Electrically driven vehicle and method for operating same

Abstract

The invention relates to a method for operating an electrically driven vehicle having a high-voltage on-board electrical system (5) with a high-voltage battery (6), and having a low-voltage on-board electrical system (1) which is connected to the high-voltage on-board electrical system (5) via a DC / DC converter (2) and has a low-voltage battery (3) and at least one connected consumer (4.1 to 4.n), wherein the low-voltage battery (3) has a plurality of battery cells (9) which can be selectively connected to or disconnected from the low-voltage on-board electrical system (1) via a charging switch (7) for charging, and which can be selectively connected to or disconnected from the low-voltage on-board electrical system (1) via a discharge switch (8) for discharging, wherein, when the vehicle is stationary, the low-voltage battery (3) fundamentally takes over the provision of energy for the at least one consumer (4.1 to 4.n) when the discharge switch (8) is closed, while the DC / DC converter (2) is switched off, wherein when the vehicle is stationary and the power consumption of the at least one consumer (4.1 to 4.n) increases above a predefined threshold value, the discharge switch (8) is opened and the power requirement is covered from the high-voltage battery (6) via the DC / DC converter (2).

Description

[0001] Mercedes Benz Group AG

[0002] Electrically powered vehicle and method for its operation

[0003] The invention relates to a method for operating an electrically powered vehicle according to the preamble of claim 1 and an electrically powered vehicle according to the preamble of claim 7.

[0004] The longer a component's active operating time, the faster it ages and the sooner it loses its proper functioning. This also applies to low-voltage batteries in motor vehicles. As long as the low-voltage battery is active, discharging and then recharging, it ages. Increasing availability requirements for electrical consumers, even when the vehicle is stationary (vehicle updates, remote access, charging processes, using the vehicle as a "living room," etc.), extend the operating time of the low-voltage battery at high charging rates. As a result, it loses its functionality sooner and must be replaced at considerable expense by the customer (or replaced by the OEM as a goodwill gesture).

[0005] To solve this problem, a larger battery can be chosen, but this is associated with high costs. Alternatively, the power consumption can be reduced. However, this will result in fewer functions being available or available for a shorter period.

[0006] DE 202024001 478 U1 describes a motor vehicle, preferably an electric motor vehicle, comprising: a battery pack comprising several battery cells, preferably several lithium battery cells; at least one discharge resistor; an electrical circuit by means of which the several battery cells and the at least one discharge resistor can be electrically connected to each other, preferably selectively; and a monitoring device comprising at least one temperature sensor for detecting a temperature of the battery pack and / or at least one voltage sensor for detecting a voltage of the battery pack;wherein the monitoring device is configured, when the motor vehicle is switched off, preferably parked, to put the electrical circuit into a discharge switching state depending on the temperature detected by at least one temperature sensor and / or depending on the voltage detected by at least one voltage sensor, in which at least one battery cell of the several battery cells is electrically connected to the at least one discharge resistor in order to discharge the at least one battery cell at least partially, preferably completely.

[0007] The invention is based on the objective of providing a novel method for operating an electrically powered vehicle and a novel electrically powered vehicle.

[0008] The problem is solved according to the invention by a method for operating an electrically powered vehicle with the features of claim 1 and an electrically powered vehicle with the features of claim 7.

[0009] Advantageous embodiments of the invention are the subject of the dependent claims.

[0010] A method is proposed for operating an electrically powered vehicle with a high-voltage electrical system comprising a high-voltage battery and a low-voltage electrical system connected to the high-voltage system via a DC / DC converter. The low-voltage system includes a low-voltage battery and at least one connected load. The low-voltage battery comprises a plurality of battery cells that can be selectively connected to or disconnected from the low-voltage electrical system for charging via a charging switch, and that can be selectively connected to or disconnected from the low-voltage electrical system for discharging via a discharge switch. When the vehicle is stationary, the low-voltage battery generally supplies energy to the at least one load when the discharge switch is closed, while the DC / DC converter is switched off.

[0011] According to the invention, when the vehicle is stationary and the current draw of at least one consumer exceeds a predetermined threshold—for example, during the installation of an update, when a user accesses the vehicle via an app, or when charging the vehicle—the discharge switch is opened, and the current demand is met by the DC / DC converter from the high-voltage battery. This prevents the battery from discharging as soon as current is dynamically demanded by active electrical consumers. This current demand is then met by the DC / DC converter. By preventing the discharge of the low-voltage battery, subsequent recharging is also unnecessary. Overall, its charging throughput is reduced, thus protecting the low-voltage battery and preventing premature aging.

