Integral battery temperature control system

An integral battery temperature control system monitors and heats a battery to enable operation in cold environments and utilizes a heating device coupled to one of the terminals of the battery to heat the terminal and thereby heat the electrode coupled thereto. The heated electrode is within the battery housing and internally heats the battery. A temperature sensor measures the temperature of the opposing terminal and a controller will terminate heating when the measured temperature of the opposing terminal rises above an upper threshold temperature value. The heating device be coupled with or be part of a discharge circuit, wherein electrical current from the battery is used to heat the battery. A discharge circuit is part of a battery unit monitoring module that balances the voltage of a plurality of battery units. The heating device may include a resistor or a transistor of the discharge circuit.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention is directed to a battery temperature control system comprising a battery temperature monitor and a heating system, and particularly to a heating system that is integral with a battery management system.

Background

Lithium batteries do not effectively accept a charge when below about 0° C. and cannot effectively discharged when below −20 C. These temperatures can vary however based on the type of use. When lithium batteries are used in cold temperature environments, insulated enclosures are sometimes utilized along with auxiliary heaters. These measures require addition volume around the batteries and/or an auxiliary power source.

Current battery management systems obtain data about individual battery units in a battery system. The systems reserve addresses for communication with battery unit sensors and/or battery units. When sensors transmit data about battery units to the management system, the sensors include the address of the battery unit. Such a system may require significant amounts or resources and complex arrangements for connecting the components of the system.

As shown inFIG. 19, lithium batteries have a non-linear discharge profile, with a relatively flat discharge region up to about 80% discharged. Therefore, a small change in voltage can mean a large difference in the state of charge, unlike a lead acid battery that has a relatively linear drop in voltage as the battery is discharged. The state of charge of a lead acid battery, and therefore the amount of power remaining, is more easily monitored by a UPS system by simply monitoring the voltage of the lead acid battery. The amount of power remaining in a lithium battery system is more difficult to monitor and predict however by simply measuring voltage. It would therefore be more difficult to determine the available power remaining in a lithium battery unit by simply measuring the voltage.

Current charging systems are configured to charge a battery pack to a predetermined voltage. However, the individual battery may not be charged to the same level, and the discrepancy between the batteries state of charge levels can cause capacity to be limited. The battery pack capacity is limited to the capacity of the lowest battery unit. Additionally, when some battery units have lower state-of-charge levels, as the battery discharges, those units may discharge to a level resulting in permanent loss of charging capacity.

SUMMARY OF THE INVENTION

The invention is directed to a battery temperature detection and heating system and particularly to a heating system that is integral with a battery management system. An exemplary battery heating system has a heating device that is coupled to a terminal of a battery and a temperature sensor that is coupled to the opposing terminal. Heat is conduct from the terminal through an electrode within the battery housing to heat the battery internally, while the battery temperature is measured on the opposing terminal. When a battery drops below a lower threshold temperature value a discharge circuit, which may be part of the battery management system and incorporated with the battery unit monitoring module, may be activated to flow current to a heating device, such as an electrically resistive heater or a transistor. When the temperature rises above an upper threshold temperature value, the flow of current through the discharge circuit may be terminated by a controller. A discharge circuit flows current between the terminals of a battery to reduce the voltage of the battery and bring to a voltage that is closer to the other batteries in the battery unit or pack.

The control system may turn on the battery heating circuit when a temperature sensor measures a temperature of the battery that is below a lower threshold temperature value and in some cases only when the state of charge of the battery is above a threshold value to prevent discharging the battery and further reducing the battery voltage. In addition, the battery heating circuit may be turned-off by the controller if while activated, the voltage of the battery drops below a lower threshold value; again, to prevent further reduction of the battery voltage by a draw of current to the heater. In still another embodiment, the battery heater may have a time limit, wherein the battery heater is activated for a period of time and then shuts off. A battery heater circuit may have a user override, or a means to prevent the battery heater from being activated, such as a manual switch, or a selection that is input to the controller, such as through a user interface.

In an exemplary embodiment, a battery management system, comprises a program to determine the state of charge of a battery unit or battery, or the amount of available charge remaining. The calculation takes into account the battery unit or pack voltage prior to the utilization of battery power as the output power. The program utilizes input related to the power being drawn by the powered device, such as current, voltage and time, and calculates the total power usurped from the battery pack. The program can then calculate the discharge percent of the battery pack, as depicted inFIG. 19. A power control system may calculate the time remaining before the battery pack is discharged 80% and may send an alert via a data transmission system of the remaining time before shut-down. A power control system may shut-down the battery pack if a discharge level of 80% or more is reached, for example, in an effort to protect the system and prevent damage to the battery pack.

An exemplary battery unit may comprise a plurality of cell units comprising a positive electrode separated from a negative electrode by a separator. Each cell unit creates electrical current and are configured in an electrolyte. In an exemplary embodiment, the cell units are planar, wherein the electrodes are planar having a first side and a second side. A positive electrode may be configured between two separators and two negative electrodes on opposing sides of the positive electrode to produce a dual cell unit. A dual cell unit has one electrode configured between two opposing electrodes. This alternating configuration of positive and negative electrodes enables just one of the electrodes, that is heated, to transfer heat to the opposing electrodes quickly and effectively. For example, the positive terminal may be heated by a heating device and each of the planar positive electrodes may conduct heat thereby distributing the heat within the cell. Since the positive electrodes are sandwiched between negative electrodes, heat will be quickly conducted throughout the cell. As the negative electrodes rise in temperature, the temperature sensor coupled with the negative electrode will communicate the temperature measured to a controller. When the temperature rises above an upper threshold temperature, the current flow to the heating device may be terminated. The lower threshold temperature value may be above a temperature when a battery will not effectively charge or discharge, such as above 0° C., or above −20° C., for example. In an exemplary embodiment, the lower threshold temperature value is about 0° C. or more, or about 5° C. or more, about 10° C. or more, about 10° C. or less, about 5° C. or less and any temperature between and including the values provided. The battery may be heated until the temperature of the terminal or terminal connector opposite the terminal that is heated, reaches an upper temperature threshold value. This upper temperature threshold value may be higher than the lower temperature threshold limit to prevent the heating circuit from turning on and off frequently in cold environments. An upper temperature threshold value may be greater than the lower temperature threshold limit by about 5° C. or more, about 10° C. or more for example.

