ACTIVATION CONTROL OF PARALLEL CONNECTED BATTERY PACKS

A computer system controls activation of a plurality of battery packs in parallel connection. The computer system has processing circuitry to activate a first battery pack from among the plurality of battery packs; determine a compensation current which is adapted to counteract at least parts of a charge equalization current expected to be generated by a subsequent activation of an additional battery pack from among the plurality of battery packs; apply the compensation current to currently activated battery pack(s); and activate the additional battery pack.

TECHNICAL FIELD

The disclosure relates generally to energy storage systems. In particular aspects, the disclosure relates to activation control of parallel connected battery packs. The disclosure can be applied to heavy-duty vehicles, such as trucks, buses, and construction equipment, among other vehicle types. The disclosure can also be applied to other areas of application, such as marine vessels, industrial applications, stationary applications, among other areas of application. Although the disclosure may be described with respect to a particular vehicle, the disclosure is not restricted to any particular vehicle.

BACKGROUND

In a battery arrangement comprising a plurality of battery packs connected in parallel, there is an issue of unintended charge equalization currents flowing between these packs. This is especially the case under certain conditions, such as in cold temperatures and high state of charge scenarios, where there can be an increased battery internal resistance and a reduced ion mobility. Battery charge power capabilities are therefore limited, especially in these conditions. Unwanted charges circulating between battery packs might lead to violation of power limits, ultimately leading to lithium plating and battery degradation.

It is in view of the above observations and others the present inventors herein are suggesting one or more improvements to the prior art of battery pack activation control.

SUMMARY

Charge equalization currents typically occur when batteries are connected together but no load is applied. Once the load is applied, batteries deliver uneven currents until they are balanced. However, in the latter case the charges move in same direction, i.e., from batteries to the load. In cold temperatures or high state of charge scenarios, charging capabilities are limited. Even minor variations in open-circuit voltage or internal resistance between battery packs can lead to the problems mentioned in the background section above. One existing solution to address this problem involves using only a single battery pack, but this approach has obvious drawbacks as it introduces an imbalance in the system and limits power capabilities. Another existing solution involves setting a maximum current threshold, thereby allowing the connection of multiple battery packs only when the current remains within acceptable limits. However, setting a maximum current threshold to allow the connection of multiple battery packs can limit power, reduce battery utilization, introduce complexity, create balancing challenges, and potentially compromise safety. In some cases it may even lead to a situation where the battery packs cannot be connected to one another due to a failure to fulfil the established maximum current threshold. The prior art therefore fails to suggest a satisfactory solution for managing charge equalization currents.

The present disclosure therefore aims to overcome the problem of unintended charge equalization currents flowing between battery packs by introducing a computer-controlled approach of controlling the activation of the battery packs.

According to a first aspect of the disclosure there is provided a computer system for controlling activation of a plurality of battery packs in parallel connection. The computer system comprises processing circuitry configured to activate a first battery pack from among the plurality of battery packs; determine a compensation current which is adapted to counteract at least parts of a charge equalization current expected to be generated by a subsequent activation of an additional battery pack from among the plurality of battery packs; apply the compensation current to currently activated battery pack(s); and activate the additional battery pack.

The first aspect of the disclosure may seek to eliminate or at least mitigate unintended charge equalization currents between the battery packs. By determining and applying a compensation current prior to activating additional packs, the system controls and limits unwanted charges, thus improving the availability of energy within storage systems. This improved energy management may enhance both the charging and discharging capabilities of the system and may prevent lithium plating, thereby contributing to the longevity and reliability of the batteries. Such precise control may be especially advantageous in conditions like low temperatures or high charge states, where charge equalization currents can be particularly problematic due to e.g. increased battery internal resistance and reduced ion mobility.

Optionally in some examples, including in at least one preferred example, the processing circuitry is configured to, sequentially for each additional battery pack to be activated, perform the determination of the compensation current, the application of the compensation current, and the activation of the additional battery pack. A technical benefit may include the assurance of tailored management for each battery pack, enhancing the precision of charge balancing and increasing the overall efficiency of the energy storage system.

Optionally in some examples, including in at least one preferred example, the processing circuitry is configured to obtain response signal data from a battery circuit to which the plurality of battery packs are connected after the compensation current has been applied, and activate the additional battery pack based on a value of the response signal data. A technical benefit may include the ability to make informed decisions on activating additional packs based on real-time feedback, leading to better system stability and battery performance.

Optionally in some examples, including in at least one preferred example, the processing circuitry is configured to determine the compensation current by a static estimation involving setting a predetermined voltage value based on empirical data of previous compensation current determinations in battery packs, wherein the empirical data is one or more of performance data, health data, environmental data, aging data, activation data, and auxiliary data. A technical benefit may include utilizing historical data to streamline the estimation process for compensation currents, making the system more responsive and adaptive to known battery behaviors.

Optionally in some examples, including in at least one preferred example, the processing circuitry is configured to provide the empirical data as training data to a machine learning model, the machine learning model being configured to map the empirical data to a prediction of the compensation current. A technical benefit may include the improvement of compensation current predictions through machine learning, resulting in a system that becomes more accurate and reliable over time.

Optionally in some examples, including in at least one preferred example, the processing circuitry is configured to determine the compensation current in a compensation current range comprising a first limit value being a maximum discharge ability of the battery pack to be activated, and a second limit value being a minimum charge ability of the battery pack to be activated. A technical benefit may include the optimization of compensation current within operational limits of the battery packs, ensuring safe operation without compromising on available power capacity.

Optionally in some examples, including in at least one preferred example, the processing circuitry is configured to determine the compensation current based on a maximum allowed system limit, the maximum allowed system limit being determined by properties of one or more controllable loads in a battery circuit to which the plurality of battery packs are connected. A technical benefit may include the alignment of compensation currents with the maximum system limits, ensuring that the system operates safely within the capabilities of the connected loads.

