Diagnostic system for a battery system

A diagnostic system for a battery system in accordance with an exemplary embodiment is provided. The battery system includes a battery module electrically coupled to a contactor. The diagnostic system includes a first microcontroller and a second microcontroller operably communicating with the first microcontroller. The second microcontroller is programmed to open the contactor electrically coupled to the battery module if either a first diagnostic indicator flag is equal to a first fault value or a second diagnostic indicator flag is equal to a second fault value. The second microcontroller is further programmed to open the contactor if either a third diagnostic indicator flag is equal to a third fault value or a fourth diagnostic indicator flag is equal to a fourth fault value.

BACKGROUND

A limitation of other diagnostic systems for battery modules is that each diagnostic system typically opens a contactor associated with the battery module based on a single diagnostic flag which is set to a fault value based on a single signal at a single hardware device. Thus, if the single hardware device is malfunctioning, a desired opening operation of the contactor may not occur.

The inventive diagnostic system provides a technical effect of performing a first diagnostic test on a battery system utilizing first and second diagnostic indicator flags determined utilizing first and second hardware devices (e.g., analog-to-digital converter in a first microcontroller, and a fault line coupled between first and second microcontrollers), respectively. The inventive diagnostic system can open a contactor based on the first and second diagnostic indicator flags. Further, the inventive diagnostic system performs a second diagnostic test on the battery system utilizing third and fourth diagnostic indicator flags determined from third and fourth hardware devices (e.g., voltage comparators in a first microcontroller, and a serial bus), respectively. Further, the inventive diagnostic system can open a contactor based on the third and fourth diagnostic indicator flags.

SUMMARY

A diagnostic system for a battery system in accordance with an exemplary embodiment is provided. The battery system has a battery module electrically coupled to a contactor. The diagnostic system includes a first microcontroller programmed to measure at least first and second cell voltage levels of first and second battery cells, respectively, of the battery module. The first microcontroller is further programmed to transmit the first and second cell voltage levels to a second microcontroller. The first microcontroller has first and second voltage comparators therein. The first and second voltage comparators compare each of the first and second cell voltage levels, respectively, to a threshold cell voltage level. The first and second voltage comparators output first and second comparator output bits, respectively. The first microcontroller is further programmed to set a fault line to a first fault line voltage if at least one of first and second comparator output bits indicate that at least one of the first and second cell voltage levels, respectively, is greater than the threshold cell voltage level. The fault line is operably coupled to the second microcontroller. The second microcontroller is programmed to set a first diagnostic indicator flag equal to a first fault value if at least one of the first and second cell voltage levels of first and second battery cells, respectively, is greater than the threshold cell voltage level. The second microcontroller is further programmed to set a second diagnostic indicator flag equal to a second fault value if the fault line has the first fault line voltage. The second microcontroller is further programmed to open the contactor electrically coupled to the battery module if either the first diagnostic indicator flag is equal to the first fault value or the second diagnostic indicator flag is equal to the second fault value.

A diagnostic system for a battery system in accordance with another exemplary is provided. The battery system has a battery module electrically coupled to a contactor. The diagnostic system includes a first microcontroller having first and second voltage comparators therein. The first and second voltage comparators compare each of first and second cell voltage levels, respectively, of first and second battery cells, respectively, of the battery module to a first threshold cell voltage level. The first and second voltage comparators output first and second comparator output bits, respectively. The first microcontroller is programmed to transmit the first and second comparator output bits from the first and second voltage comparators, respectively, to a second microcontroller. The first microcontroller is further programmed to measure a module output voltage level of the battery module. The first microcontroller is further programmed to transmit the module output voltage level to the second microcontroller. The second microcontroller is further programmed to set a first diagnostic indicator flag equal to a first fault value if at least one of the first and second comparator output bits indicate at least one of the first and second cell voltage levels, respectively, is greater than the first threshold cell voltage level. The second microcontroller is further programmed to set a second diagnostic indicator flag equal to a second fault value if the module output voltage level is greater than a threshold module output voltage level. The second microcontroller is further programmed to open the contactor electrically coupled to the battery module if either the first diagnostic indicator flag is equal to the first fault value or the second diagnostic indicator flag is equal to the second fault value.

DETAILED DESCRIPTION

Referring toFIG. 1, a vehicle10includes a battery system20, an electric motor22, and a diagnostic system24. An advantage of the vehicle10is that the vehicle10utilizes the diagnostic system24that performs a first diagnostic test on the battery system20utilizing first and second diagnostic indicator flags determined utilizing first and second hardware devices (e.g., analog-to-digital converter in a first microcontroller, and a fault line coupled between first and second microcontrollers), respectively. The diagnostic system24can open a contactor based on the first and second diagnostic indicator flags. Further, the diagnostic system24performs a second diagnostic test on the battery system20utilizing third and fourth diagnostic indicator flags determined from third and fourth hardware devices (e.g., voltage comparators in a first microcontroller, and a serial bus), respectively. Further, the inventive diagnostic system can open a contactor based on the third and fourth diagnostic indicator flags.