[0012] In one embodiment, when the vehicle switches to ferry operation or to a standby state, the discharge switch is closed again and the DC / DC converter is deactivated.

[0013] In one embodiment, the charging switch and the discharging switch are integrated into the low-voltage battery.

[0014] Alternatively, the charging switch and the discharging switch are included in the vehicle's electrical power distribution system.

[0015] In one embodiment, during ferry operation of the vehicle, the low-voltage battery takes over the buffering of dynamic processes and supports the DC / DC converter in overload situations.

[0016] According to one aspect of the present invention, a vehicle with an electric drive, a high-voltage electrical system with a high-voltage battery for supplying the electric drive, and a low-voltage electrical system connected to the high-voltage electrical system via a DC / DC converter, comprising a low-voltage battery and at least one connected load, is proposed. The low-voltage battery has a plurality of battery cells that can be selectively connected to or disconnected from the low-voltage electrical system for charging via a charging switch, and that can be selectively connected to or disconnected from the low-voltage electrical system for discharging via a discharge switch. According to the invention, the vehicle is configured for operation using the method described above.

[0017] The vehicle can be, for example, a passenger car, a commercial vehicle, or a bus. Since the necessary hardware for implementing the solution is usually already present in motor vehicles, no additional hardware is required. The low-voltage battery is protected by decoupling in situations where it is not needed. The charging throughput of the low-voltage battery is reduced, resulting in fewer battery cycles. Consequently, the aging process is slowed down. With less pronounced aging effects, the battery can be optimized for parameters other than aging, leading to savings in costs, weight, and / or installation space.

[0018] Less aging batteries lead to a longer lifespan and therefore to higher customer satisfaction.

[0019] Unlike the prior art described above, the present invention disconnects the battery from the electrical supply in such a way that its charge throughput and thus its aging are reduced. The cells are explicitly not discharged. This allows all electrical consumers in the vehicle to continue operating without impairment (and optionally at full capacity) without the low-voltage battery being cycled (as would be the case without the invention).

[0020] Exemplary embodiments of the invention are explained in more detail below with reference to drawings.

[0021] This shows:

[0022] Fig. 1 shows a schematic view of a low-voltage electrical system connected to a high-voltage electrical system via a DC / DC converter, and Fig. 2 shows a schematic view of a low-voltage electrical system with a low-voltage battery and a DC / DC converter.

[0023] Corresponding parts are marked with the same reference symbols in all figures.

[0024] Figure 1 is a schematic view of a low-voltage electrical system 1 (for example, with an operating voltage of 12 V) connected via a DC / DC converter 2 to a high-voltage electrical system 5, which converts a voltage in the high-voltage electrical system 5 of, for example, 800 V into the operating voltage of the low-voltage electrical system 1. [2024P03792WÖ]

[0025] 5

[0026] The low-voltage electrical system 1 has a low-voltage battery 3, which, like the DC / DC converter 2, is used to supply electrical consumers 4.1 to 4.n.

[0027] A high-voltage battery 6 is connected to the high-voltage electrical system 5.

[0028] The low-voltage battery 3 typically supplies all dynamic loads (for example, short-term high current demands of an electric power steering system 4.1 and / or electric brake 4.2) and buffers dynamic processes until the DC / DC converter 2, which may be slower due to its inertia, takes over the load (electrical consumers 4.1 to 4.n at the time of switch-on). Furthermore, the low-voltage battery 3 also ensures that in cases where the DC / DC converter 2 cannot guarantee a supply, at least all safety-relevant consumers 4.1 and 4.2 continue to be supplied with energy (this function is typically assigned an ASIL level for functional safety reasons).

[0029] One possible reason that could lead to the failure of the DC / DC converter 2 is, for example, a high-voltage safety problem, which leads to the opening of contactors in the high-voltage battery 6 and thus to the immediate failure of the DC / DC converter 2.

[0030] Depending on redundancy requirements, additional on-board network channels can be added to the low-voltage on-board network shown in Figure 1.

[0031] The idea presented below is not limited to use in the low-voltage electrical system 1 shown, but can be applied in any supply network where a low-voltage battery 3 is used.

[0032] Figure 2 is a schematic view of a low-voltage electrical system 1 with a low-voltage battery 3 and a DC / DC converter 2.

[0033] The low-voltage battery 3 includes a charging switch 7, which can prevent charging of the battery cells 9 of the low-voltage battery 3, and separately a discharging switch 8, which can prevent discharging of the battery cells 9 of the low-voltage battery 3. The charging switch 7 and the discharging switch 8 are used for battery protection purposes. 2024P03792WÖ

[0034] 6

[0035] The charging switch 7 and the discharging switch 8, if not integrated into the low-voltage battery 3, can also be included in an electrical power distribution system of a vehicle, in particular an electrically powered vehicle.

