneously by controlling the current regulator arrangement of the second battery cell unit to heat said second battery cell unit. The heating is performed by a pulsed charging cycle. Preferably the pulsed charging cycle is delivered by pulses having a frequency of 1 Hz - 1 MHz, even more preferably 10 Hz - 100 kHz.

[0013] It is understood that a battery cell unit according to the present disclosure may be a single battery cell (i.e. electrochemical cell), a group of battery cells arranged in a module, or a battery pack comprising multiple battery modules which may be connected in series and / or in parallel. It is further understood that the first battery cell unit and the second battery cell unit are two different battery cell units. It is further to be understood that a first battery cell unit and a second battery cell unit according to the present disclosure may be battery cells or groups of battery cells of two separate modules, or may be part of the same module. Similarly, it is to be understood that a first battery cell unit and a second battery cell unit according to the present disclosure may be battery cells or groups of battery cells of two separate battery packs, or may be part of the same battery pack

[0014] The control arrangement may be an arrangement configured to control closing of an electric circuit thus letting current pass through a battery cell, or to control opening of an electric circuit thus inhibiting current from passing through the battery cell.

[0015] The control arrangement is configured to control the first battery cell unit’s current regulator arrangement and to control the second battery cell unit’s current regulator arrangement. It is understood that the current regulator arrangements are configured to control how current is passed through a respective battery cell unit, so that a battery cell unit may be charged or heated. By a pulsed charging cycle is meant allowing a pulsed current to pass through the battery cell unit in order to induce Joule heating of the battery cell unit but no, or substantially no, charging of the battery cell unit. Joule heating occurs when a current is passed through a battery cell. Therefore, it is understood that a pulsed charging cycle within the present disclosure may comprise, or consist of, passing a pulsed current through a referred to battery cell unit. The pulsed current may thus be delivered by pulses having a frequency as described in the present disclosure. In other words, the pulsed charging frequency should be sufficiently low so as to enable current to pass through the electric battery cell but not so low so as to induce charging of the battery cell. If current is pulsed in sufficiently short pulses (i.e. at sufficiently high frequencies), the current interval, i.e. time, is below any time at which an electrochemical reaction could occur and hence any charging could occur. This may be done by opening and closing an electric circuit into the second battery cell unit with a frequency according to the present disclosure. Hence, by allowing a pulsed current to pass through a battery cell unit according to the present disclosure, heating of the battery cell unit is achieved with no or substantially no charging of the battery cell. It is to be understood that a pulsed charging cycle is not limited to only pulsed charging, but may also comprise pulsed charging and discharging, e.g. that the pulse alternates between charge and discharge current for the battery cells being subjected to heating. The battery system according to the present disclosure allows to simultaneously charge a first battery cell unit of the battery system while a second battery cell unit of the battery system undergoes a pulsed charging cycle to heat said second battery cell. Such a battery system thus allows for more efficient usage of an electrical power input to the battery system when the battery system is to be charged, as a battery cell unit whose conditions are more favourable to endure efficient charging may be charged while a second battery cell unit is prepared for charging by increasing its temperature. As both processes are simultaneous, a more time efficient charging operation is achieved compared to if heating and charging are performed separately. Moreover, a more efficient energy utilization is achieved as most of the electrical energy input is utilized to charge the battery cell unit which can be charged in an optimized manner from an electrical loss point of view. Moreover, the service life of the battery system is increased as battery cells that are not ready for charging are pre-treated by heating before subjected to charging.

[0016] The battery system according to the present disclosure may be configured for use as a battery system in an electrified vehicle. The electrified vehicle may be any kind of heavy-duty vehicle such as a truck, bus or construction equipment. Further, the battery system according to the present disclosure may be configured for use as a battery system for a generator set. Both the electrified vehicle and the generator set may be fully electrified, or partially electrified (hybrid) solutions.

