Method for charging a vehicle battery and electrical system of a vehicle

Abstract

A vehicle contains an electrical system that performs a method for charging the vehicle's battery. The electrical system comprises the battery, an inverter connected to the battery via a positive bus line, a first contactor within the inverter connecting the battery to the inverter via the positive bus line, a charging port for connecting the positive bus line to a charging station to receive a base charging current from the charging station, a diode to prevent reverse current from the electrical system to the charging station, and a processor. The processor is configured to control the first contactor to generate a ripple current in the positive bus line, which is superimposed on the base charging current to obtain a combined charging current. This combined charging current is then used to charge the battery.

Description

[0001] The subject of the description relates to the charging of electric vehicles and in particular to a system and method for improving charging speed.

[0002] Electric vehicles need to be charged at regular intervals to replenish their batteries. The charging process generally involves a constant current phase followed by a constant voltage phase. The constant voltage phase can take an undesirably long time. Particularly with lithium-ion batteries, the charging speed is limited by the occurrence of lithium plating, especially at low temperatures. Pulse charging has been shown to improve charging speeds. However, this requires either the generation of a ripple current by the charging source (which may or may not be equipped to generate ripple current) or the installation of additional hardware in the vehicle.

[0003] US 2024 / 0186811A1 describes a vehicle charging system comprising a propulsion system inverter, wherein the inverter is connected to an electric motor and a vehicle battery system, and a switching arrangement containing multiple switches. The charging system includes a controller configured to control the switching arrangement to connect the inverter and the electric motor to a vehicle charging port, and a conversion circuit containing one or more inverter switches and the electric motor, by selectively connecting the charging port to the inverter or the electric motor and selectively connecting the battery system to the electric motor through the switching arrangement.The controller is configured to operate the conversion circuit to set at least one input voltage for charging the battery system from a power source and one output voltage for discharging the battery system to charge an external energy storage system.

[0004] JP 2019 - 165 522 A describes the heating of a storage battery connected to a main circuit. In this process, a ripple current control unit in an inverter control system generates a reactive current setpoint with an amplitude and a reactive current waveform for an overhead line voltage that corresponds to a storage battery ripple current RMS value. This is done to reduce ripple components, which are constituents of a storage battery current, by superimposing it with an inverter current in an inverter control unit.

[0005] JP 2013-30351A describes the heating of a power storage device during external charging in an externally chargeable vehicle. A charger for charging an in-vehicle energy storage system from an external power source includes a DC-DC converter and a control unit. When the energy storage system's temperature is low, the control unit generates a current setpoint to superimpose the AC waveform onto the charger's DC output current and controls switching elements in an inverter contained within the DC-DC converter based on this current setpoint. The energy storage system is heated by the AC waveform superimposed on the DC output current.

[0006] In "Sensorless on-board cell temperature control for fast charging," SAE technical papers, 2019, pp. 1-11, Haussmann and Melbert describe a combined current and thermal management strategy for fast charging electric vehicles. Here, the cell temperature is determined sensorlessly via cell impedance, whereby an excitation current is superimposed in a charging profile and the resulting voltages are evaluated.

[0007] The task can be considered to be to specify a method and a system to generate a ripple current using existing circuits of the vehicle.

[0008] The problem is solved by a method according to claim 1 and a system according to claim 5. Furthermore, a vehicle is described wherein the system according to the invention is arranged in the vehicle.

[0009] A method according to the invention for charging a vehicle battery is described. A base charging current is received from a charging station connected to the vehicle's electrical system, which comprises the battery, an inverter, and a positive bus line connecting the battery to the inverter and the battery to the charging station. The inverter includes a first contactor connecting the battery and the inverter via the positive bus line. The first contactor is controlled to generate a ripple current on the positive bus line. This ripple current is superimposed on the base charging current to obtain a combined charging current. The battery is then charged via this combined charging current.The electrical system includes a second contactor between the positive bus line and a midpoint of a branch of the inverter, further comprising the control of the first contactor and the second contactor to generate the ripple current.

[0010] In one embodiment, a charging process includes a constant current phase, wherein the method further includes charging the battery using the combined charging current during the constant current phase.

[0011] In one embodiment, a charging process comprises a constant current phase and a constant voltage phase, wherein the method further comprises charging the battery using the combined charging current to shorten the duration of the constant voltage phase.

[0012] In one embodiment, the method further comprises controlling an amplitude of the ripple current in order to perform at least one of the following: preventing plating from occurring on the battery and heating the battery.