A heating device may be coupled directly with a terminal of the battery or to a portion of an electrode, or electrode connector, wherein heat is conducted to the electrode within the battery housing. The electrode acts as an internal heating element, wherein the electrode is within the battery housing and heats the battery from the inside. An electrode connector may electrically connect an electrode with a terminal, and may extend between a plurality of planar electrodes, as shown and described herein. A heating device may be a discharge circuit that is utilized by a battery unit monitoring module and/or battery management system to regulate the state of charge of a battery. In some cases, when a plurality of batteries are employed in a battery system, it may be important to keep the state of charge of each battery within some range of the other batteries, thereby preventing overcharging or over-discharging one of the batteries. A discharge circuit may be used to discharge a battery to reduce a state of charge and bring the state of charge of the battery down to within an acceptable range of the other batteries.

An exemplary battery management system includes a battery unit monitoring module that is utilized for obtaining data about battery units in a battery pack. A computing device can obtain the data by sending a data request to the first monitoring module. The first monitoring module obtains and transmits data about its connected battery unit to the computing device and sends a data request to the second monitoring module. The second monitoring module obtains and transmits data about its connected battery to the computing device and sends a data request to the next monitoring module. Each successive monitoring module performs the same steps until all the monitoring modules have sent data about their connected battery units to the computing device. Thus, the computing device needs solely a data request port and input data port(s) to obtain the data for a battery pack.

In one aspect, the present disclosure describes a battery management system. The battery management system includes a computing device with an output data request port and an input data port. The battery management system also includes first and second battery unit monitoring modules, each battery unit monitoring module connected to the input data port of the computing device. In response to a data request from the output data request port of the computing device, the first battery unit monitoring module transmits data of the first battery unit to the input data port of the computing device, and transmits a data request to the second battery unit monitoring module. In response to the data request from the first battery unit monitoring module, the second battery unit monitoring module transmits data of the second battery unit to the input data port of the computing device.

The first battery unit monitoring module can connect to a first battery unit in a battery pack of an electric vehicle. The battery management system can also include wiring connecting the computing device to the battery unit monitoring modules. Because the battery units in a battery pack can be wired in series, the physical locations of the positive and negative terminals arranged in an alternating fashion, the second battery unit monitoring module is oriented in an opposite direction from the first battery unit monitoring module.

The first battery unit monitoring module can include an analog-to-digital converter. The analog-to-digital converter can measure a voltage of the first battery unit. The first battery unit monitoring module can include a temperature monitoring device that measures a temperature of the first battery unit. The temperature can be expressed as a voltage which is applied to an input of the analog-to-digital converter. Data of the first battery unit can be a voltage and a temperature of the first battery unit. Data of the second battery unit can be a voltage and a temperature of the second battery unit.

The computing device can scan the first and second battery unit monitoring modules to determine a number of battery unit monitoring modules in the battery management system. The computing device can transmit a second data request to the first battery unit monitoring module after the computing device has not received data on the input data port for a predetermined period of time. The predetermined period of time may be 20 ms. The computing device can include an analog-to-digital convertor that measures a voltage across the first and second battery units. The computing device can include an analog-to-digital convertor that measures a current flowing in the first and second battery units.

The computing device can output an alarm when an error condition is detected. The error condition can be a high voltage condition, a low voltage condition, a high current condition, a high temperature condition, or a connection fault condition. The computing device can shut off a battery charger when the computing device detects a high voltage condition across the first and second battery units. The computing device can shut off a motor controller when the computing device detects a low voltage condition across the first and second battery units.

The battery management system can include a monitor, such as a video monitor, that displays the data of the first and second battery units. The battery management system can include a connection fault detector that detects a connection between a node at a zero-voltage reference level and the first and second battery units. The battery management system can include one or more battery unit balancing systems, each system balancing charge in a battery unit.

In another aspect, the present disclosure describes a battery management system with a computing device and first and second battery unit monitoring modules. The computing device includes a first output data request port and an input data port. The first battery unit monitoring module includes a first input data request port connected to the output data request port of the controller, a first output data port connected to the input data port of the controller, and a second output data request port. The second battery unit monitoring module includes a second input data request port connected to the second output data request port of the first battery unit monitoring module, and a second output data port connected to the input data port of the controller.

In another aspect, the present disclosure describes a method of managing a battery. The method includes transmitting, by a computing device, a first data request to a first battery unit monitoring module. The method also includes transmitting, by the first battery unit monitoring module, data of a first battery unit to an input data port of the computing device in response to the first data request. The method also includes transmitting, by the first battery unit monitoring module, a second data request to a second battery unit monitoring module. The method also includes transmitting, by the second battery unit monitoring module, data of a second battery unit to the input data port of the computing device in response to the second data request.

The entirety of the following patents are incorporated by reference herein: U.S. Pat. No. 8,723,482 issued on May 13, 2014 and entitled Battery Unit Balancing System; U.S. Pat. No. 9,595,847, issued on Mar. 14, 2017 and entitled Uninterrupted Lithium Battery Power Supply System; U.S. Pat. No. 9,371,067, issued on Jun. 21, 2016 and entitled Integrated Battery Control System; and U.S. Pat. No. 9,553,460, issued on Jan. 24, 2017 and entitled Wireless Battery Management System; all are assigned to Elite Power Solutions LLC.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The present disclosure describes, among other things, certain embodiments of a battery management system. The management system obtains and displays data about battery units in a battery pack. The management system can monitor the voltage and temperature of the individual battery units and/or the entire battery pack. If the management system discovers any of the battery units pose a concern (e.g., the voltage is over or under limits, or the battery unit is overheating), the system can take measures to prevent damage to itself or the battery pack or to alleviate the concern. The system can also take comparable measures if the system detects a connection between any of the battery units and ground. Thus, the battery management system can maintain the consistent operation of the system the battery pack powers, such as an electric vehicle.

