Charger and a method for estimating a time to a full charge of battery pack

Abstract

A battery pack charger for charging a removable, rechargeable battery pack. The battery pack charger is capable of and includes instructions for determining a state of charge in real time while charging the battery pack and estimating a remaining charging time until a charging sequence of the battery pack is complete. The charger also includes a display to present the real time state of charge and the estimated remaining time until the charging sequence is complete. The battery pack charger is capable of estimating the remaining time until the charging sequence is complete without knowing the capacity of the battery pack.

Description

Docket No. P-WO-TN-2024-1123CHARGER AND A METHOD FOR ESTIMATING A TIME TO A FULL CHARGE OF BATTERY PACK FIELD OF THE DISCLOSURE

[0001] The present disclosure relates to a charger that determines a state of charge (SoC) in real time while charging a battery pack that has a capacity unknown to the charger, and calculates, based on the SoC, an estimated time until the charging process is complete. The charger can thereby output status-related information to make the progress of the charging process easy and intuitive for the user to understand.BACKGROUND

[0002] A battery pack can power any of a variety of devices. A power tool may include a battery pack that can be charged to enable its operation. For example, a power tool (e g., a drill) may include a battery pack that can be removed for charging and then replaced after charging to enable use of the power tool. The battery pack can include one or more electrochemical cells for storing energy. The charging includes providing a direct current (DC) to positive and negative terminals of the battery pack. The time required to complete the charging varies significantly based, in part, on the initial SoC, the battery’s capacity, the charging rate, and temperature.

[0003] Generally speaking, if a battery pack’s capacity (C) is known and a fixed charge rate / constant current (Icc) is used to charge the battery pack (sometimes referred to as a constant current charging scheme), the time to charge (tcnc) from an empty state of charge (SoC = 0%) to a full state of charge (SoC = 100%) may be calculated by dividing the capacity of the battery pack by the charge current.

[0004] EQ.1: tCHG = C / ICC x (SOCFULL – SOCEMPTY)

[0005] For example, if C = 9Ah and Icc = 8 A, then tCHG = 9Ah / 8A = 1.125 h.

[0006] For a partial charge, EQ. 1 can be modified using an ending SoC (SOCEND) and a starting SoC (SOCSTART), where the SOCEND is not necessarily, but may be, a full state of charge and the SOCSTART is not necessarily, but may be, an empty state of charge.

[0007] EQ. 2: tcHG - C / Icc x (SOCEND - SOCSTART)Docket No. P-WO-TN-2024-1123

[0008] For example, if C = 9Ah, Icc = 8A, SOCEND = 90% = 0.9 and SOCSTART = 30% = 0.3, then tcHG = 9Ah / 8A x (0.9 - 0.3) = 0.675 hSUMMARY

[0009] An aspect of the present disclosure includes a method for estimating a remaining charging time of a charging sequence for charging a battery pack.

[0010] An example embodiment of the present disclosure includes a method of estimating remaining charging time of a charging sequence for charging a battery pack of a set of at least two battery packs, the charging sequence including a plurality of constant-current stages, the at least two battery packs having different capacities, the method comprising: receiving a battery pack of the set of at least two battery packs; determining a number of constant-current stages in the charging sequence; calculating a first direct current (DC) resistance of the received battery pack; determining an initial state of charge (SoC) of the received battery pack based upon the first DC resistance; beginning the charging sequence; waiting a predefined time period; determining an instantaneous SoC of the received battery pack based upon the first DC resistance; comparing the initial SoC and the instantaneous SoC; in response to the instantaneous SoC being greater than the initial SoC by a predefined amount then calculating a capacity of the received battery pack; calculating a second DC resistance of the received battery pack; determining, for each constant-current stage remaining in the charging sequence, an SoC corresponding to an end of the respective constant-current stage based upon the second DC resistance; calculating an expected duration of each of the constant-current stages remaining in the charging sequence; calculating a remaining charging time for the charging sequence based on the expected duration of each of the constant-current stages remaining in the charging sequence; and generating an output that reflects the remaining charging time.

[0011] The aforementioned example embodiment may include determining the initial SoC of the received battery pack based upon a first open circuit voltage and the first open circuit voltage calculated using the first DC resistance and a measured battery pack voltage and determining the SoC corresponding to the end of the respective constant-current stage based upon a second openDocket No. P-WO-TN-2024-1123circuit voltage and the second open circuit voltage calculated using the second DC resistance and a threshold voltage.

[0012] The aforementioned example embodiment may include measuring i) a voltage of the received battery pack when a current is not being applied to the battery pack (VOC) and ii) a voltage of the received battery pack when a current (ICHG) is being applied to the battery pack (VCHG); and iii) calculating the first DC resistance of the battery pack based on the applied current ICHG, the voltage VCHGand the voltage VOC.

[0013] The aforementioned example embodiment may include measuring a voltage of the received battery pack when the received battery pack is being charged with a charging current during the charging sequence (VM); and calculating an open circuit voltage of the received battery pack (VOC) based on the voltage VM, the charging current ICHGand the first DC resistance of the received battery pack.

[0014] The aforementioned example embodiment may include determining the instantaneous SoC of the received battery pack based on the open circuit voltage VOCand an SoC-VOCrelationship of the set of battery packs.

[0015] The aforementioned example embodiment may include determining each of the ending SoCs based on a current of the respective constant-current stage, the second DC resistance, an expected voltage of the received battery pack at the end of the respective constantcurrent stage, and the SoC-VOCrelationship.

[0016] The aforementioned example embodiment may include calculating the capacity of the received battery pack based on the charging current, a multiple of the predefined time period, and a difference between the instantaneous SoC and the initial SoC.

[0017] The aforementioned example embodiment may include calculating each expected duration of the constant-current stages based on the calculated capacity of the received battery pack, the current of the respective constant-current stage, and a difference between the ending SoC of the respective constant-current stage and a starting SoC of the respective constant-current stage.

[0018] The aforementioned example embodiment may include the voltage VCHG measured at a predefined time after the voltage Voc is measured.Docket No. P-WO-TN-2024-1123

[0019] The aforementioned example embodiment may include the current with which the battery pack is being charged when the voltage VCHGis measured is a constant current of one of the plurality of constant-current stages of the charging sequence.

[0020] The aforementioned example embodiment may include updating the second DC resistance to an updated second DC resistance during the charging sequence.

[0021] The aforementioned example embodiment may include updating the second DC resistance comprising performing determining a new voltage difference for the battery pack during the charging sequence and calculating the updated second DC resistance based on the new voltage difference and a current associated with the new voltage difference.

[0022] The aforementioned example embodiment may include a lookup table representing the SoC-Voc relationship and estimating the ending SoCs based in part on the SoC-Voc relationship comprises obtaining the ending SoCs from the lookup table.

[0023] The aforementioned example embodiment may include a function representing the SoC-Voc relationship, and estimating the ending SoCs based in part on the SoC-Voc relationship comprises calculating the ending SoCs using the function.

[0024] The aforementioned example embodiment may include the expected voltage of the battery pack at the end of the respective constant-current stage being a common expected voltage in each of the plurality of constant-current stages.

[0025] The aforementioned example embodiment may include the battery pack including a plurality of battery cells and the common expected voltage based on a threshold voltage of the battery cells.

[0026] The aforementioned example embodiment may include, for each constant-current stage of the plurality of constant-current stages except an earliest constant-current stage thereof, the starting SoC of the constant-current stage equal to the ending SoC of a preceding constantcurrent stage.

[0027] The aforementioned example embodiment may include a starting SoC of the earliest constant-current stage being the instantaneous SoC.

[0028] The aforementioned example embodiment may include continuously performing voltage measurements during the charging sequence to obtain updated voltage measurements;Docket No. P-WO-TN-2024-1123continuously calculating, during the charging sequence, the remaining charging time based in part on the updated voltage measurements and the charging sequence, to obtain updated remaining charging times; and continuously updating, during the charging sequence, the output to reflect the updated remaining charging times.

[0029] The aforementioned example embodiment may include continuously calculating, during the charging sequence, updated SoCs for the battery pack based in part on the updated voltage measurements and the charging sequence; and continuously updating, during the charging sequence, the output to reflect also the updated SoCs.

[0030] Another aspect of the present disclosure includes a battery pack charger that estimates a remaining charging time of a charging sequence for charging a battery pack.

