Method and device for trickle charging a battery of a vehicle

Abstract

The invention relates to a method for trickle charging a battery (40) of a vehicle (10), wherein current pulses (50) of an energy source (12) having a predeterminable time duration (52) are provided to the battery (40) at a predeterminable interval of time (54) until a voltage of the battery (40) is at least equal to a voltage of the energy source (12). The time duration (52) of the current pulses (50) and the interval of time (54) between the current pulses (50) are selected such that an on-board power supply system of the vehicle (10) remains in a passive mode. The invention further relates to a device (100) for trickle charging a battery (40) of a vehicle (10) using such a method.

Description

[0001] Method and device for trickle charging a vehicle battery

[0002] The invention relates to a method and a device for trickle charging a battery of a vehicle.

[0003] Vehicle batteries, especially starter batteries, are subject to natural self-discharge due to their cell chemistry. If vehicles are left idle for an extended period, this self-discharge can become so advanced that the vehicle can no longer be started. Therefore, it is common practice to charge the battery either shortly before restarting with a normal charging current or continuously with a significantly lower current during the parking period. In the latter case, this is referred to as battery maintenance charging.

[0004] EP 3459 155 B1 describes a method for charging a battery.

[0005] The method comprises selecting a pulse period. A charging pulse is provided to the battery. For this purpose, a charging current is provided from a power source to the battery at the beginning of an ON period of the charging pulse. A current flow through the battery is determined, and a change in the current flow through the battery is detected. A duration of the ON period of the charging pulse is determined based on when the change in current flow through the battery was detected relative to the application of the charging current to the battery. The charging current from the power source to the battery is interrupted at an end of the ON period of the charging pulse. Thereafter, a duration of an OFF period of the charging pulse is determined. A difference between the selected pulse period and the ON period of the charging pulse is calculated. A delay is applied by a duration of the OFF period of the charging pulse. Thereafter, another pulse period is selected.These steps are repeated using the selected pulse period.

[0006] US 4661758 discloses a solar power supply and battery charging system comprising a solar energy source that supplies a consumption current to a load and a charging current to a secondary battery when the solar energy source is exposed to sunlight. A secondary battery is connected in series with the solar energy source and is charged by the current supplied by the solar energy source. A control circuit is connected to the battery to determine the battery's state of charge and, in turn, controls the operation of a variable pulse width generator. The output pulses of the pulse width generator are applied to a short-circuit resistance switch connected to the terminals of the connected power source to periodically open the short-circuit switch for varying time intervals determined by the secondary battery's state of charge.

[0007] Solar controllers primarily use two methods to feed energy into electrical energy storage systems: pulse width modulation (PWM) and maximum power point tracking (MPPT).

[0008] In pulse-width modulation, a square-wave signal is set to oscillate between two different voltage levels. In this case, one voltage level can also be zero, so in principle, a signal can also be a rapid sequence of on and off states. Pulse-width modulation has a wide range of uses in electronics.

[0009] In electrical engineering, particularly in photovoltaics, the term "maximum power point tracking" refers to a process in which the electrical load of a solar cell, a solar module, or several solar modules connected in series is adjusted so that the cells can extract the greatest possible power. For solar cells, this optimal operating point is not constant but depends, among other things, on the irradiance, the temperature at the solar module, and the type of solar cell.

[0010] An object of the invention is to provide an improved method for trickle charging a battery of a vehicle.

[0011] A further object is to provide a device for trickle charging a battery of a vehicle using such an improved method.

[0012] The aforementioned objects are achieved by the features of the independent claims. Advantageous embodiments and advantages of the invention emerge from the further claims, the description, and the drawings.

[0013] According to one aspect of the invention, a method for trickle charging a vehicle battery is proposed, wherein current pulses from an energy source are provided to the battery with a predeterminable duration at a predeterminable interval until an electrical voltage of the battery is at least equal to an electrical voltage of the energy source. The duration of the current pulse and the interval between the current pulses are selected such that an on-board electrical system of the vehicle remains in a passive mode.

[0014] The electrical system of a modern motor vehicle always has a low quiescent current, which leads to battery discharge. Therefore, an improved charging method for trickle charging the battery is advantageously proposed. This method can charge the battery with low power, for example, using a solar module, without the vehicle's active electrical system consuming more energy than the solar module can supply.

