EP1567877A1

EP1567877A1 - Method and device for determining battery status

Info

Publication number: EP1567877A1
Application number: EP03779842A
Authority: EP
Inventors: Harald Braun; Christof Gross; Franz Nietfeld; Liane Schupp
Original assignee: DaimlerChrysler AG
Current assignee: Daimler AG
Priority date: 2002-12-04
Filing date: 2003-11-05
Publication date: 2005-08-31
Also published as: JP2006508847A; US20060091848A1; DE10256588A1; DE10256588B4; WO2004051295A1

Abstract

The invention relates to a method and a device for determining battery status. The battery status is determined by measuring the voltage of a vehicle battery during the start procedure over a given period, determination of a minimum voltage level of the vehicle battery during said period of the measuring process, evaluation of the charge status of the vehicle battery based on the minimum voltage level and control of the generator based on the evaluation of the charge status of the vehicle battery, such that an adequate supply for the vehicle electrical system and an adequate charging of the vehicle battery are guaranteed and the fuel consumption and emission discharges are optimised. The control of the generator is carried out, depending on the determined charge status and optionally the ambient temperature, whereby either a set value for the charging voltage is given at a normal charging level, a set value for charging voltage is given for relieving the load on the engine, a set value for the charging voltage is given at a reduced vehicle electrical system level or a set value for the charging voltage is given at a recuperative level.

Description

DaimlerChrysler AG

Method and device for battery status detection

The invention relates to a method and a device for battery state detection.

Different approaches for evaluating or assessing the starter battery in a vehicle are conventionally known. These are used to ensure that the battery is sufficiently charged and generally use an expensive and susceptible, faulty current sensor.

From EP 0 071 816 AI a method and a device for measuring the state of charge of a motor vehicle battery is known, in which the battery voltage is measured under load. The starter current is applied to the battery while the engine is starting. In this time phase (approx. 10 seconds) the battery voltage is measured and fed to an evaluation circuit. The evaluation circuit generates a current pulse with a constant amplitude, the length of which is a function of the battery terminal voltage. The current pulse is placed in a memory device that stores the amount of charge. Furthermore, a shunt resistance measures charging or discharging currents which occur during the loading of the battery and which are supplied to the storage component with the correct sign. Adding the stored currents results in a control signal which, after falling below a certain limit value, provides a switching element for the automatic start and stop of the vehicle and / or an optical display device (LED) actuated for the user to inform him about the state of charge of his battery.

However, it is problematic that when starting in the morning, e.g. after a cold winter night, the starting current is significantly higher and thus the terminal voltage is much lower, so that due to the morning start, the starting limit voltage is reached or almost reached. In this case, a reliable statement about the state of charge is only possible if the vehicle has already been driving for some time and the engine has reached a certain operating temperature, so that a relatively steady state is reached.

Furthermore, from DE 41 06 725 AI a circuit arrangement for displaying the state of charge of a rechargeable battery is proposed, in which the state of charge of the battery is determined by integrating the current flowing in the load circuit. By taking into account various correction factors such as inrush current, temperature, offset and self-discharge of the battery, there is reproducible accuracy for the state of charge. A difference to at least one limit value of the battery voltage can be output on a display as the state of charge of the battery.

However, an expensive and susceptible, faulty current sensor is required for this state of charge assessment.

It is therefore an object of the present invention to develop a method and a device for battery state detection for which a susceptible current sensor is not required and which enables a reliable assessment of the state of charge independent of a temperature and operating time of a vehicle.

According to the invention, this object is achieved by a method having the features of claim 1 and an apparatus with the Features solved according to claim 13. Advantageous developments of the invention are specified in the subclaims.

By dispensing with the current sensor according to the invention, simple and inexpensive battery status detection is made possible, which also uses the control of the generator for improved battery charging and for measures to optimize consumption and emissions of the entire vehicle. In addition, since the temperature can optionally be used as an additional assessment parameter, the battery status detection according to the invention is able to carry out a reliable assessment without incorrect assessments due to very low temperatures.

These and other objects, features and advantages of the present invention will become apparent from the following description of a preferred embodiment in conjunction with the drawing.

Show:

1 is a block diagram of a basic electrical system structure according to the invention,

2 shows a voltage curve at the start including various state of charge assessments,

3 shows a flowchart of the method according to the invention for battery state detection and

4 shows a flowchart of a modification of the method according to the invention for battery state detection.