[0013] In one embodiment, the method further includes applying heat to the battery via at least one external heat source or the ripple current.

[0014] In one embodiment, the method further comprises providing the base charging current at a first power, superimposing the ripple current over the base charging current to generate the combined charging current with the first power, and increasing the combined charging current from the first power to a second power that is greater than the first power.

[0015] An electrical system according to the invention for a vehicle is described. The electrical system comprises a battery, an inverter coupled to the battery via a positive bus line, a first contactor within the inverter that connects the battery to the inverter via the positive bus line, a charging port for connecting the positive bus line to a charging station to receive a base charging current from the charging station, and a processor. The processor is configured to control the first contactor to generate a ripple current in the positive bus line, wherein the ripple current is superimposed on the base charging current to obtain a combined charging current for charging the battery.The electrical system includes a second contactor between the positive bus line and a midpoint of a branch of the inverter, further comprising the control of the first contactor and the second contactor to generate the ripple current.

[0016] In one embodiment, a charging process includes a constant current phase and the processor is further configured to charge the battery using the combined charging current during the constant current phase.

[0017] In one embodiment, a charging process comprises a constant current phase and a constant voltage phase, and the processor is further configured to charge the battery using the combined charging current in order to shorten the duration of the constant voltage phase.

[0018] In one embodiment, the processor is further designed to control the amplitude of the ripple current in order to prevent at least one of the following: suppression and occurrence of plating on the battery and heating of the battery.

[0019] In one embodiment, heat is supplied to the battery via at least one external heat source or the ripple current.

[0020] In one embodiment, the processor is further designed to provide the base charging current at a first power, to superimpose the ripple current on top of the base charging current to generate the combined charging current at the first power, and to increase the combined charging current from the first power to a second power that is greater than the first power.

[0021] A vehicle is described. The vehicle contains the electrical system according to the invention.

[0022] Further features, advantages and details are mentioned only as examples in the following detailed description, which refers to the drawings in which: Fig. Figure 1 shows an embodiment of a vehicle; Fig. Figure 2 shows an electrical system of the vehicle from Fig. 1; Fig. Figure 3 shows a circuit to illustrate a charging process for the vehicle; Fig. Figure 4 shows a diagram illustrating the relationship between current and time during a charging process; Fig. 5 is a diagram illustrating the relationship between charging current and state of charge for different charging processes; Fig. Figure 6 is a diagram of an electrical system with multiple inverters and motors; Fig. Figure 7 shows a diagram of the charging power over time; Fig. Figure 8 shows a diagram of the state of charge (SOC) over time; Fig. Figure 9 is a diagram showing a low-amplitude ripple current that can be used for charging; Fig. 10 is a diagram showing a medium-amplitude ripple current that can be used for charging; Fig. Figure 11 is a diagram showing a high-amplitude ripple current that can be used for charging; Fig. 12 is a diagram showing a heating and pulse charging strategy; Fig. Figure 13 is a diagram showing the charging power for different charging methods for a cold battery; and Fig. Figure 14 is a diagram showing the battery temperatures for different charging methods with a cold battery.

[0023] In accordance with an exemplary embodiment, it shows Fig. 1 An embodiment of a vehicle 10 comprising a vehicle body 12 which at least partially defines a passenger compartment 14. The vehicle body 12 also carries various vehicle subsystems, including a drive system 16 and other subsystems for supporting the functions of the drive system 16 and other vehicle components, such as a brake subsystem, a suspension system, a steering subsystem, and others.

[0024] The vehicle 10 can be an electric vehicle (EV), a hybrid vehicle, or another type of vehicle. In one embodiment, the vehicle 10 is an electric vehicle comprising multiple motors and / or drive systems. It can include any number of drive units, such as one or more drive units that apply torque to the front wheels (not shown) and / or the rear wheels (not shown). The drive units are controllable so that the vehicle 10 can operate in various modes, such as a normal mode, a high-performance mode (in which additional torque is applied), all-wheel drive (AWD), front-wheel drive (FWD), rear-wheel drive (RWD), and others.

