System for controlling battery conditions

BACKGROUND

00011. Field of the Invention

0002The present invention generally relates to a system for controlling battery conditions.

00032. Description of Related Art

0004Often network access devices, such as those associated with vehicle telematics systems, will need to operate in emergency situations. This functionality may be necessary whether or not the vehicle power systems are functioning or even connected. Accordingly, back up batteries are typically provided for these network access devices.

0005However, the effectiveness of a battery to supply sufficient power is diminished when the temperature of the battery is close to or below 0° C. The lower temperature increases the output impedance of the battery causing increased voltage drop between the cell and the load when the load current increases. Depending on the battery chemistry, this effect may be more pronounced.

0006The effect of this increased impedance is to reduce the available talk time as the ambient temperature is decreased. For ECALL applications, customers are expecting the ability to maintain a call for up to 11 minutes at −20° C. or 5 minutes at −30° C.

SUMMARY

0007One solution to this problem would be to increase the size and/or capacity of the battery. The main drawback of this is primarily a high cost and larger package size. For an automotive ECALL application, having a smaller package size and lower cost is a distinct advantage.

0008In order to provide the required talk time at temperatures that are expected in an automotive or outdoor environment, using the smallest and lowest cost battery technology, it becomes desirable to maintain the temperature of the battery pack above a minimum operating threshold. This threshold will typically be between −20° C. and +10° C. at ambient temperatures as low as −40° C. Elevating the temperature of the battery pack by 20° C. to 30° C. above ambient can be accomplished by placing a heating element in close proximity to the case of the cell.

0009Battery packs can incorporate some type of temperature sensor which is mounted in close proximity of the battery cell and may even be thermally coupled to the battery cell. This temperature sensor can be used to control when charge and discharge cycles of the back up battery may occur. This same sensor may be used to control the heating element in order to maintain the cell temperature near the desired operating point which would typically be greater than 0° C.

0010In many applications, particularly in a vehicle, it is desired to determine the effective end of life of the battery. This is often accomplished by measuring the output impedance of the cell. One technique used to measure the output impedance is to measure the change in voltage with the battery unloaded and also when a load is connected. By measuring the open circuit voltage as well as the voltage under load and knowing the load impedance, the output impedance of the battery can be calculated.

0011In the system described, the load that is used to perform this diagnostic function may also be used as the heating element. The heating element consists of an etched trace on a flexible substrate so that the shape of the heating element can be contoured to match the shape of the cells being heated. This technique should provide uniform heating throughout the full volume of the cell. This could be similar to heating pads used to heat lead-acid batteries in vehicles.

0012For an ECALL application, it is possible that the event that triggers the call could occur some short period of time after the vehicle has been running. In this case, the heating element can be powered from the vehicle's alternator as the secondary power source so that the maximum capacity of the back up battery can be obtained. As part of the power path management, a switch is used to connect the heating element to either the secondary power source or to the battery pack.

0013There are also use cases where the vehicle will be stored in a cold environment for some duration, perhaps overnight. If the heater is activated only when the ignition switch is in the RUN position, there will be a delay before the back up battery is warmed sufficiently to complete a call. In order to have the back up battery warmed before the vehicle is started, a timer could be used to turn on the heater at some preset time. This timer could be set to trigger at a fixed time every day similar to an alarm clock based on a stored operation profile. A more sophisticated technique would include making the heating time adaptive based on the users habits. In this case, an algorithm would be used to learn the most likely time the vehicle is started each day and to activate the heater at a time before this predicted time so that the heater has sufficient time to heat the battery before the expected start of the vehicle. Of course, the user would have the option to disable this feature if they were concerned with discharging the vehicle battery.

0014The application of this idea could be used in any Telematics product that requires the use of a back up battery used to place a call in the event that the vehicle battery gets disconnected. There is also a potential use in applications where modems are used as a data port to provide diagnostics and operating conditions of remotely located motor-generator sets. Another possible application could be in systems that are deployed outdoors that are normally powered from primary power lines but also require a battery backup system.

