Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/50—Current conducting connections for cells or batteries
  • H01M50/502—Interconnectors for connecting terminals of adjacent batteries; Interconnectors for connecting cells outside a battery casing
  • H01M50/514—Methods for interconnecting adjacent batteries or cells
  • H01M50/516—Methods for interconnecting adjacent batteries or cells by welding, soldering or brazing
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
  • H01M50/204—Racks, modules or packs for multiple batteries or multiple cells
  • H01M50/207—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape
  • H01M50/209—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape adapted for prismatic or rectangular cells
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
  • H01M50/233—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders characterised by physical properties of casings or racks, e.g. dimensions
  • H01M50/242—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders characterised by physical properties of casings or racks, e.g. dimensions adapted for protecting batteries against vibrations, collision impact or swelling
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/50—Current conducting connections for cells or batteries
  • H01M50/502—Interconnectors for connecting terminals of adjacent batteries; Interconnectors for connecting cells outside a battery casing
  • H01M50/503—Interconnectors for connecting terminals of adjacent batteries; Interconnectors for connecting cells outside a battery casing characterised by the shape of the interconnectors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/50—Current conducting connections for cells or batteries
  • H01M50/502—Interconnectors for connecting terminals of adjacent batteries; Interconnectors for connecting cells outside a battery casing
  • H01M50/509—Interconnectors for connecting terminals of adjacent batteries; Interconnectors for connecting cells outside a battery casing characterised by the type of connection, e.g. mixed connections
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
  • H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
  • H02J7/0014—Circuits for equalisation of charge between batteries
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• This invention relates to power supplies, and more particularly to battery packs or battery power systems with multiple battery units, and their associated wiring, charging, and discharging.
• a typical battery pack is characterized by having more than one battery cell. Such packs do not perform, have the same operating characteristics, or life cycle as individual cells.
• a cell is a single battery unit. During charge and discharge cycles, individual batteries in the pack will often diverge or drift from the pack average or pack target value. Often the pack performance is limited by the weakest or strongest cell during discharge and recharge.
• a typical battery management system uses electronic devices such as thermistors or transistors in series or parallel with each cell to locally control the charge or discharge of the cell.
• a battery pack connection scheme is shown that provides a synchronized DC environment for every cell in the pack, such that every cell in the same or similar voltage level in the pack sees an identical, or very similar, voltage and current environment.
• One aspect of the invention features a power supply module having multiple battery units each having an anode and a cathode.
• the battery units are connected in parallel to supply at least 50 amps of electrical current to a high-power load.
• the connections are made via a conductive assembly that includes multiple conductive paths each connecting to a respective battery and passively prevents voltage divergence of the multiple battery units.
• Each of the multiple conductive paths has an under- load resistance matched to an under- load resistance of each of the other conductive paths.
• the under-load resistance of each conductive path differs from that of the other parallel conductive paths by less than about one milli-ohm, or in some cases by less than about one-tenth of a milli-ohm. In some examples, the under-load resistance of each conductive path differs from that of the other parallel conductive paths by less than about 1%.
• Each of the multiple conductive paths preferably also has an under-load inductance matched to an under-load inductance of each of the other paths.
• the multiple conductive paths each include a respective cable and a respective portion of a solid terminal bus connecting the cables and a load connection terminal.
• the conductive assembly may include high power precision DC cables, for example, that are attached to the terminal bus at respective cable terminals equally spaced from the load connection terminal.
• the cable terminals are disposed on a circle having the load connection terminal at its center.
• the solid terminal bus includes silver-plated soft copper.
• the conductive assembly also prevents capacity divergence of the multiple battery units.
• the conductive assembly includes a busbar.
• Another aspect of the invention features a battery pack capable of supplying at least 50 amps of current having a positive load connection terminal and multiple battery units each having an anode and a cathode.
• the cathodes of the batteries are connected in parallel to the positive load connection terminal via respective and distinct conductive paths.
• Each conductive path has an under-load resistance differing from an under-load resistance of each other path by less than about one milli-ohm.
• the anodes of the multiple batteries are connected in parallel to a negative terminal bus via multiple conductive paths all having identical electrical lengths.
• each of the batteries has resistance properties matched to the resistance properties of the other batteries and, preferably, each battery has an impedance of less than about 50 milli-ohms.
• the conductive paths preferably have a loaded series impedance at least five times greater than the loaded output impedance of the batteries.
• Each of the batteries preferably has charge-acceptance properties matched to the charge-acceptance properties of the other batteries.
• the battery pack includes a positive power cable connected to the positive terminal bus such that a similar resistance may be measured from the second end of the cable to the cathodes of each of the multiple batteries.
