DE102014203417A1 - Method for monitoring a state of charge - Google Patents

Abstract

The invention relates to a method for monitoring a state of charge (SOC) of a battery in a driving operation of a vehicle, having the following steps: a) determining a current state of charge (SOCakt) of the battery, b) determining a minimum state of charge (SOCmin, SOCred, min), wherein the minimum state of charge (SOCmin, SOCred, min) is adapted to the ambient temperature, and c) initiating a charging process of the battery when the current state of charge (SOCakt) falls below the determined minimum state of charge (SOCmin, SOCred, min). The invention also relates to a computer program and a battery system, which are designed and / or set up for carrying out the method, as well as to a vehicle having such a battery system.

Description

State of the art

The invention relates to a method for monitoring a state of charge of a battery. The invention also relates to a computer program and a battery system, which are designed and / or set up for carrying out the method, as well as to a vehicle having such a battery system.

In electric vehicles or hybrid vehicles battery systems are used to provide electrical energy for driving the vehicle. Such battery systems include a battery having a plurality of battery cells and a battery management system that monitors and controls the battery. For this purpose, the battery and its battery cells are equipped with sensors that provide the battery management system with various state parameters, such as the current battery temperature, the current battery current, the current cell currents and the current cell voltages. Based on the state parameters, the battery management system implements management functions that increase battery life, reliability, and safety.

For example, a safety function of the battery management system relates to the cold start capability of an internal combustion engine when, instead of a 12 V battery, the battery is to be used for driving the vehicle to start the internal combustion engine.

Out DE 10 2012 205 017 A1 a method for operating an internal combustion engine is known, which is part of a hybrid drive with at least one electrical energy storage. In the method, a heating element and the internal combustion engine are activated as a function of the state of charge of the electrical energy store. Thus, the internal combustion engine is activated at a low state of charge. A cold start from hibernation ensures that the charge in the battery is sufficient to both heat the lambda probe to its operating temperature and to start the engine. With regard to the lambda probe, parameters such as the ambient temperature or the amount of condensed water in the exhaust pipe from aborted cold starts of the engine are taken into account.

In DE 10 2008 048 519 A1 is described a transporter with hybrid drive, wherein the electric motor performs, inter alia, the starting process of the internal combustion engine. When the combustion engine is switched off, the drive battery may only be drained to the extent that the combustion engine can still be safely started. External operating conditions, such as the outside temperature or the engine temperature, are also taken into account for the calculation of the engine starting energy to be provided from the vehicle battery.

DE 10 2009 034 765 A1 describes a method for starting an internal combustion engine in a hybrid vehicle, which ensures successful starts of the internal combustion engine even at very low battery temperatures and thus ensures maximum vehicle availability at low battery temperatures. The starting speed of the internal combustion engine is determined by the temperature of the electrical energy storage.

In order to ensure the cold start capability of the internal combustion engine, it is necessary that the battery has a residual charge when the vehicle is parked. This reduces the available capacity of the battery. There is therefore a continuing interest in improving the safety function of cold start capability.

Disclosure of the invention

• a) Ermitteln eines aktuellen Ladezustandes der Batterie,
• b) Ermitteln eines minimalen Ladezustandes, wobei der minimale Ladezustand an die Umgebungstemperatur angepasst wird, und
• c) Initiieren eines Ladevorganges der Batterie, wenn der aktuelle Ladezustand den minimalen Ladezustand unterschreitet.

According to the invention, a method is proposed for monitoring a state of charge of a battery in a driving operation of a vehicle, comprising the following steps:

• a) determining a current state of charge of the battery,
• b) determining a minimum state of charge, wherein the minimum state of charge is adapted to the ambient temperature, and
• c) initiate a charging of the battery when the current state of charge falls below the minimum state of charge.

A battery or a rechargeable battery in this case denotes a unit with a plurality of battery cells or accumulator cells, which are preferably spatially combined and interconnected by circuitry, for example, connected in series or in parallel to battery modules or accumulator modules. Thus, the battery can provide the necessary drive power for vehicles such as electric vehicles or hybrid vehicles.

The vehicle is preferably designed as a hybrid vehicle comprising an electric drive system and an internal combustion engine. In this case, the battery of hybrid vehicles can be charged internally via a generator with excess energy of the engine. Additionally, plug-in hybrid electric vehicles (PHEVs) provide the option of charging the battery via an external power grid.