According to the invention, a simple solution with voltage measurement is used to achieve fuel savings and emission reductions in that the total electrical energy requirement of the vehicle electrical system and the battery is then determined by the generator. rator is produced when the internal combustion engine is optimized for consumption and emissions and the battery is sufficiently charged. The conventional current detection is dispensed with. Due to the high-frequency detection of the voltage and implicitly stored information about the vehicle, the battery state is assessed according to the invention based on the voltage behavior in defined situations, for example starting process, brief switching on of defined consumers in operation, brief switching off of the generator, etc., and different consumption and Emission-optimal control and regulation strategies of the generator are derived and tracked during driving.

1 shows a block diagram of the basic electrical system structure according to the invention. Reference number 1 denotes a consumer (SLP), 2 an internal combustion engine, 3 a switching device, 4 a generator, 5 a (vehicle) battery, 6 an on-board electrical system, 7 an engine control unit (MSG) and 8 a voltage measuring device. The switching device 3 is switched via an actuator control unit (not shown) contained in the engine control unit 7. The measurement signal of the voltage measuring device 8 is fed to the engine control unit 7, which outputs control signals for the generator 4.

In addition, an optional temperature measuring device 9, shown in dashed lines, can be designed for measuring the outside temperature, the output signals of which are also fed to the engine control unit 7. Alternatively, the output signal of a temperature measuring device already present in the vehicle, which is part of the air conditioning system, for example, can be fed to the engine control unit 7.

The engine control unit 7 has a device for determining the minimum level of the voltage signal supplied by the voltage measuring device 8 during a predetermined period of time, and a device for evaluating the state of charge of the vehicle battery 5 on the basis of the direction for determining the minimum level determined minimum voltage level. The device for evaluating the state of charge evaluates the depth of the voltage dip in comparison to the output voltage present, for example, before a starting process, on the basis of the minimum level determined during the measurement period. The voltage range in which such a drop in the voltage level can occur is divided into at least two, preferably three, voltage ranges in which the state of charge of the battery is "very efficient" (BZ1) with a very low voltage drop,

"Efficient" (BZ2) in the event of a major voltage drop, in which, however, the cold start capability is still guaranteed, and "limited performance" (BZ3) in the case of a very large voltage drop in which, for example, a

(further) cold start is no longer possible without restrictions, is assessed. FIG. 2 shows a voltage curve at the start, including various state of charge assessments.

During a cold start, the vehicle conditions are almost constant, but there is always a drop in level during the starting process. In addition to the battery charge level, battery aging and the ambient temperature also affect the depth of the level dip.

Depending on this state of charge determined by the device for evaluating the state of charge, ie "very powerful" (BZ1), "powerful" (BZ2) or "limited performance" (BZ3) by itself or in connection with another parameter, for example the temperature , various measures - bundled in packages of measures - are taken to achieve optimal battery charging and optimized consumption and emission values. For this purpose, a setpoint of the charging voltage and its duration is assigned to the generator 4 by means of a device for controlling the generator, the setpoint being either a normal charge level, a setpoint for engine relief, a reduced vehicle electrical system level or a recuperation level, depending on how good or bad the state of charge was rated, ie whether charging the vehicle battery is necessary or not. The exact assignment of the respective setpoints to the assessed states of charge is explained in more detail in the explanation below of the method according to the invention. Here it is omitted to avoid repetitions.

The method according to the invention for battery state detection is now explained in more detail below with reference to FIG. 3. In the method according to the invention for battery state detection for a motor vehicle, in step 1 a voltage of a battery 5 is first measured by a voltage measuring device 8 over a predetermined period of time. This predetermined period of time can be, for example, 5 seconds or more. In step 2, a minimum voltage level of the battery 5 is determined from the output signal of the voltage measuring device over the predetermined period of time by a device (not shown) contained in the engine control unit for determining a minimum level. This minimum voltage level is then evaluated in step 3 with steps S3-1 to S3-3 by a device for evaluating the state of charge of the battery 5, which is also contained in the engine control unit 7, the state of charge at a minimum voltage level above a first threshold value VI being " very powerful "(BZ1) (step S3-1), between the first threshold VI and a second threshold V2, which is lower than the first threshold VI, as" powerful "(BZ2) (step S3-2) and below the second threshold value V2 is rated as "limited performance" (BZ3) (step S3-3). This utilization result is then transmitted to the engine control unit 7 and this adjusts the activation of the generator 4 in step 4 in accordance with the assessment result of the state of charge. The first threshold value VI can be, for example, between approximately 7 to 8 V and the second threshold value V2 is between approximately 6 to 7 V.