Optionally in some examples, including in at least one preferred example, the processing circuitry is configured to apply the compensation current by controlling a controllable load of a battery circuit to which the plurality of the battery pack are connected. A technical benefit may include the precise control of additional loads to apply the compensation current, contributing to the fine-tuning of power distribution and protection of battery health.

Optionally in some examples, including in at least one preferred example, the processing circuitry is configured to repeatedly determine the compensation current, apply the compensation current, and activate the additional battery pack, until a time-out condition is met. A technical benefit may include the dynamic management of battery pack activation, which can adapt to changing conditions and help maintain optimal system performance until operational limits determined by the time-out condition are reached.

Optionally in some examples, including in at least one preferred example, the time-out condition is met: once the plurality of battery packs are activated, or once a battery circuit to which the plurality of battery packs are connected has reached a maximum feasible current throughput. A technical benefit may include the efficient utilization of the system's current throughput capabilities, ensuring that all battery packs are activated without overloading the system.

Optionally in some examples, including in at least one preferred example, wherein in response to the battery circuit reaches the maximum feasible current throughput, the processing circuitry is configured to introduce a delay timer during which no further battery packs are activated, obtain battery data from a battery management system, and in response to the battery data indicating an increase in the maximum feasible current throughput, cancel the delay timer and cause a continued operation of repeatedly determining the compensation current, applying the compensation current, and activating additional battery packs. A technical benefit may include the system's ability to pause and resume operations based on current throughput capacity, ensuring that additional packs are activated only when it is safe and feasible to do so.

According to a second aspect of the disclosure there is provided a vehicle comprising the computer system of the first aspect.

According to a third aspect of the disclosure there is provided a computer-implemented method for controlling activation of a plurality of battery packs in parallel connection. The method comprises activating a first battery pack from among the plurality of battery packs; determining a compensation current which is adapted to counteract at least parts of a charge equalization current expected to be generated by a subsequent activation of an additional battery pack from among the plurality of battery packs; applying the compensation current to currently activated battery pack(s); and activating the additional battery pack.

According to a fourth aspect of the disclosure there is provided a computer program product comprising program code for performing, when executed by the processing circuitry, the method of the third aspect.

According to a fifth aspect of the disclosure there is provided a non-transitory computer-readable storage medium comprising instructions, which when executed by the processing circuitry, cause the processing circuitry to perform the method of the third aspect. The fifth aspect of the disclosure may seek to enable new and/or legacy HV components or energy storage systems to be conveniently configured, by software installation/update, for controlling activation of a plurality of battery packs in parallel connection.

The second, third, fourth and fifth aspects of the disclosure may seek to eliminate or at least mitigate unintended charge equalization currents between the battery packs. By determining and applying a compensation current prior to activating additional packs, the system controls and limits unwanted charges, thus improving the availability of energy within storage systems. This improved energy management may enhance both the charging and discharging capabilities of the system and may prevent lithium plating, thereby contributing to the longevity and reliability of the batteries. Such precise control may be especially advantageous in conditions like low temperatures or high charge states, where charge equalization currents can be particularly problematic due to e.g. increased battery internal resistance and reduced ion mobility.

There are also disclosed herein computer systems, control units, code modules, computer-implemented methods, computer readable media, and computer program products associated with the above discussed technical benefits.

DETAILED DESCRIPTION

The subject matter of the present disclosure addresses the issues mentioned in the background section by way of controlling activation of a plurality of battery packs connected in parallel. The solution involves a computer-controlled approach that controls in what way the plurality of battery packs should be connected to one another. A first battery pack is activated, followed by a determination of a compensation current adapted to counteract at least parts of a charge equalization current expected to be generated by a subsequent activation of an additional battery pack. The determined compensation current is then applied to currently activated battery pack(s) (which is the first battery, or the first and any additional battery pack(s) that are currently activated), before the additional battery pack is activated. This computer-controlled approach effectively eliminates, or at least mitigates, the unintended charge equalization currents flowing between the respective battery packs. Accordingly, the unwanted charges circulating between the battery packs are therefore controlled to be limited, which may improve the availability of energy in energy storage systems, thereby enhancing both charge and discharge capabilities. Moreover, the approach may assist in avoiding lithium plating and safeguard against battery degradation during charging processes. This strategic control may be particularly beneficial in challenging scenarios where charge equalization currents tend to be a greater issue, such as in cold weather conditions or situations with a high battery state of charge.

FIG. 1 is an exemplary schematic illustration of a vehicle 10. The vehicle 10 is illustrated as a heavy-duty vehicle, in this case a truck. The vehicle 10 is preferably an electric vehicle. In other areas of application other machines typically employing battery systems can be envisaged, such as for buses, marine vessels, construction equipment, personal vehicles, among other areas of application. The vehicle 10 comprises a tractor unit 12 which is arranged to tow a trailer unit 14. While not explicitly shown, the vehicle 10 includes vehicle units and associated functionality as would be understood and expected by a skilled person, such as a powertrain, chassis, and various control systems.

The vehicle 10 comprises an energy storage system, ESS 50. The ESS 50 is arranged to store electrical energy and release it as needed. The ESS 50 comprises a high-voltage, HV, component 40. The HV component 40 is a relative term, and what is considered high voltage may depend on the context. In applicable power systems discussed herein, high voltage typically refers to voltages higher than the standard residential or commercial power distribution levels. Purely by way of example, voltage levels for HV components in traction batteries or fuel cell systems typically range between 200 V and 800 V or more, in DC fast chargers between 600 V and 1000 V, in HEV (Hybrid Electric Vehicles) between 200 and 300 V. The skilled person will appreciate that the voltage level for the HV component 40 is readily adaptable for other HV application areas.

