WO2015088425A1 - Electrical system for motor vehicles and method for voltage regulation of such - Google Patents

Electrical system for motor vehicles and method for voltage regulation of such Download PDF

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Publication number
WO2015088425A1
WO2015088425A1 PCT/SE2014/051442 SE2014051442W WO2015088425A1 WO 2015088425 A1 WO2015088425 A1 WO 2015088425A1 SE 2014051442 W SE2014051442 W SE 2014051442W WO 2015088425 A1 WO2015088425 A1 WO 2015088425A1
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WO
WIPO (PCT)
Prior art keywords
starting battery
battery
value
starting
current
Prior art date
Application number
PCT/SE2014/051442
Other languages
French (fr)
Inventor
Gunnar Ledfelt
Ninos Poli
Original Assignee
Scania Cv Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Scania Cv Ab filed Critical Scania Cv Ab
Priority to EP14870037.0A priority Critical patent/EP3080893A4/en
Publication of WO2015088425A1 publication Critical patent/WO2015088425A1/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/14—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from dynamo-electric generators driven at varying speed, e.g. on vehicle
    • H02J7/1423—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from dynamo-electric generators driven at varying speed, e.g. on vehicle with multiple batteries
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R16/00—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for
    • B60R16/02—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements
    • B60R16/03—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for supply of electrical power to vehicle subsystems or for
    • B60R16/033—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for supply of electrical power to vehicle subsystems or for characterised by the use of electrical cells or batteries
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
    • F02N11/00—Starting of engines by means of electric motors
    • F02N11/08—Circuits or control means specially adapted for starting of engines
    • F02N11/0862—Circuits or control means specially adapted for starting of engines characterised by the electrical power supply means, e.g. battery
    • F02N11/0866—Circuits or control means specially adapted for starting of engines characterised by the electrical power supply means, e.g. battery comprising several power sources, e.g. battery and capacitor or two batteries
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
    • H02J7/0031—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits using battery or load disconnect circuits
    • H02J7/0032—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits using battery or load disconnect circuits disconnection of loads if battery is not under charge, e.g. in vehicle if engine is not running
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2310/00—The network for supplying or distributing electric power characterised by its spatial reach or by the load
    • H02J2310/40—The network being an on-board power network, i.e. within a vehicle
    • H02J2310/46—The network being an on-board power network, i.e. within a vehicle for ICE-powered road vehicles
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

Definitions

  • the present invention relates to an electrical system configured to be part of a motor vehicle and comprising
  • a generator and electrical energy consumers comprising a starter motor connected between opposite poles of the power battery on a consumer side thereof which is opposite to the power battery's side for connection to the starting battery, - a breaker situated between the starting battery and one pole of the power battery to make it possible to disconnect the starting battery from said consumer side and to be open for said disconnection when the vehicle's engine is switched off, and
  • the invention is not confined to any particular type of motor vehicle, although it is particularly applicable on wheel- mounted motor vehicles, especially utility vehicles such as trucks and buses, and for this reason it will at times be discussed below in this use with a view to illustrating but in no way limiting the invention .
  • An electrical system of this type is usually called a dual-battery system because it comprises two battery packs connected in parallel , comprising a pack of service batteries serving as power batteries and a pack of starting batteries.
  • Each such pack might respectively comprise only one power battery and one starting battery, although they usually each comprise two or more batteries connected in series, such as usually two 1 2V batteries connected in series on board trucks.
  • the purpose of the starting batteries is to ensure that the starter motor is provided with sufficient power via current from the starting battery to start the vehicle's combustion engine even in situations where the power batteries of the electrical system are completely discharged. For this reason it is important to maintain a high state of charge of the starting batteries irrespective of the state of charge of the power batteries.
  • the starting battery is situated on the opposite side of the power battery relative to the generator and the vehicle's electrical energy consumers and that a breaker is provided between the starting battery and one pole of the power battery.
  • An electrical system of the kind defined in the introduction is for example known previously from EP 1 093974 B1 , which is mainly concerned with how the starting battery might be recharged in an advantageous way on the basis of various parameters of the electrical system.
  • the object of the present invention is to propose an electrical system and a method of the kind defined in the introduction which are improved in at least some respects relative to previously known electrical systems and methods.
  • the electrical system comprises a means configured to measure the time during which the current through said breaker is in a given direction , and the arrangement is configured to cause the breaker to open when, after completion of engine start procedure, current has continuously flowed in said path from the starting battery towards said consumer side for a specified ti me, e.g. at least 1 0 seconds.
  • ti me e.g. at least 1 0 seconds.
  • the electrical system comprises a unit configured to respond to the occurrence of a current which after completion of engine start procedure flows continuously in said path from the starting battery towards said consu mer side by calculating the time integral of the current, and the arrangement is configured to cause said breaker to open when said time integral of the current exceeds a predetermined level such as 0.1 Ah.
