WO2011053951A1

WO2011053951A1 - System and method for both battery charging and load regulation in a single circuit with a single, bidirectional power path

Info

Publication number: WO2011053951A1
Application number: PCT/US2010/055041
Authority: WO
Inventors: Ira S. Faberman
Original assignee: Iftron Technologies, Inc.
Priority date: 2009-11-02
Filing date: 2010-11-02
Publication date: 2011-05-05

Abstract

A method to manage battery charging, battery discharging, battery balancing, battery equalization, bidirectional voltage translation, voltage step-up, voltage step-down, or load regulation of one or more power sources employing a single, bidirectional power path, including the ability to network the system resulting in additional unique attributes.

Description

SYSTEM AND METHOD FOR BOTH BATTERY CHARGING AND LOAD REGULATION IN A SINGLE CIRCUIT WITH A SINGLE, BIDIRECTIONAL POWER PATH

RELATED APPLICATION DATA

[0001] This application claims the benefit of and priority under 35 U.S.C. §119(e) to

U.S. Patent Application Nos. 61/257,225, filed November 2, 2009, entitled "SYSTEM AND METHOD FOR BOTH BATTERY CHARGING AND LOAD REGULATION IN A SINGLE CIRCUIT WITH A SINGLE, BIDIRECTIONAL POWER PATH," which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0002] An exemplary aspect of this invention relates to voltage and current control.

Even more specifically, an exemplary embodiment is directed toward bidirectional voltage translation, as well as a battery charge and discharge controller.

SUMMARY

[0003] Lithium chemistry rechargeable batteries are significantly different in management requirements than more established chemistries based on lead or nickel, etc. This is in part because lithium chemistry batteries are highly intolerant of too high or too low a terminal voltage, and because the rate of charge and discharge must also be kept within limits.

[0004] Typically, a rechargeable lithium battery system includes a battery, a battery management system (BMS) that closely monitors the battery, and a battery charger designed specifically to charge the lithium batteries. Where the charger is not adequately adapted, a charge controller can be deployed between the charger and the battery.

[0005] Typically, a battery management system (BMS) is employed to monitor the state of the battery. As such, the BMS will monitor things such as battery voltage, individual cell voltage (where a battery includes multiple cells in series), battery temperature, etc. The BMS may also be designed to command a disconnect of the battery from the load if during discharge, the battery voltage gets too low or discharge current gets too high, or disconnect the charger in the event that the charger voltage or current gets too high. The disconnect functionality is usually carried out by relays, contactors or semiconductor switches. These devices are frequently bulky and often completely separate pieces of hardware. The BMS will also usually provide a balancing function so that individual cell voltages, where cells are in series, remain close together. Most frequently, the balancing function is preformed during charging and most notably during the last stages of charging when the battery is approaching or is at the fully charged voltage.

[0006] The lithium battery charger is typically a constant current - constant voltage system with a current limit that is consistent with the charging current limitations of the intended battery and a voltage regulation point that is consistent with the required intended battery maximum charge voltage.

[0007] Because an exemplary embodiment disclosed herein is bidirectional, it is uniquely capable of at least being able to provide the above disparate functions of BMS, discharge and charge control without the need for additional circuitry beyond that which will be disclosed for bidirectional voltage translation. However, when the exemplary embodiment is so deployed within a battery system, other novel attributes bring unique charge, discharge and BMS functionality and benefits.

[0008] During battery charging, one exemplary embodiment is fully capable of regulating the battery charge current independent from the source of charge power as long as the source current exceeds the charge current set-point of the circuit. An example of such a source might be an alternator that has sufficient current capability. Also during charging, the exemplary embodiment is fully capable of regulating and limiting the charge voltage reaching the battery. Taken together, these abilities to manage both charge current and voltage, alone supplant the need for a lithium battery charger or charge controller. What is less obvious is that the disclosed technology can also deploy sensors to monitor battery temperature and state of balance, and other factors and act upon these to modulate the charge current and voltage according to the requirements of the battery.

[0009] Further, the disclosed embodiments ca n assert a complex charging regime in response to the specific design requirements of the battery and from localized factors such as temperature, initial battery voltage, battery age, initial state of charge, state of balance, etc. The disclosed technology is also fully capable of completely disconnecting the battery from the charging source if needed.

[0010] During discharge, the disclosed technology is capable of monitoring the battery voltage and disconnecting it from the load if the battery voltage becomes too low. But unlike a simple switch, the disclosed technology is also capable of tapering the current made available to the load, as the battery voltage reaches the lower allowable voltage limit, rather than abruptly opening a switch. This feature has significant value in an operational system where an abrupt interruption of power would be undesirable.

[0011] Moreover, where a BMS might open a load switch if an overly high discharge current were detected, the disclosed technology is capable of continuous discharge current limiting at any battery given voltage, protecting the battery from discharge currents that would be too high for the specific battery.

[0012] Further, the disclosed technology is capable of modulating the discharge current limit or discharge voltage limit in response to the specific requirements of the battery and for localized factors such as battery temperature, battery age, the state of balance, etc.

[0013] Additionally, the disclosed technology can if desired, completely disconnect the battery from the load.

[0014] I n addition to the ability to function as both a charge and discharge manager or controller, the disclosed technology is capable of performing the functions of a BMS including battery voltage monitoring and battery balancing when teamed with a balancer. An example would be teaming with an embodiment of the same invention, configured as a battery balancer. Other BMS functions, including over voltage and under voltage protection can easily be handled by the ability of the disclosed technology to monitor and disconnect the battery. Even more unique is the ability of the disclosed technology to mitigate excessive demand upon the battery by limiting current or voltage in either direction;

something that a conventional BMS cannot do. Moreover, the disclosed technology can include circuitry that is capable of monitoring and logging battery data such as charge and discharge cycles, aggregate amp-hours, age, etc. Not only can the disclosed technology be configured to report on this data but can act on the data by dynamically adjusting charge and discharge voltages and currents in response to this data, as dictated by, for example, the battery operating requirements.