[0031] An example embodiment of the present disclosure includes a charger comprising: terminals configured to be coupled to battery terminals of a received battery pack for charging the received battery pack, wherein the charger is compatible with each of multiple types of battery packs having different capacities; a power source to provide at least constant current to the terminals during a charging sequence; an output device; and circuitry comprising: a protocol defining the charging sequence; and instructions that when executed cause the charger to perform operations comprising: calculating a first direct current (DC) resistance of the received battery pack; determining an initial state of charge (SoC) of the received battery pack based on the first DC resistance; when the received battery pack has been charged with the charging current for a length of time, determining an instantaneous SoC of the received battery pack based on the first DC resistance; comparing the instantaneous SoC to the first initial SoC and when the instantaneous SoC is greater than the initial SoC by a predefined amount calculating a capacity of the received battery pack; calculating a second DC resistance of the received battery pack; determining, for each of a plurality of constant-current stages of the charging sequence, an SoC of the received battery pack corresponding to an end of the respective constant-current stage, each SoC of the received battery pack corresponding to an end of the respective constant-current stage estimated based the second DC resistance; calculating an expected duration of each of the plurality of constant-current stages; calculating a remaining charging time for the charging sequence based on the expected durations; and generating, at the charger, an output using the output device that reflects the remaining charging time.Docket No. P-WO-TN-2024-1123

[0032] The aforementioned example embodiment may include the battery pack including at least one battery cell and the protocol specifying that the charging sequence terminates each of the plurality of constant-current stages upon the battery cell reaching a threshold voltage.

[0033] The aforementioned example embodiment may include the output device comprising a display device.

[0034] The aforementioned example embodiment may include each stage of the plurality of constant-current stages of the charging sequence corresponding to a current drop from a preceding stage of the plurality of constant-current stages.

[0035] The aforementioned example embodiment may include the current drop being a constant amount throughout the charging sequence.

[0036] The foregoing illustrative summary, as well as other exemplary objectives and / or advantages of the disclosure, and the manner in which the same are accomplished, are further explained within the following detailed description and its accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1 shows an example charger according to the present subject matter and an example set of battery packs that can be used with the charger.

[0038] FIG. 2 shows a schematic diagram of an example charger according to the present subject matter coupled with an example battery pack.

[0039] FIG. 3 shows an example diagram with graphs representing an example charging sequence and a battery pack voltage for an example battery pack.

[0040] FIG. 4 shows an example averaged Voc vs. SoC relationship for a set of at least two battery packs.

[0041] FIG. 5 shows an example lookup table for the averaged Voc vs. SoC relationship.

[0042] FIGs. 6A and 6B show example diagrams with a graph representing a voltage and a current signal for determining a direct current resistance upon initial insertion of an example battery pack to an example chargerDocket No. P-WO-TN-2024-1123

[0043] FIGs. 7A and 7B show example diagrams with graphs representing a voltage and a current signal for determining a direct current resistance during a step change in an example charging sequence of an example battery pack.

[0044] FIGs. 8 - 17 show flowcharts of an example method for estimating a remaining time of a charging sequence.

[0045] FIG. 18 shows a table of values of an example process of the present disclosure.

[0046] The components in the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding parts throughout the several views.DETAILED DESCRIPTION

[0047] The present disclosure relates to calculating, by a charger, an estimated remaining charging time until a charging sequence of a battery pack is complete. The present disclosure also relates to calculating, by a charger, an instantaneous state of charge (SoC) of a battery pack and an estimated SoC of a battery pack at a future point in time during a charging sequence. The present disclosure also relates to calculating an SoC based upon a direct current resistance of a battery pack. Disclosed approaches can be used in connection with a charger that is compatible with charging a variety of battery packs having different characteristics (e.g., capacity) that are not known to the charger during the charging sequence. As such, the present subject matter can provide an improved experience for a user when charging a battery pack, by presenting useful status information about SoC and / or remaining charging time regardless of the type of battery pack.

[0048] FIG. 1 shows an example charger 100 according to the present subject matter and an example set of battery packs 200 according to the present subject matter that may be charged using the charger 100. The charger 100 may implement, or be used in combination with, one or more other example battery packs described elsewhere herein. The set of battery packs 200 may include any number of different types of battery pack 201-1 - 201-M. In some implementations, each battery pack 201-1 through battery pack 201-M may be charged by the charger 100, where M=2, 3, 4,....

[0049] The battery packs 201 of the set of battery packs 200 may be used for powering any of a variety of devices (not shown). In some implementations, one or more of the battery packsDocket No. P-WO-TN-2024-1123201 may be configured for providing power to a handheld (or otherwise mobile) piece of equipment. For example, one or more of the battery packs 201 may be compatible for use as a power supply for a power tool.

[0050] Each of the battery packs 201 may have one or more characteristics relating to its energy storage and its ability to provide power. For example, the battery pack 201-1 may have a first capacity and the battery pack 201-M may have a second capacity that is different from (e.g., greater or lesser than) the first capacity. The charger 100 may be designed for charging up to a given target voltage or multiple target voltages. As such, each of the battery packs 201 may be of a type that has that one of the target voltages. The capacity of respective battery packs 201 is not known to the charger 100 beforehand or during the charging sequence. Rather, examples are described below of how the charger 100 may calculate an estimated capacity of the battery pack 201 that is being charged.

[0051] Any of the battery packs 201 may be configured for powering more than one type of equipment. In some implementations, two or more different devices may be configured for using at least one of the battery packs 200 as their power source. For example, the battery pack 201-1 may be used with either of at least two different power tools. Also or instead, two or more of the battery packs 201 may be configured for powering the same type of equipment. For example, each of the battery pack 201-1 and the battery pack 201-M may be used to power the same type of power tool.

[0052] The charger 100 may be configured for charging each of the battery packs 201 when that battery pack 201 is received by / coupled to the charger 100. The charger 100 may be coupled to an alternating current (AC) power source that provides the power for charging the battery pack. For example, the charger 100 may be connected to a grid or any other source of electricity (stationary or mobile) to power a charging sequence. The charger 100 may include circuitry (exemplified below) for conditioning the power from the power source to provide current according to the charging sequence. For example, when the power source provides AC, the charger 100 can convert the AC to direct current (DC) for charging any of the battery packs 201. The charger 100 controls the charging sequence that is being applied to the battery pack 201. In some implementations, the charging sequence can include two or more stages or steps during which different levels of DC (e.g., constant current) are applied to the battery pack 201. ForDocket No. P-WO-TN-2024-1123example, during the charging sequence the charger 100 can control when to change from one stage to another, and / or when to terminate the charging sequence.

[0053] Each of the battery packs 201 may be configured for being mechanically and electrically coupled to the charger 100 for being charged. The battery packs 201 may have different dimensions (e.g., due to having different capacity or operating / rated voltages) and may share a common interface that enables the mechanical and electrical coupling. In some implementations, the common interface may include a rail and groove design that may be used for ensuring that the battery pack 201 may be releasably coupled with the charger 100 by sliding the battery pack 200 into engagement with the housing of the charger 100. At least one rail can be provided on one of the charger 100 or the battery pack 201, and correspondingly at least one groove can be provided on the other one of the charger 100 or the battery pack 201, to facilitate the coupling. The battery pack 201 may include a plurality of battery pack terminals 202, for example, battery pack terminals 202a-202h. The mechanical coupling of any of the battery packs 201 to the charger 100 ensures that the battery pack terminals 202 of the battery pack 201 will be electrically coupled by way of contacting charger terminals 102 of the charger 100 to form an electrical connection. The mechanical coupling of the battery pack 201 to the charger 100 can be secured by way of a locking mechanism (e.g., a latch), or the coupling can be ensured by a friction fit between the respective mating portions of the battery pack 201 and the charger 100, to name just two examples. Whether or not a locking mechanism is used between the battery pack 201 and the charger 100, the battery pack 201 may have a locking mechanism to ensure a mechanical coupling of the battery pack 201 to the device (e.g., a power tool) that is to be powered.

[0054] The charger 100 may include circuitry for controlling the charging sequence when charging any of the battery packs 201 and for generating and displaying one or more outputs that indicate a status and / or progress of the charging sequence / process. The charger 100 may do so based on voltage and current measurements regarding the battery pack 201 and information about the battery packs 201. In some implementations, the charger 100 may be provided information about a relationship between open circuit voltage (Voc) and SoC among the set of battery packs 200. For example, electrical characteristics may be obtained that reflect, for each individual battery pack of the set of battery packs 200, the relationship between its Voc and its SoC. The charger 100 may make use of the information about the relationship in performing anDocket No. P-WO-TN-2024-1123estimation of the remaining charging time for any of the battery packs of the set of battery packs 200.