Referring now toFIG. 1, a block diagram of an exemplary embodiment of a battery management system100connected to a battery pack190is shown and described. The battery management system100includes battery unit monitoring modules105(e.g., sense boards), a computing device110, and a display115(e.g. a monitor such as an LCD monitor or a monitor incorporated into another device, such as a DVD player). The computing device110can measure voltage and/or current for the entire battery pack190and output the data to the display115. In various embodiments, the computing device110can determine the state of charge of the battery pack190by measuring the amount of current that flows in or out of the battery pack190. The battery pack190can integrate the amount of current to determine the state of charge. In some embodiments, when the battery pack190reaches a minimum, predetermined voltage, the computing device110can set the pack's190state of charge to about 0%. When the battery pack190reaches a maximum, predetermined voltage, the computing device110can set the state of charge to about 100%.

In some embodiments, the battery pack190may Include a plurality of battery units195(e.g., battery cells). Each battery unit may include a battery cell or a plurality of battery cells. The battery pack190can connect to an external load198, such as a motor for an electric vehicle. Each battery unit monitoring modules105of the management system100can connect to a battery unit195. A monitoring module105can obtain data, such as voltage and/or temperature, for the battery unit195connected to the module105. The monitoring modules105can transmit the data to the computing device110, which can output the data to the display115.

In some embodiments, the computing device110may be configured to operate with a predetermined, fixed number of battery unit monitoring modules105. In some embodiments, the computing device110may be configured to scan the modules105to determine the number of modules105present. The computing device110can scan the battery unit monitoring modules105to determine the number of monitoring modules105in the system100. For example, in some embodiments, the computing device110can output a scan signal to the first monitoring module105. In response, the monitoring module105can return battery unit voltage and temperature data to the computing device110and can output a scan signal to a successive monitoring module105. In some embodiments, the monitoring module105can also return battery unit voltage and temperature data to the computing device110, and can output a scan signal to the next module105. Thus, the computing device110can count the number of monitoring modules105by the number of voltage and temperature data packets received. Further, the computing device110can number a monitoring module105and/or battery unit195based on the module's105or unit's195position in the order of scan signals received. In some embodiments, a user can configure the computing device110to set the number of monitoring modules105or to instruct the device110to scan the modules105and obtain the number of modules itself.

The computing device110can detect error conditions for individual battery units195and/or the entire battery pack190. Exemplary error conditions can include conditions such as high voltage conditions, low voltage conditions, high current conditions, and high temperature condition. Another exemplary error can be a connection fault condition, e.g., a connection between at least one battery unit195and a contact point with a zero-voltage reference level, such as a chassis of an electric vehicle.

When an error is detected, the computing device110can initiate a measure based on the error condition. For example, if the computing device110detects a high voltage condition for the entire battery pack190, the computing device110can inactivate a device that charges the pack190(not shown). In another example, if the computing device110detects a first low voltage condition, the computing device110can output a low voltage warning to the display115. If the battery pack's190voltage drops further, triggering a second low voltage condition, the device110can inactivate a load connected to the battery pack190, such as a motor controller of an electric vehicle.

Referring now toFIG. 2, a block diagram of an exemplary arrangement of battery unit monitoring modules105and battery units195in a pack190is shown and described. In this embodiment, the monitoring modules105are connected to the battery units195, which are connected in series. Each monitoring module105can be connected to a single battery unit195. The battery unit195can supply the connected monitoring module105with power for performing its operations.

FIG. 3is a block diagram depicting connections within the battery management system100between the computing device110and the battery unit monitoring modules105. The computing device110includes an output data request port (also referred to herein as an “enable output”) and an input data port. Each monitoring module105includes an output data port, an input data request port (also referred to herein as an “enable input”), and an output data request port. Each monitoring module's105output data port is connected in parallel to the computing device's110input data port.

The computing device's110output data request port is connected to the first one of the battery unit monitoring module's105ainput data request port. The monitoring module's105aoutput data request port is connected to the input data request port of the successive monitoring module105b. In turn, the monitoring module's105boutput data request is connected to the input data request port of the next monitoring module105c. The remaining monitoring modules105are connected in the same manner. The communications of the computing device110and battery unit monitoring modules105described herein are transmitted from and received at these ports, as would be understood by one of ordinary skill in the art. Further, in various embodiments, the computing device110and monitoring modules105include voltage and ground connections such that the computing device110can provide power (e.g., 12V) and ground to the monitoring modules105.

In operation, to obtain data about the battery units195, the computing device110sends a data request signal (also referred to herein as an “enable signal” or an “enable pulse”) to the first battery unit monitoring module105a. In response, the monitoring module105etransmits data about a connected battery unit195ato the computing device110. After the module105afinishes transmitting data, the module105asends a data request signal to the second battery unit monitoring module105b. In response, the monitoring module105btransmits data about a connected battery unit195bto the computing device110. After the module105bfinishes transmitting data, the module105bsends a data request signal to the third battery unit monitoring module105c, and the process continues for the rest of the monitoring modules105.

Using this communication system, the computing device110can match data with a battery unit according to the order in which the device110receives data. Thus, the first set of data can be matched to the first battery unit195a, the second set of data to the second unit195b, and so forth. In this manner, the computing device110uses few ports for obtaining data and matching the data to battery units195. In some embodiments, such a battery management system100may eliminate the needs for dedicated addressing ports, addressing switches, and/or jumpers.

When the computing device110does not receive data from a battery unit195for at least a predetermined period of time (e.g., 20 ms, although other times may be used), the computing device110can conclude that data collection for the battery pack190has been completed. The computing device110can obtain another set of data by transmitting another data request to the first battery unit monitoring module105a, thereby restarting the data collection process. In some embodiments, the computing device110can collect data about the battery units195, e.g., once per 1-2 seconds.

In some embodiments, the computing device110can first compare the number of data received with the number of monitoring modules105. If the numbers match, the computing device110can determine all the monitoring modules105are operational and continue obtaining data about the battery units195. If the numbers do not match, the computing device110can conclude that at least one monitoring module105and/or battery unit195is not operational. The computing device110can generate and output an error message to the display115. Since the modules105transmit data to the computing device110in sequential order, the computing device110can identify the non-operational module105or unit195according to the number of data received. In this manner, the computing device110can inform a user of physical locations of faults in the monitoring modules105or battery pack190, allowing the user to troubleshoot problems.

Regarding the individual monitoring modules105, in some embodiments, a module105can measure data for a connected battery unit195upon receiving a data request signal. In some embodiments, a module105can measure and store data in a buffer. Then, when the module105receives the data request signal, the module105may access the buffer and may transfer the data stored therein to the computing device110.