[0015] Between the unique charge and discharge management capabilities of the disclosed technology, it ca n be seen that the disclosed technology replaces several, otherwise disparate electronic circuits and electromechanical devices while adding uniquely enhanced functionality not commonly associated with a battery charger or controller, a discharge control or a BMS.

[0016] The foregoing characteristics and benefits are applicable in addition to and add to the ability of the invention to bidirectionally translate the voltage to and from the battery and load.

[0017] Another exemplary aspect of the disclosed technology is directed toward the bidirectional voltage translation as well as battery charge and discharge control

functionality. The charge and discharge controller aspect is valuable because along with a battery balancer (be it the disclosed balancer or a balancer using another technology), it more than adequately provides all the functionality of a battery management system (BMS) - and some type of BMS is almost always needed to make a lithium battery practical.

[0018] Yet another exemplary aspect is a BMS in combination with a bidirectional voltage translator or power controller.

[0019] The foregoing characteristics and benefits of the disclosed technology are applicable to more types of batteries and power sources than just rechargeable lithium batteries. For example, at least the following types of rechargeable batteries and power sources can be used with the disclosed technology:

Rechargeable Batteries:

Lead-acid

VRLAi

Alkaline

Ni-iron

Ni-cadmium

NIH2

NiMH

Ni-zinc

Li ion

Li polymer

LiFeP04

Li sulfur

Li titanate

Li Al Thin film Li

ZnBr

V redox

NaS

Molten salt

Silver zinc (Ag-zinc)

Other sources of stored electrical energy:

Ultra-capacitors

Flywheels

Elevated water tanks

Other energy sources:

Photovoltaic cells and arrays

Windmills/wind turbines

Hydroelectric generators

Conventional energy sources (alternators, generators, etc.)

[0020] It should be appreciated however that the disclosed technology will work equally well with other types of batteries and power sources and in general can be used with any currently existing and/or future batteries and power sources.

[0021] Yet another exemplary aspect of the invention is the ability to bidirectionally translate voltage up or down, irrespective of the presence of a battery, thus providing voltage up conversion and voltage down conversion in a single device.

[0022] These and other features and advantages of this invention are described in, or are apparent from, the following detailed description of the exemplary embodiments.

BRI EF DESCRIPTION OF THE DRAWINGS

[0023] The exemplary embodiments of the invention will be described in detail, with reference to the following figures, wherein:

[0024] Figs. 1A and IB illustrate exemplary regulator circuits.

[0025] Fig. 2 illustrates an exemplary current flow circuit.

[0026] Fig. 3 illustrates an exemplary voltage regulator circuit.

[0027] Fig. 4 illustrates another exemplary voltage regulator circuit.

[0028] Fig. 5 illustrates an exemplary bidirectional current regulating circuit. [0029] Fig. 6 illustrates an exemplary circuit that compensates for different charging and discharging requirements.

[0030] Fig. 7 illustrates another exemplary circuit that compensates for different charging and discharging requirements.

[0031] Fig. 8 illustrates a circuit with charge voltage limit regulation, discharge voltage limit regulation, charge current regulation, discharge current regulation and output voltage regulation.

[0032] Fig. 9 illustrates an exemplary equalizer or balancer using a bidirectional power path.

[0033] Fig. 10 illustrates an exemplary equalizer or balancer using a bidirectional power path and with bidirectional current limiting.

[0034] Fig. 11A - 11B illustrate an exemplary embodiment of equalizers or balancers deployed in a network.

[0035] Fig. 12A - 12B illustrate a detailed schematic of an exemplary embodiment of the invention.

[0036] Figs. 13A - 13 illustrate a detailed schematic of the exemplary embodiment of a network of equalizers or balancers.

DETAI LED DESCRI PTION

[0037] The exemplary embodiments of this invention will be described in relation to battery charging and load regulation, as well as a scalable balancing network associated components. However, it should be appreciated that in general, the systems and methods of this invention work well in a plurality of environments, including DC systems without batteries, and can be extended to include one or more batteries. I n multi-battery configurations, the batteries themselves may be in series, in parallel, or a combination of the two.

[0038] The exemplary systems and methods of this invention will also be described in relation to basic power supply and battery charging type circuitry and associated hardware. However, to avoid unnecessarily obscuring the present invention, the following description omits well-known structures, components and devices that may be shown in block diagram form, are well known, or are otherwise summarized. [0039] For purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the present invention. It should be appreciated however that the present invention may be practiced in a variety of ways beyond the specific details set forth herein.

[0040] The term module as used herein can refer to any known or later developed hardware, software, firmware, or combination thereof that is capable of performing the functionality associated with that element. The terms determine, calculate and compute, and variations thereof, as used herein are used interchangeably and include any type of methodology, process, mathematical operation or technique. Further, it is to be noted that the term "a" or "an" entity refers to one or more of that entity. As such, the terms "a" (or "an"), "one or more" and "at least one" can be used interchangeably herein. It is also to be noted that the terms "comprising", "including" and "having" can be used interchangeably. As used herein, "at least one", "one or more", and "and/or" are open-ended expressions that are both conjunctive and disjunctive in operation. For example, each of the expressions "at least one of A, B and C", "at least one of A, B, or C", "one or more of A, B, and C", "one or more of A, B, or C" and "A, B, and/or C" means A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B and C together.