[0055] The charger 100 may generate and display one or more outputs to a user about a charging state. The charger 100 may include an output device 104 positioned at an outside of the charger housing. Using the output device 104, the charger 100 can display an output 106 that reflects the present SoC of the battery pack 201 that is being charged. In some implementations, the SoC can be defined as a number in the range 0-100% and the output 106 can indicate this number at some level of granularity. For example, when the output device 104 includes a display device (e.g., a liquid crystal display screen or other digital display device) the output 106 can indicate an estimated SoCs using digits and a percent sign. As another example, when the output device 104 includes light-emitting diodes (LEDs) the output 106 can indicate the estimated SoC by the number of LEDs being illuminated.

[0056] Using the output device 104, the charger 100 may display an output 108 that reflects a remaining charging time for the battery pack 200 that is being charged. The charging sequence may be configured to charge the battery pack 200 until it reaches a target SoC. For example, the target SoC can correspond to the battery pack being considered fully charged, or the target SoC can be an SoC lower than fully charged. The estimate of the remaining charging time may be expressed using any unit of time (such as, but not limited to, hours, minutes and / or seconds) and the output 108 may indicate the remaining charging time at some level of granularity. For example, when the output device 104 includes a display device (e.g., a liquid crystal display screen or other digital display device) the output 108 may indicate the remaining charging time using digits and a unit of time. As another example, when the output device 104 includes LEDs the output 108 may indicate the remaining charging time by the number of LEDs that are illuminated.

[0057] FIG. 2 shows an example schematic block diagram of the example charger 100 according to the present subject matter coupled with the example battery pack 201 according to the present subject matter.

[0058] The battery pack 200 may include a set of battery cells 204 of one or more battery cells 204a. In this example, the set 204 includes five battery cells 204a - 204e (also referred to as battery cells Bl - B5) for illustrative purposes only. In other implementations, the set 204 canDocket No. P-WO-TN-2024-1123include a greater or lesser number of battery cells. When the battery pack 200 is coupled to a device the set 204 can deliver stored energy in the form of electricity. The set 204 is rechargeable, and by coupling the battery pack 200 to the charger 100 a charging sequence can be performed. The set 204 can include any type of rechargeable electrochemical battery cells (e.g., lithium-ion battery cells). Multiple instances of the individual cell 204a can be electrically coupled with each other within the set 204 in various ways, including but not limited to using series connections, using parallel connections, or using a combination of series connections and parallel connections.

[0059] A positive terminal of the set of battery cells 204 is here indicated as B+ and a negative terminal of the set of battery cells 204 is indicated as B-. The B+ terminal of the set of battery cells 204 is connected to a positive terminal 202b of the battery pack 200. The positive battery pack terminal 202b may also be referred to as terminal BT2 or the batt+ terminal. The B-terminal is electrically connected to a negative terminal 202a of the battery pack 200 via a switch 206. The negative battery pack terminal 202a may also be referred to as terminal BT1 or the batt- terminal. The batt+ and batt- terminals may also be considered battery pack power terminals as they conduct the charging / discharging current to and from the battery pack 200 to charge or discharge the set of battery cells 204. The battery pack 201 may include circuitry 208 (e.g., a battery management system with a printed circuit board having one or more chips) that may monitor and control the battery pack 200 (e.g., by opening or closing the switch 206). The circuitry 208 may be or include a control module. The battery pack control module may include a processor and / or processing circuitry. The processor may include a microprocessor, a microcontroller or similar control circuitry. Each of the B+ terminal and the B- terminal is also connected to the circuitry 208. The circuitry 208 may have an electrical connection to respective nodes 210a - 210d between battery cells 204a-e of the set 204 of battery cells to allow the voltage of the individual battery cells 204a-e to be measured and monitored by the control module 208. The battery pack may include a set of signal terminals 202c - 202h. The signal terminals generally pass low current signals and may be used to transmit information between the battery pack 200 and the charger 100. The nodes 210a-d may also be connected to respective signal terminals 202e-h of the battery pack 200. Other components of the battery pack 200 that can be connected to respective signal terminals of the battery pack 200 may include a thermistor 212 for indicating battery temperature and an electrical component or circuit 214 (e.g., a resistorDocket No. P-WO-TN-2024-1123and / or capacitor) connected to the circuitry 208 for providing identification of the battery pack 200.

[0060] The charger 100 may include a first (positive) power terminal 102b to form an electric connection with the positive power terminal 202b, a second (negative) power terminal 102a to form an electric connection with the negative power terminal 202a, a first signal terminal 102c to form an electric connection with the first signal terminal 202c of the battery pack 200, and so on. That is, the mechanical coupling of the battery pack 200 with the charger 100 ensures that their respective terminals are placed in contact with each other. The charger 100 may include circuitry 110 (e.g., a control board including one or more chips) to monitor and control the charging performed by the charger 100 using power from a power supply 112. The circuitry 110 may be or include a control module. The control module may include a processor and / or processing circuitry. The processor may include a microprocessor, a microcontroller or similar control circuitry. The control module may include a control protocol that defines a charging sequence. The charger 100 can execute some or all of the protocol to charge the battery pack 200 or any other battery pack with which the charger 100 is compatible. The charger 100 may include instructions for providing status updates about the charging sequence / process. In some implementations, the instructions may cause the charger 100 to estimate the remaining charging time for the battery pack 201 and indicate the estimated time to a user. The estimation can involve determining the present SoC of the battery pack 201 during the charging sequence based on an average SoC-Voc relationship for a group of battery packs (e.g., for the battery packs 200 of FIG. 1). The charger 100 can make an output that indicates the estimated remaining charging time and / or the determined SoC using a display device 104, which is an example of the output device 108 of FIG. 1.

[0061] The set of battery packs 200 may be charged with a predefined profile. The charger 100 may apply a constant current, step charging sequence (sometimes referred to as a charging scheme). The charging sequence may include an initial charge rate (or current) - referred to as a first stage or a first step. The charging sequence, in general, and the first stage of the charging sequence may be based on characteristics of the battery pack 201 and / or the charger 100. The charging current may drop in a fixed amount, for example, in 2A steps when one or more of the battery cells reaches a voltage threshold (VTH), for example, 4.2V or 21V for a battery pack having five battery cells connected in series.Docket No. P-WO-TN-2024-1123

[0062] FIG. 3 shows an example graph with a plot 300 representing an example charging sequence of a battery charger 100 over time and a plot 304 representing an example voltage of a battery pack 201 over during time during the charging sequence 300. The graph presents battery pack voltage (V) on a left-hand vertical axis, charging current (I) on a right-hand vertical axis and time (t) on a horizontal axis.

[0063] The plot 300 shows that the charging sequence is configured to charge the battery pack 201 using a plurality of constant-current stages / steps 302 including steps 302a-302d. After completing one of the constant-current stages 302, the charging sequence makes a current drop down to zero amperes and then to a level of constant current lower than the completed stage / step, unless the charging sequence is completing the lowest level of constant current. In the illustrated example, the charging sequence is shown to have four stages for illustrative purposes only. In the illustrated example, the constant-current stages 302 have a charging current of 8 ampere (A) for a first step 302a, a charging current of 6A for a second step 302b, a charging current of 4A for a third step 302c, and a charging current of 2A for a fourth step 302d, respectively. For example, the difference in charging current between consecutive constant-current stages 302 may be a constant amount throughout the charging sequence (e.g., a 2A drop). More or fewer stages can be used. The charging sequence will terminate one stage when a criterion specified by a protocol is met. In some implementations, the criterion is that any of the cells of the battery pack reaches a threshold voltage. For example, with reference again briefly to FIG. 2, the charger 100 can evaluate the voltages of individual cells using the terminals 102-202 of the respective nodes 210 and cell stack terminals B+, B-. Upon ending a stage, the charge current applied by the charger 100 will drop to zero (0) amperes. After a period of time, for example 6 seconds, the charger will begin the next charging step at the next charging current. During a complete charging sequence, the charger will apply the charging current for a period of time tstep for each step of the charging sequence. In the illustrated example, the charger 100 will apply a charging current of approximately 8 A during step 1 302a for a period of time (tstep i), a charging current of approximately 6A during step 2 302b for a period of time (tstep 2), a charging current of approximately 4A during step 3 302c for a period of time (tstep 3) and a charging current of approximately 2A during step 4 302d for a period of time (tstep 4).

