Method for controlling a charging or discharging operation of batteries connected electrically in parallel

Abstract

The invention relates to a method, in particular computer-implemented method, for controlling a charging or discharging operation of a first battery, in particular lithium-ion battery, and of a second battery, in particular lithium-ion battery, connected electrically in parallel with the first battery, in an on-board electrical system of a motor vehicle, wherein the charging or discharging of the first battery and of the second battery can be interrupted or activated separately from the other battery in each case, the method comprising the steps: (i) determining a first state of charge of the first battery; (a-i) comparing the first state of charge with a first reference value during charging of the first battery and of the second battery by means of an electrical energy source, in particular a generator; (a-ii) interrupting the charging of the first battery and continuing the charging of the second battery if the comparison indicates that the first state of charge is equal to the first reference value; or (b-i) comparing the first state of charge with a second reference value during discharging of the first battery; (b-ii) interrupting the discharging of the first battery and activating the discharging of the second battery if the comparison indicates that the first state of charge is lower than the second reference value.

Description

[0001] Method for controlling a charging or discharging process of batteries connected electrically in parallel

[0002] The present invention relates to a method, in particular a computer-implemented method, for controlling a charging or discharging process of batteries electrically connected in parallel, a battery device and a motor vehicle.

[0003] In the field of energy storage cells, especially battery cells, especially lithium-ion battery cells, cylindrical, prismatic, and pouch-shaped battery cells are the most common. Battery cells for storing electrical energy, in particular, play a central role in the field of electromobility, both in vehicles with purely electric drives and in vehicles or motor vehicles with hybrid drives. However, battery cells are also used in vehicles with combustion engines, for example, in a 12V starter battery.

[0004] Redundant energy sources are advantageous for safety-critical electrical consumers in a vehicle's electrical system or power system, for example, additional batteries in addition to the standard 12V starter battery. When connecting batteries in parallel, especially lithium-ion batteries with flat voltage curves, the different charge states, internal resistances, and electrical system impedances of these batteries can lead to different loads on the individual batteries, resulting in uneven aging.

[0005] To counteract the effect of uneven battery loading, an electrical converter is typically connected between the batteries. The disadvantages of the converter are increased manufacturing costs, additional weight for the vehicle, and heat generation in the installation space during operation.

[0006] The present invention is based on the object of enabling improved charging and discharging of batteries connected in parallel. This object is achieved according to the teaching of the independent claims. Various embodiments and developments of the present invention are the subject of the dependent claims.

[0007] A first aspect of the solution relates to a method, in particular a computer-implemented method, for controlling a charging or discharging process of a first battery, in particular a lithium-ion battery, and a second battery, in particular a lithium-ion battery, electrically connected in parallel thereto, of an on-board electrical system of a motor vehicle, wherein the charging or discharging of the first battery and the second battery can each be interrupted or enabled separately from the other battery, comprising the steps: (i) determining a first state of charge of the first battery; (ai) comparing the first state of charge with a first reference value during charging of the first battery and the second battery by an electrical energy source, in particular a generator; (a-ii) interrupting the charging of the first battery and continuing the charging of the second battery if the comparison has shown that the first state of charge is equal to the first reference value;or (bi) comparing the first state of charge with a second reference value during discharging of the first battery; (b-ii) interrupting the discharging of the first battery and enabling the discharging of the second battery if the comparison shows that the first state of charge is less than the second reference value.

[0008] The terms "comprises," "includes," "includes," "has," "has," "with," or any other variation thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a method or apparatus that includes or has a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or that are inherent in such a method or apparatus.

[0009] Furthermore, unless expressly stated to the contrary, "or" refers to an inclusive "or" and not an exclusive "or." For example, a condition A or B is satisfied by one of the following conditions: A is true (or present) and B is false (or absent), A is false (or absent) and B is true (or present), and both A and B are true (or present). The terms "a" or "an" as used herein are defined to mean "one or more." The terms "another" and "a further," and any other variations thereof, are defined to mean "at least one further."

[0010] The term "plurality" as used here is to be understood as meaning "two or more".