[0041] In power systems where the source of power is either primarily or

secondarily a rechargeable battery, a connection to some type of battery charger is usually required. The battery charger is generally designed to provide the correct voltage and charging characteristics for the intended battery voltage, current and battery chemistry. For the purposes of discussion, the charging circuitry, whether the charger resides in an external circuit, an internal circuit, or in two or more locations, will be considered together to be the battery charger. In most cases, when not providing power, the charger is removed, left in place and powered down, disconnected or programmed off. Frequently the system design will allow the charger to provide the necessary power to the load, substituting for the battery, while the battery is being charged or whenever the charger is available as the primary source of power. Then, whenever the charger is not delivering power, the battery supplies power to the load. Classically, the charger, whether it is a separate circuit, or a circuit partially or fully integral to further circuitry, is comprised mainly of electronic components and mechanical elements that have little or no function other than to charge the battery and or concurrently support the load during battery charging. [0042] In a practical system there are many instances where the voltage or current from the battery and or charger must be further modified and or conditioned to meet the demands of the load. Examples of this include any circuit that regulates, converts or limits either the voltage or current coming from the battery or charger to make it suitable for use by the downstream elements of the system. The circuitry that regulates the voltage and or current is generally single purpose in design in that the circuit provides regulated voltage and/or protects either the downstream load or the battery from excessive current flow and little else. Generally, this downstream voltage regulation circuitry is not directly involved with battery charging. This means that the path that the majority of the current takes through this voltage regulator will not be the same path that current takes between the charger and the battery. Necessarily, this classical approach is then comprised of both a dedicated charging circuit between the source of charging power and the battery, and a separate dedicated regulation circuit between the source of power and or the battery and the ultimate load.

[0043] In accordance with one exemplary aspect, technology is disclosed that combines the functions of both battery charging and load regulation in a single circuit with a single, bidirectional power path. The exemplary technology combines those elements that classically are required both for charging and for load regulation into one circuit that provides a bidirectional power path, and thus leads not only to higher efficiency, lower cost and smaller size, but can also provide unique and surprising attributes that would otherwise be difficult or impossible to obtain.

[0044] Figs. 1A and IB illustrate exemplary circuit configurations that include a switch control circuit Al, a power source (e.g., battery VI), switches SI and S2, capacitors CI and C2 and load Rl.

[0045] In Fig. 1A, the pair of switches, SI and S2 are deployed in series across a DC voltage VI. The switches are controlled by the switch control circuit Al such that they conduct alternately. Thus, the junction El between the switches is first at the positive voltage of the source VI, and then at the negative voltage of the source VI.

[0046] An inductor LI is deployed at the junction of the switches. The other end of inductor LI is connected to capacitor CI. The other terminal of capacitor CI is tied to the negative voltage of the voltage source VI at ground. However, this terminal could as easily be tied to the positive terminal of VI or tied to both terminals of VI (with capacitor C2) as in Fig. IB.

[0047] I n accordance with an exemplary embodiment, inductor LI and capacitors CI,

C2 are of values that together comprise a substantial filter at the frequency of the alternating switches SI and S2. Since the voltage at El has an average value based on the voltage of VI relative to the on times of S1/S2 being switched (hereinafter called the duty cycle - which can be any value between 0 and 100%), the DC voltage E2, at the junction of LI and CI, C2 is the average voltage that is substantially equal to the voltage across VI times the duty cycle of S1/S2.

[0048] As an example, if the voltage across VI is lOVDC, and the duty cycle of S1/S2 is 50%, the average voltage at El and at E2 will both be 5VDC. If the duty cycle is changed to 25%, the voltage at El and E2 will both be 2.5V. The only difference between El and E2 is that LI and CI filter out the majority of the AC component of the signal. It is therefore apparent that by varying the ratio of on times of S1/S2, any voltage between 0V and the full voltage of VI can be caused to appear at E2.

[0049] If a load represented by Rl (where Rl is understood to represent any number of types and magnitudes of possible loads) is imposed across E2 to ground, and assuming that there are no other resistors in the circuit, the voltage at E2 will not change because the duty cycle has not changed and because LI is theoretically a DC conductor with no resistance. However, in practical circuits, the larger the load that Rl imposes, the lower the voltage at E2 will be. This voltage change is largely caused by the unavoidable resistances and switching times of practical components and conduction paths in the circuit. Thus, if it is desired to maintain a precise voltage at E2, an adjustment in the duty cycle is required to compensate for these unavoidable circuit resistances and/or imperfections.

[0050] Fig. 2 illustrates an exemplary current flow control circuit that includes comparable componentry as Fig. 1, but the load is now battery Bl, representative of one of many possible sources of energy.

[0051] If Bl represents a discharged battery or capacitor with a predisposed charge of, for example, zero volts (0V), the circuit will cause current to flow into Bl and thereby charge Bl until the voltage across Bl is substantially equal to the open circuit voltage at E2, where the voltage at E2 is a function of the voltage across VI and the duty cycle of S1/S2. [0052] Thus, it can be seen that if before connection, Bl was lower in volts than the open circuit voltage at E2, Bl will charge up. And, if the preexisting voltage of Bl was equal to the voltage at E2, when attached to the circuit, no current will flow and a state of equilibrium will exist. What is less obvious is that if the preexisting voltage of Bl is higher than that of the open circuit voltage of E2, energy will flow out of Bl and into VI. This would charge a battery at VI, if one were present, or simply raise the voltage of VI until the point of equilibrium was met. This is because the voltage at E2 is either a direct result of the voltage across VI and the duty cycle of S1/S2, or if E2 is a source of energy upon which the duty cycle of SI, S2 will act through LI, voltage VI is the result of the voltage at E2 and the duty cycle of SI, S2. It is important to note that this is without regard for polarity or current flow so long as circuit elements VI, Bl, SI, S2 and LI are understood to be bidirectional elements. When these conditions are met, there is no predisposition to the specific directionality of current flow except that the direction of current flow is a function of the difference in magnitude of the voltage of VI and voltage of E2 and the duty cycle of SI, S2.ln summary, the direction of current flow between E2 and El and therefore into or out of VI is a function of the difference in voltage between E2 and the average voltage of El, where the average voltage of El is a function of the voltage of VI times the ratio of on times or duty cycle of SI and S2.