[0017] The control arrangement may further be configured to, based on obtained data indicative of the resistance of the first battery cell unit and the second battery cell unit respectively, determine which battery cell unit to charge and which battery cell unit to heat, preferably wherein the data indicative of the resistance of the first battery cell unit and the second battery cell unit respectively are any one or a combination of: a temperature of a battery cell unit, a resistance of a battery cell unit, a state of health of a battery cell unit and a state of charge of a battery cell unit.

[0018] Such a control arrangement allows for further charging efficiency improvements and service life improvements of the battery system, as the battery cell unit which is determined to have the least favourable resistance properties is heated, while the battery cell unit determined to have more favourable resistance properties is simultaneously charged.

[0019] The data may be obtained by receiving data from a data collection device such as, but not limited to, sensors arranged on each one of the first battery cell unit and the second battery cell unit configured to obtain a desired parameter, or may be calculated based on data available to the control arrangement in regard to current data and voltage data of the battery system, which may be measured or tabulated.

[0020] The control arrangement may further be configured to first heat the battery cell unit having the lowest temperature and / or the highest resistance before heating another battery cell unit of the battery system.

[0021] Due to the relationship between voltage, current, and resistance, a higher resistance results in a larger voltage drop, which means the battery may reach its voltage limits, and there is less available energy for the receiving device. A higher internal resistance also generates more heat. Hence, the battery system according to the present disclosure utilizes a normally disadvantageous property of a battery cell unit (i.e. high resistance) to achieve efficient heating and prepare the battery cell unit for charging, while another battery cell unit is simultaneously charged.

[0022] The battery system may further be configured to receive electrical power for the charging and / or the heating from an external electrical source and / or from a third battery cell unit of the battery system.

[0023] Such a battery system allows for more efficient usage of received electrical power for the charging and / or the heating as explained above. Moreover, if the received electrical power originates from a third battery cell unit of the battery system, the battery system according to the present disclosure may allow to prepare the battery cell units of the battery system for a subsequent charging with an external power source, such as a charging station. This decreases charging time as the battery cell units of the battery system may exhibit temperature or resistance parameters suitable for charging once an external power source is connected.

[0024] The battery system may be configured to receive the electrical power for the heating of the second battery cell from the first battery cell undergoing charging.

[0025] The current regulator arrangement may be any one or a combination of a mechanical switch or an electronic switch. An electronic switch may be a semiconductor type of switch.

[0026] The battery system may further comprise an electric power converter configured to control a current and / or a voltage to a first battery cell unit and / or a second battery cell unit. Preferably, said electric power converter is a DC-DC converter. Preferably the system comprises a plurality of DC-DC converters each configured to control a current and / or a voltage to a respective battery cell unit or battery cell units. In such a battery system, the DC-DC converters allow to control the current to a first and second battery cell unit, preferably a first battery pack and a second battery pack. This further improves the charging efficiency of the battery system according to the present invention, as an optimized current amount can be sent to the first and second battery cell unit depending on if is to be charged or heated by a pulsed charging cycle.

[0027] According to a second aspect, the present disclosure relates to a method for selectively controlling charging of a first battery cell unit and a second battery cell unit in a battery system. The first battery cell unit and the second battery cell unit each comprise a respective current regulator arrangement. The method comprises: controlling, by a control arrangement, the current regulator arrangements to simultaneously charge the first battery cell unit and heat the second battery cell unit by a pulsed charging cycle, preferably wherein the pulsed charging cycle is delivered by pulses having a frequency of 1 Hz - 1 MHz, preferably 10 Hz - 100 kHz.

[0028] Similarly as to the first aspect of the present disclosure, a method according to the second aspect allows to simultaneously charge a first battery cell unit of a battery system while a second battery cell unit of the battery system undergoes a pulsed charging cycle to heat said second battery cell. Such a method thus allows for more efficient usage of an electrical power input to the battery system when the battery system is to be charged, as a battery cell unit whose conditions are more favourable to endure efficient charging is charged while a second battery cell unit is prepared for charging by increasing its temperature. As both processes are simultaneous, a more time efficient charging operation is achieved compared to if heating and charging are performed separately, as well as more efficient energy utilization. Moreover, the service life of the battery system is increased as battery cells that are not ready for charging are pre-treated by heating before subjected to charging.