[0011] The term “configured” or “set up” to fulfil a specific function (and respective variations thereof) as used here is to be understood to mean that the corresponding device is already in a design or setting in which it can carry out the function or is at least adjustable - i.e. configurable - so that it can carry out the function after being set accordingly. The configuration can be carried out, for example, by appropriately setting parameters of a process sequence or of switches or similar for activating or deactivating functionalities or settings. In particular, the device can have a plurality of predetermined configurations or operating modes, so that the configuration can be carried out by selecting one of these configurations or operating modes.

[0012] The term “essentially equal” or “essentially equal” as used here means in particular that two values, in particular charge states of two batteries, do not differ from each other by more than 10%, in particular not more than 5%.

[0013] The term "battery," as used here, refers in particular to a rechargeable battery, in particular an accumulator. Such a rechargeable battery can, in particular, comprise a galvanic cell for storing chemical energy and releasing electrical energy. Such a battery can comprise an electrode stack with a plurality of plate-shaped elements, with at least two electrodes, namely an anode and a cathode, and a separator which can at least partially accommodate an electrolyte. Preferably, at least one anode, a separator, and a cathode are superimposed or stacked, with the separator being arranged at least partially between the anode and cathode. This sequence of anode, separator, and cathode can be repeated as often as desired within the electrode stack. The plate-shaped elements can preferably be wound into an electrode coil.Before electrical energy is released, stored chemical energy is converted into electrical energy. During charging, the electrical energy supplied to the electrode stack is converted into chemical energy and stored. The electrodes can have a current collector, particularly made of aluminum for the cathode and copper for the anode. A thin layer of a mixture of an active material, binder (e.g., PVDF, PTFE, CMC, SBR, LiPAA, PAA, etc.), and conductive additives (carbon black, CNTs, carbon fibers, etc.) can be applied to both sides of the current collector.

[0014] The term “charging”, in particular “charging a battery” as used here, means in particular that electrical energy is supplied to a rechargeable battery, this is converted into chemical energy in the battery and stored, and this can be made available to an electrical consumer as electrical energy.

[0015] The term “discharging”, in particular “discharging a battery”, as used here, is understood to mean in particular the release or transfer of electrical energy from a battery to an electrical consumer.

[0016] The term “MOSFET” or (English: metal-oxide-semiconductor field-effect transistor), as used here, refers in particular to a metal-oxide-semiconductor field-effect transistor.

[0017] The method according to the first aspect according to alternative (a) can ensure that charging of the first battery is interrupted when the detected first state of charge is equal to the first reference value. This is because, in the event that the first battery and the second battery do not have the same state of charge - for example, the state of charge of the first battery may be more advanced than the state of charge of the second battery, in particular due to different voltage drops - the first battery will reach its maximum state of charge before the second battery. Since the batteries connected in parallel are not yet fully charged in this case, the charging process continues. By interrupting the charging process of the first battery in a timely manner, i.e. when the reference value of the state of charge is reached, damage to the first battery due to overcharging can be avoided.

[0018] The method according to the first aspect according to alternative (b) can ensure that, if the first state of charge of the first battery falls below a second reference value, discharging of the first battery is interrupted and discharging of the second battery is enabled. This ensures that a vehicle's electrical system, which is to be powered by the first battery, can continue to be supplied with electrical energy even if the state of charge of the first battery falls below the reference value.

[0019] The present process also eliminates the need for a converter between the batteries. The disadvantages associated with an additional converter, such as increased manufacturing costs, additional weight for the vehicle, and the operation of heat generation in the installation space, can be avoided.

[0020] Preferred embodiments of the method are described below, which can be combined with each other as well as with the other aspects described, unless this is expressly excluded or is technically impossible.

[0021] In some embodiments, according to alternative (a), the charging process of the first battery is interrupted if a second charge level of the second battery was determined as the first reference value, and the comparison has shown that the first charge level is greater than the second charge level. This allows the second charge level to be adjusted to the first charge level after the interruption.