0015In the system described, the power for heating the backup battery is coming from a secondary power source. In particular, this could be an engine, either in a vehicle or stationary, with the current for the heating element supplied from an alternator or from a primary power line with current supplied through a transformer and charger.

0016Further objects, features and advantages of this invention will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings and claims that are appended to and form a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

0017<figref idref="DRAWINGS">FIG. 1</figref> is a schematic view of a system including a telematics controller and a network access device;

0018<figref idref="DRAWINGS">FIG. 2</figref> is a schematic view of a system with a telematics controller and network access device implemented within a motor vehicle;

0019<figref idref="DRAWINGS">FIG. 3</figref> is a schematic view of a circuit for controlling battery conditions;

0020<figref idref="DRAWINGS">FIG. 4</figref> is a graph illustrating the call duration provided by a battery with respect to the ambient temperature; and

0021<figref idref="DRAWINGS">FIG. 5</figref> is a graph illustrating the battery capacity with respect the ambient temperature;

DETAILED DESCRIPTION

0022Now referring to <figref idref="DRAWINGS">FIG. 1</figref>, a system <b>100</b> is provided. The system includes a network access device <b>110</b> and a telematics controller <b>112</b>. The network access device <b>110</b> may include a processor <b>114</b> and storage <b>116</b>. The processor <b>114</b> may be a programmable microprocessor or alternatively may be an application specific integrated circuit (ASIC), or other known processor. The storage <b>116</b> may be a memory, for example, random access memory, static memory, or other data storage device. The network access device <b>110</b> may also include a transceiver <b>118</b> which includes a transmitter <b>122</b> and a receiver <b>120</b>. Alternatively, the network access device <b>110</b> may include an independent transmitter and receiver. The transceiver <b>118</b> may be in communication with an antenna <b>124</b>. The transceiver <b>118</b> may communicate with a radio tower <b>128</b> as denoted by line <b>126</b>. The communication <b>126</b> between the network access device <b>110</b> and the radio tower <b>128</b> may comprise one of a plurality of communication modes.

0023The transceiver <b>118</b> in the network access device <b>110</b> may be used for transmitting uplink communications and receiving downlink communication to and from the network <b>130</b> and service center <b>132</b> over the wireless communication link <b>126</b>. The wireless communication link <b>126</b> may use a wireless protocol such as a standard cellular network protocol, for example, transmission control protocol/internet protocol (TCP/IP), Code Division Multiple Access (CDMA), Global System for Mobile Communications (GSM).

0024The radio tower <b>128</b> may be in communication with a service provider <b>132</b> including for example, a network server through a network <b>130</b>. Network <b>130</b> may be an analog network such as a plain old telephone service (POTS) or a digital network for example, Ethernet over transmission control protocol/internet protocol (TCP/IP). In other examples, the network <b>130</b> could be one of several standard cellular communication networks, a satellite-based network, a public switched telecommunication network (PSTN), the Internet, an integrated services digital network (ISDN), and/or other communication networks. The service provider may include a service center to provide telematics applications and services to the vehicle. For instance, the service center may contain operators, content servers and content databases. The content servers for telematics applications and services may include traffic servers, map servers, user profile servers, location information servers, and the like. The content databases for telematics applications and services may include location information, user profiles, traffic content, map content, point-of-interest content, usage history, or other similar data.

0025The network access device <b>110</b> may be in communication with the telematics controller <b>112</b> through a communication interface <b>134</b>. In some implementations the network access device <b>110</b> may be in the same package as the telematics controller <b>112</b>. However, other implementations the network access device <b>110</b> may be provided in a separate package from the package of the telematics controller <b>112</b> and, therefore, may be located in a different area of the vehicle. Various information may be communicated between the telematics controller <b>112</b> and the network access device <b>110</b>.

