WO2018130020A1

WO2018130020A1 - Power supply methods and apparatus

Info

Publication number: WO2018130020A1
Application number: PCT/CN2017/113428
Authority: WO
Inventors: Kwok Kit Patrick Lee
Original assignee: Gp Batteries International Limited
Priority date: 2017-01-13
Filing date: 2017-11-28
Publication date: 2018-07-19

Abstract

A method of supplying battery power from a battery assembly, the battery assembly comprising a first plurality of N battery cells, wherein the method comprises a controller to select a second plurality of M battery cells from said first plurality of battery cells to form a battery output group and an output connection to facilitate power output from said battery assembly during a power output process, the second plurality of battery cells consisting of a number of battery cells lesser than the number of battery cells forming the battery assembly and N, M being integers. The controller is to select different battery cells of said battery assembly to form different battery output groups during the power output process to facilitate more equalized or more even total discharge time contribution due to the different battery cells, the total discharge time of a battery cell being a sum of all the specific discharge time intervals due to that battery cell.

Description

POWER SUPPLY METHODS AND APPARATUS

Field

The present disclosure relates to power supply methods and apparatus, and more particularly to methods and apparatus of supplying power from a power pack comprising a plurality of battery cells connectible in series.

Disclosure

A method of supplying battery power from a battery assembly is disclosed, the battery assembly comprising a first plurality of battery cells to form a portable power supply apparatus such as a power pack or a power bank. The method comprises a controller to select a second plurality of battery cells from said first plurality of battery cells to form a battery output group and an output connection to facilitate power output from said battery assembly, the second plurality of battery cells consisting of a number of battery cells lesser than the number of battery cells forming the battery assembly. The controller is to select combinations of battery cells from said battery assembly to form different battery output groups according to connection history of the battery cells and/or operational conditions of the battery cells so that battery output groups forming a sequence of power supply connections consist of different combinations of battery cells selected from said battery assembly. Connection history herein means a history of whether a battery cell was connected for discharging in the immediately past last discharging connection, was connected for discharging in a discharging connection immediately before that last discharging connection, etc.

In some embodiments, the controller is to select the second plurality of battery cells such that an output battery group forming a first battery output group to facilitate a first power supply connection comprises at least one battery of the battery assembly which is not present in an output battery group forming a last battery output group of a last power supply connection, the last power supply connection being an output connection preceding or immediately preceding the first output connection.

A method of outputting power from a battery assembly, the battery assembly having an output voltage and comprising one battery cell or a plurality of battery cells in series and/or parallel connection is disclosed. The method comprises a controller monitoring the output voltage of the battery assembly and operating a current limitation circuitry to reduce battery output current when the output voltage of the battery assembly falls to an output voltage threshold, whereby the circuitry voltage drop across the battery assembly and the battery connection circuitry is reduced.

A power supply apparatus comprising a battery assembly and a controller arranged to operate a method according to the present disclosure is disclosed.

The battery assembly comprises a first plurality of battery cells and the apparatus comprising a switching circuitry. The switching circuitry is operable to connect said first plurality of battery cells in series or to selective connect a second plurality of battery cells selected from said first plurality of battery cells in series, said second plurality being lesser than said first plurality.

In example embodiments, the switching circuitry comprises a plurality of series connected sections and each section comprises a connection branch comprising a connection switch in series a battery cell and a bypassing branch comprising a bypassing switch, the bypassing branch being in parallel with the connection branch, and wherein the connection branch and the bypassing branch are to alternately operate to facilitate selection and deselection of a battery cell to form a battery output group.

In example embodiments, the power supply apparatus is a power pack in the form of a portable power bank.

The power pack may comprise a plurality of alkaline, carbon-zinc, NiMH battery cells, or other battery cells, each having a maximum terminal voltage of between 1.4V and 1.6V.

Figures

The present disclosure will be described by way of non-limiting example and with reference to the accompanying Figures, in which,

Figure 1 is a schematic diagram showing an example power supply apparatus according to the present disclosure,

Figure 2 is an enlarged view showing the example battery cells and the example battery connection circuitry of the example power supply apparatus of Figure 1,

Figure 3 shows an example circuit arrangement comprising an example MCU, the example battery connection circuitry, and example peripheral circuit devices,

Figure 4 shows an example battery discharge group sequence,

Figures 4A shows schematically example cyclical battery discharge group combinations,

Figure 4B shows an example cyclical discharging sequence of the battery discharge groups of Figure 4A,

Figure 4C depicts an example discharging group with an available battery is exhausted,

Figure 5 is a schematic diagram depicting an example circuit arrangement according to another aspect of the present disclosure,

Figure 5A is a diagram depicting relationship between Vo, lo, lmin and lmax according to the present disclosure, and

Figure 5B is depicting relationship between Vo, lo, lmin and lmax according to a specific example of the present disclosure.

Description

A power supply apparatus 100 comprises battery connection circuitry, a plurality of battery cells connected to the battery connection circuit, a controller such as a microcontroller ( “MCU” ) and a power management arrangement, as depicted in Figures 1 and 2.