The battery system20includes a battery module40, contactors42,44, voltage drivers,50,52,54,56, and a DC/AC inverter60.

The battery module40has first and second battery cells,70,72electrically coupled in series with one another between a positive battery module terminal74and a negative battery module terminal76. In an exemplary embodiment, the first and second battery cells70,72are pouch-type lithium-ion battery cells. Of course, in an alternative embodiment, each of the first and second battery cells70,72could comprise another type of battery cell such as nickel-cadmium battery cell, a nickel-metal-hydride battery cell, or a lead acid battery cell for example. The first battery cell70has a positive terminal80and a negative terminal82. Further, the second battery cell72has a positive terminal90and a negative terminal92. The positive terminal80of the first battery cell70is coupled to positive battery module terminal74. The negative terminal82of the first battery cell70is coupled to the positive terminal90of the second battery cell72. Further, the negative terminal92of the second battery cell72is coupled to the negative battery module terminal76. In an alternative embodiment, the battery module40could have a plurality of additional battery cells electrically coupled to one another in series with the first and second battery cells70,72.

The contactor42is electrically coupled in series between the positive battery module terminal74and the DC/AC inverter60. The contactor42includes a contactor coil100and a contact102. When the second microcontroller132generates first and second control signals that are received by the voltage drivers50,52, respectively, the voltage drivers50,52, energize the contactor coil100, which moves the contact102to a closed operational position. Alternately, when the second microcontroller132stops generating the first and second control signals, the voltage drivers50,52de-energize the contactor coil100, which moves the contact102to an open operational position.

The contactor44is electrically coupled in series between the negative battery module terminal76and the DC/AC inverter60. The contactor44includes a contactor coil110and a contact112. When the second microcontroller132generates third and fourth control signals that are received by the voltage drivers54,56, respectively, the voltage drivers54,56, energize the contactor coil110, which moves the contact112to a closed operational position. Alternately, when the second microcontroller132stops generating the third and fourth control signals, the voltage drivers54,56de-energize the contactor coil110, which moves the contact112to an open operational position.

The DC/AC inverter60is electrically coupled to and between the contactors42,44, and provides AC power to the electric motor22via the electrical lines120,122,124.

The diagnostic system24includes a first microcontroller130, a second microcontroller132, a vehicle microcontroller134, serial communication buses136,138and a fault line140.

The first microcontroller130includes a microprocessor160, a memory device162, an analog-to-digital (A/D) converter170, and voltage comparators180,182. The microprocessor160operably communicates with the memory device162, the analog-to-digital (A/D) converter170, and the voltage comparators180,182. The microprocessor160utilizes software instructions stored in the memory device162to implement at least in part the flowchart steps described hereinafter for the first microcontroller130.

The A/D converter170includes input ports A and B which are electrically coupled to the positive terminal80and the negative terminal82, respectively, of the first battery cell70to measure a voltage level between the terminals80,82. The A/D converter170includes input ports B and C which are electrically coupled to the positive terminal90and the negative terminal92, respectively, of the second battery cell72to measure a voltage level between the terminals90,92. The A/D converter70also measures a battery module voltage level of the battery module40utilizing the input ports A and C.

The voltage comparator180is electrically coupled to the input ports A and B, and compares the voltage level (between input ports A and B) of the first battery cell70to a threshold cell voltage level (VTHRESHOLD). If the voltage level of the first battery cell70is greater than the threshold cell voltage level, the voltage comparator180sets an associated comparator output bit to a binary “1” value. Otherwise, the voltage comparator180sets the associated comparator output bit to a binary “0” value.

The voltage comparator182is electrically coupled to the input ports B and C, and compares the voltage level (between input ports B and C) of the second battery cell72to the threshold cell voltage level (VTHRESHOLD). If the voltage level of the second battery cell72is greater than the threshold cell voltage level, the voltage comparator182sets an associated comparator output bit to a binary “1” value. Otherwise, the voltage comparator182sets the associated comparator output bit to a binary “0” value.

The first microprocessor130operably communicates with the second microcontroller132utilizing a serial communication bus136. Further, the first microprocessor130sets a fault line140to a first fault line voltage if at least one of the first and second voltage levels of the first and second battery cells70,72, respectively, are greater than the threshold cell voltage level (VTHRESHOLD). The operation of the first microcontroller130will be discussed in greater detail hereinafter.

The second microcontroller132includes a microprocessor200and a memory device202. The microprocessor200operably communicates with the memory device202. Further, the microprocessor200operably communicates with the microprocessor160of the first microcontroller130via the serial communication bus136and the fault line140. Still further, the microprocessor200operably communicates with a microprocessor210of the vehicle microcontroller134via the serial communication bus138. The microprocessor200utilizes software instructions stored in the memory device202to implement at least in part the flowchart steps described hereinafter for the second microcontroller132. The operation of the second microcontroller132will be discussed in greater detail hereinafter.

