Low voltage energy management system

Abstract

According to one aspect of the invention, a low voltage energy management system for a vehicle is provided. The system includes a low voltage battery; a battery sensor connected to the low voltage battery; a high voltage battery; a controller configured to: in response to a wake-up condition, waking the controller and battery sensor from a sleep state; in response to a recalibration condition, recalibrating the battery sensor; in response to a charging entry condition, charging the low voltage battery with the high voltage battery; and in response to a charging exit condition, stopping the charging of the low voltage battery and putting the controller and battery sensor into the sleep state.

Description

LOW VOLTAGE ENERGY MANAGEMENT SYSTEMTECHNICAL FIELD

[0001] The present disclosure relates to the field of battery energy management, in particular low voltage battery energy management for vehicles.BACKGROUND

[0002] Conventional automotive vehicles power onboard electronics with a Low- Voltage (LV) battery, e.g. 12V, 9V, 6V, 48V batteries. Vehicles equipped with an internal combustion engine charge the LV battery with an alternator run by the engine when the engine is running. When the engine is not running, the vehicle is unable to charge the LV battery and therefore cannot continue to run the electronics while maintaining the State of Charge (SoC) of the battery. As a result, internal combustion engine vehicles typically shutdown electronics a predetermined time after the engine shuts down. Vehicles equipped with a High-Voltage (HV) battery for powering an electric powertrain can use the HV battery to charge the LV battery. The HV battery typically has a larger capacity than the LV battery which allows the LV battery to be continually charged and thus maintain a SoC while powering the electronics. This allows for electronics to be operated for longer periods of time when the vehicle powertrain is not being operated. However, this extended use of the LV battery can have negative repercussions. For example, extended charging of the LV battery with the HV battery will cause the SoC of the HV battery to decrease, commonly referred to as “phantom drain”. Drives may be unsatisfied to return to a vehicle and find the SoC of the HV battery has significantly decreased. Additionally, continual charging and discharging of the LV battery maintains a load on the LV battery which may degrade the State of Health (SoH) of the LV battery and / or cause sensors monitoring the battery to fall out of calibration.SUMMARY

[0003] According to one aspect of the invention, a low voltage energy management system for a vehicle, the system comprising: a low voltage battery; a battery sensor connected to the low voltage battery; a high voltage battery; a controller configured to: in response to a wake-up condition, waking the controller and battery sensor from a sleep state; in response to a recalibration condition, recalibrating the battery sensor; in response to a charging entry condition, charging the low voltage battery with the high voltage battery; and in response to acharging exit condition, stopping the charging of the low voltage battery and putting the controller and battery sensor into the sleep state.

[0004] According to another aspect of the invention, a low voltage energy management method for a vehicle, the method comprising the steps of: in response to a wake-up condition, waking a controller and a battery sensor from a sleep state; in response to a recalibration condition, recalibrating the battery sensor; in response to a charging entry condition, charging a low voltage battery with a high voltage battery; and in response to a charging exit condition, stopping the charging of the low voltage battery and putting the controller and battery sensor into the sleep state.

[0005] The aspects above achieve a more reliable LV battery SoC, reduces the degradation of the LV battery SoH, and minimizes drain of the HV battery SoC. These and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings..BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 is an illustration of an exemplary embodiment of a Low Voltage Energy Management system.

[0007] FIG. 2 is an illustration of an exemplary embodiment of a Low Voltage Energy Management operation of the Low Voltage Energy Management system.DETAILED DESCRIPTION

[0008] Figure 1 illustrates a Low Voltage Energy Management system 100 for an electric vehicle. System 100 includes a Low Voltage (LV) battery 110, a High Voltage (HV) battery 120, a controller 130, a HV powertrain 140, auxiliary electronics 150, and DC-DC Converter 160. LV battery 110 is a conventional battery with a low voltage, e.g. 12V, 9V, 6V, 48V, and composed of conventional battery chemistries, e.g. AGM (Absorbed Glass-Matt), Lead Acid, Lithium-Ion. Attached to LV battery 110 is one or more battery sensor 111 which measures battery parameters such as current load, voltage, internal resistance, SoC, and SoH. Battery sensor 111 may be an Intelligent Battery Sensor (IBS) that measures multiple parameters. HV powertrain 140 includes one or more electric motor powered by HV battery 120. Auxiliary electronics 150 may include additional controllers, networking components, displays, vehicle actuators, HVAC systems, and the like powered by the LV battery 110. In some embodiments, the auxiliary electronics 150 may be an additional controller that operatescockpit functions such as infotainment. DC-DC converter 160 is positioned between LV battery 110 and HV battery 120 and controlled by controller 130 to charge LV battery 110.

