Embodiments disclosed herein relate to a battery energy storage system (BESS) that can be used to store energy that is produced by conventional sources (e.g., coal, gas, nuclear) as well as renewable sources (e.g., wind, solar), and provide the stored energy on-demand.
Electrical energy is vital to modern national economies. Increasing electrical energy demand and a trend towards increasing the use of renewable energy assets to generate electricity, however, are creating pressures on aging electrical infrastructures that have made them more vulnerable to failure, particularly during peak demand periods. In some regions, the increase in demand is such that periods of peak demand are dangerously close to exceeding the maximum supply levels that the electrical power industry can generate and transmit. New energy storage systems, methods, and apparatuses that allow electricity to be generated and used in a more cost effective and reliable manner are described herein.
The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the disclosure and to enable a person skilled in the relevant art to make and use the disclosure.
In the drawings, like reference numbers may indicate identical or functionally similar elements.
While the present disclosure is described herein with illustrative embodiments for particular applications, it should be understood that the disclosure is not limited thereto. A person skilled in the art with access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the disclosure would be of significant utility.
The terms “embodiments” or “example embodiments” do not require that all embodiments include the discussed feature, advantage, or mode of operation. Alternate embodiments may be devised without departing from the scope or spirit of the disclosure, and well-known elements may not be described in detail or may be omitted so as not to obscure the relevant details. In addition, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. For example, as used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or groups thereof.
Conventional sources of electrical energy, such as power plants that burn fossil fuels, have an adverse effect on the environment. These adverse effects have led to the development of “clean” or “alternative” energy production using renewable energy sources, such as solar and wind. These alternative energy sources are being integrated into the power grid along with the conventional energy sources, and account for an increasing percentage of the overall amount of energy produced and consumed. However, they have yet to fully replace the conventional sources. Indeed, conventional sources still account for a majority of the energy produced on the power grid.
One reason that conventional energy sources remain a primary source of electrical energy is their ability to handle fluctuations in demand. Power plants that burn fossil fuels and other conventional sources (e.g., nuclear) typically use large generators to produce energy. To account for fluctuations in demand, these generators are typically operated below their full capacity. Thus, when demand temporarily increases or “spikes,” the generators can be ramped-up to produce more energy and meet the increased demand. The excess capacity of a generator is often referred to as its “spinning reserve.”
By contrast, alternative energy sources lack spinning reserve. That is, the source (e.g., the sun or wind) produces at its maximum level and cannot be ramped-up as desired to meet increased demand. Moreover, the amount of energy produced by these alternative sources is not as predictable as by conventional sources—the alternative sources are at the mercy of the environment. An overcast or calm day (i.e., not windy) will not produce as much energy as a sunny or windy day. Likewise, if the sun goes behind a cloud or the wind stops blowing while demand remains constant or increases, the alternative source may not be able to produce enough energy to meet the demand.
It is necessary for the power grid to provide a stable (e.g., frequency stability) and reliable source of electrical energy. When alternative energy sources are integrated into the power grid along with the conventional energy sources, the “clean” energy produced by the alternative energy sources can replace a certain amount of the energy that is produced by the conventional sources, reducing the amount of energy produced by burning fossil fuels or other controversial methods (e.g., nuclear). At the same time, the conventional energy sources can be ramped-up or down to meet demand and provide a stable frequency.
However, in addition to the initial investment, there are operation expenses associated with running generators that are used to produce energy at conventional power plants.
Embodiments of the battery energy storage system (BESS) described throughout this disclosure may alleviate many of the problems associated with integrating alternative (renewable) energy sources into the power grid.
BESS 340 can provide energy to power grid 320 when the output of alternative energy source 330 falls below a threshold or when alternative energy source 330 cannot produce enough energy to meet demand (e.g., BESS 340 can function as the “spinning reserve” for alternative energy source 330). For example, instead of starting a shutdown generator at conventional energy source 310 to meet a spike in demand or lack of production by alternative energy source 330, BESS 340 may discharge energy from its battery packs to provide the needed energy. As a few non-limiting examples, BESS 340 may provide 3 MW for 15 minutes, 2 MW for 30 minutes, or 1.5 MW for 45 minutes. BESS 340 may be configured to provide more or less energy for different lengths of time.
BESS 340 can also be used to assist in frequency stabilization of power grid 320. For example, BESS 340 may include electronics that monitor the line frequency of power grid 320 and deliver energy to or draw energy from power grid 320 to maintain a stable frequency (e.g., 60 Hz). As shown in
As shown in
In an embodiment (described in more detail below), each battery pack includes battery cells (which may be arranged into battery modules), a battery pack controller that monitors the battery cells, a balancing charger (e.g., DC power supply) that adds energy to each of the battery cells, and a distributed, daisy-chained network of battery module controllers that may take certain measurements of and remove energy from the battery cells. The battery pack controller may control the network of battery module controllers and the balancing charger to control the state-of-charge or voltage of a battery pack. In this embodiment, the battery packs that are included in BESS 400 are considered “smart” battery packs that are able to receive a target voltage or state-of-charge value and self-balance to the target level.
