DE102006001201B4 - Method for controlling a battery charging operation - Google Patents

Abstract

method for controlling a battery charging operation of a battery (1) of a Motor vehicle with by controlling a generator (2) existing Rekuperationsphasen for the conversion of kinetic energy of the motor vehicle in electrical energy and for recuperation of braking energy, wherein a SOC level (state of charge) of the battery (1) within two Limits is maintained and an SOC target level is given as well the while a recuperation phase flowing Amount of charge to the battery (1) to one or more of the preceding Rekuperationsphasen is adjusted, where shortly before a Rekuperationsladung the Braking behavior monitored and from this a charging strategy is determined, for which a short-term Charge measurement is carried out, characterized in that the SOC target level adapted to the flow of charge so flowed through a braking process That is, if a previous braking operation is a high amount of charge has revealed the charge amount of a present Rekuperationsphase less fails and vice versa.

Description

The The invention relates to a method for controlling a battery charging process a battery of a motor vehicle with the in the preamble of Claim 1 specified characteristics.

In Motor vehicles become batteries for electrical energy storage used. They are charged by the generator while the engine is running and provide electrical power when the engine is off. They provide energy to start the engine or deliver while the engine is running Engine additional Energy, when many consumers, such as light, rear window heating and more consumers are turned on.

Around extend the life of the battery, methods are known which prevent overcharging the battery is done. This does not exhaust the full storage capacity of the battery (100%), but stops the battery as possible between two limits, well below 100%. The charge status The battery is the so-called SOC (State of charge).

Also Methods are known which by generator control practically a Energy recovery allow braking energy. The kinetic energy of the vehicle is converted by the generator into electrical energy that is stored by the battery. These methods have the advantage that one Fuel savings in internal combustion engines up to 2% is possible.

in this connection the problem occurs that one preferably high fuel economy at the expense of battery life. For many braking operations would be an overload the battery easily possible. Would you To keep the SOC very low in order to prevent the above overload would be the Danger that no sufficient energy to start the internal combustion engine available would.

From the DE 101 53 509 A1 a method for controlling the battery charging operation of a battery of a motor vehicle is known. The motor vehicle is designed as a hybrid vehicle. In this solution, it is provided that the battery is charged via regenerative braking, wherein the state of charge of the battery, for example, must be below a predetermined value, which still allows the charging of the battery by the operation of the starter / generator as a generator. The engine is kept running as the battery charge may be too low to restart the engine when it is shut down. A control unit monitors the state of charge. If the state of charge is below predetermined values for various hybrid modes of charging, regenerative braking, or engine start-up, the controller allows the battery to be charged. If the state of charge is above predetermined values, the controller allows the battery to reduce the state of charge for both a discharge mode and a hybrid mode. An SOC manager for monitoring the state of charge is also provided. The purpose of this SOC manager is to prevent the state of charge of the battery from being excessively high.

A such solution is only for Hybrid vehicles and for designed different hybrid modes.

For example, a technique in which an SOC level can be changed between 50% and 70% is described in Scripture US 6,344,732 B2 , This method is intended to provide a reduction in the required battery size in a hybrid vehicle. The basis is a speed information. If a low speed of the vehicle is detected over a set period of time, a prediction is made that the vehicle will accelerate or stop in the future. A control unit in this case controls the charging or discharging of the battery, wherein a detection of the accelerator pedal position of the vehicle takes place and the vehicle speed is detected. Although this method should make it possible to use a smaller battery, fuel economy is neither intended nor achieved.

Another method for charging a battery for hybrid vehicles is from the WO 01/73919 A1 known. In some cases, the SOC value should rise to 80% and 90% without damaging the gasification effects of the vehicle battery. This is to optimize the SOC value, whereby the highest possible charge capacity is to be achieved. It does not increase the life of the battery or save fuel. Rather, the battery life is significantly reduced by the high SOC value.

According to the preamble of claim 1 underlying publication DE 100 46 631 A1 It is proposed to lower the generator voltage during acceleration in order to relieve the vehicle engine and to increase the generator voltage when braking, so that the generator for charging the battery by recuperation of braking energy can absorb more power.

A technical solution with the one hand, a Rekuperationsbetrieb and on the other hand, an increase in battery life is to be possible, is in the DE 100 46 631 A1 proposed. This is to be done by a mode of operation, the consequences of the stress of the battery by Rekupe partially reversing the ration. This is explained by a frequent change between discharging and charging of the battery. Therefore, a recovery mode is provided. As a recuperation characteristic, a charge flow rate through the battery is utilized, namely, from a switching point between the recovery mode and a recuperation standby mode. For this purpose, in the case of regenerative braking shortly before a recuperation charge, the braking behavior is monitored and used to determine a charging strategy, for which purpose a short-term charge measurement takes place. A given charge range is 60% to 80% of a full charge.

basis for one Setpoint voltage forms a so-called base value of the generator voltage. This Value corresponds to the battery return voltage in a partial charge operation, the for the recuperation operation is desired. Depending on the actual State of charge SOC, of the temperature of the battery and of an accelerator pedal position this base generator voltage is corrected downwards. The SOC level is at this solution dependent from the battery temperature and the accelerator pedal position. A high fuel economy, without lowering the battery life, however, is with this Procedure not possible.

