Vehicle key off load monitoring

Abstract

The invention provides vehicle key off load monitoring. A current limit is provided for detecting an abnormal current draw of a battery in an electrical system during a key-off state of a vehicle. A plurality of test vehicles are selected that operate without any abnormal current draw. A plurality of time intervals are identified as a function of a plurality of predetermined key off load (KOL) patterns that are continuously activated after the key off state is initiated. A key off interval current during each of the time intervals in each of the test vehicles is measured. A respective average current of the interval currents in each respective time interval is determined. A respective standard deviation current for the interval current in each respective time interval is determined. A respective current limit corresponding to each time interval is set as a function of the respective average current plus a respective delta value determined as a function of the respective standard deviation current.

Description

Technical Field

[0001] The present invention relates generally to battery power management in automotive vehicles and, more particularly, to monitoring battery power management in and between multiple vehicles to identify performance anomalies and / or identify actions for preserving battery reserves. Background Art

[0002] A typical automotive electrical system relies on a battery to power the electrical system loads when the main power source is inactive / unavailable. In a gas-powered vehicle, the main power source typically includes an alternator / generator driven by the internal combustion engine (started by a starter motor, which is also powered by a battery). In an electric propulsion vehicle, the main power source typically includes a high-voltage / high-capacity battery pack (also called a high-voltage traction battery). Typically, the high-voltage battery used for vehicle propulsion provides voltages of up to several hundred volts and has an energy storage capacity of tens or hundreds of kilowatt-hours. Electric vehicles will also typically utilize a low-voltage battery, which is a low-voltage battery, typically a 12-volt battery (which may be the same as the battery used in a combustion engine vehicle). The battery has a limited charge capacity, is much smaller than the high-voltage propulsion battery, and it is very important to maintain sufficient energy storage to start the vehicle (e.g., start the combustion engine or close the high-voltage contactor to connect the traction battery to the electric drive motor).

[0003] Many modern electronic vehicle systems continue to operate even when the vehicle is parked and unattended when the battery is the only available power source. Examples of electronic modules that must always be powered include those that perform functions while the vehicle is parked (e.g., anti-theft systems and remote entry systems), and those that require only a reduced amount of power to maintain memory contents or monitor / measure various conditions or electrical communication signals (e.g., when in sleep mode). Other modules may continue to operate for a specified time after the driver turns off the vehicle, but may be powered down after a specified time (e.g., door-controlled lighting).

[0004] Since the vehicle may be parked for a long time, it is important to limit the consumption of the battery so that when the user returns, there is still enough battery charge state available to activate the vehicle (e.g., start the engine or close the contactor). Therefore, automobile manufacturers specify limits on the current drawn by various modules in each possible situation. Specifically, a static current limit is set for the module, wherein the limit is applied during the time when the vehicle ignition switch has been disconnected for a specified time and there is no user activity. Multiple levels of sleep states (e.g., from a light sleep state to a deep sleep state) can be specified for some modules, and the multiple levels of sleep states gradually reduce the allowable current level over a longer period of time. For example, if a large display screen is placed in a completely powered-off state, a large display screen that is part of a driver information system may require an undesirable long time to activate (e.g., start), thereby forcing the driver to wait when starting the vehicle to use the device as intended. By defining a progressive intermediate current level of the KOL current of the display unit, a compromise between the rapid availability of the driver information system and maintaining sufficient battery power for restarting the vehicle can be achieved.