[0029] It is understood that any one of the effects described for the battery system of the first aspect, are also applicable to the method for selectively controlling charging of a first battery cell unit and a second battery cell unit according to the second aspect.

[0030] Controlling the charging of a first battery cell unit and a second battery cell unit may comprise: generating, by the control arrangement, a first control signal configured to control the current regulator arrangement of the first battery cell unit to charge the first battery cell unit, generating, by the control arrangement, a second control signal configured to control the current regulator arrangement of the second battery cell unit to heat the second battery cell unit by a pulsed charging cycle, and controlling the current regulator arrangement of the first battery cell unit and the current regulator arrangement of the second battery cell unit in response to the first and second control signal respectively.

[0031] Controlling the current regulator arrangement of the first battery cell unit to charge the first battery cell unit may be done by allowing a continuous and / or a discontinuous current to pass through the first battery cell unit, in order to induce electrochemical reactions and hence charging of the battery cell unit.

[0032] Controlling the current regulator arrangement of the second battery cell unit to heat the second battery cell unit by a pulsed charging cycle may be done by allowing a pulsed current to pass through the battery cell in order to induce Joule heating of the battery cell unit but no, or substantially no, charging of the battery cell unit. This may be done by the pulsed charging frequency being sufficiently low so to enable current to pass through the electric battery cell but not so low to induce charging of the battery cell.

[0033] It is to be understood that a pulsed charging cycle is not limited to only pulsed charging, but may also comprise pulsed charging and discharging, e.g. that the pulse alternates between charge and discharge current for the battery cells being subjected to heating.

[0034] The method may further comprise, determining, by the control arrangement, which battery cell unit to charge and which battery cell unit to heat based on data indicative of the resistance of the first battery cell unit and the second battery cell unit, preferably wherein determining which battery cells unit to charge and which battery cell unit to heat comprises determining which battery cells unit has the lowest temperature and / or highest resistance value.

[0035] Such a method allows for further charging efficiency improvements and service life improvements of the battery system, as the battery cell unit which is determined to have the least favourable resistance properties for charging is heated, while the battery cell unit determined to have more favourable resistance properties is simultaneously charged.

[0036] Similarly as previously described for the battery system according to the first aspect of the present disclosure, the method according to the present disclosure utilizes a normally disadvantageous property of a battery cell unit (i.e. high resistance) to achieve efficient heating and prepare the battery cell unit for charging, while another battery cell unit is simultaneously charged.

[0037] The step of determining, by the control arrangement, which battery cell unit to charge and which battery cell unit to heat may comprise: obtaining, in the control arrangement, a first data D1 indicative of the resistance of the first battery cell unit; obtaining, in the control arrangement, a second data D2 indicative of the resistance of the second battery cell unit; comparing, by the control arrangement, the obtained first and second data D1 , D2 indicative of the resistance of the respective battery cell unit, to a preset threshold data value T1.

[0038] The data may be obtained by receiving data from a data collection device such as, but not limited to, sensors arranged on each one of the first battery cell unit and the second battery cell unit configured to obtain a desired parameter, or may be calculated based on data available to the control arrangement in regard to current data and voltage data of the battery system, which may be measured or tabulated.

[0039] The threshold data value T1 is a data value set which determines the comparative value if a battery cell unit can be charged or if it needs to be heated. The threshold data value may be indicative of a resistance of a battery cell unit, and may be any one of or a combination of: a temperature value, a resistance value, a state of health value and a state of charge value.

[0040] Controlling the charging of a first battery cell unit and a second battery cell unit may further comprise ceasing the heating when the second battery cell unit has reached a predefined temperature or resistance, or is performed for a predefined period of time.

