Abstract:
In one embodiment, the invention includes a power source having a plurality of battery groups and a processor coupled to the groups and adapted to electrically disconnect a group from the power source. Each group includes a plurality of cells, a sensor adapted to sense operating parameters of the cells, and a protection circuit coupled to the sensor. In another embodiment, the invention includes a method of managing a power source with a two-tier approach. On a group level, the method includes retrieving cell data representative of the operating parameters of the cells of the group and managing the connection state of the group based on the retrieved cell data. On a system level, the method includes, retrieving group data representative of the operating parameters of the groups and managing the connection state of the group based on the retrieved group data.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/978,684 filed 9 Oct. 1007; U.S. Provisional Application No. 60/978,685 filed 9 Oct. 2007; U.S. Provisional Application No. 61/040,091 filed 27 Mar. 2008; and U.S. Provisional Application No. 61/040,094 filed 27 Mar. 2008. All four provisional applications are incorporated in their entirety by this reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates generally to the power source field, and more specifically to an improved power source and method of managing a power source. 
       BACKGROUND 
       [0003]    High-density battery packs have the energy density required for transportation applications but may fail catastrophically, unexpectedly, and fatally if poorly managed. Current battery packs provide either acceptable energy density (lithium ion or lithium polymer) or safety features (nickel metal hydride, lead acid), but not both. Existing solutions to this problem use traditional methods of protection and isolation. For example, some automotive battery packs use an assortment of mechanical, thermal, and electrical techniques to isolate faulty cell groups (e.g. thermal fuses and heavy packaging or physical firewalls). These techniques are typically used, however, with large groups of cells, so a fault significantly depletes the available pack power. In order to achieve the necessary safety and driving range for battery packs in transportation applications, it is desired to provide the energy density of a lithium ion or lithium polymer battery pack with the safety of older battery chemistries. Thus, there is a need in the battery protection field to create an improved power source and method of managing a power source. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0004]      FIG. 1  is an abstract representation of a first preferred embodiment of the invention. 
           [0005]      FIG. 2  is a detailed schematic representation of the battery modules of  FIG. 1 . 
           [0006]      FIG. 3  is a detailed schematic representation of the battery protection circuit of  FIG. 2 . 
           [0007]      FIG. 4  is a detailed schematic representation of the pack-unit of  FIG. 1 . 
           [0008]      FIG. 5  is a detailed schematic representation of the integration level of  FIG. 1 . 
           [0009]      FIG. 6  is a detailed schematic representation of the integration level of  FIG. 1 , similar to  FIG. 5 , showing the isolation of a pack-unit by the activation of the electrical bridge bypass. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0010]    The following description of the preferred embodiments of the invention is not intended to limit the invention to these preferred embodiments, but rather to enable any person skilled in the art to make and use this invention. 
         [0011]    In the abstract, as shown in  FIG. 1 , the power source of the preferred embodiment includes a module level, a pack-unit level, and an integration level. On the module level, as shown in  FIG. 2 , the modules  100  of the preferred embodiment include a plurality of cells  102 , a sensor  110 , and a battery protection circuit  104 . On the pack-unit level, as shown in  FIG. 4 , the pack-unit  200  of the preferred embodiment for protecting battery packs includes a plurality of battery modules  100 , a processing unit  202 , and a data bus  212 . On the integration level, as shown in  FIG. 5 , the system  300  of the preferred embodiment includes a plurality of pack-units  200 , a central processing unit  302 , and a data bus  312 . The invention provides a system for scalable, fine grain protection of battery packs, which may provide additional safety, reliability, and maintenance features that increase the range and usable life of the battery pack. The multi-level management facilitates the intelligent application of methods for continuous optimization of the performance and safety of the cells  102 . Such packs are likely to be used in transportation applications, although they may also find use in other fields such as outdoor power equipment, uninterruptible power supplies, and auxiliary power units. 
       1. Module Level 
       [0012]    As shown in  FIGS. 2 and 3 , the battery modules  100  include at least one cell  102 , a sensor  110  to measure parameters of the cell (such as voltage, current, temperature, failure modes, physical location, air/gas pressure, or any other suitable parameter), and a battery protection circuit  104  to disconnect the battery module from the pack-unit. The battery module  100  preferably contains at least one battery protection circuit  104  for each cell  102 , but may alternatively contain one battery protection circuit  104  for a plurality of cells  102 . The battery module  100  may also preferably includes circuitry to control temperature regulation fluid flow through the module and circuitry to communicate with neighboring modules to obtain information on operating conditions of neighboring modules. Neighboring modules are defined as those modules that are in physical and/or electrical proximity to the current module. 