[0005] With respect to a combined Key-Off-Load management system that combines the current drawn from the battery by all loads, there may be a first (deepest) KOL mode, referred to as KOL-1, which allows a maximum total quiescent current of no more than 8 milliamps (mA). KOL-1 is typically used in newly manufactured vehicles only during vehicle shipping mode when they are delivered to dealers. The next deepest KOL mode is referred to as KOL-2, which may allow a maximum quiescent current of no more than 20mA. This may be considered a normal sleep state in which some modules are still partially powered during the key-off state (e.g., providing the ability to enter keypad detection and other normal vehicle monitoring operations). A KOL-3 mode may be provided, which allows a maximum quiescent current of up to 50mA to allow certain features to be fully activated. For example, a luxury vehicle may operate a welcome function, such as welcome lighting, based on detecting a user approaching the vehicle (e.g., polling to detect a wireless device on the user). A KOL-4 mode may be provided, which allows a maximum quiescent current of up to 500mA. This higher current draw level can be used to keep large display panels or other ECUs and computerized systems partially powered during vehicle sleep to provide a quick start (e.g., a few seconds instead of 30 seconds or more for powering off a display system). Even with the enhanced battery capacity, the KOL-4 mode can typically only be maintained for approximately 14 to 24 hours. It should be noted that in any particular vehicle, not all four modes described above may be implemented, and a smaller number of modes may be used. For example, the KOL-3 mode and KOL-4 mode described above may be combined into a single mode (i.e., the welcome function of the display system and the quick start mode may be controlled together). In addition, the KOL modes may be subsets of each other, such that a higher mode may activate certain loads at a higher current draw, but any loads other than those specifically modified for that mode continue to operate as defined by the lower mode.

[0006] The setting of the maximum total quiescent current value depends on the interaction between the electrical demands of the various modules to provide the desired features at the appropriate times and the need to maintain the battery charge level over the required period of time. Due to the complexity of device interactions and the large number of contingencies in both the current drawn by the loads and the storage capacity of the individual batteries, determining the quiescent current limit for detecting excessive current drain during key-off is time consuming and resource intensive. In addition, tracking and evaluating vehicle KOL performance for a fleet of vehicles has been difficult and imprecise.

[0007] Attempts by vehicle manufacturers to proactively identify potential issues involving key-off load performance by predictively detecting trends in events where excessive KOL current draw occurs are hampered by a lack of meaningful metrics. It would be desirable to be able to better identify KOL performance issues and improve diagnosis of the causes of such performance issues. Manufacturers want to monitor such trends because excessive current draw can cause battery wear, which can lead to warranty costs and dissatisfaction. Summary of the invention

[0008] In one aspect of the invention, a method for setting a current limit for detecting abnormal current draw of a battery in an electrical system during a key-off state of a vehicle includes selecting a plurality of test vehicles operating without any abnormal current draw. Identifying a plurality of time intervals based on a plurality of predetermined key-off load (KOL) patterns that are activated successively after initiating the key-off state. Measuring the key-off interval current during each of the time intervals in each of the test vehicles. Determining a corresponding average current of the interval current in each corresponding time interval. Determining a corresponding standard deviation current of the interval current in each corresponding time interval. Setting a corresponding current limit corresponding to each time interval based on the corresponding average current plus a corresponding delta value determined based on the corresponding standard deviation current.

[0009] As used herein, key-on or key-off states refer to activation and deactivation vehicle states that are controlled not only using a physical key and lock, but also using a push button switch, keypad, voice command, or wireless device such as a key fob or a smartphone with a phone as a key (PaaK) application. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a graph showing the current draw limits for different KOL modes compared to the actual current draw during a key-off state.

[0011] Figure 2 is a block diagram illustrating the interaction of the power management module and the controller module.

[0012] Figure 3 is a block diagram illustrating one embodiment of an electrical architecture for distributing power and multiplexing communication signals in which KOL power management is implemented.

[0013] Figure 4 is a graph showing measured current draw from multiple test vehicles during a key-off state.

[0014] Figure 5 is a data distribution of current measured during an exemplary time interval of a test vehicle.

[0015] Figure 6is a flow chart illustrating a process for determining a current limit to detect excessive current draw in a purchased vehicle.

[0016] Figure 7 is a block diagram illustrating one embodiment of a circuit for detecting and responding to excessive KOL current in a vehicle.

[0017] Figure 8 is a flow chart illustrating a method for monitoring a fleet of purchased vehicles.