[0025] The drive system 16, for example, is a multi-drive system comprising a front drive unit 20 for driving the front wheels and rear drive units for driving the rear wheels. The front drive unit 20 includes a front electric motor 22 and a front inverter 24 (e.g., a front power inverter module or FPIM), as well as other components such as a cooling system. A left rear drive unit 30L includes a left rear electric motor 32L and a left rear inverter 34L. A right rear drive unit 30R includes a right rear electric motor 32R and a right rear inverter 34R. The front inverter 24, the left rear inverter 34L, and the right rear inverter 34R (e.g., power inverter units or PIMs) each convert direct current (DC) from a high-voltage battery system 40 into multiphase (e.g.,two-phase, three-phase, six-phase, etc.) alternating current (AC) to power the front electric motor 22, the left rear electric motor 32L and the right rear electric motor 32R.

[0026] As in Fig. As shown in Figure 1, the drive systems are equipped with separate electric motors. However, the embodiments are not limited to this. Instead of separate motors, for example, several drives can be provided by a single machine that has multiple sets of windings that are physically independent.

[0027] As also in Fig. As shown in Figure 1, the drive systems are configured such that the front electric motor 22 drives the front wheels (not shown), and the left rear electric motor 32L and the right rear electric motor 32R drive the rear wheels (not shown). However, the embodiments are not limited in this way, as there can be any number of drive systems and / or motors at different locations (e.g., one motor driving each wheel, two motors per axle, etc.). Furthermore, the embodiments are not limited to a dual drive system, as they can be used with a vehicle that has any number of motors and / or power inverters.

[0028] In the drive system 16, the front drive unit 20, the left rear drive unit 30L, and the right rear drive unit 30R are electrically connected to the battery system 40. The battery system 40 can also be electrically connected to other electrical components (also called "electrical consumers"), such as the vehicle electronics (e.g., via an auxiliary power module - APM 42), heating systems, cooling systems, and others. The battery system 40 can be configured as a rechargeable energy storage system (RESS).

[0029] In one embodiment, the battery system 40 comprises a plurality of separate battery assemblies, each of which can be charged independently and used to independently power one or more drive systems. For example, the battery system 40 comprises a first battery arrangement, such as a first battery pack 44 connected to the front inverter 24, and a second battery pack 46. The first battery pack 44 comprises a first plurality of battery modules 48, and the second battery pack 46 comprises a second plurality of battery modules 50. Each of the first plurality of battery modules 48 and the second plurality of battery modules 50 comprises a number of individual cells (not shown).

[0030] Each of the front electric motors 22, the left rear electric motor 32L, and the right rear electric motor 32R is a three-phase motor with three-phase motor windings. However, the embodiments described here are not limited to these. For example, the motors can be any multi-phase machines powered by multi-phase inverters, and the drive units can be implemented with a single machine with independent winding sets.

[0031] The battery system 40 and / or the drive system 16 comprises a switching system with various switching devices for controlling the operation of the first battery pack 44 and the second battery pack 46, as well as for selectively connecting the first battery pack 44 and the second battery pack 46 to the front drive unit 20, the left rear drive unit 30L, and the right rear drive unit 30R. The switching devices can also be actuated to selectively connect the first battery pack 44 and the second battery pack 46 to a charging system. The charging system can be used to charge the first battery pack 44 and the second battery pack 46 and / or to provide power from the first battery pack 44 and / or the second battery pack 46 to charge another energy storage system (e.g., vehicle-to-vehicle (V2V) and / or vehicle-to-everything (V2X) charging). The charging system comprises one or more charging modules.For example, a first onboard charging module (OBCM) 52 is electrically connected to a charging port 54 for charging with an AC system or device, e.g., an AC power supply. A second OBCM 53 can be provided for DC charging (e.g., DC fast charging or DCFC). However, in various embodiments, no OBCM is required for DC fast charging.

[0032] The first OBCM 52 and / or the second OBCM 53 can be connected to an electric charging station 70 via a power cable 72 for charging the vehicle 10.

[0033] In one embodiment, the switching system comprises a first switching device 60 that selectively connects the first battery pack 44 to the front inverter 24, the left rear inverter 34L, and the right rear inverter 34R, and a second switching device 62 that selectively connects the second battery pack 46 to the front inverter 24, the left rear inverter 34L, and the right rear inverter 34R. The switching system also includes a third switching device 64 (also referred to as the "battery switching device") for selectively connecting the first battery pack 44 to the second battery pack 46 in series.

[0034] Various controllers can be used to control the functions of the battery system 40, the switching system, and the drive units. A controller comprises any suitable processing device or unit and may utilize an existing controller, such as a drive system controller, a RESS controller, and / or controllers within the drive system. For example, a controller 65 may be included for controlling switching and drive control operations as described herein.

