Method and apparatus for high-voltage battery array monitoring sensors network

[0002] This application claims the benefit of the U.S. Provisional Application Serial No. 60/288,158, filed May 2, 2001, Docket No. 56363-137 (PSIK-016PR), entitled BATTERY ARRAY MONITORING SENSORS AND NETWORK, invented by Daniel D. Friel and Louis Hruska, which application is hereby incorporated by reference in its entirety.

[0003] The invention relates to battery power-control and, more particularly, to battery monitoring.

[0004] Flashlights, handheld computers, and cellular telephones are not the only devices that are “battery-operated.” Large-scale battery installations are used, for example, as backup power sources in the telecommunications industry and in uninterruptable power supplies. Because these applications are inherently reliability-sensitive (these are backup applications, after all), it is essential to monitor the state of such batteries. In order to thoroughly monitor the status of several cells within a battery, and several batteries within an installation, conventional battery monitoring systems may distribute sensors throughout the battery stacks and run several wires from each cell to a central battery monitor. The complex array of wires that results is not only inconvenient and expensive to install and maintain, it also poses a hazard to personnel and equipment. Some monitoring systems reduce the expense and hazard associated with such an installation by reducing the number of cells monitored, proportionally reducing the number of connecting wires strung to the central monitor. Although some cost savings and reduction in hazard may be achieved by this approach, there is a concomitant reduction in battery monitoring information. This dearth of battery information may lead to costly, otherwise avoidable, battery faults and can result in power outages and loss of service.

[0005] A system and method for monitoring a battery permits relatively easy interconnection of monitoring units and, at the same time, provides thorough monitoring of the battery components would therefore be highly desirable.

[0006] A battery-monitoring system in accordance with the principles of the present invention includes one or more cell sensor modules linked to a battery sensor module via a “power-isolated” network. In turn, one or more battery sensor modules may be linked to an alarm interface. A battery-monitoring system in accordance with the principles of the present invention may form a hierarchical system that includes one cell-sensor module per battery cell, with all the cell sensor modules linked to a battery sensor module and, in a multi-battery configuration, all the battery sensor modules linked to an alarm interface that provides access to the external world, in the form of a workstation that operates as a site monitor, for example.

[0007] Each cell sensor module may be configured to fit between the terminals of a cell and to attach to cell terminals via spring-clips and tabs. Each cell sensor module may include one or more sensors that sense a cell-related physical parameter, a signal conditioner, a controller, and a communications interface. The one or more sensors may be voltage or temperature sensors, for example, and the signal conditioner may include circuitry configured to amplify, offset, scale-adjust or otherwise enhance the raw signal provided by the one or more sensors. Additionally, the signal conditioner may include one or more analog-to-digital-converters (ADCs) configured to convert the conditioned sensor signals from the one or more sensors from analog to digital form. A single ADC with multiplexed input may be used to convert multiple sensor inputs, for example. The cell sensor module's controller, which may take the form of an embedded microprocessor core within an application specific integrated circuit, for example, may initiate the conversion of sensor signals from analog to digital form and store the results of such conversions. The controller may also perform analytical operations, such as averaging values obtained by the sensors, determining peak sensor values, and logging events such as the excursion of a sensor signal beyond one or more thresholds. The controller may also exercise control over the communications interface, receiving messages from the interface and formatting responses through the interface. In order to ensure survivability of the communications link while, at the same time, employing a relatively simple, economical, serial topology, the communications link is “power-isolated.” That is, the local and link sides of the interface employ separate power sources. The local side of each communications interface receives power from the cell to which the sensor module is attached and the link side of the communications interface receives power from a central source, such as the battery sensor module, for example. In this way, the failure of an individual battery cell will not “bring down” the entire communications network.