[0041] This allows to heat a battery cell unit until a temperature or resistance which allows for efficient and safe subsequent charging.

[0042] The method may further comprise receiving the electrical power for the charging and / or heating from an external electrical source, from a third battery cell unit of the battery system or a combination of both.

[0043] Such a method allows for more efficient usage of received electrical power for the charging and the heating as explained above. Moreover, if the received electrical power originates from a third battery cell unit of the battery system, the method according to the present disclosure allows to prepare the battery cell units of the battery system for a subsequent charging with an external power source, such as a charging station. This decreases charging time as the battery cell units of the battery system may exhibit temperature or resistance parameters suitable for charging once an external power source is connected.

[0044] In a third aspect, the present disclosure relates to a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the method according to any one of the second aspect.

[0045] The computer program provides the same advantages as described above with reference to the second aspect of the present disclosure with reference to a method for selectively controlling charging of a first battery cell unit and a second battery cell unit in a battery system.

[0046] In a fourth aspect, the present disclosure relates to a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method according to any one the second aspect.

[0047] In a fifth aspect, the present disclosure relates to an electrified vehicle or a generator set comprising a battery system according to any one of the first aspect.

[0048] The electrified vehicle or a generator set provides the same advantages as described above with reference to the first aspect of the present disclosure with reference to a battery system.

[0049] BRIEF DESCRIPTION OF THE FIGURES

[0050] Further objects and advantages of, and features of the disclosure will be apparent from the following description of one or more embodiments, with reference to the appended figures, where:

[0051] Fig. 1 schematically illustrates an example of a battery system according to the present disclosure;

[0052] Fig. 2 represents a flowchart schematically illustrating a first exemplifying embodiment of the method for selectively controlling charging of a first battery cell unit and a second battery cell unit in a battery system; Fig. 3 represents a flowchart schematically illustrating a second exemplifying embodiment of the method for selectively controlling charging of a first battery cell unit and a second battery cell unit in a battery system;

[0053] DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0054] The invention will be described in more detail below with reference to exemplifying embodiments and the accompanying figures. The invention is however not limited to the exemplifying embodiments discussed and / or shown in the figures, but may be varied within the scope of the appended claims. Furthermore, the figures shall not be considered drawn to scale as some features may be exaggerated in order to more clearly illustrate the invention or features thereof.

[0055] The terminology used herein is for the purpose of describing particular aspects of the disclosure only and is not intended to limit the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0056] In accordance with the present disclosure, a battery system is provided. The battery system is configured for use as a battery system in an electrified vehicle or in a generator set. Both the electrified vehicle and the generator set may be fully electrified, or partially electrified (hybrid) solutions.

[0057] Fig. 1 exemplifies one example of a battery system 1 according to the present disclosure. The battery system 1 comprises a first battery cell unit 2 and a second battery cell unit 3. In Fig. 1 , two battery cell units are shown. It should however be recognized that the battery system 1 may consist of more than two battery cell units. The battery cell units may be connected in series or in parallel to each other.

[0058] Each battery cell unit 2, 3 may be a single battery cell (i.e. electrochemical cell), a group of battery cells arranged in a module, or a battery pack comprising multiple battery modules which may be connected in series and / or in parallel. It is further to be understood that a first battery cell unit and a second battery cell unit according to the present disclosure may be battery cells or groups of battery cells of two separate modules, or may be part of the same module. Similarly, it is to be understood that a first battery cell unit and a second battery cell unit according to the present disclosure may be battery cells or groups of battery cells of two separate battery packs, or may be part of the same battery pack It is further understood that the first battery cell unit and the second battery cell unit are two different battery cells units. A battery cell may for example be lithium-ion battery cells or sodium-ion battery cells, but are not limited thereto.