The monitoring module105can transmit the data to the computing device110in a human readable form. The monitoring modules105can transmit the data via an asynchronous serial protocol, such as protocols used for RS-232 or USB connections. The monitoring modules105can transmit the data at any rate and with any number of start and/or stop bits. For example, a module105can transmit at 9600 Baud with 1 start bit and 1 stop bit.

Referring now toFIG. 4, a diagram depicting connections between battery unit monitoring modules105is shown and described. In some embodiments, wiring400(e.g., ribbon cable, 4-wire round shape harnesses) can be used to connect the monitoring modules105to one another. In some embodiments, for each monitoring module105, the output data port can be located in the center of a module's105interface. In some embodiments, the input data request port and the output data request port can be symmetrically located on opposite sides of the output data port. By orienting each battery unit monitoring module105in an opposite direction from adjacent modules105, wiring400can connect the output data request port of one module105to the input data request port of the successive module105. Due to the orientation of the ports, the wiring400need not be twisted or folded. Further, the wiring400can connect all the output data ports to the input data port of the computing device110. When a monitoring module105transmits data for its connected battery unit195, the data can be sent across each portion of wiring400connecting the monitoring modules105before the data arrives at the computing device110.

FIG. 5is a hybrid block and circuit diagram depicting an exemplary battery unit monitoring module105. The monitoring module105includes terminals502and503, a microprocessor505, a reverse connection protection system510, a battery unit balancing system515, a voltage regulator520, resistors525,526for sampling a battery unit's195voltage, and a temperature monitoring device527(e.g., a thermistor) for sampling a battery units195temperature. The monitoring module105also includes a receiver540for receiving a data request signal from a computing device110or monitoring module105, a driver541for transmitting data of the connected battery unit195to the computing device110, and a driver542for transmitting a data request signal to another monitoring module105.

A battery unit195connects to the monitoring module105at terminals502and503. Thus, the battery unit195applies its voltage to the reverse connection protection system510. If the voltage is sufficiently high, the protection system510conducts and applies the voltage to the voltage regulator520, resistors525,526, temperature monitoring device527, and balancer515. If the battery unit195is improperly connected to the terminals502,503(e.g., with incorrect polarity), the reverse connection protection system510does not conduct, thereby protecting the module105from potentially damaging voltages.

When the protection system510conducts, the voltage regulator520can draw upon the battery units195voltage to supply a stable voltage (e.g., 2V) for the monitoring module105. In particular, this voltage can power the microprocessor505. The microprocessor505can obtain the battery unit's195voltage via resistors525and526and/or the temperature via temperature monitoring device527. In some embodiments, the microprocessor505can sample the values on the resistors525,526and temperature monitoring device527to obtain the voltage and temperature. The microprocessor505can store the values in an internal memory.

In some embodiments, when the receiver540receives a data request signal, the receiver540transmits the signal to the microprocessor505. In response, the microprocessor505obtains the voltage and temperature of the battery unit195, either by measuring the values on the resistors525,526and temperature monitoring device527or by accessing stored values in an internal memory. The microprocessor505transmits the values to the driver541, which drives the values back to the computing device110via, for example, asynchronous serial ASCII communication. At substantially the same time, the microprocessor505can generate and output a data request signal to the driver542. The driver542drives the data request signal to the next monitoring module105for obtaining data about its connected battery unit195.

Referring now toFIG. 6, a circuit diagram of an exemplary embodiment of a battery unit monitoring module105is shown and described. In this embodiment, the terminals602,603correspond to the terminals502,503ofFIG. 5. The protection system510can be a metal-oxide-semiconductor field effect transistor (MOSFET)605, such as a p-type MOSFET. Terminals of the battery unit195can connect to both the source and base of the MOSFET605. When the battery unit's195voltage is sufficiently high, the voltage activates the MOSFET605. As the MOSFET605conducts, the battery unit195applies its voltage to the voltage regulator610. If the battery units195voltage is insufficiently high, or its polarity is reversed, the MOSFET605does not conduct, thereby protecting the module105from potentially damaging voltages. In this manner, the MOSFET605can operate as a low voltage drop diode.

The voltage regulator610can be an integrated circuit (e.g., a LP2951) which can use a transistor611, two operational amplifiers612,613, and two resistors614,615to regulate a voltage. Resistors616,617can divide the output of the voltage regulator610to, for example, 2V. The divided voltage can be fed back to the error amplifier612, and the regulator610can adjust the output accordingly. In this manner, the voltage regulator610can output a substantially constant voltage. The capacitor618can filter the divided voltage before supplying the voltage to a microprocessor620. Further, a power supply can power a clock generator (with capacitors623,624, an oscillator625, resistor626, and buffers627,628) to generate a clock signal. The clock signal can be provided to the microprocessor620for its operations.

The battery unit195can connect, via the terminals602,603, to resistors629,630and a thermistor631. A node between the resistors629,630and a node adjacent to the thermistor631can connect to input ports of the microprocessor620, which in turn can connect to an internal analog-to-digital converter (also referred to herein as A/D converter). One of the inputs to the internal A/D converter can sample the voltage between the resistors629,630to determine the voltage of the battery unit195. Another input to the internal A/D converter can sample the temperature of the battery unit195, expressed as a voltage, via the thermistor631. The microprocessor620can store the voltage and temperature in an internal memory. In some embodiments, the microprocessor620connects to separate A/D converters that sample the voltage and temperature.

The microprocessor620can receive a data request signal via the receiver640(e.g., an optocoupler). In response, the microprocessor620can obtain the voltage and temperature of the battery unit195and transmit the values to the driver641, which drives the values back to the computing device110. At substantially the same time, the microprocessor620can generate and output a data request signal. The data request signal can connect to the base of a transistor650. When the signal turns on the transistor, current flows through the driver642to output another data request signal to the next monitoring module105.

FIG. 7is a circuit diagram of an exemplary embodiment of an interface700for the computing device110. The interface700can be used by the computing device110for communicating with to battery unit monitoring modules105. The computing device110can apply a data request signal to the gate of a transistor705, such as a metal-oxide-semiconductor field-effect transistor (MOSFET). In response, the transistor705conducts and current flows from the voltage source710through the resistors715,716. The voltage that develops at the node between the resistors715,716activates the transistor720. As a result, current flows from the voltage source710through the transistor720and resistor721to output a data request signal (e.g., a logic high signal) for the first battery unit monitoring module105.