The driving operation in the present context denotes an operating phase in which the Vehicle is driven by means of the battery and / or the internal combustion engine.

The current state of charge (SOC) of the battery indicates the still available capacity of the battery in relation to a full charge, which corresponds to a state of charge of 100%. The minimum state of charge of a battery corresponds to a state of charge, which allows a cold start of an internal combustion engine after the vehicle has been switched off.

The state of charge can be determined by measuring different state parameters of the battery, the battery cells and / or the battery modules. For example, a voltage can be measured as a state parameter approximately in the form of voltage-dependent discharge curves. To determine the state of charge, state parameters can be detected with the aid of sensor units, which can be implemented, for example, as a cell supervision circuit at the output of the battery cells or as module monitoring units at the output of the battery modules. The sensor units can thus monitor individual battery cells or individual battery modules and provide corresponding data to a control unit on which a battery management system can be implemented. For example, data may be exchanged between the sensor units and the controller via a bus, such as a Serial Peripheral Interface Bus (SPI bus) or a Controller Area Network Bus (CAN bus).

In one embodiment, the possible, i. H. can be determined minimum charging states at least a first minimum state of charge and a second minimum state of charge, wherein the first minimum state of charge is greater than the second minimum state of charge. Preferably, the first and the second minimum state of charge are predefined stored in a memory. Thus, depending on the ambient temperature, a corresponding value for the minimum state of charge can be provided. In this case, a temperature sensor on the vehicle can detect the ambient temperature and provide it to a control unit on which the battery management system can be implemented.

In another embodiment, the minimum state of charge is set to a first minimum state of charge when the ambient temperature is less than or equal to a threshold. In another embodiment, the minimum state of charge is set to a second minimum state of charge when the ambient temperature is greater than a threshold. For example, when the ambient temperature is ≦ 0 ° C, the first minimum state of charge is set as the minimum state of charge value. For example, if the ambient temperature is> 0 ° C, the second minimum state of charge is set as the minimum state of charge value. This exploits the fact that the cold-start capability is given at ambient temperatures of, for example, more than 0 ° C., even with a low charge state.

In another embodiment, prospective ambient temperatures are provided for a future period of time, and the minimum state of charge is adjusted based on the anticipated ambient temperatures. The anticipated ambient temperatures may be provided, for example, for a few hours or days in a database, such as a weather service, accessible via a communications link such as a GSM module (Global System for Mobile Communications Module). Thus, the ambient temperatures for the future period may be communicated to the GSM module, which may be associated with the vehicle or battery, and provided to a controller on which the battery management system is implemented. If the GSM module is assigned to the vehicle, the ambient temperatures can be provided via a CAN bus to the control unit on which the battery management system is implemented.

In a further embodiment, the charging process is initiated at the latest before the end of the driving operation. This ensures that when parking the vehicle, the minimum state of charge is achieved and thus the cold start capability is given. To initiate the charging process, the internal combustion engine can be started and used to charge the battery.

In a further embodiment, when the minimum state of charge is undershot, a condition is set after which the driving operation is not ended before a charging process is initiated and completed. This condition can be cleared if during driving the current state of charge is greater than the minimum state of charge or equal to the minimum state of charge. So it can be ensured that the minimum charge state when parking the vehicle is given. At the same time, it is possible to respond flexibly to situations in which it is not necessary to charge the battery by the internal combustion engine when the battery is being charged by recuperation in a braking operation, for example.

According to the invention, a computer program is also proposed according to which one of the methods described herein is performed when the computer program is executed on a programmable computer device. The computer program may be For example, it may be a software module, a software routine, or a software subroutine for implementing a battery management system on a controller of a vehicle. The computer program can be stored on a machine-readable storage medium, for example on a permanent or rewritable storage medium or in association with a computer device, for example on a portable memory, such as a CD-ROM, a DVD, a Blu-ray Disc, a USB stick or a memory card. Additionally or alternatively, the computer program may be provided for download on a computing device, such as a server or a cloud server, for example via a data network, such as the Internet or a communication link, such as a telephone line or wireless connection.