The battery connection circuitry comprises a plurality of battery connection circuits 112 and the battery connection circuits are connected in series to form a switchable battery network 110. Each battery connection circuit 112 has a first circuit end and a second circuit end defining circuit ends of the battery connection circuit and comprises a first circuit branch and a second circuit branch which are connected in parallel across the first circuit end and the second circuit end.

The first circuit branch comprises a set of battery connection terminals (that is, positive and negative connection terminals) for making electrical connection with the power terminals, that is, positive and negative terminals of a battery, a battery having its battery terminals in connection with the set of battery connection terminals, and a first switch Si which is in series connection with the battery connection terminals or the battery. When the first switch Si is closed, the terminal voltage of the battery will appear across the first circuit branch. When the first switch Si is open, the first circuit branch will become a very high impedance path or a non-electrically conductive path.

The second circuit branch comprises a second switch Pi which is in series connection with a very low impedance conductive path. When the second switch Pi is closed, the second circuit branch will become a very low impedance conductive path. When the second switch Pi is open, the second circuit branch will become a very high impedance path or a non-electrically conductive path.

The first switch Si and the second switch Pi are arranged to operate in an alternative manner so that when one switch is open or off, the other is closed or on, and vice versa. In some operational embodiments, the first switch Si and the second switch Pi are both open, for example, on reset, update or routine inspection operations.

When the first switch Si is closed and the second switch Pi is open, the first circuit branch is a dominant circuit branch and the electrical properties of the first circuit branch will become the electrical properties of the battery connection circuit. When the first circuit branch is dominant, the electrical properties of the first circuit branch or the battery connection circuit will be the electrical properties of the connected battery.

When the first switch Si is open and the second switch Pi is closed, the second circuit branch will become a dominant circuit branch and the electrical properties of the second circuit branch will become the electrical properties of the battery connection circuit. When the second circuit branch is dominant, the electrical properties of the second circuit branch or the battery connection circuit will become the electrical properties of the closed second switch Pi. Since a closed second switch Pi has a very low impedance across its terminals, the battery connection circuit in this situation will become a very low impedance conductive path, and to operate as an electrically shunting path or an electrically bypassing path bypassing the electrical properties or effects of the first circuit branch. During operations, each of the first switch Si functions as a battery switch and each of the second switch Pi functions as a bypassing switch.

The battery switches Si and the bypassing switches Pi are electronic power switches, for example, electronic power switches which can operate at a switching frequency of 0.5Hz to 10Hz or above. In some embodiments, higher speed electronic power switches which can operate at a higher switching frequency of, for example at 5kHz, 10kHz, 100kHz, 1 MHz or above may be used. Power MOSFET switches, IGBT switches, BJT switches, etc. are example electronic switches which are suitable for the present applications. In some embodiments, the switches Si and Pi are high speed electro-mechanical switches such as relays or other appropriate switches such as hybrid switches without loss of generality.

The switchable battery network 110 is connected to the microcontroller 120 and the power management arrangement 130.

The switchable battery network 110 is connected to the microcontroller 120 so that battery conditions, and more specifically electrical conditions of the battery cells, can be individually monitored and/or collectively monitored as a battery assembly.

Referring to Figure 3, the example battery connection circuitry comprises an example plurality of four battery connection circuits 112. The positive battery connection terminal is electrically connected to the first circuit end of the first circuit branch by the switch Si, the negative battery connection terminal is electrically connected to the second circuit end of the first circuit branch, and the positive battery connection terminal of the first circuit branch is electrically connected to a voltage sensing port ADi of the microcontroller 120. As the positive battery connection terminal is connected in series with the switch Si, the positive battery terminal can be connected to or disconnected from the first circuit end of the first circuit branch by switching operations of the switch Si. The example voltage sensing port ADi of the microcontroller 120 is an analog-to-digital input port 120.

Switching control terminals of the switches Si and Pi are connected to the microcontroller 120 so that the microcontroller 120 can send control signals to operate the switches Si and Pi. More specifically, the control terminals of the switches Si and Pi are electrically connected to a control port OPi of the microcontroller 120 and the microcontroller 120 can send control signals to turn on or turn off the switches Si and Pi alternately. Referring to Figure 3, the control terminal of the switch Si is directly connected to the control port OPi of the microcontroller 120 and the control terminal of the switch Pi is connected to the control port OPi of the microcontroller 120 via a serially connected reversal device so that the control signal received at the control terminal of the switch Si and is opposite or has an opposite switching effect to that received at the control terminal of the switch Pi to facilitate alternative operations of the switches Pi and Si.

The particular battery connection circuit or circuits 112 which is or are to contribute actively to the electrical properties of the switchable battery network 110 can be selected by operations of the switches Pi and Si,

For example, when switch Si is on and switch Pi is off, the battery connection circuits 112i is an actively contributing battery connection circuit. Alternatively, when switch Si is off and switch Pi is on, the battery connection circuits 112i is a non-actively contributing or bypassed battery connection circuit.

