THERMAL WAKEUP FOR BATTERY MANAGEMENT SYSTEM CONTROLLER

A monitoring circuit for a battery system of a work machine includes a system controller configured to operate in a low power mode when the battery system is inactive, a sensing circuit element configured to produce an electrical sensor signal representative of an environmental parameter of the battery system, and a wakeup circuit configured to generate a controller activation signal when the sensor signal indicates that the environmental parameter is outside of a specified operating range. The system controller is configured to initiate a controller boot operation in response to the controller activation signal.

TECHNICAL FIELD

This document relates to electric powered work machines and in particular to techniques of managing the battery systems of electric powered work machines.

BACKGROUND

Powering a large moving work machine (e.g., a wheel loader) with an electric motor requires a large mobile electric energy source that can provide current of hundreds of Amperes (Amps). This large mobile energy source can include multiple large capacity battery cells connected in parallel as battery strings that provide the sustained energy power needed by a large electric-powered moving work machine. It may be desirable to ensure that the performance or the lifetime of the large capacity battery cells aren't compromised by environmental conditions.

SUMMARY OF THE INVENTION

Electric powered large moving work machines use large capacity battery systems that may remain idle for periods of time when the work machine is not in use. It would be useful to avoid environmental conditions that can impact the performance and lifetime of the batteries, but monitoring the status of the battery system shouldn't impact battery life through extra energy drain.

An example monitoring circuit for a battery system of a work machine includes a system controller configured to operate in a low power mode when the battery system is inactive, a sensing circuit element configured to produce an electrical sensor signal representative of an environmental parameter of the battery system, and a wakeup circuit configured to generate a controller activation signal when the sensor signal indicates that the environmental parameter is outside of a specified operating range. The system controller is configured to initiate a controller boot operation in response to the controller activation signal.

An example method of monitoring a battery system of a work machine includes operating a system controller in a low power mode when the battery system is powered down, monitoring an environmental parameter of the battery system using the system controller in the low power mode, detecting when the environmental parameter is outside of a specified operating range, operating the system controller in an active mode in response to the detecting that the environmental parameter is outside of the specified operating range when the battery system is powered down, and the system controller initiating a corrective action to bring the environmental parameter to within the specified operating range.

An example battery system of a work machine includes at least one battery pack including multiple battery cells; a system controller, and a monitoring circuit. The monitoring circuit includes a sensing circuit element configured to produce an electrical sensor signal representative of temperature of the battery cells, and a comparator circuit configured to generate a controller activation signal when the sensor signal indicates that the temperature of the battery cells is outside of a specified operating range. The system controller is configured to initiate a corrective action in response to the controller activation signal.

DETAILED DESCRIPTION

Examples according to this disclosure are directed to methods and systems for automatic monitoring a battery system of a work machine. Monitoring the environmental conditions of the battery system allows for predictive maintenance to avoid negative impact on the performance of the battery system.

FIG.1depicts an example machine100in accordance with this disclosure. InFIG.1, machine100includes frame102, wheels104, implement106, and a speed control system implemented in one or more on-board electronic devices like, for example, an electronic control unit or ECU. Example machine100is a wheel loader. In other examples, however, the machine may be other types of machines related to various industries, including, as examples, construction, agriculture, forestry, transportation, material handling, waste management, and so on. Accordingly, although a number of examples are described with reference to a wheel loader machine, examples according to this disclosure are also applicable to other types of machines including graders, scrapers, dozers, excavators, compactors, material haulers like dump trucks, along with other example machine types.

Machine100includes frame102mounted on four wheels104, although, in other examples, the machine could have more than four wheels. Frame102is configured to support and/or mount one or more components of machine100. For example, machine100includes enclosure108coupled to frame102. Enclosure108can house, among other components, an electric motor to propel the machine over various terrain via wheels104. In some examples, multiple electric motors are included in multiple enclosures at multiple locations of the machine100.

Machine100includes implement106coupled to the frame102through linkage assembly110, which is configured to be actuated to articulate bucket112of implement106. Bucket112of implement106may be configured to transfer material such as, soil or debris, from one location to another. Linkage assembly110can include one or more cylinders114configured to be actuated hydraulically or pneumatically, for example, to articulate bucket112. For example, linkage assembly110can be actuated by cylinders114to raise and lower and/or rotate bucket112relative to frame102of machine100.

