Method for client-assisted battery calibration of a battery

Abstract

The invention relates to a method for client-assisted battery calibration of the battery of an electric vehicle or of a hybrid vehicle. The invention is characterized in that, as needed, a driver is actively prompted to switch the battery to a state in which its state-of-charge and / or capacity is determined if it was not possible to determine its state-of-charge and / or capacity for a certain predefined use of the vehicle.

Description

[0001] Mercedes-Benz Group AG

[0002] Procedure for customer-assisted battery calibration of a battery

[0003] The invention relates to a method for customer-assisted battery calibration of a battery of electric or hybrid vehicles according to the type defined in more detail in the preamble of claim 1.

[0004] In principle, methods for customer-assisted battery calibration are known from the state of the art. In the automotive industry, these are of interest for batteries based on lithium-ion cells that are installed in electric vehicles (EVs), hybrid vehicles (HEVs), plug-in hybrid vehicles (PHEVs) or other electric vehicles. Such batteries comprise many individual lithium-ion cells, measurement technology for current, voltage and temperature of the cells as well as a battery management system (BMS), which is used, among other things, to determine the state of charge. State determination is used to monitor cell states. Important cell states include, for example, a state of charge (SOC) and a capacity, which represents a typical amount of charge between a full state and a dead state, i.e. between 100% and 0% SOC.

[0005] To determine a range forecast and a charging power approval, a precise determination of these conditions is essential. Therefore, inaccurately determined SOC values ​​and capacity values ​​lead to inaccurate range forecasts and possibly incorrect charging power approvals. An incorrectly determined charging power that is too low results in an incorrectly determined charging time that is too long for the customer or driver. Likewise, an incorrectly determined charging power that is too high can cause irreversible damage to the battery cells. The terms customer and driver can be used synonymously here. For lithium iron phosphate-based battery cells (LFP-based battery cells), determining the SOC at rest, i.e. when the vehicle is stationary, is more difficult in the battery management system than, for example, for nickel manganese cobalt oxide-based battery cells (NMC-based battery cells).This is due, among other things, to the flatter shape of the open-circuit voltage (OCV) characteristic curve over a large SOC range. As a result, a measured open-circuit voltage cannot be converted into an SOC using this characteristic curve in all conditions. Furthermore, the conversion is complicated by common effects such as temperature dependence (entropy) and hysteresis of the open-circuit voltage characteristic curve.

[0006] As a result, the capacity of LFP-based battery cells is also difficult to determine. Capacity is typically determined by at least two different SOC states and the amount of charge flowing between these states, expressed, for example, in ampere-hours. This amount of charge can be used to determine whether the battery is fully charged or empty. However, since the SOC cannot be determined over wide SOC ranges using the open-circuit voltage characteristic, the capacity cannot be determined in this way either.

[0007] Therefore, different approaches exist in the state of the art. For example, a customer or driver is recommended to fully charge LFP-based batteries regularly once a week. This may solve the problem of determining the SOC at rest, but not the problem of determining the capacity, since the second SOC value is not determined. Other methods are known, in which a filter method, such as a sigma-point Kalman filter or a particle filter, is used to estimate the SOC and other states using models. However, this results in high computational requirements, coupled with high data and validation costs.

[0008] The object of the present invention is to create a method that overcomes the aforementioned disadvantages. This method should be particularly suitable for lithium-ion cells and enable accurate determination of the state of charge (SOC) and capacity. According to the invention, this object is achieved by a method having the features in claim 1, and in particular in the characterizing part of claim 1. Advantageous embodiments and further developments are set out in the dependent claims.

[0009] At the core of the method according to the invention, a driver is actively prompted, as needed, to bring the battery into a state for determining the state of charge and / or the capacity if no state of charge determination and / or no capacity determination was possible for a certain predefined use of the vehicle. According to the invention, the customer or the driver is therefore actively involved in the method in order to enable an SOC estimation and a capacity estimation in the battery management system. A predefined use can, for example, be a time, an energy throughput, a distance traveled or the like. If no SOC determination and / or no capacity determination was possible, the battery was not in a suitable state for this purpose. Consequently, the driver can improve the service life of the battery cells through active intervention. The term battery also refers to a plurality of batteries orto understand all batteries that are installed in the vehicle.

[0010] The process for customer-assisted battery calibration is suitable for electric vehicles, hybrid vehicles, plug-in hybrid vehicles, or other electric vehicles. The driver can be informed of the necessary steps via a display, for example, in conjunction with a head unit or an application (app).

[0011] Preferably, the driver can be given a notification regarding a battery calibration process. Such notifications can include a recommendation as to how the driver can actively intervene to enable a SOC or capacity determination. This way, the driver or another vehicle occupant can be prompted, as needed, to actively bring the battery into a state suitable for SOC determination. A notification can contain requests such as "Please (dis)charge your vehicle to x% SOC." The percentage can be specified individually; for example, it could be 20% or 100%. Other values ​​are also conceivable. According to a very advantageous development of the concept, it can be provided that the driver can agree to the battery calibration process by activating a process, or reject the battery calibration process by deactivating the process.Depending on the driver's decision, a targeted battery calibration process can be initiated and run. Such a calibration process can, for example, involve a controlled charging process and / or a controlled discharging process, as described below. The driver can therefore specify the time at which the respective process is started.