[0018] Fig. 9 is a block diagram illustrating a system for monitoring a fleet of vehicles. DETAILED DESCRIPTION

[0019] Figure 1 1 shows the variation of the current drawn from the battery by the combined electrical loads over a time span during which the main power is not available (i.e., the vehicle is in a key-off state). Trace 10 depicts the total current draw from the battery, which follows a gradual decline starting with the ignition key off (IGN off), resulting in trace 10 falling to a reduced level 12 at 11 during the first key-off mode. The current draw 12 occurs during a time period known as the accessory delay (from IGN off to the first delay time Delay1). During the accessory delay, several systems and modules continue to operate to temporarily assist the occupants (e.g., door-controlled lighting, active power points, and power window operation). During the accessory delay, active systems may continue to draw current from the battery to operate various devices according to time periods and capabilities determined within the various systems. For the purpose of detecting unexpected high current draws, the dashed line 13 depicts the maximum current draw specified during the accessory delay. As used herein, a "power-off state" includes 1) a sleep state when the module suspends most activities but still uses a small amount of power to monitor for wake-up signals, and 2) a completely off state.

[0020] At a subsequent time as indicated by Delay1, the power management controller determines that the global accessory delay period has expired. The accessory delay period may be a predetermined length of time after the IGN is turned off, or may also depend on the moment when an occupant is detected to be leaving the vehicle. At Delay1, many functions are disabled, and with some systems / modules powered off, the current draw is expected to drop below the level indicated at 15. After this, a new KOL mode begins, during which the overall battery consumption is expected to be below the current limit 14. At subsequent times Delay3 and Delay4, other KOL modes begin, during which additional systems / modules are turned off and tighter current limits are imposed.

[0021] Figure 2Portions of the vehicle electrical system involving key-off load management are shown. A body control module (BCM) 16 is configured (e.g., via software and / or firmware programming) to implement a key-off load management strategy in response to a vehicle ignition state, which is determined in response to a data message from a multiplexed bus. The BCM 16 is coupled to a battery monitoring system (BMS) 17, which is connected to a battery (not shown). The electronic controller module 18 represents any electronic module (e.g., a lighting module, an HVAC module, an audio entertainment module, or a wireless communication module) that receives power from a battery during a key-off state and may have a number of different power modes that may be monitored by the BCM 16. The BCM 16 receives the measured current i from the BMS 17. The BCM 16 exchanges various control and data signals with a representative controller module 18, such as commands for powering on, entering a sleep mode, and initiating a power-off mode. The module 18 may transmit various response signals to the BCM 16, such as status / confirmation signals, and data messages identifying the duration that the module 18 remains awake.

[0022] Figure 3 A more complete electrical architecture is shown having a battery 20 connected to a battery monitoring system (BMS) 21. The BMS 21 may be a conventional component that measures, among other things, the battery current flowing from the battery 20 to the electrical loads. When part of an electric propulsion vehicle, the low voltage battery 20 may be recharged from a high voltage battery pack 22 via a DC to DC converter 23. When included in a gas propulsion vehicle or a hybrid vehicle, the battery 20 may be recharged by an alternator 24 driven by an internal combustion engine 25.

[0023] The body control module (BCM) 26 and the BMS 21 are both contained within and communicate via a bus network (not shown) such as a CAN bus that links the electronic modules within the group 27. The bus network for the group 27 is interconnected with a gateway 28, which is further connected to additional bus network groups 29 and 30 that can operate using different protocols. The gateway 28 reformats and passes messages between networks, allowing modules in different bus networks to exchange communication signals as is known in the art. The power bus 31 distributes the output of the battery 20 to various modules including the BCM 26 and many other modules, including a group of modules 32-34 interconnected in the bus group 27.