The HV component 40 comprises a plurality of battery packs 20, each battery pack 20 having a set of battery cells 21 responsible for storing energy in chemical form. When chemical reactions occur electrical energy is harnessed for various application. The battery cell 21 is the fundamental building block of a battery, comprising an anode, cathode, and electrolyte. Multiple battery cells 21 are combined to create a battery pack 21, a modular unit that delivers voltage, capacity, and power for diverse applications. The battery packs 20 may include lithium-ion batteries, lithium iron phosphate batteries, solid-state batteries, graphene batteries, sodium-ion batteries, nickel-cobalt-manganese batteries, aluminum-ion batteries, or other battery types known in the art. The battery packs 20 are rechargeable and adapted to provide a source of electricity for an electric propulsion system (not shown). During charging, electricity from an external power source is used to replenish the energy stored in the battery packs 20, the external power source typically being Electric Vehicle Supply Equipment (EVSE). EVSE refers to the infrastructure, commonly known as a charging station or charging point, that supplies electric energy for recharging the battery packs 20. The stored electrical energy is then made available for the electric propulsion system or other power-consuming components, systems or subsystems of the vehicle 10.

The vehicle 10 comprises a battery management system, BMS 30, operating in tandem with the ESS 50 by monitoring and managing the individual battery cells 21 within the battery packs 20. Typically, each battery pack 20 is associated with a BMS controller. Alternatively, the BMS 30 may include a master controller configured to monitor and manage a plurality of battery packs 20. The BMS 30 ensures balanced charging and discharging, prevents overcharging or over-discharging, manages temperature, and optimizes overall performance and safety.

The vehicle 10 comprises a computer system 100 having processing circuitry 102. The processing circuitry 102 is configured for controlling activation of the plurality of battery packs 20 in parallel connection with one another. The disclosure is applicable for parallel connected battery packs due to the fact that more power and capacity are needed for certain application areas. When multiple battery packs are in parallel connection, the term activate shall in contexts of the present disclosure refer to the simultaneous engagement of a battery pack to other connected one or more battery packs to contribute collectively to an electrical output or storage capacity. Activating parallel battery packs thus allows for increased current delivery capability, which enhances power performance and facilitates a shared load-bearing capacity during specific operational demands. Activation of battery packs may occur during the occurrence of different operational events, including but not limited to the provisioning of electrical power to an electric motor or combustion engine, the receiving and storage of electrical energy from the EVSE, the provisioning of power to auxiliary systems, on-board equipment, lifting mechanisms, climate control systems or other devices or the like. Regardless of what type of reason there is for activating a plurality of battery packs in parallel connection, this may be done by causing transmission of control signals or specific commands to the BMS 30. The BMS 30 thereby dynamically manages the activation of battery packs 20 based on the received control signals or specific commands from the processing circuitry 102. This will be described in more detail with further reference to FIG. 2, showing an exemplary single battery pack, and FIG. 3, showing a parallel connection of a plurality of battery packs.

FIG. 2 shows an exemplary battery pack 20 comprising a battery circuit 22 having multiple battery cells 21. The open-circuit voltage UOCV of each battery cell 21 is a function of the state of charge and temperature UOCV=f(SoC, T). The battery pack 20 further includes a load R0, representing the internal ohmic resistance of the battery pack 20, and the current through this node is denoted as I/(t). The battery pack 20 further comprises a first controllable load 26-1 and a second controllable load 26-2. In other examples any suitable number of controllable loads 26 can be realized. The controllable loads 26-1, 26-2 represent devices or systems that draw electrical power from the output of the battery pack 20, such as a heater device, chiller device, electric machine, or practically any other device or auxiliary load having an electric output that can be controlled (e.g. increased or decreased). The first controllable load 26-1 introduces short-term polarization effects. It includes a parallel-connected resistor R1 and capacitor C1. Short-term polarization effects are phenomena that occur temporarily during certain conditions, such as high current demand, high charge/discharge rates, temperature extremes, partial state of charge operation, sudden changes in load, aging and wear, impurities or contaminants, or incomplete charging cycles, affecting the behaviour of the battery pack 20. The second controllable load 26-1 introduces long-term polarization effects. It includes a parallel-connected resistor R2 and capacitor C2. Long-term polarization effects are more persistent phenomena that affect the performance of the battery pack 20 over an extended period, such as cycling and cycling depth, state of charge extremes, consistently elevated temperatures, impurities and side reactions, over-charging or over-discharging, internal resistance changes or particle agglomeration.

Further shown in FIG. 2 is the processing circuitry 102, which is merely for illustrative purposes shown in conjunction with the battery pack 20. It shall however be understood that this is typically not the case, as the functionality of the processing circuitry 102 is typically implemented as a more central controller depending on the area of application, such as in a central computer system 100 of a vehicle 10. In any event, the processing circuitry 102 is configured to cause various control actions with respect to components of the battery pack 20.

The control actions involve an activation action of the battery pack 20. This may be done by controlling the controllable contactor 24 to be closed or opened based on control signals received from the processing circuitry 102. A control signal sent to the controllable contactor 24 may control the closing thereof. Electronically closing a controllable contactor is, as such, well known to the skilled person. However, in the present disclosure this is conditioned by the application of a compensation current that is adapted to counteract at least parts of a charge equalization current expected to be generated by the subsequent activation of an additional battery pack. Hence, the control actions carried out by the processing circuitry 102 further involve the determination of said compensation current, and the application of said compensation current. The activation of battery packs in conjunction with the determination and application of the compensation current will now be described in detail with further reference to the multiple battery packs 20-n shown in FIG. 3. While only one controllable contactor 24-n is shown in FIG. 3 per battery pack 20-n, it shall be understood that each battery pack 20-n in typical configurations may involve three of them; one positive contactor, one negative contactor, and one pre-charge contactor.

FIG. 3 shows an exemplary battery arrangement involving a plurality of battery packs 20-1, 20-2, 20-n. In this very example n is equal to three (i.e., the battery arrangement includes three battery packs), although it shall be understood that any alternative configuration of battery arrangements can alternatively be envisaged. Alternative configurations of battery arrangements may include any number of battery packs 20, each having any number of battery cells, controllable contactors, loads, controllable loads, power sources, or other circuitry components.