[0012] According to an advantageous embodiment, it can be provided that a controlled charging or discharging process can be initiated by the driver. During such a charging or discharging process, the battery can be specifically brought into advantageous states, which have a positive effect on the battery's service life. The battery can therefore be operated gently and charged or discharged optimally with regard to performance during operation.

[0013] A further advantageous embodiment may provide for the controlled charging or discharging process to include unidirectional or bidirectional charging. Other charging or consumption options are also conceivable.

[0014] According to an advantageous embodiment, it can be provided that the battery is deliberately brought into state-of-charge ranges that enable and / or improve state-of-charge and / or capacity determination. For example, the driver can also be suggested a battery usage option that is both battery-friendly in terms of service life and optimized in terms of operation.

[0015] A further advantageous embodiment may provide for a favorable charging current and / or a reduction or increase of the charging current in favorable state-of-charge ranges. This can also optimize the service life and operation of the battery.

[0016] According to an advantageous embodiment, the values ​​determined for the state-of-charge determination and / or the capacity determination can be displayed to the driver. This can be done via a display in the vehicle and / or using a smartphone app.

[0017] Overall, it is therefore advantageous to motivate the driver or another vehicle occupant in a targeted and as-needed manner to ensure the necessary use of the battery for stable and optimal operation. The proposed improved SOC and capacity determination can enable an improved range forecast and / or improved charging power release. This can positively influence battery life. The method therefore allows the driver to specifically influence the battery's calibration status. The method can also be used to determine a residual battery value, which is directly dependent on a residual capacity, for example, using a targeted process at a given time and, for example, to display it as required.

[0018] Further advantages of the method according to the invention also emerge from the remaining dependent subclaims and become clear from the exemplary embodiments which are described in more detail below with reference to the figures.

[0019] Showing:

[0020] Fig. 1 shows a possible embodiment of the method;

[0021] Fig. 2 shows another possible embodiment of the method.

[0022] Fig. 1 shows a schematic representation of a possible embodiment of method 1. In step 2, for example, it can be determined that the SOC of the battery is poorly calibrated. This can be shown to the driver, for example, on a display in the vehicle, on a smartphone or another mobile device. In step 3, the driver can be given a hint to set a specific SOC. This can be done by a request such as "Please charge the vehicle to 30% SOC." Any percentage can be specified. Likewise, a hint can be given to discharge the vehicle to a certain SOC. For example, a hint could be: "Please fully charge the battery and let the vehicle stand for 2 hours." In a further recommendation for battery calibration, a hint orA prompt may be displayed, such as "Please park the vehicle below 30% SOC and above 10°C. Connect the charging cable and activate battery calibration. The charging time will be extended by 3 hours." These are merely examples; any time and temperature setting is possible. In step 4, the battery's SOC can be recalibrated. This can also be displayed to the driver accordingly.

[0023] Another embodiment of method 1 is schematically illustrated in Fig. 2. Here, in step 5, for example, the driver can be informed that the battery capacity is poorly calibrated. This can also be done via a display, as described above. In step 6, the driver can be prompted to specifically set a specific SOC and allow calibration. In step 7, a charging or discharging procedure can specifically trigger states to calibrate the capacity.

[0024] Using the methods described 1, battery calibration can therefore be controlled through active intervention by the customer or driver.

[0025] Of course, the described variants of method 1 in Figures 1 and 2 can also be combined with each other, creating various possibilities. For example, a state of charge and capacity can be assessed in just one step.

Claims

Mercedes-Benz Group AG Patent claims 1. Method (1) for customer-assisted battery calibration of a battery of an electric vehicle or a hybrid vehicle, characterized in that a driver is actively requested, as needed, to bring the battery into a state for state-of-charge determination and / or capacity determination if no state-of-charge determination and / or no capacity determination was possible for a certain predefined use of the vehicle.

2. Method (1) according to claim 1, characterized in that the driver is given an indication of a battery calibration process.

3. Method (1) according to claim 2, characterized in that the driver can agree to the battery calibration process by activating a process or reject the battery calibration process by deactivating the process.

4. Method (1) according to one of claims 1 to 3, characterized in that a controlled charging or discharging process can be started by the driver.

5. Method (1) according to claim 4, characterized in that the controlled charging or discharging process comprises unidirectional or bidirectional charging. Method (1) according to one of claims 1 to 5, characterized in that the battery is deliberately brought into state-of-charge ranges that enable and / or improve a state-of-charge determination and / or a capacity determination. Method (1) according to one of claims 1 to 6, characterized in that an advantageous charging current and / or a reduction or increase of the charging current in advantageous state-of-charge ranges occurs. Method (1) according to one of claims 1 to 7, characterized in that determined values ​​of the state-of-charge determination and / or the capacity determination are displayed to the driver.

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