  • the electrical system comprises a device configured to calculate, after completion of engine start procedure, a value for the degree of charge of the starting battery and to compare this value with a value which corresponds to starting battery fully charged , and the arrangement is configured to cause said breaker to open at a value of the degree of charge of the starting battery calculated by this device which corresponds to the starting battery being regarded as fully charged. It is thus assured that the starting battery will be separated from the consumer side of the power battery when there is no longer any need to charge the starting battery.
  • said device is configured, when calculating a value for the degree of charge of the starting battery, to find that the starting battery is to be regarded as fully charged if the current measured by said means in said path from the consumer side towards the starting battery during a predetermined period of ti me, e.g. at least five minutes, is below a predetermined level such as 0.2 A.
  • a predetermined period of ti me e.g. at least five minutes
  • said device is configured, when calculating a value for the degree of charge of the starting battery, to compare the rate at which a current measured by said means in said path from the consumer side towards the starting battery drops at a predetermined value for this rate, such as 0.1 A/h, and to regard the starting battery as fully charged when said rate is below said value predetermined for it.
  • the electrical system comprises a means configured, after completion of engine start procedure, to determine the temperature of the power battery, means configured to use the temperature value determined as a basis for calculating a set-point value for the voltage across the power battery, a device configured to calculate a value of the degree of charge of the starting battery and compare this value with a value which corresponds to starting battery fully charged, a means configured to measure the voltage across the power battery and a means configured to compare the calculated voltage set-point value with said measured voltage and, if said breaker is open and the result of the comparison is that the starting battery is not to be regarded as fully charged, to close the breakers if said measured voltage is substantially equal to said voltage set-point value, meaning that it is at least 95% or at least 98% of the voltage set-point value.
  • the starting battery can be charged as soon as the conditions so allow, i .e. when the power battery has been recharged by the generator to a voltage of substantially the same level as the voltage set-point value, thereby meeting the requirements for charging the starting battery.
  • the invention relates also to a computer programme with features according to clai m 1 3, a computer programme product with features according to claim 1 4, an electronic control unit with features according to claim 1 5 and a motor vehicle with features according to claim 1 6.
  • Fig. 1 illustrates very schematically an electrical system according to an embodiment of the invention
  • Fig. 2 is a diagram illustrating a possible trend of the charging current for a starting battery during the ti me after completion of a motor vehicle's engine start procedure
  • Fig. 3 is a diagram of the load on an electrical system according to the invention and the current between the starting battery and a consu mer side of the power battery of the electrical system over time to illustrate various embodi ments of the invention
  • Fig. 4 is a flowchart illustrating a method according to an embodiment of the invention .
  • Fig. 5 is a schematic diagram of an electronic control unit for i mplementing a method according to the invention .
  • Fig. 1 illustrates very schematically the general structure of an electrical system according to the invention intended to be part of a schematically indicated motor vehicle 1 and comprising two power or service batteries 2 connected in series and two starting batteries 3 thus connected in parallel on one side.
  • the batteries are for example 1 2V batteries, so that the operating voltage between the two poles 4, 5 of the power battery will normally be about 24V.
  • a generator 7, a starter motor 8 and an electronic control unit 9 for control of components of the electrical system are connected on a consumer side 6 of the power batteries. It should be noted that numerous undepicted components of the vehicle which require electricity supply are connected to the electrical system on the consumer side 6 of the power batteries 2.
  • the electrical system further comprises a breaker 1 0 which , via an arrangement 1 1 in the form of a circuit card, is operable via two signals Si , S 2 , represented by broken lines, from relays, the signal S ! being intended to arise from the operating of an ignition key or the like of the vehicle for starting the latter's engine and then , via the arrangement 1 1 , to cause the breaker 1 0 to close in order to provide a path for current between the starting batteries 3 and the consumer side of the power batteries, and hence current to the starter motor 8.
  • the other signal S 2 arises from the electronic control unit 9 and also operates the breaker. When either of the signals S ! and S 2 calls for closure of the breaker, the latter will be closed via the arrangement 1 1 .
  • the system also comprises schematically indicated means 1 2 configured to measure the current through the breaker 1 0 and means 1 3 configured to measure the time during which the current through the breaker is in a given direction.
  • a means 1 4 is provided to measure the voltage between the two poles 4, 5 of the power battery package, and another means 1 5 is configured to determine the temperature of the power batteries. This may be done by direct or indirect measurement and calculation of the temperature.
  • Means 1 2 and means 1 3- 1 5 are configured to send the information on to the electronic control unit 9 for production of appropriate relay signals S 2 .
  • the electronic control unit comprises for this purpose a unit 1 6 configured to respond to the occurrence of a current which after completion of engine start procedure flows continuously in the path from the starting battery towards the consumer side 6 by calculating the time integral of the current, and a device 1 7 configured to calculate, after completion of engine start procedure, a value for the degree of charge of the starting battery and to compare this value with a value which corresponds to starting battery fully charged.