The control of the generator 4 by the engine control unit 7 takes place in the present exemplary embodiment of the invention depending on the evaluation result of the state of charge by the device for evaluating the state of charge as follows:

Step ^" S4 -3:

If the battery status has been rated as having limited capacity (BZ3), the setpoint of the charging voltage is set to a normal charging level indefinitely. In this case, no fuel or emission savings are possible, since the state of charge of the battery 5 must be improved to ensure problem-free and reliable operation of the vehicle.

Step S4-2:

If the state of charge has been rated as efficient (BZ2), the nominal value of the charging voltage is set to a value for motor relief and then to the normal charging level. This time-limited period is a dead time.

In this way, the good state of charge of the battery is used to reduce the energy requirements of the vehicle for as long as is possible without impairing the performance of the battery, thereby reducing fuel consumption and emissions.

Step S4-1:

If the state of charge has been rated as very efficient (BZ1), the nominal value of the charging voltage, for example 12V, is monitored for the value to relieve the engine, then for a period specified by the battery used to a reduced on-board electrical system level, for example 12V, and then to a recuperation level , for example 15V. In this way, the state of charge, which is rated as very efficient (BZ1), can be used to reduce consumption and emissions, since the total electrical energy requirement is reduced due to the lack of a need to recharge the battery.

The method for battery status detection according to the invention can thus easily identify the battery status and control the generator accordingly, so that fuel consumption and emissions can be significantly reduced.

In a further development of the exemplary embodiment of the method according to the invention described below, which is shown in FIG. 4, the outside temperature is used as a further parameter, as a result of which a further optimization of consumption and emissions and an even better evaluation of the state of charge is possible Further development of the above exemplary embodiment distinguishes, for example, between three temperature ranges Tl to T3, which are defined by two temperature threshold values Tsl and Ts2, where, for example, Tsl = 0 ° C and Ts2 = 25 ° C and thus Tl: T <Tsl, T2: Tsl ≤ T <Ts2 and T3: Ts2 ≤ T.

In principle, steps 1 to 4 described above are also carried out in the development of the method for battery state detection according to the invention. However, the evaluation of the state of charge carried out in step 3 and the adaptation of the control of the generator 4 carried out by the engine control unit 7 are modified.

The modified control of the generator 4 according to the development of the invention takes place as follows depending on the evaluation result of the state of charge and the temperature recorded: 1) If the measured temperature T is in the temperature range Tl, ie below the first temperature threshold Tsl (step S3-0), regardless of the battery state and in the temperature ranges T2 and T3, ie at a temperature T greater than the first temperature threshold Tsl limited capacity of the battery (BZ3) (step S3-3 *) the setpoint of the charging voltage is set to a normal charging level indefinitely (step S4-3).

In this case, it is not possible to save fuel or emissions, since the vehicle battery needs to be recharged again.

2) If the measured temperature T is above the first temperature threshold Tsl (step S3-0) and the state of charge has been rated as efficient (BZ2)

(Step S3-2 *), the nominal value of the charging voltage is limited in time (for example until a minimum voltage is undershot) to a value for motor relief and then to the normal charging level (Step S4-2).

3) If the measured temperature T is between the first temperature threshold Tsl (step S3-0) and the second temperature threshold Ts2 and the state of charge has been rated as very efficient (BZ1) (step S3-1 *), the target value of the charging voltage is limited in time

(for example until a minimum voltage is undershot) is set to the value for engine relief, then to a reduced on-board electrical system level (for example 13V) and then to a recuperation level (for example 15V) (step S4-1).

In this way, the state of charge, which is rated as very efficient (BZ1), can be used to reduce consumption and emissions, since the total electrical energy requirement is reduced due to the lack of a need to recharge the battery.

4) If the temperature T is above the second temperature threshold Ts2 and the state of charge is very performance (BZ1) was evaluated (step S3-3 *), the target value of the charging voltage is set to the normal charging level indefinitely (step S4-3).