• a. eine Einheit zum Ermitteln eines aktuellen Ladezustandes der Batterie im Fahrbetrieb;
• b. eine Einheit zum Ermitteln eines minimalen Ladezustandes, wobei der minimale Ladezustand an die Umgebungstemperatur angepasst wird, und
• c. eine Einheit zum Initiieren eines Ladevorganges der Batterie, wenn der aktuelle Ladezustand den minimalen Ladezustand unterschreitet.

According to the invention, a battery system for monitoring a state of charge of a battery while driving a vehicle is provided with the following components:

• a. a unit for determining a current state of charge of the battery while driving;
• b. a unit for determining a minimum state of charge, wherein the minimum state of charge is adapted to the ambient temperature, and
• c. a unit for initiating a charging process of the battery when the current state of charge falls below the minimum state of charge.

Preferably, the battery system is designed and / or set up to carry out the methods described herein. Accordingly, features described in the context of the method correspondingly apply to the battery system, and vice versa, the features described in the context of the battery system accordingly for the method. The battery of the battery system may be configured as a lithium-ion battery or nickel-metal hydride battery. Furthermore, the battery system can be connectable to a drive train of a vehicle.

The components of the battery system are to be seen as functional units that are not necessarily physically separated from each other. Thus, multiple components of the battery system may be implemented in a single physical unit, such as when multiple functions are implemented in software on a controller. Furthermore, the functions of the components can also be realized in hardware, for example by sensor units or memory units. In particular, the components b are preferred. and c. of the battery system implemented by software in the battery management system on a control unit.

In one embodiment, component c. In addition, a component for determining deviation points in the time course of the operating parameter. In the case of deviations, deviation points can be stored in the storage unit as usage parameters. The storage unit for storing the usage data is preferably a non-volatile storage unit, for example an EEPROM (electrically erasable programmable read-only memory) of the control unit. The detected time profile is preferably stored in a volatile memory unit, for example a RAM (Random Access Memory) of the control unit.

According to the invention, a vehicle with the battery system described herein is also proposed. Preferably, the vehicle is an electrically driven vehicle, such as a hybrid vehicle or an electric vehicle, which is at least partially driven by electrical energy of a battery having a plurality of battery cells. For this purpose, the battery system is connected in particular to the drive system of the vehicle.

Advantages of the invention

The invention makes it possible to adapt the minimum state of charge of the battery flexibly to the conditions in the environment of the vehicle. In particular, the range of the electric drive is effectively increased by the start-optimized operating strategy, with a minimum state of charge adapted to the ambient temperature. At the same time, however, it is ensured that the battery ideally always provides sufficient starting power. To ensure long-term cold-start capability, additional data, such as a weather service, can be included in the operating strategy.

Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

Show it:

1 an at least partially electrically powered vehicle having a battery system, and

2 an exemplary course of a state of charge using the method according to the invention.

In the following description of the embodiments of the invention, the same or similar components are denoted by the same or similar reference numerals, wherein in individual cases a repeated description of these components is omitted. The figures illustrate the subject matter of the invention only schematically.

Embodiments of the invention

1 shows an at least partially electrically powered vehicle 10 with a battery system 12 ,

The vehicle 10 of the 1 is a hybrid vehicle that also has an internal combustion engine 13 has, designed. Here is the vehicle 10 with an electric drive system 14 equipped, that the vehicle 10 via an electric motor (not shown) at least partially electrically drives. The electrical energy is coming from the battery system 12 provided a battery 16 and a battery management system 18 includes. The internal combustion engine 13 serves both to drive the vehicle 10 as well as to charge the battery 16 ,

The battery 16 includes several battery cells 19 , which can also be referred to as accumulator cells and are operated, for example, as lithium-ion cells with a voltage range of 2.8 to 4.2 volts. The battery cells 19 are in groups to battery modules 20 summarized. To individual battery cells 19 or battery modules 20 These are with cell monitoring units 22 or module monitoring units 23 equipped, the state parameters, such as a voltage, a current or a temperature, individual battery cells 19 or individual battery modules 20 capture and the captured condition parameters to the battery management system 18 provide. For example, the state parameters can be over a bus 24 such as a Serial Peripheral Interface (SPI) bus or a Controller Area Network Bus (CAN) bus from the cell monitoring units 22 or module monitoring units 23 to the battery management system 18 be transmitted.