Platform116is coupled to frame102and provides access to various locations on machine100for operational and/or maintenance purposes. Machine100also includes an operator cabin118, which can be open or enclosed and may be accessed via platform114. Operator cabin118may include one or more control devices (not shown) such as, a joystick, a steering wheel, pedals, levers, buttons, switches, among other examples. The control devices are configured to enable the operator to control machine100and/or the implement106. Operator cabin118may also include an operator interface such as, a display device, a sound source, a light source, or a combination thereof.

Machine100can be used in a variety of industrial, construction, commercial or other applications. Machine100can be operated by an operator in operator cabin118. The operator can, for example, drive machine100to and from various locations on a work site and can also pick up and deposit loads of material using bucket112of implement106. As an example, machine100can be used to excavate a portion of a work site by actuating cylinders114to articulate bucket112via linkage110to dig into and remove dirt, rock, sand, etc. from a portion of the work site and deposit this load in another location. Machine100can include a battery compartment connected to frame102and including a battery system120. Battery system120is electrically coupled to the one or more electric motors of the machine100.

FIG.2is a block diagram of a battery system120. The battery system120can be included in a mobile energy source used to provide power to an electric motor of a work machine, such as the example machine100ofFIG.1. The battery system120includes multiple battery cells224(e.g., two to eight battery cells) connected in parallel. The battery cells224are large capacity battery cells (e.g., a 750 Volt, 80 Amp-hour battery, or 60 kilowatt-hours). The battery cells224may be included in one battery pack or multiple battery packs connected in parallel in the battery system120. The battery system120also includes a system controller226. The system controller226includes circuitry to perform tasks such as bringing the battery cells online and to monitor the condition of the battery cells224.

FIG.3is a block diagram of portions of an example of an energy system300for a work machine. The energy system300includes an energy storage system320(e.g., the battery system ofFIG.2) that can include an energy source322such as one or more battery packs that each include one or more battery cells. The energy system can include a second separate energy source323independent of the energy storage system320. The energy system300also includes a system controller226to manage the energy storage system. The “OR” block324inFIG.3represents that system controller226could be powered using the energy storage system320it is managing or the system controller226can be powered using a separate energy source323to power the system controller226. The separate energy source323is independent of the energy storage system320, and may have a different voltage potential than the energy storage system320.

When the system controller226is in an active mode, the system controller226brings the energy storage system320online to provide electrical power to the work machine and monitors operation of the energy storage system320, such as to identify faults, change a configuration of the cells of the energy storage system320, and the like.

When the energy storage system320is not being utilized, it is desired to not have the system controller226continuously operating in order to reduce the energy drain by an idle energy system. However, it is still desired to monitor the physical characteristics of the energy storage system320. For example, it may desired to monitor the ambient air temperature or the temperature of individual components of the energy storage system to avoid excessively high or low temperatures that can impact the energy storage system320.

The system controller226may include processing circuitry (e.g., processing unit328) that includes logic to perform the functions described. The processing circuitry may include a microprocessor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), or other type of processor, interpreting or executing instructions in software or firmware stored in memory. The energy storage system320includes one or more sensing circuit elements330to provide an electrical sensor signal representative of one or more physical characteristics of one or more components of the energy storage system320.

To monitor the energy storage system320, the system controller226is placed in a low power mode. In lower power mode, the number of circuits of the system controller226that are active is reduced. For example, the processing circuitry may be powered down or set to an idle mode in which functionality of the system controller226is reduced. In the low power mode, enough circuitry remains active in system controller226to monitor one or more physical characteristics of the energy storage system320.

For instance, the system controller226includes an interface332to the sensing circuit element330. This interface332may remain active while other circuitry of the system controller226is in low power mode and is inactive. In some examples, the interface332includes a wakeup circuit334. The wakeup circuit334is active in the low power mode and includes logic that generates a controller activation signal when the sensor signal indicates that the environmental parameter is outside of a specified operating range. The system controller226becomes active in response to the controller activation signal.

The system controller226includes a main supply circuit336and a bootstrap supply circuit338. The main supply circuit336provides power to the system controller226in normal operation. In low power mode, the main supply circuit336may be powered down or disconnected from some or all of the circuitry (e.g., the processing unit328) of the system controller226. The bootstrap supply circuit338may provide the power to the circuits (e.g., the wakeup circuit334) that remain active in the low power mode. The controller activation signal enables the main supply circuit336activating the processing unit328. Upon activation, the processing unit328may initiate a controller boot operation.

