SE543020C2 - Method and arrangement for heating a high voltage battery for a vehicle - Google Patents

lO Method and arrangement for heating a high voltage battery for a vehicle TECHNICAL FIELD The present invention relates to a method for heating a high voltage battery for a vehicle. Theinvention also relates to an arrangement for heating a high voltage battery for a vehicle. Theinvention also relates to a vehicle. Further, the invention relates to a computer program and a computer program product adapted to implement the method.

BACKGROUND Electrically powered vehicles and hybrid vehicles powered by electricity in combination withsome form of fuel are equipped with at least One high voltage battery for storage of electricalenergy. In general, batteries peiforms poorly at cold temperatures. Specially, coldtemperatures affect battery chemistry and increase electrical resistance within the battery. Asa result the capacity of a battery to store energy and the maximum value of discharge currentwhich can be drawn from a battery decreases substantially. Cold temperatures may also decrease the life of a battery and therefore increase its replacement frequency.

Current methods of Operating high voltage batteries at low temperatures employ means forheating the high voltage battery by a heater adapted to be activated by the vehicle°s lowvoltage electrical system. A problem with such a method is that it is only possible to run theheater when the vehicle is in operation, i.e. when the ignition is switched on. When thevehicle is not in operation and the ignition is switched off the electrical system is normallyshut off and the heater is therefore disconnected. When such a vehicle is started the highvoltage battery may be at a temperature below its optimal Operating temperature and it maytake some time for the high voltage battery to reach its optimal Operating temperature, causingthe high voltage battery to run less efficiently. Improvements in the field of heating high voltage batteries are therefore desirable. lO SUMMARY An object of the present invention is to address and at least alleviate the above mentionedproblems. A further object is to make it possible to activate the heater when the vehicle is notin operation, i.e. when the ignition is switch off. A further object is to preheat a high voltagebattery to a more battery-friendly temperature. A further object is to retard high voltage battery ageing at cold temperatures.

In accordance with the present invention there is provided a method for heating a high voltagebattery for a vehicle comprising an electrical circuit, a battery heater adapted to heat the highvoltage battery, a SLI (Starter Lightning Ignition) battery and a heater switch arranged forconnecting and disconnecting the battery heater to/from power received from the batterycharger. The method comprises the steps of connecting the electrical circuit to an extemalsource of electric energy, detecting an establishment of the connection of the electrical circuitto the external source of electric energy, emitting an activating signal, deterrnining if a valuefor the charging status of the SLI battery is equal to or above a predetermined value,determining if a temperature of the high voltage battery is equal to or below a predeterminedvalue and activating the battery heater when the value for the charging status of the SLIbattery is equal to or above the predetermined value and the temperature of the high voltagebattery is equal to or below the predetermined value. This makes it possible to determinewhether the high voltage battery should be heated or not and thereby only heating the high voltage battery when needed.

According to an optional aspect of the invention the method comprises the step of stoppingthe battery heater if the temperature of the high voltage battery is above the predeterminedvalue. Hereby it is possible to only heat the high voltage battery when heating is necessary and that the heating is stopped when no longer needed.

According to an optional aspect of the invention the method comprises the step of the driver/operator of the vehicle being able to enforce starting or stopping high voltage battery lO heating. Hereby it is possible for the driver/operator of the vehicle to take over the control of the heating of the high voltage battery.

According to an optional aspect of the invention the method comprises the step of controllingthe heater switch based on inforrnation from a detecting device. The advantages of the methodappears from the above discussion of the arrangement according to the invention and different embodiments thereof.

In accordance with the present invention there is also an arrangement provided for heating ahigh voltage battery for a vehicle. The arrangement comprises an electrical circuit, a batteryheater adapted to heat the high voltage battery, a SLI (Starter Lightning Ignition) battery and aheater switch arranged for connecting and disconnecting the battery heater to/from powerreceived from the SLI battery. Further the arrangement comprises a detecting deviceconnected to the electrical circuit, which detecting device comprises means adapted to detectan establishment of a connection of the electrical circuit to an external source of electricenergy and adapted to activate the battery heater when the electrical circuit is connected to theexternal source of electric energy. The detecting device may be adapted to emit informationwhen connected to the external source of electric energy. The information may comprise asignal, such as a wake up signal or a trigger signal, which may be adapted to activate thebattery heater despite of the vehicle being not in operation i.e. when the ignition is switchedoff. This makes it possible to preheat the high voltage battery to a more battery-friendlytemperature before starting the vehicle, causing the high voltage battery to run more efficiently when started and thereby retard battery aging at cold temperatures.