[0015] In order to be able to charge the battery continuously with low power to maintain the charge level, unwanted activation of the on-board electrical system can be avoided, which would happen with a continuous charging current. It is therefore proposed that the charging current be delivered to the battery only in pulses. The current pulse is selected to be so short that the electronics of the on-board electrical system are not activated and remain in a passive or sleep mode, with the next current pulse only occurring after a certain duration, which allows the system to remain in sleep mode. The current pulses are selected to be so short and occur at such a large time interval that any error suppression of the on-board electrical system suppresses these current pulses as irrelevant and the vehicle or its electrical consumers are not activated or "woken up".

[0016] The pulsation can advantageously be adjusted depending on the specific on-board electronics used in the vehicle. The pulse length can be selected short enough and the charging current small enough that these values ​​are acceptable within the fluctuation range of disturbances in the on-board electrical system. This can prevent unwanted activation of the on-board electrical system, which would activate or wake up control units. The control units would then be active for a certain duration and consume power, which can be prevented according to the invention. A sufficient period of time can be waited until the next current pulse, until the on-board electrical system has forgotten the disturbance and then, at the next current pulse, perceives the charging current as a new, tolerable disturbance that remains below an upper limit of disturbances that would otherwise lead to waking up the on-board electrical system.

[0017] The current pulses can be applied to the battery in a periodic sequence with a specific periodic time interval. However, this is not mandatory. Optionally, the current pulses can also be applied in an irregular sequence. The time interval between the current pulses can be equal to or greater than a minimum time interval.

[0018] According to an advantageous embodiment, the method can comprise at least the steps of: determining the electrical voltages of the battery and the energy source by means of a control unit, wherein the control unit is electrically coupled to the energy source and the battery; if the electrical voltage of the battery is lower than the electrical voltage of the energy source, checking whether a control pulse, in particular of a pulse generator, is present at the control unit; if the control pulse is present, switching through a switching element by the control unit, which provides the current pulse to the battery; checking whether the control pulse is switched off; if the control pulse is switched off, blocking the switching element.

[0019] In this way, the battery can be recharged with limited power without activating the vehicle's electrical system. This requires that the energy source delivers a voltage that exceeds the battery voltage. The sequence of current pulses can advantageously be controlled by a pulse generator, which specifies the appropriate duration and interval at which the current pulses are to be delivered to the battery to the control unit. The control unit can then deliver the defined current pulses to the battery by controlling a suitable switching element.

[0020] According to an advantageous embodiment of the method, the duration of the current pulse and the time interval between the current pulses can be set manually according to predeterminable parameters and / or determined from a vehicle characteristic map and / or determined by measurements on the battery and / or the energy source. The predeterminable parameters can in particular be determined by the specific on-board electrical system. The overall maintenance charging system can advantageously be adjusted to various vehicle systems. The necessary values ​​can be set manually according to parameters, read from a characteristic map for the respective vehicle, or determined through testing and measuring, so that the parameters of the charging electronics for the current pulses, in particular the length and magnitude of the current pulses, and the time intervals between the current pulses, can be suitably adjusted.

[0021] According to an advantageous embodiment of the method, a solar module can be used as the energy source, wherein electrical energy generated by the solar module is temporarily stored in an electrical buffer storage device.

[0022] Using a solar module as an energy source offers the possibility of self-sufficient battery maintenance charging based on a comparatively small solar panel. Such a solar module proves sufficient even in adverse winter weather conditions. Furthermore, such a solar module is particularly simple and cost-effective to implement.

[0023] When exposed to sunlight, the solar module generates electrical energy, which is fed into the buffer storage. The buffer storage can be configured as a capacitor, for example. As soon as the voltage of the buffer storage reaches a value significantly higher than the battery voltage, a current pulse can be delivered to the battery.

[0024] Advantageously, the buffer storage can be provided in such a size that the method according to the invention can be carried out with very little technical effort. If the buffer storage is designed as a capacitor, in particular as a supercapacitor (so-called supercapacitors) or several interconnected capacitors, which then have a capacitance of over one farad, in particular over 10 farads, for example, sufficient energy can be temporarily stored to provide a corresponding charging pulse for trickle charging the battery. For example, an electrical energy of at least 1000 joules can be stored in such a buffer storage, so that a charging pulse with 100 joules of electrical energy can be delivered to the battery without immediately emptying the buffer storage.