On the other hand, the utility embodiment 430 of
Field monitoring device 524 may also be coupled to EMS 526 via communication network 522. Field monitoring device 524 may be coupled to an alternative energy source (e.g., a solar plant, a wind plant, etc.) to measure the energy generated by the alternative energy source. Likewise, monitoring device 518 may be coupled to BESS 502 and measure the energy generated by BESS 502. While two monitoring devices are illustrated in
BESS 502 includes a hierarchy of control levels for controlling BESS 502. The control levels of BESS 502, starting with the top level are system controller, array controller, string controller, battery pack controller, and battery module controller. For example, system controller 512 may be coupled to one or more array controllers (e.g., array controller 508), each of which may be coupled to one or more string controllers (e.g., string controller 504), each of which may be coupled to one or more battery pack controllers, each of which may be coupled to one or more battery module controllers. Battery pack controllers and battery modules controllers are disposed with battery packs 506(a)-506(n), and will be discussed in more detail with respect to
As shown in
System controller 512 can monitor and report the operation of BESS 502 to EMS 526 or any other device connected to communication network 522 and configured to communicate with BESS 502. System controller 512 can also receive and process instructions from EMS 526, and relay instructions to an appropriate array controller (e.g., array controller 506) for execution. System controller 512 may also communicate with PCS 520 to control the charging and discharging of BESS 502.
Although system controller 512 is shown disposed within BESS 502 in
In other embodiments, such as utility embodiment 430, only one of BESS units 431-436 may include a system controller. For example, in
Considering
Each string controller in BESS 502 is coupled to one or more battery packs. For example, string controller 504 is coupled to battery packs 506(a)-(n), which are connected in series to form a battery pack string. Any number of battery packs may be connected together to form a battery pack string. Strings of battery packs can be connected in parallel in BESS 502. Two or more battery pack strings connected in parallel may be referred to as an array of battery packs or a battery pack array. In one embodiment, BESS 502 includes an array of battery packs having six battery pack strings connected in parallel, where each of the battery pack strings has 22 battery packs connected in series.
As its name suggests, a string controller may monitor and control the battery packs in the battery pack string. The functions performed by a string controller may include, but are not limited to, the following: issuing battery string contactor control commands, measuring battery string voltage; measuring battery string current; calculating battery string Amp-hour count; relaying queries between a system controller (e.g., at charging station) and battery pack controllers; processing query response messages; aggregating battery string data; performing software device ID assignment to the battery packs; detecting ground fault current in the battery string; and detect alarm and warning conditions and taking appropriate corrective actions. Example embodiments of a string controller are described below with respect to
Likewise, an array controller may monitor and control a battery pack array. The functions performed by an array controller may include, but are not limited to, the following: sending status queries to battery pack strings, receiving and processing query responses from battery pack strings, performing battery pack string contactor control, broadcasting battery pack array data to the system controller, processing alarm messages to determine necessary actions, responding to manual commands or queries from a command line interface (e.g., at an EMS), allowing a technician to set or change the configuration settings using the command line interface, running test scripts composed of the same commands and queries understood by the command line interpreter, and broadcasting data generated by test scripts to a data server for collection.
In String 1, each of the 22 battery packs is labeled (“BP1” through “BP22”), illustrating the order in which the battery packs are connected in series. That is, BP1 is connected to the positive terminal of a string controller (SC1) and to BP2, BP2 is connected to BP1 and BP3, BP3 is connected to BP2 and BP4, and so on. As shown, BP22 is connected to the negative terminal of SC1. In the illustrated arrangement, SC1 may access the middle of string 1 (i.e., BP11 and BP12). In an embodiment, this middle point is grounded and includes a ground fault detection device.
BESS 502 includes one or more lighting units 530 and one or more fans 532, which may be disposed at regular intervals in ceiling panels of BESS 502. Lighting units 530 can provide illumination to the interior of BESS 502. Fans 532 are oriented so that they blow down from the ceiling panels toward the floor of BESS 502 (i.e., they blow into the interior of BESS 502). BESS 502 also includes a split A/C unit including air handler 534 housed within the housing of BESS 502 and condenser 536 housed outside the housing of BESS 502. The A/C unit and fans 532 may be controlled (e.g., by array controller 508) to create an air flow system and regulate the temperature of the battery packs housed within BESS 502.
Example Battery Pack
The housing of battery pack 600 may be assembled using fasteners 628 shown in
In
The front panel 602 of battery pack 600 may also include a status light and reset button 608. In one embodiment, status button 608 is a push button that can be depressed to reset or restart battery pack 600. In one embodiment, the outer ring around the center of button 608 may be illuminated to indicate the operating status of battery pack 600. The illumination may be generated by a light source, such as one or more light emitting diodes, that is coupled to or part of the status button 608. In this embodiment, different color illumination may indicate different operating states of the battery pack. For example, constant or steady green light may indicate that battery pack 600 is in a normal operating state; flashing or strobing green light may indicate that battery pack 600 is in a normal operating state and that battery pack 600 is currently balancing the batteries; constant or steady yellow light may indicate a warning or that battery pack 600 is in an error state; flashing or strobing yellow light may indicate a warning or that battery pack 600 is in an error state and that battery pack 600 is currently balancing the batteries; constant or steady red light may indicate that the battery pack 600 is in an alarm state; flashing or strobing red light may indicate that battery pack 600 needs to be replaced; and no light emitted from the status light may indicate that battery pack 600 has no power and/or needs to be replaced. In some embodiments, when the status light emits red light (steady or flashing) or no light, connectors in battery pack 600 or in an external controller are automatically opened to prevent charging or discharging of the batteries. As would be apparent to one of ordinary skill in the art, any color, strobing technique, etc., of illumination to indicate the operating status of battery pack 600 is within the scope of this disclosure.