According to an optional aspect of the invention the detecting device is connected to theheater switch. The heater switch is adapted to be controlled by inforrnation from the detectingdevice. Thanks to these provisions it is possible to detect, in a simple and reliable way, anexternal source of electric energy and activate the heater despite of the vehicle being not in operation.

According to an optional aspect of the invention there is a control unit arranged between the detecting device and the heater switch and the control unit is adapted to control the heater lO switch based on information from the detecting device. Thanks to these provisions it ispossible to process inputs to determine Whether the high voltage battery should be heated ornot. These inputs may for example include high voltage battery temperature and /or SLI battery voltage.

At some embodiments at least one temperature sensor is connected to the control unit toprovide high voltage battery temperature to the control unit. Hereby it is possible to start thebattery heater only When heating is necessary. At some embodiments at least one voltagesensor may be connected to the control unit to provide SLI battery voltage to the control unit.Hereby it is possible to determine the charging status of the SLI battery and to determine ifthere is enough energy available in the SLI battery or if the SLI battery needs to be charged.

According to an optional aspect of the invention the means adapted to detect the connectioncomprises a relay adapted to close a contact switch, in Which the relay is arranged in thedetecting device, upon a connection of the electrical circuit to the external source of electricenergy. This constitutes a simple and reliable Way for detecting the connection of electric energy to the electrical circuit.

According to an optional aspect of the invention the electrical circuit comprises a chargingunit adapted to charge the SLI battery. Using a charging unit makes it possible to charge theSLI battery before the battery heater is activated or to heat the high voltage batterysimultaneously as charging the SLI battery, When the vehicle is not in operation. But it is also possible to heat the high voltage battery only by the use of the invention.

In accordance With the present invention there is also provided a vehicle comprising an arrangement for heating a high voltage battery according to What is mentioned above.

In accordance With the present invention there is also provided a computer programcomprising program code, Which program, When the program code is eXecuted in a computer,causes the computer to effect the methods mentioned above. The invention also relates to acomputer program product comprising a data storage medium Which can be read by the computer and on Which the program code of a computer program is stored. lO It is to be understood that both the foregoing general description and the following detaileddescription are eXemplary and are intended to provide further eXplanation of the invention asclaimed. Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following detailed description.

BRIEE DESCRIPTION OF THE DRAWINGS The invention will now be described in greater detail with reference to the accompanying drawings in which: Fig. l is a schematic view of a hybrid vehicle.

Fig. 2 is a schematic view of a control unit shown in fig.l.

Fig. 3 is a flowchart of an embodiment of the invention.

DETAILED DESCRIPTION The invention will now be described with reference to the drawings in which some eXemplaryembodiment are shown. Well-known functions or constructions will not necessarily be described in detail for brevity and/or clarity.

Fig.l shows schematically a hybrid vehicle l comprising a hybrid controller 2, an electricalmachine 3 and an intemal combustion engine 4. The hybrid vehicle l further comprises ahigh voltage battery 5 and a SLI (Starting, Lighting, Ignition-battery) battery 6. The highvoltage battery 5 is arranged for providing power for the propulsion of the hybrid vehicle l.The high voltage battery 5 is connected to the electrical machine 3. The SLI battery 6 isarranged to provide power for a low voltage DC system of the hybrid vehicle l, including providing power to loads 28, including accessories 7 and a start motor 8 for the internal combustion engine 4. The accessories 7 may for example be electrical controllers, windshieldwipers, lamps, air conditioners etc.. The high voltage battery 5 has a high DC level voltage,such as for example 400 V or 800 V, higher than the SLI battery 6, which supplies DC at alow voltage e. g. l2 or 24 V. Further, the high voltage battery 5 and/or the SLI battery 6 maybe a single battery or a battery pack comprising multiple batteries that are electricallyconnected to each other. At some embodiments the high voltage battery 5 may be a battery ofan electrically powered vehicle. The hybrid vehicle l shown in Fig .l also comprises traction wheels ll, a gearbox 9 and a differential gear l0.