The battery management system 18 implements functions to control and monitor the battery 16 , This is the way the battery management system points 18 one unity 26 for receiving state parameters from the cell monitoring units 22 or the module monitoring units 23 be recorded. The one from the unit 26 received state parameters, in particular cell voltages and module voltages, become one unit 28 for determining a current state of charge SOC _{akt of} the battery 16 provided. One unity 29 for determining a minimum state of charge SOC _min , SOC _{red, min} adjusts the minimum state of charge SOC _min , SOC _{red, min} to an ambient temperature. This is a unit 30 the ambient temperature ready, for example, from a temperature sensor 32 of the vehicle 10 is captured and sent to the unit 30 for providing the ambient temperature is transmitted. Additionally or alternatively, ambient temperatures for future periods may be via a GSM module 31 of the vehicle 10 from a database, and the unit 29 be provided for determining the minimum state of charge SOC _min , SOC _{red, min} . One unity 34 to initiate a charging process compares the current state of charge SOC _akt , that of the unit 28 is provided with the minimum state of charge SOC _min , SOC _{red, min} , that of the unit 29 provided. If the current state of charge SOC _{act falls below} the minimum state of charge SOC _min , SOC _{red, min} , then the charging process is initiated.

2 shows an exemplary course of a current state of charge SOC _act using the method _according to the invention.

In 2 is the state of charge SOC in percent (%) of the full charge of the battery 16 plotted against time t. Takes the vehicle 10 at time t ₀ driving with the electric drive system 14 on, then the current state of charge SOC _{akt takes} the battery 16 from SOC _max , which corresponds for example to a full charge of 100%, continuously. At time t ₁ , the current state of charge SOC _{act reaches} a first minimum state of charge SOC _min , which corresponds, for example, to 20% of the full charge. In this case, the first minimum state of charge SOC _{min is} the state of charge, which is for a cold start of the internal combustion engine 13 at a temperature ≤ 0 ° C is necessary.

If the ambient temperature at time t _{1 is} greater than 0 ° C and the ambient temperature depending on the service life of the vehicle 10 over a period of, for example, a few hours or days presumably remain at more than 0 ° C, then the first minimum state of charge SOC _{min is} reduced to a second minimum state of charge SOC _{red, min} . For example, the second minimum state of charge SOC _{red, min is} reduced to only 8% of the full charge, since at temperatures above 0 ° C, a state of charge of 8% of the full charge for a cold start of the engine 13 suffice. By this reduction of the first minimum state of charge SOC _min , the energy content of the battery that is effectively available becomes 16 and thus the range of the vehicle 10 elevated.

If the current state of charge SOC _act decreases at time t ₂ below the second minimum state of charge SOC _{red, min} for ambient temperatures greater than 0 °, then a charging process is initiated. At the same time the internal combustion engine becomes 13 switched on to the battery 16 to load. After a recharge phase, the duration of which is maintained by the system taking into account other circumstances, such as the Available energy of the internal combustion engine 13 or possible loss of comfort by the driver, can be determined, the internal combustion engine 13 be switched off and the charging process will be terminated. In the illustrated embodiment in 2 the charging process is terminated at time t ₃ . Between the times t ₃ and t ₄ , an ordinary operation of the vehicle takes place 10 , At time t ₄ , the vehicle 10 switched off.

However, if the ambient temperature drops to ≤ 0 ° C or the ambient temperature changes depending on the service life of the vehicle 10 over a period of, for example, a few hours or days presumably fall to ≤ 0 ° C, then the charging is performed when the current state of charge SOC _{act reaches} the first minimum state of charge SOC _min for ambient temperatures ≤ 0 ° C or already below the first minimum state of charge SOC _min is located. To determine the anticipated ambient temperature for a period of, for example, a few hours or days, weather service data may be used. This is done for example via the GSM module 31 (Global System for Mobile Communications Module), which is in the vehicle 10 is provided. The battery management system 18 can thus query the ambient temperatures for the next hours or days and thus the expected ambient temperatures. If the ambient temperatures remain ≤ 0 ° C, then the first minimum state of charge SOC _min remains in the example shown at 20% of the full charge.