[0059] The first battery cell unit 2 comprises a current regulator arrangement 4. Similarly, also the second battery cell unit 3 comprises a current regulator arrangement 5. The current regulator arrangements 3, 4 are configured to control the charging of a respective battery cell unit. The current regulator arrangements 3, 4 may be any one or a combination of a mechanical switch or an electronic switch. An electronic switch may be a semiconductor type of switch. The current regulator arrangements 3, 4 are configured to control charging of the battery cell units 2, 3 by allowing a current to pass through the battery cell units 2, 3 in order to induce electrochemical reactions. This may be done by closing an electric circuit formed by the battery cell units 2, 3 and thereby allowing a continuous and / or a discontinuous current to pass through the first battery cell unit, in order to induce electrochemical reactions and hence charging of the battery cell unit.

[0060] The system 1 further comprises a control arrangement 6. The control arrangement 6 is configured to selectively control charging of the first battery cell unit 2 and simultaneously control heating of the second battery cell unit 3.

[0061] The control arrangement 6 may be a part of the battery system 1 as such, as illustrated in Fig. 1. For example, the control arrangement 6 may be incorporated in the battery system 1. Alternatively, the control arrangement 6 may be any other control arrangement 6 of an electrified vehicle or a generator set. Parts of the control arrangement 6 may also be arranged remote from the vehicle or generator set, if desired. For example, parts of the control arrangement 6 may be arranged at a charging station or at a remotecontrol centre. The control arrangement 6 may comprise one or more control units. In case of the control arrangement 6 comprising a plurality of control units, each control unit may be configured to control a certain function or a certain function may be divided between more than one control units. The control arrangement 6 comprises control circuitry to perform the method according to any one of the steps, examples or embodiments as described in the present disclosure. The control arrangement 6 may include one or more Electronic Control Units (ECUs).

[0062] When the control arrangement 6 controls the current regulator arrangement 4 of the first battery cell unit 2 to charge said first battery cell unit, it may send a first control signal to the current regulator arrangement 4 so to allow charging of the first battery cell unit 2. The first control signal may be a control signal to the current regulator arrangement 4 closing an electric circuit into the first battery cell unit 2. When the control arrangement controls heating of the second battery cell unit 3, it may send a second control signal to the current regulator arrangement 5 to send pulsed charging cycles into the second battery cell unit according to the present disclosure. Such a control signal may be a control signal controlling the current regulator arrangement to close and open an electric circuit into the second battery cell unit 3 with a frequency according to the present disclosure.

[0063] The battery system may further comprise an electric power converter 7. The electric power converter 7 is configured to control a current and / or a voltage to the first battery cell 2 and / or the second battery cell 3. In the embodiment illustrated in Fig. 1 , one electric power converter 7 is provided in the battery system 1 , controlling a current and / or a voltage to both the first battery cell unit 2 and the second battery cell unit 3. However, in another embodiment of the present disclosure not illustrated in Fig. 1 , the battery system may comprise a respective electric power converter 7 for each one of the first battery cell unit 2 and second battery cell unit 3. This allows to control the amount of current and / or voltage to each one of the of first battery cell unit 2 and second battery cell unit 3 individually, and hence improve energy input utilization so that current and / or voltage is applied to parts of the battery system 1 that are most suitable to receive such current and / or voltage.

[0064] The herein described methods may be used for selectively controlling charging and heating of the first battery cell unit 2 and the second battery cell unit 3 in the battery system 1 shown in figure 1.

[0065] Figure 2 represent a flowchart schematically illustrating a first exemplifying embodiment of the method for controlling charging of a first battery cell unit 2 and a second battery cell unit 3 in a battery system 1 according to the present disclosure.

[0066] The method comprises a method step S100 of controlling the current regulator arrangements 4, 5 to simultaneously charge the first battery cell unit 2 and heat the second battery cell unit 3 by a pulsed charging cycle. Said method step S100 is performed by the control arrangement 6 as previously disclosed. More details in how step S100 is performed are provided below.