• the positive terminal bus is connected to the center of a round conductive piece.
• the conductive paths may include a precision DC cable and, in some cases, a solder joint connecting the precision DC cable to its respective battery cathode.
• each of the solder joints has a solder joint resistance value precision matched to that of the other solder joints.
• Another aspect of the invention features a battery pack having multiple batteries connected in parallel to a positive load connection terminal via respective conductive paths, each of the conductive paths including a respective high-power DC precision cable segment.
• each of the conductive paths has a resistance suitable to allow an average charge acceptance rate of the battery pack to be greater than a Cl charge rate.
• the battery pack includes a second set of batteries connected in parallel with each other and connected in series with the first set of batteries.
• the second set of batteries are preferably connected in parallel to each other with precision conductive segments each having equal resistance.
• the ratio of the loaded amperage capacity (in amps) to the loaded impedance (in ohms) of each conductive path is at least 1000 to 1. In some examples, the ratio of the desired operating amperage (in amps) to the loaded impedance (in ohms) being at least 1000 to 1.
• the under-load resistance of each conductive path differs by less than about a 1% tolerance.
• Each of the conductive paths preferably has an operating resistance matched to an operating resistance of the other conductive paths and/or an operating inductance matched to an operating inductance of the other conductive paths.
• the conductive paths may each include precision cable segments having matching lengths.
• each of the conductive paths are capable of carrying charge current of at least 5 amps.
• the precision cable segments are connected to the positive load connection terminal with precision-matched connections.
• the precision-matched connections preferably include low-resistance solder connections.
• Some aspects of the invention feature a power supply system having a positive load connection terminal, a negative load connection terminal, and multiple ranks of batteries. The ranks are connected in series with precision low-impedance conductors connecting multiple batteries within each rank.
• the battery anodes of the most negative rank are connected in parallel to the negative load connection terminal via respective conductive paths.
• the battery cathodes of the most positive rank are connected in parallel to the positive load connection terminal via a second set of respective conductive paths.
• the under- load resistance of each of the conductive paths differs by less than about a 1% tolerance.
• Other aspects of the invention feature methods of mitigating battery characteristic divergence within a battery pack.
• One aspect includes selecting multiple batteries based on their individual loaded output resistance and charge acceptance characteristics; connecting the multiple batteries in parallel in a battery pack; and, while charging the multiple batteries simultaneously, maintaining both equal charging voltages across each of the connected batteries and maintaining equal charge-acceptance rates in each of the connected batteries.
• the method includes selecting multiple batteries each having matched discharge rate characteristics and connecting the multiple batteries in parallel in a battery pack.
• the method includes discharging the multiple batteries simultaneously into a load, and while discharging the multiple batteries simultaneously, maintaining equal discharging voltages across each of the multiple batteries, maintaining equal discharge rates in each of the multiple batteries, and/or maintaining equal discharge currents in each of the multiple batteries.
• the method includes enclosing each of the multiple batteries in a compression cage, and/or compressing each of the batteries to mitigate previous battery swelling.
• the selected batteries have a charge acceptance rate of Cl or higher, and/or a discharge rate of Cl or higher.
• connecting the batteries in parallel includes connecting the batteries to each other with a high-power precision DC cabling assembly or a high-power precision DC busbar assembly.
• FIG. IA shows a battery pack formed from two batteries connected in parallel using precision conductors.
• FIG. IB is a circuit diagram of the battery pack shown in FIG. IA.
• FIG. 2 is a generalized circuit diagram of a battery pack according to another implementation.
• FIGs. 3 A and 3B are more detailed circuit diagrams of the buses 301, 302 shown in
• FIGs. 4A-C show 12 volt battery pack with parallel batteries and precision conductors according to another implementation.
• FIG. 4A illustrates the internals of the 12 volt battery pack.
• FIG. 4B is a representation of the assembled 12 volt battery pack.
• FIG. C is a circuit diagram of the 12 volt battery pack.
• FIGs. 5A-D illustrate a 24-volt battery pack using precision conductors according to another implementation.
• FIG. 5A illustrates the internals of the 24-volt battery pack.
• FIG. 5B is a representation of the assembled 24-volt battery pack.
• FIG. 5 C is a circuit diagram of the 24-volt battery pack.
• FIG. 5D is a circuit diagram of the 24-volt battery pack described above.
• FIG. 5E depicts a battery compression cage.
• FIGs. 6A-C illustrate a 36-volt battery pack using precision conductors, similar to the battery pack described above in FIGs. 5A-D, with the addition of another column of power cells.
• FIG. 6 A depicts a perspective view.