For example, when all the battery connection circuits 112 are to be actively contributing, all the Pi will be off and all the Si will be on. On the other hand, when three of the battery connection circuits 112 are to be actively contributing, the switches Si of the three actively contributing battery connection circuits 112 will be on and the Si of the remaining battery connection circuits 112 will be off. Likewise, when two of the battery connection circuits 112 are to be actively contributing, the switches Si of the two actively contributing battery connection circuits 112 will be on and the Si of the remaining battery connection circuits 112 will be off without loss of generality.

The voltage of a selected individual battery (Cell i) or a group of selected battery cells comprising a plurality of selected battery cells of the battery connection circuit 112 can be determined, measured or monitored by selective switching of the bypassing switches Pi and battery switches Si.

For example, the voltage of a selected battery Cell i of a battery connection circuit 112i would be the voltage appearing at ADi when the battery switch Si is off (with the bypassing switch Pi on or off) to isolate the battery from other battery cells and the bypassing switches P of all the other or remaining battery connection circuits 112 are on. When all the bypassing switches P are on and all the battery switches Si are off, the voltage appearing at an input port ADi corresponds to the voltage of the individual battery cells connected to that input port ADi.

For example, when battery switch S1 is off and the bypassing switches P of all the battery connection circuits 112 or all the downstream battery connection circuits 112 are on, the voltage reading at AD1 will be that of cell 1. A downstream battery connection circuit 112 herein means one which is connected to the negative battery connection terminal of an upstream battery connection circuit 112. Likewise, when the bypassing switches P of all the battery connection circuits 112 are all on and each one of the battery cells connected to the battery connection circuits 112 are isolated, the voltage appearing at each input port ADi would be the voltage of the battery cell i connected to that particular input port, that is, the voltage reading at AD2 will be that of cell 2, the voltage reading at AD3 will be that of cell 3, and the voltage reading at AD4 will be that of cell 4. In this way, the open circuit voltage of the individual cells can be determined.

In general, when a battery switch Si is off and the bypassing switches P of all the downstream battery connection circuits 112 are on, the voltage appearing at the input port ADi would be the voltage of the battery cell i, and the switching condition of the upstream bypassing switch or switches is usually of no significance.

Alternatively, the voltage of celli can be determined while on load, that is, under closed circuit or loaded conditions. For example, when all the bypassing switches P_i are off and all the battery switches S_i are on, the closed-circuit voltage V_cell i of an individual battery Cell i would be equal to V_i -V_i+1 for i = 1, 2, 3, ..., N -1 and V_i for i = N, where V_i is the voltage at the voltage sensing port AD_i of the MCU which is associated with battery Cell i. For example, the voltage of battery Cell 1 would be equal to V₁ -V₂, the voltage of battery Cell 2 would be equal to V₂ -V₃, the voltage of battery Cell 3 would be equal to V₃ -V₄, and the voltage of battery Cell 4 is V₄. The voltage of the battery assembly comprising all the battery cells of the battery assembly is equal to V₁.

In some operational embodiments, an active battery group consists of a lesser plurality of battery cells than the N battery cells forming the battery assembly to form a selected battery group, and the closed-circuit voltages of the individual battery cells forming the selected battery group or the voltage of the entire selected battery group can be measured. An active battery group herein is one which contributes to the supply of current to the load during an operation cycle. For example, a selected active battery group having one battery lesser than the total number of battery cells forming the battery assembly, with battery cell j bypassed, where j can be any one of 1, 2, 3, ..., N, the voltage V_cell i of the individual battery cell i would be V_cell i = V_i -V_i+1 , where i ≠ j and i + 1 ≠ j and i ＜ N , V_cell i = V_i -V_j+1 where i + 1 = j and i ＜ N , and V_cell i = V_N where i = N. The voltage of the selected active battery group V_group would be V₁ for j ≠ 1 and would be V₂ for j = 1.

In some embodiments, a selected active battery group has more than one battery lesser than the total number of battery cells forming the battery assembly without loss of generality.

Therefore, the example battery connection circuits 112 provides exceptional flexibility in facilitating voltage measurements of a selected battery, selected battery cells or selected battery groups.

It is noted that the terminal voltage of a battery decreases on discharging. For example, a NiMH battery has a terminal voltage of about 1.4 volt when fully charged and the terminal voltage will gradually decease to about 1 volt when fully discharged.

Modern day electronic appliances are typically configured to operate with a DC (direct current) power supply of a prescribed voltage. For example, many modern day electronic appliances such as smart phones, WiFi equipment, storage devices, etc., are adapted for DC operations, and many modern day electronic appliances are operable with a USB power source, whether as a main or supplemental power supply. A typical USB power source has a typical standard output voltage which is currently set at 5V. A typical USB power supply typically comprises a DC-DC power converter which is to convert battery power of an input voltage to the output voltage. The DC-DC power converter may comprise an up-converter or a ‘boost converter’ to up-convert a lower voltage to the standard output voltage, a down-converter or a ‘buck converter’ which is to down-convert a higher voltage to the standard output voltage, or both an up-converter and a down converter. A typical up-converter having a 5V rated output requires a typical voltage input of about 2V (minimum) to 4.8V (maximum) to be operable. An example power converter for use in the present example may be one having a minimum input voltage of 2.4V.