Each battery pack 20 (Bp1-n) includes a set of battery cells 21-1, 21-2, 21-n with open-circuit voltage UOCVBp1-n=f(SoC,T). Each battery pack 20 (Bp1-n) also includes the polarization effect vpBp1-n(t), internal ohmic resistance R0Bp1-n, controllable contactor 24-1, 24-2, 24-n and current I1-n. The sum of the open-circuit voltage UOCVBp1-n and the voltage drop that occurs due to the internal ohmic resistance R0 of each battery pack 20 results in the total overpotential. Over time, as the system stabilizes, the voltage will settle to the open-circuit voltage UOCVBp1-n alone, without any additional overpotential. The controllable contactor 24 is a switch that can be controlled to connect each battery pack 20 to or from the battery circuit 22. This is similar to the single battery pack 20 shown and explained with reference to FIG. 2, with the difference that this battery arrangement includes three battery packs 20-1, 20-2, 20-n and that the processing circuitry 102 may perform individual control to activate them one by one, for example by way of controlling the closing of the respective contactor 24-1, 24-2, 24-n. The battery packs 20-1, 20-2, 20-n are connected to a common controllable load 26. The controllable load 26 represents a device or system that draws electrical power from the combined output of the three battery packs 20-1, 20-2, 20-n, such as a heater device, chiller device, electric machine, or practically any other device which electric output is controllable. Moreover, a common voltage VESS(t) represents the collective voltage output of the three battery packs 20-1, 20-2, 20-n as a result of combining the individual voltages of the battery packs 20-1, 20-2, 20-n, and a common less is also provided. The controllable contactors 24-1, 24-2, 24-n allow for selective activation or deactivation of each battery pack 20-1, 20-2, 20-n in the battery circuit 22. When the controllable contactors 24-1, 24-2, 24-n are closed, the battery packs 20-1, 20-2, 20-n contribute to the common voltage VESS(t) and power delivery to the common controllable load 26. In other battery arrangement examples, each battery pack may include a separate controllable load, or a subset of the battery packs may be connected to a common controllable load, while another subset of battery packs include a separate controllable load for each battery pack included in said another subset of battery packs.

A general control procedure of activating the battery packs may be realized according to the following. The processing circuitry 102 is configured to activate the first battery pack 20-1. This is done by closing the contactor 24-1, thus allowing current to flow from an outlet of the first battery cells 21-1, through the battery circuit 22 via the controllable load 26 and back to an inlet of the battery cells 21-1. At this time, the additional battery packs 20-2, 20-n do not contribute to the common voltage VESS(t) and current IESS since they are not activated (their respective contactors 24-2, 24-n may be opened).

It is now envisaged that the present power application requires more energy, thus requiring the activation of the additional battery packs 20-2, 20-n. Thanks to the insights obtained by the inventors of the present disclosure, it is realized that a subsequent activation of additional battery packs 20-2, 20-n may cause unwanted charge equalization currents to be generated in the battery circuit 22, thereby inducing one or more of the disadvantageous effects mentioned in the background section. Therefore, instead of arbitrarily activating any number of additional battery packs 20-2, 20-n, a more intelligent activation procedure is proposed, which involves a selective and individual activation of the additional battery packs 20-2, 20-n based on a charge equalization current that is expected to be generated by a subsequent activation thereof.

The intelligent activation procedure involves determining a compensation current that is adapted to counteract at least parts of these unwanted charge equalization currents that are expected to be generated by the subsequent activation of the additional battery packs 20-2, 20-n to the battery circuit 22. In ideal operation conditions where all battery packs have exactly the same potential and internal resistance, there would be no equalization currents expected to be generated even when these are activated. However, in real-world scenarios, achieving perfect uniformity across all battery packs is practically impossible due to various factors, including but not limited to manufacturing variations, operating conditions and measurement limitations. Even within the same batch of batteries, individual batteries can have slight differences in capacity, self-discharge rates and internal resistance due to manufacturing variances. This is especially the case for different batches of batteries made by different manufacturers. Operating conditions such as temperature, age and usage history can also lead to variations in individual battery performance. Moreover, measuring the exact potential of each pack with perfect accuracy is impractical in certain applications, especially in high-voltage applications. Therefore, even if the initial potentials appear the same, these slight variations can cause small charge equalization currents to flow between the various battery packs to maintain balance over time. The charge equalization currents are accordingly expected to be generated due to the existence of these variations. For example, a first battery pack may have an open-circuit voltage of 700 V, and a second battery pack an open-circuit voltage of 702 V. In this example, the activation of these two exemplary battery packs in the same parallel configuration will cause an automatic balancing to occur so as to equalize a common open-circuit voltage to 701 V. In contexts of the present disclosure, a compensation current shall accordingly be interpreted as a current that, at least to some extent, prevents the equalization currents that are expected to occur from flowing between the battery pack that is to be subsequently activated and the other battery packs already included and activated in the battery circuit.

In some examples, the processing circuitry 102 is configured to determine the compensation current by a static estimation. The static estimation predicts the value of the compensation current based on a value of the charge equalization current that is expected to be generated by the activation of an additional battery pack. The value of the compensation current may vary depending on how excessive the charge equalization currents are. Typical values of the compensation current have been shown to range between 2 V and 3 V, but this is not to be seen as limiting in any way. Too low compensation current values may not mitigate the charge equalization currents sufficiently, but too high compensation current values may negatively affect various components of the battery circuit, such as the contactors 24-1, 24-2. 24-n. It may also lead to violation of battery discharge abilities.

The static estimation may be based on empirical data of previous compensation current determinations in battery packs. The empirical data may be one or more of performance data, health data, environmental data, aging data, activation data, and auxiliary data. Generally, this data may affect the compensation current that is to be generated in different ways. The exemplary empirical data may be considered one by one, several combined, or all combined, optionally as a weighted value. The static estimation may be based on a machine learning model, such as a machine learning model trained for solving a predictive task involving a mapping between input features (empirical data) to a desired output (the statically estimated value of the compensation current).