Of the Invention has for its object to find a method that a very high fuel economy, without the lifetime to reduce the battery.

These Task is solved by that the SOC target level adapted to the flow of charge so flowed through a braking process That is, if a previous braking operation is a high amount of charge has revealed the amount of charge of the present Rekuperationsphase less fails and vice versa.

By This measure is it more surprising Way possible, save more than 2% fuel and even up to 5% fuel.

The On the one hand, the invention is based on the knowledge that an exact Control the SOC (State of charge) level of the battery is. By only a few, especially only the last preceding one Recuperation phase as a yardstick for the allowed for amount of charge allowed is an accurate SOC control and thus high fuel economy possible. An error of already 5% at the SOC level can be an already achieved fuel saving destroy it. In known methods can easily SOC error of 5-10% enter. The invention minimizes the SOC error.

By The invention can therefore a possible high percentage of braking energy are stored.

The On the other hand, the invention is also based on the knowledge that the creation a uniform charge balance is important for recuperation. In that during a Recuperation phase a fluid Amount of charge to the battery of the previous recuperation phase adjusted, results in an optimal charging strategy. It will the battery in the short term only so much energy through recuperation admitted, as by a favorable SOC level is allowed.

It In practice, the braking behavior is monitored shortly before a recuperative charge and from this the charging strategy is determined. A short-term current measurement or charge measurement bears this claim.

The inventive method takes a different approach than other solutions (e.g., 100 46 631 A1). It is essential that the State of charge (SOC) is to be adapted to the flowed charging currents while the previous Rekuperationsphase (s), so that the highest possible proportion of braking energy can be stored. In contrast, in the prior art between Recreation mode and recuperation mode switched.

In an advantageous embodiment of the method according to the invention, is provided that during a Recuperation phase flowing Charge quantity to the battery only at the last, preceding recuperation phase is adjusted. An adaptation means, if already a last one Braking a high charge amount has revealed that the amount of charge the present Rekuperationsphase correspondingly lower precipitates and reversed (adapted). The capture of the last by recuperation Flowed charge quantity can be done with simple means and is easy to work with.

Especially It is advantageous if a control is carried out so that the immediate After a Rekuperationsphase from the battery effluent charge equal to the amount of charge received in the recuperation phase is. Thus, a balanced charge balance is always created, which is a very accurate SOC compliance allowed. This greatly increases the life of the battery.

One optimal compromise between service life extension and fuel economy when implementing the solution according to the invention, when the SOC level is kept between about 60-70%.

Around a practical solution it's cheap to get that one Controlled by a battery management system with one battery status detecting monitoring device and one with the monitoring device connected generator and recuperation phase control takes place, wherein the battery status of the generator control passed as an input parameter becomes. Such procedures have been proven in similar methods and can by the method according to the invention be easily modified by, for example, another programming and or parameterization takes place. Such systems are in fact made Hardware and software. This measure requires one low to no hardware change.

One Another preferred embodiment of the invention is characterized from that the Generator and recuperation phase control further input parameters, such as at least one vehicle status, accelerator pedal status and / or a Brake pedal status processed. In particular, the detection of vehicle pedal positions is easily e.g. above suitable sensors and over Buses (e.g., CAN bus) feasible. A safe generator control results when the generator and Rekuperationsphasen control as the output parameter comprises an excitation voltage of the generator. By change the excitation voltage is a rapid change in the charging current possible.

The inventive method is particularly useful for motor vehicles with internal combustion engines and a single 12V battery. The 12V battery (Standard battery voltage) is used to crank the engine and to the electrical system supply, but not to the actual vehicle drive, as in hybrid vehicles.

In order to no sudden change the vehicle electrical system voltage is to be remembered or thus a disturbing erratic change the vehicle lighting, changes from fan movements and The like is avoided, it is advantageous if the generator voltage while the Rekuperationsphasen is regulated so that the voltage changes follow the generator voltage of a ramp function. This creates a smooth transition or a gentle change the electrical system voltage, so that a Recuperation phase goes virtually unnoticed.

Further advantageous embodiments of the invention are characterized in the subclaims.

One embodiment becomes closer on the basis of the drawings explains wherein further advantageous developments of the invention and advantages are described the same.