[0067] In more detail, the method step S100 of controlling the current regulator arrangements 4, 5 to simultaneously charge the first battery cell unit 2 and heat the second battery cell unit 3 by a pulsed charging cycle may comprise the method steps S101 , S102, S103 and S105. Method step S101 is a step of generating a first control signal configured to control the current regulator arrangement 4 of the first battery cell unit 2 to charge the first battery cell unit 2. The first control signal is generated by the control arrangement 6. As previously described, the first control signal may control the current regulator arrangement 3 of the first battery cell unit 2 so to allow current to pass through the first battery cell unit 2 in order to induce charging.

[0068] After step S101 , the method proceeds to a step S102 of generating a second control signal configured to control the current regulator arrangement 5 of the second battery cell unit 3 to heat the second battery cell unit 3 by a pulsed charging cycle. The second control signal is generated by the control arrangement 6. As previously described, the second control signal may control the current regulator arrangement 5 of the second battery cell unit 3 so to allow a pulsed charging cycle to pass through the second battery cell unit 3 in order to induce heating, but not charging of said second battery cell unit.

[0069] After step S102, the method proceeds to a step S103 of controlling the current regulator arrangement 4 of the first battery cell unit 2 and the current regulator arrangement 5 of the second battery cell unit 3 in response to the first and second control signal respectively. The first control signal may be a control signal provided to the current regulator arrangement 4 of the first battery cell unit 2 to close an electric circuit into the first battery cell unit 2 so to allow current to pass through and induce charging of the battery cell unit 2. The second control signal may be a control signal provided to the current regulator arrangement 5 of the second battery cell unit 3 so to deliver a pulsed charging cycle to the second battery cell unit 3. The pulsed charging cycle may be delivered by the current regulator arrangement 5 by opening and closing an electric circuit into the second battery cell unit 3 with a frequency of 1 Hz - 1 MHz, preferably 10 Hz - 100 kHz. The pulsed charging frequency should be sufficiently low so to enable current to pass through the electric battery cell but not so low to induce charging of the battery cell.

[0070] It is to be understood that method steps S101 and S102 may be performed in that order, may be performed simultaneously, or may be performed in the reversed order.

[0071] It is understood that any one of the methods of controlling charging of a first battery cell unit 2 and a second battery cell unit 3 in a battery system according to the present disclosure may further comprise a step S105 of ceasing the heating of the second battery cell unit 3 when the second battery cell unit 3 has reached a predefined temperature, or is performed for a predefined period of time. It is to be understood that the second battery cell unit 3 may be subjected to charging after a heating process according to the present disclosure.

[0072] It is understood that any one of the methods of controlling charging of a first battery cell unit 2 and a second battery cell unit 3 in a battery system according to the present disclosure may further comprise a step of receiving electrical power for the charging and / or heating from an external electrical source. The electrical power for the charging and / or heating may also be received from a third electric battery cell present in the battery system.

[0073] Figure 3 represent a flowchart schematically illustrating a second exemplifying embodiment of the method for controlling charging of a first battery cell unit 2 and a second battery cell unit 3 in a battery system 1 according to the present disclosure. Similarly as to the exemplified embodiment of Fig. 2, also the exemplified method illustrated in Fig. 3 comprises steps S101 , S102, S103 and S105.

[0074] The method illustrated in Fig. 3 further comprises a step of determining S104 which battery cell unit to charge and which battery cell unit to heat based on data indicative of the resistance of the first battery cell unit 2 and the second battery cell unit 3. The determination is performed by the control arrangement 6. This allows to heat the battery cell unit which has the least favourable resistance properties, and charge the battery cell unit which is deemed to have the more favourable resistance properties among the first and second battery cell units.

[0075] In an alternative embodiment of the second exemplifying embodiment illustrated in Fig. 3, the step of determining S104 which battery cell unit to charge and which battery cell unit to heat may further comprise steps S1041 , S1042 and S1043.