         [0013]    The cells  102  of the preferred embodiment function to store energy. Preferably, each cell  102  is a conventional battery designed for use in small-scale applications like mobile phones and laptop computers. In a first version, the cells  102  are a lithium ion cell of type number 18650, which have the following specification: Nominal Voltage is 3.6-3.7 V, Shape is cylindrical, Diameter is 18 mm, Length is 65 mm, and Capacity is 2400-2600 mAh. These cells, which are lightweight and have a high energy density, are generally used in laptop computers. In a second version, the cells  102  are a lithium ion cell of type number 26700 (which have the following specifications: Shape is cylindrical, and Diameter is 26 mm, Length is 70 mm). With minimal or no modifications, the cells may be of greater (or lower) capacity and/or of greater (or lower) voltage. The cells  102 , in fact, may be of any suitable composition, of any suitable shape, and of any suitable performance specification. The battery module  100  preferably contains 1-7 cells  102 . The cells  102  of the battery module  100  are preferably arranged in a parallel electrical structure, but may alternatively be any other electrical structure suitable to provide adequate voltage levels to the device. 
         [0014]    As shown in  FIG. 3 , the sensor  110  of the preferred embodiment functions to measure the operating conditions of the cells in the module. The operating conditions preferably include current, voltage, and temperature, but may additionally include pressure and another other suitable parameters. The sensor  110  preferably includes a current sensor, a temperature sensor, a voltage sensor, and a pressure sensor. The current sensor preferably measures current through Rsense  108  (using nodes A-B). Rsense  108  is preferably a resistance or impedance used to measure current. Rsense  108  may alternatively be a hall-effect sensor or any other sensor suitable to measure current. The voltage sensor preferably measures voltage across the cell  102  (using nodes B-D). The temperature sensor preferably measures the temperature of the cell  102  using node C. The pressure sensor preferably measures the air pressure of a confined space enclosing the cell  102  using node E. The current sensor, temperature sensor, voltage sensor, and pressure sensor may, however, be of any suitable device and method to measure their respective parameters. 
         [0015]    As shown in  FIG. 2 , the battery protection circuit  104  functions to disconnect individual cells  102  or a plurality of cells  102  if a fault condition is detected. A fault condition may be indicated if the parameter rises above a particular threshold (such as “over voltage”, “over current”, or “over temperature”), drops below a particular threshold (such as “under voltage” or “under temperature”), or changes more than a particular amount over a particular time period (such as “increased air pressured”). The battery protection circuit  104  may alternatively monitor for fault conditions in the cell  102  based on other suitable fault conditions for a cell  102  or a plurality of cells  102 , such as the internal characteristic resistance of a cell, which may change over time. This resistance and its change over time may indicate the remaining life of the cell  102 . One or more cells  102  are preferably electrically disconnected by controlling a bypass disable/enable switch  112  and a connection/disconnection switch  114  of the cell  102 . This allows individual cells  102  or a plurality of cells  102  to be switched out on a fault condition; these may also be switched back in if the fault condition does not persist, for example, if a hot cell  102  or plurality of cells  102  returns to operable temperatures when switched out, it may be switched back in at a lower temperature threshold. As the cells  102  are switched out entirely on an over-voltage condition, there is little additional power consumed. The battery protection circuit may, however, electrically disconnect one or more cells by other suitable methods, such as re-directing the current flow through a grounding connection. 
         [0016]    The battery protection circuits  104  are preferably conventional battery protection circuits. Preferably, the fault conditions in the battery protection circuits  104  have at least one threshold for cell operating conditions. The thresholds are preferably programmed into the module, but may alternatively be defined by hardware in the module. The programmed threshold may also be adjusted during the operation of the module. The thresholds may also exist in more than one layer. For example, a software threshold either at the pack-unit level or the integration level may be used concurrently with a hardware threshold in the module level. With multiple threshold, the software threshold may be a lower value such that the hardware threshold acts as a backup threshold. In other words, the hardware threshold functions to define the fault conditions when the software malfunctions or is not available. The programmed threshold, at the pack-unit level and/or integration level, is preferably adjustable during the operation of the module. The battery protection circuit  104  preferably communicates battery module parameters, such as voltage, current, temperature, and pressure, to at least one processing unit  202 , across a serial data bus  212 . Additionally, the battery protection circuit  104  preferably identifies and communicates its physical, thermal, and electrical proximity to other battery protection circuits  104 . This proximity identification preferably uses a number or set of numbers to indicate location within the larger battery pack and physical, thermal, and electrical proximity to neighboring cells and battery protection circuits  104 . This identification, which is preferably unique to each battery protection circuit  104 , preferably divides the pack into proximate zones. The battery protection circuit  104  also preferably receives physical, thermal, and electrical conditions from neighboring protection circuits  104  of neighboring modules. This information preferably facilitates the battery protection circuit  104  in determining safe to operate conditions based upon the performance of neighboring modules. 
