Method and system for increasing capacity of a battery of an electric vehicle prior to kinetic energy capture

Abstract

A system and a method for increasing capacity of a battery for an electric vehicle during mining operations. The systems and methods provide a battery management software application that allows vehicle operators to designate a value for a target state of charge (SoC) of the battery before initiating a downhill tramming operation that will engage a kinetic energy capture system. The current SoC of the battery is monitored, and when it exceeds the target SoC and the vehicle is connected to a power grid, a power dump can be triggered. The power dump causes a discharge of the battery to a level corresponding to the target SoC. The vehicle can then recharge the battery with a substantially greater net charge in a subsequent downhill tramming operation.

Description

METHOD AND SYSTEM FOR INCREASING CAPACITY OF A BATTERY OF AN ELECTRIC VEHICLE PRIOR TO KINETIC ENERGY CAPTURERELATED APPLICATIONS

[0001] The present application claims the benefits of priority of U.S. Provisional Patent Application No. 63 / 622,688; entitled “ENERGY DISCHARGE TO POWER GRID IN MINING OPERATIONS FOR INCREASING BATTERY CAPACITY”; and filed at the United States Patent and Trademark Office on January 19, 2024; the content of which is incorporated herein by reference.TECHNICAL FIELD

[0002] The present description relates generally to providing mechanisms by which excess battery energy can be discharged.BACKGROUND

[0003] Mining vehicles are often equipped with an electrical drive system that includes electric motors which drive the wheels. These vehicles can then draw electrical power from an onboard electrical generator that is powered by the vehicle’s engine during its operations. In addition, during downhill travel (tramming), the electric motor brakes, and this braking power can be captured and used to charge an onboard electrical energy storage system, also known as a regenerative kinetic energy capture system.

[0004] It can be appreciated that electrical power captured by such a regenerative kinetic energy capture system associated with an electric vehicle may then be used to charge the onboard battery of the vehicle. However, if the onboard battery is fully charged before beginning a downhill operation, the battery may not have enough capacity to receive the regenerative energy produced during the descent.SUMMARY

[0005] Systems and methods that can transfer the excess battery energy before a descent to a desired state of charge (SoC) can ensure the battery is able to take advantage of the regenerative energy supplied during each descent and would also provide significant operational and cost advantages.

[0006] In one aspect, a computer-implemented method of increasing capacity of a battery prior to kinetic energy capture events is disclosed. The method includes a first step of receiving a selection of a target state of charge (SoC) value for a battery onboard the electric vehicle. A second step includes determining both that: (a) the battery has, at a first time, a first SoC value that exceedsthe target SoC value, and (b) the battery is currently connected to a power grid. In addition, a third step includes executing a power dump whereby the battery is discharged to the power grid until the SoC of the battery drops from the first SoC value to a second SoC value that is less than or equal to the target SoC value.

[0007] In another aspect, a system for increasing capacity of a battery prior to kinetic energy capture events is disclosed. The system comprises a processor and machine-readable media including instructions which, when executed by the processor, cause the processor to: receive a selection of a target state of charge (SoC) value for a battery onboard the electric vehicle; determine both that: the battery has, at a first time, a first SoC value that exceeds the target SoC value, and the vehicle is currently connected to a power grid; and execute a power dump whereby the battery is discharged to the power grid until the SoC of the battery drops from the first SoC value to a second SoC value that is less than or equal to the target SoC value.

[0008] In another aspect, a non-transitory computer-readable medium storing software comprising instructions executable by one or more computers is disclosed. The non-transitory computer- readable medium stores software comprising instructions which are executable by one or more computers and which, upon such execution, cause the one or more computers to: receive a selection of a target state of charge (SoC) value for a battery onboard the electric vehicle; determine both that: the battery has, at a first time, a first SoC value that exceeds the target SoC value, and the vehicle is currently connected to a power grid; and execute a power dump whereby the battery is discharged to the power grid until the SoC of the battery drops from the first SoC value to a second SoC value that is less than or equal to the target SoC value.

[0009] Other systems, methods, features and advantages of the disclosure will be, or will become, apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description and this summary, be within the scope of the disclosure, and be protected by the following claims.BRIEF DESCRIPTION OF THE FIGURES

[0010] The disclosure can be better understood with reference to the following figures and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the disclosure. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views.

[0011] FIG. 1 depicts an example of a drill rig for a mining operation, according to an embodiment;

[0012] FIG. 2 shows a schematic flow diagram of a process for performing a power dump, according to an embodiment;

[0013] FIG. 3 shows an example of an onboard user interface for a battery management software application for initiating the power dump, according to an embodiment;

[0014] FIGS. 4A-4E is a depiction of a process in which energy is discharged to a mine power grid, according to an embodiment;

[0015] FIG. 5 is a flow diagram showing a flow of current during the power dump, according to an embodiment; and

[0016] FIG. 6 is a flow chart depicting a process for increasing capacity of a battery prior to kinetic energy capture events, according to an embodiment.DETAILED DESCRIPTION

[0017] Providing power to sub-surface mining operations can present various challenges. For deep mines, transmitting the energy from the surface may be inefficient, and generating the power at depth may generate toxic emissions that are costly to dissipate and control. In particular, tramming operations are especially challenging for battery-powered mining vehicles (e.g., drill rigs) when beginning a downhill drive. For example, in cases where the batteries are fully or near-fully charged before a downhill drive, the batteries will lack the capacity to take advantage of the kinetic energy that becomes available as the vehicle performs regenerative braking. In other words, the vehicle’s regenerative braking capacity is diminished, and the drill rig will be required to greatly reduce its downhill tramming speed.