[0064] As noted above, a charging sequence or scheme is determined based upon characteristics of the charger 100 and the battery pack 201. For example, when a battery pack isDocket No. P-WO-TN-2024-1123received by (coupled to) a charger, information regarding the charging capability of the battery pack may be transmitted to / received by the charger. For example, the battery pack charging capability information may indicate a maximum amount of charging current a battery pack is capable of receive during a charging sequence. For example, the battery pack charging capability information may indicate that the battery is capable of receiving a maximum charging current of 8A. Furthermore, the charger may know information regarding the charger charging capability. The charger charging capability information may indicate a maximum amount of charging current the charger is capable of providing during a charging sequence. For example, the charger charging capability information may indicate that the charger is capable of providing a maximum charging current of 8A. Based on these two characteristics, the charger may determine the charging current of the initial or first step / stage in the charging sequence and determine the number of steps / stages of the charging sequence by dividing the charging current of the first step by the amount of the drop in current from one step to the next. In the example illustrated in FIG. 3, the battery pack is capable of receiving a maximum charging current of 8A and the charger is capable of providing a maximum charging current of 8A. In this example, as the maximum charging current of the charger is less than or equal to the maximum charging current of the battery pack, the first step in the charging sequence will be equal to the maximum charging current of the charger. And therefore, the number of steps in the charging sequence will be the maximum charging current of the charger, e.g., 8A, divided by the current drop from one step to the next, e.g., 2A, for a number of steps equal to 4. In another example, the maximum charging current of the battery pack is 10A and the maximum charging current of the charger is 12A. In this example, as the maximum charging current of the charger is greater than the maximum charging current of the battery pack, the first step in the charging sequence will be equal to the maximum charging current of the battery pack. And therefore, the number of steps in the charging sequence will be the maximum charging current of the battery pack, e.g., 10 A, divided by the current drop from one step to the next, e.g., 2A, for a number of steps equal to 5.

[0065] In order to estimate the total time to a full charge (also referred to as “total time to the end of the charging sequence”) (tcno) the charger 100 sums the estimated charge time of each step (tstepn) remaining in the charging sequence.

[0066] EQ 3 tCHG tstep 1 "1“ tstep 2 "1“ tstep 3... tstep NDocket No. P-WO-TN-2024-1123

[0067] where N = the number of steps remaining in the charging scheme / process.

[0068] In order to calculate / determine / estimate tstepn the charger uses EQ. 2 for each step.

[0069] Specifically, the charger uses:

[0070] EQ. 4 ’ tstcp n C X (SoCstcp n, end—SoCstcp n, start ) / Ltep n, [wherein in all steps except the first Step, SoCstep n, start SoCstep n-1, en d]

[0071] As such, for the example charging sequence noted above and as illustrated in FIG. 3, the charger may plug EQ. 4 into EQ. 3 to calculate the total estimated time to a full charge. It should be noted that SoCstart may be the instantaneous SoC (SoCt1·y) determined for a particular calculation. Furthermore, in EQ. 4, C is a capacity of the received battery pack, measured in ampere-hours (Ah). The capacity C may be calculated / determined / estimated as described below.

[0072] EQ. 5: tCHG [C X (SoCstep 1, end — SoCstart) / Istep 1] + [C X (SoCstep 2, end — SoCstep 1, end) / Istep 2] + [C X (SoCstep 3, end—SoCstep 2, end) / Istep 3] + [C X (SoCstep 4, end—SoCstep 3, end) / Istep 4]

[0073] In order to calculate / determine / estimate tcHG the charger 100 must calculate / determine / estimate SoCstart, SoCstep i. end, SoCstep 2. end, SoCstep 3, end, and SoCstep 4, end.

[0074] In general, the state of charge of a battery pack is a function of an open circuit voltage of the battery. As a corollary, the state of charge of a battery cell is a function of an open circuit voltage of the battery cell. In some implementations, a function can be defined that represents the information of a graph 400 of FIG. 4, as discussed in more detail below. For example, the function can be defined so that it takes any Voc value as an input and calculates / determines / estimates a corresponding SoC value as an output. As such, the averaged Voc-SoC relationship illustrated in FIG. 4 may include a function.

[0075] EQ. 6: SoC = f(Voc)

[0076] The various battery packs 201 of the set of battery packs 200 may include various different battery cells in various different configurations. The battery cells themselves, and therefore the battery packs, may have various different relationships between the SoC and the Voc. The relationship between the SoC and the Voc for each battery cell / battery pack of the set of battery packs 200 may be determined. A weighted, averaged of the relationship between the SoC and the Voc for all of the battery cells of the battery packs 201 of the set of battery packsDocket No. P-WO-TN-2024-1123200 may be determined. Such a weighted, averaged relationship for an example set of battery packs 200 may be presented as plot on a graph, as illustrated in FIG. 4 or stored in a look-up table, as illustrated in FIG. 5.

[0077] FIG. 4 shows an example graph 400 representing a weighted, averaged SoC-Voc relationship for the battery cells of an example set of battery packs 200. Voc is indicated at the horizontal axis and may be measured in a unit that indicates voltage (e.g., volt). The SoC is indicated at the vertical axis and here ranges from 0% to 100%.

[0078] The SoC-Voc relationship may be manifested in any of multiple ways. In some implementations, a lookup table may be generated that reflects the information of the graph 400. For example, as illustrated in FIG. 5, an array may be created that includes at least respective pairs of Voc values and SoC values, such that for a given Voc value a corresponding SoC value can be obtained from the lookup table. As such, the averaged SoC-Voc relationship of FIG. 4 may include a lookup table, as represented in FIG. 5.

[0079] As such, in order to calculate / determine / estimate SoC, the charger must calculate / determine / estimate Voc. More particularly, the charger must calculate / determine / estimate a starting / instantaneous open circuit voltage (Voc, start) and an open circuit voltage at the end of each N steps (VOC, step n, end) in the charging sequence.

[0080] An open circuit voltage measurement can be determined from a voltage measurement of a battery pack. The following equation may be used.

[0081] EQ. 7: VM, pack = VOC, pack + ICHGRDC, pack

[0082] In the previous equation, VM, pack is the voltage measured across the charger terminals ch+ / ch-, VOC, pack is a voltage across the charger terminals without the application of a current, ICHG is a current applied to the battery pack and RDC, pack is a direct current (DC) resistance (DCR) of the battery pack upon the application of the current ICHG to the battery pack.

[0083] EQ.8: VOC, pack = VM, pack – ICHGRDC, pack

[0084] In order to determine the open circuit voltage of a battery cell in the battery pack, the open circuit voltage of the battery pack may be divided by the number of cells in the battery pack connected in series.

[0085] EQ. 9: VOC, cell = (VM, pack – ICHGRDC, pack) / ZDocket No. P-WO-TN-2024-1123

[0086] In the previous equation, Z is the number of battery cells in the battery pack connected in series.

[0087] From EQ. 9, in order to calculate / determine / estimate an open circuit voltage the charger must first calculate / determine / estimate the DC resistance of the battery pack / battery cell.

[0088] During a charging sequence where current is being applied to a battery pack, the terminal voltage of the battery pack (batt+ / ch+ - batt- / ch-) can be measured at any time by the charger. However, the terminal voltage (batt+ / ch+ - batt- / ch-) measured while charging is not a good indicator of the present SoC of the battery pack because the measured terminal voltage is influenced by the voltage across the DC resistance of the battery pack. Following is an example of calculating the DC resistance so that the SoC of the battery pack can be determined more accurately.

[0089] When calculating an initial open circuit voltage or an instantaneous open circuit voltage to determine a respective initial state of charge or instantaneous state of charge, it is preferable that the charger calculate / determine / estimate an initial or instantaneous or starting DC resistance (RDC, start), using the following process.

[0090] FIGs. 6A and 6B show graphs 600A, 600B and 602A, 602B, respectively, relating to an example process for calculating a DC resistance for a battery pack upon initial insertion of the battery pack with the charger (the charger initially receiving the battery pack).

[0091] The graph 600A shows current being applied to the battery pack on the vertical axis and time on the horizontal axis. The graph 600B shows the terminal voltage of the battery pack 201 (batt+ / batt-) on the vertical axis and time on the horizontal axis. Before a time tA no current is being applied to the battery pack according to the graph 600A and the graph 600B shows the measured voltage of the battery pack (batt+ / batt-) to be a value Voc. Beginning at the time tA, a current ICHG is applied to the battery pack as shown in the graph 600A, and the graph 600B shows that the voltage of the battery pack begins to increase. At a time tB the graph 600B shows the measured voltage of the battery pack (batt+ / batt-) to be a value VCHG. That is, after an amount of time (At = tB— tA), which can be a predetermined amount of time (e.g., on the order of about one second), the terminal voltage has increased (by an amount AC = VCHG— VREST) as a result of applying the current ICHG to the battery pack. The starting (instantaneous) DC resistance (RDC) can be calculated by:Docket No. P-WO-TN-2024-1123

[0092] EQ. 10: RDC, start = (VCHG, pack – VOC, pack) / ICHG

[0093] That is, EQ. 10 is an example of calculating the starting DC resistance for any battery pack compatible with the charger based on the current ICHG and a difference between the voltage VCHG and the voltage Voc. The starting DC resistance may be calculated before the charging sequence is initiated, or at the beginning of the charging sequence. For example, the current ICHG that is applied according to the graph 600A can be one of multiple constant-current stages of the charging sequence. However, the DC resistance may not remain constant over time. For example, the starting DC resistance may vary with SoC of the battery pack.