[0022] In some embodiments, according to alternative (a), the interruption of the charging process of the first battery is terminated when the first state of charge is substantially equal to the second state of charge. This can prevent the state of charge of the second battery from becoming greater than the state of charge of the first battery. This would in turn lead to uneven charging of the batteries. In some embodiments, according to alternative (a), the first reference value corresponds to a maximum state of charge of the first battery. This can prevent the first battery from being charged to the maximum state of charge, thereby preventing overcharging and thus damage to the first battery.

[0023] In some embodiments, according to alternative (b), the discharging of the first battery is interrupted when a detected voltage value of the first battery is less than a predetermined threshold. A voltage value can be easily determined, and the ability to interrupt charging due to a voltage value that is too low, which is below the threshold, can improve the overall reliability of determining the need to interrupt discharging of the first battery.

[0024] A second aspect of the solution relates to a battery device, wherein the battery device is configured to carry out the method according to the first aspect.

[0025] Preferred embodiments of the battery device are described below, which can be combined with each other as well as with the other aspects described, unless this is expressly excluded or is technically impossible.

[0026] In some embodiments, the battery device comprises: (i) a first battery, in particular a lithium-ion battery, with a first separation module that is configured to interrupt and enable charging and discharging of the first battery, respectively; (ii) a second battery, in particular a lithium-ion battery, with a second separation module that is configured to interrupt and enable charging and discharging of the second battery, respectively; (iii) wherein the first battery and the second battery are electrically connected in parallel to one another; (iv) a detection device that is configured to detect a first state of charge of the first battery and a second state of charge of the second battery;(v) a control device which is configured: (ai) to compare the first state of charge with a first reference value during charging of the first battery and the second battery by an electrical energy source, in particular a generator, and (a-ii) to interrupt the charging of the first battery using the first separation module and to continue the charging of the second battery using the second separation module if the comparison has shown that the first state of charge is equal to the first reference value;or (bi) during discharging of the first battery, comparing the first state of charge with a second reference value and interrupting the discharging of the first battery using the first separation module, and (b-ii) discharging the second battery using the second separation module if the comparison has shown that the first state of charge is less than the second reference value;

[0027] In some embodiments, the first separation module comprises a first charging separation element, in particular a first MOSFET, which is configured to interrupt and enable charging of the first battery. Furthermore, the first separation module comprises a first discharging separation element, in particular a second MOSFET, which can interrupt and enable discharging of the first battery. The first charging separation element and the first discharging separation element make it possible to interrupt and enable charging separately from discharging and separately from the second battery.

[0028] In some embodiments, the second separation module comprises a second charging separation element, in particular a third MOSFET, which is configured to interrupt and enable charging of the second battery. Furthermore, the second separation module comprises a second discharging separation element, in particular a fourth MOSFET, which can interrupt and enable discharging of the second battery. The second charging separation element and the second discharging separation element make it possible to interrupt and enable charging separately from discharging and separately from the first battery.

[0029] In embodiments in which the battery device has the first separation module and the second separation module, optimization can be achieved during the separate charging and discharging of the respective batteries, since charging and discharging can be interrupted and reactivated separately for each of the first battery and the second battery. This can be adapted according to the state of the other battery and / or the requirements of the vehicle electrical system. A third aspect of the solution relates to a motor vehicle with a battery device according to the second aspect. In particular, the motor vehicle can have an electric drive, a hybrid drive, or an internal combustion engine.

[0030] The features and advantages explained with regard to the first aspect of the solution also apply accordingly to the other aspects described.

[0031] Further advantages, features and possible applications emerge from the following description of preferred embodiments in conjunction with the figures.

[0032] This shows

[0033] Fig. 1 schematically shows a battery device in an on-board power system according to an embodiment; and

[0034] Fig. 2 schematically shows a flow diagram to illustrate an embodiment of a method.

[0035] Throughout the figures, the same reference numerals are used for the same or corresponding elements.

[0036] Fig. 1 schematically shows a battery device 100 in an on-board power system 105 according to an embodiment.

[0037] The on-board electrical system 105 has a first on-board electrical system 160, a second on-board electrical system 170, an electrical energy source 150, which can be an alternator of a vehicle or a high-voltage converter, and the battery device 100.