[0018] While capacity can be increased by dissipation of battery energy via hydraulic systems or compressor retarders, brake resistors, brake chopper devices, etc., these options are costly and remain unreliable. The proposed embodiments provide for systems and methods for discharging a battery before a downhill drive that is efficient and can be implemented in most mining environments. In one embodiment, the proposed techniques can enable electric mining vehicles (e.g., battery-powered mining drill rigs) to feed battery energy back to the power grid of the mine prior to a downhill drive. The approach described herein can be used to selectively target and tune a battery’s capacity and then discharge or otherwise dump the selected amount of power from the battery to the power grid before performing the downhill drive, allowing the battery increased capacity to receive additional charge during the descent. Furthermore, this approach offers greater sustainability, as the energy that is discharged from the batteries to the power grid can be utilized for other purposes, rather than simply becoming dissipated as heat to the ambient air.

[0019] As will be discussed in greater detail below, a drill rig operator can set a specific battery charge level (state of charge, or SoC) and activate a transfer or dump of power from the battery to the grid. In response to this selection, the system can cause the battery to automatically drain itself (e.g., discharge) to the target SoC. In general, SoC refers to a level of charge of an electric battery relative to its capacity (i.e., the maximum possible charge that can be stored in the battery), and is used to describe the amount of electrical charge stored in the battery. SoC is often expressed as a percentage. Thus, a fully charged battery has an SoC of 100% while a fully discharged battery has an SoC of 0%.

[0020] Once the battery has been discharged, capacity is increased, and downhill tramming can be performed with improved tramming speeds. In some embodiments, a charging transformer sets the maximum power levels for the battery discharging. In some embodiments, the proposed embodiments enable high-speed, effective, and highly stable discharge of the onboard batteries to significantly improve downhill tramming performance. The approach also offers substantial reductions in cost as the vehicle no longer requires the additional expense of onboard brake resistors and / or brake chopper(s).

[0021] Simply for purposes of background context, some example systems and methods for using kinetic energy capture technologies to charge battery-powered mining vehicles are now described below with reference to FIG. 1. FIG. 1 presents a schematic diagram of an example of an electrically powered drilling machine (“drill rig”) 100 configured to move (and possibly drill) with onboard battery (electric energy).

[0022] As a general matter, the drill rig 100 has been developed to operate in a mine environment, in some cases utilizing only electric power for both moving the machine from a first position to a second position within the mine environment and also to power the drilling operations. Such a drill rig can therefore operate in a mine utilizing electrical power provided by the mine grid’s electric power 102 to operate its rock drilling units. The drill rig 100 may have one or more rock drilling units mounted thereto. However, in other machines, movement of the machine from one position to another position is typically done with an internal combustion engine, such as a diesel engine. Such engines generate particulate matter in the mine environment atmosphere which then requires expensive ventilation equipment in the mine which increases cost of operation of the mine and maintenance of the machine’s filter system. Thus, such machines can reduce or completely eliminate the need for an internal combustion engine for moving the machine from a first position to a second position.

[0023] For reference, in FIG. 1, the drill rig 100 includes a support structure or frame 104 configured to support the equipment used for both moving the drill rig and the equipment for adrilling operation. In some embodiments, the support structure 104 can be articulated and include a pivot between portions of the support structure 104.

[0024] In some embodiments, a rock drilling unit 112 can be mounted on a boom extending from the front of the support structure 104. In some embodiments, a second rock drilling unit 128 can be mounted on a separate boom also mounted on the front of the support structure 104. The booms are typically articulated by hydraulic actuators controlled by an operator of the drill rig 100 during a drilling operation. In some embodiments, the support structure 104 includes ground engaging elements, such as wheels 110, 118. In the illustrated embodiment, the support structure 104 has a first wheel set and a second wheel set. Each wheel set can be operated independently and also can be operated simultaneously as determined by an operator of the drill rig.

[0025] In some embodiments, support structure 104 also provides a platform for mounting the various components of the drill rig 100. In one example, a self-contained battery module such as battery module 140 is mounted on the support structure 104. In other examples, the drill rig 100 comprises one or more battery modules 142. The battery modules 140 can be configured to be recharged while on the support structure 104. A number of battery modules, for example two or three modules, can be included and installed on the support structure 104.

[0026] In some embodiments, an AC motor 114 is mounted on the support structure 104 and coupled to at least one wheel set and the battery module 140. In one example, the AC motor 114 is configured to receive the power from the battery module 140 through an inverter and variable speed drive unit. In some embodiments, the AC motor 114 is an electric induction motor. In some embodiments, there may be multiple AC motors 114. In different embodiments, the drill rig 100 can also be configured with a DC motor in some embodiments, for example a brushless DC motor or a switched reluctance motor (SRM). In one example, the electric induction motor is properly sized for the particular operation of the drill rig 100 and can be, for example with a rated horsepower in the range of 50 to 150 horsepower or such other appropriate horsepower rating needed for a specific application. In some embodiments, the electric motor is configured to drive hydraulic pumps at either a constant speed, or a variable speed to maximize the efficiency of the electric / hydraulic circuit. The electric motor may also be configured with a speed feedback circuit utilizing either encoders coupled to the motor and hydraulic pump or with a sensorless configuration through software installed on a system controller provided on the drill rig 100. In different embodiments, the AC motor 114 can also receive electric power from the provided AC mine grid’s electric power 102 through a transformer. In some embodiments, an electric switch device, as controlled by the system controller, can switch the AC motor 114 between electric power from one of the battery modules 142 and the provided AC electric power 102. In one example, thesystem controller in conjunction with input controls, for example joy-sticks, operates the various functions on the powered drill rig 100.

[0027] In different embodiments, the battery charger(s) 175 is in electrical communication with each battery module 140. The battery charger(s) 175 can be mounted on the support structure 104. The battery charger(s) 175 may include a battery status (health) monitoring and management system. As illustrated in FIG. 1, a plurality of battery chargers 175 are mounted on the support structure 104 above each of the battery modules 140. In some embodiments, the battery chargers 175 are each also coupled by appropriate electrical cables to the provided AC electric power 102. For example, an electric cable 126 is mounted on a cable reel 124 coupled to the support structure 104. In different embodiments, the electric cable 126 mounted on the cable reel 124 can be coupled to power stations within the mine environment and are coupled to the provided AC electric power 102. As the drill rig 100 moves from a first position to a second position in the mine, the electric cable 126 is unreeled as the support structure 104 is moved. Thus, the provided AC electric power 102 can be used to power the drilling operation and charge the battery modules 142.