[0035] The controller 65 may include processing circuitry that may comprise an application-specific integrated circuit (ASIC), an electronic circuit, a processor (common, dedicated, or group), and memory executing one or more software or firmware programs, a combinational logic circuit, and / or other suitable components that provide the described functionality. The controller 65 may include a non-transient, computer-readable medium that stores instructions which, when processed by one or more processors of the controller 65, implement a method for performing a pulse charge of a vehicle battery using components of the vehicle's electrical system according to one or more embodiments described herein.

[0036] The vehicle 10 also includes a computer system 55, which comprises one or more processing units 56 and a user interface 58. The computer system 55 can, for example, communicate with the charging system controller to issue commands to it in response to user input. The various processing units, modules, and components can communicate with each other via a communication device or system, such as a Controller Area Network (CAN) or Transmission Control Protocol (TCP) bus.

[0037] Fig. Figure 2 shows an electrical system 200 of vehicle 10 of Fig. Figure 1 in an illustrative embodiment. The electrical system 200 comprises a direct current source (e.g., a battery 202), an inverter 204 that converts the direct current from the battery 202 into alternating current, and an electric motor 206 that operates on the alternating current. The electric motor 206 is generally a three-phase motor. The inverter 204 comprises at least three branches (a first branch 208a, a second branch 208b, and a third branch 208c) that are phase-shifted by approximately 120 degrees relative to each other. Each branch contains a pair of switches that controls the conversion of direct current to alternating current along the branch. The first branch 208a comprises switches Q1 and Q2. The second branch 208b comprises switches Q3 and Q4. The third branch 208c comprises switches Q5 and Q6. In one embodiment, a switch comprises a transistor with a diode extending from the source of the transistor to the drain of the transistor.A gate voltage can be applied to the gate of the transistor to control the current flow through it. The transistor can be an insulated-gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), or another suitable transistor.

[0038] The battery 202 is connected to the inverter via a positive bus line 210 and a negative bus line 212.

[0039] Fig. Figure 3 shows a circuit 300 illustrating a charging process for the vehicle in one embodiment. The circuit 300 comprises the electric charging station 70 and the electrical system 200. The battery 202 and the inverter 204 of the electrical system 200 are shown.

[0040] A first contactor S1 controls a connection along the positive bus line 210 between the battery 202 and the inverter 204. A second contactor S2 controls a connection between the positive bus line 210 and a midpoint along the first branch 208a between switches Q1 and Q2. A third contactor S3 and a fourth contactor S4 control an electrical connection between the battery 202 and the inverter along the positive bus line 210 during a pre-charging sequence of a charging process. The control unit 65 can be used to control the operations of the first contactor S1, the second contactor S2, the third contactor S3, and the fourth contactor S4.

[0041] The electric charging station 70 comprises a positive DC fast charging port (positive DCFC port 302) and a negative DC fast charging port (negative DCFC port 304). A positive bus charging contactor S5 controls a connection between the positive bus line 210 and the positive DCFC port 302, and a negative bus charging contactor S6 controls a connection between the negative bus line 212 and the negative DCFC port 304. A first diode D1 is arranged on the positive bus line 210. A second diode D2 is arranged on the negative bus line 212. The orientations of the first diode D1 and the second diode D2 are chosen to prevent backflow of current from the vehicle into the electric charging station 70.

[0042] The electric charging station 70 charges the vehicle in two phases: a constant current phase and a constant voltage phase that follows the constant current phase. During the constant current phase, a DCFC base charging current is supplied to the battery 202. The first contactor S1 and the second contactor S2 can be controlled to generate a ripple current within the base charging current. This ripple current is superimposed on the base charging current to form a combined charging current. The combined charging current is used to charge the battery and reduces the charging time (increases the charging power). The ripple current is generated by controlling the first contactor S1 and the second contactor S2, as well as switches Q1 and Q2. The ripple current can be a sinusoidal current.

[0043] Since the first contactor S1, the second contactor S2, the first diode D1, and the second diode D2 are part of the electrical system, no additional circuitry is required to generate the ripple current. Specifically, the first contactor S1 and the second contactor S2 are part of the inverter 204.