Turning to
As shown, battery pack 600 includes a plurality of battery modules and a BMC (e.g., battery module controller 638) is coupled to each battery module (e.g., battery module 636). In one embodiment, which is described in more detail below, n BMCs (where n is greater than or equal to 2) can be daisy-chained together and coupled to a BPC to form a single-wire communication network. In this example arrangement, each BMC may have a unique address and the BPC may communicate with each of the BMCs by addressing one or more messages to the unique address of any desired BMC. The one or more messages (which include the unique address of the BMC) may include an instruction, for example, to remove energy from a battery module, to stop removing energy from a battery module, to measure and report the temperature of the battery module, and to measure and report the voltage of the battery module. In one embodiment, BPC 634 may obtain measurements (e.g., temperature, voltage) from each of the BMCs using a polling technique. BPC 634 may calculate or receive (e.g., from a controller outside of battery pack 600) a target voltage for battery pack 600, and may use the balancing charger 632 and the network of BMCs to adjust each of the battery modules to the target voltage. Thus, battery pack 600 may be considered a smart battery pack, able to self-adjust its battery cells to a target voltage.
The electrical wiring that connects various components of battery pack 600 has been omitted from
Battery module 636 includes a plurality of battery cells. Any number of battery cells may be included in battery module 636. Example battery cells include, but are not limited to, Li ion battery cells, such as 18650 or 26650 battery cells. The battery cells may be cylindrical battery cells, prismatic battery cells, or pouch battery cells, to name a few examples. The battery cells or battery modules may be, for example, up to 100 AH battery cells or battery modules. In some embodiments, the battery cells are connected in series/parallel configuration. Example battery cell configurations include, but are not limited to, 1P16S configuration, 2P16S configuration, 3P16S configuration, 4P16S configuration, 1P12S configuration, 2P12S configuration, 3P12S configuration, and 4P12S configuration. Other configurations known to one of ordinary skill in the art are within the scope of this disclosure. Battery module 636 includes positive and negative terminals for adding energy to and removing energy from the plurality of battery cells included therein.
As shown in
In
Each BMC in the communication network 700 may have a unique address that BPC 710 uses to communicate with individual BMCs. For example, BMC 720 may have an address of 0002, BMC 730 may have an address of 0003, BMC 740 may have an address of 0004, BMC 750 may have an address of 0005, and BMC 760 may have an address of 0006. BPC 710 may communicate with each of the BMCs by addressing one or more messages to the unique address of any desired BMC. The one or more messages (which include the unique address of the BMC) may include an instruction, for example, to remove energy from a battery module, to stop removing energy from a battery module, to measure and report the temperature of the battery module, and to measure and report the voltage of the battery module. BPC 710 may poll the BMCs to obtain measurements related to the battery modules of the battery pack, such as voltage and temperature measurements. Any polling technique known to one of skill in the art may be used. In some embodiments, BPC 710 continuously polls the BMCs for measurements in order to continuously monitor the voltage and temperature of the battery modules in the battery pack.
For example, BPC 710 may seek to communicate with BMC 740, e.g., in order to obtain temperature and voltage measurements of the battery module that BMC 740 is mounted on. In this example, BPC 710 generates and sends a message (or instruction) addressed to BMC 740 (e.g., address 0004). The other BMCs in the communication network 700 may decode the address of the message sent by BPC 710, but only the BMC (in this example, BMC 740) having the unique address of the message may respond. In this example, BMC 740 receives the message from BPC 710 (e.g., the message traverses communication wires 715, 725, and 735 to reach BMC 740), and generates and sends a response to BPC 710 via the single-wire communication network (e.g., the response traverses communication wires 735, 725, and 715 to reach BPC 710). BPC 710 may receive the response and instruct BMC 740 to perform a function (e.g., remove energy from the battery module it is mounted on). In other embodiments, other types of communication networks (other than communication network 700) may be used, such as, for example, an RS232 or RS485 communication network.
The method 7000 of
As the description of
Upon starting (stage 7010), the method 7000 proceeds to stage 7020 where the battery module controller receives a message. For example, a battery pack controller may communicate with the network of daisy-chained battery module controllers (e.g.,
As discussed with respect to
In stage 7040, the battery module controller decodes the instruction that is included in the message and the method 7000 advances to stage 7050. In stage 7050, the battery module controller performs the instruction. Again, the instruction may be (but is not limited to) measure and report the temperature of the battery module, measure and report the voltage of the battery module, remove energy from the battery module (e.g., apply one or more shunt resistors across the terminals of the battery module), stop removing energy from the battery module (e.g., stop applying the one or more shunt resistors across the terminals of the battery module), or calibrate voltage measurements before measuring the voltage of the battery module. In various embodiments, temperature and voltage measurements may be sent as actual temperature and voltage values, or as encoded data that may be decoded after reporting the measurement. After stage 7050, the method 7000 loops back to stage 7020 and the battery module controller waits for a new message.