[0024] Also interconnected within bus group 27 are module 35 and powertrain control module (PCM) 36. Power to modules 35 and 36 is controlled by BCM 26 as subnet 37 (e.g., power to these modules is managed as a unit by BCM 26). Modules 35 and 36 both receive supply voltage directly via power bus 31, but each receives shared control signals from BCM 26 to simultaneously activate or deactivate power to modules 35 and 36. Control messages from BCM 26 may also include commands to control power delivery to slave components of the control module, such as sensors 38 and actuators 41 that receive power through PCM 36.

[0025] In another example of power management, the BCM 26 is connected to a relay 39 that receives power from the power bus 31 and selectively transmits the power to a module 40. The relay 39 may, for example, include an ignition relay. The module 40 is also connected to the bus group 27. The relay 39 may be controlled by a direct signal connection to the BCM 26, or alternatively by a multiplexed message. However, the module 40 does not have a sleep mode, but is fully powered or fully de-powered depending on the on / off state of the relay 39. On the other hand, the modules 35 and 36 are always powered from the power bus 31, but each invokes a corresponding reduced power mode, such as a sleep state.

[0026] With the help of Figure 3 , the BCM 26 can respond to vehicle conditions to operate various loads (e.g., modules) at selected power levels (KOL modes) according to a key-off schedule, and then obtain a measured aggregate key-off current drawn from the battery during each of the key-off time intervals. When the measured key-off current is greater than a specified limit, the BCM 26 can record the event for diagnostic purposes, and can take corrective action to maintain the battery's charge.

[0027] The present invention relates to the selection of appropriate current limits and the monitoring of compliance with current limits by a fleet of vehicles. A key-off load metric is derived that can better identify when and why key-off load problems occur, thereby enabling prediction and prevention of excessive key-off load consumption. The metric follows a time curve of acceptable current draw from a battery (e.g., based on time intervals that are based on the time elapsed since the ignition key was turned off). An exemplary curve has seven time intervals. The metric can provide an overall score that can be used to rate the performance of (A) individual key-off cycles of a vehicle, (B) all key-off cycles of a single vehicle, (C) all key-off cycles in a given week for a given vehicle program or model, or (D) any other combination of key-off cycles of interest.

[0028] When the vehicle is turned off, there are different processes that occur during the vehicle-off period (e.g., via messaging on the CAN bus). Some modules turn off within a few minutes, while other modules are allowed to draw current for a longer period of time. Based on the off mode, a curve can be defined for the acceptable current draw for each corresponding time interval. To develop this curve, a representative sample of vehicles with error-free performance (i.e., nominal test vehicles) is identified. For these well-performing vehicles with no known key-off load issues, the history of the current drawn during multiple key-off cycles is collected during the process of determining the target current. At each time interval of the key-off cycle, the average current is measured. The average current can be composed of the mean (μ) of the periodic current measurements during that interval. The average current is obtained during each of seven time intervals. In one example, the time intervals are 0 to 6 minutes, 6 to 12 minutes, 12 to 30 minutes, 30 to 60 minutes, 60 to 90 minutes, 90 minutes to 3 hours, and more than 3 hours. The standard deviation (σ) of the measured current during each time interval is also determined (using known statistical methods).

[0029] According to some embodiments, if the measured (average) interval current (i) within a single time interval is less than one standard deviation above the mean (μ + σ), the vehicle is in the green zone during that time interval. If the measured interval current is between one and two standard deviations above the mean [i.e., (μ + σ) < i < (μ + 2σ)], it is in the yellow zone. If the measured interval current is greater than two standard deviations above the mean [i.e., i > (μ + 2σ)], it is in the red zone. To score the entire key-off cycle, the "root mean square" scoring method compares the actual vehicle current during each corresponding time interval with a normalized acceptable score that takes into account the sample size using the standard error. Thus, the more key-off cycles used for scoring, the closer the average current from vehicles in service will be to the previously derived target current (which is developed from ideal / well-performing vehicles).

[0030] Using this scoring system, if the final score of a set of key-off cycles is less than or equal to 1, it is performing as expected (i.e., it will pass). If a set of key-off cycles scores greater than 1, the current it draws exceeds the allowed current, and more attention should be paid to these vehicles.