[0038] The battery device 100 has a primary battery 110 with a first separation module 115, which has two MOSFETs 120, 125, and a secondary battery 130 with a second separation module 135, which has two further MOSFETs 140, 145. The primary battery 110 and the secondary battery 130 can be charged by the electrical energy source 150, so that the primary battery 110 and the secondary battery 130 can each provide electrical energy for consumers connected to them or for an associated vehicle electrical system 160, 170. The primary battery 110 can supply a primary vehicle electrical system 160 with electrical energy, and the secondary battery 130 can supply a secondary vehicle electrical system 170 with electrical energy. Furthermore, the primary battery 110 and the secondary battery 130 are electrically connected in parallel with one another.

[0039] In the on-board power system 105, impedances arise due to the arrangement and the electrical lines, which are schematically represented as Z1, Z3, and Z4. This applies to Z1 between the electrical energy source 150 and the primary battery 110, Z3 between the electrical energy source 150 and the primary on-board power system 160, and Z4 between the electrical energy source 150 and the secondary on-board power system 170. Furthermore, a disconnecting device Z2 is arranged between the electrical energy source 150 and the secondary battery 130, whereby independence from the on-board power system can be ensured in the event of a fault.

[0040] The MOSFETs 120, 125 of the primary battery and the MOSFETs 140, 145 of the secondary battery each act as a separating element, whereby a current supply can be separated or interrupted from the respective battery 110, 130 during a charging process or current discharge to a consumer in order to protect the respective battery 110, 130 from damage.

[0041] During a charging process of the primary battery and the secondary battery, it may happen that a state of charge, also known as “state of charge” (SOC), of the primary battery 110 is greater than the state of charge of the secondary battery 130.

[0042] Since these MOSFETs 120, 125, 140, 145 have an internal diode (body diode) due to the technology, separate MOSFETs 120, 125, 140, 145 are required to separate the charging and discharging directions. Therefore, both the primary battery 110 and the secondary battery 130 each have two MOSFETs 120, 125, 140, 145. For the primary battery 110, MOSFET 120 controls the charging direction, and MOSFET 125 controls the discharging direction. For the secondary battery 130, MOSFET 140 controls the charging direction, and MOSFET 145 controls the discharging direction. Likewise, several MOSFETs can be connected in parallel in each of the batteries 110, 130 to increase current-carrying capacity. In an operating strategy of the battery device 100 in which the charging direction of the secondary battery 130 is kept separate, the primary battery 110 can be charged to a required charge state independently of an on-board network load and an on-board network impedance of the primary on-board network 160.The charge states of the first battery 110 and the second battery 130 are detected by a detection device 180 and forwarded to a control device 190 of the battery device 100. A measuring device (not shown here) for measuring or determining electrical parameters, such as current, voltage, and state of charge, can be integrated into each of the first battery 110 and the second battery 130. These measured parameters can then be detected or read out by the detection device.

[0043] Discharge also occurs from the primary battery 110, as long as it has a capacity that allows the required vehicle electrical system voltage of the primary vehicle electrical system 160 to be maintained stable. If this vehicle electrical system voltage drops, e.g., due to an increased vehicle electrical system load on the primary vehicle electrical system 160 or if the available electrical power or electrical energy of the primary battery 110 is too low for the primary vehicle electrical system 160, a forward voltage of the diode of the open MOSFET 140 of the secondary battery 130 is reached, and a discharge current can flow from the secondary battery 130, thus supporting the primary vehicle electrical system 160 without interruption.

[0044] In the present embodiment, the primary battery 110, preferably with cycle stability, is provided with sufficient capacity to supply the first vehicle electrical system 110. The secondary battery 130 is operated with an open charging isolating element, MOSFET 140, and is thus maintained at a current charge level.