[0053] This clearly demonstrates the direction of current flow is thereby

controllable, however, the magnitude of current flow in either direction is a function of the difference between the voltages of E2 and El, where El is the average of voltage VI and Bl and the duty cycle of S1/S2, divided by the total of the series resistances in the circuit. This, if there were no circuit resistance, any difference whatsoever in the voltage between El and E2 would cause infinite current to flow. However, in practical circuits, all the circuit elements have some resistance and therefore, the magnitude of current for a given voltage ratio is thereby governed.

[0054] From the above, it follows that two voltage sources, VI and Bl may be deployed in the circuit such that no current flows even though VI and Bl may be substantially different in voltage, as long as the ratio of difference in voltages VI and Bl is matched by the same ratio of duty cycle of S1/S2. Said another way, for any two given voltages at VI and Bl, there exists a duty cycle of S1/S2 that will cause no DC current to flow. [0055] For example, if Bl is introduced to the circuit with a predisposed voltage of 5 volts DC, and VI has a voltage of 10 volts DC, while the duty cycle of S1/S2 is 50%, no current will flow and a state of electrical equilibrium will exist. When so deployed, thenceforth both the magnitude and direction of current flow between VI and Bl can then be changed by changing the on-time ratio of the duty cycle of S1/S2 on either side of the point of electrical current equilibrium.

[0056] Fig. 3 illustrates an arrangement that regulates the voltage at E2 as a function of difference between the voltage at E2 and a reference voltage E3. An error amplifier A2 is deployed such that the voltage E2 is made responsive to the difference between the reference voltage E3 and the voltage of E2, by adjusting the duty cycle via the switch control circuit Al (shown here in block diagram form for simplicity) that controls the on-time ratio duty cycle of switches Sland S2. It is notable that the circuit is capable of adding or removing energy from Bl as is appropriate to regulate the voltage at E2 to the regulation voltage E3 as impressed by Zener diode Dl at the input of error amplifier A2.

[0057] Fig. 4 illustrates a similar but complimentary arrangement in which the voltage of VI is regulated rather than that of the voltage at E2. Thus the circuit can add or remove energy from VI as needed to achieve voltage regulation at VI by adding or subtracting it from Bl.

[0058] For the purpose of this example, VI is assumed to be a voltage source that has sufficient compliance to afford external regulation. Such a source might include a battery or batteries, a large capacitor or capacitors, other electrical storage element(s), or other source(s) of power.

[0059] Fig. 5 illustrates one exemplary way of regulating or limiting the current flowing in either direction as may be necessary to protect circuit components, for performance reasons, or the like. For clarity, voltage regulation componentry that was demonstrated in the previous figures has been removed, leaving only the current regulating components.

[0060] In Fig. 5, R2 is a sense resistor deployed in series within the main current path for the purpose of measuring the magnitude and direction of current flow. R2 only represents a current monitoring device, since there are many ways that this measurement can be accomplished, including, for example: magnetic amplifiers and Hall Effect devices, to name just a few. Indeed, the sensing element can be deployed in many locations in the current path in order to achieve the desired result. Note that the example clearly demonstrates the capability of the circuit to separately regulate or limit the current flowing one direction verses the other. This may be very advantageous in practice because, for example, in the case of use as a charge and discharge control, the battery may have distinctly different charging current requirements, compared to discharge current capability. I n this example, Zener diodes D2 and D3 represent two different reference voltages, one for charge current regulation and one for discharge current regulation.

[0061] Each is deployed at the inputs of separate error amplifiers A3 and A4. A3 and

A4 influence the switch control circuit Al, through diodes D4 and D5. Note that the polarity of D4 and D5 are such that the range of influence of each error amplifier over switch control circuit Al is limited to one direction only. This circuit not only demonstrates that the current can be regulated or limited, but the regulation point can be different for each direction of current flow in the circuit.

[0062] Taken together, Figs. 1 through 5 and the forgoing text, illustrate that voltage can be regulated for either VI or Bl, either by adding or subtracting energy to either source of energy, VI or Bl, and that current can also be regulated or limited in either direction, regardless of the magnitudes of voltage of VI or Bl, by manipulating the on-time duty cycle of S1/S2 such that it deviates on the appropriate side of the duty cycle point of electrical equilibrium. The result of this ability will be more fully explained by the following examples which are for illustration purposes only and are in no way intended to suggest the limits of application of this technology.

[0063] Fig. 6 illustrates an exemplary circuit wherein the circuit is deployed between two batteries, B2 and Bl that have different voltages, different chemistries and different charging requirements. I n this example, let battery B2 be representative of a lithium battery and Bl be representative of a lead-acid battery. As discussed, the batteries need not be those as specifically shown in this example, but in general can be any type of battery(ies) and/or energy source(s) as discussed above.