The vehicle microcontroller134includes a microprocessor210and a memory device212. The microprocessor210operably communicates with the memory device212. The microprocessor210utilizes software instructions stored in the memory device212to implement at least in part the flowchart steps described hereinafter for the vehicle microcontroller134.

Referring toFIGS. 1-4, a flowchart of a method for performing diagnostic tests on the battery system20utilizing the diagnostic system24in accordance with another exemplary embodiment is provided.

At step300, the first microcontroller130measures at least first and second cell voltage levels of first and second battery cells70,72, respectively, of the battery module40.

At step302, the first microcontroller130transmits the first and second cell voltage levels to a second microcontroller132.

At step304, voltage comparators180,182in the first microcontroller130compare each of the first and second cell voltage levels, respectively, to a first threshold cell voltage level. The voltage comparators180,182output first and second comparator output bits, respectively.

At step306, the first microcontroller130sets a fault line140to a first fault line voltage if at least one of first and second comparator output bits indicate that at least one of the first and second cell voltage levels, respectively, is greater than the first threshold cell voltage level. The fault line140is operably coupled to the second microcontroller132.

At step308, the second microcontroller132sets a first diagnostic indicator flag equal to a first fault value if at least one of the first and second cell voltage levels of first and second battery cells70,72, respectively, is greater than a second threshold cell voltage level.

At step310, the second microcontroller132sets a second diagnostic indicator flag equal to a second fault value if the fault line140has the first fault line voltage.

At step312, the microcontroller132opens contactors42,44electrically coupled to the battery module40if either the first diagnostic indicator flag is equal to the first fault value or the second diagnostic indicator flag is equal to the second fault value.

At step320, the first microcontroller130transmits the first and second comparator output bits from the first and second voltage comparators, respectively, to the second microcontroller132.

At step322, the first microcontroller130measures a module output voltage level of the battery module40.

At step324, the first microcontroller130transmits the module output voltage level to the second microcontroller132.

At step326, the second microcontroller132sets a third diagnostic indicator flag equal to a third fault value if at least one of the first and second comparator output bits indicate at least one of the first and second cell voltage levels, respectively, is greater than the first threshold cell voltage level.

At step328, the second microcontroller132sets a fourth diagnostic indicator flag equal to a fourth fault value if the module output voltage level is greater than a threshold module output voltage level.

At step330, the second microcontroller132opens the contactors42,44electrically coupled to the battery module40if either the third diagnostic indicator flag is equal to the third fault value or the fourth diagnostic indicator flag is equal to the fourth fault value.

At step332, the second microcontroller132sets a module over-voltage diagnostic trouble code equal to a first trouble code value if the first diagnostic indicator flag is equal to the first fault value, and the fourth diagnostic indicator flag is equal to the fourth fault value, and transmits the module over-voltage diagnostic trouble code to the vehicle microcontroller134.

At step334, the second microcontroller132sets a first cell over-voltage diagnostic trouble code equal to a second trouble code value if the first diagnostic indicator flag is equal to the first fault value, and the fourth diagnostic indicator flag is not equal to the fourth fault value, and transmits the first cell over-voltage diagnostic trouble code to the vehicle microcontroller134. The first cell over-voltage diagnostic trouble code is associated with at least one of the first and second battery cells70,72.

At step336, the second microcontroller132sets a second cell over-voltage diagnostic trouble code equal to a fourth trouble code value if the second diagnostic indicator flag is equal to the second fault value, and the third diagnostic indicator flag is equal to the third fault value, and transmits the second cell over-voltage diagnostic trouble code to the vehicle microcontroller134. The second cell over-voltage diagnostic trouble code is associated with at least one of the first and second battery cells70,72.

At step338, the second microcontroller132sets a microcontroller diagnostic trouble code equal to a third trouble code value if the second diagnostic indicator flag is equal to the second fault value, and the third diagnostic indicator flag is not equal to the third fault value; and transmits the first microcontroller diagnostic trouble code to the vehicle microcontroller134. The microcontroller diagnostic trouble code is associated with the first microcontroller130.

Referring toFIG. 5, a vehicle410includes a battery system420, an electric motor422, and a diagnostic system424. A primary difference between the battery system420and the battery system20is that the battery system420only utilizes a single contactor442electrically coupled between the battery module440and the inverter460, instead of a pair of contactors. Another primary difference between the battery system420and the battery system20is that the battery system420only utilizes a pair of voltage drivers450,452to energize and de-energize the single contactor442, instead of four voltage drivers to energize and de-energize two contactors. The structure and functionality of the diagnostic system424is substantially similar to the diagnostic system24, except that the diagnostic system424will open only the single contactor442if at least one of the first, second, third, and fourth diagnostic indicator flags are set to the first, second, third, and fourth fault values, respectively.

The diagnostic system described herein provides a substantial advantage over other systems and methods. In particular, the diagnostic system performs a first diagnostic test on the battery system20utilizing first and second diagnostic indicator flags determined from first and second hardware sensing devices, respectively. Further, the diagnostic system24performs a second diagnostic test on the battery system20utilizing third and fourth diagnostic indicator flags determined from third and fourth hardware sensing devices, respectively.