         [0017]    As shown in  FIG. 3 , in the battery protection circuits  104  of the preferred embodiment, the output from node Z preferably controls the switches for cell connection/disconnection  114  and bypass disable/enable 112. Preferably, the switches for cell connection/disconnection  114  and bypass disable/enable 112 are programmable transistor based switches. A field effect transistor (FET) is preferably used for cell connection/disconnection  114  and is preferably controlled by the battery protection circuit  104 . Cell connection/disconnection  114  may alternatively be an insulated-gate bipolar transistor (IGBT), a mechanical contractor, or any other suitable switching device. The field effect transistor is employed in series with the battery terminals to switch the cell  102  in or out of the circuit: a bypass path  112  is provided to permit current flow when the cell is switched out. The battery protection circuit  104  preferably also includes circuitry to detect catastrophic failure of cells  102  and immediately disconnect to prevent spread of catastrophic failure to neighboring battery modules  100 . Catastrophic failure may be detected by sudden increases in pressure within the battery module  100 . In addition, the battery protection circuit  104  may communicate with an external temperature-regulating system, such as a fluidic network. The battery protection circuit  104  may include an output Y that controls switches for valves that allow temperature-regulating fluid through the module. The switch may be a two state on/off switch or a variable switch such as a potentiometer. 
       2. Pack-Unit Level 
       [0018]    As shown in  FIG. 4 , the pack-unit  200  of the preferred embodiment for protecting battery packs includes at least one battery module  100 , a processing unit  202 , a data bus  212 , and a load power delivery path  224 . Each battery module  100  preferably contains 10% or less of the overall cells in the battery pack-unit  200 . 
         [0019]    The battery modules  100  are preferably arranged in series within the battery pack-unit  200 . This provides a high voltage level to the device that is relatively minimally affected by the disconnection of battery modules  100  from the battery pack-unit  200 . However, the battery modules  100  may also be arranged in any other electrical arrangement suitable to powering the device. 
         [0020]    The processing unit  202  functions to store parameter data in memory, correlate parameters to failure, and manage module connection states. The processing unit  202  also preferably functions to manage temperature regulation of the modules within pack-unit  200 . The processing unit  202  preferably includes a processor and a memory unit, and communication circuitry to connect to an external interface  222  (via a suitable connection such as RS-232, USB, or IEEE-1394) as well as the internal data bus  212 . 
         [0021]    The data bus  212  functions to transmit parameter measurements from the battery modules  100  to the processing unit  202 , and preferably also functions to carry module connection management data from the processing unit  202  to the battery modules  100 . The data bus  212  is preferably a serial data bus connecting the battery modules  100  and the processing unit  202 . The data bus  212  preferably allows data and control signals to flow from the battery modules  100  to the processing unit  202  as well as from the processing unit  202  back to the battery modules  100 . The processing unit  202  preferably transmits commands over the data bus  212  to the battery modules  100 , switching the battery modules  100  in or out of the pack controlled by the processing unit  202 . Preferably, the signals from the processing unit  202  will take a higher priority than any internal control circuitry in the battery modules  100 , allowing the processing unit  202  to override the internal circuitry of the battery modules. 