Performance data may include voltage and current profiles during activation, which can provide insights into an expected initial behaviour and/or potential stress experienced during activation. Performance data may include temperature variations during activation, which may indicate potential issues with heat generation or uneven cell balancing. Performance data may include energy consumption during activation, which may analyze the energy used during activation which may assist in assessing efficiency and identifying potential losses.

Health data (e.g. state of health, SoH) may include a capacity, such as a remaining capacity after activation, which can assist in understanding the impact of activation on overall battery capacity and potential degradation. Health data may include cell voltage data after activation, which can reveal any imbalances within the pack after activation relating to individual cell voltages. Health data may include internal resistance measurements, which can analyze changes in internal resistance for providing insights into the health of the battery pack.

Environmental data may correlate environmental factors with activation performance, including factors such as humidity or temperature, etc.

Aging data may relate to age and usage history of the battery pack, thus contextualizing how prior usage may affect activation behaviour.

Activation data may include time taken for the pack to be activated, which can assist in understanding the activation speed and potential delays in a system startup. Activation data may include a number of activation attempts typically required to activate an additional battery pack and whether there may be any issues with the activation process or communication between the battery pack and the computer system.

Auxiliary data may include error codes or warnings, system-related data of other units of the HV component, ESS, BMS or computer system, etc., load profile of the battery circuit, communication protocols used, maintenance history or logs, calibration and sensory information, external events or system disturbances, user-related data, cost and efficiency data, compliance data, and the like.

The compensation current may be determined as a part of the charge equalization current, e.g. 50%, 80% or 99% thereof, or a value that corresponds to the expected charge equalization current (i.e., substantially the same value). The compensation current may be determined in a compensation current range. The compensation current range may involve a first limit value being a maximum discharge ability of the battery pack to be activated. The maximum discharge ability of a battery pack is also known as a continuous discharge rate or maximum sustained discharge rate, referring to the highest current a battery pack can safely deliver continuously without experiencing damage or reduced lifespan. That is, the maximum discharge ability may be understood as the maximum rate at which the battery pack can be drained while maintaining its performance and integrity. Failure to meet this limit value in the compensation current range may cause excessive heat generation, electrode damage, performance degradation or lifespan reduction, to name some issues. The compensation current range is therefore preferably capped at this limit value in one end. In the other end, the compensation current range may comprise a second limit value being a minimum charge ability of the battery pack. This may offer some room to regulate the lower limit value based on e.g. system characteristics, battery properties, ambient conditions, application area, etc. The minimum charge ability of the battery pack may be substantially zero. That is, the compensation current range (ccr) can be seen as minimum charge ability<ccr<maximum discharge ability.

The compensation current may be based on a maximum allowed system limit. Hence, while the compensation range could in some examples include values up to the maximum discharge rate, some system requirements may cause the compensation current to be capped at a maximum allowed system limit which is specific to the area of application in which the battery packs are applied. The maximum allowed system limit may thus not allow a compensation current that is as high as the maximum discharge ability of the battery pack to be activated. The maximum allowed system limit may be determined by properties of the controllable load 26, or other loads of the battery circuit 22.

Once having determined the compensation current using any of the approaches discussed above, the processing circuitry 102 is configured to apply the compensation current to currently activated battery packs 20 within the battery circuit 22. In the example of FIG. 3 the battery pack that is currently activated is the first battery pack 20-1. The compensation current may be applied to the first battery pack 20-1 by way of controlling the controllable load 26. When the controllable load 26 is controlled to be decreased (i.e. reduce its resistance), the current in the battery circuit 22 increases, thereby introducing an excess current that can correspond to the compensation current. The compensation current is preferably applied before the additional battery pack 20-2 has been activated, although some variations may be realized where the compensation current is applied after the additional battery pack 20-2 has been activated, or optionally about the same time as the additional battery pack 20-2 (e.g. control signals are sent one after the other from the processing circuitry 102, possibly involving some minor signal delay) is activated.

Since the compensation current that at least partly counteracts the charge equalization currents expected to be generated by the activation of the additional battery pack 20-2 has now been introduced to the battery circuit 22, the additional battery pack 20-2 can be activated. The charge equalization currents expected to be generated in response thereto are thereby mitigated by way the introduced compensation current that is introduced to the battery circuit 22. Hence, even if the first battery pack 20-1 and the second battery pack 20-2 involves variations in potential, the inherent balancing therebetween are minimized. This may ensure compliance with power limits and enhance charging capabilities. Moreover, this approach may assist in avoiding lithium plating and safeguarding against battery degradation during charging processes. This strategic control may be particularly beneficial in challenging scenarios where charge equalization currents tend to be a greater issue, such as in cold weather conditions or situations with a high battery state of charge.

The above procedures of determining the compensation current, applying the compensation current, and activating an additional battery pack may be repeated for each additional battery pack to be activated. In the example of FIG. 3, the remaining battery pack is the third battery pack 20-3. The difference between the activation of the second battery pack 20-2 and the activation of the third battery pack 20-3 is that the compensation current is not only applied to the first battery pack 20-1, but also to the second battery pack 20-2 since it is now included as an activated battery pack in the battery circuit 22. The compensation may accordingly involve a different for each additional activation depending on presently activated battery packs in the battery circuit 22.