It demonstrate:

1 a block diagram of a generator control according to the invention,

2 a schematic representation of a charge window in a COC process,

3 a current diagram with recuperation phases,

4 an SOC diagram with recuperation phases,

5 a current and voltage diagram as a function of the SOC, and

6 a voltage diagram as a function of time.

1 , shows a block diagram of a generator controller for implementing a method according to the invention for controlling a battery charging operation of a battery 1 a motor vehicle. A generator 2 , which is mechanically coupled to an internal combustion engine, powers the battery 1 and / or an electrical system 3 of the motor vehicle with electrical energy, through power or power cable 4 and 5 ,

With the battery 1 is electrically a battery management system comprising a monitoring device 6 connected. This monitors the battery current and battery voltage U. In addition, it can monitor other quantities such as battery temperature T. The battery management system 6 is to a recuperation phase control 7 connected and provides a battery status. The system 6 determines the charging strategy of the battery 1 , The recuperation phase control 7 controls the generator 2 and determines its operating point, so that, for example, a higher voltage than the battery voltage is supplied, so that the battery 1 is charged or so that a not higher voltage is delivered, so that it runs virtually empty. The recuperation phase control 7 also includes conventional control functions that are outside the actual recuperation function. In particular, the vehicle status, an accelerator pedal and / or brake pedal position and preferably also other characteristic parameters serve as input parameters.

By this arrangement is a control of the generator 2 or control of Rekuperationsphasen for the conversion of kinetic energy of the motor vehicle into electrical energy and the recuperation of braking energy possible. If there is no braking and the battery is sufficiently charged, the generator voltage is low and the generator does not load the internal combustion engine. In a braking operation, the generator voltage is increased according to the charging strategy, wherein a charging current through the battery 1 flows and the internal combustion engine with a torque of the generator 2 is loaded so that the desired braking energy conversion occurs.

As in 2 is illustrated, a SOC level (state of charge) of the battery is maintained within two limits. An SOC target level is specified according to the specified charging strategy. There is practically an SOC window in which the battery 1 to operate. The SOC window is monitored by the monitoring device 6 certainly.

The SOC level or the SOC window is 60-70%. This avoids a full battery condition and possible overcharging, resulting in a long battery life 1 ensures. Also, too low a charge of the battery 1 avoided. A low-charged battery could namely ensure no starting operation of the internal combustion engine.

3 illustrates the battery current in connection with Rekuperationsphasen or braking processes and recovery of braking energy.

According to the invention, the amount of charge flowing to the battery during a recuperation phase is adapted to one or more of the preceding recuperation phases by adapting the setpoint SOC level to the flow rate that has flowed. At the in 3 As shown, the amount of charge is adjusted to the previous recuperation phase.

The first current rectangle with a positive current profile represents a first recuperation phase in which a brake pedal is preferably actuated. As in 4 is shown, the SOC or ΔSOC changes ramped upward. The battery 1 is charged and the kinetic energy of the engine or the vehicle withdrawn, resulting in an additional deceleration of the vehicle. This process not only saves fuel but also spares existing brake systems. After the first recuperation phase shown here, the battery is discharged, for example, to supply a connected to the electrical system consumers, such as vehicle lighting or the like, which is based on the first negative current rectangle in 3 or by the associated falling ramp in 4 you can see. The battery discharge corresponds to the charge obtained during recuperation. The generator control takes place in such a way that the amount of charge flowing out of the battery immediately after a recuperation phase is equal to the charge quantity supplied in the recuperation phase.

Of the Charge current, however, is e.g. higher as the discharge current, so that the Battery is discharged slower than that it is charged. Here was the charge current is about twice as high as the discharge current.

This is followed by a rest phase of the battery, in which the ΔSOC is kept constant. An on-board power supply is exclusively via the generator 2 ,

Since the first braking operation was relatively long and / or relatively intense, according to the invention, the second in 3 and 4 shown recuperation phase adapted to the first. The second current pulse is therefore lower than the first. Thus, the ΔSOC changes less due to the second recuperation phase, which is due to the lower peak height of the second triangle in FIG 4 you can see. However, the battery discharge can be greater than its Rekuperationsladung. The battery may have a longer discharge time, such as 3 illustrated. Analogously, it is also possible to allow a higher supply current for the electrical system. In this case could be a mixed feed of battery 1 and generator 2 be provided. Analogously, depending on the intended strategy, a smaller discharge can take place, so that the SOC level of the battery is raised.

A change The SOC level is achieved according to the invention by the SOC target level at the flowed Charging current is adjusted.

By this procedure will change the charging cycle behavior of the battery and thus improving the battery life.