         [0022]    The processing unit  202  also preferably evaluates real time operation data from a plurality of battery modules  100  and determines optimal pack-unit operation. For example, temperature readings from a certain location within the battery pack-unit  200  may be higher than those from another location. To compensate for this, the processing unit  202  may send control signals through data bus  212  to preferably minimize power draw from the high temperature region until temperature throughout battery pack-unit  200  normalizes. To maintain power output of the pack-unit  200  when the output of one or more of the battery modules  100  is limited, the power output from other normally operating battery modules  100  in the pack-unit  200  may be increased. Location of the battery module  100  within the pack-unit  200  may be used to determine the re-balancing of power output. Alternatively, the processing unit  202  may communicate with an external temperature regulating system through battery protection units  104  and send control signals through data bus  212  to change the state of the temperature regulation through the high temperature region. However, the processing unit  202  may also communicate directly with an external temperature regulating system to regulate temperature in a high temperature region. Additionally, the processing unit  202  preferably evaluates real time operation data with historical data from the battery modules  100 . This facilitates the prediction of abnormal battery module  100  behavior based upon historical performance data of each particular module and the location of the battery module  100  within battery pack-unit  200 . For example, operational temperatures from battery modules  100  located in a certain location of battery pack-unit  200  may be consistently higher than those in other locations. Processing unit  202  may detect this pattern and signal for maintenance. Additionally, the processing unit  202  may detect the tendency for certain battery modules  200  to operate under normal conditions at higher temperatures. In response to this pattern, the processing unit  202  may increase the pre-programmed temperature fault threshold for these particular battery modules  100 . This dynamic adjustment of the programmed thresholds allows the pack-unit  200  to adapt to manufacturing and operation variations in the battery cells  102 . The processing unit  202  may also detect operating conditions that are similar to those seen prior to catastrophic failure and may disconnect those battery modules  100  in danger of failure, preventing catastrophic failure from affecting the battery pack-unit  200 . Additionally, the processing unit  202  may detect battery modules  100  whose operating conditions do not improve with re-balancing of power output or any other failure prevention adjustments and may disconnect these battery modules  100  from the pack-unit  200  to prevent failure. The processing unit  202  may also be pre-programmed to expect certain patterns in the performance of a battery module  100 . The historical data stored in processing unit  202  is preferably available for diagnostics during maintenance of the battery pack-unit  200 . 
         [0023]    The processing unit  202  also preferably evaluates real time operation data from the neighbors of each battery module  100 . In the case of a non-operational battery module  100 , the processing unit  202  preferably evaluates the real time operation data from all neighboring battery modules  100  to determine whether the neighboring battery modules  100  exhibit failure characteristics. “Neighboring battery modules”  100  preferably means directly adjacent, but my additionally include battery modules within a particular distance, along a particular electrical connection, or any other suitable parameter. In the case of an operational battery module  100 , the processing unit  202  preferably evaluates the real time operation data from all neighboring battery modules  100  to determine whether the neighboring battery modules exhibit characteristics that may harm the current battery module  100 , for example, increased pressure and/or high temperature. Additionally, the processing unit  202  preferably evaluates real time operation data with historical data from the neighboring battery modules  100 . This facilitates the prediction of adverse effects between neighboring battery modules  100 . For example, the processing unit  202  may notice that certain trends in operation data (high rate of temperature increase, consistently low levels of power output, etc.) have a stronger effect on neighboring battery modules  100 . Examining historical operation data of neighboring battery modules  100  may also facilitate distinguishing battery modules  100  that may have better performance if grouped together. 
         [0024]    The processing unit  202  also preferably controls current and power output of the battery pack-unit  200  based upon operating conditions measured within the battery pack-unit  200  and the power requirements of the device powered by the power source. For example, if all battery modules  100  are in healthy condition, the processing unit  202  preferably allows maximum current and power output. However, if one, some, or all of the battery modules are under non-optimal operating conditions, the processing unit  202  preferably limits current and power output. 
         [0025]    In a preferred embodiment, the pack-unit  200  further includes an external interface  222 . The external interface  222  functions to communicate (through either a display and/or a data port) the cell performance data from the processing unit  202 . The external interface  222  is preferably connected to the processing unit  202  via IEEE 1394, but may be connected to the processing unit  202  via RS-232, IEEE 1284, Ethernet, Wireless, Bluetooth, USB, or any other suitable communication protocol. 
       3. Integration Level 
       [0026]    As shown in  FIG. 5 , the system  300  of the preferred embodiment includes a plurality of pack-units  200 , a central processing unit (“CPU”)  302 , a data bus  312 , a load power delivery path  324 , and electrical bridge bypasses  314 . 
         [0027]    The pack-units  200  in the system  300  of the preferred embodiment are preferably arranged in a combination parallel and series electrical structure. The pack-units  200  are preferably split into two in-series electrical structures, each preferably with the same number of pack-units  200 . These two series electrical structures are then arranged in parallel and an electrical bridge bypass  314  is included in between each neighboring parallel battery pack, as shown in  FIG. 5 , to allow for various electrical arrangements. Alternatively, the pack-units may be arranged in a “main pack” and “auxiliary pack” configuration such that only the “main pack” is in constant use by the device and the “auxiliary pack” is put into use when the “main pack” experiences an operation malfunction. However, the pack-units  200  may be arranged into any other electrical structure suitable to powering the device. As mentioned previously, each pack-unit  200  is preferably capable of communicating with the CPU  302  through data bus  312 . The pack-units  200  are preferably connected directly to the processing unit  200  where the state of connectivity may be controlled by the processing unit  200 . Alternatively, the pack-units  200  may also be directly electrically connected with each other and preferably function to control individual state of connectivity. 