  • Fig. 2 illustrates a possible trend of the current I which flows in said path over ti me t after completion of an engine start procedure, in order to recharge the starting batteries 3, and said device 1 7 may be configured to find that the starting batteries are to be regarded as fully charged if the current measured by means 1 2 in said path during a predetermined period of time, e.g. at least five minutes, is below a predetermined level , e.g. 0.2 A, represented by the chain-dotted line A in Fig . 2.
  • a predetermined level e.g. 0.2 A
  • Fig. 3 illustrates schematically how the electrical system according to the invention behaves as regards operating the breaker 1 0 in response to different operating conditions of the electrical system .
  • a line a represents the trend of the load on the electrical system's consumer side over ti me t, and the broken line G denotes the maxi mum current which the generator 7 can generate.
  • the current in the path between the starting batteries 3 and the consu mer side 6 of the power battery, i .e. the current through the breaker 1 0, is represented by I .
  • An engine start takes place at time t 0 and the arrangement 1 1 then causes the breaker 1 0 to close in order to activate the starter motor 8, thereby partly discharging the starting batteries and causing a current I to flow from the power battery's consumer side to the starting batteries in order to charge these latter.
  • the load on the electrical system quite suddenly becomes for a very short time greater than the generator can generate, meaning that current will also flow from the starting batteries to supply the electrical system's consumers as a result of the breaker 1 0 being closed.
  • the time integral of this "wrong direction" current in said path will nevertheless not reach a predetermined level at which the arrangement 1 1 would cause the breaker 1 0 to open, so charging of the starting batteries 3 will continue once the very short load peak has passed.
  • the voltage measured via the means 1 4 is compared with a voltage set-point value calculated on the basis of the information about the temperature of the power batteries, and when the comparison shows that the voltage across the power batteries has reached substantially the same level as said set-point value the arrangement 1 1 will cause the breaker 1 0 to close again , which takes place at time t 5 . The charging of the starting batteries will thus continue.
  • Fig. 4 depicts a flowchart illustrating a method according to an embodiment of the invention for voltage regulation of an electrical system according to the invention , in which a first step S ! demands starter motor activation. As a result of this demand the starting battery is connected to the consumer side of the power battery at step S 2 . The starter motor is then activated at step S 3 , the question arises at step S 4 as to whether the engine start procedure has been completed, and if the answer is yes the method moves on to step S 5 of measuring the current which flows between the starting battery and the consumer side of the power battery. But if the answer to the question is no, the question is put again.
  • the questions which arise at step S 6 are 1 ) whether the starting battery has been discharged to a predetermined extent since the engine start procedure was completed or 2) whether the starting battery is fully charged, and if the answer to either of these questions raised at step S 6 is yes, then at step S 7 the starting battery is disconnected from the power battery's consumer side to protect the starting battery against further discharge. If the answer to both of the questions put at step S 6 is no, the starting battery will remain connected to the power battery's consumer side.
  • Computer programme code for implementing a method according to the invention is with advantage included in a computer programme which can be read into the internal memory of a computer, e.g. the internal memory of an electronic control unit of a vehicle.
  • a computer programme is with advantage provided via a computer programme product comprising a data storage medium which can be read by an electronic control unit, which medium is permanent, i .e. non-transitory, and has the computer programme stored on it.
  • Said data storage medium is for example an optical data storage maxim m in the form of a CD ROM disc, a DVD disc etc. , a magnetic data storage maxim m in the form of a hard disc, a diskette, a cassette tape etc. , or a flash memory or a memory of the ROM , PROM , EP ROM or E EPROM type.
  • Fig. 5 illustrates very schematically an electronic control unit 9 comprising an execution facility 1 8, e.g. a central processor unit (CPU) , for execution of computer software.
  • the execution facility 1 8 communicates with a memory 1 9, e.g. of the RAM type, via a data bus 20.
  • the control unit 9 comprises also a data storage medium 21 , e.g . in the form of a flash memory or a memory of the ROM , PROM , EPROM or EEP ROM type.
  • the execution facility 1 8 communicates with the data storage medium 21 via the data bus 20.
  • a computer programme comprising computer programme code for implementing a method according to the invention , e.g. in accordance with the embodiment illustrated in Fig. 4, is stored on the data storage maxim m 21 .

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • General Engineering & Computer Science (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)

Abstract

An electrical system in a motor vehicle (1) comprises a power battery (2), a starting battery (3) connected in parallel therewith, a generator (7) and electrical energy consumers comprising a starter motor (8) connected between opposite poles (4, 5) of the power battery. A breaker ( 10) is provided between the starting battery (3) and one pole (4) of the power breaker. An arrangement (11) is configured to cause the breaker (10) to close upon activation of the starter motor (8). Means (12) are configured to measure the current through the breaker, and the arrangement (11) is configured, after completion of engine start procedure, to cause the breaker (10) to open as soon as a condition which relates to a certain degree of discharge of the starting battery having taken place after the completion of the engine start procedure is fulfilled.