As shown in
In one embodiment, battery pack controller 800 may be powered from energy stored in the battery cells. Battery pack controller 800 may be connected to the battery cells by DC input 802. In other embodiments, battery pack controller 800 may be powered from an AC to DC power supply connected to DC input 802. In these embodiments, a DC-DC power supply may then convert the input DC power to one or more power levels appropriate for operating the various electrical components of battery pack controller 800.
In the example embodiment illustrated in
Battery pack controller 800 may also include several interfaces and/or connectors for communicating. These interfaces and/or connectors may be coupled to MCU 812 as shown in
Battery pack controller 800 also includes an external EEPROM 816. External EEPROM 816 may store values, measurements, etc., for the battery pack. These values, measurements, etc., may persist when power of the battery pack is turned off (i.e., will not be lost due to loss of power). External EEPROM 816 may also store executable code or instructions, such as executable code or instructions to operate microprocessor unit 812.
Microprocessor unit (MCU) 812 is coupled to memory 814. MCU 812 is used to execute an application program that manages the battery pack. As described herein, in an embodiment the application program may perform the following functions (but is not limited thereto): monitor the voltage and temperature of the battery cells of battery pack 600, balance the battery cells of battery pack 600, monitor and control (if needed) the temperature of battery pack 600, handle communications between the battery pack and other components of a battery energy storage system, and generate warnings and/or alarms, as well as take other appropriate actions, to protect the battery cells of battery pack 600.
As described above, a battery pack controller may obtain temperature and voltage measurements from battery module controllers. The temperature readings may be used to ensure that the battery cells are operated within their specified temperature limits and to adjust temperature related values calculated and/or used by the application program executing on MCU 812. Similarly, the voltage readings are used, for example, to ensure that the battery cells are operated within their specified voltage limits.
Watchdog timer 822 is used to monitor and ensure the proper operation of battery pack controller 800. In the event that an unrecoverable error or unintended infinite software loop should occur during operation of battery pack controller 800, watchdog timer 822 can reset battery pack controller 800 so that it resumes operating normally. Status light and reset button 820 may be used to manually reset operation of battery pack controller 800. As shown in
In
Battery module controller 900 may communicate with other components of a battery pack (e.g., a battery pack controller, such as battery pack controller 634 of
Battery module controller 900 may be electrically isolated from other components that are coupled to the communication wire (e.g., battery pack controller, other battery module controllers, computing systems external to the battery pack) via isolation circuit 945. In the embodiment illustrated in
As explained above, battery module controller 900 may measure the voltage of the battery module it is mounted on. As shown in
Battery module controller 900 may also remove energy from the battery module that it is mounted on. As shown in
Fail safe circuit 925 may prevent shunt switch 930 from removing too much energy from the battery module. In the event that processor 905 malfunctions, fail safe circuit 925 may instruct shunt switch 930 to stop applying shunt resistor 935 across the positive and negative terminals of the battery module. For example, processor 905 may instruct shunt switch 930 at regular intervals (e.g., once every 30 seconds) to apply shunt resistor 935 in order to continuously discharge the battery module. Fail safe circuit 925, which is disposed between processor 905 and shunt switch 930, may monitor the instructions processor 905 sends to shunt switch 930. In the event that processor 905 fails to send a scheduled instruction to the shunt switch 930 (which may be caused by a malfunction of processor 905), fails safe circuit 925 may instruct or cause shunt switch 930 to open, preventing further discharge of the battery module. Processor 905 may instruct fail safe circuit 925 to prevent shunt switch 930 from discharging the battery module below a threshold voltage or state-of-charge level, which may be stored or calculated in battery module controller 900 or in an external controller (e.g., a battery pack controller).
Battery module controller 900 of
Considering
Example String Controller
The functions performed by string controller 1100 may include, but are not limited to, the following: issuing battery string contactor control commands, measuring battery string voltage; measuring battery string current; calculating battery string Amp-hour count; relaying queries between a system controller (e.g., at charging station) and battery pack controllers; processing query response messages; aggregating battery string data; performing software device ID assignment to the battery packs; detecting ground fault current in the battery string; and detect alarm and warning conditions and taking appropriate corrective actions. MCU 1125 may perform these functions by executing code that is stored in memory 1127.
String controller 1100 includes battery string terminals 1102 and 1104 for coupling to the positive and negative terminals, respectively, of a battery string (also referred to as a string of battery packs). Battery string terminals 1102 and 1104 are coupled to voltage sense unit 1142 on string control board 1124 that can be used to measure battery string voltage.
String controller 1100 also includes PCS terminals 1106 and 1108 for coupling to the positive and negative terminals, respectively of a power control system (PCS). As shown, positive battery string terminal 1102 is coupled to positive PCS terminal 1106 via contactor 1116, and negative battery string terminal 1104 is coupled to negative PCS terminal 1108 via contactor 1118. String control board 1124 controls contactors 1116 and 1118 (to open and close) via contactor control unit 1126 and 1130, respectively, allowing the battery string to provide energy to the PCS (discharging) or receive energy from the PCS (charging) when contractors 1116 and 1118 are closed. Fuses 1112 and 1114 protect the battery string from excessive current flow.