The high voltage battery 5 may have an optimal operating temperature. At higher and lowertemperatures the efficiency of the high voltage battery 5 may be reduced. The high voltagebattery 5 may therefore need to be heated at times when it is at too low a temperature andcooled when it is at too high a temperature. When the high voltage battery 5 needs heatingthis can be effected by means of a battery heater l2 which may be an electrical component or coolant from the cooling system which cools the internal combustion engine 4.

The hybrid controller 2, which may be an Electronic Control Unit (ECU), may be adapted tomonitor and control various aspects of the hybrid vehicle l. For example, the hybridcontroller 2 may be connected to the intemal combustion engine 4 and the electrical machine3 to monitor and control their operation and performance. The hybrid controller 2 may also beconnected to the high voltage battery 5 or to a regulating equipment (not shown) connected tothe high voltage battery 5 to regulate the flow of electrical energy between the high voltagebattery 5 and the electrical machine 3 and to control the charging of the high voltage battery 5when the electrical machine 3 serves as a generator. Further, the hybrid controller 2 may,which is not shown in the figure, be connected to the battery heater l2 and adapted to start orstop the battery heater l2 depending on the temperature of the high voltage battery 5 when the hybrid vehicle l is in operation.

Further, the hybrid vehicle l comprises an arrangement for heating the high voltage battery 5when the hybrid vehicle l is not in operation. The arrangement may comprise a control unit l3 adapted to start or stop the battery heater l2 when the hybrid vehicle l is not in operation, e.g. When parked. The control unit 13 may be adapted to process inputs to determine whetherthe high voltage battery 5 should be heated or not. These inputs may include high voltagebattery temperature and/or SLI battery voltage. Battery temperature may be provided by abattery temperature sensor 14 located on the high voltage battery 5. Altematively, multipletemperature sensors 14 may be used: Battery voltage may be provided by a voltage sensor 17located on the SLI battery 6. Alternatively the control unit 13 may contain an intemal voltagesensor accurate enough to approXimate the SLI battery voltage to this internal voltage in thecontrol unit 13. Further, a heater switch 15 may be arranged between the SLI battery 6 and thebattery heater 12, which heater switch 15 is arranged for connecting and disconnecting thebattery heater 12 to/from power received from the charging unit 22, i.e. to start or stop thebattery heater 12. The heater switch 15 is connected to the control unit 13 and is adapted to be controlled by information from the control unit 13.

Fig. 1 further shows that the hybrid vehicle 1 may be provided with a charging socket 18 forplugging in a cable 19 and connecting it to an electrical circuit 20 in the vehicle 1 for feedingelectric energy there through from an extemal source of electric energy 21, e. g. at a chargingstation, to the electrical circuit 20. The electrical circuit 20 comprises a charging unit 22connected to the SLI battery 6 and adapted to charge the SLI battery 6. At some embodimentsthe electrical circuit 20 may comprise an interior heating unit 49 adapted to heat the interior ofthe vehicle 1, i.e. its driver and passenger compartment and/or its cargo space. At someembodiments the electrical circuit 20 may comprise an engine heating unit 50 adapted to heatthe intemal combustion engine of the vehicle 1. Further, the socket 18 may be arranged at thefront 23 of the vehicle 1 and the extemal source of electric energy 21 may be a 230 V supply network.

At some embodiments the control unit 13 may be adapted to monitor the SLI battery 6 and/orthe charging unit 22 during a charging process and to determine how the energy from thecharging unit 22 may be used, e. g. if the energy may be used to charge the SLI battery 6 andprovide power to some crucial accessories 29 only, while the start of the battery heater 12 isdelayed until the voltage of the SLI battery 6 is equal to or above a threshold voltage value, or if the energy may be used to start the battery heater 12 as soon as the electrical circuit 20 is connected to the external source of energy 21. The crucial accessories 29 may for example be security systems, key fob sensors and memories in control units.