[0076] Step S1041 is a step of obtaining a first data D1 indicative of the resistance of the first battery cell unit 2. The step is performed in the control arrangement 6. The first data D1 indicative of the resistance of the first battery cell unit 2 may be any one of a temperature of a battery cell unit, a resistance of a battery cell unit, a state of health of a battery cell unit and a state of charge of a battery cell unit.

[0077] After step S1041 , the method proceeds to a step S1402 of obtaining a second data D2 indicative of the resistance of the second battery cell unit 3. The second data D2 indicative of the resistance of the second battery cell unit 3 may be any one of a temperature of a battery cell unit, a resistance of a battery cell unit, a state of health of a battery cell unit and a state of charge of a battery cell unit. It is to be understood that method steps S1401 and S1402 may be performed in that order, may be performed simultaneously, or may be performed in the reversed order.

[0078] The alternative embodiment of the second exemplifying embodiment illustrated in Fig. 3 further comprises a step S1403 of comparing, the first and second data D1 , D2 indicative of the resistance of the respective battery cell unit, to a preset threshold data value T 1. Thereby, based on the obtained data indicative of the resistance of the first battery cell unit 2 and the second battery cell unit 3 respectively, the control arrangement 6 may determine which battery cell unit to charge and which battery cell unit to heat. The determination may be done by comparing D1 and D2 and analyse which one of D1 and D2 is closest or most far away from the preset threshold data value T1 depending on the analysed parameter of interest. For instance, the control arrangement may determine to first heat the battery cell unit having the lowest temperature and / or the highest resistance before heating another battery cell unit of the battery system.

[0079] It is understood that instructions for selectively controlling charging of a first battery cell unit and a second battery cell unit in a battery system according to the present disclosure may be provided in a computer program. Such a computer program may be stored in a computer-readable medium (e.g., a memory or a compact disc) that comprises instructions which, when executed by a computer, cause the computer to carry out the method. The computer may be comprised in the control arrangement 6 according to the present invention. In some embodiments, the computer-readable medium may be a non- transitory computer- readable medium, such as a tangible electronic, magnetic, optical, infrared, electromagnetic, and / or semiconductor system, apparatus, and / or device.

[0080] The computer program is usually part of a computer program product which comprises a suitable digital storage medium on which the computer program is stored, such as the computer-readable medium mentioned above. In other words, the computer program product may be a computer readable medium and the computer program may be stored in the computer readable medium.

[0081] In more detail, the control arrangement 6 may comprise one, or more, computer(s). The computer comprises any hardware or hardware / firmware device implemented using processing circuity such as, but not limited to, a processor, Central Processing Unit (CPU), a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a System-on-Chip (SoC), a programmable logic unit, a microprocessor, an application-specific integrated circuit, or any other device capable of electronically performing operations in a defined manner.

Claims

CLAIMS1. A battery system (1), wherein said battery system (1) comprises; a first battery cell unit (2) and a second battery cell unit (3), wherein the first battery cell unit (2) and the second battery cell unit (3) each comprise a respective current regulator arrangement (4, 5) configured to control charging of a respective battery cell unit (2, 3), a control arrangement (6), wherein said control arrangement (6) is configured to selectively control charging of the first and second battery cell units (2, 3), by controlling the current regulator arrangement (4) of the first battery cell unit (2) to charge the first battery cell unit (2), and simultaneously by controlling the current regulator arrangement (5) of the second battery cell unit (3) to heat said second battery cell unit (3), wherein said heating is performed by a pulsed charging cycle, preferably wherein the pulsed charging cycle is delivered by pulses having a frequency of 1 Hz - 1 MHz, preferably 10 Hz - 100 kHz.

2. The battery system (1) according to the preceding claim, wherein the control arrangement (6) is further configured to, based on obtained data indicative of the resistance of the first battery cell unit (2) and the second battery cell unit (3) respectively, determine which battery cell unit (2, 3) to charge and which battery cell unit (2, 3) to heat, preferably wherein the data indicative of the resistance of the first battery cell unit (2) and the second battery cell unit (3) respectively are any one or a combination of: a temperature of a battery cell unit, a resistance of a battery cell unit, a state of health of a battery cell unit and a state of charge of a battery cell unit.