An example power supply appliance according to the present disclosure comprises a power supply apparatus 100 and a main portable housing which cooperate to form a portable power bank. The example power supply apparatus 100 comprises an example plurality of four NiMH battery cells connected to the battery connection circuit and a power management arrangement comprising a boost converter. A NiMH battery is known to have a terminal voltage of about 1.4V when fully charged and the terminal voltage will gradually decrease to a critical or a drained voltage of 1.0V due to discharge.

When the four NiMH battery cells connected to the battery connection circuitry are fully charged and in good conditions, the total available voltage of the battery assembly consisting of four battery cells will be at 5.6V due to the serial connection of the four battery connection circuits 112 and this total available voltage is higher than the maximum input voltage of 4.8V of the up-converter. When the total available voltage of the four battery cells drops to the maximum allowable input voltage of the power converter, i.e., 4.8V, the power converter will be operable with the power of the four NiMH battery cells.

In embodiments where the battery assembly consists of alkaline battery cells, the maximum voltage of each battery cell would be 1.6V and a battery assembly consisting of four alkaline battery cells would have a maximum battery assembly voltage of 6.4V.

In either embodiment, a plurality of one or two battery cells less than the total number of the battery cells forming the fully charged or brand new battery assembly would be sufficient to drive the power converter.

To facilitate operation of the power converter when the total available voltage of all the battery cells connected to the battery connection circuitry is higher than the maximum operation voltage of the power converter, the microcontroller is to execute stored instructions to select a plurality of battery cells among the available battery cells to form selected battery discharge groups for alternate or alternative discharging, at least initially when the total available voltage exceeds the maximum operation voltage.

In example embodiments, the microcontroller is to execute stored instructions to select three battery cells among the four available battery cells to form selective discharge groups, provided that the total voltage of the selected battery cells is within the operational input voltage of the power converter, which is between 2V-4.8V in the present case.

Initially, and when all the available battery cells are fully charged and in good conditions, each battery will be at its maximum voltage, which is 1.4v for a fully charged NiMH battery or 1.6V in the example case of a brand new alkaline battery, and any three of the four battery cells when connected in series will have the suitable operational input voltage of the power converter. Under these circumstances, the microcontroller will execute stored instructions to form battery discharge group C1 during time interval t1, C2 during time interval t2, C3 during time interval t3, C4 during time interval t4, and then repeat the discharging sequence with C1 during time interval t5, C2 during time interval t6, C3 during time interval t7, C4 during time interval t8, and the discharge cycles are to repeat, as depicted in Figures 4A and 4B, where each of the battery discharge group consists of three battery cells selected from the four battery cells forming the battery assembly and each aforesaid time interval is a discharge time interval and the discharge time intervals are non-overlapping, continuous and occur in sequence such that a discharge time interval designated with a higher discharge time interval number occurs after one designated by a lower discharge time interval number as a convenient example. The discharge time intervals t1, t2, t3, ..., ti, ..., continues to a final discharge time interval t_final when the controller ends a power output process, and the total discharging duration time Td of a power output process is the duration from beginning to end of the power output process, and controlled by operation of the controller. The total discharging duration time Td of a power output process is equal to the sum of the interval time of all the discharging discharge time intervals from t1 to t_final when the controller ends discharging at the end of the discharge time interval t_final. discharge time interval

In example discharge battery group arrangements, the example battery group C1 consists of battery cells Cell 2, Cell 3 and Cell 3, the example battery group C2 consists of battery cells Cell 1, Cell 3 and Cell 4, the example battery group C3 consists of battery cells Cell 1, Cell 2 and Cell 4, and the example battery group C4 consists of battery cells Cell 1, Cell 2 and Cell 3. In this example, one battery cell in a last group will be replaced by a new battery unused in the last group to form a new battery group.

In this example, the discharging follows a cyclical order of C1, C2, C3, C4, and repeat until end of the power output process, as depicted in Figure 4A.

In other example discharge arrangements, the discharging may follow the cyclical order of C1, C3, C4, C2 and repeat until end of the power output process.

In yet other example discharge arrangements, the discharging may follow the cyclical order of C2, C4, C1, C3 and repeat of the power output process.

In the above examples, the discharge sequence will repeat after each group discharge cycle time Tc, where Tc is equal to t₁ + t₂ + t₃ + t₄ = t₅ + t₆ + t₇ + t₈.

In general, the number of available battery discharge groups that can be selected is determined according to the combination

that is to select M battery cells from N battery cells, where N is the maximum number of available battery cells of sufficiently good condition and N is the number of battery cells required to supply the operation power.

When there are more battery cells available than battery cells required to meet the power supply requirements, that is N＞M, consecutive battery discharge groups will be formed from non-identical members, with overlapping battery members.