The circuit can receive a data signal (e.g., as 12V signal) through the TX pins on a connector. Resistors725,726can divide the data signal, and the Zener diode730can clamp the data signal to a voltage substantially equal to the voltage supplied to the battery unit monitoring module's microprocessor (e.g., 3.3V). An inverter735, such as a Schmitt Trigger inverter, can eliminate noise and sharpen the rise and fall times of the divided and/or clamped data signal before passing the data signal to the microprocessor of the computing device110.

In various embodiments, the interface700can be located on the same board as the other components of the computing device110. In some embodiments, the communication interface can be isolated from those other components.

FIG. 8is a circuit diagram of an exemplary embodiment of a balancing unit800of a battery unit monitoring module105. The operation of the balancing unit is described in U.S. application Ser. No. 12/939,889, entitled “Battery Unit Balancing System,” filed Nov. 4, 2010, the contents of which are hereby incorporated by reference in their entirety.

FIG. 9is a block diagram depicting an exemplary embodiment of the computing device110of the battery management system100. The computing device110can include a central processing unit (CPU, e.g. 8-core processor)905and a memory910(e.g., electrically erasable programmable read-only memory, or EEPROM serial memory) that stores a program with executable instructions. The program can be loaded into the memory910from an external device connected via, for example, the bus interface965or a USB cable. The CPU905can load and execute instructions from the memory910to perform its operations. The program may include configuration data, such as the predetermined number of battery unit monitoring modules105in the system100or the threshold battery unit voltage or temperature that would trigger an error condition. In some embodiments, the program may obtain the configuration data from values input by a user of the system100.

The computing device110can use an analog-to-digital (A/D) converter915to measure the voltage of the battery pack190. The A/D converter915can sample the voltage to obtain a value. The computing device110can use an analog-to-digital (A/D) converter916to measure the current of the battery pack190. In some embodiments, the A/D converter916is connected to a shunt, which in turn is connected to a terminal of the battery pack190and a terminal of the external load198. The shunt can be a resistor that develops a voltage drop proportional to the battery pack's190current (e.g., 0.0001 Ohms developing a voltage drop of 0.1 mV/A). An amplifier917can amplify the value of the current before the A/D converter916samples the current. The A/D converters915,916can direct the battery pack voltage and current to an isolation barrier920controlled by a signal from a connection fault detector925. In some embodiments, the A/D converters915,916are on the same board as the CPU905, isolated, and/or both.

The connection fault detector925can signal the presence of a connection between a battery unit195and a zero-voltage reference level. For example, the zero-voltage reference level can be the battery pack's190enclosure or chassis, and the connection between a battery unit195and the chassis would represent a hazard to service personnel. When one or more battery units195within the battery pack190contacts a point at the zero-voltage reference level, the contact can cause current to flow from the battery unit195. The connection fault detector925detects the connection and outputs a signal to the CPU905which will display a warning indicating this connection on the display device115.

The CPU905can connect to the battery unit monitoring modules105to obtain data about the individual battery units195, as described in reference toFIGS. 3-5. The CPU905can process data about the individual battery units195and/or battery pack190to create a composite video signal. A digital-to-analog (D/A) converter930(e.g., a 3-bit converter) can produce the composite video signal from digital to analog format so the signal can be displayed on a display115.

If the CPU905detects an error condition, the CPU905can transmit an error signal to an alarm output system940. The system940can be used to control a component and/or device that responds to the error signal (e.g., a charger that stops charging the battery pack190, or a motor controller of an electric vehicle that stops discharging the battery).

The computing device110can include power supplies960(not shown onFIG. 9). The power supplies960supply voltages to components of the battery management system100. In some embodiments, a power supply960can include an internal voltage regulator to provide a constant voltage. The power supplies960can be isolated from the other components of the computing device110to prevent damage to the device110.

The computing device110can include an interface965, such as a controller area network (CAN) interface. The interface can include ports, such as parallel port pins. The computing device110can connect to external devices via an interface (not shown). For example, the device110can connect to another computing device to receive a program to be stored in the memory910.

The computing device110can include a port970for receiving a page select signal. A page can correspond to a format for displaying data about a battery unit195within the battery pack190. For example, one page can display the data for the entire pack190. Another page can display the voltages and temperatures of eight, twenty, or any other number of battery units195. Successive pages can display the same information for adjacent sets of battery units195. The computing device110can receive the page select signal from a switch mounted in a dashboard in an electric vehicle, for example (not shown). In response, the computing device110can output the selected page containing battery pack data to the display115.

FIG. 10is a block diagram depicting an exemplary embodiment of the alarm output system940of the computing device110. The alarm output system940receives an error signal from the computing device110. The alarm output system940outputs a binary signal according to the error signal. If the error signal corresponds to an off signal, the system940allows current to flow to a ground reference, thereby outputting a logic low signal (e.g., 0V). If the error signal corresponds to an on signal, the system940allows current to flow from a voltage source, such as 12V. In some embodiments, the system940does not allow current to flow until the error signal lasts at least 30 seconds. In this manner, the system940turns on or off external devices according to the presence of an error.

FIG. 11is a circuit diagram depicting an exemplary embodiment of the alarm output system940of the computing device110. The alarm output system940includes a voltage source1101, two resistors1103,1104, four transistors (e.g., metal-oxide-semiconductor field-effect transistors or MOSFETs)1105,1106,1107,1108configured to form an H bridge, and two transistors1120,1121that operate the alarm output system940. Transistors1105,1108can be of opposite polarity from transistors1106,1107. The alarm output system940can apply one or more received error signals to the transistors1120,1121and output one or more command signals corresponding to the error signals at terminals1130,1131.

In operation, an error signal can be applied to transistor1120and/or transistor1121. If the computing device110detects a low voltage condition, the device110can apply an error signal to transistor1120. As transistor1120conducts, the voltage applied to the gates of transistors1107,1108by the voltage source1101drops. The voltage differential between the source and gate of transistor1107decreases to turn the transistor1107off. The voltage differential between the source and gate of transistor1108increases to turn the transistor1108on. As transistor1108conducts, current flows from the voltage source1101through the transistor1108to the output terminal1130. The voltage that develops on the output terminal1130can be used to shut off a motor controller, by way of example.