[0031] Figure 4Key-off load current draw for multiple test vehicles is shown. The key-off state of the vehicle is divided into seven time intervals labeled T1 to T7. At the beginning of each time interval, a particular set of electrical loads (e.g., modules) are disabled, causing the total aggregate current to drop accordingly. The solid, dashed, and dot-dash lines each represent the key-off interval current draw for a corresponding one of the test vehicles. Because the current draw in any particular vehicle may not be constant, the current measured within a certain interval may include, for example, an average current during the interval. Multiple key-off cycles can be characterized for each of the multiple test vehicles, and the time intervals can be calculated as follows: Figure 5 The resulting data is analyzed to determine the average current for each corresponding interval and the standard deviation of the current values ​​in the sample. Figure 5 In , each vertical bar shows the number of occurrences of each current value in the sample. The arithmetic mean and one standard deviation (σ) and two standard deviations (2σ) are shown. Based on data from well-behaved vehicles, the current limit can be set at an appropriate level above the mean. For example, the current limit can be set to the mean plus two standard deviations.

[0032] Figure 6 A preferred method for deriving the current limit is outlined in . A plurality of nominal test vehicles are selected in step 42. Test vehicles that are known to operate without any abnormal current draw during a key-off state are selected. Specifically, the test vehicles may include prototype vehicles and / or early production vehicles. Based on the key-off load (KOL) pattern used in the test vehicles, a plurality of time intervals are defined in step 43 to monitor the KOL current draw. The time intervals may each have a start time and an end time measured in respective elapsed times since entering the key-off state.

[0033] In step 44, KOL performance data is collected for a plurality of key-off cycles for each of the test vehicles. More specifically, the key-off current is measured for each time interval in each test vehicle. Preferably, a single current value is derived for each individual time interval, wherein the single value may include (1) an average value of the current draw for the time interval, (2) a maximum current draw during the time interval, or (3) any other representative current value. Using the measured key-off interval currents, an average value (e.g., mean) and standard deviation of all the measured values ​​are determined for each respective time interval in step 45.

[0034] The current limit to be used for each corresponding time interval is derived based on the mean (μ) and the standard deviation (σ). When monitoring a vehicle based on current limit, a measured current consumption that is less than the mean plus the standard deviation (μ+σ) will generally be considered acceptable. For current consumption that is just above the mean plus the standard deviation, there may be a slight overconsumption, and a "yellow" state can be identified. A measured current consumption above or even higher than a threshold value may indicate a "red" state, which may result in a higher probability of depleting charge in the battery. For example, a preferred value for a higher threshold value may be the mean plus twice the standard deviation (μ+2σ). In step 46, the calculated values ​​of μ, σ, and any threshold values ​​are loaded into the vehicle to be monitored. The vehicle to be monitored may be a service vehicle manufactured for sale or otherwise transferred to a customer. As used herein, a "purchased vehicle" refers to any vehicle transferred to a customer by sale, lease, or other means.

[0035] The current limits as derived herein may be used by purchased vehicles for on-board monitoring so that excessive KOL current consumption may be detected and remedied. Figure 7 A monitoring circuit 50 is shown, wherein the measured current i in a time interval x x is coupled to the inverting input of comparator 51 and the non-inverting input of comparator 52. A first threshold (e.g., μ+σ) is coupled to the non-inverting input of comparator 51. A second threshold (e.g., μ+2σ) is coupled to the inverting input of comparator 52. The outputs of comparators 51 and 52 are coupled to statistical analysis unit 54. When current i x When the value of is less than the first threshold, the output of comparator 51 becomes high (logic 1) to indicate a green state (i.e., no over-consumption). At the same time, the output of comparator 52 is low (logic 0) because the current i x The statistical analysis unit 54 is configured to take no action in response to the green state.