[0044] Fig. Figure 4 shows a diagram 400 illustrating the relationship between current and time during a charging process. Time is shown along the abscissa in seconds (s) and current along the ordinate in amperes (A). Graph 400 shows the base charging current 402 and a ripple current profile 404. The RMS pulse charging current 406 represents the effective value of the combined charging current. The RMS pulse charging current 406 is greater than the base charging current 402 due to a relaxed lithium plating limit. Thus, the RMS pulse charging current 406 enables faster battery charging compared to charging with the base charging current 402.

[0045] Fig. Figure 5 is a diagram 500 that illustrates the relationship between charging current and state of charge for various charging processes. Time (t) is shown on the abscissa and the RMS current (A) on the ordinate axis. A first curve 502 represents the current during a standard DCFC charge with a base charging current (without added ripple current), and a second curve 504 represents the current during a DCFC pulse charge (ripple current superimposed on a base charging current). The first curve 502 shows a baseline constant current phase 506 (at an initial power input), followed by a baseline constant current phase 508. The baseline constant current phase 506 lasts until the first phase transition time 510 (at t1), after which the baseline constant current phase 508 is used to charge the battery 202.

[0046] The second curve 504 shows a pulsed constant current phase 512 (with a second power input), followed by a pulsed constant voltage phase 514. The pulsed constant current phase 512 lasts until the second phase transition time 516 (t2), after which the pulsed constant voltage phase 514 begins. The second phase transition time 516 occurs later than the first phase transition time 510 because the ripple current applied during the pulsed constant current phase 512 charges more effectively than the baseline constant current phase 506. Furthermore, the pulsed RMS current during the pulsed constant current phase 512 is greater than the baseline charging current during the baseline constant current phase 506. During each charging cycle, the charging current decays during the pulsed constant current phase. The extent of the decay of the charging current in the pulsed constant current phase 514 is less than the extent of the decay of the charging current during the base charging constant current phase 508.This difference is due to the fact that the second phase transition time 516 occurs later than the first phase transition time 510. Therefore, the duration of the pulsed constant voltage phase 514 is shorter than the duration of the baseline constant voltage phase 508. Thus, less time is available for decay in the pulsed constant voltage phase 514 than in the baseline constant voltage phase 508.

[0047] Fig. Figure 6 is a diagram 600 of an electrical system with multiple inverters and motors. For illustration, the electrical system includes a first inverter 602, a first motor 604, a second inverter 606, and a second motor 608. The battery 202 is connected to both the first inverter 602 and the second inverter 606. The phases of each inverter can be controlled to generate a heating alternating current through the battery without causing unwanted torque disturbances in the motors. A single diode D3 is used to prevent reverse current from the electrical system to the charging station.

[0048] Fig. Figure 7 shows a diagram 700 of the charging power over time. Time is indicated on the abscissa in seconds (s) and module power on the ordinate in kilowatts (kW). It should be noted that the numerical markings along each axis are for illustrative purposes only and are not intended to restrict the procedure described here. Diagram 700 contains a first power curve 702, which shows a baseline charging process; a second power curve 704, which shows a pulsed charging process (with ripple current); and a third power curve 706, which shows a pulsed charging process with a power increased to 1.1 times the maximum power of the baseline charging process. As the first power curve 702 shows, the baseline charging power during a constant current phase (from approximately t = 0 to approximately t = 1050 seconds) is approximately 220 kW.During the constant current phase (after about t = 1050 seconds), the charging power decreases until the battery 202 is fully charged (at about t = 1880 seconds).

[0049] As the second power curve 704 shows, the pulsed charging power during a constant current phase (from approximately t = 0 to approximately t = 1250 seconds) is about 220 kW. During the constant current phase (after approximately t = 1250 seconds), the pulsed charging power decreases until the battery 202 is fully charged (at approximately t = 1400 seconds).

[0050] As can be seen from the third power curve 706, the pulsed charging with increased power during a constant current phase (from approximately t = 0 to approximately t = 1150 seconds) is about 220 kW. During the constant current phase (after approximately t = 1150 seconds), the pulsed charging with increased power decreases until the battery 202 is fully charged (at approximately t = 1290 seconds).

[0051] Fig. Figure 8 shows a graph 800 of the state of charge (SOC) over time. Time is shown along the abscissa in seconds (s), and the SOC is shown along the ordinate as a percentage (SOC%) of the maximum SOC. Graph 800 includes a first SOC curve 802, which shows a baseline charge; a second SOC curve 804, which shows a pulsed charge; and a third SOC curve 806, which shows pulsed charging with power increased to 1.1 times the maximum power of the baseline charge. The first SOC curve 802 reaches 100% charge at approximately t = 1880 seconds. The second SOC curve 804 reaches 100% charge at approximately t = 1400 seconds. The third SOC curve 806 reaches 100% charge at approximately t = 1290 seconds.