At some embodiments the control unit 13 may be adapted to monitor the SLI battery 6 and/orthe charging unit 22 and to, when the charging process has been interrupted but the hybridvehicle 1 is still not in operation, determine how the energy from the SLI battery 6 may beused. The charging process may for example have been interrupted by a timer after apredetermined charging time has elapsed or after a fuse has blown in the charging station or inthe vehicle. At such an interruption the control unit 13 may be adapted to for example allowaccessories 7 in general or crucial accessories 29 in particular to discharge the SLI battery 6and/or allow the battery heater 12 to discharge the SLI battery 6. At some embodiments thedischarge may be allowed if the voltage of the SLI battery 6 is equal to or above the threshold voltage value.

The arrangement for heating the hybrid battery 5 comprises a detecting device 24 connectedto the electrical circuit 20. The detecting device 24 comprises means 27 adapted to detect anestablishment of a connection of the electrical circuit 20 to the extemal source of electricenergy 21, by the cable 19, and adapted to activate the battery heater 12 when the electricalcircuit 20 is connected to the external source of electric energy 21. The detecting device maybe adapted to emit information 47 when connected to the extemal source of electric energy21. The information 47 may comprise a signal, such as a wake up signal or a trigger signal,which may be adapted to activate, wake or trigger the battery heater despite of the vehiclebeing not in operation i.e. when the ignition is switched off.

There are several ways for the detecting device 24 to detect the connection. E. g. by using an optical transmitter.

Fig. 2 shows schematically the control unit 13 in fig. 1. The control unit 13 is adapted tocontrol the heater switch 15 based upon information 47 from the detecting device 24. Thecontrol unit 13 comprises a calculation unit 40 which may take the form of substantially anysuitable type of processor or microcomputer, e. g. a circuit for digital signal processing (digitalsignal processor, DSP) or a circuit with a predetermined specific function (application specific integrated circuit, ASIC). The calculation unit 40 is connected to a memory unit 41 which may be incorporated in the control unit l3 and Which provides the calculation unit 40 with, forexample, the stored program code and/or the stored data which the calculation unit 40 needsin order to be able to perform calculations. The calculation unit 40 is also adapted to store partial or final results of calculations in the memory unit 4l.

The control unit l3 is provided with devices 42, 43, 44 for receiving input signals and adevice 46 for sending an output signal. These input and output signals may comprisewaveforms, pulses or other attributes which the signal receiving devices 42, 43, 44 can detectas information and which can be converted to signals processable by the calculation unit 40.The calculation unit 40 is adapted to receive the input signals and the signal sending device 46is adapted to convert the signals received from the calculation unit 40 in order to create, e. g.by modulating the signals, an output signal which can be transmitted to the heater switch 15.Each of the connections to the devices 42, 43, 44 for receiving input signals and the device 46for sending output signals may take the form of one or more from among the following: cable,data bus, e. g. a CAN (controller area network) bus, a MOST (media orientated systems transport) bus or some other bus configuration, or a wireless connection.

The function of the control unit l3 may depend on signals from various sensors or signalsfrom one or more additional control units. Inforrnation 47 conceming the establishment of aconnection of the electrical circuit 20 to the external source of energy 2l (fig. l) may forexample be provided by the detecting device 24. High voltage battery temperature may forexample be provided by the temperature sensor l4 and SLI battery voltage may for example be provided by the voltage sensor l7.

The monitoring and/or control of different functions in the vehicle, such as for example themonitoring and/or control of the heater switch 15, may be implemented in a computerprogram comprising program code, which program, when the program code is executed in acomputer, causes the computer to effect the monitoring and/or control. The computer programis contained in a computer program product°s computer-readable data storage medium whichtakes the form of a suitable memory, e. g. ROM (read-only memory), PROM (programmableread-only memory), EPROM (erasable PROM), flash memory, EEPROM (electrically erasable PROM), hard disc unit, etc. The suitable memory may be the memory unit 41 which may be incorporated in the control unit l3.