[0025] With such a design of the buffer storage, it would be particularly advantageous to simplify the control of the charging pulses, since the stored electrical energy in the capacitor changes its voltage and the charging pulse can therefore start as soon as the voltage in the capacitor rises above a first value. The charging pulse then essentially falls as the capacitor discharges with the battery charging pulse until the capacitor voltage essentially corresponds to the battery voltage and the current flow decreases and stops due to the falling voltage difference between the capacitor and the battery. The charging pulse can also advantageously be ended when the voltage across the capacitor falls below a second value, since in this case the smaller voltage difference between the capacitor and the battery means that efficient trickle charging of the battery is hardly possible.However, after a maximum duration of the charging pulse, it will be terminated anyway in order to comply with the requirement to keep the vehicle's electrical system in passive mode.

[0026] To implement the method according to the invention, the temporal sequence and duration of the charging pulses must then be controlled, implemented and maintained, so that, for example, a simple clock generator or pulse generator can be used for this purpose.

[0027] The method according to the invention can thus advantageously be implemented with a correspondingly large capacitor as the buffer storage device, by primarily determining the voltage across the capacitor and determining the charging pulses by their duration and temporal sequence. Accordingly, a charging pulse is started from the buffer storage device to the battery when the voltage across the capacitor is above a first value and a minimum duration has elapsed since the end of the last charging pulse. Depending on the design of the components, the duration of the charging pulse itself can then also be determined by a pulse generator in order to terminate charging pulses that are too long should the capacity of the buffer storage device be so large that its discharge to maintain the battery charge would otherwise be too long to leave the vehicle's electrical system in a passive mode.

[0028] Particularly advantageously, the first capacitor voltage value above which the charging pulse can start can be specified to the system and / or adjustable within the system. In particular, the time interval between charging pulses, especially between the end of a previous charging pulse and the beginning of a current charging pulse, can also be specified and / or adjusted within the system, in particular a pulse generator.

[0029] If the system operates with a maximum duration of the charging pulse, which can of course also be specified and / or adjusted, the time duration can also be used directly between the beginnings of consecutive charging pulses, since the maximum duration of the charging pulse and the time duration between the charging pulses can be added together.

[0030] In order to comply with the requirement to keep the vehicle's electrical system in passive mode, and this requirement is closely linked to the parameters of the electrical system and its activation, these parameters must also be taken into account when setting the buffer storage voltage and the duration, so that these must always be adapted to the specific electrical system and thus at least to the specific vehicle type. For this purpose, these values ​​and parameters must be specified and can, for example, be entered directly, preset by the manufacturer, and / or selected from stored values. It is also possible to determine these values ​​initially by conducting a test measurement of the maintenance charging system in the electrical system itself and then save the determined values ​​for implementation.

[0031] Predefined and stored values ​​can also be set, for example, based on vehicle data, determined from a characteristic map, or through communication between the maintenance charging system and the vehicle electrical system itself.

[0032] This advantageous design makes it possible to construct and use a particularly simple system for trickle charging a battery. In addition, such a system can always supply itself with energy for control purposes via the buffer storage, so that no external energy is required for control. If the buffer storage is completely empty, no charging pulses need to be controlled, and when the buffer storage refills, the initial energy from the buffer storage can be used for control purposes, in particular to operate the pulse generator and to determine the voltage at the buffer storage itself. A corresponding charging pulse is only emitted when the voltage is above a first value, meaning there is always enough energy in the buffer storage to operate the control system in advance.

[0033] Furthermore, this design allows for completely autonomous control and configuration of the maintenance charging system on or in the vehicle, thus avoiding any impact on the vehicle's electrical system. The key requirement of keeping the vehicle's electrical system in passive mode is always met, thus ensuring that it is acted upon. The vehicle's battery also remains technically unaffected, apart from the charging pulses for maintenance charging, and no other adjustments are required.According to an advantageous embodiment, the method may further comprise: determining the electrical voltage of the buffer storage by means of the control unit, wherein the control unit is electrically coupled to the buffer storage and the battery; if the electrical voltage of the buffer storage is greater than the electrical voltage of the battery, checking whether providing the current pulse is possible or permissible; if providing the current pulse is possible or permissible, switching through the switching element by the control unit, which provides the current pulse to the battery; checking whether an end of the temporal duration of the current pulse has been reached; if the end of the temporal duration of the current pulse has been reached, blocking the switching element.