[0052] Pulsed charging can be used to warm the battery, especially when charging at low temperatures. When the battery temperature is low, the ripple current can be adjusted to favor battery heating. These heating effects can be used in conjunction with an existing battery heater to increase the heating rate compared to heating by the heater and ripple current alone.

[0053] Fig. Figure 9 is a diagram 900 showing a low-amplitude ripple current 902 that can be used for charging. Time (t) is shown on the abscissa and current (A) on the ordinate axis. The low-amplitude ripple current 902 remains close to the RMS value of the charging current. Therefore, the charging current is always a positive value. The low-amplitude ripple current 902 is ideal for use in a later stage of a charging process and in a constant-voltage phase.

[0054] Fig. Figure 10 is a diagram 1000 showing a medium-amplitude ripple current 1002 that can be used for charging. Time (t) is shown on the abscissa and current (A) on the ordinate axis. The peak-to-peak voltage of the medium-amplitude ripple current 1002 is designed so that the charging current drops to zero once per cycle. Therefore, the medium-amplitude ripple current 1002 inhibits the occurrence of plating on the lithium-ion battery while heating the battery during charging. The medium-amplitude ripple current 1002 is ideal for the early stages of charging (CC).

[0055] Fig. Figure 11 is a diagram 1100 showing a high-amplitude ripple current 1102 that can be used for charging. Time (t) is shown on the abscissa and current (A) on the ordinate axis. The peak-to-peak voltage of the high-amplitude ripple current 1102 is chosen such that the charging current drops below zero once per cycle. Therefore, the high-amplitude ripple current 1102 strongly inhibits the occurrence of plating on the lithium-ion battery while simultaneously providing a high level of heating to the battery. The high-amplitude ripple current 1102 is ideal for early charge (CC) phases and low-temperature conditions.

[0056] Fig. Figure 12 is a diagram (1200) illustrating a heating and pulse charging strategy. A first curve (1202) shows the charging rate. A second curve (1204) shows the charging pulse rate. A third curve (1206) shows the battery temperature. The strategy comprises three stages. In the first stage (1208), the primary objective is to raise the battery temperature as quickly as possible. In the second stage (1210), the objective is to accelerate the charging rate. In the third stage (1212), the objective is pulse charging until the battery is fully charged.

[0057] In the first stage 1208, there is a low charging rate (first curve 1202) and a high pulse rate (second curve 1204). The battery temperature (third curve 1206) is low. In the second stage 1210, the charging rate (first curve 1202) increases, while the pulse rate (second curve 1204) decreases, causing the battery to heat up, as shown by the third curve 1206. In the third stage 1212, the charging rate (first curve 1202) is reduced. The pulse rate (second curve 1204) is maintained, while the cell temperature (third curve 1206) increases until the battery is fully charged.

[0058] Fig. Figure 13 is a diagram 1300 showing the charging power for different charging methods for a cold battery. Time is shown in seconds (s) on the x-axis and module power in kilowatts (kW) on the y-axis. For illustrative purposes, the battery temperature starts at -20 degrees. Time is given in seconds (s) on the x-axis and module power in kilowatts (kW) on the x-axis. A first curve 1302 shows the power for a baseline charging process. A second curve 1304 shows the power for a baseline charging process with 0.5 degrees / min of external heating, e.g., from an external heat source. A third curve 1306 shows the power for a pulsed charging process without external heating. A fourth curve 1308 shows the power for a pulsed charging process with 0.5 degrees / min of external heating. A fifth curve 1310 shows the power for pulsed charging with 0.5 degrees / min external heating and with 1.1 times the power of the basic charging process.

[0059] The charging time varies from cycle to cycle. The baseline charge (first curve 1302) is completed after approximately 3400 seconds. The baseline charge with 0.5 degrees / min external heating (second curve 1304) is completed after approximately 2400 seconds. The pulsed charge without external heating (third curve 1306) is completed after approximately 1900 seconds. The pulsed charge with 0.5 degrees / min external heating (fourth curve 1308) is completed after approximately 1735 seconds. The pulsed charge with 0.5 degrees / min external heating and 1.1 times the power of the baseline charge (fifth curve 1310) is completed after approximately 1600 seconds.