[0064] Let Rl represent the system load and Gl a battery charger. To further the example, let Bl and Gl represent an existing battery and charging system such as that commonly found throughout industry or in transportation. Thus, it will be understood that Gl and the implied voltage regulation contained therein, are already suited to the task of charging Bl and of supporting the load Rl. The exemplary embodiment is connected to the existing battery, load and charger through connector Jl, and returned through a common ground. In this arrangement, the voltage of B2 is necessarily larger in voltage than Bl.

[0065] In operation, error amplifier A2 compares the voltage of the lead-acid battery, Bl to the reference voltage at E5, and through R3, controls the switch control circuit Al to keep the desired voltage on Bl constant.

[0066] For the purposes of this example, let the voltage across Bl measurable at E2 be equal to the resting voltage of a fully charged lead-acid battery Bl. For this example, this is about 12.6V. With charger Gl turned off, any load from Rl will start to decrease the voltage across battery Bl. Error amplifier A2 will regulate the voltage at E2 by adjusting the duty cycle of switches S1/S2 such that the voltage at E2 remains constant, by adding sufficient energy to battery Bl from battery B2.

[0067] This process will continue for as long as there is energy remaining in battery

B2. During this time, battery Bl will remain charged because the load current is being sourced by B2 and error amplifier A2 is keeping the voltage of Bl constant. If however, the load demand at Rl is more than battery B2 or the circuit can supply, B2 discharge current will be limited by error amplifier A4. Amplifier A4 will, through diode D4, override the control of amplifier A2 and adjust the duty cycle via switches S1/S2 to limit the discharge current, when the current derived voltage across current sense resistor R2 exceeds the discharge current reference voltage at E3.

[0068] When charger Gl is energized, the charger will attempt to charge battery Bl.

Battery chargers designed to charge lead-acid batteries will attempt to raise the battery voltage to roughly above the resting point. However, as soon as the voltage across Bl exceeds the regulation voltage of 12.6V, error amplifier A2 will adjust the duty cycle of switches S1/S2 in an attempt to keep the voltage at E2 constant. In doing so, the circuit will draw energy from Bl and Gl and add this energy to B2, which will then commence charging. Thus, the direction of energy transfer has been accomplished without relays, switches, redundant circuitry, complimentary circuitry, or by the use of two current paths. Instead, the exemplary circuit uses a single, bidirectional current path for both discharge and for charge and does so smoothly.

[0069] When the current charging B2 increases the voltage across R2 until it is equal to or greater than the reference voltage E4, error amplifier A3 will, through diode D5, override the control asserted by amplifier A2 and limit the current charging battery B2 to the desired level. Battery B2 will continue to charge at this regulated current rate until the voltage across B2 reaches the voltage limit as set by error amplifier A3 and reference voltage E6, whereupon amplifier A5 through diode D6 will override the current limiting amplifier and modify the duty cycle of switches S1/S2 such that the voltage on battery B2 ceases to increase. The voltage will thus remain constant as the charging current flowing into B2 tapers off. This is consistent with typical regimes associated with charging, for example, lithium chemistry batteries.

[0070] During the time when current limiting amplifier and voltage limiting amplifiers A3 and A5 are in control, they are both limiting the current taken from the battery charger Gl. Thus, A3 and A5 may be adjusted so that there will be additional current available from the charger Gl for charging the battery Bl if it had been previously discharged. This implies that by deliberately limiting the charge current flowing to battery B2 with regard to the charging capability of charger Gl, the system can apportion how much current will be used to charge B2 and how much will be left over to charge Bl and to simultaneously aid in supporting any loads imposed by Rl. An example might be that if the battery charger were capable of 50 amps, the B2 charge limit might be set to 20 amps, leaving 30 am ps available to charge Bl and to supply load current while still allowing B2 to charge.

[0071] I n similar fashion to the above, error amplifier A6 will protect battery B2 from over-discharge by comparing the voltage across B2 to reference voltage E7 and limiting the discharge voltage of B2 to a safe lower limit, below which, no further discharge will be allowed. At this point, the circuit will limit the current available from B2 to avoid over- discharge, and any continuing load imposed by Rl will finally draw the rest of the current from Bl.

[0072] It should be restated that one exemplary embodiment the source of energy with the series switches deployed across it should be higher in voltage than the other source of energy. This is predominantly because voltage equal to that of the second source of power must be achievable by dividing the voltage of the first source of power by the on- time duty cycle of the series switches S1/S2 or current equilibrium cannot exist.

[0073] The foregoing discussion of Fig. 6 and associated text described an embodiment wherein the battery with the lower voltage is used as the focal point of voltage regulation. That is, the system will charge or discharge the higher battery, based on the deviation of the lower battery from a predetermined regulation voltage.

[0074] However, the forgoing is not the only configuration of the circuitry that is possible. Fig. 7 demonstrates a circuit arrangement that has a similar function. However, in this circuit, the voltage of the higher voltage battery, here illustrated as a series connection of two batteries, BIA and BIB, is used as the determining factor for charge and discharge of B2. Close examination and comparison with the embodiment of Fig. 6 will reveal very little difference between the two embodiments. Even the amplifier sense points are located in the same place in the block diagram. For example, the voltage regulation amplifier A2 senses the existing battery Bl but at a higher voltage, while those dedicated to protecting the additional battery B2 sense that voltage, albeit at a lower voltage.

[0075] Thus, this embodiment illustrates that the system is not limited by the difference in voltage of the two power sources.

[0076] Until now, all references to duty cycle of the switches S1/S2 have assumed that at all times, either SI or S2 were conducting. However, there are times during operation that it is advantageous that the total time that SI and S2 are in conduction are not equal to 100% of the total period. The advantage of this is that if the conduction time periods are interspersed with periods when neither switch is conducting, the effective impedance of the circuit increases without incurring actual resistive losses.