[0034] In this way, the battery can be recharged with limited power without activating the on-board electrical system. The prerequisite is that the voltage of the buffer storage device significantly exceeds the battery voltage. The control unit then checks whether a sufficient time has elapsed since the last current pulse so that a new current pulse can be sent. The control unit can then deliver the next current pulse to the battery by controlling the switching element. It then checks whether the duration of the current pulse is coming to an end. Once the end is reached, the switching element is blocked and the current pulse is thus switched off. The control unit can then return to determining the voltage of the buffer storage device. By designing the solar module appropriately in relation to the size of the buffer storage device, advantageous trickle charging can be achieved.

[0035] According to a further aspect of the invention, a device for trickle charging a vehicle battery using such a method is proposed, comprising at least one energy source which, during normal operation, is electrically coupled to the battery via a control unit. The control unit is designed to deliver current pulses from the energy source to the battery with a predeterminable duration at a predeterminable time interval.

[0036] Advantageously, a device for the improved charging method for trickle charging the battery is proposed, which can charge the battery with low power, for example by means of a solar module, without an active on-board network of the vehicle consuming more energy than the solar module can supply.

[0037] In order to be able to charge the battery continuously with low power to maintain the charge level, unwanted activation of the on-board electrical system can be avoided, which would happen with a continuous charging current. It is therefore proposed that the charging current be delivered to the battery only in pulses. The current pulse is selected to be so short that the electronics of the on-board electrical system are not activated and remain in a passive or sleep mode, with the next current pulse only occurring after a certain duration, which allows the system to remain in sleep mode. The current pulses are selected to be so short and occur at such a large time interval that any error suppression of the on-board electrical system suppresses these current pulses as irrelevant and the vehicle or its electrical consumers are not activated or "woken up".

[0038] The pulsation can advantageously be adjusted depending on the specific on-board electronics used in the vehicle. The pulse length can be selected short enough and the charging current small enough that these values ​​are acceptable within the fluctuation range of disturbances in the on-board electrical system. This can prevent unwanted activation of the on-board electrical system, which would activate or wake up control units. The control units would then be active for a certain duration and consume power, which can be prevented according to the invention. A sufficient period of time can be waited until the next current pulse, until the on-board electrical system has forgotten the disturbance and then, at the next current pulse, perceives the charging current as a new, tolerable disturbance that remains below an upper limit of disturbances that would otherwise lead to waking up the on-board electrical system.

[0039] The device can be installed directly in a vehicle or added as a retrofit system. Due to the minimal intervention in the vehicle's system, such a retrofit system can be installed and used permanently or temporarily. For example, such a device can be installed only for extended periods of inactivity, while parked, or while waiting outdoors, and can be removed again when the vehicle is in continuous operation and maintenance charging is no longer required.

[0040] According to an advantageous embodiment of the device, the control unit can comprise a pulse generator or be electrically coupled to a pulse generator. The pulse generator controls the sequence and duration of the individual current pulses. The pulse generator can be connected to the control unit as a separate unit. Alternatively, however, it is also possible for the pulse generator to be integrated into the control unit. According to an advantageous embodiment of the device, the energy source can be designed as a solar module with an electrical buffer storage. The buffer storage can be designed for the temporary storage of electrical energy generated in the solar module.

[0041] Using a solar module as an energy source offers the possibility of self-sufficient battery maintenance charging based on a comparatively small solar panel. Such a solar module proves sufficient even in adverse winter weather conditions. Furthermore, such a solar module is particularly simple and cost-effective to implement and can be replaced if damaged.

[0042] When exposed to sunlight, the solar module generates electrical energy, which is fed into the buffer storage. The buffer storage can be configured as a capacitor, for example. As soon as the voltage of the buffer storage reaches a value significantly higher than the battery voltage, a current pulse can be delivered to the battery.