[0094] FIG. 6B illustrates an alternate representation of FIG. 6A wherein graph 602A corresponds to graph 600A and graph 602B corresponds to graph 600B.

[0095] In some implementations, the calculation of the starting DC resistance RDC, start according to EQ. 10 can be performed multiple times during the charging sequence (e.g., periodically or at random times or when the SoC has increased by a predefined amount) based on newly measured values of current and voltage. As illustrated in FIGs. 7A and 7B, the starting DC resistance may be calculated during the charging sequence when the charging sequence transitions from one step to the next step. As illustrated in FIG. 3, when the charging sequence transitions from one step to the next step, for example from the third step 302c to the fourth step 302d, the charger stops providing a charging current, e.g., ICHG goes from 4A to 0A. This is an opportune time to calculate the starting DC resistance as the charging sequence is defined to “pause” the charging current - in other words stop providing a charging current.

[0096] Similar to the process illustrated with respect to FIGs. 6A and 6B, in FIG. 7A the graph 700A shows current being applied to the battery pack on the vertical axis and time on the horizontal axis. The graph 700B shows the terminal voltage of the battery pack 201 (batt+ / batt-) on the vertical axis and time on the horizontal axis. Before a time tA a current ICHG is being applied to the battery pack according to the graph 700A and the graph 700B shows the measured voltage of the battery pack (batt+ / batt-) to be a value VCHG. Beginning at the time tA, the current is no longer applied to the battery pack as shown in the graph 700A, and the graph 700B shows that the voltage of the battery pack begins to decrease. At a time tB the graph 700B shows the measured voltage of the battery pack (batt+ / batt-) to be a value Voc. That is, after an amount of time (At = tB— tA), which can be a predetermined amount of time (e.g., on the order of aboutDocket No. P-WO-TN-2024-1123one second), the terminal voltage has decreased (by an amount AV = VCHG— VREST) as a result of removing the current ICHG to the battery pack. The starting (instantaneous) DC resistance (RDC) can be calculated by using equation EQ. 10.

[0097] The charging sequence is defined to transition from a first step to a second step when a measured voltage of one of the battery cells in the stack of battery cells (VM, ceil) reaches a voltage threshold voltage (VTH, ceil). During the charging sequence, the first battery cell in the series-connected string of battery cells or the last cell in the series-connected string of battery cells is most likely to reach the voltage threshold (VTH) first. That is why the charger may use the DC resistance of the first battery cell (RDC, ceil i).

[0098] The state of charge and the open circuit voltage that are to be estimated for the end of each step in the charging sequence (SoCceii, stepn, end and Voc, ceil, stepn. end) may be based upon the assumed measured voltage of the battery cell (VM, ceil) that has reached the voltage threshold (VTH, ceil). And a DC resistance of the battery cell at the end of the step (referred to herein as RDC. end) is preferably used for the calculation of the end of step open circuit voltage (Voc, ceil, stepn, end). The RDC, end may be equal to the DC resistance of a single battery cell (RDC, ceil) plus the DC resistance of a coupled charger terminal (ch+) and battery pack terminal (batt+) through which the charging current ICHG flows (RDC, term) and may be determined somewhat differently than the starting DC resistance (RDC, start) described above.

[0099] EQ. 11 RDC, end = RDC, cell + RDC, term

[0100] Referring to FIG. 2 and the example coupled charger 100 and battery pack 201, under charge, the measured voltage for the first battery cell Bl and / or the last battery cell B5 in the stack of battery cells 204 will be the highest.

[0101] Referring to FIG. 2, the RDC, end for the first cell in the string (Bl) is the DC resistance of the first cell Bl (RDC, cell 1) plus the DC resistance of the coupled positive charger and pack terminal batt+ / ch+ (Rterm i).

[0102] Furthermore, RDC, start may also be expressed as a sum of the DC resistance of the series connected battery cells and the DC resistance of the coupled charger / pack terminals.

[0103] EQ. 12 RDC, start = RDC, ceil i + RDC, ceil 2 + RDC, ceil 3 +... + RDC, ceil z + RDC. term i + RDC, term 2Docket No. P-WO-TN-2024-1123

[0104] where Z = number of battery cells in series and where RDC, term = RDC, term 1 = RDC, term 2 equals the resistance of a coupled charger terminal and battery pack terminal.

[0105] If the resistance of each cell is equal (RDC, cell = RDC, cell 1 = RDC, cell 2 = RDC, cell 3 = . . . RDC, cell Z), then:

[0106] EQ. 13 RDC, start = ZR DC, cell + 2RDC, term

[0107] EQ. 14 RDC, cell = (RDC, start – 2RDC, term) / Z

[0108] EQ. 15 RDC, cell + RDC, term = (RDC, start + (Z – 2)RDC, term) / Z

[0109] EQ. 16 RDC, end = (RDC, start + (Z – 2)Rterm) / Z

[0110] The measured voltage across the charger / pack terminals (batt+ / ch+) and the first cell Bl may be represented by:

[0111] EQ. 17 VM, cell 1 = VOC, cell 1 + ICHG x (RDC, cell 1 + RDC, term)

[0112] Using equation EQ. 11,

[0113] EQ 18 VM, cell 1 = VOC, cell 1 + ICHG x RDC, end

[0114] EQ 19 VOC, cell 1 = VM, cell 1 – ICHG x RDC, end

[0115] Using equation EQ. 16,

[0116] EQ. 20 VOC, cell 1 = VM, cell 1 – ICHG x (RDC, start + (Z – 2)Rterm) / Z

[0117] VM, cell 1, TH is a threshold voltage as measured at ch+ / B1-, at which the charging process transitions from the application of one charge current ICHG, step n to a next charge current ICHG, step n+1

[0118] EQ. 21 VOC, cell 1, step n, end = VM, cell 1, TH – ICHG, step n x (RDC, start + (Z – 2)Rterm) / Z

[0119] EQ 22 SoCcell 1, step n, end = f(VOC, cell 1, step n, end), go to a lookup table

[0120] While the cell resistance will be unique to a particular pack, the charger terminal / pack terminal resistance can be measured and characterized under nominal conditions to provide a more accurate estimate.

[0121] The starting (instantaneous) state of charge may be determined as follows:

[0122] EQ. 23 SoCcell, t1·y = f(VOC, cell, t1·y),Docket No. P-WO-TN-2024-1123

[0123] where VOC, cell, t1·y= (VM, pack, t1·y– Istep 1x RDC, start) / Z.

[0124] And the end of step state of charge, for each step in the charging sequence, may be determined as follows:

[0125] EQ. 24 SoCstep 1, end= f(VOC, cell 1, step 1, end)

[0126] where VOC, cell 1, step 1, end= VM, cell 1, TH– Istep 1x (RDC, start+ (Z-2)Rterm) / Z,

[0127] EQ. 25 SoCstep 2, end= f(VOC, cell 1, step 2, end),

[0128] where Voc. cell 1, step 2, end — M, cell 1, TH—Istep 2 X (RDC, start “I" (Z-2)Rterm) / Z,

[0129] SoCstep 3, end= f(VOC, cell 1, step 3, end)

[0130] where Voc, cell 1, step 3. end — V. cell 1, TH—Istep 3 X (RDC. start “I" (Z-2)Rterm) / Z,

[0131] SoCstep 4, end= f(VOC, cell 1, step 4, end)

[0132] where Voc, cell 1, step 4. end VM. cell 1, TH—Istep 4 X (RDC, start “I" (Z-2)Rterm) / Z.)

[0133] where tl-y is the point in time the estimation to full charge begins (instantaneous), VM, pack, ti y is the voltage across the battery pack (ch+ / ch-) without current flowing at time tl-y or when the SoC and the Voc are determined as a SoCt1·yand VOC, t1·y, and

[0134] where VM, cdi i, TH is a threshold voltage as measured at ch+ / Bl-, at which the charging process transitions from the application of one charge current ICHG, step n to a next charge current ICHG, step n+1, e.g., 4.2V.