If the computing device110detects a high voltage condition, a high current condition, or a high temperature condition, the device110can apply an error signal to transistor1121. As transistor1121conducts, the voltage applied to the gates of transistors1105,1106by the voltage source1101drops. The voltage differential between the source and gate of transistor1106decreases to turn the transistor1107off. The voltage differential between the source and gate of transistor1108increases to turn the transistor1105on. As transistor1105conducts, current flows from the voltage source1101through the transistor1105to the output terminal1131. The voltage that develops on the output terminal1130can be used to shut off a battery charger or turn on a fan, by way of example.

FIG. 12is a circuit diagram depicting an exemplary embodiment of the connection fault detection system of the computing device. The connection fault detection system includes an optocoupler1205with a light emitting diode1210and a transistor1215, such as a phototransistor. One terminal of the light emitting diode1210connects to ground (also referred to herein as “a node at a ground zero reference lever”), such as a chassis of an electric vehicle. The other terminal of the light emitting diode1210connects to a current sink1220. One terminal of the transistor1215connects to a voltage source1225. The other terminal connects to a node corresponding to the output1228of the optocoupler1205(also referred to herein as the “output node”). This node connects to a resistor1230that also connects to a ground zero reference level, which can be electrically isolated from the battery pack190. The current sink1220connects to the negative terminal of a voltage source1235. The positive terminal of the voltage source1235connects to the negative terminal of at least one battery unit195of the battery pack190.

In operation, when none of the terminals of the battery units195connect to ground, current does not flow through the light emitting diode1210of the optocoupler1205. The light emitting diode1210does not activate the transistor1215, and the transistor1215does not conduct. Because the node1228corresponding to the optocoupler's1205output is disconnected from the voltage source1225, any charge at the node drains through the resistor1230to ground. In this manner, the optocoupler1205outputs a logic low signal, such as 0V, indicating that a connection fault has not been detected.

When a positive terminal of a battery unit195does connect to a zero-voltage reference level, current flows through the light emitting diode1210to the current sink1220. The current activates the transistor1215so the transistor1215conducts. Current flows from the voltage source1225, building charge at the output node1228. Thus, the optocoupler1205outputs a logic high signal indicating that a connection fault has been detected. The logic high signal can be applied to CPU905, which can output a message to the display device warning an operator of the battery unit management system of a potentially hazardous connection fault.

The voltage sources1225,1235can have any voltage. For example, voltage source1225can provide 3.3V. Voltage source1235can provide 5.0V. The current sink1220can limit the current flowing through itself and the light emitting diode1210to any current, such as a minimum safe level of current. For example, the current sink1220can limit the current to 2 mA. The current sink1220can operate over a range of voltages of the battery pack190, such as the voltages between the battery pack's190positive and negative terminals. In some embodiments, this range can be from about 5V to about 500V. In some embodiments, the current sink1220can operate at voltages that exceed the voltage at the positive terminal of the battery pack190.

FIG. 13is another circuit diagram depicting an exemplary embodiment of the connection fault detection system of the computing device. This embodiment includes all the components described in reference toFIG. 12. In addition, in this embodiment, the current sink1220includes a voltage source1305, a first resistor1310, a first transistor1315, a second transistor1320, and a second resistor1325. The voltage source1305connects to one terminal of the first resistor1310. The other terminal of the first resistor1310connects to the gate of the first transistor1315and the emitter of the second transistor1320. The source of the first transistor1315connects to the optocoupler1205. The drain of the first transistor1315connects to the base of the second transistor1320and one terminal of the second resistor1325. The other terminal of the second resistor1325connects to the collector of the second transistor1315and the negative terminal of the voltage source1235.

In operation, current flows from the voltage source1305through the first resistor1310to activate the first transistor1315such that the first transistor1315conducts. When a terminal of a battery unit195connects to ground, current flows through the optocoupler1205, the first transistor1315, and the second resistor1325. The voltage that develops across the second resistor1325activates the second transistor1320. As the second transistor conducts1320, current is diverted from the gate of the first transistor1315. The transistors1315,1320and resistors1310,1325reach equilibrium such that a constant current flows through the first transistor1315.

The transistors1315can be any type of transistor, such as a metal-oxide-semiconductor field-effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), or a NPN transistor. In some embodiments, a 2N3904-type transistor is used for the second transistor1320.

FIG. 14is a circuit diagram depicting an exemplary embodiment of the pack voltage and pack current input systems of the computing device. The battery pack190can connect to the systems at terminals1401,1402. Resistors1405,14068,1407,1408,1409,1410can divide the battery pack190voltage from 500V to 2V, by way of example. A capacitor1411can filter the divided voltage, and an A/D converter1415can sample the voltage. The A/D converter1415can transmit the voltage to a processor of the computing device110, such as CPU905. Optocouplers1420,1421,1422can create an isolated communication interface between the A/D converter1415and the processor.

The voltage drop across a shunt can be input at terminal1430. The operational amplifier1435, resistors1436,1437, and capacitors1438,1439,1440can form an amplifier to amplify the voltage drop. Because the amplifier has a fixed gain, such as 80, the amplified voltage may exceed the capacity of the A/D converter1445that samples the voltage. Thus, resistors1447,1448can form a voltage divider that divides the amplified voltage to a level the A/D converter1445can process. The A/D converter1445can sample the voltage and transmit the voltage to the processor, which can calculate the battery pack190current based on the value of the shunt. The A/D converter1445can use the same communication interface as the A/D converter1415to transmit its sampled voltage.

FIG. 15is a circuit diagram depicting an exemplary embodiment1500of the central processing unit905of the computing device110. Resistors1501-1519, capacitors1520-1527. Zener diodes1530-1532, and inverters1535-1537condition the inputs and outputs for the central processing unit1550.

FIG. 16is a circuit diagram1600depicting an exemplary embodiment of a power supply that can be used with the battery management system100. The power supply1600can be a step down switching voltage regulator. The components1601-1616can operate to produce a voltage, such as 5V or 12V. In particular, component1612can be a linear voltage regulator that accepts a voltage produced by the other components of the system and outputs a substantially constant 3.3V.