[0028] It should be noted that due to mine regulations, the electric cable coupling the drill rig 100 to the mine providing AC electric power 102 is limited in distance and therefore the mine typically may provide a plurality of power stations or move a power station within the mine to accommodate the drill rig 100. Movement of the drill rig 100 is accomplished utilizing the electric power from the battery modules 140 to power the AC motor 114 for moving the mobile drill 100 from a first position to a second position.

[0029] As noted above, in different embodiments, operation of drill rig 100 is configured such that the movement of the drill rig 100 is accomplished by electric power provided by the battery modules 140 through the appropriate electrical-mechanical driveline and / or electric / hydraulic circuit. In addition, the drilling operation can be accomplished by utilizing the electric power provided by the mine’s power grid via the appropriate electric / hydraulic circuit. In some embodiments, during a drilling operation, the provided electric power 102 can also be utilized to charge the battery modules 142 through the battery charger 175. In some embodiments, the drilling operation can proceed for some duration (e g., one hour) during which the appropriate holes are drilled in the mine face. During the same time period, the batteries are being charged via the connection to the power grid.

[0030] In some embodiments, a system controller can control the system so that the batteries will be charged for a predetermined period to replace the spent energy from the previous movement of the drill rig 100, i.e. , movement from the first position to the second position. Upon completion of the drilling operation, utilizing the provided AC electric power 102, the electric cable 126 can bereeled up onto the cable reel 124 and the drill rig 100 is moved, utilizing the electric energy from the battery modules 142 to a new drilling position within the mine environment. In an appropriate position, the electric cable 126 from the reel 124 is again coupled to a mine power station that connects to the mine power grid to establish provided AC electric power with the drill rig 100 moving onto the next drilling position as the electric cable is unreeled from the reel 124. During the movement of the drill rig 100, power is again provided through the battery modules 142. At the new drilling position, the provided AC electric power 102 is utilized to operate the drills 112 and to charge the battery modules 142 through the battery chargers 175.

[0031] In different embodiments, drill rig 100 operates without the provided mine AC electric power 102. For example, in some embodiments, the electric power for operating the drill motor and the hydraulic motor for tramming the vehicle from a first position to a second position can be provided solely by the battery modules 142, where the size and capacity of the battery modules are configured to provide the appropriate and necessary electrical power for all functions of the drill rig 100 for a given time period and given operation. When the electric energy of the battery modules 142 are depleted to a predetermined level, the drill rig 100 can be moved to an appropriate recharge station to replenish the electric energy in the battery module.

[0032] Various systems within the mine may draw power from the mine’s power grid. Examples of such systems include the drill rig 100 during drilling operations (e.g., see FIG. 1), ventilation system for maintaining appropriate air quality within the mine Lights in the mine may be run from the power grid. Climate control, such as air conditioning, fans, and / or heaters may draw power from the power grid. Pumps for controlling water within the mine or for directing water to an ore face for assisting in extraction operations may be powered by the power grid. Conveyors for moving ore, equipment, and / or personnel within the mine may use power from the power grid. A crusher for breaking ore down into smaller or more uniform pieces than extraction can produce may be part of the mine’s electrically powered operations.

[0033] Moving now to FIG. 2, a schematic diagram depicts an embodiment of a process 200 for a separate power dump (discharge) feature in mining operations. As noted earlier, the proposed embodiments are directed to techniques by which excess energy (reflected as a diminishing SoC value) can be discharged from the vehicle’s batteries to the mine’s power grid. This process can be performed during the drilling phase (e.g., charging while drilling but with the opposite functionality) or when the drill rig is standing idle. In other words, the power dump can occur prior to the driving phase in which regenerative braking will be used.

[0034] As shown in FIG. 2, the process can be initiated via a power dump request 210 submitted to the onboard computing system by an operator of the rig. In different embodiments, onboardcomputing system can include a device processor and a non-transitory computer readable medium, such as a memory, including instructions executable by the device processor to perform the processes discussed herein. For example, the computer readable medium may include instructions stored thereon and executable by the device processor for controlling articulation of the vehicle. In some embodiments, the non-transitory computer readable medium may include any suitable computer readable medium, such as a memory, e.g., RAM, ROM, flash memory, or any other type of memory known in the art. In some embodiments, the non-transitory computer readable medium may include, for example, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of such devices. More specific examples of the non-transitory computer readable medium may include a portable computer diskette, a floppy disk, a hard disk, a read-only memory (ROM), a random-access memory (RAM), a static random-access memory (SRAM), a portable compact disc read-only memory (CD-ROM), an erasable programmable read-only memory (EPROM or Flash memory), a digital versatile disk (DVD), a memory stick, and any suitable combination of these exemplary media. A non-transitory computer readable medium, as used herein, is not to be construed as being transitory signals, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire.

[0035] The computing system may further include networking hardware configured to interface with other nodes of a network, such as a LAN, WLAN, or other networks. In some cases, communications between components may be made via the Internet, a cellular network, WIFI, or other suitable communications network. Any suitable communication platforms and / or protocols may be utilized for communication between one component and other components of the system. Since the various sources of information may each have their own platform and / or protocol, the system may be configured to interface with each platform and / or protocol to receive the data.