In some embodiments with N=4 and M=3, the battery cells forming the different battery output groups may be selected according to the connection history of the battery cells and the sequential order of the discharge group remains the same in each cycle. An example discharge cycle with fixed sequential manner is shown below (using the same battery cell numbering) or equivalent:

In some embodiments with N=4 and M=3, the battery cells forming the different battery output groups may be selected according to the connection history of the battery cells and the sequential order of the discharge group is selected at random within a cycle. An example discharge cycle with non-sequential manner is shown below (using the same battery cell numbering) or equivalent:

The batteries may be selected in a cyclical and non-sequential manner below:

Alternatively, and/or in combination, the batteries may be selected in a cyclical, non-sequential and non-repeat manner below:

Further, alternatively, and/or in combination, the batteries may be selected in a cyclical, non-sequential and repeat and non-repeat manner below:

In the above, the battery groups C1, C2, C3, C4 have the same battery cell composition as that of Figure 4A and the discharge time interval, ti, where i=1, 2, 3, 4, 5, ..., has the same meaning.

The above are non-exhaustive examples demonstrating selection of battery groups which would achieve battery discharging in a more even or balanced manner in the long run so that the number of discharging cycles undertaken or performed by each available battery cell is substantially the same.

In some embodiments with N=4 and M=3, the battery cells forming the different battery output groups may be selected according to the connection history of the battery cells and the discharge group is selected without sequence or at random. In an example discharge cycle with random manner, each discharge group have an equal probability to be selected and the frequency of occurrence of each discharge group remains the same in a long run.

When the number of battery cells available is substantially larger than the number of battery cells required, consecutive battery discharge groups may consist of non-overlapping battery members without loss of generality.

In the example of Figure 1, N is larger than M by 1 and this provides a good balance in performance, costs, size and resiliency. In other examples, N may be larger than M by more than 1 without loss of generality.

The discharge time interval ti of each selected battery group may be scheduled or set to be tens or hundreds of milliseconds to facilitate stable operations of the power converter, for example, 10ms, 20ms, 30ms, 40ms, 50ms, 60ms, 70ms, 80ms, 90ms, 100ms, 150ms, 200ms, 250ms, 300ms, 350ms, 400ms, 450ms, 500ms, 550ms, etc. or any value or range or ranges or values selected by combination of any of the aforesaid values or ranges. In some embodiments, the discharge time interval of each selected battery group is scheduled or set to be 1s, 2s, 5s, 10s, 20s, 30s or any value or range or ranges or values selected by combination of any of the aforesaid values or ranges as a convenient example. The group discharge cycle time T would equal

In some embodiments, the discharge time intervals are set to be uniform. In some embodiments, the discharge time intervals are non-uniform, for example to inversely correlate with the rate of discharge or other discharge schemes.

During operations, the MCU will monitor the individual battery cells whilst or prior to forming the battery discharge groups. For example, a battery will be discarded or bypassed from forming an instantaneous battery discharge group if the battery terminal voltage of a battery which is scheduled to be a member or a new member of a next battery discharge group to be formed has fallen to an undesirable level, for example, when the battery falls to a critical or drained voltage level corresponding to a drained, exhausted or unusable battery or battery state.

Before forming a selected active battery group, the MCU will determine the closed-circuit voltage of each battery cell which is a scheduled candidate of the selected active battery group to ensure that the closed-circuit voltage of the battery cell is above a threshold voltage corresponding to the critical or drained voltage level.

When one battery cell of the battery assembly is found to be unfit for operation, for example, when the battery terminal voltage falls to or below a critical or drained voltage level, the unfit battery will be bypassed, and N-1 battery cells will remain for selection in which case the number of battery group combination will become

Where the number of available battery cells in the battery assembly falls to a number which is just sufficient to operate the load, the MCU will stop changing the combination of battery cells and stay with a working combination of a selected battery group until one of the battery cell in the last working selected battery group falls to the critical or drained voltage level.

In some embodiments, the MCU may execute stored instructions to identify a battery cell having a terminal voltage at or above a threshold selection voltage if, in the meantime, the battery terminal voltage of a battery cell which is scheduled to be a member or a new member of a next battery discharge group to be formed has fallen to below the threshold selection voltage level.

In example embodiments where the power converter requires an operational voltage which is higher than the aggregate of the total voltages of the next set of battery cells scheduled to form a battery discharge group, for example, a power converter requiring an operation voltage of say 3.2V, the MCU will look for a combination of battery cells that meet the operation voltage or to select a new battery having the highest terminal voltage as a next battery without loss of generality. A new battery herein means a battery which is not in a current battery discharge group and an old battery herein means a battery which is a member of a current battery discharge group as a convenient short hand.

When a discharge operation has completed, that is, when an appliance taking power from the power supply apparatus is switched off or disconnected, the MCU may reset the system so that the next discharge action will commence from initiation, that is C1, from the last stopped combination, or other combination to restart without loss of generality.