[0043] The proposed device thus advantageously features energy self-sufficiency. The control unit, acting as a solar controller, can be powered by the energy from the solar module. This means that the moment the first ray of sunlight arrives, the buffer storage, such as a capacitor, begins to fill, thus charging the capacitor. This applies regardless of whether the solar module is being used for the first time or simply exiting an underground garage after a long period of parking.

[0044] As soon as the capacitor reaches a voltage sufficient to operate the control unit's processor, the control unit can start the process. Since the capacitor only discharges to a maximum of the battery's voltage during recharging, which is significantly higher than the processor's required operating voltage, the solar module remains in operation as long as sunlight is sufficient to compensate for the self-discharge caused by the control electronics' own consumption via the solar energy still supplied.

[0045] According to an advantageous embodiment of the device, the control unit can be designed to provide the current pulses to the battery by controlling a switching element. In particular, the switching element can be designed as a semiconductor switching element, in particular as a transistor. In particular, the switching element can be designed to switch a negative electrical potential. The sequence of current pulses can be controlled via a pulse generator, which specifies the appropriate duration and time interval at which the current pulses are to be provided to the battery to the control unit. The control unit can then advantageously provide the thus defined current pulses to the battery by controlling a suitable switching element.

[0046] Advantageously, the solar module can be electrically coupled to the buffer storage via a forward-biased diode. This diode prevents reverse discharge of the buffer storage when solar radiation decreases.

[0047] Furthermore, the buffer storage can be electrically connected to the vehicle via a forward-biased diode. This diode ensures that the battery does not reverse charge the buffer storage in the event of a fault.

[0048] Advantageously, the energy source, in particular the solar module, can be further electrically coupled to the battery via an electrical resistor in order to limit the charging current due to the voltage difference between the buffer storage and the battery when the switching element is opened.

[0049] According to an advantageous embodiment of the device, the energy source can be electrically coupled to the vehicle via at least one electrical fuse. The fuse ensures that the energy source is safely disconnected from the vehicle in the event of a fault.

[0050] According to an advantageous embodiment of the device, the energy source can be electrically coupled to the vehicle via a jump-start connection point. This allows the device to be electrically connected to the vehicle in a particularly convenient manner. Such a jump-start connection point is common in many vehicles. This ensures a permanent connection to the vehicle's battery. In this way, the charging current flows only in parallel and not in series with the other systems of the vehicle's electrical system. Furthermore, there is no need to intervene in the battery's wiring, which is advantageous for safety reasons, especially for a retrofit system.

[0051] Further advantages are shown in the following drawing description.

[0052] The drawings illustrate an embodiment of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will expediently consider the features individually and combine them into further meaningful combinations.

[0053] Showing:

[0054] Fig. 1 is a system overview of a device for trickle charging a battery of a vehicle according to an embodiment of the invention;

[0055] Fig. 2 is a flow chart of a method for trickle charging a battery of a vehicle using a device according to Fig. 1;

[0056] Fig. 3 shows a temporal sequence of current pulses for a trickle charge of a battery of a vehicle according to an embodiment of the invention;

[0057] Fig. 4 is a system overview of a device for maintaining the charge of a vehicle battery according to a further embodiment of the invention; and

[0058] Fig. 5 is a flowchart of a method for trickle charging a battery of a vehicle using a device according to Fig. 4.

[0059] In the figures, identical or similar components are numbered with the same reference numerals. The figures show only examples and are not to be understood as limiting.

[0060] Figure 1 shows a system overview of a device 100 for trickle charging a battery 40 of a vehicle 10 according to an embodiment of the invention.

[0061] The device 100 comprises an energy source 12, which, during normal operation, is electrically coupled to the battery 40 of the vehicle 10 via a control unit 20. The device 100 is electrically coupled to the vehicle 10 via a jump-start support point 70.

[0062] The control unit 20 is designed to provide current pulses 50 from the energy source 12 with a predeterminable duration 52 at a predeterminable time interval 54 to the battery 40. For this purpose, the control unit 20, as shown in Figure 1, can be electrically coupled to a pulse generator 22, which provides the time basis for providing the current pulses 50. Alternatively, the pulse generator 22 can also be integrated into the control unit 20. Figure 2 shows a flowchart of a method for trickle charging the battery 40 of the vehicle 10 using the device 100 according to Figure 1.