[0036] For purposes of illustration, an example scenario in which an operator selects a target SoC for the vehicle’s batteries and initiates or activates a power dump via an onboard user interface 320 for a battery management software application 350 is depicted in FIG. 3. In one example, the application 350 can be accessed via a display for an onboard computing device of mining vehicle 300. In this case, an operator 310 can view user interface 320 and monitor and / or adjust settings associated with the vehicle’s batteries. In the example of FIG. 3, a dashboard 330 is presented via user interface 320 that summarizes the status of the vehicle’s three batteries, including a first battery (“Battery 1”), a second battery (“Battery 2”), and a third battery (“Battery 3”). For eachbattery, an SoC is displayed, as well as the battery’s temperature (which can affect charging and discharging rates).

[0037] Furthermore, user interface 320 provides a set of battery management options 360 that permit the operator 310 to establish target charge levels for each individual battery, or for all of the batteries collectively. In this case, the operator 310 has selected a target SoC of 30% via a charge level input element 340 (shown here as an input stepper element with a minus option for decreasing the target value and a plus option for increasing the target value). In other examples, the operator may be shown a manual input field that allows the operator to input the numerical value directly, a slider that allows the operator to drag a knob or button to the desired target value, or an input dropdown that allows the operator to select an option from a dropdown list (e.g., 1- 100%). This target value (e.g., 30%) can then be applied to the operator’ s larger battery SoC goal, whether as a target charge level (via charge option 342) or a target discharge level (via discharge option 344). In this example, the first battery SoC is 92% (above the currently selected target value), the second battery SoC is 93% (also above the currently selected target value), and the third battery SoC is 81% (above the currently selected target value). In other instances, the SoC for a given battery may be lower than the currently selected target value, which can affect how and to what extent the system will perform a charge or discharge of each battery.

[0038] In different embodiments, the operator 310 can then decide whether they want the batteries to charge or discharge one or more (or all) of the batteries to their selected target value. For purposes of this example and in concert with the process depicted in FIG. 2, the operator selects the discharge option 344. Although only one discharge option is shown in FIG. 3 for purposes of simplicity, it should be understood that there may be a separate battery discharge option and / or battery charge option presented at the user interface for each battery onboard, allowing the operator to fine-tune the charging / discharging of each battery individually, particularly in cases where one battery has an SoC that is above the target value and another battery has an SoC that is below the target value. In some other embodiments, the user interface 320 can provide individual target charge input fields that are to be assigned to each battery, rather than a single target value that should be applied to all of the batteries. In other examples, the battery management options 360 can include a battery disconnect option 346 that triggers disconnection of one or more batteries from the system, a charge to full option 352 that initiates a full-charge operation, and a battery calibration option 354. In some embodiments, the user interface 320 can also offer a battery performance option 356 by which the operator 310 can select a level for usage of the battery energy (e.g., off, low, moderate, high, full) during drilling.

[0039] Once the operator selects the discharge option 344, the system can initiate a power dump. Returning now to FIG. 2, the resultant power dump process automatically carried out in response to the operator’s selections is described in greater detail. Following receipt of a power dump request 210, a battery power dump management system (“system”) can enter a first stage 230 involving an automated preconditions check. This ensures that certain requirements are met (specific conditions are detected / verified) before any further action can be taken by the system. In some embodiments, preconditions 220 include (a) a first requirement / condition 222 whereby the system must determine whether the battery’s actual SoC is greater than the selected target SoC, and / or (b) a second requirement / condition 224 whereby the system must determine whether there is a power grid connection available to dump power into (i.e., whether the drill rig 100 is connected to the power grid).

[0040] In some embodiments, the system can include provisions for determining the charge or state of each of the onboard batteries (e g., determine the SoC of the battery). This may be accomplished using any method known in the art. As noted above, a dashboard in the vehicle may display this information in real-time with a constant or continuous measuring of the battery charge. The vehicle operator may then confirm if the battery has reached the predetermined discharge level. Such constant measuring of a battery charge level is well known and common in electric and hybrid vehicles. Thus, in some embodiments, each of the preconditions 220 serves as a basis for a decision point in the power dump process. If the battery’s SoC is lower than or equal to the target SoC, the system will refrain from performing a power dump.

[0041] However, if both of the preconditions 220 are met, such that the actual SoC is greater than the target SoC, and a power grid connection is detected / available, the system can move to a second stage 250 in which the power dump is executed (performed / activated). In some embodiments, these preconditions 220 are continuously monitored by the system, and the power dump is executed in a dump stage 250 at the earliest time that the preconditions are deemed satisfied following the request 210, causing current to flow from the onboard batteries to the power grid. As long as the preconditions 220 remain unmet, a hold stage 240 is maintained in which the power dump operation remains inactive / deactivated or otherwise blocked or prevented from being executed.

[0042] Before and once a power dump is triggered (e.g., when the dump procedure is activated / selected, but prior to the power dump execution), a sequence of operations can be performed in preparation for the upcoming power dump. As shown in FIG. 2, in some embodiments, one or more energy management metrics 260 can be monitored in order to calculate discharging power (calculation stage 270) that will be required to perform the dump. For example,metrics 260 can include data reflecting the (a) target discharge power, (b) battery discharge current limits, (c) grid connection limit, (d) temperature derates (e.g., specifications showing how a rating stated at a particular temperature is reduced at higher temperatures), and other component-specific limits. These data can be processed by the system to calculate a maximum discharging power 280 that may be automatically applied by the system when executing the power dump. It should be noted that in different embodiments, discharging power can also be continuously (dynamically) adjusted in response to the maximum power level (e.g., the target SoC) selected by the operator. Some example power adjustment techniques that may be employed include, but are not limited to, target DC-link voltage, current limit, torque limit, and maximum motoring power.