[0009] Controller 130 is programmed to operate system 100. Controller 130 may be a standalone control unit, a control unit that controls the function of multiple vehicle functions, or a module in another control unit or virtualized on another control unit in the vehicle. Controller 130 may include a processor, random access memory (RAM), storage, and input and output ports. The processor may be one or more microprocessors. The RAM functions as a work memory that temporarily stores data to be processed by processor. The storage is capable of saving information that has been put therein. The storage may include a read only memory (ROM) and a rewritable non-volatile memory. As the processor executes a program stored in storage, various types of control are carried out. Additional controllers include similar hardware configurations as controller 130.

[0010] Figure 2 illustrates a Low Voltage Energy Management operation 200 of Low Voltage Energy Management system 100 performed by controller 130. Operation 200 begins when the vehicle is in a Sleep state (Step 201). In a Sleep State, controller 130 and auxiliary electronics 150 are operated in a very low power mode. The vehicle enters the Sleep state when the vehicle will not be operated for an extended period of time, such as long duration parking or when the driver has not been detected for a predetermined time. Maintaining a Sleep state reduces discharge of the LV and HV batteries; however, even in the Sleep state, controller 130 and auxiliary electronics 150 may drain the LV battery. Therefore, it is necessary to charge the LV battery even when the vehicle is in a Sleep state. Operation 200 proceeds when a Wake- Up condition is met (Step 210) and controller 130 and battery sensor 111 are woken up (Step 211). A Wake-Up condition may be when a predetermined time since last Wake-up elapses, e.g. 60-65 minutes. When a Wake-Up condition is not met, the controller 130 and auxiliary electronics 150 remain in the Sleep state.

[0011] Operation 200 proceeds to check whether Recalibration conditions are met (Step 220) for recalibrating the battery sensor 111. Some battery sensors, such as IBS, require extended periods of quiescent current to calibrate. When the battery sensor is maintained at active current levels for extended periods, the battery sensor may fall out of calibration resulting in erroneous readings, such as incorrect battery voltage. Recalibration conditions may be when a charge-cycle counter exceeds a predetermined threshold. When Recalibration conditions are met, controller 130 will execute a Preparation phase (Step 221). In the Preparation phase, the LV battery 110 is charged to a substantially full at a low charging current, e.g. below 2.5A. The controller 130 may determine that the LV battery is substantiallyfully when it can no longer accept charging current, e.g. when charging current drops below the low charging current, or when the battery reaches a substantially full SoC, e.g. 95%. After the Preparation phase is completed, operation 200 sets Entry conditions for LV charging such that the LV battery 110 is not charged for a predetermined number of Wake-Ups or until the LV battery SoC or voltage is below a low threshold, e.g. below 70% SoC or 11 ,5 V. Suspending LV battery charging allows battery sensor 111 time to recalibrate. When the Entry Conditions have been set, the vehicle is returned to the Sleep State (Step 201).

[0012] If the Recalibration conditions are not met, the operation 200 checks whether Entry conditions for LV charging are met (Step 230). When Entry conditions are met, the LV battery 110 is charged by the HV battery 120 (Step 231) via the DC-DC Converter 160. Controller 130 may control the charging voltage based on a measured SoC and battery temperature. For example, the charge voltage when the SoC is low and / or the temperature is low may be higher than when the SoC is high and / or the temperature is high. Entry conditions are based on measurements from battery sensor 111 such as battery voltage, SoC, charging current, SoH, and total available capacity. While LV battery 110 charges, operation 200 checks whether Exit conditions for LV charging are met (Step 232) to stop charging. Exit conditions are based on measurements from battery sensor 111 such as battery voltage, SoC, charging current, SoH, total available capacity, and capacity loss. Basing the Entry and Exit conditions on multiple parameters and not only voltage decreases the effect of an uncalibrated battery sensor 111. For example, even if even when the reading from battery sensor 111 has degraded or when the SoH of the battery capacity has degraded, the controller 130 can determine that the LV battery 110 has reached an upper threshold when charging current falls below a threshold or battery voltage reaches an upper threshold. When Exit conditions are met, the vehicle is returned to the Sleep State (Step 201). When Exit conditions are not met, operation 200 will check whether a Max Timeout since the start of charging has elapsed. When Max Timeout has elapsed, the vehicle is returned to the Sleep state (Step 201). When Max Timeout has not elapsed, the LV battery 110 continues to be charged. Setting a Max Timeout prevents the LV battery 110 from charging for an extended period without reaching an Exit condition and keeping the vehicle awake. This situation may occur if the SoH of the battery has degraded such that the battery cannot reach a threshold voltage or SoC. A Max Timeout may be based on ambient temperature as the LV battery 110 may require more time to charge in cold environments than in warm environments. When Entry conditions are not met (Step 230), the vehicle is returned to the Sleep State (Step 201).