3. The battery system (1) according to any of the preceding claims, wherein the control arrangement (6) is configured to first heat the battery cell unit having the lowest temperature and / or the highest resistance before heating another battery cell unit of the battery system.

4. The battery system (1) according to any one of the preceding claims, wherein said battery system (1) is configured to receive electrical power for the charging and / or the heating from an external electrical source and / or from a third battery cell unit of the battery system (1).

5. The battery system (1) according to any one of the preceding claims, wherein the current regulator arrangement (6) may be any one or a combination of a mechanical switch or an electronic switch.

6. The battery system (1) according to any one of the preceding claims, where said battery system (1) further comprises at least one electric power converter (7), preferably a DC-DC converter, configured to control a current and / or a voltage to the first battery cell unit (2) and / or the second battery cell unit (3), preferably the batterysystem (1) comprises a plurality of DC-DC converters each configured to control a current and / or a voltage to a respective battery cell unit (2, 3).

7. A method for selectively controlling charging of a first battery cell unit (2) and a second battery cell unit (3) in a battery system (1), wherein the first battery cell unit (2) and the second battery cell unit (3) each comprise a respective current regulator arrangement (4, 5), wherein the method comprises: controlling (S100), by a control arrangement (6), the current regulator arrangements (4, 5) to simultaneously charge the first battery cell unit (2) and heat the second battery cell unit (3) by a pulsed charging cycle, preferably wherein the pulsed charging cycle is delivered by pulses having a frequency of 1 Hz - 1 MHz, preferably 10 Hz - 100 kHz.

8. The method of claim 7, wherein controlling the charging of a first battery cell unit (2) and a second battery cell unit (3) comprises: generating (S101), by the control arrangement (6), a first control signal configured to control the current regulator arrangement (4) of the first battery cell unit (2) to charge the first battery cell unit (2), generating (S102), by the control arrangement (6), a second control signal configured to control the current regulator arrangement (5) of the second battery cell unit (3) to heat the second battery cell unit (3) by a pulsed charging cycle, and controlling (S103) the current regulator arrangement (4) of the first battery cell unit (2) and the current regulator arrangement (5) of the second battery cell unit (3) in response to the first and second control signal respectively.

9. The method according to any one of claims 7 - 8, further comprising, determining (S104), by the control arrangement (6), which battery cell unit (2, 3) to charge and which battery cell unit (2, 3) to heat based on data indicative of the resistance of the first battery cell unit (2) and the second battery cell unit (3), preferably wherein determining which battery cells unit (2, 3) to charge and which battery cell unit (2, 3) to heat comprises determining which battery cells unit (2, 3) has the lowest temperature and / or highest resistance value10. The method according to claim 9, wherein the step of determining (S104) comprises: obtaining (S1041), in the control arrangement (6), a first data D1 indicative of the resistance of the first battery cell unit (2); obtaining (S1042), in the control arrangement (6), a second data D2 indicative of the resistance of the second battery cell unit (3); comparing, by the control arrangement 86), the first and second data D1 , D2 indicative of the resistance of the respective battery cell unit (2, 3), to a preset threshold data value T 1.

11. The method according to any one claims 7 - 10, wherein controlling the charging of a first battery cell unit (2) and a second battery cell unit (3) further comprises ceasing (S105) the heating when the second battery cell unit (3) has reached a predefined temperature, or is performed for a predefined period of time.

12. The method according to any one of claims 7 - 11, further comprising receiving (S106) the electrical power for the charging and / or heating from an external electrical source, from a third battery cell unit of the battery system or a combination of both.

13. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the method according to any one of claims 7 - 1214. A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method according to any one of claims 7 - 12.

15. An electrified vehicle or a generator set comprising a battery system (1) according to any one of claims 1 - 6.

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