[0008] A battery sensor module may be configured to fit between a battery terminal and a load; attached, for example, to a bus bar that provides the conductive path from the battery to the electrical load. Each battery sensor module may include one or more sensors that sense a battery-related physical parameter, a signal conditioner, a controller, and a communications interface. The one or more sensors may be voltage, temperature, or current sensors, for example, and they are connected to measure corresponding battery-level values. That is, unlike a cell sensor module, which is configured to monitor the voltage, temperature or other parameter of an individual cell within a battery, a battery sensor module is configured to measure, for example, the voltage and discharge current, of the entire assemblage of cells that constitute a battery. The battery sensor module's signal conditioner may include circuitry configured to amplify, offset, scale-adjust or otherwise enhance the raw signal provided by the one or more sensors. Additionally, the signal conditioner may include one or more ADCs configured to convert the conditioned sensor signals from analog to digital form. A single ADC with multiplexed input may be used to convert multiple sensor inputs. The battery sensor module's controller, which may take the form of an embedded microprocessor core within an application specific integrated circuit, may initiate the conversion of sensor signals from analog to digital form and store the results of such conversions. The controller may also perform analytical operations, such as averaging values obtained by the sensors, determining peak sensor values, and logging events such as signal excursions beyond thresholds. The controller may also exercise control over the communications interface: receiving messages from the interface and formatting responses to the interface. The battery sensor module's controller may query the various cell sensor modules within the battery, analyze sensor output and/or reduced data from the various cell sensor modules, and provide information to the alarm interface related to the status of the cells under its purview.

[0009] The alarm interface includes a communications interface for communicating with one or more battery sensor modules. The alarm interface provides a link between each cell and each battery in an installation and the external world. The external world may take the form, for example of a workstation that operates as a site monitor, for example. The alarm interface may include a user interface that permits input from and output to a user, directly, through visual and/or audio signals, or remotely, through a communications link.

[0010] In an illustrative embodiment, the isolated data interface includes opto-isolators at each cell sensor module and at the batter sensor module. The opto-isolators provide separation between the electrical power system of each cell sensor module and the electrical power system of the link, which obtains power from the battery sensor module. Additionally, in this illustrative embodiment, the topology of the battery cell communications link is a daisy-chained serial link, with its physical layer in compliance with the RS485 communications standard.

[0011] The new battery-monitoring system may be particularly useful in high-capacity battery installations, such as those employed in telecommunications systems and uninterruptable power supplies, for example. The new system is also useful in high-voltage mobile battery applications, such as hybrid electric vehicles (HEVs) which require precise monitoring and management but employ large high-voltage battery arrays.

[0012] The above and further features, aspects, and advantages of the invention will be apparent to those skilled in the art from the following detailed description, taken together with the accompanying drawings in which:

[0013] FIG. 1 is a block diagram of a battery-monitoring system in accordance with the principles of the present invention;

[0014] FIG. 2 is a block diagram of a cell sensor module in accordance with the principles of the present invention;

[0015] FIG. 3 is a block diagram of a battery sensor module in accordance with the principles of the present invention; and

[0016] FIG. 4 is a conceptual layout of a battery power system that includes a battery-monitor in accordance with the principles of the present invention.

[0017] The conceptual block diagram of FIG. 1 illustrates a battery-monitoring system 100 in accordance with the principles of the present invention. This illustrative battery monitoring system 100 monitors two batteries 102, 104 with respective battery sensor modules 106, 108 interfaced to an external interface 110 (also referred to herein as an alarm interface). Each battery sensor module 106, 108 is linked with respective cell sensor modules 110, 112, 114, 116 and 118, 120, 122, 124 through respective isolated-power, daisy-chained, serial data networks 126, 128. In this illustrative embodiment, the topology of the battery cell communications network is that of a daisy-chained serial link, with its physical layer in compliance with the RS485 communications standard. The cell sensor modules monitor, store, and report data related to physical parameters, such as voltage or temperature, associated with the respective cell. The battery sensor modules monitor physical measurements related to an array of cells that constitutes a battery. In addition to measuring battery-level voltage and current drain, for example, the battery sensor module gathers information from each of the cell sensor modules to accumulate information related to the overall state of the battery and to the state of individual cells within the battery. The cell sensor and/or battery sensor modules may perform various data reduction operations, such as averaging or peak detection, for example. The alarm interface 110 links the battery monitoring system to the outside world through a site monitor, system controller or other, centralized controller. The alarm interface 110 may interpret data and analyses from a plurality of battery sensor modules and pass this information along to a site monitor or other outside world devices. The alarm interface 110 may include a user interface that permits input from and output to a user, directly, through visual and/or audio signals, or remotely, through a communications link. The battery-monitoring system 100 may be contained within a high-voltage mobile battery system within a hybrid electric vehicles (not shown), or a telecommunications office (not shown), for example.