[0043] For purposes of illustration, FIGS. 4A-4E show an embodiment of a process by which a power dump can be executed. At a first time T1 in FIG. 4A, the drill rig 100 has arrived at a first site at which a drilling operation is to be performed. The battery module 140 (which here represents all batteries onboard) is schematically represented to indicate the SoC at each time. In this case, the first site includes a connection to the electric power 102 supplied by the mine’s power grid. The vehicle’s onboard chargers 175 are connected to the electric power 102 to enable access to the power for the drilling operation that is to occur nearby. The battery module 140 currently is at a first charge state 422. In FIG. 4B, at a second time T2, electric cable 126 has been extended and connected to the grid for access to electric mine power 102, thereby initiating a charging session whereby the SoC of battery module 140 is increased to a second charge state 424 and the drilling operation is powered via the mine power grid. This process of charging (e.g., employing the vehicle’s onboard charger) while the mining operation is conducted continues until the battery module 140 is fully charged or the drilling operation is concluded. In FIG. 4C, at a third time T3, the battery module 140 has become fully charged at a third charge state 428 and the drilling successfully completed.

[0044] At this time, the operator may appreciate that their upcoming operation(s) include downhill tramming events in which kinetic energy capture is to occur. In conventional scenarios, with a fully charged battery, the drill rig 100 would be forced to dissipate energy during the drive. However, as shown in FIG. 4D, in some embodiments, the operator can now instruct the drill rig 100 to dump energy from the battery module 140 before disconnection from the mine’s power grid, and transfer this extracted energy back to the power grid.

[0045] At a fourth time T4, as one example, if a vehicle such as drill rig 100 determines its onboard battery charge has reached a predetermined level that is greater than the target SoC (as selected previously by the operator when opting to execute the power dump feature), and the system confirms that the connection to the power grid is still available, the system can cause (via onboardbattery charger 175) the battery module 140 to begin discharging the battery, such that the battery module 140 now enters a discharging state 435. At this time, the SoC of the battery module 140 begins to drop, falling to a fourth charge state 435 that is less than a full charge but still higher than the target SoC. Finally, in FIG. 4E, the system determines the battery module 140 has reached a fifth charge state 440 that is substantially equal to the target SoC and terminates the discharging session. The drill rig 100 can then be disconnected from the power grid at a fifth time T5 and proceed to engage in any downhill tramming operations during which kinetic energy can be captured and stored in the carefully modulated capacity that is now available in the battery module 140. In other words, once the onboard battery has been discharged to its designated target charge state or “target SoC” (selected by the vehicle operator, as represented in FIG. 3), the vehicle may be ready to take advantage of further charging events (e.g., through regenerative braking).

[0046] In some embodiments, the battery charger 175 depicted in FIGS. 4A-E may be a bidirectional charging system. The battery charger 175 can be electrically linked to the mine’s power grid. As power is drained from the battery due to the discharging, power is fed to the mine power grid through the onboard battery charger 175. The mine power grid may include capacitors, rechargeable batteries, or other provisions for receiving the discharged power from the battery via battery charger 175. The mine power grid may then use the discharged power to run the mine electrical systems, such as lights, climate control systems, ventilation systems, and the like, as well as be returned to the drill rig 100 itself at a later time during a subsequent drilling operation. It can be understood that discharging the battery transfers the energy stored in the battery to the mine’s power grid via the battery charger 175. Transferring the energy from the battery into the mine’s power grid may be accomplished using any method known in the art. The power grid may contain energy storage devices like capacitors and batteries to receive and store the transferred energy.

[0047] In some embodiments, battery charger 175 system is configured to adapt the power (e.g., voltage, current, frequency) received from the onboard battery to be compatible with the operating parameters (e.g., voltage, current, frequency) of the mine’s power grid.

[0048] In some embodiments, the battery charger 175 may include any type of charging and discharging system known in the art. In some embodiments, battery charger 175 may include a grid connection, one or more networks (e.g., the Internet), a remote terminal (e.g., a personal computer), and a remote data store. The battery charger 175 may support various AC systems. For example, battery charger 175 may support an AC system associated with an AC supply. For example, battery charger 175 may support various voltages, current, power, frequencies (e g., 50 Hz, 60 Hz), number of phases, and the like. In the example, battery charger 175 may support a 480 / 600 volt AC voltage.

[0049] Similarly, battery charger 175 may support charging and discharging with various DC systems. For example, battery charger 175 may support a DC system associated with a battery. For example, battery charger 175 may support a 480 volt DC voltage. In other examples, battery charger 175 may support a 240 volt DC voltage. In some examples, battery charger 175 may support a 65 kW DC power output. In other examples, battery charger 175 may support a 100 kW DC power output.

[0050] In some embodiments, the battery charger 175 comprises a bi-directional converter. In such embodiments, the bi-directional converter of battery charger 175 may use various types of converter topologies including, for example, buck, boost, buck-boost, and the like. Similarly, the bi-directional converter may use various types of inverter topologies including, for example, a grid-tie inverter system, a square wave, modified square wave, modified sine wave, pure sine wave, and the like. The topologies used in the bi-directional converter may support a bi-directional function. As used herein, bi-directional DC / AC converter may include a converter configured to (1) convert from the DC system to the AC system and (2) convert from the AC system to the DC system. In some embodiments, the bi-directional converter may include an AC to DC converter for converting from the AC system to the DC system and a DC to AC inverter for converting from the DC system to the AC system. In other embodiments, a single converter is used to convert between the AC and the DC systems.

[0051] Additional details regarding one possible embodiment of a battery charger 175 for use in a method for providing power to / from a mine are described in Huff et al., “System and Method for Battery Pack Charging and Remote Access,” U.S. Patent Application Number 14 / 529,853, filed on October 31, 2014.

[0052] In some embodiments, the battery is automatically discharged into the mine’s power grid until the battery charge is determined by the system to have reached the target SoC. This process may take several minutes to several hours, depending upon the capacity of the battery and the charged state of the battery.

[0053] As in the embodiment shown in FIG. 4A, battery charger 175 is electrically linked to the mine’s power grid. As power is drained from battery 414 due to the discharging, power is fed to the mine power grid through battery charger 175. The mine power grid may include capacitors, rechargeable batteries, or other provisions for receiving the discharged power from battery 414 via battery charger 175. The mine power grid may then use the discharged power to run the mine electrical systems, such as lights, climate control systems, ventilation systems, and the like. Battery 414 is then discharged to the operator- selected target SoC 440.