In response to activation, the system controller226may initiate a corrective action to bring the environmental parameter to within the specified operating range. In some examples, the sensing circuit element330is a temperature sensing circuit element that produces a sensor signal representative of temperature of one or more components (e.g., one or more battery cells) of the energy storage system320. The wakeup circuit334generates the activation signal when the sensing circuit element330indicates a temperature that is outside of a specified temperature range (i.e., the environmental temperature of the energy storage system is too hot or too cold for ideal operation or to preserve lifetime of the battery cells).

In response to the activation signal, the system controller226may determine the temperature status using the sensor signal (e.g., by determining a voltage level of the sensor signal) to determine whether the temperature is above the specified temperature range or below the specified temperature range. If the sensor signal indicates the temperature is below the temperature range, the system controller226may activate a heating system340to bring the energy storage system to a predetermined temperature. If the sensor signal indicates the temperature is above the temperature range, the system controller226may activate a cooling system342to bring the energy storage system320to a predetermined temperature.

In some examples, the cooling system342is a liquid cooling system that circulates a non-conductive liquid to cool the battery cells. Based on the sensor signal, the system controller226may activate the cooling system342to bring the temperature of the energy storage system320to a predetermined temperature.

In some examples, the sensing circuit element330is a fluid level sensing element that produces a sensor signal representative of fluid level of the cooling system. The wakeup circuit334generates the activation signal when the fluid sensing circuit element indicates the fluid level is below a specified fluid level. In response to the activation signal, the system controller226may determine the fluid level status using the sensor signal. The system controller226may initiate adding more nonconductive liquid coolant to the one or more battery cells when the fluid level is below the specified fluid level range (e.g., by activating a remote control valve), or the system controller226may generate an alert that indicates a technician should service the energy storage system320.

In some examples, the system controller226stores information associated with the environmental parameter being outside of the specified operating range in response to the controller activation signal. The information may include an identifier of the parameter, the value of the parameter, and one or both of the date and time of the excursion. In certain examples, the information includes the effect on the State of Health (SOH) of one or more battery cells of the energy storage system. The health and longevity of the battery cells are affected by exposure to extremes (e.g., extreme temperatures) and has a likelihood to affect the Warranty Coverage of the battery cells.

FIGS.4A-4Bshow detailed circuit schematics of circuits that can be included in the interface332of the system controller226.FIG.4Aincludes an example of a wakeup circuit434. The wakeup circuit434receives the sensor signal on an input450, and the wakeup circuit434includes a window comparator circuit to determine of the sensor signal is within the specified signal range. The signal range is specified by voltages applied to one input of the comparators with the other input of the comparators electrically connected to the wakeup circuit input450. The output of the window comparator circuit is used to generate the activation signal output452that goes to other portions of the system controller226.

As part of its activation, the processing unit328of the system controller226may check the output of the sensing circuit element330to determine an environmental status of the energy storage system320. The interface332can include a filter circuit454that filters the sensor signal that is used by the processing unit328to determine status of the energy storage system320and determine a corrective action. In certain examples, the filter circuit454is a single-pole low-pass filter circuit.

FIG.4Bincludes an example of a bootstrap supply circuit448that supplies power to one or more circuits of the interface332that are active in the low power mode.FIG.4Balso includes a reverse battery protection circuit458and an inductor-capacitor LC filter circuit460connected between the reverse battery protection circuit and the bootstrap supply circuit.

The systems, devices and methods described herein provide a technique for monitoring the environmental conditions of the energy storage system to ensure proper performance and life cycle of the components of the energy storage system. The monitoring is achieved with the system controller in a lower power state or off state to minimize energy drain when the energy storage system is not in use.

INDUSTRIAL APPLICABILITY

FIG.5is a flow diagram of an example method of real time monitoring of the environment conditions of a battery system of a work machine. At block505, a system controller of the battery system is operated in a low power mode when the battery system is powered down or otherwise disabled and not operated. Most of the circuitry of the system controller is powered down in the low power mode.

At block510, an environmental parameter of the battery system is monitored using the system controller in the low power mode. An example of the environmental parameter is temperature. At block515, while in the low power mode the system controller detects when the environmental parameter is outside of a specified operating range.

At block520, the system controller is enabled and operated in an active mode in response to the detecting that the environmental parameter is outside of the specified operating range while the battery system is powered down. At block525, the activated system controller performs a corrective action to bring the environmental parameter to within the specified operating range.