[0063] According to the method, current pulses 50 from an energy source 12 are provided to the battery 40 with a predeterminable duration 52 at a predeterminable interval 54 until an electrical voltage of the battery 40 is at least equal to an electrical voltage of the energy source 12. The duration 52 of the current pulse 50 and the interval 54 between the current pulses 50 are selected such that an on-board electrical system of the vehicle 10 remains in a passive mode.

[0064] It has been empirically determined that current pulses of, for example, 4 seconds in length and at least 15 seconds in pause are ignored by the on-board electrical system of a vehicle 10.

[0065] Figure 3 shows an example of such a temporal sequence of current pulses 50. The current 61 varies as a function of time 60 between an off state 64 and an on state 62. The current pulses 50 have a duration 52 and are provided with a minimum temporal interval 54. Optionally, a larger temporal interval 54 can be selected.

[0066] The method comprises at least the steps illustrated in Figure 2. The process is started in step S100. Then, in step S102, the electrical voltages of battery 40 and energy source 12 are determined by means of control unit 20.

[0067] In the next step S104, it is checked whether the electrical voltage of the battery 40 is lower than the electrical voltage of the energy source 12. If this is not the case, the determination of the electrical voltages in step S102 is repeated.

[0068] This loop is repeated until the voltage of the battery 40 is lower than the voltage of the energy source 12.

[0069] Next, in step S106, it is checked whether a control pulse from a pulse generator 22, generated in step S114, is present at the control unit 20. If this is not the case, the determination of the electrical voltages is repeated in step S102.

[0070] If the control pulse is present, the control unit 20 switches on a switching element 24, such as a switch or a transistor, in step S108, which supplies the current pulse 50 to the battery 40. Subsequently, in step S110, it checks whether the control pulse has been deactivated again. If this is not the case, the system returns to step S108. This process is repeated until the control pulse is deactivated.

[0071] When the control pulse is switched off, the switching element 24 is blocked in step S112, thereby terminating the current pulse 50. The loop then restarts with step S102.

[0072] The duration 52 of the current pulse 50 and the time interval 54 between the current pulses 50 can be manually adjusted according to predefined parameters. Alternatively or additionally, the values ​​can be determined from a characteristic map of the vehicle 10. It is also possible for the values ​​to be determined by measurements on the battery 40 and / or the energy source 12.

[0073] In this way, the battery 40 can be recharged with limited power without activating the vehicle's electrical system. This requires that the energy source 12 delivers a voltage that exceeds the voltage of the battery 40. The sequence of current pulses 50 can advantageously be controlled via a pulse generator 22, which specifies to the control unit 20 the appropriate duration and time interval at which the current pulses 50 are to be delivered to the battery 40. The control unit 20 can then deliver the thus defined current pulses 50 to the battery 40 by controlling a suitable switching element 24.

[0074] Figure 4 shows a system overview of a device 100 for trickle charging a battery 40 of a vehicle 10 according to a further embodiment of the invention.

[0075] The energy source 12 is designed as a solar module 14 with an electrical buffer storage 16, wherein the buffer storage 16 serves to temporarily store the electrical energy generated in the solar module 14. The buffer storage 16 can be designed, for example, as a capacitor.

[0076] The device 100 is electrically coupled to the battery 40 via terminal 30, which represents the positive electrical potential of the battery 40, and via terminal 31, which represents the negative electrical potential and / or the electrical vehicle ground of the battery 40. Terminal 30 and terminal 31 can be connected, for example, via the jump-start support point 70 of the vehicle 10. The control unit 20 can switch the current pulses 50 to the battery 40 by controlling a switching element 24, for example a transistor or another suitable semiconductor switching element, via the negative electrical potential. In this exemplary embodiment, the control unit 20 comprises the pulse generator 22, which can simply be designed as a threshold value transmitter.

[0077] The solar module 14 is electrically coupled to the buffer storage 16 via a forward-biased electrical diode 30. The diode 30 prevents reverse discharge of the buffer storage 16 when solar radiation decreases.

[0078] The energy source 12 is electrically coupled to the vehicle 10 via a forward-biased electrical diode 32. This diode 32 ensures that, in the event of a fault, the battery 40 does not reversely charge the buffer storage 16.