When only a sufficient number M of battery cells are in good condition and available for forming a battery discharge group, the M battery cells will be used to form the only available battery discharge group without loss of generality. For example, when battery cell 4 is exhausted,

battery cells

1, 2 and 3 are the remaining battery cells that are available in good conditions and the battery discharge group will consist only the

battery cells

1, 2 and 3, as depicted in Figure 4C, until the next recharge.

While a boost converter has been used as an example, it should be understood that the power converter may be a buck converter, or one comprising both boost and buck converters and the example operational voltages are provided solely as a convenient example without loss of generality. Whether a buck converter or a boost converter is required would depend on the voltage or the instantaneous voltage of a selected battery group supplying a load current without loss of generality.

Referring to Figure 5, an output terminal of a battery assembly is connected to Vin of a power converter. The terminal voltage of the battery assembly is the input voltage to the power convertor and converted power is available at an output terminal Vo of the power converter.

When the battery assembly consists of fully charged battery cells, the input voltage to the power convertor is at maximum and the power converter operates to boost voltage of the battery assembly to output a boosted voltage.

When the terminal voltage of the battery assembly falls as a result of discharging, the circuitry voltage drop, which is the total circuitry voltage drop across the battery connection circuitry and the battery assembly, due to flow of battery discharge current through the battery connection circuitry and the discharging battery cells becomes significant.

In example embodiments, the power converter is a boost converter having a rated voltage Vo output of 5V, a rated output current lo of 1A, a minimum required input voltage of 2V to operate, and a conversion efficiency of 90%. When the input voltage to the power converter falls to the minimum voltage of 2V, the input current (or the output current of the battery assembly) will be at 2.78A, i.e., ( (5V x 1A) /90%/2V) .

In general terms, the relationship can be described by:

I_{in_converter} = (V_{out_converter}×I_{out_converter}) ÷ conversion efficiency ÷ V_{min_required}

For example, where the active battery assembly is formed by series connection of three AA or AAA sized NiMH battery cells each having an example circuitry resistance of 0.5 ohm, each of the battery cells would need to have a minimum terminal voltage of 1.13V in order to meet the minimum voltage requirement, i.e., 2V, at the power converter input after accounting for the circuitry voltage drop of the battery cell. This necessary minimum terminal voltage (1.13V) is higher than the critical or drained voltage of 1V of a typical NiMH, meaning that stored battery energy cannot be fully released and can therefore not be fully utilized.

To enhance utilization of stored battery power, an adaptive current loading scheme is proposed.

Since

I_{in_converter} = I_{out_battery_assembly}, and

where M is the number of battery in series connection to form the battery assembly and ∑ R_circuit is the sum of resistance of the circuit through which the battery current flows, it follows that a lower output load current would mean a lower battery terminal voltage that could produce the same minimum required voltage at the power converter input.

In this example, by reducing the output load current from 1.0A to 0.5A, the minimum terminal voltage to produce the minimum required voltage for operation of the power converter is reduced from 1.13V to 0.9V, as a result of halving of the battery current from 1.0A to 0.5A.

Therefore, by reducing the load current I_{out_converter} at the power converter output, the minimum cell voltage of the battery cells forming the battery assembly can be reduced to promote fuller or deeper discharge of the battery cells. In some embodiments, the minimum cell voltage is set to be at or slightly above the drained voltage or the critical voltage of the specific battery type to strike a balance between maximum discharge and longer operation life of a rechargeable battery.

Referring to Figure 5B, by reducing the load output current from a maximum load current to a minimum load current, a balance between maximum discharge and longer operation life of a rechargeable battery can be obtained.

In example embodiments, the MCU is to monitor the terminal voltage of the individual battery cells as well as the terminal voltage of the battery assembly, and to reduce the load current from maximum to minimum to correspond with a fall in terminal voltage due to battery discharge.

In general, a load current between the maximum I_max and the minimum I_min can be selected for optimal loading operations without loss of generality.

For example, the MCU is to send a control signal “0” to the OC port of the power converter of Figure 5 to set the load current to a maximum of 1A when the battery assembly terminal voltage is above a threshold voltage, say 2V, and to send a control signal “1” to the OC port of the power converter to set the load current to a lower or minimum of 0.5 when the battery assembly terminal voltage is at or approaching the threshold voltage. Where multiple load currents are available for selection on the power converter, the MCU can operate to select an optimal or most optimal load current to maximize battery utilization or to achieve other useful objectives.

While the above description is with reference to NiMH battery cells, it should be appreciated that the scheme applies mutatis mutandis to other rechargeable battery cells or primary battery cells such as alkaline battery cells without loss of generality.

Where the power pack comprises rechargeable battery cells, the power management arrangement may comprise charging circuitry to facilitate recharging of the rechargeable battery cells.

In addition, the voltage values, the current values, efficiency of power converter, the circuitry resistance, the number of battery cells, the size of battery cells, etc. referred to herein are non-limiting examples which should not be used to limit the scope of the present disclosure.