0026The telematics controller <b>112</b> may include a processor <b>136</b> and storage <b>138</b>. The processor <b>136</b> may be a microprocessor, an application specific integrated circuit, a programmable gate array, or other processor. Further, the storage <b>138</b> may be a memory device for example, random access memory, read only memory, static memory, or may even be a hard drive or optical drive, or other means of data storage. The telematics control <b>112</b> may be in communication with a plurality of other vehicle sensors and devices through a wire harness or over the vehicle bus as denoted by lines <b>140</b>. In addition, the telematics controller <b>112</b> may be in communication with a user interface <b>144</b> as denoted by line <b>142</b>. The user interface <b>144</b> may include a display <b>146</b> and controls <b>148</b> for providing user input such as vehicle parameters into the telematics controller <b>112</b>. Also, the user interface <b>144</b> may include elements such as a keyboard or keypad, one or more control buttons, indicator lights, one or more speakers, a microphone, and any other user interface type elements for telematics applications and services. Optionally, the telematics controller <b>112</b> may also be connected to a positioning unit. The positioning unit could be a system that determines the geographic location of the vehicle such as a global positioning system (GPS) or similar systems.

0027Further, the telematics controller <b>112</b> may be in communication with other vehicle systems, such as the engine control system, the vehicle lock controls, the vehicle safety systems (e.g. seatbelt retractors, airbags, etc.), vehicle entertainment system, or a suspension control system to implement the described functions of the telematics controller <b>112</b> or network access device <b>110</b> based on parameters of such systems.

0028The telematics controller <b>112</b> may be powered by the vehicle battery <b>150</b> as denoted by lines <b>152</b> and <b>154</b>. Alternatively, a voltage converter may be provided to convert from the vehicle battery voltage to a different voltage that may be appropriate for running the telematics controller <b>112</b>. The voltage converter may be included in the package for the telematics controller <b>112</b> or alternatively may be in a separate package between the vehicle battery <b>150</b> and the telematics controller <b>112</b>. The vehicle battery <b>150</b> may also provide power to the network access device <b>110</b>.

0029A circuit <b>158</b> may be included between the vehicle battery <b>150</b> and the network access device <b>110</b>. The circuit <b>158</b> may include a voltage converter to change the voltage provided to the network access device <b>110</b> in lines <b>160</b> and <b>162</b>. In addition, the circuit <b>158</b> may be connected to a network access device battery <b>156</b>. The network access device battery <b>156</b> may be charged while the vehicle is running and may for example, be switched to provide power to the network access device <b>110</b> when power from the vehicle power system (e.g., the battery or alternator) is not available. Further, the circuit <b>158</b> may control the monitoring and periodic powering of the network access device if the vehicle is turned off for a long period of time. Further, the circuit <b>158</b> may control the charging of the network access device battery <b>156</b> at appropriate times according to the environmental variables or the expected use cycle of the vehicle.

0030Now referring to <figref idref="DRAWINGS">FIG. 2</figref>, one possible implementation of the system <b>200</b> is provided within a vehicle <b>230</b>. The network access device <b>210</b> may be provided in the same or a separate package from the telematics controller <b>212</b>. The network access device <b>210</b> may be connected to an antenna <b>214</b>. The antenna <b>214</b> may be representative of a plurality of antennas or a matrix of antennas depending upon the particular communication mode selected. Communication of the network access device <b>210</b> is facilitated with a remote station <b>228</b>, as denoted by line <b>216</b>. As described previously, the remote station <b>218</b> may be in communication with a service provider <b>222</b> including a network server through a network <b>220</b>. The telematics controller <b>212</b> may be in communication with a global positioning device <b>240</b> over the vehicle bus or a custom connection as denoted by line <b>238</b>. The global positioning device <b>240</b>, such as a satellite global positioning system (GPS), may be in communication with an antenna <b>242</b>. The antenna <b>242</b> may be one of a plurality of antennas or a matrix of antennas. Further, the antenna or plurality of antennas represented by reference number <b>242</b> may be the same antennas, as denoted by reference number <b>214</b>. The GPS unit may be in communication with a satellite <b>248</b>, as denoted by line <b>246</b>. As such, the GPS unit <b>240</b> may retrieve positional data for the vehicle or in other implementations <b>240</b> may also represent a general satellite receiver and, therefore, may receive other general broadcast information or communication from the satellite <b>248</b>. The telematics controller <b>212</b> may also be in communication with various other vehicle devices and systems through the vehicle bus, wire harnesses, or other wireless connections, as denoted by line <b>234</b>. The various other devices <b>236</b> may include but are not limited to the engine control system, the vehicle locks, the vehicle safety systems (e.g. seatbelt retractors, airbags, etc.), vehicle entertainment system, or a suspension control system.