[0079] The energy source 12 is electrically coupled to the battery 40 via an electrical resistor 34 in order to limit the charging current due to the voltage difference between the buffer storage 16 and the battery 40 when the switching element 24 is opened.

[0080] The energy source 12 is electrically coupled to the vehicle 10 via at least one electrical fuse 36. The fuse 36 ensures that the energy source 12 is safely disconnected from the vehicle 10 in the event of a fault.

[0081] When exposed to sunlight, the solar module 14 generates electrical energy, which is fed into the buffer storage 16. The buffer storage 16 can be configured, for example, as a capacitor. As soon as the voltage of the buffer storage 16 reaches a value that is significantly higher than the battery voltage, a current pulse 50 can be delivered to the battery 40.

[0082] The proposed device 100 advantageously has a self-sufficient energy supply. The control unit 20, as a solar controller, is fed by the energy of the solar module 14. This means that at the moment the first ray of sunlight arrives, the buffer storage 16, for example, a capacitor, begins to fill, and the capacitor thus charges. This is independent of whether the solar module 14 is being used for the first time or simply exiting an underground garage after a long period of parking. As soon as a voltage is reached at the capacitor that is sufficient to operate the processor of the control unit 20, the control unit 20 starts the process.Since the capacitor only discharges to a maximum of the voltage of the battery 40 during recharging and this is significantly above the necessary operating voltage of the processor, the solar module 14 remains in operation as long as the solar radiation is sufficient to compensate for the self-discharge due to the self-consumption of the control unit 20 via the solar energy that is still supplied.

[0083] Figure 5 shows a flowchart of the method for trickle charging the battery 40 of the vehicle 10 with the device 100 according to Figure 4.

[0084] After initialization, i.e. reaching the processor operating voltage in step S200, the control unit 20 starts in step S202 with the measurement of the voltage of the buffer memory 16, which is proportional to the charge state of the buffer memory 16, for example a capacitor, and thus a measure of the memory content of the buffer memory 16.

[0085] If this charge level is high enough, i.e., the capacitor voltage is, for example, 2 V above the nominal battery voltage, which is checked in step S204, the algorithm checks in step S206 whether a current pulse 50 was already sent shortly beforehand. Thus, the necessary charging pause, the minimum time interval 54 between the current pulses 50, is checked to ensure that the vehicle's electrical system 10 is not awakened.

[0086] If the charging pause has already elapsed, for example when a so-called charge enable flag was set, the switching element 24 switches through in step S208 and the buffer memory 16 discharges into the battery 40. A corresponding current pulse 50 is provided to the battery 40.

[0087] During this process, a check is performed in step S210 to determine whether the end of the charging pulse duration, i.e., the end of the duration 52 of the current pulse 50, has already been reached. If not, the switching element 24 remains open.

[0088] When the end of the charging pulse duration is reached, the switching element 24 is switched off in step S212 and the algorithm returns to the area of ​​measuring the voltage of the buffer storage 16 in step S202. In real-life use, the duration of the charging pause can depend on the solar radiation. On days with little sun, the solar module 14 supplies little energy, which causes the buffer storage 16 to charge very slowly, depending on the ratio of the size of the solar module 14 to the capacity of the buffer storage 16, e.g., a capacitor. Therefore, charging pauses of up to several minutes or even an entire night are conceivable. On sunny days, the capacitor 16 can be charged in significantly less than 15 seconds. In this case, the control unit 20 must prevent the switching element 24 from switching on prematurely.