[0077] Raising the effective impedance has the advantage of reducing the current available to the load when such a reduction in current is desirable. These times include but are not limited to initial start-up or when recovering from a fault condition, including occurrences such as a short circuit across the output. During times such as these, if the resistances in the circuit are low, large currents may flow due to large voltage mismatches between the voltage of the power source with the series switches across it times the duty cycle of the switches and the voltage of the other power source, or in other words, when the circuit is very far from the current equilibrium point. It is then advantageous to limit the conduction time of the switches and therefore limit the current that ca n flow. By doing so, extraneous and potentially harmful currents will be suppressed. Then by slowly increasing the conduction periods until full conduction is achieved, the control loops have the time to settle at the proper operating point without incurring unintended currents. [0078] I ndeed, continuing to limit the conduction periods of the switches to something less than full, is a valid means of current regulation that may be employed within the spirit of the disclosed technology. It therefore follows that when both switches are turned off, a diode will be needed in parallel with the switches in appropriate polarity. This is necessary for the commutation of energy in the inductor back to the system during switch off times. Such diodes are intrinsic within the structures of some types of modern switches, or sometimes co-packaged with the switch. I n cases where the switches themselves do not contain the diodes, external diodes should be added to the circuit for inductive current commutation to proceed without there would be excessive voltage stress upon the switches and other circuit components.

[0079] It should be recognized that the examples given here are for the purposes of illustration and understanding and not to be taken as the only application of the disclosed technology. Also, the illustration through the use of batteries is not to be construed as suggesting that other sources of power could not be substituted or that applications should be limited to those containing only batteries or capacitors. As discussed, there are many other sources of energy and energy storage to which the concepts set forth here apply. There are even applications where only one source of power is required.

[0080] Fig. 8 is an exemplary embodiment that only includes one battery B2. As ca n be seen, Fig. 8 is identical to Fig. 6 except that power source Bl has been removed. When the source of power Gl is not energized, the exemplary embodiment provides power to the load Rl and will do so as long as power is available from the source of energy B2. When the Gl is energized, the energy in B2 will be replenished while Gl will supply additional current to support the load. In this way, the exemplary system allows the use of a source of power B2 that is not equal in voltage to the load requirement, yet, the system does the required voltage regulation, while at the same time, acts as a battery manager that can accurately charge the battery while protecting it from over voltage, under voltage, excessive charge current and excessive discharge current, through the use of a single bidirectional current path.

[0081] There are also applications where the technology ca n be used to equalize or balance the voltage between 2 batteries. An example of this can be seen in Fig. 9.

[0082] Figure 9 demonstrates how two batteries, Bl and B2 ca n be equalized or balanced in a non dissipative-manner through a bidirectional power path. [0083] In Fig. 9, the batteries Bl and B2 are placed in series, and series switches SI and S2 are placed across them. One node of LI is placed at the junction of the two batteries El. Thus the series combination of Bl and B2 are representative of one source of power and B2 alone is representative of the other source of power.

[0084] If, for example, amplifier A2 did not affect the switch control Al and the duty cycle of S1/S2 was deliberately set at a constant 50% by the switch control, current would only stop flowing out of or into B2 when the voltage at the junction of the two batteries was equal to the voltage of the two batteries in series, divided by the duty cycle of S1/S2.

Although not necessary for operation, the addition of a ratiometric, voltage-based control loop, shown as Rl, R2 and A2, improves the response of the circuit and hastens equalization because it will increase the equalization current and keep this current high until voltage equalization occurs. To do this, error amplifier A2 compares the voltage at El, the junction of the two batteries, with the voltage E2 at the junction of a voltage divider. In this example, the design voltages of the two batteries is assumed to be the same and thus, if Rl is equal to R2, A2 will adjust the duty cycle to make El equal to E2, or 50% of the total voltage across both batteries. If batteries of different design voltages are so deployed, the ratio of Rl to R2 can be changed to accommodate this difference, so that the junction of the two batteries will still be equalized to the correct voltage for each battery. By so deploying the technology in a ratiometric manner, equalization occurs regardless of the state of charge of the batteries or the total voltage across them.

[0085] It should be noted that if error amplifier A2 has sufficient gain, the circuit will apply sufficient current in the proper polarity such that the voltage at the junction of Bl and B2 will be virtually the same as the voltage at E2 even before the true resting voltage of the batteries would be thus if the circuit were to be disabled. This is because a battery cannot change its resting voltage, which is dependent on its state of charge, instantly. This occurs because most batteries can be grossly modeled as a capacitor in series with an internal series resistance. Thus, although the terminals of the battery can be impressed with a particular voltage by external circuitry (in this case 50% of the voltage of the series connected pair), the internal voltage across the internal storage medium (modeled as a capacitor) has not yet caught up due to the before mentioned internal series resistance. When such is the case, a tapering current will flow until the actual state of charge has asymptotically reached the potential impressed across the battery terminals in like fashion to the current in a series connected resistor and capacitor. This so called "taper charge" is familiar to those skilled in the art of battery charging as the portion of the charge when the battery is approaching full charge under a charging regime that is constant current/constant voltage in nature. What may not be as familiar to many is that this phenomenon presents for any given state of charge and can be demonstrated both during charging and

discharging, whenever a change in terminal voltage is externally impressed upon the battery.

[0086] The result of this phenomenon is that if amplifier A2 acts to impresses the balanced voltage upon the junction of batteries Bl and B2, there will be some time delay before the batteries will be truly balanced, and during this time the current in the batteries will taper down, finally reaching an insignificant level. At this time, the resting voltage of the batteries will be said to be balanced.