String controller 1100 also includes communication terminals 1110 and 1112 for coupling to other devices. In an embodiment, communication terminal 1110 may couple string controller 1100 to the battery pack controllers of the battery string, allowing string controller 1100 to issue queries, instructions, and the like. For example, string controller 1100 may issue an instruction used by the battery packs for cell balancing. In an embodiment, communication terminal 1112 may couple string controller 1100 to an array controller, such as array controller 508 of
String controller 1100 includes power supply unit 1122. Power supply 1220 of
String control board 1124 includes current sense unit 1128 which receives input from current sensor 1120, which may allow the string controller to measure battery string current, calculate battery string amp-hour count, as well as other functions. Additionally, current sense unit 1128 may provide an input for overcurrent protection. For example, if over-current (a current level higher than a pre-determined threshold) is sensed in current sensor 1120, current sensor unit 1128 may provide a value to MCU 1125, which instructs contactor control units 1126 and 1130 to open contactors 1116 and 1118, respectively, disconnecting battery string from PCS. Again, fuses 1112 and 1114 may also provide overcurrent protection, disconnecting battery sting from the PCS when a threshold current is exceeded.
String controller 1100 includes battery voltage and ground fault detection (for example, battery voltage and ground fault detection 1210 of
Example Battery Pack Balancing Algorithm
As the description of
Upon starting, the method 1300 proceeds to stage 1310 where a target voltage value is received by a battery pack controller, such as battery pack controller 634. The target value may be used to balance the voltage and/or state of charge of each battery module (e.g., battery module 636) in the battery pack and may be received from an external controller, such as a string controller described with respect to
In stage 1320, a determination is made as to whether each polled battery module voltage is in an acceptable range. This acceptable range may be determined by one or more threshold voltage values above and/or below the received target voltage. For example, battery pack controller 634 may use a start discharge value, a stop discharge value, a start charge value, and a stop charge value that are used to determine whether balancing of battery modules should be performed. In an embodiment, the start discharge value may be greater than the stop discharge value (both of which may be greater than the target value), and the start charge value may be less than the stop charge value (both of which may be less than the target value). These threshold values may be derived by adding stored offset values to the received target voltage value. In an embodiment, the acceptable range may lie between the start discharge value and the start charge value, indicating a range in which no balancing may be necessary. If all battery module voltages are within the acceptable range, method 1300 proceeds to stage 1325. In stage 1325, a balancing charger (e.g., balancing charger 632) is turned off (if on) and shunt resistors of each battery module controller 638 that have been applied, such as shunt resistors 935 of
Returning to stage 1320, if all battery module voltages are not within the acceptable range, the method proceeds to stage 1330. In stage 1330, for each battery module, it is determined whether the battery module voltage is above the start discharge value. If the voltage is above the start discharge value, method 1300 proceeds to stage 1335 where shunt resistors of the battery module controller (e.g., battery module controller 638) coupled to the battery module are applied in order to remove (discharge) energy from the battery module. The method then continues to stage 1340.
In stage 1340, for each battery module, it is determined whether the battery module voltage is below the stop discharge value. If the voltage is below the stop discharge value, method 1300 proceeds to stage 1345 where shunt resistors of the battery module controller (e.g., battery module controller 638) coupled to the battery module are opened in order to stop discharging energy from the battery module. That is, the battery module controller stops applying the shunt resistor(s) across the terminals of the battery module it is mounted on. This prevents the battery module controller from removing energy from the battery module. The method then continues to stage 1350.
In stage 1350, it is determined whether at least one battery module voltage is below the start charge value. If any voltage is below the start charge value, method 1300 proceeds to stage 1355 where a balancing charger is turned on to provide energy to all of the battery modules. For example, battery pack controller 634 may instruct balancing charger 632 to turn on, providing energy to each of the battery modules in the battery pack 600. Method 1300 then continues to stage 1360.
In stage 1360, it is determined whether all battery module voltages are above the stop charge value. If all voltages are above the stop charge value, method 1300 proceeds to stage 1365 where a balancing charger is turned off (if previously on) to stop charging the battery modules of the battery pack. For example, battery pack controller 634 may instruct balancing charger 632 to stop providing energy to the battery modules of battery pack 600. Method 1300 then returns to stage 1315 where the battery modules are again polled for voltage measurements. Thus, as previously described, stages 1315 to 1360 of method 1300 may be used to continuously balance the energy of the battery modules within a battery pack, such as battery pack 600.
Example BESS Housing
Example Warranty Tracker for a Battery Pack
In an embodiment, a warranty based on battery usage for a battery pack, such as battery pack 600 of
Charge and discharge rates of a battery pack are related to and can be approximated or determined based on the amount of electric current flowing into and out of the battery pack, which can be measured. In general, higher charge and discharge rates may produce more heat (than lower rates), which may cause stress on the battery pack, shorten the life of the battery pack, and/or lead to unexpected failures or other issues.