FIG. 17is a circuit diagram1700depicting an exemplary embodiment of another power supply that can be used with the battery management system100. The power supply1700can be an isolated power supply. Components1701-1708can operate as an oscillator that produces 40 KHz. The transformer with windings1709-1711can transfer energy produced by the oscillator to components1712-1721, which can operate as positive and negative half-wave rectifiers and a shunt regulator. The rectifiers and shunt regulator can operate to produce a substantially constant output voltage.

FIG. 18is a circuit diagram depicting an exemplary embodiment of a controller area network (CAN) interface used with the battery management system100. The interface can be used to connect a CPU905of a computing device110with an external device via a CAN bus. A connector1801can attach to a component of the computing device110, such as the CPU board. The other connector1880can attach to a CAN bus that connects to an external device. The computing device110and external device can communicate over the interface using a standard bus protocol such as a serial peripheral interface (SPI) protocol. In some embodiments, the devices can use handshaking signals, such as receiver buffer full and interrupt.

The interface chip1805can operate in a non-isolated mode or an isolated mode. In the non-isolated mode, the interface chip1805communicates with the bus buffer1810with data received, for example, from an external CAN-enabled device. In some embodiments, the bus buffer1810can receive data from the bus ports1880. The interface chip1805can send a transmit signal to the buffer1810so the buffer1810outputs its data to the bus ports1880. The interface chip1805can send a receive signal so the buffer1810outputs its data obtained from the bus ports to the interface chip1805.

In the isolated mode, an isolator1815isolates the interface chip's1805transmit and receive signals from a buffer1820. The isolator1815can be a magnetic isolator. An isolated power supply1825can use a voltage from a voltage regulator1828to provide power for the isolator1815and buffer1820. In some embodiments, the voltage regulator1828receives a 12V signal and outputs a 5V signal.

In view of the structure, functions and apparatus of the system described herein, the present disclosure provides an efficient and intelligent battery management system. Having described certain embodiments of the battery management system, it will now become apparent to one of skill in the art that other embodiments incorporating the concepts of the disclosure may be used. Therefore, the invention should not be limited to certain embodiments, but should encompass the spirit and scope of the claims.

As shown inFIG. 19, a lithium battery has a non-linear discharge profile. The discharge rate from approximately 5% to 80% of full charge is substantially linear but has a very small slope. Therefore, it is difficult to estimate the state of charge of a battery, or battery unit by measuring the voltage. Small variations in voltage may result in erroneous estimates of the state of charge. As described herein, a power control system may calculate the time remaining before a battery pack should be shut down when being used as the output power supply. The power control system and specifically the computing device may initiate battery shut down if a calculated value of 80% discharged or more is reached.

As shown inFIG. 20, an exemplary lithium battery power supply system10comprises a battery pack12, and a power control system14. The battery pack12has a first battery unit20and a second battery unit20′. A battery data input provides data about the status of the battery unit and batteries configured therein to the computing device52through the battery data input62. A computing device may request data from battery monitoring modules (not shown), through the data request output64. The battery pack is coupled to the power control system14by a battery power input40. An AC power input42is connected to an AC power line or cable. In an exemplary embodiment, the power control system utilizes the AC power for output power unless there is an interruption or disturbance in the incoming AC power. A data transmission system18is configured to send pertinent data related to the battery management system to an external location, such as a monitoring station. A powered device54is connected to the power control system at the power output connector50. The battery management system100controls the charging and discharging of batteries and balances the battery system to prevent large variations between individual battery voltages within a battery pack. A discharge circuit may be used to reduce the voltage of a battery when has a voltage higher than the other batteries in the battery pack. This discharge circuit may be used as a battery heating circuit, wherein a resistor or transistor that heats with current flow acts as the heater for the battery.

As shown inFIG. 21, an exemplary power control system14comprises a plurality of inputs, outputs and indicators. In an exemplary embodiment, a power control system is configured in a single enclosure15, thereby making installation of the battery management system quick and easy. A battery power input40is configured to connect to a battery pack to receive power from said battery pack. A battery on/off switch41may be used to temporarily disable battery power in the event that the system requires maintenance or repair. An AC power switch44is also shown. A power output connector50is configured for providing power to an electronic device and may be any suitable type of plug. An AC power Input42is configured to couple to an AC power line or cable and may also comprise any suitable type of plug. An AC power switch is configured to enable or disable AC power input. A battery data input62is configured to couple to a battery monitoring module to receive data input regarding the battery pack, unit or individual batteries. As described herein a battery data input may be configured to receive a data transmission cable and in some embodiments comprises a wireless signal receiver. A remote data output connector80is configured to couple with a cable or line, such as a phone-line, DSL line, fiber optic line and the like. Again, a remote data output connector may be a wireless signal transmitter that is configured to send data output wirelessly. A number of indicators, such as lights, are also shown, a computing device indicator85, a data reception indicator84, a data transmit indicator83and an AC input indicator82. These indicators may indicate that a particular function is current active.

As shown inFIG. 22, an exemplary battery pack12comprises two battery units20and20′, each having four individual lithium batteries21. The batteries are all connected in series by jumpers27. A jumper27′ connects the first battery unit20with the second battery unit20′. Battery monitoring modules30are configured between the positive28and negative29terminals of the batteries. A battery monitoring module may comprise a voltage sensor34and/or a temperature sensor36. A circuit87on a module30may be configured to determine the voltage state of a battery. Module connectors32connect battery monitoring modules in a daisy-chain configuration. Module connector32′ couples a battery monitoring module from the first battery unit to a battery monitoring module on the second battery unit. A battery power cable26is configured to provide power to the power control system. A battery module cable61is configured to couple with a battery data input, as shown inFIG. 22.

As shown inFIG. 23, an exemplary battery management system100comprises a battery pack12and a power control system14. In this exemplary embodiment, only a battery power cable physically couples the battery pack to the power control system. Data from the battery monitoring modules30is wirelessly transmitted to the power control system. A wireless transmitter66and wireless receiver68are coupled on the battery pack10and transmit battery status information to the control system. Likewise, the control system comprises a wireless transmitter66′ and wireless receiver68′ for requesting battery status information and receiving battery status information respectively. A powered device54is plugged into the power output connector50. An AC power line43is coupled with the power control system.