[0018] The block diagram of FIG. 2 illustrates the components of a cell sensor module 200 in accordance with the principles of the present invention. In this illustrative embodiment, the cell sensor module 200 includes a temperature sensor 202 and a voltage sensor 204 respectively configured to measure the temperature and voltage of the cell to which they are attached. A signal conditioner 208 includes circuitry that operates on the raw signals provided by the sensors 202, 204 to amplify, offset, scale-adjust or otherwise enhance the raw signals provided by the sensors 202, 204 as necessary for proper conversion from analog to digital form by the ADC 210. The ADC 210 includes a multiplexed input that permits the sequential conversion of the temperature and voltage signals. A controller 212, which may be an embedded core microprocessor, for example, controls the operation of the ADC 210 by selecting which sensor's signal is to be converted. Additionally, the controller 212 may store the results of such conversions, for example in nonvolatile memory 214, such as electrically erasable programmable read only memory (EEPROM). The controller 212 may also perform analytical, data reduction, operations, such as averaging values obtained by the sensors, determining peak sensor values, and logging events such as the excursion of a sensor signal beyond a threshold. The controller 212 may also exercise control over a communications interface 216: receiving messages from the communications interface 216 and formatting responses to the interface.

[0019] The communications interface 216 obtains power from two separate sources. On the “cell” or “local” side, the interface 216 obtains power from the cell to which the cell sensor module 200 is attached. On the “link” or “remote” side, the interface 216 obtains power from the battery of which the cell is a part. The battery-power is distributed through a link, along with data lines that form a part of the daisy-chained serial network (e.g., network 130). In this illustrative embodiment, the interface 216 includes an opto-isolator 218 that operates as a serial communications transceiver. The opto-isolator 218 includes transmitter/receiver pairs that are powered by cell power on the local side of the interface and by battery power in the remote side of the link. In each communications direction, a photo-transmitter (e.g., a light emitting diode) transforms digital electronic signals into pulses of light and transmits the pulses to a photo-receiver (e.g., a photodiode). Because the photo-transmitter and photo-receiver receive power from separate sources, the failure of an individual cell will not “bring down” the entire communications network 130. Additionally, the network interface 216 does not rely upon the cell side of the interface to regenerate network traffic. That is, a pass-through in the network interface 216, powered by the remote side (Batt+, Batt−), ensures the continuity of the network, even in the event of a failure on the local side, such as the failure of the cell that supplies local power (Cell+, Cell−).

[0020] The cell sensor module 200 may include modes of operation, such as a low power consumption, or “hibernation”, mode in which operations are curtailed to save operating power. For example, the sensor measurements and/or analog to digital conversion of sensor signals may be performed less frequently in such a mode. Voltage and temperature measurements may be compared with thresholds values, such as minimum or maximum values, with any excursions beyond the threshold levels stored in the non-volatile memory 214. The controller 212 may perform calculations on the sensor values, such as averages, deviation limits, or time beyond a threshold, for example. The measurements may be taken in response to a command from an associated battery sensor module. Additionally, the measurements may be taken at the behest of the controller 212 as determined, for example, during an initial configuration. A cell sensor module may be integral to a battery cell, in that it may be directly attached to a cell and remain attached to the cell for the cell's duration.