• FIG. 6B depicts an enlarged perspective of a precision conductive ladder.
• FIG. 6C depicts a perspective view of a housing.
• FIG. 6D is a circuit diagram of a 36V battery pack.
• FIGs. 7A-D illustrate a high-power battery pack suitable for powering a remote installation.
• FIG. 7A depicts an enlarged perspective of battery interconnects.
• FIG. 7B depicts a preferred lattice support frame.
• FIG. 7C depicts an enlarged perspective of a crossbar bus.
• FIG. 7D depicts an enlarged perspective of an output bus.
• FIGs. 7E-G depicts a circuit equivalent to the battery pack depicted in Figs. 7A-7D.
• FIG. 7E is the pack circuit diagram.
• FIG. 7F is detailed circuit diagram of an output bus.
• FIG. 7G is another detailed circuit diagram of an output bus.
• FIG. 7H depicts another output connection solution.
• FIG. 8 shows an example of precision conductor configuration
• FIGs. 9A-C illustrate a circuit diagram of a system for providing electric power.
• FIG. 9 A is a circuit diagram of the power system.
• FIG. 9B is a circuit diagram of a negative bus.
• FIG. 9C is a circuit diagram of a positive bus.
• FIGs. lOA-C illustrate a circuit diagram of a system having a battery pack coupled to a automobile electrical system.
• FIG. 1OA is a circuit diagram of the power system.
• FIG. 1OB is a circuit diagram of a negative bus.
• FIG. 1OC is a circuit diagram of a positive bus.
• FIG. IA shows a battery pack formed from two batteries connected in parallel using precision conductors.
• a battery pack 100 may have batteries 101, 102, a positive terminal 106, a negative terminal 108, and cables 111, 112, 121, 122.
• the batteries 101, 102 may supply similar voltages and currents.
• the cables 111, 112, 121, 122 connect the batteries 101, 102 to the terminals 106, 108 in a parallel fashion.
• the terminals 106, 108 supply the voltage and combined current to an external device.
• a device connected to the battery pack of receives a voltage equivalent to that provided by of a single battery and a current equal to the sum of the individual battery currents.
• Batteries 101 and 102 have similar construction to ensure they have similar electrical characteristics. For example, the batteries 101 and 102 may use the same chemistry, have the same dimensions, etc. As a result of their similar construction, the batteries 101 and 102, have nearly identical voltage and current output curves when the same load is applied is applied to each battery.
• Batteries 101 and 102 may be a common type. For instance, they may be a high performance sealed, lead acid battery. Batteries 101, 102 used in the battery pack 100, and in other embodiments, may be individual cells or batteries of cells. For example, in one instance, the batteries 101, 102 may each be a single 1.5 volt cells; in other instances, each battery may be a combination of multiple cells, such as 12 volt battery consisting of eight 1.5 volt cells connected in series. In some instances, the batteries 101, 102 may be rechargeable; in this case, the battery pack may be replenished by applying an external voltage to the battery pack terminals 106, 108.
• the battery pack may be charged by connecting a standard battery charger to the battery pack terminals.
• the batteries employed herein are sealed lead-acid batteries such as those described in U.S. Patent Nos. 6,074,774 and 6,027,822, which are hereby incorporated by reference in their entirety for all purposes. Batteries used herein preferably have the lowest series impedance possible for the chemistry used, with some preferred embodiments of the lead-acid batteries employed having an open circuit series impedance of 5-10 milli-ohms or less. Series impedance varies greatly among different battery designs. Other battery chemistries may be used depending on the desired applications, operating environments, and costs. For example, Ni-Cad, NiMH, Li-Polymer, or Li-Ion or any other suitable battery.
• the cables 111, 112, 121, 122 are manufactured as identically as possible to ensure that they have similar electrical characteristics to each other within a given battery pack.
• the cables 112 and 122 have characteristics as closely as possible identical to each other.
• Cables 111 and 121 are similarly identical to each other, and may be identical to cables 112 and 122, ensuring similar electrical characteristics as seen by the batteries 101, 102 looking to load terminal 106. If the loads applied to the two batteries are similar and the batteries themselves are similar, the batteries are likely to drain at the same rate and retain similar voltages. As a result, the batteries tend to be drained at a similar rate without the use, in this embodiment, of any active battery management systems or other active battery management circuitry present between batteries 101, 102 and load terminal 106 and 108.
• the cables 111, 112, 121, 122 are preferably precision manufactured to reduce variability.
• the cables 111, 112, 121, 122 may be manufactured from the same material lots for creating a single set.
• all the cables for a battery pack may be manufactured a single piece of cabling.