[0054] An embodiment of the disclosed processes is also schematically represented by the simplified diagram of FIG. 5 depicting a flow of current 500 during this discharge operation. The current is initially held at battery 502. Once the power dump is activated, the current can be discharged from the battery to an inverter 504. From there, the current is passed to a transformer 506, and then relayed to a connected power grid 508. This process continues until the target SoC is attained. In another embodiment, the current can be discharged from the battery to a DC / AC converter unit that can provide galvanic isolation between the battery and the mine’s power grid and serve the functions of both the inverter and the transformer.

[0055] Once a vehicle’s battery has been sufficiently discharged in accordance to the operator’s target SoC, the vehicle is now in a state in which it can take full advantage of its regenerative braking system or other kinetic energy capture system. As noted earlier, in some embodiments, the electric mining vehicle is configured to capture the kinetic energy of the vehicle as the vehicle travels downhill from the current drilling location to the next drilling location (e.g., charging the onboard battery with captured kinetic energy as the vehicle travels downhill). Kinetic energy capture systems are well known in the art. The captured kinetic energy is converted into electrical energy and stored in the vehicle’s onboard battery. Technologies for charging an onboard battery using captured and converted kinetic energy are also well known in the art, such as those systems associated with regenerative braking systems in electric and hybrid vehicles.

[0056] FIG. 6 is a flow chart illustrating an embodiment of a computer-implemented method 600 of increasing capacity of a battery of an electric vehicle prior to kinetic energy capture events. The method may be implemented in a system controller and / or onboard computing system of the electric vehicle (e g , drill rig 100). The method may also be implemented in collaboration with a battery management software application associated with the system controller and / or onboard computing system of the electric vehicle. The method 600 includes a first step 610 of receiving a selection of a target state of charge (SoC) value for a battery onboard the electric vehicle. A second step 620 includes determining both that: (a) the battery has, at a first time, a first SoC value that exceeds the target SoC value, and (b) the electric vehicle is currently connected to a power grid. In addition, a third step 630 includes executing a power dump whereby the battery is discharged to the power grid until the SoC of the battery drops from the first SoC value to a second SoC value that is less than or equal to the target SoC value.

[0057] In some embodiments, the method may include additional steps or aspects. In one embodiment, the method also includes automatically connecting, as part of executing the power dump, the electric vehicle to a discharging device to facilitate a flow of current from the battery to an inverter, from the inverter to a transformer, and from the transformer to the power grid. Inanother embodiment, the method further includes automatically disconnecting the electric vehicle from the discharging device in response to determining the second SoC value is less than or equal to the target SoC value. In some embodiments, the method also includes steps of capturing kinetic energy while the electric vehicle drives down a ramp; and thereby charging the battery to a third SoC value that is greater than the target SoC value. In one embodiment, the method further includes automatically deactivating execution of the power dump whenever a current SoC value of the battery is less than the target SoC value. In some embodiments, the battery can receive a greater net surplus energy charge from an onboard kinetic energy capture system after the power dump is executed than before the power dump is executed.

[0058] In some embodiments, the method also includes steps of connecting the electric vehicle to the power grid while the battery has a third SoC value that is less than the first SoC value; and conducting (or causing to conduct), by the electric vehicle, a drilling operation while the vehicle is connected to the power grid. In some embodiments, the method includes charging the battery from the third SoC value to the first SoC value during the drilling operation. In one embodiment, the first SoC value corresponds to a fully charged state for the battery. In another embodiment, the target SoC value is selected based on an anticipatory, estimated increase in charge that is to be delivered to the battery during an upcoming downhill tramming operation. In some embodiments, the method also includes performing (or causing to be performed), via the electric vehicle, a downhill tramming operation in which a first amount of kinetic energy is generated, and the first amount is equivalent to the capacity of the battery that became available following the power dump.

[0059] Other systems may be contemplated within the scope of the present disclosure. For example, a system for increasing capacity of a vehicle battery prior to kinetic energy capture events, is disclosed. The system can include (1) a battery associated with an electric vehicle, where the battery is configured to be charged by a kinetic energy capture system associated with the vehicle when the electric vehicle engages in a downhill tramming operation; (2) a discharging device connected to a power grid, where the discharging device is configured to discharge energy out of the battery and into the power grid when the battery is attached to the discharging device; and (3) a computing device onboard the electric vehicle that includes a battery management software application, the battery management software application providing a user interface including a first option for executing a power dump until a target state of charge (SoC) for the battery is attained, where a user designation of a value for the target SoC and selection of the first option causes the battery management software application to monitor the SoC of the battery and in response to determining the SoC exceeds the target SoC and the vehicle is connected to the power grid, execute the power dump.

[0060] In different embodiments of the system, the discharging device is a bidirectional charger. In some embodiments, the kinetic energy capture system is a regenerative braking system. In one example, the battery is configured to receive a greater net surplus energy charge from the kinetic energy capture system after the power dump is executed. In some embodiments, the electric vehicle engages in a downhill tramming operation comprising a trip down a ramp following the discharge event. In one example, execution of the power dump is automatically deactivated whenever the current SoC of the battery is less than the target SoC. In some embodiments, execution of the power dump is automatically deactivated whenever a disconnection between the battery and the power grid is detected. In another example, the battery is discharged to the target SoC by the battery management software application.

[0061] The processes and methods of the embodiments described in this detailed description and shown in the figures can be implemented using any kind of computing system having one or more central processing units (CPUs) and / or graphics processing units (GPUs). The processes and methods of the embodiments could also be implemented using special purpose circuitry such as an application specific integrated circuit (ASIC). The processes and methods of the embodiments may also be implemented on computing systems including read only memory (ROM) and / or random access memory (RAM), which may be connected to one or more processing units. Examples of computing systems and devices include, but are not limited to: servers, cellular phones, smart phones, tablet computers, notebook computers, e-book readers, laptop or desktop computers, all-in-one computers, as well as various kinds of digital media players.