In embodiments where the minimum input voltage required by the power converter to operate can be supplied by a single battery cell or the voltage of a two-battery-cell-group exceeds the maximum allowed input voltage, the controller may form an active battery group with a single battery cell, to select a different battery cell to form a next active battery group, and then to select another different battery cell to form yet another next active battery group, until all the different battery cells (four in the example of Figure 2) forming the battery assembly have performed their discharging contribution, and then repeat, for example with the same cyclical discharging sequence or a different discharging sequence. When the voltage of the single battery cell falls below the minimum required input voltage but above its critical or drained voltage level, the controller may increment the number of battery cells forming an active battery group and perform the cyclical or sequential discharging. The increment may be by one, two, or more etc., without loss of generality.

In embodiments where the minimum input voltage required by the power converter to operate can be supplied by two battery cells or the voltage of a three-battery-cell-group exceeds the maximum allowed input voltage, the controller may form a first active battery group with a first set of two cells to perform a first discharge cycle, a second active battery group with a second set of two cells to perform a next discharge cycle (or a second discharge cycle) after the first discharge cycle, a third active battery group with a third set of two cells to perform a yet next discharge cycle (or a third discharge cycle) after the second discharge cycle, etc., until the

combination has exhausted, and then repeat the discharging sequence in the same or different cyclical manner. In the aforesaid combinations, the battery members in the first, second and third groups are non-identical and may be overlapping or non-overlapping depending on the value of N. Likewise, the controller may increment the number of battery cells forming an active battery group and perform the cyclical or sequential discharging when the voltage of the two-battery cell group falls below the minimum required input voltage but the voltage of each battery cell of the two-battery cell group is above its critical or drained voltage level. Similarly, the increment may be by one, two, or more etc. depending on the value of N without loss of generality.

Claims

A method of supplying battery power from a battery assembly, the battery assembly comprising a first plurality of N battery cells, wherein the method comprises a controller to select a second plurality of M battery cells from said first plurality of battery cells to form a battery output group and an output connection to facilitate power output from said battery assembly during a power output process, the second plurality of battery cells consisting of a number of battery cells lesser than the number of battery cells forming the battery assembly and N, M being integers; wherein a specific battery output group consisting of a specific combination of battery cells is to provide power output of the battery assembly for a specific discharge time interval during the power output process and each battery cell of a specific battery output group is to contribute to the power output for the specific discharge time interval; wherein different battery output groups are to output power at immediately adjacent discharge time intervals and the power output process lasts for a total duration between beginning and ending of the power output process, the total duration being a sum of all the specific discharge time intervals of the power output process; and wherein the controller is to select different battery cells of said battery assembly to form different battery output groups during the power output process to facilitate more equalized or more even total discharge time contribution due to the different battery cells, the total discharge time of a battery cell being a sum of all the specific discharge time intervals due to that battery cell.
A method according to Claim 1, wherein the controller is to select battery cells to form a battery output group according to connection history of the battery cells and/or operational conditions of the battery cells so that battery output groups forming a sequence of power supply connections consist of different combinations of battery cells selected from said battery assembly.
A method according to Claims 1 or 2, wherein the controller is to select the second plurality of battery cells according to the connection history of the battery cells such that an output battery group forming a first battery output group to facilitate a first power supply connection comprises at least one battery of the battery assembly which is not present in an output battery group forming a last battery output group of a last power supply connection, the last power supply connection being an output connection preceding or immediately preceding the first output connection.
A method according to any preceding Claim, wherein the controller is to select the second plurality of battery cells according to the connection history of the battery cells such that an output battery group forming a next battery output group to facilitate a next power supply connection comprises at least one battery of the battery assembly which is not present in the output battery group forming the first battery output group of the first power supply connection, the next power supply connection being an output connection succeeding or immediately succeeding the first output connection.
A method according to any preceding Claim, wherein the controller is to select a plurality of battery cells to form a next battery output group for a next discharging connection cycles according to prescribed selection criteria with reference to the connection history of the battery cells, the prescribed selection criteria comprising one or a combination of criteria below:

· whether a battery cell is an output battery cell in last J discharging connection cycles immediately preceding the next discharging connection cycles, J being an integer equal to or smaller than M; a battery cell having a larger or the largest value of J will be excluded from or has a lower chance of being selected as a member battery cell of the next battery output group;