[0089] List of reference symbols

[0090] 10 vehicles

[0091] 12 Energy source

[0092] 14 solar modules

[0093] 16 buffer storage

[0094] 20 Control unit

[0095] 22 Pulse generator

[0096] 24 switching element

[0097] 30 diodes

[0098] 32 diodes

[0099] 34 Resistance

[0100] 36 Security

[0101] 40 Battery

[0102] 50 current pulses

[0103] 52 duration

[0104] 54 time interval

[0105] 60 time

[0106] 61 Electricity

[0107] 62 A

[0108] 64 From

[0109] 70 external launch base

[0110] 100 device

Claims

Patent claims 1. A method for trickle charging a battery (40) of a vehicle (10), wherein current pulses (50) of an energy source (12) are provided to the battery (40) with a predeterminable time duration (52) at a predeterminable time interval (54) until an electrical voltage of the battery (40) is at least equal to an electrical voltage of the energy source (12), wherein the time duration (52) of the current pulse (50) and the time interval (54) of the current pulses (50) are selected such that an on-board electrical system of the vehicle (10) remains in a passive mode, wherein the current pulses (50) are selected to be so short and occur at such a large time interval that an error suppression of the on-board electrical system classifies these current pulses as irrelevant and the vehicle (10) with its electrical consumers in the on-board electrical system is not activated.

2. Method according to claim 1, comprising at least the steps Determining the electrical voltages of the battery (40) and the energy source (12) by means of a control unit (20), wherein the control unit (20) is electrically coupled to the energy source (12) and the battery (40); If the electrical voltage of the battery (40) is lower than the electrical voltage of the energy source (12), checking whether a control pulse, in particular from a pulse generator (22), is present at the control unit (20); If the control pulse is present, switching through a switching element (24) by the control unit (20), which provides the current pulse (50) to the battery (40); checking whether the control pulse is switched off; If the control pulse is switched off, block the switching element (24).

3. Method according to claim 1 or 2, wherein the time duration (52) of the current pulse (50) and the time interval (54) of the current pulses (50) are set manually according to predeterminable parameters and / or are determined from a characteristic map of the vehicle (10) and / or are determined by measurements on the battery (40) and / or the energy source (12).

4. Method according to one of the preceding claims, wherein a solar module (14) is used as the energy source (12), wherein electrical energy generated by the solar module (14) is temporarily stored in an electrical buffer storage device (16).

5. The method of claim 4, further comprising Determining the electrical voltage of the buffer storage (16) by means of the control unit (20), wherein the control unit (20) is electrically coupled to the buffer storage (16) and the battery (40); If the electrical voltage of the buffer storage (16) is greater than the electrical voltage of the battery (40), check whether it is possible or permissible to provide the current pulse (50); If the provision of the current pulse (50) is possible or permissible, switching through the switching element (24) by the control unit (20), which provides the current pulse (50) to the battery (40); Check whether an end of the time duration (52) of the current pulse (50) has been reached; If the end of the time duration (52) of the current pulse (50) is reached, the switching element (24) is blocked.

6. Device (100) for maintaining the charge of a battery (40) of a vehicle (10) with a method according to one of the preceding claims, at least comprising an energy source (12) which, in normal operation, is electrically coupled to the battery (40) via a control unit (20), wherein the control unit (20) is configured to provide current pulses (50) of the energy source (12) with a predeterminable duration (52) in a predeterminable time interval (54) to the battery (40) and the control unit (20) comprises a pulse generator (22) or is electrically coupled to a pulse generator (22), characterized in that the pulse generator (22) is designed such that it can generate current pulses (50) with a time duration (52) and time interval (54), which are selected such that an on-board network of the vehicle (10) remains in a passive mode, wherein the current pulses (50) are selected so short and with such a large time interval Distance that an error suppression of the on-board network classifies these current pulses as irrelevant and the vehicle (10) with its electrical consumers in the on-board network is not activated.

7. Device according to claim 6, wherein the energy source (12) is designed as a solar module (14) with an electrical buffer storage (16), wherein the buffer storage (16) is designed for the intermediate storage of electrical energy of the solar module (14) generated in the solar module (14).

8. Device according to claim 7, characterized in that the electrical buffer storage (16) is designed as a capacitor, in particular as a supercapacitor, with a capacitance of at least 1 farad.

9. Device according to one of claims 6 to 8, wherein the control unit (20) for providing the current pulses (50) to the battery (40) is designed by controlling a switching element (24), in particular wherein the switching element (24) is designed as a semiconductor switching element, in particular as a transistor, in particular wherein the switching element (24) is designed to switch a negative electrical potential.

10. Device according to one of claims 6 to 9, wherein the energy source (12) is electrically coupled to the vehicle (10) via at least one electrical fuse (36).

11. Device according to one of claims 6 to 10, wherein the energy source (12) is electrically coupled to the vehicle (10) via an external start support point (70).

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