Description

ELECTRICAL SYSTEM FOR MOTOR VEHICLES AND METHOD FOR VOLTAGE REGULATION OF SUCH
FI ELD OF TH E I NVENTION
The present invention relates to an electrical system configured to be part of a motor vehicle and comprising
a power battery,
a starting battery connected in parallel with the power battery,
a generator and electrical energy consumers comprising a starter motor connected between opposite poles of the power battery on a consumer side thereof which is opposite to the power battery's side for connection to the starting battery, - a breaker situated between the starting battery and one pole of the power battery to make it possible to disconnect the starting battery from said consumer side and to be open for said disconnection when the vehicle's engine is switched off, and
- an arrangement configured for control of the breaker and to cause the breaker to close upon activation of the starter motor for starting of the vehicle's engine, in order to provide a path for current between the starting battery and the consu mer side of the power battery, and hence current to the starter motor, and
to a method for voltage regulation of an electrical system according to the preamble of the attached independent method claim . In this context the invention is not confined to any particular type of motor vehicle, although it is particularly applicable on wheel- mounted motor vehicles, especially utility vehicles such as trucks and buses, and for this reason it will at times be discussed below in this use with a view to illustrating but in no way limiting the invention .
An electrical system of this type is usually called a dual-battery system because it comprises two battery packs connected in parallel , comprising a pack of service batteries serving as power batteries and a pack of starting batteries. Each such pack might respectively comprise only one power battery and one starting battery, although they usually each comprise two or more batteries connected in series, such as usually two 1 2V batteries connected in series on board trucks. The purpose of the starting batteries is to ensure that the starter motor is provided with sufficient power via current from the starting battery to start the vehicle's combustion engine even in situations where the power batteries of the electrical system are completely discharged. For this reason it is important to maintain a high state of charge of the starting batteries irrespective of the state of charge of the power batteries. It is for this reason that in such an electrical system the starting battery is situated on the opposite side of the power battery relative to the generator and the vehicle's electrical energy consumers and that a breaker is provided between the starting battery and one pole of the power battery. This makes it possible for the starting battery to be disconnected from said consumer side, i .e. from the rest of the electrical system , at times when the vehicle's engine is switched off, and for it subsequently to be connected to the electrical system at the ti me of the next start. Since during such a start the starting battery will be partly discharged, it is also important to ensure that it regains charge, which can be achieved by keeping it connected to said consu mer side and hence to the generator for recharging via the generator before the starting battery is separated from the rest of the system by opening of said breaker.
STATE OF TH E ART
An electrical system of the kind defined in the introduction is for example known previously from EP 1 093974 B1 , which is mainly concerned with how the starting battery might be recharged in an advantageous way on the basis of various parameters of the electrical system.
SUMMARY OF TH E I NVENTION
The object of the present invention is to propose an electrical system and a method of the kind defined in the introduction which are improved in at least some respects relative to previously known electrical systems and methods.
This object is achieved as regards the electrical system by providing such an electrical system with the features enu merated in the characterising part of claim 1 .
After completion of engine start procedure, when the breaker is closed and the starting battery is connected to the consu mer side of the power battery and hence to the generator for possible recharging of the starting battery, it is possible, by measuring the current through the breaker and opening the breaker as soon as a condition is fulfilled which relates to a certain degree of discharge of the starting battery having taken place after the completion of the engine procedure, for the starting battery to be effectively protected against a dangerous discharge which might otherwise take place if the electrical system is for any reason subjected by said consumers, after starting of the vehicle, to offtake of a higher electrical power than the generator can deliver. In contrast, if said condition is not fulfilled, i .e. if no such degree of discharge has taken place after completion of the engine start procedure, the breaker may then be closed to allow desired recharging of the starting battery. In one embodiment of the invention the electrical system comprises a means configured to measure the time during which the current through said breaker is in a given direction , and the arrangement is configured to cause the breaker to open when, after completion of engine start procedure, current has continuously flowed in said path from the starting battery towards said consumer side for a specified ti me, e.g. at least 1 0 seconds. The condition of current having to flow in the "wrong" direction in said path continuously, i .e. without stopping , being fulfilled before the breaker opens to protect the starting battery prevents its opening as a result of any kind of momentary fluctuation, e.g . a voltage peak, in some parameter of the electrical system. Recharging of the starting battery may thus continue despite such a momentary fluctuation . In another embodiment of the invention the electrical system comprises a unit configured to respond to the occurrence of a current which after completion of engine start procedure flows continuously in said path from the starting battery towards said consu mer side by calculating the time integral of the current, and the arrangement is configured to cause said breaker to open when said time integral of the current exceeds a predetermined level such as 0.1 Ah. Applying such a condition for interruption of the path between the starting battery and the consumer side of the power battery makes it possible, after completion of engine start procedure, to have said breaker remain closed even if the current through it does for a short time flow in the "wrong" direction or even does so for a longer time but is weak. It can still be guaranteed that the starting battery is maximally discharged with a charge which corresponds to said predetermined level .