[0062] The processes and methods of the embodiments can be stored as instructions and / or data on non-transitory computer-readable media. The non-transitory computer readable medium may include any suitable computer readable medium, such as a memory, such as RAM, ROM, flash memory, or any other type of memory known in the art. In some embodiments, the non-transitory computer readable medium may include, for example, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of such devices. More specific examples of the non- transitory computer readable medium may include a portable computer diskette, a floppy disk, a hard disk, magnetic disks or tapes, a read-only memory (ROM), a random access memory (RAM), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), an erasable programmable read-only memory (EPROM or Flash memory), electrically erasable programmable read-only memories (EEPROM), a digital versatile disk (DVD and DVD-ROM), a memory stick, other kinds of solid state drives, and any suitable combination of these exemplary media. A non-transitory computer readable medium, as used herein, is not to be construed as beingtransitory signals, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire.

[0063] Instructions stored on the non-transitory computer readable medium for carrying out operations of the present disclosure may be instruction- set-architecture (ISA) instructions, assembler instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, configuration data for integrated circuitry, state-setting data, or source code or object code written in any of one or more programming languages, including an object oriented programming language such as Smalltalk, C++, or suitable language, and procedural programming languages, such as the "C" programming language or similar programming languages.

[0064] Aspects of the present disclosure are described in association with figures illustrating flowcharts and / or block diagrams of methods, apparatus (systems), and computing products. It will be understood that each block of the flowcharts and / or block diagrams can be implemented by computer readable instructions. The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of various disclosed embodiments. Accordingly, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions. In some implementations, the functions set forth in the figures and claims may occur in an alternative order than listed and / or illustrated.

[0065] Implementations and all of the functional operations described in this specification may be realized in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Implementations may be realized as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer readable medium for execution by, or to control the operation of, data processing apparatus. The computer readable medium may be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter effecting a machine-readable propagated signal, or a combination of one or more of them. The term “computing system” encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus may include, in addition to hardware, code that creates an execution environment for the computer program in question, e g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal that is generated to encode information for transmission to suitable receiver apparatus.

[0066] A computer program (also known as a program, software, software application, script, or code) may be written in any appropriate form of programming language, including compiled or interpreted languages, and it may be deployed in any appropriate form, including as a standalone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program may be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e g., files that store one or more modules, sub programs, or portions of code). A computer program may be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

[0067] The processes and logic flows described in this specification may be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows may also be performed by, and apparatus may also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0068] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any appropriate kind of digital computer. Generally, a processor may receive instructions and data from a read only memory or a random-access memory or both. Elements of a computer can include a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer may also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. However, a computer need not have such devices. Moreover, a computer may be embedded in another device, e.g., a mobile telephone, a personal digital assistant (PDA), a mobile audio player, a GPS receiver, to name just a few. Computer readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and CD ROM and DVD-ROM disks. The processor and the memory may be supplemented by, or incorporated in, special purpose logic circuitry.

[0069] To provide for interaction with a user, implementations may be realized on a computer having a display device, e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor,for displaying information to the user and a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user may provide input to the computer. Other kinds of devices may be used to provide for interaction with a user as well; for example, feedback provided to the user may be any appropriate form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user may be received in any appropriate form, including acoustic, speech, or tactile input.

[0070] Implementations may be realized in a computing system that includes a back-end component, e.g., as a data server, or that includes a middleware component, e.g., an application server, or that includes a front end component, e.g., a client computer having a graphical user interface or a web browser through which a user may interact with an implementation, or any appropriate combination of one or more such back end, middleware, or front end components. The components of the system may be interconnected by any appropriate form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a local area network (“LAN”) and a wide area network (“WAN”), e.g., the Internet. The computing system may include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other.

[0071] While this specification contains many specifics, these should not be construed as limitations on the scope of the disclosure or of what may be claimed, but rather as descriptions of features specific to particular implementations. Certain features that are described in this specification in the context of separate implementations may also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation may also be implemented in multiple implementations separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination may in some examples be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

[0072] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood thatthe described program components and systems may generally be integrated together in a single software product or packaged into multiple software products.

[0073] While various embodiments of the disclosure have been described, the description is intended to be exemplary, rather than limiting, and it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the disclosure. Accordingly, the disclosure is not to be restricted except in light of the attached claims and their equivalents. Also, various modifications and changes may be made within the scope of the attached claims.

Claims

CLAIMSWhat is claimed is:

1. A method of increasing capacity of a battery of an electric vehicle prior to kinetic energy capture events, the method comprising: receiving a selection of a target state of charge (SoC) value for a battery onboard the electric vehicle; determining both that: the battery has, at a first time, a first SoC value that exceeds the target SoC value, and the electric vehicle is currently connected to a power grid; and executing a power dump whereby the battery is discharged to the power grid until the SoC of the battery drops from the first SoC value to a second SoC value that is less than or equal to the target SoC value.

2. The method of claim 1, further comprising automatically connecting, as part of executing the power dump, the electric vehicle to a discharging device to facilitate a flow of current from the battery to an inverter, from the inverter to a transformer, and from the transformer to the power grid.

3. The method of claim 2, further comprising automatically disconnecting the electric vehicle from the discharging device in response to determining the second SoC value is less than or equal to the target SoC value.

4. The method of claim 1, further comprising: capturing kinetic energy while the electric vehicle drives down a ramp; and thereby charging the battery to a third SoC value that is greater than the target SoC value.

5. The method of claim 1, further comprising automatically deactivating execution of the power dump whenever a current SoC value of the battery is less than the target SoC value.