5 shows the battery voltage U and, by way of example, the battery current I during a recuperation phase as a function of the SOC level in%. At a very low SOC level of, for example, 50%, which is below the tolerated limit of 60%, a very high charging current of, for example, 50 A is permitted. At the beginning of such a charging process, the battery voltage is low, eg 12 V. At the upper SOC limit of 70%, the charging current is considerably lower and at 100% even only a few A. Charging current I and battery voltage are preferably linear functions of the SOC level ,

It is very advantageous that a balanced charge balance takes place, so that the SOC level is kept constant before and after a drive cycle. In particular, the short-term charge balance consideration is important. Also, it is beneficial if the outside temperature in the battery management system 6 and thus influence the generator control. On cold days, it is beneficial to increase the SOC level. Also long downtimes eg a 30-day parking time can be considered accordingly. For vehicles that are usually idle for longer, the SOC level can also be increased. The battery management system 6 also records these or other variables and determines the charging strategy accordingly. The charging or discharging strategy can be achieved by changing the excitation voltage of the generator 2 be implemented.

6 shows an example in which the generator voltage is controlled during the Rekuperationphasen so that the voltage changes of the generator voltage follow a ramp function. At the beginning of the first recuperation phase, a rising voltage ramp A begins. At the end of the recuperation phase, a falling voltage ramp B begins, wherein preferably the slopes of the rising ramp A and the descending ramp B are approximately equal. Points C and D mark the beginning and the end of the recuperation phase. The reference E denotes the maximum voltage. The reference character F indicates the target value at which the battery 1 supplies the electrical system.

The voltage setpoint of the generator after a recuperation phase with respect to the voltage setpoint before the beginning of a recuperation phase as a function of the SOC setpoint level to be changed is variable. Thus, the voltage before the recuperation phase (SOC, eg 70%) is higher than afterwards, as in 6 you can see.

By the ramp-shaped Changes will be Flakererscheinungen, such as Lichtflachern, and / or noise avoided.

When Battery in the sense of this description is also a similar one electrical energy storage, such as a supercapacitor or the like, consider.

1

battery

2

generator

3

board network

4

power cables

5

power cable

6

Battery management system

7

Rekuperationsphasensteuerung

Claims (12)

Method for controlling a battery charging operation of a battery ( 1 ) of a motor vehicle by controlling a generator ( 2 ) existing Rekuperationsphasen for converting kinetic energy of the motor vehicle into electrical energy and for recuperation of braking energy, wherein a SOC level (State of charge) of the battery ( 1 ) is kept within two limits and an SOC target level is specified and the amount of charge flowing to the battery during a recuperation phase ( 1 ) is adapted to one or more of the preceding Rekuperationsphasen, being monitored shortly before a Rekuperationsladung the braking behavior and from a charging strategy is set, for which a short-term charge measurement is carried out, characterized in that the SOC target level of the flow rate flowed through such a braking operation is adapted that when a previous braking operation has resulted in a high amount of charge, the charge amount of a present Rekuperationsphase lower and vice versa. Method according to Claim 1, characterized in that the amount of charge flowing during a recuperation phase to the battery ( 1 ) is adapted only to the last, preceding recuperation phase. A method according to claim 1, characterized in that a control is carried out so that the immediately after a Rekuperationsphase from the battery ( 1 ) is equal to the amount of charge flowed in the recuperation phase. Method according to claim 1 or 2, characterized that the SOC level between about 60-70% is held. Method according to one of the preceding claims, characterized in that a control by a battery management system ( 6 ) with a battery status monitoring device and with the battery management system ( 6 ) generator and recuperation phase control ( 7 ), wherein the battery status is passed to the generator controller as an input parameter. Method according to claim 5, characterized in that the generator and recuperation phase control ( 7 ) processes further input parameters, such as at least one vehicle status, accelerator pedal status, and / or a brake pedal status. Method according to claim 6 or 7, characterized in that the connected generator and recuperation phase control ( 7 ) comprises as output parameter an exciter voltage of the generator. Method according to one of the preceding Claims characterized by an application to a 12V battery. Method according to one of the preceding claims, characterized by applying to a battery charging operation with a coupled with an internal combustion engine generator. Method according to one of the preceding claims, characterized characterized in that Generator voltage during the Rekuperationsphasen is regulated so that the voltage changes follow the generator voltage of a ramp function. Method according to claim 10, characterized in that that too Beginning of a recuperation phase a rising voltage ramp begins and at the end of the recuperation phase a declining voltage ramp begins, preferably the slopes of the rising ramp and the sloping ramp are about the same. Method according to claim 10, characterized in that that the Voltage setpoint of the generator after a recuperation phase with respect to Voltage setpoint before the beginning of a recuperation phase depending on the SOC target level to be changed variable is.