• Use of a single source of material used for constructing cables may reduce the likelihood of variation in electrical variation due to, for example, variations in wire looping, insulation, etc.
• FIG. IB is a circuit diagram of the battery pack shown in FIG. IA.
• the first cable 111, first battery 101, and second cable 112 form a parallel circuit with the third cable 121, second battery 102, and fourth cable 122. Resistance, inductance, and capacitance is modeled for each cable.
• the first cable 111 has a corresponding resistance HlR, an inductance 1111, and a capacitance HlC.
• the second cable 112 has a corresponding resistance 112R, an inductance 1121, and a capacitance 112C.
• the third cable 121 has a corresponding resistance 121R, an inductance 1211, and a capacitance 121C.
• the fourth cable 122 has a corresponding resistance 122R, an inductance 1221, and a capacitance 122C.
• the circuit branch consisting of cable 111, battery 101 and cable 112 is very similar and preferably identical to the branch consisting of cable 121, battery 102 and cable 122.
• the depicted cables 111, 121, 112, and 122 are preferably high power DC cables each comprising at least one high power DC precision cable segment. Such high power DC cables are preferably of the same length, material, and cross section.
• the resistance of the cables and connections is preferably as low as possible. Their length is preferably matched by precision measurement and cutting techniques to ensure accuracy. Further, the connections to each depicted battery terminal are also preferably identical.
• IA and IB there are uniform parallel conductive paths comprising, in order, as contained in this embodiment: the bolted connection from the positive terminals of batteries 101 and 102; the transitioning conductive connection from the fitting bolted to each battery terminal to the cable conductor in each of cables 112 and 122; the cables 112 and 122; the cable-to-fitting conductive connection at the positive terminal 106 end of each cable 112, 122; the fitting at such ends; and the conductive path portions of positive terminal 106 from each cable to a load connection point on the terminal.
• Each of these conductive portions is preferably identical or, as closely as possible, similar to its mirror image in the parallel conductive path.
• identical it is meant, in this case, identical materials, size, shape, and electrical properties such as the identical electrical resistance, capacitance, and inductance illustrated in Fig. IB.
• electrical properties of the conductive portions are made to be as similar as possible.
• the impedance of the high-power precision DC cables, and the various connection fittings and solder connections that may be employed in construction of the implementations herein, is preferably as low as possible under existing design constraints. In one implementation, this is achieved by using fittings and busbars that are copper with silver plating, although other suitable low-resistance and low loaded-inductance connections may be used.
• the silver to silver connections provide low impedance and low oxidation.
• the surface of the connections is preferably polished and processed with an oxidation inhibitor treatment to help ensure the extremely low resistance connections retain their characteristics for as long as possible.
• preferred cables used herein are selected to be oversized for their power load requirement in order to reduce their series resistance.
• high power precision DC cables used herein may be selected, for example, to work under a 50- amp current load.
• high power DC cables are selected having a series resistance preferably as low as less than 2 milliohms under load.
• a ratio of current to resistance Amps/Ohms
• this example provides a 50,000/1 ratio at 1 milliohm, and a 25,000/1 ratio at 2 milliohms.
• “high power” could mean that each conductive path (each battery) provides 5 amps or 1 amp, for example, depending on how many batteries are in a pack.
• Connectors used herein may also be oversized to reduce their equivalent series resistance and enable such large currents without excessive power dissipation.
• Figs. IA and IB depict uniform parallel conductive paths comprise cables and bolted electrical fittings
• other embodiment may use any suitable conductive materials and fittings to form the parallel conductive paths, provided respective parallel paths are preferably identical or, as closely as possible, similar.
• precision matched-length high-power DC cables comprise the parallel conductive paths some embodiments described herein, solid busbars, traces, or other conductors may also be used if they are suitable for the power load of the desired application.
• the properties achieved by employing matched precision cables may also be achieved in some embodiments by employing low resistance busbar designs.
• busbar designs it is imperative that each busbar section is identical and dimensional equivalent providing for identical resistance, capacitance, and inductance where such equivalence is required in the circuit.
• precision cables are typically cables where the resistance, capacitance, and inductance are known or equal to other precision cables of the same design and construction.
• the construction of a precision cable is made by manufacturing matched cable sets which are constructed from the same cable roll (lot) using copper connectors that are silvered and crimped and soldered using exactly the same process. Small variations in the manufacturing process can lead to large differences in the cables.
• the matched cables are bench tested for consistency (or differences) before being put into a pack construction.
• Resistance, inductance and capacitance values for cable 111 are very close to corresponding values for cable 121, creating a synchronized DC environment from negative terminal 108 to the negative battery terminals of each of batteries 101 and 102.