Optionally, an additional step S5 can be formed both in the method according to FIG. 3 and in the method according to FIG. 4, in which the evaluation result is optically displayed to the user. This can be done, for example, when using three charge state ranges in the form of traffic light colors, green being "very efficient" for the optimal state and red "having limited capacity" for the worst state of charge. In this case, a display device (not shown), for example in the form of three differently colored LEDs (green, yellow, red), is additionally formed in the device according to the invention according to FIG. 1, which displays the result of the device (7) for evaluating the state of charge is fed. Of course, other display and / or display types and devices can also be used for this information.

It is thus possible with the method according to the invention for battery state detection and the associated device for battery state detection to reduce the fuel consumption and the emissions depending on the battery state of charge and still ensure an adequate battery state of charge at all times.

In summary, the invention discloses a method and a device for battery state detection. The battery state is determined by measuring the voltage of a motor vehicle battery during the starting process over a predetermined period of time, determining a minimum voltage level of the motor vehicle battery during the predetermined period of the measuring process, evaluating the state of charge of the vehicle battery based on the minimum voltage level and controlling the generator depending on the evaluation the state of charge of the motor vehicle battery, so that an adequate supply of the On-board electrical system and a sufficient charge of the vehicle battery is guaranteed and at the same time the fuel consumption and emissions are optimized. The generator is controlled depending on the determined state of charge and optionally the ambient temperature by specifying either a setpoint of the charge voltage at normal charge level, a setpoint of charge voltage to relieve the engine, a setpoint of charge voltage at a reduced electrical system level or a setpoint of charge voltage at recuperation level.

Claims

DaimlerChrysler AG patent claims

1. A method for battery state detection for a motor vehicle, with the steps

(51) measuring a voltage of a motor vehicle battery (5) during the starting process of a motor vehicle over a predetermined period of time,

(52) determining a minimum voltage level of the motor vehicle battery (5) during the predetermined period of the measurement process,

(S3-1 to S3-3; S3-0 to S3-3 *) evaluating a state of charge of the motor vehicle battery (5) on the basis of the determined minimum voltage level,

(S4-1 to S4-3) controlling a generator depending on the evaluation of the state of charge of the motor vehicle battery (5), so that an adequate supply of the vehicle electrical system and a sufficient charge of the motor vehicle battery (5) is guaranteed and at the same time optimizes fuel consumption and emissions becomes.

2. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that

(S5) the result of the evaluation is output to a vehicle user.

3. The method according to claim 1 or 2, characterized in that the assessment of the state of charge in step S3-1 to S3-3 is carried out by assigning the minimum voltage level to one of at least two predetermined state of charge ranges.

4. The method according to claim 3, so that three predetermined state of charge ranges (BZ1, BZ2, BZ3) are formed, which are defined by two threshold values (VI, V2).

5. The method according to claim 3, so that the three predetermined state of charge ranges comprise the state of charge "very efficient" (BZ1), "efficient" (BZ2) and "restrictedly efficient" (BZ3).

6. The method according to any one of claims 2 to 5, that the result of the evaluation is optically output in step S5.

7. The method according to claim 5, characterized in that the result of the evaluation in step S5 takes place optically in the form of different colors for the three charge states "limited performance" (BZ3), "performance" (BZ2) and "very performance" (BZ1) ,

8. The method according to any one of claims 1 to 7, characterized in that in step S4-3 the generator (4) with a state of charge "limited performance" (BZ3) a target value of the charging voltage to a normal charging level is given indefinitely, in step S4-2 the generator (4) is given a target value of the charging voltage for motor relief and then the target value of the charging voltage is set to the normal charging level for a predetermined period of time when the charging state is "powerful" (BZ2), in step S4-1 the generator ( 4) in the case of a "very efficient" state of charge (BZ1), the target value of the charging voltage is set to the value for engine relief, then to a reduced vehicle electrical system level and then to a recuperation level over a predetermined period of time.

9. The method according to any one of claims 1 to 7, characterized in that the control of the generator in steps S4-1 to S4-3 depending on the evaluation of the state of charge of the motor vehicle battery (5) and at least one further parameter in steps S3-0 to S3-3 * takes place in order to ensure a sufficient charge of the motor vehicle battery (5) and at the same time to optimize fuel consumption and emissions.