[0036] The outputs of comparators 51 and 52 are each coupled to a corresponding inverting input of an AND gate 53, the output of which is coupled to a statistical analysis unit 54. x When the value of becomes greater than the first threshold and less than the second threshold, the low outputs from comparators 51 and 52 are inverted at the input of AND gate 53, causing the output of AND gate 53 to go high to indicate the yellow state. x When the value of is greater than the second threshold, the output of the comparator 52 goes high to indicate a red state (i.e., excessive consumption). The statistical analysis unit 54 is configured to monitor the yellow and red states over time to determine appropriate actions to mitigate excessive KOL current consumption (e.g., driver notification and / or changing the allowed load during the corresponding time interval).

[0037] The purchased vehicle may utilize the current limits as derived herein to detect a KOL condition, during which data regarding excessive KOL current draw should be reported off-board the vehicle to facilitate monitoring of the fleet of vehicles to which the purchased vehicle belongs (e.g., all vehicles of a particular model of car or truck). Once the purchased in-service vehicle is operating based on the current limits as described above, the KOL condition may be detected utilizing the current limits as derived herein. Figure 8 The method shown is used to monitor such a fleet of vehicles. In step 60, each vehicle determines a score for each key-off cycle. The score can be based on an aggregated examination of all differences between the corresponding current limit and the actual current consumption during the corresponding time interval. For example, the score of the key-off cycle in each individual vehicle can be calculated using the square root normalized according to the standard error. In step 61, the scores obtained from multiple cycles are combined (e.g., collected into a data packet and / or further processed to characterize the performance of a single vehicle). For example, the score for the time interval can be composed of a number reflecting how many standard deviations the actual current is above the current limit. A score of 1 or lower will indicate no problem. A score above 1 may be sufficient to initiate a report or other action. In step 62, each individual vehicle reports the score by transmitting a data packet to a central server. For example, the manufacturer can maintain a central server in a network that can be accessed by the vehicle fleet via wireless communication (such as a cellular data connection).

[0038] The received scores are collected and analyzed by the manufacturer using a central server. In step 63, when a particular number of scores or some combination of scores exceeds a threshold (i.e., an anomaly is detected), the manufacturer can initiate an investigation. When there are scores exceeding the threshold, identification of a specific vehicle population is performed in step 64 (e.g., vehicle model and / or trim level of a specific model). In step 65, the scores and any supporting data are analyzed to determine which time intervals are affected by excessive current draw. Based on modules that are known to be active during various time intervals, one or more identities of modules that may be causing the excessive current draw can be tracked in step 66. Based on the source of the excessive current draw, the manufacturer can identify and take resolution or other response actions.

[0039] The reported scores can also be used to track the progress of a fleet of vehicles over time to see if it is improving as a result of actions taken. When a specific vehicle scores above 1 at a point in time, the data can be viewed in a more granular manner to identify which vehicles are experiencing issues and when they occurred during the KOL shutdown process. Once a manufacturer knows when excess consumption occurs during the shutdown process, it can attempt to replicate the problem in a construction vehicle and identify a solution.

[0040] Fig. 9A schematic diagram of an overall implementation of the present invention is shown, wherein a test vehicle 70 is operated without any abnormal current draw, and actual current draw data is collected from the test vehicle by recording data during key-off testing. An engineering function 71 performs the data collection and analyzes the data to generate corresponding current limits to be used in vehicle production, and the current limits are utilized in the manufacturing process 72 of the vehicle 73 in production service. During normal operation, the vehicle 73 monitors the key-off load scores, and when appropriate, the scores are combined and transmitted to the central server 75 via the data link 74. As described above, the engineering function 71 utilizes the data from the central server 75.

Claims

1. A method of setting a current limit for detecting abnormal current consumption of a battery in an electrical system during a key-off state of a vehicle, the method comprising the steps of: Select multiple test vehicles that operate without any abnormal current draw; identifying a plurality of time intervals based on a plurality of predetermined key-off load (KOL) patterns that are successively activated after initiation of the key-off state; measuring a key-off interval current during each of the time intervals in each of the test vehicles; determining a respective average current of the interval currents in each respective time interval; determining a corresponding standard deviation current of the interval current in each corresponding time interval; and A respective current limit corresponding to each time interval is set based on the respective average current plus a respective increment value determined based on the respective standard deviation current.