0031Now referring to <figref idref="DRAWINGS">FIG. 3</figref>, a system <b>300</b> for controlling conditions of a battery pack <b>310</b> is provided. The battery pack <b>310</b> may include battery cells <b>314</b> for storing electrical energy, as well as, a protection circuit <b>312</b> and a temperature sensor <b>316</b>. The protection circuit <b>312</b> may protect the battery cells <b>314</b> from an excessive surge or depletion in voltage or current that may damage the battery cells <b>314</b>. In addition, the temperature sensor <b>316</b> may be located proximate to battery cells <b>314</b> to provide a temperature of the battery cells <b>314</b>. The battery pack <b>310</b> may serve as a backup battery such as a NAD backup battery <b>156</b> for <figref idref="DRAWINGS">FIG. 1</figref>.

0032A discharge load <b>320</b> may be connected in electrical series connection between a positive terminal <b>350</b> of the battery pack and a negative terminal <b>352</b> of the battery pack. The discharge load <b>320</b> may be a resistive load such as a resistor, but generally will include an impedance along the voltage drop to occur across the discharge load <b>320</b>. In addition, a voltage sensor <b>322</b> may be in parallel electrical connection with discharge load <b>320</b>. As such, the voltage sensor <b>322</b> may measure the voltage between the positive terminal <b>350</b> of the battery pack <b>310</b> and the negative terminal <b>352</b> of the battery pack <b>310</b>, and therefore, correspondingly the voltage drop across the discharge load <b>320</b>.

0033The discharge load <b>320</b> may also be a heating element. For example, the discharge load <b>320</b> may be a resistive heater such that the energy dissipated across the discharge load <b>320</b> is converted into thermal energy for heat. As such, the discharge load <b>320</b> may be in thermal communication with the battery cells <b>314</b> to warm the battery cells and provide an improved energy storage performance. Further, the discharge load <b>320</b> may be connected to the battery cells <b>314</b> directly or through a thermal conductive element.

0034The resistive load acting as a heating element may be distributed across the area of the cell to provide more uniform heating. Using a resistive trace on a flexible substrate, the heating element is designed to surround the cell or battery pack like an electric blanket. The heating element could also be on a portion of the rigid PCB substrate with the battery mounted in close proximity. In other implementations, the heating element consists of an etched trace on a flexible substrate so that the shape of the heating element can be contoured to match the shape of the cells being heated. This technique should provide uniform heating throughout the full volume of the cell.

0035Switches <b>324</b> and <b>326</b> may be provided between the battery pack <b>310</b> and the discharge load <b>320</b>. Accordingly, each of the switches <b>324</b> and <b>326</b> may selectively connect the discharge load <b>320</b> to the battery pack <b>310</b>. Disconnecting the battery pack <b>310</b> from the discharge load <b>320</b> prevents power draw from the battery cells <b>314</b>. The switch <b>324</b> may be a three connection switch allowing the discharge load <b>320</b> to be connected to either the battery pack <b>310</b> or the secondary power source <b>332</b>. Meanwhile, the switch <b>326</b> may be a two connection switch, for example, to selectively connect the discharge load <b>320</b> to the negative terminal of the battery and an electrical reference such as an electrical ground.