In some examples, the activation of an additional battery pack 20-2, 20-n may be based on a value of response signal data. In these examples, the processing circuitry 102 is configured to make one or more measurements of the battery circuit 22, for instance at its terminals. The terminals form a closed loop for the current flow, so measurements at these points can allow assessment of overall performance of the battery pack, including voltage, current, resistance, and the like. The measurements are made after the compensation current has been applied to the battery circuit 22 to assess whether the application thereof provides an expected behaviour of the current within the battery circuit 22. Accordingly, the additional battery pack 20-2, 20-n is in these examples activated based on a value of the response signal data. To make the assessment as regards to how the compensation current affects the total current of the battery circuit 22, the obtained response signal data may be compared to pre-stored data corresponding to measurements taken before the compensation current was applied. By way of applying the compensation current, assessing how the battery circuit 22 behaves, and responding to these changes in a subsequent battery pack activation, a more reliable activation control procedure may be obtained. This procedure may provide an improved charge equalization mitigation.

The order of which the battery packs 20-1, 20-2, 20-n are to be activated may vary depending on the battery configuration. In some examples, the battery packs 20-1, 20-2, 20-n are selected to be activated in a descending order of open-circuit voltages. In these examples, the first battery pack 20-1 is the battery pack having the highest open-circuit voltage, and the second battery pack 20-2 is the battery pack having the second highest open-circuit voltage, and so forth, until the battery pack having the lowest open-circuit voltage is selected for activation. In alternative examples this may be inverted, i.e., starting with the battery pack having the highest open-circuit voltage and selecting additional battery packs to be activated in an ascending order of open-circuit voltages. In yet alternative approaches, the activation selection may be randomized. However, the ascending/descending order is more easily predictable, which may provide a higher precision in the compensation current determination, and also with respect to power demands.

The compensation current determination and application, and the battery pack activation, may be carried out repeatedly until a time-out condition is met. This may be done automatically in response to the ongoing operation requiring the additional power/capacity from additional battery packs, for example due to an increased power demand being identified. The time-out condition may correspond to a point in time at which all of the battery packs in a battery system or a battery subsystem have been activated, thus maximizing what power that can be outputted by the system or subsystem. Alternatively, the time-out condition may correspond to a point in time when the battery circuit 22 to which the battery packs 20 are connected has reached a maximum feasible current throughput. The maximum feasible current throughput, which can also be referred to as the current carrying capability, refers to a highest current the battery circuit 22 can safely handle on a continuous basis without being subjected to issues or damages such as excessive heating, voltage sag, component limitations, etc. This may depend on internal properties such as wire gauge, material, circuit design, environmental factors, etc.

If the time-out condition is a maximum feasible current throughput, and an ongoing operation reaches said time-out condition, some examples may involve the introduction of a delay timer during which no further battery packs are activated. Hence, instead of cancelling (or optionally restarting) the operation, the operation may be set on hold until obtained battery data indicates an increase in the maximum feasible current throughput. This may indicate that continued operation of repeatedly determining a compensation current, applying the compensation current, and activating additional battery packs is possible. The battery data may be obtained from the battery management system 30, and the resumption of the operation may be done by cancelling the delay timer and setting a new time-out condition based on the updated maximum feasible current throughput indicated by the battery data. Several different factors may contribute to an increase in the maximum feasible current throughput, such as dynamic derating based on real-time conditions including changes in temperatures, loads or power demands, short-term surges or pulses, BMS adjustments, or the like.

To exemplify the above examples of a delay timer, a non-ideal scenario is envisaged. In an ideal scenario, the electrical system aims to distribute current across all battery packs until the total load is met or the system reaches its maximum current capacity. However, this may not always be the case due to the maximum feasible current throughput as explained above. The incorporation of the delay timer can therefore allow for some flexibility. For instance, if the system has a maximum current capacity of 15 A, but the demand is 20 A, the delay timer comes into play, giving the system time to adapt until the criteria are eventually met. One noteworthy consideration is the impact of loads on temperature, particularly when one of the loads functions as a heater. The increase in temperature can potentially enhance the available range, affecting the feasibility of drawing a specific amount of current. If the system cannot immediately fulfill the current demand, waiting becomes a strategic option. During this waiting period, the temperature gradually rises, influencing the power capability of the system. Continuous reporting by the battery packs through the BMS 30 may ensure that changes in temperature and power ability are consistently monitored. Consequently, when the temperature increases, the power capacity of the system also rises, providing an opportunity to meet the desired current requirements at a later point in time. This dynamic process may allow for efficient management of current demands, taking into account both system capabilities and the influence of temperature on performance.

With further reference to FIG. 4, an exemplary procedure for controlling activation of a plurality of battery pack is shown generally according to teachings of the present disclosure. In this example there are three battery packs being sequentially activated, starting with a first battery pack, then a second, and finally a third. The first and second battery pack involve similar open-circuit voltages, approximately v2, whereas the third battery pack involves an open-circuit voltage of approximately v3. These values v2, v3 may be any suitable voltage used in battery packs, such as any value in the range 600-800 V, or the like. In order to connect the third battery pack in parallel with the first and second battery packs without any risk of causing charge equalization currents, a compensation current determination and application is done by the processing circuitry of the computer system. The subplots 400a, 400b, 400c, 400d shown in FIG. 4 share the x-axis (time) from t0 seconds (start) to approximately t3 seconds (end). T0 may be zero, and t3 any time that the procedure can take. Purely by way of example, t3 may be 10 seconds, 100 seconds, 500 seconds, 1000 seconds, or any value less or higher that is suitable for different application areas. At t0 the first battery pack is already activated, at t1 the second battery pack is activated, and at t2 the third battery pack is activated.

The first subplot 400a shows voltage over time. At t1 the second battery pack is activated in parallel connection with the first battery pack, causing a short oscillation at 402-1 of the voltage of the first battery pack (pre-charge current). The voltage of the first and second battery packs are then balanced at 402-2, 404-1 until t2 occurs. Because of the voltages of the first and second battery packs being substantially similar, i.e. v2, there are no charge equalization currents flowing between the packs. At t2 when the third battery pack is connected, the voltages of the first and second battery oscillate and stabilize at 402-3, 404-2. During the entire time shown in subplot 400a, the voltage of the third battery pack remains at 406.