Normal charge and discharge rates for batteries of different capacities may vary. For this reason, in an embodiment, electric current measurements may be normalized in order to apply a standard for determining normal charge and discharge rates for different battery packs. One of skill in the art will recognize that the measured electric current may be normalized based on the capacity of the battery pack, producing a C-rate. As an example, a normalized rate of discharge of 1 C would deliver the battery pack's rated capacity in one hour, e.g., a 1,000 mAh battery would provide a discharge current of 1,000 mA for one hour. The C-rate may allow the same standard to be applied for determining normal charge and discharge, whether the battery pack is rated at 1,000 mAh or 100 Ah or any other rating known to one of ordinary skill in the art.
Still considering
In an embodiment, calculated C-rates above a maximum C-rate warranty threshold 1708 may immediately void the warranty of the battery pack. This threshold may be predefined or set dynamically by the warranty tracker. In a non-limiting example, maximum warranty threshold 1708 may be set to a C-rate of 2 C. Calculated C-rates above maximum warranty threshold 1708 may indicate improper usage of the battery pack, and hence the warranty may not cover subsequent issues that arise. In an embodiment, maximum warranty thresholds may be defined for both the rate of charge and discharge of the battery pack, rather than maintaining a single threshold for both charge and discharge.
Temperature is another factor that may affect battery performance. In general, higher temperatures may cause the battery pack to age at a faster rate by generating higher internal temperatures, which causes increased stress on the battery pack. This may shorten the life of a battery pack. On the other hand, lower temperatures may, for example, cause damage when the battery pack is charged.
Warranty thresholds may also be a function of battery temperature such as, for example, charging the battery pack when the temperature is below a predefined value. In an embodiment, operating temperatures below a minimum temperature warranty threshold 1808 or above a maximum temperature warranty threshold 1810 may immediately void the warranty of the battery pack. These thresholds may be predefined or set dynamically by the warranty tracker. Operating temperatures below minimum warranty threshold 1808 or above maximum warranty threshold 1810 may indicate improper usage of the battery pack, and hence the warranty may not cover subsequent operating issues or defects that arise. In an embodiment, minimum and maximum warranty thresholds may be defined for both charging and discharging the battery pack rather than maintaining the same thresholds for both charging and discharging.
Voltage and/or state-of-charge are additional factors that may affect battery performance. The voltage of a battery pack, which may be measured, may be used to calculate or otherwise determine the state-of-charge of the battery pack. In general, very high or very low states of charge or voltages cause increased stress on the battery pack. This, again, may shorten the life of the battery pack.
In
In an embodiment, measured voltages below a minimum voltage warranty threshold 1908 or above a maximum voltage warranty threshold 1910 may immediately void the warranty of the battery pack. These thresholds may be predefined or set dynamically by the warranty tracker. In a non-limiting example, minimum and maximum warranty thresholds 1908 and 1910 may be set to voltages indicating the over-discharging and over-charging of the battery cells, respectively. Measured voltages below minimum warranty threshold 1908 or above maximum warranty threshold 1910 may indicate improper usage of the battery pack, and hence the warranty may not cover subsequent issues that arise.
In various embodiments, a battery pack may store the minimum recorded voltage 2001, maximum recorded voltage 2002, minimum recorded temperature 2003, maximum recorded temperature 2004, maximum recorded charging electric current 2005, and maximum recorded discharging electric current 2006 for the life of the battery pack. These values may be recorded by any device or combination of devices capable of measuring or calculating the aforementioned data, such as (but not limited to) one or more battery voltage measurement circuit(s), battery temperature measurement circuit(s), and electric current measurement circuit(s), respectively, which are further described with respect to
In an embodiment, each battery pack may maintain a list of warranty threshold values, for example warranty threshold values 2011-2016, in a computer-readable storage device. In another embodiment, the list of warranty threshold values may be maintained in a computer-readable storage device that is external to the battery pack. Warranty threshold values may indicate minimum and maximum limits used to determine uses of the battery pack that are outside the warranty coverage. The warranty tracker may periodically compare the stored minimum and maximum values 2001-2006 to warranty threshold values 2011-2016 to determine whether a warranty for the battery pack should be voided.
In an embodiment, the battery pack may store a warranty status in a computer-readable storage device. The warranty status may be any type of data capable of representing a status. For example, the warranty status may be a binary flag that indicates whether the warranty has been voided. The warranty status may also be, for example, an enumerated type having a set of possible values, such as but not limited to, active, expired, and void.
As illustrated in
In an embodiment, one or more ranges of values may be defined for each type of recorded data. In the example illustrated in
In an embodiment, voltage measurements may be taken periodically. When a measured value falls within a defined range, the associated counter may be incremented. The value of each counter then represents the frequency of measurements falling within the associated range of values. Frequency statistics may then be used to create a histogram displaying the distribution of usage measurements for the life of a battery pack, or during a period of time. Likewise, frequency statistics may be recorded for other measured or calculated data, such as but not limited to, battery temperature measurements and charge/discharge current measurements.
For example, battery usage 2102 represents the distribution of voltage measurements taken during the life of a battery pack. Battery usage 2102 may indicate ordinary or proper usage of a battery pack, having the highest frequency of measurements between 3.0 V and 3.2 V. In contrast, battery usage 2104 may indicate more unfavorable usage.
Histograms, such as those displayed in
In various embodiments, voltage may be measured as an aggregate voltage or average voltage of the battery cells or battery modules contained within the battery pack. Battery temperature measurement circuit 2218 may include one or more temperature sensors to periodically measure battery cell temperatures or battery module temperatures within the battery pack and send an aggregate or average temperature measurement to processor 2212.