0036The secondary power source <b>332</b> may be the vehicle battery or the vehicle alternator. The secondary power source <b>332</b> may be connected to a battery charger <b>334</b>. The battery charger <b>334</b> may include a power path switch that may connect the battery <b>310</b> to either the secondary power source for charging, the power device <b>330</b> such as the network access device <b>110</b> from <figref idref="DRAWINGS">FIG. 1</figref>, or both. In a normal operation mode, the battery pack <b>310</b> would be isolated from both the secondary power source <b>332</b> and the power device <b>330</b> where the secondary power source <b>332</b> will provide electrical power to the power device <b>330</b>, for example, through the battery charger and power path switch of the battery charger <b>334</b>.

0037In addition, a processor <b>340</b> may be provided to control the operation of the system <b>300</b> and, for example, determine switching between various operational modes such as a normal operation mode, a charging operation mode, and a heating operation mode. In the normal operating mode, the secondary power source <b>332</b> will power the device <b>330</b> while the battery pack <b>310</b> will remain isolated for storing emergency power. Accordingly, the processor <b>340</b> will control switch <b>324</b> as denoted by line <b>348</b> such that the switch <b>324</b> will not connect any of the three points thereby isolating each of the battery pack <b>310</b>, the discharge load <b>320</b>, and the secondary power source <b>332</b> from each other. Further, the processor <b>340</b> will control switch <b>326</b> such that the discharge load <b>320</b> will be disconnected from the electrical reference. The processor <b>340</b> will also periodically connect the discharge load <b>320</b> between the positive terminal <b>350</b> and the negative terminal <b>352</b> of the battery pack <b>310</b> to determine a charge status of the battery cells <b>314</b>. Various test methodologies may be used to determine the battery charging status, for example, the voltage drop across the discharge load <b>320</b> may be indicative of the battery storage capacity and used to determine the battery status.

0038As such, the processor <b>340</b> is in communication with the voltage sensor <b>322</b>, as denoted by line <b>344</b>, to measure the voltage drop across the discharge load <b>320</b> while in connection with the battery pack <b>310</b>. If the voltage drop is below a threshold voltage drop, for example, indicating a low charge battery status, the battery charger <b>334</b> may connect the secondary power source <b>332</b> with the battery pack <b>310</b> for charging purposes. The battery charger <b>334</b> may allow charging of the battery pack <b>310</b> for a predetermined time period or until the voltage sensor <b>322</b> indicates that the battery cells <b>314</b> are sufficiently charged.

0039However, as discussed above, the battery cells <b>314</b> provide the poor performance and charging characteristics at very cold temperatures. As such, the temperature sensor <b>316</b> is in communication with the processor <b>340</b>, as denoted by line <b>342</b>, to provide a temperature indication of the battery cells <b>314</b>. With the temperatures below a threshold temperature, the processor <b>340</b> may control the switches <b>324</b> and <b>326</b> to allow power to be supplied to the discharge load <b>320</b>. For example, the power may be provided from the secondary power source <b>332</b> and, thereby, provide a dual action as a heating element to warm the battery cells <b>314</b>, as well as, facilitating an impedance measurement of the battery. The processor <b>340</b> may control the heating of the battery cells <b>314</b> using the discharge load <b>320</b> until the temperature sensor <b>316</b> indicates that the temperature of the battery cells <b>314</b> has exceeded a threshold temperature. However, it is understood that other parameters may be used to control the heating process for example, a predetermined time period or the voltage measurement from the voltage sensor <b>322</b>.