[0021] The block diagram of FIG. 3 illustrates a battery sensor module 300 in accordance with the principles of the present invention. Such a battery sensor module 300 may be configured to fit between a battery terminal and a load, attached, for example, to a bus bar that provides the conductive path from the battery to the electrical load. Such a sensor module is described, for example, in U.S. Pat. No. 6,304,062 B1, issued Oct. 16, 2001, to Batson, which is hereby incorporated by reference. In this illustrative embodiment, the battery sensor module 300 includes a temperature sensor 302, a voltage sensor 304, and a current sensor 305 respectively configured to measure the temperature, voltage, and current of the battery to which they are attached. A signal conditioner 308 includes circuitry that operates on the raw signals provided by the sensors 302, 304, 305 to amplify, offset, scale-adjust or otherwise enhance the raw signal provided by the sensors 302, 304, 305 as necessary for proper conversion from analog to digital form by the ADC 310. The ADC 310 includes a multiplexed input that permits the sequential conversion of the temperature, voltage, and current signals.

[0022] A controller 312, which may be an embedded core microprocessor, for example, controls the operation of the ADC 310 by selecting which sensor's signal is to be converted. Additionally, the controller 312 may store the results of such conversions, for example in nonvolatile memory 314, such as electrically erasable programmable read only memory (EEPROM). The controller 312 may also perform analytical operations, such as averaging values obtained by the sensors, determining peak sensor values, and logging events such as the excursion of a sensor signal beyond a threshold. The controller 312 may also exercise control over a communications interface 316, receiving messages from the communications interface 316 and formatting responses to the interface. Because the battery sensor module 300 is monitoring the entire battery, rather than a single cell within the battery, the communications interface 316, need not employ a two-power system. The battery sensor module's controller 312 may query the various cell sensor modules within the battery (through the network 130), analyze sensor output obtained from the various cell sensor modules, and provide information to the alarm interface related to the status of the battery and cells it is monitoring.

[0023] The battery sensor module 300 provides power Batt+, Batt− to the serial network that links the battery- and cell-sensor modules. In an illustrative embodiment, a battery sensor module may be mounted on the negative terminal plate of a battery stack, with a power input and voltage sense lead attached to the battery stack's positive terminal plate. The battery sensor module may command associated cell sensor modules to measure their respective cell temperature and voltages at predetermined times, then read the results and compile a relatively complete picture of the battery status. The battery sensor module may then analyze the assembled data (including data obtained from the battery sensor module's sensors), to calculate and predict the performance of the battery.

[0024] The new battery-monitoring system may be particularly useful in high-capacity battery installations, such as those employed in telecommunications systems and uninterruptable power supplies, for example. The conceptual physical layout of FIG. 4 may be employed in such an installation. An illustrative battery stack 400 includes twenty-four two-volt cells connected in series through bus-bars, such as bus bar 401, to yield a forty-eight volt potential across the positive 402 and negative 404 terminal plates. A battery sensor module 406, as previously described, is mounted on the negative terminal plate 404. A power input and voltage sense lead (not shown) is attached from the battery sensor module 406 to the battery stack's positive terminal plate 402. A cell sensor module, such as module 408, is attached to each of the cells. A serial, power-isolated, network link 410 connects the cells.

[0025] Although various exemplary embodiments of the invention have been disclosed, it will be apparent to those skilled in the art that various changes and modifications can be made which will achieve some of the advantages of the invention without departing from the spirit and scope of the invention. It will be evident to those reasonably skilled in the art that other components performing the same functions may be suitably substituted. Further, the methods of the invention may be achieved using software implementations, using the appropriate object or processor instructions, or in hybrid implementations that utilize a combination of hardware logic, software logic and/or firmware to achieve the same results. The specific configuration of logic and/or instructions utilized to achieve a particular function, as well as other modifications to the inventive concept are intended to be covered by the appended claims.

[0026] The foregoing description of specific embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed, and many modifications and variations are possible in light of the above teachings. The embodiments were chosen and described to best explain the principles of the invention and its practical application, and to thereby enable others skilled in the art to best utilize the invention. It is intended that the scope of the invention be limited only by the claims appended hereto.