[0060] Fig.Figure 14 is a diagram (1400) showing battery temperatures for different charging methods with a cold battery. Time is indicated in seconds (s) along the abscissa, and temperature is indicated in degrees Celsius (°C) along the abscissa. The first curve (1402) shows the battery temperature during a basic charge. The second curve (1404) shows the battery temperature for a basic charge with 0.5 degrees / min of external heating. The third curve (1406) shows the battery temperature for a complete charge without external heating. The fourth curve (1408) shows the battery temperature for a complete charge with 0.5 degrees / min of external heating. The fifth curve (1410) shows the battery temperature for a complete charge with 0.5 degrees / min of external heating and at 1.1 times the power of the basic charge.

[0061] During the initial charging process (first curve 1402), the battery temperature rises only slightly to approximately -15 °C. During the initial charge with 0.5 °C / min external heating (second curve 1404), the battery temperature rises to approximately 10 °C. During the continuous charge without external heating (third curve 1406), the battery temperature rises to approximately 18 °C. During the continuous charge with 0.5 °C / min external heating (fourth curve 1408), the battery temperature rises to approximately 25 °C. During the continuous charge with 0.5 °C / min external heating and at 1.1 times the power of the initial charge (fifth curve 1410), the battery temperature reaches approximately 23 °C.

Claims

[1] Method for charging a battery (202) of a vehicle (10), comprising: Receiving a base charging current (402) from a charging station (70) coupled to an electrical system (200) of the vehicle (10), wherein the electrical system (200) comprises the battery (202), an inverter (204) and a positive bus line (210) connecting the battery (202) to the inverter (204) and the battery (202) to the charging station (70), wherein the inverter (204) comprises a first contactor (S1) for connecting the battery (202) and the inverter (204) along the positive bus line (210); Controlling the first contactor (S1) to generate a ripple current (404) on the positive bus line (210); Superimposing the ripple current (404) over the base charging current (402) to obtain a combined charging current (406); and Charging the battery (202) using the combined charging current (406); wherein the electrical system (200) comprises a second contactor (S2) between the positive bus line (210) and a midpoint of a branch (208a, 208b, 208c) of the inverter (204), further comprising controlling the first contactor (S1) and the second contactor (S2) to generate the ripple current (404). [2] Method according to claim 1, wherein a charging process comprises a constant current phase, further comprising charging the battery (202) using the combined charging current (406) during the constant current phase. [3] Method according to claim 1, further comprising controlling an amplitude of the ripple current (404) to perform at least one of the following: (i) preventing plating from occurring on the battery (202); and (ii) heating the battery (202). [4] Method according to claim 1, further comprising providing the base charging current (402) at a first power, superimposing the ripple current (404) over the base charging current (402) to generate the combined charging current (406) with the first power, and increasing the combined charging current (406) from the first power to a second power which is greater than the first power. [5] Electrical system (200) of a vehicle (10), comprising: a battery (202); an inverter (204) which is connected to the battery (202) via a positive bus line (210); a first contactor (S1) inside the inverter (204) which connects the battery (202) to the inverter (204) via the positive bus line (210); a charging port (54) for connecting the positive bus line (210) to a charging station (70) for receiving a basic charging current (402) from the charging station (70); and a processor configured to control the first contactor (S1) to generate a ripple current (404) in the positive bus line (210), wherein the ripple current (404) is superimposed on the base charging current (402) to obtain a combined charging current (406) for charging the battery (202); wherein the electrical system (200) has a second contactor (S2) between the positive bus line (210) and a midpoint of a branch (208a, 208b, 208c) of the inverter (204) and the processor is further configured to control the first contactor (S1) and the second contactor (S2) to generate the ripple current (404). [6] Electrical system (200) according to claim 5, wherein a charging process comprises a constant current phase and the processor is further configured to charge the battery (202) using the combined charging current (406) during the constant current phase. [7] Electrical system (200) according to claim 5, wherein the processor is further configured to control an amplitude of the ripple current (404) to perform at least one of the following: (i) preventing plating from occurring on the battery (202); and (ii) heating the battery (202). [8] Electrical system (200) according to claim 5, wherein the processor is further configured to provide the base charging current (402) at a first power, to superimpose the ripple current (404) over the base charging current (402) to generate the combined charging current (406) at the first power, and to increase the combined charging current (406) from the first power to a second power which is greater than the first power.

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