In another embodiment of the invention the electrical system comprises a device configured to calculate, after completion of engine start procedure, a value for the degree of charge of the starting battery and to compare this value with a value which corresponds to starting battery fully charged , and the arrangement is configured to cause said breaker to open at a value of the degree of charge of the starting battery calculated by this device which corresponds to the starting battery being regarded as fully charged. It is thus assured that the starting battery will be separated from the consumer side of the power battery when there is no longer any need to charge the starting battery. In a further development of the last-mentioned embodiment, said device is configured, when calculating a value for the degree of charge of the starting battery, to find that the starting battery is to be regarded as fully charged if the current measured by said means in said path from the consumer side towards the starting battery during a predetermined period of ti me, e.g. at least five minutes, is below a predetermined level such as 0.2 A. When the charging current has dropped to such a value, it may be appropriate to separate the starting battery from the consu mer side of the power battery.
In another embodiment of the invention said device is configured, when calculating a value for the degree of charge of the starting battery, to compare the rate at which a current measured by said means in said path from the consumer side towards the starting battery drops at a predetermined value for this rate, such as 0.1 A/h, and to regard the starting battery as fully charged when said rate is below said value predetermined for it. In another embodiment of the invention the electrical system comprises a means configured, after completion of engine start procedure, to determine the temperature of the power battery, means configured to use the temperature value determined as a basis for calculating a set-point value for the voltage across the power battery, a device configured to calculate a value of the degree of charge of the starting battery and compare this value with a value which corresponds to starting battery fully charged, a means configured to measure the voltage across the power battery and a means configured to compare the calculated voltage set-point value with said measured voltage and, if said breaker is open and the result of the comparison is that the starting battery is not to be regarded as fully charged, to close the breakers if said measured voltage is substantially equal to said voltage set-point value, meaning that it is at least 95% or at least 98% of the voltage set-point value. It is thus ensured that, after the breaker has opened to prevent risk of the starting battery being discharged too much because of such a large load on the electrical system that the generator cannot cope alone, and of the voltage across the power battery consequently dropping, the starting battery can be charged as soon as the conditions so allow, i .e. when the power battery has been recharged by the generator to a voltage of substantially the same level as the voltage set-point value, thereby meeting the requirements for charging the starting battery.
The object of the invention as regards the method is achieved by employing a method according to the independent method claim. The advantages of this and of the methods according to the embodiments cited in the dependent method claims are indicated by the above description of the electrical system according to the invention.
The invention relates also to a computer programme with features according to clai m 1 3, a computer programme product with features according to claim 1 4, an electronic control unit with features according to claim 1 5 and a motor vehicle with features according to claim 1 6.
Further advantages and advantageous features of the invention are indicated by the description set out below. BRI EF DESCRI PTION OF TH E DRAWI NGS
Embodiments of the invention cited as examples are described below with reference to the attached drawings, in which
Fig. 1 illustrates very schematically an electrical system according to an embodiment of the invention, Fig. 2 is a diagram illustrating a possible trend of the charging current for a starting battery during the ti me after completion of a motor vehicle's engine start procedure, Fig. 3 is a diagram of the load on an electrical system according to the invention and the current between the starting battery and a consu mer side of the power battery of the electrical system over time to illustrate various embodi ments of the invention ,
Fig. 4 is a flowchart illustrating a method according to an embodiment of the invention , and
Fig. 5 is a schematic diagram of an electronic control unit for i mplementing a method according to the invention .
DETAI LED DESCRI PTION OF EMBODI M ENTS OF TH E I NVENTION Fig. 1 illustrates very schematically the general structure of an electrical system according to the invention intended to be part of a schematically indicated motor vehicle 1 and comprising two power or service batteries 2 connected in series and two starting batteries 3 thus connected in parallel on one side. The batteries are for example 1 2V batteries, so that the operating voltage between the two poles 4, 5 of the power battery will normally be about 24V. A generator 7, a starter motor 8 and an electronic control unit 9 for control of components of the electrical system are connected on a consumer side 6 of the power batteries. It should be noted that numerous undepicted components of the vehicle which require electricity supply are connected to the electrical system on the consumer side 6 of the power batteries 2.