10. The method according to claim 9, so that the at least one further parameter is the ambient temperature (T).

11. The method according to claim 10, characterized in that in step S4-3 the generator (4) regardless of the assessed state of charge at a temperature below a first temperature threshold (Tsl) (step S3-0) and in a state of charge "limited performance" (BZ3 ) (Step S3-3 *) a setpoint of the charging voltage on normal charging level is specified, in step S4-2 the generator (4) with a charge state "efficient" (BZ2) (step S3-2 *) and a temperature above the first temperature threshold value (Tsl) (step S3-0) over a predetermined period of time a target value of the charging voltage for motor relief and then the target value of the charging voltage at normal charging level is specified in step S4-1 the generator (4) with a "very powerful" state of charge (BZ1) (step S3-1 *) and a temperature above the first temperature threshold value (Tsl) (step S3-0) and below a second temperature threshold value (Ts2) (step S3-1 *) for a predetermined period of time the target value of the charging voltage for engine relief, then for a predetermined period of time a target value of the charging voltage on reduced vehicle electrical system Level and then a target value of the charging voltage at the recuperation level is specified and in step S4-3 the generator (4) with a charge state "very powerful" (BZ1) and one Temperature above the second temperature threshold (Ts2) (step 3-3 *) the target value of the charging voltage at normal charging level is specified for an unlimited time.

12. Method according to claim 11, so that the first temperature threshold (Tsl) is 0 ° C and the second temperature threshold (Ts2) is 25 ° C.

13. Device for battery status detection for a motor vehicle, comprising: a device (8) for measuring a voltage of a motor vehicle battery (5) during the starting process of a motor vehicle over a predetermined period of time, a device (7) for determining a minimum level of the motor vehicle battery (5) during the predetermined period of the measurement process, a device (7) for evaluating a state of charge of the motor vehicle battery (5) on the basis of the determined minimum voltage level and a device (7) for controlling a generator (4) depending on the evaluation of the state of charge of the motor vehicle battery (5), such that a sufficient Supply of the vehicle electrical system and an adequate charge of the motor vehicle battery (5) is guaranteed and at the same time the fuel consumption and the emission emissions are optimized.

14. The apparatus as claimed in claim 13, so that a display device is formed on which a vehicle user is shown the state of charge determined by the device (7) for evaluating the state of charge of the motor vehicle battery (5) in different colors for each state of charge.

15. The apparatus of claim 13 or 14, d a d u r c h g e k e n n z e i c h n e t that the device (7) for controlling the generator (4)

- the generator (4) with a state of charge "limited performance" (BZ3) specifies a target value of the charging voltage to a normal charging level indefinitely,

- The generator (4) at a charge state "powerful" (BZ2) over a predetermined period of a setpoint

Charging voltage for motor relief and then specifies the target value of the charging voltage to the normal charging level,

- The generator (4) with a state of charge "very powerful" (BZ1) over a predetermined period of time the target value of the charging voltage to the value for engine relief, then to a reduced vehicle electrical system level and then to a recuperation level.

16. The apparatus of claim 13 or 14, so that a device (9) for measuring the ambient temperature is additionally formed, the measurement result of which is taken into account by the device (7) for controlling the generator (4) in addition to the result of the evaluation of the state of charge.

17. The apparatus of claim 16, d a d u r c h g e k e n n z e i c h n e t that the device (7) for controlling the generator

- the generator, regardless of the assessed state of charge at a temperature below a first temperature threshold (Tsl) and in a state of charge "limited performance" (BZ3), regardless of the temperature, a setpoint of the charging voltage at normal charging level indefinitely,

- the generator with a state of charge "powerful" (BZ2) and a temperature above the first temperature threshold (Tsl) over a predetermined period of time a target value of the charging voltage for engine relief and then the target value of the charging voltage at normal charging level,

- The generator with a state of charge "very powerful" (BZ1) and a temperature above the first temperature threshold (Tsl) and below a second temperature threshold (Ts2) for a predetermined period of time the target value of the charging voltage for engine relief, then a target value for a predetermined period Charging voltage to a reduced on-board electrical system level and then a target value of the charging voltage at recuperation level and

- The generator with a state of charge "very powerful" (BZ1) and a temperature above the second temperature threshold (Ts2) sets the target value of the charging voltage at normal charging level indefinitely.