As shown inFIGS. 24 and 25, an exemplary lithium battery power supply system comprises a positive terminal28and a negative terminal29. The battery monitoring module30is configured between and coupled, electrically with the two terminals. A battery discharge circuit72is coupled with the battery monitoring module and can drain charge from the battery unit20, such as in the event of a charge above a threshold value. This discharge circuit may act as the battery heating circuit700. A voltage sensor34measures the state of charge of the battery unit and communicates this to a power control system, not shown. A temperature sensor36measures the temperature of the battery unit, by measuring the temperature of one of the terminals, the positive or the negative terminal. As described herein, a lithium battery cannot be effectively charged if the temperature is below a threshold charge value and cannot be effectively discharged if the temperature is below threshold discharge value. A controller65of the battery monitoring module, such as a microprocessor67may receive input from the temperature sensor(s) and then control a heating device and a balancing circuit or discharge circuit72to provide a flow of current to heat a heating device75. The heating device75, such as a resistor73or transistor, is in thermal communication with one of the terminals of the battery unit and is heated if the temperature of the battery unit, as measured by the temperature sensor36or37, measures a temperature below at least one of the threshold values, such as a lower temperature threshold value. The heating device may receive a flow of current from the discharge circuit72to heat the heating device75and thereby heat the electrode connected to the heated terminal, the positive terminal28as shown. The heat is transferred into the battery housing38by the electrode, wherein it heats the battery from the interior of the housing, or internally. The heat flow is depicted by the bold arrows. As shown inFIG. 24, the positive electrode58is heated and heat is transferred from the positive electrode through the separator56to the negative electrode59, as indicated by the bold arrows. The heat is then transferred to the negative terminal29where the temperature is measured by the temperature sensor36. Temperature sensor36is coupled with the negative terminal and as the negative electrode59rises in temperature, the negative terminal also rises in temperature until it is above at least one of threshold temperature values, such as an upper temperature threshold value. The upper temperature threshold value may be greater than the lower temperature threshold value, to prevent the heating circuit from turning on and off too frequently. The battery monitoring module30may then reduce or eliminate the current flow to the discharge circuit and to the heating device.

As shown inFIG. 25, the battery unit20comprises a plurality of positive electrodes58, negative electrodes59and separators56that are stacked within the housing38to form a single cell31having a plurality of cell units33. A cell unit33consists of a positive electrode, a negative electrode and a separator therebetween. The cell shown has five positive electrodes and some of these electrodes act as the positive electrode for two cell units, wherein there is a separate and negative electrode on either side of the positive electrode. This single positive electrode for two opposing negative electrodes is a dual cell unit39. Likewise, some of the negative electrodes act as a negative electrode for positive electrodes configured on either side. The positive and negative electrodes may be planar sheets of material comprising a metal conductor, such as aluminum or copper. The metal conductor may act as heating device to conduct and transfer heat into the cell to heat the cell above a threshold temperature. A positive electrode connector55connects the positive electrodes58, to provide electrical current to each of the individual positive electrodes. The heating device75is coupled with the positive electrode75and heat is transferred into the battery housing38by the positive electrode. Heat may also be transferred by a positive electrode connector. Alternatively, the heating device may be coupled with the negative terminal, or negative electrode connector57to enable heat transfer into the housing by the negative electrode. The electrodes may heat the electrolyte77and heat may be distributed within the housing by the electrolyte. A heating device is thermally coupled with a terminal of the battery when it heats the terminal directly or through a terminal connector, whereby when the heating device is on, the terminal will increase in temperature. A heating device may conduct heat through a thermally conductive material that may be non-electrically conductive. For example, a thermally coupled heating device may employ a material such as silicone rubbers or epoxies comprising boron nitride or aluminum nitride. The material, such as an elastomer may be filled with boron nitride or aluminum nitride to produce a thermally conductive yet electrically non-conductive heating material. An enclosure may be configured around the heating device and the terminal or terminal conductor to heat the terminal through conduction or convection.

As shown inFIG. 26, a battery heating circuit700, which may be a battery discharge circuit72, produces a flow of current708for heating a terminal, positive terminal28or negative terminal29, and subsequently an associated electrode of the battery. When a temperature sensor36detects that the battery has dropped below a lower threshold temperature value, the controller704may activate the battery heating circuit. The heater may be coupled with a terminal connector as described herein. A terminal connector may extend between a terminal and the electrode and be electrically and thermally conductive. When the battery heating circuit is turned on, electrical current from a terminal of the battery will flow through resistor722and indicator716, such as a light emitting diode (LED)718, causing the LED to illuminate to indicate that the heater is activated. Concurrently, electrical current will flow through resistor724,726and transistor732. The voltage developed across resistor724and726will cause the transistor730to partially turn on, starving transistor732for base current. As the current through resistors724and726increases, transistor730will starve more current from the base of transistor732. An equilibrium between the two transistors730and732will be reached so that the current through732will be constant even though the battery cell voltage may change. Transistor732will be operating in a linear mode in the normal voltage operating range of the battery cell and will dissipate heat. By locating the heat dissipating transistor near a terminal of the battery cell, this heat will be transferred to from the terminal to an electrode that extends into the inner core of the battery cell to warm the battery internally. A software program in the controller, or a microprocessor of the controller, will determine when to turn the heater on and off. In particular, when the temperature sensor measures a temperature that is above an upper threshold limit, the controller will deactivate or turn-off the battery heating circuit by opening the transistors730and732. The control system may turn on the battery heating circuit when a temperature sensor measures a temperature of the battery that is below a lower threshold temperature value or limit and in some cases only when the state of charge of the battery is above a threshold value to prevent discharging the battery and further reducing the battery voltage. In addition, as the battery heating circuit may be turned-off by the controller if while activated, the voltage of the battery drops below a lower threshold value; again, to prevent further reduction of the battery voltage by a draw of current to the heater. In still another embodiment, the battery heater may have a time limit, wherein the battery heater is activated for a period of time and then shuts off. A battery heater circuit may have a user override, or a means to prevent the battery heater from being activated, such as a manual switch, or a selection that is input to the controller, such as through a user interface.