The electrical system further comprises a breaker 1 0 which , via an arrangement 1 1 in the form of a circuit card, is operable via two signals Si , S2, represented by broken lines, from relays, the signal S! being intended to arise from the operating of an ignition key or the like of the vehicle for starting the latter's engine and then , via the arrangement 1 1 , to cause the breaker 1 0 to close in order to provide a path for current between the starting batteries 3 and the consumer side of the power batteries, and hence current to the starter motor 8. The other signal S2 arises from the electronic control unit 9 and also operates the breaker. When either of the signals S! and S2 calls for closure of the breaker, the latter will be closed via the arrangement 1 1 . The system also comprises schematically indicated means 1 2 configured to measure the current through the breaker 1 0 and means 1 3 configured to measure the time during which the current through the breaker is in a given direction. A means 1 4 is provided to measure the voltage between the two poles 4, 5 of the power battery package, and another means 1 5 is configured to determine the temperature of the power batteries. This may be done by direct or indirect measurement and calculation of the temperature. Means 1 2 and means 1 3- 1 5 are configured to send the information on to the electronic control unit 9 for production of appropriate relay signals S2. The electronic control unit comprises for this purpose a unit 1 6 configured to respond to the occurrence of a current which after completion of engine start procedure flows continuously in the path from the starting battery towards the consumer side 6 by calculating the time integral of the current, and a device 1 7 configured to calculate, after completion of engine start procedure, a value for the degree of charge of the starting battery and to compare this value with a value which corresponds to starting battery fully charged.
Fig. 2 illustrates a possible trend of the current I which flows in said path over ti me t after completion of an engine start procedure, in order to recharge the starting batteries 3, and said device 1 7 may be configured to find that the starting batteries are to be regarded as fully charged if the current measured by means 1 2 in said path during a predetermined period of time, e.g. at least five minutes, is below a predetermined level , e.g. 0.2 A, represented by the chain-dotted line A in Fig . 2. This might then mean that the arrangement 1 1 receives a signal to cause the breaker 1 0 to open and thereby disconnect the starting batteries 3 from the consumer side 6 so that they can be kept fully charged until the next ti me an engine start is to take place.
Fig. 3 illustrates schematically how the electrical system according to the invention behaves as regards operating the breaker 1 0 in response to different operating conditions of the electrical system . A line a represents the trend of the load on the electrical system's consumer side over ti me t, and the broken line G denotes the maxi mum current which the generator 7 can generate. The current in the path between the starting batteries 3 and the consu mer side 6 of the power battery, i .e. the current through the breaker 1 0, is represented by I .
An engine start takes place at time t0 and the arrangement 1 1 then causes the breaker 1 0 to close in order to activate the starter motor 8, thereby partly discharging the starting batteries and causing a current I to flow from the power battery's consumer side to the starting batteries in order to charge these latter. At time ^ the load on the electrical system quite suddenly becomes for a very short time greater than the generator can generate, meaning that current will also flow from the starting batteries to supply the electrical system's consumers as a result of the breaker 1 0 being closed. The time integral of this "wrong direction" current in said path will nevertheless not reach a predetermined level at which the arrangement 1 1 would cause the breaker 1 0 to open, so charging of the starting batteries 3 will continue once the very short load peak has passed.
At time t2 an "overload" of the electrical system again occurs, this time with a significantly longer load peak L2, and when said ti me integral of the current I in the wrong direction in the path reaches said predetermined level the arrangement 1 1 will cause the breaker 1 0 to open, which takes place at ti me t3. At time t4 the load from the electrical system's consu mers drops back below the G which the generator can deliver and the generator then begins charging the power batteries which during the time between t3 and t4 have helped the generator by delivering electrical energy to the consumers. The voltage measured via the means 1 4 is compared with a voltage set-point value calculated on the basis of the information about the temperature of the power batteries, and when the comparison shows that the voltage across the power batteries has reached substantially the same level as said set-point value the arrangement 1 1 will cause the breaker 1 0 to close again , which takes place at time t5. The charging of the starting batteries will thus continue. At time t6 a further load peak L3 occurs but only insignificantly exceeds the level which the generator can itself cope with, so there will be a small discharge of the starting batteries but the time integral of the current between times t6 and t7 will be below a predetermined level , so the breaker will remain closed and charging of the starting batteries will continue after time t7 before being ended at time t8 by the arrangement 1 1 causing the breaker 1 0 to open because the current I has during a predetermined period of ti me been below a certain value. After time t8 the breaker 1 0 will then remain open until another engine start is to take place.