[0045] The on-board electrical system voltage of the primary electrical system 160 is regulated by the control device 190 such that the primary battery 110 is charged by the electrical energy source 150 and maintained at this charge level, which is also known as a "balance-hold strategy." In this state, the primary battery 110 can buffer energy (in the charging and discharging direction). If the voltage in the primary electrical system 160 drops, i.e., reduces due to excessive load (dynamics), and the primary battery 110 ultimately cannot provide sufficient available electrical power or electrical energy for the primary electrical system 160, a current flows through a diode of the MOSFET 140 of the secondary battery 130. This flowing current leads to a power loss at the charging isolating element, MOSFET 140, of the secondary battery 130.If this power loss exceeds a predetermined reference value, the charging and disconnecting element, MOSFET 140, is closed to minimize the power loss. When the discharge current of the secondary battery 130 has decreased, the charging and disconnecting element, MOSFET 140, of the secondary battery 130 is opened again.

[0046] In order to charge the secondary battery 130 and to ensure the correct state of charge for sufficient buffer capacity (in the discharge direction), two cases can be distinguished:

[0047] In a first case, the secondary battery 130 has a lower state of charge than the primary battery 110. In this state, the charging isolating element, MOSFET 120, of the primary battery 110 is opened, and within a short time, for example, 100 ms, the charging isolating element, MOSFET 140, of the secondary battery 130 is closed. Using the control device 190, the secondary battery 130 is charged to a target state of charge. As soon as the charge states of the primary battery 110 and the secondary battery 130 have equalized, the charging isolating element, MOSFET 120, of the primary battery 110 is closed. A brief equalizing current can still flow between the primary battery 110 and the secondary battery 130. Subsequently, the primary battery 110 and the secondary battery 130 are charged in parallel or simultaneously.Once the secondary battery 130 has reached a target charge level, its charge isolation element, MOSFET 140, is opened and the secondary battery 130 then remains in this state.

[0048] In a second case, the secondary battery 130 has a higher charge level than the primary battery 110. In this case, the primary battery 110 is charged until both charge levels are equal. In this state, the charging isolation element, MOSFET 140, of the secondary battery 130 is closed, and the secondary battery 130 is also charged until it reaches a desired charge level. Subsequently, the charging isolation element, MOSFET 140, is opened again, and the secondary battery 130 remains in this state.

[0049] Fig. 2 schematically shows a flow chart 200 for illustrating an embodiment of a method for controlling a charging or discharging process of a first battery 110, in particular a lithium-ion battery, and a second battery 130, in particular a lithium-ion battery of an on-board electrical system of a vehicle, which is electrically connected in parallel thereto, wherein the charging or discharging of the first battery 110 and the second battery 130 can each be interrupted or enabled separately from the other battery.

[0050] In a first step S210 of the method, a first state of charge of the first battery 110 is determined. To determine the state of charge, for example, a current measurement can be performed at a reference resistor, also known as a "shunt," with the current measurement being integrated over time. This can be done using a charge counter. In addition, a voltage of the first battery 110 is measured, and a current capacity is estimated. The determined state of charge can then be transmitted, in particular via a detection device 180, to a control device 190, as described for Fig. 1.

[0051] According to a first alternative (a), in a further step S220 of the method, the first state of charge is compared with a first reference value during charging of the first battery 110 and the second battery 130 by a generator, in particular an alternator of the vehicle or motor vehicle.

[0052] In a further step S230 of the method according to alternative (a), the charging of the first battery 110 is interrupted and the charging of the second battery 130 is continued if the comparison has shown that the first state of charge is equal to the first reference value.

[0053] According to a second alternative (b), in a further step S240, the first state of charge is compared with a second reference value during discharging of the first battery 110. In a further step S250 of the method according to alternative (b), the discharging of the first battery 110 is interrupted and the discharging of the second battery 130 is enabled if the comparison has shown that the first state of charge is less than a second reference value.

[0054] For steps S220 to S250, in particular, a control device 190 as described in Fig. 1 can be used.

[0055] While at least one exemplary embodiment has been described above, it should be appreciated that a wide variety of variations exist. It should also be understood that the described exemplary embodiments are merely non-limiting examples and are not intended to limit the scope, applicability, or configuration of the devices and methods described herein. Rather, the foregoing description will provide one skilled in the art with guidance for implementing at least one exemplary embodiment, it being understood that various changes in the operation and arrangement of the elements described in an exemplary embodiment may be made without departing from the subject matter as defined in the appended claims, as well as their legal equivalents.