In an embodiment, processor 2212 also receives periodic electric current measurements from battery current measurement circuit 2222. Battery current measurement circuit 2222 may be external to warranty tracker 2210. For example, battery current measurement circuit 2222 may reside within string controller 2220 (e.g., string controller 1100 of
Processor 2212 may compute warranty values based on received voltage, temperature, and electric current measurements. In an embodiment, each warranty value represents battery usage at the time the received measurements were recorded. Once received, measurements may be converted to associated factors for use in calculating a warranty value. For example, a voltage measurement received from battery voltage measurement circuit 2216 may be converted to a corresponding voltage factor as described with respect to
In an embodiment, processor 2212 may calculate a warranty value by multiplying the voltage factor, temperature factor, and current factor together. For example, the current factor may be 0 when a battery pack is neither charging nor discharging. The calculated warranty value will therefore also be 0, indicating that no usage is occurring. In another example, when battery temperature and voltage are at optimal levels, the corresponding temperature and voltage factors may be 1. The calculated warranty value will then be equal to the current factor corresponding to the measured electric current. When all factors are greater than zero, the warranty value indicates battery usage based on each of the voltage, temperature, and electric current measurements.
As described previously, additional measured or calculated data may also be used in the calculation of a warranty value. A warranty value may also be calculated based on any combination voltage, temperature, and current factors, according to an embodiment.
While a warranty value represents battery usage at a point in time, a warranty for a battery pack is based on battery usage for the life of the battery pack (which may be defined by the manufacturer of the battery pack). In an embodiment, memory 2214 stores a cumulative warranty value that represents battery usage over the life of the battery pack. Each time a warranty value is calculated, processor 2212 may add the warranty value to the cumulative warranty value stored in memory 2214. The cumulative warranty value may then be used to determine whether the battery pack warranty is active or expired.
Method 2300 begins at stage 2304 by measuring battery cell voltages within a battery pack. In an embodiment, battery cell voltage measurements for different battery cells or battery modules may be aggregated or averaged across a battery pack. At stage 2306, battery cell temperatures may be measured. In an embodiment, battery cell temperature measurements for different battery cells or battery modules may be aggregated or averaged across a battery pack. At stage 2308, an electric charge/discharge current measurement may be received. Stages 2304, 2306, and 2308 may be performed concurrently or in any order.
At stage 2310, a warranty value is calculated using the measured battery voltage, measured battery temperature, and received electric current measurement. In an embodiment, each warranty value represents battery usage at the time the measurements were recorded. Once received, measurements may be converted to associated factors for use in calculating a warranty value. For example, a voltage measurement may be converted to a corresponding voltage factor as described with respect to
In an embodiment, a warranty value may be calculated by multiplying the voltage factor, temperature factor, and current factor together. For example, the current factor may be 0 when a battery pack is neither charging nor discharging. The calculated warranty value will therefore also be 0, indicating that no usage is occurring. In another example, when battery temperature and voltage are at optimal levels, the corresponding temperature and voltage factors may be 1. The calculated warranty value will then be equal to the current factor corresponding to the measured electric current. When all factors are greater than zero, the warranty value indicates battery usage based on each of the voltage, temperature, and electric current measurements.
As described previously, additional measured or calculated data may also be used in the calculation of a warranty value. A warranty value may also be calculated based on any combination voltage, temperature, and current factors, according to an embodiment.
At stage 2312, the calculated warranty value is added to a stored cumulative warranty value. In an embodiment the cumulative warranty value may be stored within the battery pack. In other embodiments, the cumulative warranty value may be stored external to the battery pack. The cumulative warranty value may then be used to determine whether the battery pack warranty is active or expired, as will be discussed further with respect to
At stage 2404, the cumulative warranty value stored in the defective battery pack is compared to a predefined threshold value. This threshold value may be set to provide a certain warranty period based on normal usage of the battery pack. For example, the threshold may be set such that a battery pack may be covered under warranty for 10 years based on normal usage. In this manner, aggressive usage of the battery pack may reduce the active warranty period for the battery pack.
At stage 2406, it is determined whether the stored cumulative warranty value exceeds the predefined threshold value. If the stored cumulative value exceeds the predefined threshold value, method 2400 proceeds to stage 2408. At stage 2408, the warranty for the battery pack is determined to be expired. If the stored cumulative value does not exceed the threshold value, the method ends, indicating that the battery pack warranty has not expired.
In an embodiment, battery pack 2504 may be connected to a computing device with display 2506. In this manner, the battery pack operator, seller, or manufacturer may be able to view various warranty information and status in order to determine which party is financially responsible for repairing battery pack 2504. In the example illustrated in
In an embodiment, warranty information for battery pack 2504 may be viewed without physically removing battery pack 2504 from electrical storage unit 2502. For example, stored warranty information may be sent via accessible networks to a device external to battery pack 2504 for analysis.