Fig. 4 depicts a flowchart illustrating a method according to an embodiment of the invention for voltage regulation of an electrical system according to the invention , in which a first step S! demands starter motor activation. As a result of this demand the starting battery is connected to the consumer side of the power battery at step S2. The starter motor is then activated at step S3, the question arises at step S4 as to whether the engine start procedure has been completed, and if the answer is yes the method moves on to step S5 of measuring the current which flows between the starting battery and the consumer side of the power battery. But if the answer to the question is no, the question is put again. The questions which arise at step S6 are 1 ) whether the starting battery has been discharged to a predetermined extent since the engine start procedure was completed or 2) whether the starting battery is fully charged, and if the answer to either of these questions raised at step S6 is yes, then at step S7 the starting battery is disconnected from the power battery's consumer side to protect the starting battery against further discharge. If the answer to both of the questions put at step S6 is no, the starting battery will remain connected to the power battery's consumer side.
Computer programme code for implementing a method according to the invention is with advantage included in a computer programme which can be read into the internal memory of a computer, e.g. the internal memory of an electronic control unit of a vehicle. Such a computer programme is with advantage provided via a computer programme product comprising a data storage medium which can be read by an electronic control unit, which medium is permanent, i .e. non-transitory, and has the computer programme stored on it. Said data storage medium is for example an optical data storage mediu m in the form of a CD ROM disc, a DVD disc etc. , a magnetic data storage mediu m in the form of a hard disc, a diskette, a cassette tape etc. , or a flash memory or a memory of the ROM , PROM , EP ROM or E EPROM type.
Fig. 5 illustrates very schematically an electronic control unit 9 comprising an execution facility 1 8, e.g. a central processor unit (CPU) , for execution of computer software. The execution facility 1 8 communicates with a memory 1 9, e.g. of the RAM type, via a data bus 20. The control unit 9 comprises also a data storage medium 21 , e.g . in the form of a flash memory or a memory of the ROM , PROM , EPROM or EEP ROM type. The execution facility 1 8 communicates with the data storage medium 21 via the data bus 20. A computer programme comprising computer programme code for implementing a method according to the invention , e.g. in accordance with the embodiment illustrated in Fig. 4, is stored on the data storage mediu m 21 .
The invention is of course in no way restricted to the embodiments described above, as nu merous possibilities for modifications thereof are likely to be obvious to one skilled in the art without thereby deviating from the invention's scope such as defined in the attached claims.

Claims

An electrical system configured to be part of a motor vehicle (1 ) and comprising :
- a power battery (2) ,
- a starting battery (3) connected in parallel with the power battery,
- a generator (7) and electrical energy consumers comprising a starter motor (8) connected between opposite poles (4, 5) of the power battery on a consumer side (6) thereof which is opposite to the power battery's side for connection to the starting battery,
- a breaker ( 1 0) situated between the starting battery (3) and one pole of the power battery to make it possible to disconnect the starting battery from said consumer side (6) and to be open for said disconnection when the vehicle's engine is switched off , and
- an arrangement (1 1 ) configured for control of breaker and for causing the breaker (1 0) to close upon activation of the starter motor (8) for starting of the vehicle's engine, in order to provide a path for current between the starting battery and the consumer side (6) of the power battery, and hence current to the starter motor, and
characterised in that it also comprises means (1 2) configured to measure the current through said breaker (1 0) , and that the arrangement (1 1 ) is configured, after completion of engine start procedure, to cause the breaker to open as soon as a condition which relates to a certain degree of discharge of the starting battery (3) having taken place after the completion of the engine start procedure is fulfilled.
An electrical system according to claim 1 , characterised in that it comprises a means (1 3) configured to measure the time during which the current through said breaker (1 0) is in a given direction , and that the arrangement (1 1 ) is configured to cause the breaker to open when, after completion of engine start procedure, current has continuously flowed in said path from the starting battery (3) towards said consu mer side (6) for a specified time, e.g. at least 1 0 seconds.
An electrical system according to claim 1 , characterised in that it also comprises a unit (1 6) configured to respond to the occurrence of a current which after completion of engine start procedure flows continuously in said path from the starting battery (3) towards said consumer side (6) by calculating the time integral of the current, and that the arrangement (1 1 ) is configured to cause said breaker ( 1 0) to open when said time integral of the current exceeds a predetermined level such as 0.1 Ah.
An electrical system according to any one of the foregoing claims, characterised in that it comprises a device ( 1 7) configured to calculate, after completion of engine start procedure, a value for the degree of charge of the starting battery (3) and to compare this value with a value which corresponds to starting battery fully charged, and that the arrangement ( 1 1 ) is configured to cause said breaker ( 1 0) to open at a value of the degree of charge of the starting battery (3) calculated by this device which corresponds to the starting battery being regarded as fully charged.