[0087] The time that the tapering current takes to balance the states of charge can be seen as a limitation of the effectivity of a balancing system. I ndeed, the time that the current takes to taper down to insignificance can be protracted, depending on the battery construction, chemistry and other factors. However, Fig. 10 demonstrates a refinement of the circuit set forth in Fig. 9 that ca n greatly reduce the time for current tapering to occur and thus improve the effectivity of the system.

[0088] Fig. 10 illustrates a modification the circuit of Fig. 9 through the addition of current sense amplifier A3 and resistor R3. It is the purpose of these additional components to move the balance reference voltage E2 in such direction so as to further increase the balance current flowing in the batteries Bl and B2 in response to the instantaneous balance current. This is accomplished by impressing a larger or smaller voltage across the battery terminals (depending on the direction of balancing current) while the taper current is flowing, than the final balance voltage when the circuit is finally at equilibrium.

[0089] Because the battery current will taper during balancing, the circuit will act to reduce the effect upon the balance reference voltage proportionally toward the final level at the fully balanced state. This dynamic approach to the balancing reference voltage significantly increases the average current during current tapering and thereby significantly reduces the time that taper requires.

[0090] As an example, if one assumes that the starting potential at El is lOOmv from the balance reference voltage at E2, then as in the circuit presented in Fig. 9, error amplifier A2 would act to impress the voltage at E2 across the battery terminals. This amounts to a net voltage difference of lOOmv between the present battery resting voltage and the impressed terminal voltage. The batteries would then either charge or discharge beginning with a current equal to 100mv/Br, where Br is the equivalent internal series resistance of the battery. For this example, let the value of Br be equal to .01 ohms. Then the initial battery current would be 10 amps and would ta per down from this value as the state of charge of the battery changed. If however as in the Fig 10, a circuit responsive to balancing current is added, the voltage at E2 will be modified in response to balancing current such that a higher net voltage difference between the resting voltage and balance voltage were presented at the battery terminals. This, in turn, then increases the balance current so that the state of charge of the batteries changes more quickly. Because the newly increased current would then cause a further increase the balance current, etc., a runaway condition could be induced if the transfer function of the circuit containing amplifier A3 were too great. However, the system is stable if the overall transfer function has a gain of less than 1. Near this point, the result would be nearly a 2:1 increase in balance current or 20 amps with a significant shortening of required balance time.

[0091] An exemplary application of the arrangement of Fig. 9 can be seen in Fig. 11.

[0092] I n Fig. 11, a number of batteries (Bl - B6) (although any number of batteries could be present) are deployed in series in order to achieve a required total voltage for a given application. A scalable network of the circuits disclosed in Fig. 9 is interspersed across the series of batteries in such a manner that each junction in the series string of batteries is serviced by the disclosed technology. When so deployed, the system will equalize or balance the voltages of all batteries regardless of the absolute voltage of the series string, or the state of charge. This is because, if a single battery is out of voltage balance, energy is either added or subtracted from the adjacent batteries on either side and any change in the voltage of the adjacent batteries due to the transfer of energy, will be balanced out in similar fashion from the circuits servicing them. So it can be seen that regardless of the total voltage across the series of batteries, or the state of charge, the system will equalize the voltages of all of the batteries. The number of batteries in series can be any required number as needed to supply the voltage to the system with which it is associated.

[0093] Deploying the technology in a network as in Fig. 11 results in an unexpected result. If a source of external power is applied to any junction in the network, the incoming energy will be distributed to all the batteries, regardless of the point of entry, by the means already described for balancing. For example, a battery charger may be applied to E3, a power port. The energy would initially go to charge battery B2, but as soon as the voltage across B2 starts to rise, the circuit will begin to transfer energy from B2 to Bl. Thereupon the circuit will remove energy from Bl and distribute it to B3 and will by the network, distribute the energy throughout the battery. This process is highly advantageous since it allows a source of charging energy to be applied that is not equal to the total battery voltage. It should be understood that port E3 can be placed at any junction between any of the batteries such as ports E5, E7, E8, etc., and the placement in this example is only for illustration and clarity. Although each section in Fig. 11 depicts an error amplifier, and the amplifiers enhance operation, they are not strictly necessary for operation, since in many applications, it may be sufficient to set the duty cycle of the switches at the ratio of the two battery design voltages tied to the junction as described earlier.

[0094] A further and perhaps even less obvious attribute to deploying the technology in a network as in Fig. 11 is that energy can be removed from E3 as in the load imposed by R9. When a load represented by R9 removes energy, the technology acts to distribute the energy loss to all batteries in the system. Since E3 has been placed in the example for illustration and could instead be placed at any battery junction, it is easy to understand that several of such ports ca n be placed wherever desired and that multiple loads and power sources of various voltages ca n thereby be accommodated without unbalancing the battery(ies).

[0095] It is therefore even possible to charge this arrangement through any convenient port(s) while simultaneously discharging it through one or more different ports.

[0096] Figs. 12A - 12B illustrate an exemplary detailed working schematic of one embodiment of the invention. More specifically, Figs. 12A - 12B show a detailed working schematic of one embodiment of Fig. 8. While specific part numbers and component values are illustrated, it should be appreciated that the parts and component values may change depending on the environment in which the technology is deployed.

[0097] As can be seen in the figure, there is a voltage charge limit portion, a current charge limit portion, a voltage regulation portion, a switch drive/control portion, a current discharge limit portion, and a current sensing portion. [0098] Figs. 12A-12B are a detailed schematic of a working system that adds lithium battery power to existing lead-acid battery systems.