[0056] LIST OF REFERENCE SYMBOLS

[0057] 100 Battery device

[0058] 105 On-board power system

[0059] 110 Primary Battery

[0060] 115 First separation module

[0061] 120, 125 MOSFET

[0062] 130 Secondary battery

[0063] 135 Second separation module

[0064] 140, 145 MOSFET

[0065] 150 Electrical energy source

[0066] 160 Primary electrical system

[0067] 170 Secondary electrical system

[0068] 180 Recording device

[0069] 190 Control device

[0070] Z1-Z4 Zener diode

[0071] 200 Flowchart

[0072] S210 Determine first state of charge

[0073] S220 Compare first state of charge with first reference value

[0074] S230 Interrupt charging of first battery

[0075] S240 Compare first state of charge with second reference value

[0076] S250 Interrupt charging of second battery

Claims

CLAIMS 1 . A method for controlling a charging or discharging process of a first battery (110) and a second battery (130) of an on-board power supply (160) of a motor vehicle, said method comprising the steps of: Determining a first state of charge of the first battery (110); (a) comparing the first state of charge with a first reference value during charging of the first battery (110) and the second battery (130) by an electrical energy source (150); interrupting the charging of the first battery (110) and continuing the charging of the second battery (130) if the comparison has shown that the first state of charge is equal to the first reference value; or (b) comparing the first state of charge with a second reference value during discharging of the first battery (110); interrupting the discharging of the first battery (110) and enabling the discharging of the second battery (130) if the comparison shows that the first state of charge is less than a second reference value.

2. The method according to claim 1, wherein according to alternative (a) the interruption of the charging process of the first battery (110) occurs when a second charge state of the second battery (130) was determined as the first reference value, and the comparison has shown that the first charge state is greater than the second charge state.

3. The method according to claim 1 or 2, wherein according to alternative (a) the interruption of the charging process of the first battery (110) is terminated when the first state of charge is substantially equal to the second state of charge.

4. Method according to one of the preceding claims, wherein according to alternative (a) the first reference value corresponds to a maximum state of charge of the first battery (110).

5. Method according to one of the preceding claims, wherein according to alternative (b) the discharging of the first battery (110) is interrupted if a detected voltage value of the first battery (110) is less than a predetermined threshold value.

6. Battery device (100) configured to carry out the method according to any one of the preceding claims.

7. Battery device (100) according to claim 6, comprising: A first battery having a first separation module (115) configured to interrupt and enable charging and discharging of the first battery (110), respectively; A second battery with a second separation module (135) configured to interrupt and enable charging and discharging of the second battery (130), respectively; wherein the first battery (110) and the second battery (130) are electrically connected in parallel with each other; a detection device (180) configured to detect a first charge state of the first battery (110) and a second charge state of the second battery (130); a control device (190) configured to: (a) during charging of the first battery (110) and the second battery (130) by an electrical energy source (150), comparing the first state of charge with a first reference value, and interrupting the charging of the first battery (110) using the first separation module (115) and continuing the charging of the second battery (135) using the second separation module (135) if the comparison has shown that the first state of charge is equal to the first reference value, or (b) during discharging of the first battery (110), comparing the first state of charge with a second reference value, and interrupting the discharging of the first battery (110) using the first separation module, and discharging the second battery using of the second separation module if the comparison has shown that the first state of charge is less than the second reference value.

8. Battery device (100) according to claim 7, wherein the first separation module (115) has a first charging separation element (120) which is configured to be able to interrupt and enable charging of the first battery (110), and a first discharging separation element (125) which can interrupt and enable discharging of the first battery (110).

9. Battery device (100) according to one of claims 6 to 8, wherein the second separation module (135) has a second charging separation element (140) which is configured to be able to interrupt and enable charging of the second battery (130), and a second discharging separation element (145) which is configured to be able to interrupt and enable discharging of the second battery (130).

10. Motor vehicle with a battery device (100) according to one of claims 6 to 9.

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