An electrical system according to claim 4, characterised in that said device (1 7) is configured, when calculating a value for the degree of charge of the starting battery (3) , to find that the starting battery is to be regarded as fully charged if the current measured by said means (1 2) in said path from the consu mer side towards the starting battery during a predetermined period of time, e.g . at least five minutes, is below a predetermined level such as 0.2 A. 6. An electrical system according to claim 4, characterised in that said device (1 7) is configured, when calculating a value for the degree of charge of the starting battery (3) , to compare the rate at which a current measured by said means (1 2) in said path from the consumer side (6) towards the starting battery (3) drops at a predetermined value for this rate, such as 0.1 A/h, and to regard the starting battery as fully charged when said rate is below said value predetermined for it. 7. An electrical system according to any one of the foregoing claims, characterised in that it also comprises a means ( 1 5) configured, after completion of engine start procedure, to determine the temperature of the power battery (2) , means configured to use the temperature value determined as a basis for calculating a set-point value for the voltage across the power battery, a device (1 7) configured to calculate a value for the degree of charge of the starting battery (3) and compare this value with a value which corresponds to starting battery fully charged, a means (1 4) configured to measure the voltage across the power battery (2) and a means configured to compare the calculated voltage set- point value with said measured voltage and, if said breaker (1 0) is open and the result of the comparison is that the starting battery (3) is not to be regarded as fully charged, to close the breaker if said measured voltage is substantially equal to said voltage set-point value, meaning that it is at least 95% or at least 98% of the voltage set-point value.
A method for voltage regulation of an electrical system configured to be part of a motor vehicle (1 ) and comprising a power battery (2) , a starting battery (3) connected in parallel with the power battery, a generator (7) and electrical energy consumers comprising a starter motor (8) connected between opposite poles (4, 5) of the power battery on a consumer side (6) thereof which is opposite to the power battery's side for connection to the starting battery,
which starting battery (3) is kept disconnected from said consumer side (6) of the power battery (2) when the vehicle's engine is switched off, by a path for current between the starting battery and the consumer side of the power battery being kept broken and said path being closed upon activation of the starter motor (8) to start the vehicle's engine,
characterised in that it comprises the steps of
- measuring the current in said path, and - breaking said path as soon, after completion of engine start procedure, as a condition which relates to a certain degree of discharge of the starting battery (3) having taken place after the completion of the engine start procedure is fulfilled .
A method according to claim 8, characterised in that it comprises the steps of
- measuring the time during which the current in said path is in a given direction, and
- breaking said path when, after completion of engine start procedure, the current has continuously flowed in said path from the starting battery (3) towards said consu mer side (6) for a specified time, e.g . 1 0 seconds.
A method according to claim 8, characterised in that it comprises the steps of
- responding to the occurrence of a current which, after completion of engine start procedure, continuously flows in said path from the starting battery (3) towards said consumer side (6) by calculating the time integral of the current, and
- breaking said path when said time integral of the current exceeds a predetermined level , e.g. 0.1 Ah .
A method according to any one of claims 8- 1 0, characterised in that it comprises the steps of - calculating, after completion of engine start procedure, a value for the degree of charge of the starting battery (3) ,
- comparing the calculated value with a value which corresponds to starting battery fully charged, and
- breaking said path at a calculated value for the degree of charge of the starting battery (3) which corresponds to the starting battery being regarded as fully charged .
A method according to any one of claims 8- 1 1 , characterised in that it comprises the steps of
- determining, after completion of engine start procedure, the temperature of the power battery (2) ,
- calculating a set-point value for the voltage across the power battery on the basis of the measured temperature value,
- calculating a value for the degree of charge of the starting battery (3) and comparing this value with a value which corresponds to starting battery fully charged,
- measuring the voltage across the power battery (2) ,
- comparing the calculated voltage set-point value with said measured voltage, and
- closing said path if it is broken , the starting battery (3) as a result of said comparison is not to be regarded as fully charged and said measured voltage is substantially equal to said voltage set-point value, meaning that it is at least 95% or at least 98% of the voltage set-point value. A computer programme which is loadable directly into the internal memory of a computer and which comprises computer programme code for causing a computer to conduct steps according to any one of clai ms 8- 1 2 when said programme is run on the computer.
A computer programme product comprising a permanent data storage mediu m which can be read by a computer and on which the programme code of a computer programme according to claim 1 3 is stored .
An electronic control unit for voltage regulation of an electrical system configured to be part of a motor vehicle (1 ) comprising an execution facility (1 8) , a memory (1 9) connected to the execution facility and a permanent data storage mediu m (21 ) which is connected to the execution facility and on which programme code of a computer programme according to claim 1 3 is stored.
A motor vehicle characterised in that it is provided with an electrical system according to any one of claims 1 -7 and/or an electronic control unit (9) according to claim 1 5.
PCT/SE2014/051442 2013-12-13 2014-12-03 Electrical system for motor vehicles and method for voltage regulation of such WO2015088425A1 (en)

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SE1351493A SE537877C2 (en) 2013-12-13 2013-12-13 Dual battery system for motor vehicles and method of voltage regulation of such

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SE537877C2 (en) 2015-11-10
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EP3080893A4 (en) 2017-10-04

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