         [0028]    The CPU  302  preferably functions to control current and power output from the system  300  based upon device power requirements and the state of the system  300 . The CPU  302  also preferably functions to communicate with pack-units  200  through data bus  312 . Data representative of the status of modules  100  within pack unit  200  are preferably communicated to the CPU  302 . Preferably, data representative of the voltage, current, temperature, and/or pressure of the modules  100  within pack-unit  200  are communicated to the CPU  302 . Alternatively, data representing the overall state of pack-unit  200  may be communicated to the CPU  302 . For example, data representing the number of modules  100  that are in operation in pack-unit  200 , the equivalent current and power output of pack-unit  200 , the overall temperature of pack-unit  200 , and/or the overall pressure of pack-unit  200 , may be communicated to the CPU  302 . The data communicated to the CPU  302  from each of the pack-units  200  are preferably compared to pre-programmed operable thresholds for each set of data to determine overall health of the pack-unit  200 . For example, one such threshold may indicate the maximum number of inoperable modules that can be within any one pack-unit at one time; another such threshold may indicate the maximum length of time for which a battery parameter such as voltage, current, or temperature may be at a certain level, indicating the inability of the pack-unit  200  to restore safe operating conditions for the cells  102  contained within, or yet another such threshold may indicate a maximum overall pressure within pack-unit  200 . Other indicators of pack-unit  200  or battery module  100  health may be changes in the frequency of occurrences in which a battery parameter such as voltage, current, or temperature may be at a certain level, indicating potential failure. The lack of improvement of operation conditions despite modulation of operational parameters of pack-unit  200  or battery module  100  may also indicate potential failure. These thresholds are preferably adjusted during the operation of the system to adapt to variations in the performance of a pack-unit  200 . 
         [0029]    The CPU  302  preferably sends signals to each pack-unit  200  through the data bus  312  to retrieve operation data and to analyze pack-unit  200  to determine whether to disconnect or reconnect pack-unit  200  from/to the system  300 , or to adjust power output of the pack-unit  200 . Alternatively, each pack-unit  200  in the system  300  may also be capable of detecting internal operating conditions and disconnecting and connecting itself to the system  300 . In the event the CPU  302  detects a pack-unit  200  that is operating at conditions that are deemed unhealthy by the CPU  302 , the CPU  302  preferably electrically isolates said pack-unit  200  from the system  300 . With the combination parallel and series electrical structure of the battery packs described above, in the event the CPU  302  determines a pack-unit  200  is inoperable, the pack-unit  200  may be isolated by the activation of the electrical bridge bypass  314  to reroute power in the system, as shown in  FIG. 6 . In this case, one pack-unit  200  in the system  300  will experience twice the load of other operating pack-units  200  in the system and the total current of the system  300  is preferably limited to minimize wear on the double-loaded pack-unit  200 . Alternatively, in the “main pack” and “auxiliary pack” battery pack integration structure variation described above, in the event an inoperable pack-unit  200  is detected, the CPU  302  may isolate all battery packs that may be in use and switch to the “auxiliary pack.” 
         [0030]    The data bus  312  of the preferred embodiment functions to transmit operation data from the pack-units  200  to the CPU  302 , and preferably also functions to carry pack-unit  200  connection management data from the CPU  302  to the pack-units  200 . The data bus  312  is preferably a serial data bus connecting the pack-units  200  and the CPU  302 . The data bus  312  preferably allows data and control signals to flow from the pack-units  200  to the CPU  302  as well as from the CPU  302  back to the pack-units  200 . The pack-units  200  preferably transmit data over representing the connection state of each individual pack-unit  200  over data bus  312 . Alternatively, the CPU  302  may also transmit commands over the data bus  312  to the pack-units  200  to switch the pack-units  200  in or out of the system  300 . Preferably, the signals from the CPU  302  will take a higher priority than any internal control circuitry in the pack-units  200  or the battery modules  100 , allowing the CPU  302  to override the internal circuitry of the pack-units  200  or the battery modules  100 . 
         [0031]    As a person skilled in the art will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiments of the invention without departing from the scope of this invention defined in the following claims.