The second subplot 400b shows battery status over time. The battery status indicates how many of the battery packs are activated. As seen at t0, the first battery pack 412 is activated. At t1, the second battery pack 414 is activated, and at t2, the third battery pack 416 is activated.

The third subplot 400c shows two lines 420, 430 of currents over time. The first line 420 illustrates a total current of the ESS, and the second line 430 illustrates a requested load current. The total current of the ESS includes the sum of currents used for charging, discharging, and any internal losses within the ESS itself. The requested load current is the current drawn by the electrical load connected to the system, such as the controllable load 26 discussed herein. At t2, the total current of the ESS meets the requested load current. This means that the ESS is supplying the necessary electrical current to meet the demand of the connected load. This is when the connection attempt of the third battery pack is made. The compensation current is determined between the time periods t1 and t2, i.e., after the second battery pack has been activated in parallel connection with the first battery pack but before the third battery pack has been activated. The processing circuitry may then be configured to notify a master controller of the battery packs, such as a controller in the ESS overseeing the operation of the battery packs, of the determined compensation current. This is so it can be applied in conjunction with (typically before) the activation of the third battery pack.

The fourth subplot 400d shows charge equalization current over time for the first battery pack 442, the second battery pack 444, and the third battery pack 446. In the fourth subplot 400d when the third battery pack is connected at t2, it is shown that the compensation current has effectively eliminated (a0=0) charge equalization currents flowing from the third battery pack at 446-3 to the first and second battery packs at 442-4, 444-3.

FIG. 5 is a flowchart of a computer-implemented method 200 for controlling activation of a plurality of battery packs 20 in parallel connection. The method 200 comprises activating 210 a first battery pack 20-1 from among the plurality of battery packs 20. The method 200 further comprises determining 220 a compensation current which is adapted to counteract at least parts of a charge equalization current expected to be generated by a subsequent activation of an additional battery pack 20-n from among the plurality of battery packs 20. The method 200 further comprises applying 230 the compensation current to currently activated battery pack(s) 20. The method 200 further comprises activating the additional battery pack 20-n.

The computer system 600 may comprise at least one computing device or electronic device capable of including firmware, hardware, and/or executing software instructions to implement the functionality described herein. The computer system 600 may include processing circuitry 602 (e.g., processing circuitry including one or more processor devices or control units), a memory 604, and a system bus 606. The computer system 600 may include at least one computing device having the processing circuitry 602. The system bus 606 provides an interface for system components including, but not limited to, the memory 604 and the processing circuitry 602. The processing circuitry 602 may include any number of hardware components for conducting data or signal processing or for executing computer code stored in memory 604. The processing circuitry 602 may, for example, include a general-purpose processor, an application specific processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a circuit containing processing components, a group of distributed processing components, a group of distributed computers configured for processing, or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The processing circuitry 602 may further include computer executable code that controls operation of the programmable device.

The system bus 606 may be any of several types of bus structures that may further interconnect to a memory bus (with or without a memory controller), a peripheral bus, and/or a local bus using any of a variety of bus architectures. The memory 604 may be one or more devices for storing data and/or computer code for completing or facilitating methods described herein. The memory 604 may include database components, object code components, script components, or other types of information structure for supporting the various activities herein. Any distributed or local memory device may be utilized with the systems and methods of this description. The memory 604 may be communicably connected to the processing circuitry 602 (e.g., via a circuit or any other wired, wireless, or network connection) and may include computer code for executing one or more processes described herein. The memory 604 may include non-volatile memory 608 (e.g., read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), etc.), and volatile memory 610 (e.g., random-access memory (RAM)), or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a computer or other machine with processing circuitry 602. A basic input/output system (BIOS) 612 may be stored in the non-volatile memory 608 and can include the basic routines that help to transfer information between elements within the computer system 600.

Computer-code which is hard or soft coded may be provided in the form of one or more modules. The module(s) can be implemented as software and/or hard-coded in circuitry to implement the functionality described herein in whole or in part. The modules may be stored in the storage device 614 and/or in the volatile memory 610, which may include an operating system 616 and/or one or more program modules 618. All or a portion of the examples disclosed herein may be implemented as a computer program 620 stored on a transitory or non-transitory computer-usable or computer-readable storage medium (e.g., single medium or multiple media), such as the storage device 614, which includes complex programming instructions (e.g., complex computer-readable program code) to cause the processing circuitry 602 to carry out actions described herein. Thus, the computer-readable program code of the computer program 620 can comprise software instructions for implementing the functionality of the examples described herein when executed by the processing circuitry 602. In some examples, the storage device 614 may be a computer program product (e.g., readable storage medium) storing the computer program 620 thereon, where at least a portion of a computer program 620 may be loadable (e.g., into a processor) for implementing the functionality of the examples described herein when executed by the processing circuitry 602. The processing circuitry 602 may serve as a controller or control system for the computer system 600 that is to implement the functionality described herein.

The computer system 600 may include an input device interface 622 configured to receive input and selections to be communicated to the computer system 600 when executing instructions, such as from a keyboard, mouse, touch-sensitive surface, etc. Such input devices may be connected to the processing circuitry 602 through the input device interface 622 coupled to the system bus 606 but can be connected through other interfaces, such as a parallel port, an Institute of Electrical and Electronic Engineers (IEEE) 1394 serial port, a Universal Serial Bus (USB) port, an IR interface, and the like. The computer system 600 may include an output device interface 624 configured to forward output, such as to a display, a video display unit (e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)). The computer system 600 may include a communications interface 626 suitable for communicating with a network as appropriate or desired.

The operational actions described in any of the exemplary aspects herein are described to provide examples and discussion. The actions may be performed by hardware components, may be embodied in machine-executable instructions to cause a processor to perform the actions, or may be performed by a combination of hardware and software. Although a specific order of method actions may be shown or described, the order of the actions may differ. In addition, two or more actions may be performed concurrently or with partial concurrence.