[0099] Figs. 13A - 13B illustrate a portion of Fig. 11 in greater detail including exemplary specific component parts that can be used to realize the circuitry of Fig. 11. In Figs. 13A - 13B, the circuit varies from Fig. 11 in that in Fig. 11 has four identical balancing sections, while the exemplary detailed Fig. 13 shows only two. The circuit in Figs. 13A - 13B can be scaled as appropriate as discussed in relation to the above embodiments.

[00100] Figs. 13A-13B are a detailed schematic of a working network of bidirectional battery balancers.

[00101] While the invention is described in terms of exemplary embodiments, it should be appreciated that individual aspects of the invention could be separately claimed and one or more of the features of the various embodiments can be combined.

[00102] The present invention, in its various embodiments, includes components, methods, processes, means, systems and/or apparatus substantially as depicted and described herein, including various embodiments, subcombinations and subsets thereof. Those of skill in the art will understand how to make and use the present invention after understanding the present disclosure. The present invention, in various embodiments, includes providing devices and processes in the absence of items not depicted and/or described herein or in various embodiments hereof, including in the absence of such items as may have been used in previous devices or processes, e.g., for improving performance, achieving ease and/or reducing cost of implementation.

[00103] The foregoing discussion of the invention has been presented for purposes of illustration and description. The foregoing is not intended to limit the invention to the form or forms disclosed herein. In the foregoing description for example, various features of the invention are grouped together in one or more embodiments for the purpose of

streamlining the disclosure. The features of the embodiments of the invention may be combined in alternate embodiments other than those discussed above. This method of disclosure is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the following claims are hereby incorporated into this description, with each claim standing on its own as a separate exemplary embodiment of the invention. [00104] Moreover, though the description of the invention has included description of one or more embodiments and certain variations and modifications, other variations, combinations, and modifications are within the scope of the invention, e.g., as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative embodiments to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures, functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter.

Claims

Claims:

1. A system capable of one or more of battery charging, battery balancing, battery equalization and load regulation of one or more power sources with a single, bidirectional power path.

2. The system of claim 1, wherein the one or more power sources are a network of series connected power sources.

3. The system of claim 1, wherein the power sources are one or more of, or a combination of: one or more batteries, one or more rechargeable batteries, one or more capacitors, one or more ultra-capacitors, one or more flywheels, one or more elevated water tanks, one or more photovoltaic cells or arrays, one or more wind turbines, one or more hydroelectric generators, one or more alternators, one or more generators and one or more sources of DC energy.

4. The system of claim 3, wherein the rechargeable batteries are one or more of lead-acid batteries, VRLAi batteries, alkaline batteries, Ni-iron batteries, Ni-cadmium batteries, NIH2 batteries, NiMH batteries, Ni-zinc batteries, Li ion batteries, Li polymer batteries, LiFeP04 batteries, Li sulfur batteries, Li titanate batteries, thin film Li batteries, ZnBr batteries, V redox batteries, NaS batteries, Molten salt batteries, Silver zinc (Ag-zinc) batteries, lithium-aluminum batteries and other types of rechargeable batteries.

5. The system of claim 1, further comprising a switch controller that controls a first and a second switch.

6. The system of claim 5, wherein the switch controller regulates a duty cycle of the switches.

7. The system of claim 6, wherein the duty cycle can be varied by varying a ratio of on times of the switches such that any voltage can be obtained.

8. The system of claim 6, wherein the duty cycle can be varied by varying a ratio of on times of the switches such that the system is capable of controlling a current made available to a load.

9. The system of claim 1, wherein the system is scalable to include multiple instances of the system.

10. The system of claim 9, wherein the scalable system includes a plurality of balancing sections, the balancing sections allowing power to be one or more of supplied and discharged at a plurality of nodes within a circuit network.

11. A system that manages a group of series-connected networked power sources, wherein power can be added or removed at any of a plurality of nodes in a network simultaneously, and any power loss or gain is distributed amongst the plurality of networks power sources in the network.

12. The system of claim 11, wherein the group of networked power sources include one or more of, or a combination of: one or more batteries, one or more

rechargeable batteries, one or more capacitors, one or more ultra-capacitors, one or more flywheels, one or more elevated water tanks, one or more photovoltaic cells or arrays, one or more wind turbines, one or more hydroelectric generators, one or more alternators, one or more generators and one or more sources of DC energy.

13. A method to manage a group of series-connected networked power sources using a plurality of balancing networks, wherein power can be added or removed at any of a plurality of nodes in a network simultaneously, and any power loss or gain is distributed amongst the plurality of networks power sources in the network.

14. The method of claim 12, wherein the group of networked power sources include one or more of, or a combination of: one or more batteries, one or more

15. A method to manage one or more of battery charging, battery balancing, battery equalization and load regulation of one or more power sources employing a single, bidirectional power path, wherein a switch controller regulates a duty cycle of a plurality of switches, wherein the duty cycle can be varied by varying a ratio of on times of the switches such that the voltage of the one or more power sources can be obtained and the duty cycle can be varied such that the system is capable of controlling a current made available to one or more loads.

16. The method of claim 15, wherein the duty cycle is controlled by one or more feedback loops.

17. The method of claim 16, wherein the one or more feedback loops include one or more error amplifiers.

18. One or more means for performing the functionality of claim 15.

19. A power control system comprising:

a plurality of scalable, series-connected networkable balancing circuits, each scalable, networkable balancing circuit including:

a switch controller,

an error amplifier,

a plurality of switches, wherein on times of the plurality of switches are controlled by the switch controller and the error amplifier to control charge current, discharge current and voltage regulation,

wherein the plurality of scalable, networkable balancing circuits are connectable to one or more power sources.

20. Any one or more of the features substantially as disclosed herein.