2. The method of claim 1, wherein each respective average current is formed by an average value of the respective interval currents in each respective time interval.

3. The method of claim 1, wherein each respective incremental value consists of twice the respective standard deviation current.

4. The method according to claim 1, further comprising the steps of: measuring a key-off interval current during each of the time intervals in a purchased vehicle not included in the plurality of test vehicles; comparing the measured key-off interval current to a corresponding current limit; as well as Excessive current draw is detected when one of the measured key-off interval currents is greater than the corresponding current limit.

5. A method of monitoring a fleet of vehicles for excessive key-off load (KOL) current draw when in a key-off state, the method comprising the steps of: Select multiple test vehicles that operate without any abnormal current draw; identifying a plurality of time intervals based on a plurality of predetermined KOL patterns that are successively activated after initiation of the key-off state; measuring a key-off interval current during each of the time intervals in each of the test vehicles; determining a respective average current of the interval currents in each respective time interval; determining a corresponding standard deviation current of the interval current in each corresponding time interval; setting a respective current limit corresponding to each time interval according to the respective average current plus a respective increment value determined according to the respective standard deviation current; communicating the respective current limit to each of the fleet of vehicles; measuring a key-off interval current during each of said time intervals in each of said vehicles in said fleet of vehicles; comparing the measured key-off interval current to the corresponding current limit to determine a corresponding key-off load fraction for each vehicle in the fleet of vehicles; combining key-off load scores from the fleet of vehicles; as well as When the combined key-off load score exceeds a predetermined threshold, an abnormality of the vehicle in the vehicle fleet is detected.

6. The method of claim 5, wherein each respective average current is formed by an average value of the respective interval currents in each respective time interval.

7. The method of claim 5, wherein each respective incremental value consists of twice the respective standard deviation current.

8. The method of claim 5, wherein each respective key-off load fraction is comprised of a root sum of squares of each of the differences between the respective measured key-off interval current and the respective current limit.

9. The method of claim 5, wherein each time interval is associated with a respective first current limit and a respective second current limit, and wherein each respective key-off load fraction is determined based on a compilation of respective time intervals in which the respective measured key-off interval current is greater than the respective first current limit and the respective measured key-off interval current is greater than the respective second current limit.

10. The method of claim 9, wherein each first current limit consists of the corresponding average current plus the corresponding standard deviation current, and wherein each second current limit consists of the corresponding average current plus twice the corresponding standard deviation current.

11. The method of claim 5, further comprising the steps of: When the anomaly is detected, the time interval and the measured key-off interval current are matched to an electronic module in the fleet of vehicles that could fail to generate the measured key-off interval current.

12. A vehicle comprising: a battery configured to supply current during a key-off state of the vehicle; a plurality of electrical loads, each electrical load being configurable to receive said current from said battery during said key-off state depending on a predetermined key-off load (KOL) pattern being active according to a corresponding time interval; a battery monitor that measures a key-off interval current during each of the time intervals; a controller configured to (1) compare the measured key-off interval currents to corresponding current limits and (2) indicate excessive current draw in response to one of the measured key-off interval currents being greater than the corresponding current limit; Wherein the corresponding current limit is obtained from: Select multiple test vehicles that operate without any abnormal current draw; measuring a key-off interval current during each of the time intervals in each of the test vehicles; determining a respective average current of the interval currents in each respective time interval; determining a corresponding standard deviation current of the interval current in each corresponding time interval; and A respective current limit corresponding to each time interval is set based on the respective average current plus a respective increment value determined based on the respective standard deviation current.

13. The vehicle of claim 12, wherein each respective average current is comprised of an average value of the respective key-off interval current for each respective time interval.

14. The vehicle of claim 12, wherein each respective incremental value consists of twice the respective standard deviation current.

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