The text below refers to figs.l and 3. Fig. 3 shows a flow chart of a method according to anembodiment of the invention carried out for heating a high voltage battery 5 for a vehicle l.The method includes a step 55 of connecting the electrical circuit 20 to the extemal source ofelectric energy 2l. In a step 56 it is detected an establishment of the connection of theelectrical circuit 20 to the external source of electric energy 2l, when such a connectionoccurs. In a step 57 information 47 is emitted as a confirrnation that the electrical circuit 20 isconnected to the external source of electric energy 2l. In a step 58 a value for the chargingstatus of the SLI battery 6 is deterrnined. The value for the charging status may be detected bysensing if a voltage of the SLI battery 6 is equal to or above a predeterrnined threshold value.The threshold voltage value may be a predetermined constant based on battery specificationsthat is programed into the memory unit 4l (fig. 2) of the control unit l3. If the voltage of theSLI battery 6 is equal to or above the predetermined threshold voltage value i.e. high theremay be enough energy in the SLI battery 6 to power the battery heater l2. If the voltage of theSLI battery 6 is below the predeterrnined threshold voltage value i.e. low the SLI battery 6may be charged by the charging unit 22 in a step 59. In a step 60 a temperature is deterrnined.The temperature may be detected by sensing if the temperature of the high voltage battery -is equal to or below a predeterrnined threshold value. The threshold temperature value maybe a predetermined constant that is programed into the memory unit 4l (fig.2) of the controlunit l3. If the value for the charging status of the SLI battery 6 is equal to or above thepredetermined value and the temperature of the high voltage battery 5-is equal to or below thethreshold temperature value i.e. low, heating is desired and the method continues at step 6l byactivating the battery heater l2. If the temperature is above the threshold value i.e. high, efforts to increase the temperature of the high voltage battery 5 may be unnecessary.

At some embodiments the battery heater l2 may by stopped after a predetermined timeperiod, for example by a timer or by a predeterrnined time value that is pro gramed into thememory unit 4l (fig.2). At some embodiments the method may comprise a step 62 in which atemperature may be detected. The temperature may be detected by sensing if the temperature of the high voltage battery 5 is equal to or below a predetermined threshold value. The lO ll threshold temperature value may be a predeterrnined constant that is pro gramed into thememory unit 41 (fig.2) of the control unit 13. If the temperature is equal to or below thethreshold temperature value i.e. low, additional heating is desired and the method continues atstep 63 by maintaining the heating. If the temperature is above the predetermined thresholdvalue i.e. high, efforts to increase the temperature of the high voltage battery 5 may be unnecessary and the battery heater 12 is stopped in a step 54.

The method described can of course be extended to comprise over ride functions by thedriver/operator to enforce starting or stopping high voltage battery heating, namely in that thedriver/operator of the vehicle being able to enforce starting or stopping high voltage battery heating by the use of e. g. a push button (not shown in figure).

The method makes it possible to start the battery heater only when additional heating isnecessary and despite of the vehicle being not in operation i.e. when the ignition is switchedoff. This makes it is possible to preheat the battery to a more battery-friendly temperaturebefore starting the vehicle, causing the battery to run more efficiently when started and thereby retard battery aging at cold temperatures.

The present invention is not limited to the embodiments described above, but relates to andcomprises all embodiments within the scope of protection of the attached independent claims.The vehicle is described as a hybrid vehicle but it may be an electrical vehicle. The vehiclemay for example be a truck, a bus or a passenger car. Further, the vehicle may be a commercial vehicle or a constructional vehicle or the like.

The hybrid vehicle 1 comprises a control system that may consist of a communication bussystem (not shown) consisting of one or more communication buses that serves asconnections between electronic control units, controllers, and components located on thevehicle. A control system of this kind may comprise a large number of controllers and controlunits, and the responsibility for a specific function may be divided amongst two or morecontrollers or control units. For the sake of simplicity, fig. 1 only shows twocontrollers/control units 2, 13 but in reality the control of a specific function may depend on information which may be received from one or more further controllers or control units. 12 As used herein, the term “comprisíng” or “comprises” does not exclude other features,elements, steps, components, functions or groups thereof. Further, the índefíníte article "a" or "an" does not exclude a pluralíty.