Alternatively, the minimum state of charge SOC _min , SOC _{red, min} for ambient temperatures ≤ 0 ° C can still be set to the second minimum state of charge SOC _{red, min} . In this variant, the in 2 exemplified by a dashed line 40 is shown, however, before parking the vehicle 10 a charging operation forced, provided that the current state of charge SOC _{act is} smaller than the first minimum state of charge SOC _min for ambient temperatures ≤ 0 ° C. In this case, for example, at the time t ₄ , at which the driver wishes to end the driving operation, the key can be blocked or in a caster of the internal combustion engine 13 be started until the current state of charge SOC _{act has reached} at least the first minimum state of charge SOC _min . A battery 16 For example, it can be temporarily charged to 100% at 6 C in 10 minutes. In this case, C designates the charging current related to the capacity of the battery, with charging at 1 C the battery is fully charged within one hour. An increase of 2.5% can be achieved in about 15 s. In the example shown in FIG 2 is reached until the time t ₅ a state of charge, which is well above the first minimum state of charge SOC _min .

In doing so, the battery management system provides 18 the minimum state of charge SOC _min , SOC _{red, min} the control unit of the internal combustion engine 13 ready. The adjustment updates this value. As a result, an engine start can be required in the engine control unit at the latest until the end of the journey. Increases the current state of charge SOC _act due to other energy, such as a recuperation, the required engine start can be deleted. Will in the meantime the vehicle 10 turned off, the required engine start is performed.

The invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, within the scope given by the claims a variety of modifications are possible, which are within the scope of expert action.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102012205017 A1 [0004]
• DE 102008048519 A1 [0005]
• DE 102009034765 A1 [0006]

Claims (11)

Method for monitoring a state of charge (SOC) of a battery ( 16 ) in a driving operation of a vehicle ( 10 ) with the following steps: a) determining a current state of charge (SOC _akt ) of the battery ( 16 ), b) determining a minimum state of charge (SOC _min , SOC _{red, min} ), wherein the minimum state of charge (SOC _min , SOC _{red, min} ) is adapted to the ambient temperature, and c) initiating a charging process of the battery ( 16 ), when the current state of charge (SOC _act ) below the determined minimum state of charge (SOC _min , SOC _{red, min} ). The method of claim 1, wherein the possible minimum states of charge (SOC _min, SOC _{red, min)} at least one first minimum state of charge (SOC _min), and a second minimum state of charge (SOC _{red, min),} wherein the first minimum state of charge (SOC _min) is greater than the second minimum state of charge (SOC _{red, min} ). The method of claim 2, wherein the minimum state of charge (SOC _min , SOC _{red, min} ) is set to a first minimum state of charge (SOC _min ) when the ambient temperature is less than or equal to a threshold. The method of claim 2 or 3, wherein the minimum state of charge (SOC _min , SOC _{red, min} ) is set to a second state of charge (SOC _{red, min} ) when the ambient temperature is greater than a threshold value. Method according to one of claims 1 to 4, wherein the prospective ambient temperatures are provided for a future period, and the minimum state of charge (SOC _min , SOC _{red, min} ) is adjusted based on the expected ambient temperatures. Method according to one of claims 1 to 5, wherein the charging process is initiated at the latest before completion of the driving operation, when the current state of charge (SOC _act ) below the minimum state of charge (SOC _min , SOC _{red, min} ). Method according to one of claims 1 to 6, wherein when falling below the minimum state of charge (SOC _min , SOC _{red, min} ), a condition is set, after which the driving operation is not terminated before a charging process is initiated and completed. The method of claim 7, wherein the condition is deleted when during driving the current state of charge (SOC _act ) greater than the minimum state of charge (SOC _min , SOC _{red, min} ) or equal to the minimum state of charge (SOC _min , SOC _{red, min} ) is. A computer program performing a method according to any one of claims 1 to 8 when the computer program is executed on a programmable computer device. Battery system ( 12 ) for monitoring a state of charge (SOC) of a battery ( 16 ) in a driving operation of a vehicle ( 10 ) with the following components: a. one unity ( 26 ) for determining a current state of charge (SOC _akt ) of the battery ( 16 ); b. one unity ( 29 ) for determining a minimum state of charge (SOC _min , SOC _{red, min} ), wherein the minimum state of charge (SOC _min , SOC _{red, min} ) is adapted to the ambient temperature, and c. one unity ( 34 ) for initiating a charging process of the battery ( 16 ), when the current state of charge (SOC _act ) falls below the minimum state of charge (SOC _min , SOC _{red, min} ). Vehicle ( 10 ) with a battery system ( 12 ) according to claim 10.

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