Example 1: A computer system (100; 600) for controlling activation of a plurality of battery packs (20) in parallel connection, the computer system (100; 600) comprising processing circuitry (102; 602) configured to: activate a first battery pack (20-1) from among the plurality of battery packs (20); determine a compensation current which is adapted to counteract at least parts of a charge equalization current expected to be generated by a subsequent activation of an additional battery pack (20-n) from among the plurality of battery packs (20); apply the compensation current to currently activated battery pack(s) (20); and activate the additional battery pack (20-n).

Example 2: The computer system (100; 600) of example 1, wherein the processing circuitry (102; 602) is further configured to, sequentially for each additional battery pack (20-n) to be activated, perform the determination of the compensation current, the application of the compensation current, and the activation of the additional battery pack (20-n).

Example 3: The computer system (100; 600) of any of examples 1-2, wherein the processing circuitry (102; 602) is configured to: obtain response signal data from a battery circuit (22) to which the plurality of battery packs (20) are connected after the compensation current has been applied, and activate the additional battery pack (20-n) based on a value of the response signal data.

Example 4: The computer system (100; 600) of any of examples 1-3, wherein the processing circuitry (102; 602) is configured to determine the compensation current by a static estimation.

Example 5: The computer system (100; 600) of example 4, wherein the static estimation involves setting a predetermined voltage value based on empirical data of previous compensation current determinations in battery packs.

Example 6: The computer system (100; 600) of example 5, wherein the empirical data is one or more of performance data, health data, environmental data, aging data, activation data, and auxiliary data.

Example 7: The computer system (100; 600) of any of examples 5-6, wherein the processing circuitry (100; 600) is configured to provide the empirical data as training data to a machine learning model, the machine learning model being configured to map the empirical data to a prediction of the compensation current.

Example 8: The computer system (100; 600) of any preceding example, wherein the processing circuitry (102; 602) is configured to determine the compensation current in a compensation current range comprising a first limit value being a maximum discharge ability of the battery pack (20-n) to be activated.

Example 9: The computer system (100; 600) of example 8, wherein the compensation current range comprises a second limit value being a minimum charge ability of the battery pack (20-n) to be activated.

Example 10: The computer system (100; 600) of any of examples 1-9, wherein the processing circuitry (102; 602) is configured to determine the compensation current based on a maximum allowed system limit.

Example 11: The computer system (100; 600) of example 10, wherein the maximum allowed system limit is determined by properties of one or more controllable loads (26) in a battery circuit (22) to which the plurality of battery packs (20) are connected.

Example 12: The computer system (100; 600) of any of examples 1-11, wherein the first battery pack (20-1) comprises a higher open-circuit voltage compared to each one of the additional battery packs (20-n) to be activated, and wherein the processing circuitry (102; 602) is configured to activate each additional battery pack (20-n) in a descending order of open-circuit voltage.

Example 13: The computer system (100; 600) of any of examples 1-12, wherein the processing circuitry (102; 602) is configured to activate a battery pack (20) by controlling a closing of a controllable contactor (24) of a battery circuit (22) to which the plurality of the battery packs (20) are connected.

Example 14: The computer system (100; 600) of any of examples 1-13, wherein the processing circuitry (102; 602) is configured to apply the compensation current by controlling a controllable load (26) of a battery circuit (22) to which the plurality of the battery pack (20) are connected.

Example 15: The computer system (100; 600) of any of examples 1-14, wherein the processing circuitry (102; 602) is configured to repeatedly determine the compensation current, apply the compensation current, and activate the additional battery pack (20-n), until a time-out condition is met.

Example 16: The computer system (100; 600) of example 15, wherein the time-out condition is met once the plurality of battery packs (20) are activated.

Example 17: The computer system (100; 600) of any of examples 15-16, wherein the time-out condition is met once a battery circuit (22) to which the plurality of battery packs (20) are connected has reached a maximum feasible current throughput.

Example 18: The computer system (100; 600) of example 17, wherein in response to the battery circuit (22) reaches the maximum feasible current throughput, the processing circuitry (102; 602) is configured to: introduce a delay timer during which no further battery packs (20) are activated, obtain battery data from a battery management system (30), and in response to the battery data indicating an increase in the maximum feasible current throughput, cancel the delay timer and cause a continued operation of repeatedly determining the compensation current, applying the compensation current, and activating additional battery packs (20-n).

Example 19: The computer system (100; 600) of any of examples 1-18, wherein the plurality of battery packs (20) are arranged in a high-voltage component (40).

Example 20: The computer system (100; 600) of example 19, wherein the high-voltage component (40) is arranged in an energy storage system (50).

Example 21: The computer system (100; 600) of example 20, wherein the energy storage system (50) is arranged in a vehicle (10).

Example 22: A high-voltage component (40) comprising the plurality of battery packs (20) of any of examples 1-18, wherein the processing circuitry (102; 602) of the computer system (100; 600) of any of examples 1-18 is configured to control activation of the plurality of battery packs (20).

Example 23: An energy storage system (50) comprising the high-voltage component (40) of example 22.

Example 24: A vehicle (10) comprising the energy storage system (50) of example 23.

Example 25: A computer-implemented method (200) for controlling activation of a plurality of battery packs (20) in parallel connection, comprising: activating (210) a first battery pack (20-1) from among the plurality of battery packs (20); determining (220) a compensation current which is adapted to counteract at least parts of a charge equalization current expected to be generated by a subsequent activation of an additional battery pack (20-n) from among the plurality of battery packs (20); applying (230) the compensation current to currently activated battery pack(s) (20); and activating (240) the additional battery pack (20-n).

Example 26: A computer program product comprising program code for performing, when executed by the processing circuitry (102; 602), the method (200) of example 25.

Example 27: A non-transitory computer-readable storage medium comprising instructions, which when executed by the processing circuitry (102; 602), cause the processing circuitry (102; 602) to perform the method (200) of example 25.