6. The method of claim 1, wherein the battery can receive a greater net surplus energy charge from an onboard kinetic energy capture system after the power dump is executed than before the power dump is executed.

7. The method of claim 1, further comprising:connecting the electric vehicle to the power grid while the battery has a third SoC value that is less than the first SoC value; and conducting, by the electric vehicle, a drilling operation while the vehicle is connected to the power grid.

8. The method of claim 7, further comprising charging the battery from the third SoC value to the first SoC value during the drilling operation.

9. The method of claim 8, wherein the first SoC value corresponds to a fully charged state for the battery.

10. The method of claim 1, wherein the target SoC value is selected based on an anticipatory, estimated increase in charge that is to be delivered to the battery during an upcoming downhill tramming operation.

11. The method of claim 1, further comprising performing, via the electric vehicle, a downhill tramming operation in which a first amount of kinetic energy is generated, and the first amount is equivalent to the capacity of the battery that became available following the power dump.

12. A system for increasing capacity of a battery of an electric vehicle prior to kinetic energy capture events, the system comprising a processor and machine-readable media including instructions which, when executed by the processor, cause the processor to: receive a selection of a target state of charge (SoC) value for a battery onboard the electric vehicle; determine both that: the battery has, at a first time, a first SoC value that exceeds the target SoC value, and the electric vehicle is currently connected to a power grid; and execute a power dump whereby the battery is discharged to the power grid until the SoC of the battery drops from the first SoC value to a second SoC value that is less than or equal to the target SoC value.

13. The system of claim 12, wherein the instructions further cause the processor to automatically connect, as part of executing the power dump, the electric vehicle to adischarging device to facilitate a flow of current from the battery to an inverter, from the inverter to a transformer, and from the transformer to the power grid.

14. The system of claim 13, wherein the instructions further cause the processor to automatically disconnect the electric vehicle from the discharging device in response to determining the second SoC value is less than or equal to the target SoC value.

15. The system of claim 12, wherein the instructions further cause the processor to: capture kinetic energy while the electric vehicle drives down a ramp; and thereby charge the battery to a third SoC value that is greater than the target SoC value.

16. The system of claim 12, wherein the instructions further cause the processor to automatically deactivate execution of the power dump whenever a current SoC value of the battery is less than the target SoC value.

17. The system of claim 12, wherein the battery can receive a greater net surplus energy charge from an onboard kinetic energy capture system after the power dump is executed than before the power dump is executed.

18. The system of claim 12, wherein the instructions further cause the processor to: connect the electric vehicle to the power grid while the battery has a third SoC value that is less than the first SoC value; and conduct, by the electric vehicle, a drilling operation while the vehicle is connected to the power grid.

19. The system of claim 18, wherein the instructions further cause the processor to charge the battery from the third SoC value to the first SoC value during the drilling operation.

20. The system of claim 19, wherein the first SoC value corresponds to a fully charged state for the battery.

21. The system of claim 12, wherein the target SoC value is selected based on an anticipatory, estimated increase in charge that is to be delivered to the battery during an upcoming downhill tramming operation.

22. The system of claim 12, wherein the instructions further cause the processor to perform, via the electric vehicle, a downhill tramming operation in which a first amount of kineticenergy is generated, and the first amount is equivalent to the capacity of the battery that became available following the power dump.

23. A non-transitory computer-readable medium storing software comprising instructions executable by one or more computers which, upon such execution, cause the one or more computers to: receive a selection of a target state of charge (SoC) value for a battery onboard an electric vehicle; determine both that: the battery has, at a first time, a first SoC value that exceeds the target SoC value, and the electric vehicle is currently connected to a power grid; and execute a power dump whereby the battery is discharged to the power grid until the SoC of the battery drops from the first SoC value to a second SoC value that is less than or equal to the target SoC value.

24. The non-transitory computer-readable medium storing software of claim 23, wherein the instructions further cause the one or more computers to automatically connect, as part of executing the power dump, the electric vehicle to a discharging device to facilitate a flow of current from the battery to an inverter, from the inverter to a transformer, and from the transformer to the power grid.

25. The non-transitory computer-readable medium storing software of claim 24, wherein the instructions further cause the one or more computers to automatically disconnect the electric vehicle from the discharging device in response to determining the second SoC value is less than or equal to the target SoC value.

26. The non-transitory computer-readable medium storing software of claim 23, wherein the instructions further cause the one or more computers to: capture kinetic energy while the electric vehicle drives down a ramp; and thereby charge the battery to a third SoC value that is greater than the target SoC value.

27. The non-transitory computer-readable medium storing software of claim 23, wherein the instructions further cause the one or more computers to automatically deactivate executionof the power dump whenever a current SoC value of the battery is less than the target SoC value.

28. The non-transitory computer-readable medium storing software of claim 23, wherein the battery can receive a greater net surplus energy charge from an onboard kinetic energy capture system after the power dump is executed than before the power dump is executed.

29. The non-transitory computer-readable medium storing software of claim 23, wherein the instructions further cause the one or more computers to: connect the electric vehicle to the power grid while the battery has a third SoC value that is less than the first SoC value; and conduct, by the electric vehicle, a drilling operation while the vehicle is connected to the power grid.

30. The non-transitory computer-readable medium storing software of claim 29, wherein the instructions further cause the one or more computers to charge the battery from the third SoC value to the first SoC value during the drilling operation.

31. The non-transitory computer-readable medium storing software of claim 30, wherein the first SoC value corresponds to a fully charged state for the battery.

32. The non-transitory computer-readable medium storing software of claim 23, wherein the target SoC value is selected based on an anticipatory, estimated increase in charge that is to be delivered to the battery during an upcoming downhill tramming operation.

33. The non-transitory computer-readable medium storing software of claim 23, wherein the instructions further cause the one or more computers to perform, via the electric vehicle, a downhill tramming operation in which a first amount of kinetic energy is generated, and the first amount is equivalent to the capacity of the battery that became available following the power dump.

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