· whether a battery cell is not an output battery cell in last K discharging connection cycles immediately preceding the next discharging connection cycles, K being an integer equal to or smaller than M; a battery cell having a larger or the largest value of M will be included in or has a has a better or higher chance of being selected as a member battery cell the next battery output group.
A method according to any preceding Claim, wherein the controller is to operate a switching circuitry to connect the battery cells forming the different battery output groups in series.
A method according to any preceding Claim, wherein the controller is to operate a switching circuitry to connect the battery cells in series to provide an output voltage within a predetermined voltage range.
A method according to any preceding Claim, wherein the controller is to operate a switching circuitry to increment the number of battery cells to be connected in series to form the battery output group when the total voltage of the second plurality of battery cells falls below a predetermined threshold voltage or to decrement the number of battery cells to be connected in series to form the battery output group when the total voltage of the second plurality of battery cells exceeds a predetermined maximum voltage.
A method according to any preceding Claim, wherein the controller is to operate a switching circuitry to exclude a battery from selection if an electrical condition or parameter of the battery falls below a performance criterion.
A method according to Claim 7, wherein the electrical condition or parameter which is below a performance criterion represents a faulty or drained battery.
A method according to any preceding Claim, wherein the controller is to select the battery cells forming the different battery output groups by sequential, non-sequential and/or cyclical selection according to the connection history of the battery cells.
A method according to any preceding Claim, wherein the method comprises boosting voltage of the battery assembly to a boosted output voltage.
A method according to Claim 12, wherein the voltage of the battery output group is in a region of 2V to 4.8V.
A method according to Claims 12 or 13, wherein the boosted output voltage is in a region of 5V.
A power supply apparatus comprising a battery assembly and a controller arranged to operate a method according to any preceding Claim.
A power supply apparatus according to Claim 15, wherein the battery assembly comprises a first plurality of battery cells and the apparatus comprising a switching circuitry, and wherein the switching circuitry is operable to connect said first plurality of battery cells in series or to selective connect a second plurality of battery cells selected from said first plurality of battery cells in series, said second plurality being lesser than said first plurality.
A power supply apparatus according to Claims 15 or 16, wherein the battery assembly NiMH battery cells, for example, 2, 3, 4 NiMH battery cells or more.
A power supply apparatus according to any of Claims 15 to 17, wherein the apparatus comprises a USB power connector for making external power connection.
A power supply apparatus according to any of Claims 15 to 18, wherein the switching circuitry comprises a plurality of series connected sections and each section comprises a connection branch comprising a connection switch in series a battery and a bypassing branch comprising a bypassing switch, the bypassing branch being in parallel with the connection branch, and wherein the connection branch and the bypassing branch are to alternately operate to facilitate selection and deselection of a battery to form a battery output group.
A power supply apparatus according to Claim 19, wherein the bypassing switch and the connection switch are oppositely or alternately operable such that when one switch is on, the other is off and vice versa.
A power supply apparatus according to any of Claims 15 to 20, wherein the battery assembly comprises two, three, four or more rechargeable or primary battery cells connected to said switching circuitry.
A power supply apparatus according to any of Claims 15 to 21, further comprising a charging circuitry to facilitate charging of the battery cells.
A method of outputting power from a battery assembly, the battery assembly having an output voltage and comprising one battery or a plurality of battery cells in series and/or parallel connection, wherein the method comprises a controller monitoring the output voltage of the battery assembly and operating a current limitation circuitry to reduce battery output current when the output voltage of the battery assembly falls to an output voltage threshold, whereby voltage drop across the battery assembly is reduced.
A method according to Claim 23, wherein the current limitation circuitry is part of a DC-DC converter and the method comprises the controller operating the DC-DC converter to limit battery output current to reduce voltage drop across the battery assembly when the output voltage of the battery assembly falls to an output voltage threshold to maintain the output voltage of the battery assembly at or above a threshold operation voltage of the DC-DC converter.
A method according to Claims 23 or 24, wherein the controller is to further reduce the battery output current when the output voltage of the battery assembly falls further from the output voltage threshold in order to maintain the battery output voltage at or above the voltage threshold.
A power supply apparatus comprising a battery assembly, a DC-DC converter and a controller arranged to operate a method according to any preceding Claim.
A power supply apparatus according to Claim 26, wherein the controller is to operate the DC-DC converter to limit battery output current to reduce voltage drop across the battery assembly when the output voltage of the battery assembly falls to an output voltage threshold so that the output voltage of the battery assembly is above a minimum operation voltage of the DC-DC converter.
A power supply apparatus according to Claims 26 or 27, wherein the battery assembly comprises a first plurality of battery cells and the apparatus comprising a switching circuitry, and wherein the switching circuitry is operable to connect said first plurality of battery cells in series or to selective connect a second plurality of battery cells selected from said first plurality of battery cells in series, said second plurality being lesser than said first plurality.
A power supply apparatus according to any of Claims 26 to 28, wherein the battery assembly NiMH battery cells, 2, 3, 4 NiMH battery cells or more.
A power supply apparatus according to any of Claims 26 to 29, wherein the apparatus comprises a USB power connector for making external power connection.
A power supply apparatus according to any of Claims 26 to 30, wherein the switching circuitry comprises a plurality of series connected sections and each section comprises a connection branch comprising a connection switch in series a battery and a bypassing branch comprising a bypassing switch, the bypassing branch being in parallel with the connection branch, and wherein the connection branch and the bypassing branch are to alternately operate to facilitate selection and deselection of a battery to form a battery output group.
A power supply apparatus according to any of Claims 15 to 22 in combination with a power supply apparatus according to any of Claims 25 to 31.
A method according to any of Claims 1 to 14 in combination with the method according to any of Claims 23 to 25.