0040In addition, the processor <b>340</b> may be in communication with a storage device <b>350</b> to retrieve information indicating the time of usage of the vehicle including such information as typical operation times, length of operation associated with the various operation times, ambient temperature conditions associated with the operation times, and other similar associations. Accordingly, the processor <b>340</b> may determine based on the described information if operation, for example a drive or other usage, is expected in the near future. Further, the processor <b>340</b> may determine a heating schedule based on the above noted parameters. As such, the processor <b>340</b> may check the battery status using the voltage sensor <b>322</b> or may preemptively determine to charge the battery cells <b>314</b> in anticipation of expected operation. Accordingly, the processor <b>340</b> may instruct the battery charger <b>334</b> to charge the battery back <b>310</b> based on the anticipated operation.

0041Based on a temperature sensor measurement, the information from the database <b>350</b>, or both, the processor <b>340</b> may use the discharge load <b>320</b> to warm the battery cells <b>314</b> above a threshold temperature prior to charging the battery pack <b>310</b>. Further, the processor <b>340</b> may utilize discharge load <b>320</b> to warm the battery cells <b>314</b> in anticipation of and during the operation to improve the storage performance of the battery cells <b>314</b> independent of the charging of the battery pack <b>310</b>. Again, the heating of the battery cells <b>314</b> for battery performance purposes may also be based on one of the temperature sensors <b>316</b> and/or the information from the data store <b>350</b>.

0042Now referring to <figref idref="DRAWINGS">FIG. 4</figref>, a graph of the call duration provided by a battery is provided graphically with respect the ambient temperature. As discussed previously, the battery performance and, therefore, the call duration does degrade at low temperature conditions. This principle is illustrated in the curves <b>410</b> and <b>412</b>. Line <b>410</b> represents the call duration for a lithium ion battery, whereas, the line <b>412</b> represents the call duration for a metal hydride battery. Significant battery degradation for both battery types can be seen around the 0° C. temperature range.

0043Now referring to <figref idref="DRAWINGS">FIG. 5</figref>, a graph of the available capacity of the battery is plotted with regard to ambient temperature. Line <b>510</b> illustrates the available capacity of a lithium ion battery whereas, line <b>512</b> illustrates the capacity of a nickel metal hydride battery. The lithium ion battery provides better normalized capacity performance especially in the −20 to −30 temperature ranges, both batteries provide a 0% normalized capacity around the negative 35° temperature range. Accordingly, there is a significant benefit from using the discharge load <b>320</b> as a heating element to increase the temperature of the battery pack prior to charging or anticipating use of the battery.

0044In other embodiments, dedicated hardware implementations, such as application specific integrated circuits, programmable logic arrays and other hardware devices, can be constructed to implement one or more of the methods described herein. Applications that may include the apparatus and systems of various embodiments can broadly include a variety of electronic and computer systems. One or more embodiments described herein may implement functions using two or more specific interconnected hardware modules or devices with related control and data signals that can be communicated between and through the modules, or as portions of an application-specific integrated circuit. Accordingly, the present system encompasses software, firmware, and hardware implementations.

0045In accordance with various embodiments of the present disclosure, the methods described herein may be implemented by software programs executable by a computer system. Further, in an exemplary, non-limited embodiment, implementations can include distributed processing, component/object distributed processing, and parallel processing. Alternatively, virtual computer system processing can be constructed to implement one or more of the methods or functionality as described herein.

0046Further, the methods described herein may be embodied in a computer-readable medium. The term “computer-readable medium” includes a single medium or multiple media, such as a centralized or distributed database, and/or associated caches and servers that store one or more sets of instructions. The term “computer-readable medium” shall also include any medium that is capable of storing, encoding or carrying a set of instructions for execution by a processor or that cause a computer system to perform any one or more of the methods or operations disclosed herein.

0047As a person skilled in the art will readily appreciate, the above description is meant as an illustration of the principles of the invention. This description is not intended to limit the scope or application of the invention in that the invention is susceptible to modification, variation and change, without departing from spirit of the invention, as defined in the following claims.