[0135] The capacity of a received battery pack may be calculated / determined / estimated, as follows:

[0136] EQ. 26: C = ICHGx (t1·y – t0) / (SoCcell, t1·y– SoCcell, t0)

[0137] In order to calculate / determine / estimate SoCto the charger may first calculate / determine / estimate Voc. pack, to. In order to calculate / determine / estimate Voc, pack, to the charger may measure voltage of the battery pack (VM, pack) when no current is being applied to the battery pack (ICHG = 0), for example, at the moment the battery pack is received / mated with / coupled with the charger (to)Docket No. P-WO-TN-2024-1123

[0138] In order to calculate / determine / estimate Voc, ceil. to the charger may divide VOC, pack, t0by the number of cells connected in a series string in the battery pack.

[0139] In order to calculate / determine / estimate SoCto the charger may use the following:

[0140] SoCcell, to = f(VoC, cell, to)

[0141] The charger may use the lookup table of FIG. 5 to determine SoCto.

[0142] SoCt1·yis the instantaneous state of charge, where tl is a first time period and y is a positive integer. The instantaneous state of charge may be measured at the end of an initial, first time period tl where y = 1 or at the end of a subsequent, first time period tl where y = 2, etc.

[0143] In order to calculate / determine / estimate SoCti-y the charger may use the following:

[0144] SoCt1·y= f(VoC, cell, tl-y),

[0145] The applied current (ICHG) must be constant over the time interval tO to tl -y.

[0146] The charger may calculate / determine / estimate capacity (C) when SoCt1·y- SoCto > 20%.

[0147] The flowcharts of FIGs. 8 - 17 present an example process for estimating a time to a full charge of a charging sequence.

[0148] As shown in FIG. 8, the process begins at step 800. At step 802, the charger 100 may receive a battery pack 200. At step 804, the charger 100 may determine a number of steps N in a charging sequence for the received battery pack 200. At step 806, the charger 100 may calculate an initial DC resistance of the battery pack 200 (RDC, start). As shown in FIG. 9, when calculating the initial DC resistance of the battery pack (RDC, start), at step 902 the charger may use EQ. 10. Once the initial DC resistance of the battery pack (RDC, start) is calculated, at step 904, the charger may return to the flow of FIG. 8. At step 808, the charger 100 may determine an initial state of charge of the battery pack 200 or a battery cell of the battery pack 200 (SoCto). As shown in FIG. 10, when determining the initial state of charge of the battery pack (SoCto), at step 1002 the charger may calculate Voc, pack, to using EQ. 8. At step 1004, the charger 200 may use EQ. 9 to calculate Voc, ceil, to. At step 1006, the charger 200 may use a lookup table to determine SoCceitto. Once the initial state of charge (SoCto) is determined, at step 1008, the charger may return to the flow of FIG. 8. At step 810, the charger 100 may start the charging sequence 300. At step 812,Docket No. P-WO-TN-2024-1123the charger 100 may set a first counter (y) equal to one (1), the counter y being related to the number of first time periods that pass until an instantaneous state of charge exceeds an initial state of charge by a predefined amount (P) and may set a second counter (a) equal to one (1), the counter a being related to a step number in the charging sequence. At step 814, the charger 100 waits the first time period tl. After the first time period has passed, at step 816, the charger 100 may determine an instantaneous state of charge (SoCti-y). As shown in FIG. 11, when determining the instantaneous state of charge SoCti-y, at step 1102, the charger may measure the voltage of the battery pack VM, pack, t1·yat time tl-y. At step 1104, the charger may calculate the open circuit voltage of a battery cell VOC, cell, t1·yat time tl -y. At step 1106, the charger 200 may use a lookup table to determine SoCcell, t1·y. Once the instantaneous state of charge (SoCti-y) is determined, at step 1108, the charger may return to the flow of FIG. 8.

[0149] At step 818, the charger may compare the instantaneous state of charge determined in step 816 to the initial state of charge determined in step 808. As noted above, the charger 100 does not know the capacity of the battery pack 200 when the charger receives the battery pack. And, as the estimation of time to a full charge is based, in part, on the capacity of the battery pack, it is preferred to have a good understanding of the capacity of the battery pack before calculating and displaying the time to full charge to a user. As capacity is determined based, in part, on the difference in SoC at a first time (tO) and a second time (tl) it is preferable to wait until the difference between an initial state of charge and an instantaneous state of charge is greater than a predefined difference (Q) before calculating the capacity and the estimated time to full charge. As such, if the instantaneous state of charge is not greater than the initial state of charge by an amount Q, for example 20, then the charger may increment in step 820 the first counter y by 1 and return to step 814 at which the charger may wait another time period tl. Again, after the time period tl has passed, at step 816, the charger may determine the instantaneous state of charge as noted above. At step 818, the charger may again compare the instantaneous state of charge to the initial state of charge. If the difference is again less than Q, the charger may again repeat steps 820, 814, 816, and 818. As a note, as the counter y is incremented each time the aforementioned loop is repeated, the number resulting from tl y is equal to the time period tl multiplied by the number of time periods that have passed when the instantaneous state of charge is greater than the initial state of charge by the predefined amount Q. For example, if the time period tl is equal to 90 seconds and three time periods tl haveDocket No. P-WO-TN-2024-1123passed before the instantaneous state of charge is greater than the initial state of charge by Q, for example y = 3, thentl y = 270 seconds and SoCt1·ywould be the state of charge at 270 seconds.

[0150] Once the instantaneous state of charge is greater than the initial state of charge by the predefined amount Q, at step 822 the charger may calculate the capacity (C) of the received battery pack. As shown in FIG. 12, when calculating the capacity C, at step 1202, the charger may use EQ. 26 to calculate the capacity C of the received battery pack. Once the capacity C has been calculated, at step 1204, the charger may return to the flow of FIG. 8.

[0151] At step 824, the charger may calculate the end of step DC resistance RDC, end. As shown in FIG. 13, at step 1302, the charger may use EQ. 16 to determine RDC, end. Once the end of step resistance RDC. end has been calculated, at step 1304, the charger may return to the flow of FIG. 8.

[0152] At step 826, the charger may determine the instantaneous step number in the charging sequence. As shown in FIG. 14, at step 1402, the charger may determine if a step change has occurred. The charger may know that a current level has changed from a first level, for example 8 A, to a second level, for example 6A. If a step change has not occurred, then in step 1404, the charger may set a third counter n equal to the second counter a and a fourth counter x equal to the second counter a. As the counter a is set to 1 in the step 812, the first time the process is carried out then the third counter n and the fourth counter x will be set to 1 indicating that the charging sequence is in the first step of the charging sequence. If a step change has occurred, then in step 1406, the charger may increment the second counter a by one. Then, in step 1404, the charger may set the third counter n and the fourth counter x equal to a. Once the step number has been determined, at step 1408, the charger may return to the flow of FIG. 8.

[0153] At step 828, the charger may determine the state of charge at the end of each step in the charging sequence (SoCcell, step n, end). As shown in FIG. 15, in order to determine the state of charge at the end of each step in the charging sequence, in step 1502, the charger may calculate the open circuit voltage at the end of a step in the charging sequence (Voc, cell, stepn, end) using equation 20. Once the open circuit voltage at the end of a step VOC, cell, step n, endis calculated, in step 1504, the charger may determine the state of charge at the end of the step SoCcell, step n, end. Once, the state of charge at the end of the step SoCcell, step n, endis determined, at step 1506, the charger may determine whether a state of charge at the end of every remaining step in theDocket No. P-WO-TN-2024-1123charging sequence has been determined by comparing the third counter n to the total number of steps in the charging sequence N. If the state of charge at the end of all of the steps has not been determined (n < N), then, at step 1508, the third counter n is incremented by 1 and the process returns to step 1502 to calculate the open circuit voltage at the end of the next step and then to step 1504 to determine the state of charge at the end of the next step. Once the state of charge has been determined for all of the remaining steps in the charging sequence (n = N), then at step 1510, the charger may return to the flow of FIG. 8.

[0154] At step 830, the charger may calculate the charging time for each step remaining in the charging sequence. As shown in FIG. 16, at step 1602, the charger may calculate the charging time for the instantaneous step. In this step, the charger may use equation EQ. 4, the capacity C calculated at step 822, the state of charge at the end of the first step (SoCstep i, end) determined at step 828 and the instantaneous state of charge (SoCti-y) determined in step 816. Once the charging time for the first step in the remaining steps of the charging sequence is calculated, at step 1604, the charger may determine whether charging time for every remaining step in the charging sequence has been calculated by comparing the fourth counter x to the total number of steps in the charging sequence N. If the charging time for all of the steps has not been determined (x < N), then, at step 1606, the fourth counter x is incremented by 1 and at step 1608, the charger may calculate the charging time for the next step in the charging sequence. In this step, the charger may use equation EQ. 4, the capacity C calculated at step 822, the state of charge at the end of the next step (SoCstep x, end) determined at step 828 and the state of charge of the previous step (SoCstep x-i, end) determined in step 828. Thereafter, the process returns to step 1604 to determine if the charging time for all of the steps has been calculated. Once the charging time has been calculated for all of the steps in the charging sequence (x = N), then at step 1610, the charger may return to the flow of FIG. 8.