Example Detection of a Battery Pack Having an Operating Issue or Defect
Plot 2608 shows an analogous distribution of battery packs based on the charge time 2610 of each battery pack. In an embodiment, a timer may track the operating time of a balancing charger, such as balancing charger 632 of
As illustrated in
Temperature has a significant effect on the performance of a battery pack. For example, higher temperatures may increase the rate of self-discharge of a battery. In a non-limiting example, a battery pack may self-discharge 2% per month at a constant 20° C. and increase to 10% per month at a constant 30° C. Plot 710 shows the distribution of battery packs based on charge time 2706 with each battery pack having a temperature of 30° C. At 30° C., the charge times of each battery pack maintain a normal distribution, but the mean and expected charge time is shifted.
Because of distribution shifts at different temperatures, maximum variance 2708 may be updated to compensate for temperature fluctuations. In an embodiment, one or more temperature sensors may monitor the average battery cell or battery module temperature of a battery pack. The temperature sensors may be internal or external to the battery pack. Maximum variance 2708 may then be adjusted dynamically in response to temperature changes. For example, if the average battery module temperature of a battery pack is determined to be 30° C., the maximum expected variance may be adjusted to maximum variance 2712. This may prevent replacement of healthy battery packs, for example, when charge time of a battery pack falls between maximum variance 2708 and maximum variance 2712 at a temperature of 30° C. In other embodiments, environmental temperature may be monitored instead of or in combination with battery module temperatures, and maximum variance 2708 may be adjusted dynamically in response to environmental temperature changes.
In an embodiment, timer 2806 records the amount of time that balancing charger 2804 is operating. Timer 2806 may be embedded in the battery pack as part of a battery pack controller, such as battery pack controller 800 of
In an embodiment, timer 2806 may periodically send recorded operating times to analyzer 2808. In an embodiment, analyzer 2808 may be a part of battery pack 2802. For example, analyzer 2808 may be integrated into a battery pack controller of battery pack 2802, such as battery pack controller 800 of
In an embodiment, analyzer 2808 may select a time period and compare recorded operating times for the selected time period to a threshold time. The threshold time may indicate a maximum determined variance from the expected operating time of balancing charger 2806. The expected operating time may represent the expected charge time of the battery pack for the selected time period, taking into account factors such as, but not limited to, battery usage and self-discharge rate. Analyzer 2808 may set expected operating times and threshold times based on statistical analysis of data collected from a plurality of battery packs and may be adjusted as additional data is collected. If battery pack 2802 is part of an array of battery packs, expected and threshold operating times may be determined based on analysis of all or a subset of battery packs in the array. Additionally, in an embodiment, the threshold time may be dynamically adjusted based on the average battery cell or battery module temperature of the battery back or the environmental temperature surrounding the battery pack, as described with respect to
In an embodiment, if the recorded operating time exceeds the threshold time, analyzer 2808 may determine that the battery pack has an operating issue or defect and may require maintenance and/or replacement. In this case, analyzer 2808 may issue an alert to an appropriate party, such as an operator responsible for monitoring the battery pack. In an embodiment, the alert may be issued as an email or other electronic communication. In other embodiments, the issued alert may be audial or visual, for example a flashing red light on the battery pack, such as the warnings described above with respect to status button 608 of
In an embodiment, analyzer 2808 may also halt operation of the battery pack in response to determining that the battery pack has an operating issue or defect. This may act as a mechanism to preclude any adverse effects that may occur from operating a battery pack having an operating issue or defect.
In an embodiment, recorded times for each battery pack may be aggregated by one or more string controllers (such as string controller 504 of
In an embodiment, the aggregated recorded times may be sent by the one or more string controllers or the array or system controller to one or more analyzers 2910, such as analyzer 2808 of
Method 3000 begins at stage 3002 by recording the amount of time that a balancing charger is operating. The balancing charger may be part of the battery pack, such as balancing charger 632 of
At stage 3004, the recorded operating time for a particular time period is compared to a threshold time. The threshold time may indicate a maximum determined variance from the expected operating time of the balancing charger. The expected operating time may represent the expected charge time of the battery pack for the time period, taking into account factors such as, but not limited to, battery usage and self-discharge rate.
At stage 3006, it is determined whether the recorded operating time exceeds the threshold time. This may indicate that the battery pack is charging longer than expected and may require maintenance and/or replacement. At stage 3008, if the recorded operating time exceeds the threshold time, an alert may be provided to an appropriate party, such as a computer or a human operator responsible for monitoring the battery pack (e.g., at energy management system 360 of
It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present disclosure as contemplated by the inventor(s), and thus, are not intended to limit the present disclosure and the appended claims in any way.
Embodiments of the present disclosure have been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. Also, Identifiers, such as “(a),” “(b),” “(i),” “(ii),” etc., are sometimes used for different elements or steps. These identifiers are used for clarity and do not necessarily designate an order for the elements or steps.
The foregoing description of specific embodiments will so fully reveal the general nature of the inventions that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present disclosure. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance.
The breadth and scope of the present disclosure should not be limited by any of the above-described embodiments, but should be defined only in accordance with the following claims and their equivalents.
This application is a continuation of U.S. application Ser. No. 14/932,688, filed Nov. 4, 2015 (issuing as U.S. Pat. No. 9,882,401), which is hereby incorporated herein by reference in its entirety.
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Number | Date | Country | |
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Number | Date | Country | |
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Parent | 14932688 | Nov 2015 | US |
Child | 15882713 | US |