[0036] In addition, the charging switch 7 and the discharging switch 8 can also be used for the normal operation of the low-voltage battery 3.

[0037] During ferry operation, the low-voltage battery 3 buffers dynamic processes and provides support in overload situations. Short-term current fluctuations, for example due to start-up processes, are buffered by the low-voltage battery 3.

[0038] When the vehicle is stationary, the low-voltage battery 3 largely takes over the energy supply without the support of the DC / DC converter 2, which can be switched off.

[0039] Due to increasing availability requirements for electrical consumers 4.1 to 4.n even when stationary (vehicle updates, remote access, charging processes, vehicle use as a "living room"), the operating time of the DC / DC converter 2 also increases significantly when stationary. During this time, both the low-voltage battery 3 and the DC / DC converter 2 are active under normal circumstances.

[0040] According to the present invention, this problem is solved by opening the discharge switch 8. This saves installation space, weight and costs and avoids the disadvantages of known solutions described above.

[0041] During phases in which the vehicle is stationary (no ferry operation) and yet in a state with increased power consumption, for example because an update is being installed, a user is accessing the vehicle via app or the vehicle is being charged, the discharge switch 8 of the low-voltage battery 3 is opened.

[0042] This allows the low-voltage battery 3 to be charged to the desired state of charge. In particular, this also prevents the low-voltage battery 3 from discharging when current is dynamically demanded by the active electrical consumers 4.1 to 4.n. This current demand is now met by the DC / DC converter 2.

[0043] Preventing the discharge of the low-voltage battery 3 reduces its charge throughput and thus protects the low-voltage battery 3.

[0044] As soon as the vehicle enters ferry operation or a true resting state, the discharge switch 8 is closed again, thus enabling the regular operation of the low-voltage battery 3.

Claims

Mercedes Benz Group AG Patent claims 1. Method for operating an electrically powered vehicle with a high-voltage electrical system (5) with a high-voltage battery (6) and a low-voltage electrical system (1) connected to the high-voltage electrical system (5) via a DC / DC converter (2) with a low-voltage battery (3) and at least one connected load (4.1 to 4.n), wherein the low-voltage battery (3) has a plurality of battery cells (9) which can be selectively connected to or disconnected from the low-voltage electrical system (1) for charging via a charging switch (7), and which can be selectively connected to or disconnected from the low-voltage electrical system (1) for discharging via a discharge switch (8), wherein when the vehicle is stationary, the low-voltage battery (3) generally provides the energy for the at least one load (4.1 to 4.n) when the discharge switch (8) is closed, while the DC / DC converter (2) is switched off. characterized in that, when the vehicle is stationary and the current draw of at least one consumer (4.1 to 4.n) is increased above a predetermined threshold, the discharge switch (8) is opened and the current requirement is met via the DC / DC converter (2) from the high-voltage battery (6).

2. Method according to claim 1, characterized in that when the vehicle switches to ferry operation or to a standby state, the discharge switch (8) is closed again and the DC / DC converter (2) is deactivated.

3. Method according to claim 1 or 2, characterized in that the charging switch (7) and the discharging switch (8) are integrated into the low-voltage battery (3).

4. Method according to one of claims 1 or 2, characterized in that the charging switch (7) and the discharging switch (8) are included in an electrical power distribution of the vehicle.

5. Method according to any one of the preceding claims, characterized in that during ferry operation of the vehicle the low-voltage battery (3) takes over the buffering of dynamic processes and supports the DC / DC converter (2) in overload situations.

6. Method according to any one of the preceding claims, characterized in that the increased current consumption of the at least one consumer (4.1 to 4.n) above the specified threshold occurs when installing an update, when a user accesses the vehicle via app or when charging the vehicle.

7. Vehicle with electric drive, a high-voltage electrical system (5) with a high-voltage battery (6) for supplying the electric drive and a low-voltage electrical system (1) connected to the high-voltage electrical system (5) via a DC / DC converter (2) with a low-voltage battery (3) and at least one connected load (4.1 to 4.n), wherein the low-voltage battery (3) has a plurality of battery cells (9) which can be selectively connected to or disconnected from the low-voltage electrical system (1) for charging via a charging switch (7), and which can be selectively connected to or disconnected from the low-voltage electrical system (1) for discharging via a discharge switch (8), characterized in that the vehicle is configured for operation using the method according to one of the preceding claims.

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