[0155] At step 832, the charger may calculate the remaining time to a full charge (tCHG). As shown in FIG. 17, at step 1702, the charger may use equation EQ. 3 to calculate the remaining time to a full charge. Once the remaining time to a full charge has been calculated, then at step 1704, the charger may return to the flow of FIG. 8.Docket No. P-WO-TN-2024-1123

[0156] While not shown in the flow of FIG. 8, once the remaining time to a full charge for the received battery pack has been calculated, the charger may display the remaining time to a full charge and the instantaneous state of charge on the display 104.

[0157] At step 834, the charger may determine if the received battery pack has been fully charged. If the received battery pack has been fully charged, then the time to full charge tCHGwill equal zero and the process will continue to step 836 and the process will end.

[0158] If the received battery pack is not fully charged, then the time to full charge tCHGwill not equal zero and the process will continue. At step 838, the charger may wait the first time period tl and increment the first counter y. At step 840, the charger may determine if a second time period t2 has expired. If the second time period t2 has expired, then the charger may begin the process for recalculating and updating the time to a full charge of the received battery pack.

[0159] The charger may, at step 842 determine an updated instantaneous state of charge (SoCt1·y), at step 822 calculate an updated capacity C, at step 824 calculate an updated end of step DC resistance (RDC. end), at step 826 determine the step number in the charging sequence, at step 828 determine updated state of charge at the end of each step in the charging sequence (SoCstep n. en d), at step 830 calculate an updated charging time for each of the remaining steps in the charging sequence (tstep x) and at step 832 calculate an updated remaining time to a full charge (tCHG). As noted above, the charger 100 may display the updated remaining time to a full charge and the updated instantaneous state of charge on the display 104.

[0160] If at step 840 the second time period t2 has expired, at step 844, the charger may calculate an updated starting DC resistance (RDC, start). At step 846, the charger may restart the second time period t2. The process may then proceed to step 842.

[0161] The following is an example of calculating a remaining time to a full charge of a received battery pack. In step 802, the charger 100 receives a battery pack 200. In step 804, the charger 100 determines that the received battery pack 200 has five (5) cells connected in series and is capable of receiving an 8 A charging current and the charger 100 is capable of providing an 8A charging current. The charger 100 is configured to implement a current drop of 2A from one step to the next step. As such, the charger 100 determines that there are four steps in the charging sequence (N=4). The charging sequence 302 of FIG. 3 illustrates an example charging sequence having four steps. In step 806, the charger calculates an initial DC resistance RDC. start.Docket No. P-WO-TN-2024-1123The charger 100 measures the voltage of the received battery pack 200, without the application of a charging current (Voc) to be approximately 15.757V. The charger 100 applies a charging current (ICHG) of approximately 8A and measures the voltage of the received battery pack with the application of the charging current (VCHG) to be approximately 16.068V. The charger 100 calculates the initial DC resistance RDC, start to be approximately 38.875mQ.

[0162] In step 808, the charger 100 determines an initial state of charge (SoCto) of the received battery pack 200. The charger 100 may use the measured voltage of the received battery pack 200, without the application of a charging current (Voc) from the previous step as the measured open circuit voltage of the pack (Voc. pack, to). Alternatively, the charger 100 may measure the open circuit voltage of the received battery pack 200 (measuring the voltage across the ch+ / ch- terminals without the application of a charging current) at a time prior to the time used for calculating RDC, start or at a time after the time used for calculating RDC, start. The Voc. pack, to equals 15.757V and therefore, the Voc, ceil, to = 3.151V. Using the lookup table of FIG. 5, the charger 100 may determine the initial state of charge SoCto equals approximately 2.4%.

[0163] In step 810, the charger 100 begins the charging sequence and sets the first counter y = 1 and the second counter a = 1. The charger may have a predetermined first time period (tl) of approximately 100 seconds and a predefined difference between the initial state of charge SoCtO and the instantaneous state of charge SoCtl-y (Q) of 20. In this example, the charger 100 carries out steps 814, 816, 818, and 820 thirteen times before the difference between the instantaneous state of charge SoCti-y and the initial state of charge SoCto is greater than 20. At this point, the first counter y = 13, the elapsed time tl -y = 1300 seconds, the charging current is approximately 8A, the measured voltage of the received battery pack 200 is approximately 18.318V, and the initial DC resistance is approximately 38.875mQ. As such, the Voc. ceil, ti y equals 3.601V.Using the lookup of FIG. 5, the charger 100 may determine the instantaneous state of charge SoCti-y equals approximately 30%.

[0164] At step 822, the charger 100 calculates the capacity of the received battery pack 100, wherein the charging current ICHG equals 8A, the elapsed time equals 1300s, the instantaneous state of charge SoCti-y equals approximately 30% and the initial state of charge SoCto equals approximately 2.4%. As such, the capacity of the received battery pack 200 equals approximately 37,681 Ampere- seconds or approximately 10.47Ampere-hours.Docket No. P-WO-TN-2024-1123

[0165] At step 824, the charger 100 calculates an end of step DC resistance (RDC, end). With RDC, start equal to approximately 38.875mQ, Z equal to 5 and Rtermequal to approximately 10mΩ, RDC, end equals 68.875mQ.

[0166] At step 826, the charger 100 determines that the process is in step 1.

[0167] At step 828, the charger 100 determines that the open circuit voltage at the end of step 1 is approximately 4.090V and the state of charge at the end of step 1 is approximately 91.8%, that the open circuit voltage at the end of step 2 is approximately 4.1 IV and the state of charge at the end of step 2 is approximately 94.9%, that the open circuit voltage at the end of step 3 is approximately 4.145V and the state of charge at the end of step 3 is approximately 97.1%, and that the open circuit voltage at the end of step 4 is approximately 4.172V and the state of charge at the end of step 4 is approximately 99.1%.

[0168] At step 830, the charger 100 calculates the charging time for each charging step in the charging sequence. With capacity equal to approximately 37,681 Ampere-seconds, the initial state of charge equal to approximately 30%, the state of charge at the end of step 1 equal to approximately 91.8%, the state of charge at the end of step 2 equal to approximately 94.9%, the state of charge at the end of step 3 equal to approximately97.1% and the state of charge at the end of step 4 equal to approximately 99.1%, the estimated charging time for step 1 is approximately 2911 seconds, the estimated charging time for step 2 is approximately 195 seconds, the estimated charging time for step 3 is approximately 207 seconds and the estimated charging time for step 4 is approximately 377 seconds.

[0169] At step 832, the charger 100 calculates the remaining time to a full charge as approximately 3690 seconds or approximately 1.026 hours.

[0170] The charger may present on the display 104 “1.026 hours” as the time to a full charge.

[0171] In an alternate embodiment, the step 824 of calculating an end of step DC resistance (RDC, end) may be moved to the step 824 and calculated simultaneously with the calculation of the initial DC resistance (RDC, start) instead of after the calculation of the capacity (C) in step 822.

[0172] The table of FIG. 18 illustrates the calculated / determined / estimated values for the foregoing example.Docket No. P-WO-TN-2024-1123

[0173] In the specification and / or figures, typical embodiments have been disclosed. The present disclosure is not limited to such exemplary embodiments. The use of the term “and / or” includes any and all combinations of one or more of the associated listed items. The figures are schematic representations and so are not necessarily drawn to scale. Unless otherwise noted, specific terms have been used in a generic and descriptive sense and not for purposes of limitation.

[0174] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure. As used in the specification, and in the appended claims, the singular forms “a,” “an,” “the” include plural referents unless the context clearly dictates otherwise. The term “comprising” and variations thereof as used herein is used synonymously with the term “including” and variations thereof and are open, non-limiting terms. The terms “optional” or “optionally” used herein mean that the subsequently described feature, event or circumstance may or may not occur, and that the description includes instances where said feature, event or circumstance occurs and instances where it does not. Ranges may be expressed herein as from "about" one particular value, and / or to "about" another particular value. When such a range is expressed, an aspect includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0175] While certain features of the described implementations have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the scope of the implementations. It should be understood that they have been presented by way of example only, not limitation, and various changes in form and details may be made. Any portion of the apparatus and / or methods described herein may be combined in any combination, except mutually exclusive combinations. The implementations described herein can include various combinations and / or subDocket No. P-WO-TN-2024-1123combinations of the functions, components and / or features of the different implementations described.