[0013] Low Voltage Energy Management operation 200 aims to keep the vehicle in the Sleep state as much as possible to reduce draining the HV battery 120 while ensuring that the LV battery remains sufficiently charged. Operation 200 further accounts for limitations in sensor accuracy and potential degradation of the LV battery 110 in the charging strategy resulting in a more reliable vehicle.

[0014] The included descriptions and figures depict specific implementations to teach those skilled in the art how to make and use the best mode. For teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these implementations that fall within the scope of the invention. Those skilled in the art will also appreciate that the features described above can be combined in various ways to form multiple implementations. As a result, the invention is not limited to the specific implementations described above, but only by the claims and their equivalents.

Claims

CLAIMSWhat is claimed is:

1. A low voltage energy management system for a vehicle, the system comprising: a low voltage battery; a battery sensor connected to the low voltage battery; a high voltage battery; and a controller configured to: in response to a wake-up condition, waking the controller and battery sensor from a sleep state; in response to a recalibration condition, recalibrating the battery sensor; in response to a charging entry condition, charging the low voltage battery with the high voltage battery; and in response to a charging exit condition, stopping the charging of the low voltage battery and putting the controller and battery sensor into the sleep state.

2. The low voltage energy management system of claim 1, wherein the wake-up condition is based on a predetermined time elapsing.

3. The low voltage energy management system of claim 1, wherein the charging the low voltage battery with the high voltage battery is via a DC-DC converter.

4. The low voltage energy management system of claim 1, wherein the recalibration condition is based on a number of charging cycles.

5. The low voltage energy management system of claim 1, wherein recalibrating the battery sensor comprises charging the low voltage battery to significantly full state of charge at a predetermined charge rate.

6. The low voltage energy management system of claim 5, wherein recalibrating the battery sensor further comprises preventing the low voltage battery from being charged until a predetermined time has lapsed or the low voltage battery state of charge is below a predetermined critical state of charge.

7. The low voltage energy management system of claim 1, wherein the entry condition is based on at least one of a low voltage battery voltage, state of charge, state of health, charging current, total capacity, and capacity loss.

8. The low voltage energy management system of claim 1, wherein the exit condition is based on at least one of a low voltage battery voltage, state of charge, state of health, charging current, total capacity, and capacity loss.

9. The low voltage energy management system of claim 1, wherein the controller is further configured to in response to a max timeout elapsing, stopping the charging of the low voltage battery and putting the controller and battery sensor into the sleep state.

10. The low voltage energy management system of claim 9, wherein the max timeout is based on an ambient temperature.

11. A low voltage energy management method for a vehicle, the method comprising the steps of: in response to a wake-up condition, waking a controller and a battery sensor from a sleep state; in response to a recalibration condition, recalibrating the battery sensor; in response to a charging entry condition, charging a low voltage battery with a high voltage battery; and in response to a charging exit condition, stopping the charging of the low voltage battery and putting the controller and battery sensor into the sleep state.

12. The low voltage energy management method of claim 11, wherein the wake-up condition is based on a predetermined time elapsing.

13. The low voltage energy management system of claim 11, wherein the charging the low voltage battery with the high voltage battery is via a DC-DC converter.

14. The low voltage energy management method of claim 11, wherein the recalibration condition is based on a number of charging cycles.

15. The low voltage energy management method of claim 11, wherein recalibrating the battery sensor comprises charging the low voltage battery to significantly full state of charge at a predetermined charge rate.

16. The low voltage energy management method of claim 15, wherein recalibrating the battery sensor further comprises preventing the low voltage battery from being charged until a predetermined time has lapsed or the low voltage battery state of charge is below a predetermined critical state of charge.

17. The low voltage energy management method of claim 11, wherein the entry condition is based on at least one of a low voltage battery voltage, state of charge, state of health, charging current, total capacity, and capacity loss.

18. The low voltage energy management method of claim 11, wherein the exit condition is based on at least one of a low voltage battery voltage, state of charge, state of health, charging current, total capacity, and capacity loss.

19. The low voltage energy management method of claim 11, further comprising in response to a max timeout elapsing, stopping the charging of the low voltage battery and putting the controller and battery sensor into the sleep state.

20. The low voltage energy management method of claim 19, wherein the max timeout is based on an ambient temperature.

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