[0176] It will be understood that, in the foregoing description, when an element is referred to as being on, connected to, electrically connected to, coupled to, or electrically coupled to another element, it may be directly on, connected or coupled to the other element, or one or more intervening elements may be present. In contrast, when an element is referred to as being directly on, directly connected to or directly coupled to another element, there are no intervening elements present. Although the terms directly on, directly connected to, or directly coupled to may not be used throughout the detailed description, elements that are shown as being directly on, directly connected or directly coupled can be referred to as such. The claims of the application, if any, may be amended to recite exemplary relationships described in the specification or shown in the figures.

[0177] As used in this specification, a singular form may, unless definitely indicating a particular case in terms of the context, include a plural form. Spatially relative terms (e.g., over, above, upper, under, beneath, below, lower, and so forth) are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. In some implementations, the relative terms above and below can, respectively, include vertically above and vertically below. In some implementations, the term adjacent can include laterally adjacent to or horizontally adjacent to.

Claims

Docket No. P-WO-TN-2024-1123CLAIMS1. A method of estimating remaining charging time of a charging sequence for charging a battery pack of a set of at least two battery packs, the charging sequence including a plurality of constant-current stages, the at least two battery packs having different capacities, the method comprising:receiving a battery pack of the set of at least two battery packs;determining a number of constant-current stages in the charging sequence; calculating a first direct current (DC) resistance of the received battery pack; determining an initial state of charge (SoC) of the received battery pack based upon the first DC resistance;beginning the charging sequence;waiting a predefined time period;determining an instantaneous SoC of the received battery pack based upon the first DC resistance;comparing the initial SoC and the instantaneous SoC;in response to the instantaneous SoC being greater than the initial SoC by a predefined amount then calculating a capacity of the received battery pack;calculating a second DC resistance of the received battery pack;determining, for each constant-current stage remaining in the charging sequence, an SoC corresponding to an end of the respective constant-current stage based upon the second DC resistance;calculating an expected duration of each of the constant-current stages remaining in the charging sequence;calculating a remaining charging time for the charging sequence based on the expected duration of each of the constant-current stages remaining in the charging sequence; and generating an output that reflects the remaining charging time.

2. The method of claim 1, wherein determining the initial SoC of the received battery pack is based upon a first open circuit voltage and the first open circuit voltage is calculated using the first DC resistance and a measured battery pack voltage and wherein determining the SoC corresponding to the end of the respective constant-current stage is basedDocket No. P-WO-TN-2024-1123upon a second open circuit voltage and the second open circuit voltage is calculated using the second DC resistance and a threshold voltage.

3. The method of claim 1, further comprising measuring i) a voltage of the received battery pack when a current is not being applied to the battery pack (VOC) and ii) a voltage of the received battery pack when a current (ICHG) is being applied to the battery pack (VCHG); and iii) calculating the first DC resistance of the battery pack based on the applied current ICHG, the voltage VCHGand the voltage VOC.

4. The method of claim 1, further comprising measuring a voltage of the received battery pack when the received battery pack is being charged with a charging current during the charging sequence (VM); andcalculating an open circuit voltage of the received battery pack (VOC) based on the voltage VM, the charging current ICHGand the first DC resistance of the received battery pack.

5. The method of claim 1, wherein determining the instantaneous SoC of the received battery pack is based on the open circuit voltage VOCand an SoC-VOCrelationship of the set of battery packs.

6. The method of claim 5, wherein determining each of the ending SoCs is based on a current of the respective constant-current stage, the second DC resistance, an expected voltage of the received battery pack at the end of the respective constant-current stage, and the SoC-VOCrelationship.

7. The method of claim 1, wherein calculating the capacity of the received battery pack is based on the charging current, a multiple of the predefined time period, and a difference between the instantaneous SoC and the initial SoC.

8. The method of claim 1, wherein calculating each expected duration of the constant-current stages is based on the calculated capacity of the received battery pack, the current of the respective constant-current stage, and a difference between the ending SoCDocket No. P-WO-TN-2024-1123of the respective constant-current stage and a starting SoC of the respective constantcurrent stage.

9. The method of claim 3, wherein the voltage VCHGis measured at a predefined time after the voltage VOCis measured.

10. The method of claim 3, wherein the current with which the battery pack is being charged when the voltage VCHGis measured is a constant current of one of the plurality of constant-current stages of the charging sequence.

11. The method of claim 1, further comprising updating the second DC resistance to an updated second DC resistance during the charging sequence.

12. The method of claim 11, wherein updating the second DC resistance comprises performing determining a new voltage difference for the battery pack during the charging sequence and calculating the updated second DC resistance based on the new voltage difference and a current associated with the new voltage difference.

13. The method of claim 1, wherein a lookup table represents the SoC-VOCrelationship and wherein estimating the ending SoCs based in part on the SoC-VOCrelationship comprises obtaining the ending SoCs from the lookup table.

14. The method of claim 1, wherein a function represents the SoC-VOCrelationship, and wherein estimating the ending SoCs based in part on the SoC-VOCrelationship comprises calculating the ending SoCs using the function.

15. The method of claim 1, wherein the expected voltage of the battery pack at the end of the respective constant-current stage is a common expected voltage in each of the plurality of constant-current stages.

16. The method of claim 15, wherein the battery pack includes a plurality of batteryDocket No. P-WO-TN-2024-1123cells and wherein the common expected voltage is based on a threshold voltage of the battery cells.

17. The method of claim 1, wherein for each constant-current stage of the plurality of constant-current stages except an earliest constant-current stage thereof, the starting SoC of the constant-current stage is equal to the ending SoC of a preceding constant-current stage.

18. The method of claim 17, wherein a starting SoC of the earliest constant-current stage is the instantaneous SoC.

19. The method of claim 1, further comprising:continuously performing voltage measurements during the charging sequence to obtain updated voltage measurements;continuously calculating, during the charging sequence, the remaining charging time based in part on the updated voltage measurements and the charging sequence, to obtain updated remaining charging times; andcontinuously updating, during the charging sequence, the output to reflect the updated remaining charging times.

20. The method of claim 19, further comprising:continuously calculating, during the charging sequence, updated SoCs for the battery pack based in part on the updated voltage measurements and the charging sequence; and continuously updating, during the charging sequence, the output to reflect also the updated SoCs.

21. A charger comprising:terminals configured to be coupled to battery terminals of a received battery pack for charging the received battery pack, wherein the charger is compatible with each of multiple types of battery packs having different capacities;a power source to provide at least constant current to the terminals during a charging sequence;Docket No. P-WO-TN-2024-1123an output device; andcircuitry comprising:a protocol defining the charging sequence; andinstructions that when executed cause the charger to perform operations comprising:calculating a first direct current (DC) resistance of the received battery pack;determining an initial state of charge (SoC) of the received battery pack based on the first DC resistance;when the received battery pack has been charged with the charging current for a length of time, determining an instantaneous SoC of the received battery pack based on the first DC resistance;comparing the instantaneous SoC to the first initial SoC and when the instantaneous SoC is greater than the initial SoC by a predefined amount calculating a capacity of the received battery pack;calculating a second DC resistance of the received battery pack; determining, for each of a plurality of constant-current stages of the charging sequence, an SoC of the received battery pack corresponding to an end of the respective constant-current stage, each SoC of the received battery pack corresponding to an end of the respective constant-current stage estimated based the second DC resistance;calculating an expected duration of each of the plurality of constantcurrent stages;calculating a remaining charging time for the charging sequence based on the expected durations; andgenerating, at the charger, an output using the output device that reflects the remaining charging time.

22. The charger of claim 21, wherein the operation of determining the initial SoC of the received battery pack is based upon a first open circuit voltage and the first open circuit voltage is calculated using the first DC resistance and a measured battery pack voltage andDocket No. P-WO-TN-2024-1123wherein the operation of determining the SoC corresponding to the end of the respective constant-current stage is based upon a second open circuit voltage and the second open circuit voltage is calculated using the second DC resistance and a threshold voltage.

23. The charger of claim 21, wherein the battery pack includes at least one battery cell and wherein the protocol specifies that the charging sequence terminates each of the plurality of constant-current stages upon the battery cell reaching a threshold voltage.

24. The charger of claim 21, wherein the output device comprises a display device.

25. The charger of claim 21, wherein each stage of the plurality of constant-current stages of the charging sequence corresponds to a current drop from a preceding stage of the plurality of constant-current stages.

26. The charger of claim 25, wherein the current drop is a constant amount throughout the charging sequence.

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