• Resistance, inductance and capacitance values for cable 112 are very close to corresponding values for cable 122, thereby creating a similar synchronized or uniform DC environment from positive terminal 106 to the positive battery terminals of each of batteries 101 and 102.
• the batteries preferably have identical or, as closely as possible, similar electrical characteristics. As a result, power draw from the batteries is similar if a load is placed on terminals 108, 106.
• battery pack 100 provides a voltage and current output from terminals 106, 108.
• the connecting circuitry preferably maintains an equal discharge current from each battery, and an equal voltage across each battery. Conversely, during the charging process, the connecting circuitry maintains an equal charge current to each battery and an equal voltage across each battery.
• IB operates passively to match the DC current and voltage at the output terminals of batteries 101 and 102, which may be described as providing a synchronized DC environment
• a synchronized DC environment may be used to passively prevent divergence of battery performance characteristics, under discharge (loaded pack) and charge (charging pack) conditions.
• the battery pack 100 is rechargeable. Since the two branches of the circuit are identical or similar, half of an applied charge is deposited in each battery. While the battery pack 100 is being charged, the batteries 101, 102 may be charged at an equal or, as closely as possible, similar rate such that, at any given time, the batteries 101, 102 have approximately the same amount of stored charge, thus maintaining the similarity of their electrical characteristics such as voltage, capacity, charge acceptance rate, and temperature.
• FIG. 2 is a generalized circuit diagram 200 of a battery pack according to another implementation.
• Figs. 3A and 3B show elements of the circuit 200, regions 3A and 3B as marked with dotted lines in FIG. 2, in further detail.
• circuit 200 has an array batteries 211B-2NMB connected with precision conductors each represented by a resistor, inductor and capacitor such as 21 IR, 2111, and 211C.
• the array of batteries has batteries connected in series or parallel by the precision conductors.
• the array may provide or store electric power via the external interface.
• Particularly, arrangements of the battery array and precision conductors with many parallel batteries result in a battery pack with higher current capacity than a single row. Arrangements with many batteries in series (rows in Fig. 2) provide a higher voltage.
• the depicted circuit 200 has an array of batteries and conductors.
• Reference numbers associated with elements of the array may indicate the type of the element and its position within the array. For most of the reference numbers in FIG. 2, the first digit of the reference number may indicate the figure number, the second digit may indicate a row position, and the third digit may indicate a column position with "N" and "M" corresponding to the final row or column in an array with N rows and M columns of batteries.
• Reference numbers ending with an "R” refer to the equivalent resistance of a conductor
• reference numbers ending with an “I” refer to the equivalent inductance of a conductor
• reference numbers ending with a “C” refer to the equivalent capacitance of a conductor
• reference numbers ending with a "B” refer to a battery.
• the batteries in the circuit 200 should be of a similar type. For example, they should have the same chemistry and physical construction.
• the batteries may be of a standardized lead-acid type, capable of high power output.
• the batteries should have similar electrical characteristics. For instance, the batteries may provide similar currents at a similar voltage when an identical load is applied across their positive and negative terminals.
• the batteries in the depicted array are connected in series using precision conductors.
• a set of batteries are connected in series if the positive terminal of one battery is connected to the negative terminal of another battery.
• the output voltage of a series circuit is equal to the sum the voltages of the batteries that are in series.
• the first row of the circuit 200 may consist of batteries 21 IB, 212B, ... 21MB, and the voltage across the series is equal to the sum of the voltages of batteries 21 IB, 212B, ... 21MB.
• a second row in the array may consist of batteries 221B, 222B, ... 22MB also connected in series.
• the batteries in the circuit 200 may be connected parallel using precision conductors.
• the current capacity of the system increases with the number of parallel branches. For example, a circuit with four parallel branches will have twice the current capacity of a circuit with two parallel branches.
• a first column in the depicted array consist of batteries 21 IB, 221B, 23 IB, 241B, ... 2NlB connected in parallel; the current capacity of this portion of the circuit is equal to the sum of the currents capacity of the batteries 21 IB, 221B, 231B, 241B, ... 2NlB.
• Precision conductors may be modeled by a resistor, an inductor, and a capacitor.
• Each resistor, inductor, and capacitor in FIGs. 2 and 3A-B corresponds to the resistance, inductance, and capacitance of the electrical path, e.g. a conductor, that directly connects two elements in the circuit 200.
• conductor 212 linking batteries 21 IB and 212B may be modeled by resistor 212R, inductor 2121, and capacitor 212C.
• batteries within a given column are connected in parallel.
• battery 21 IB produced a higher voltage than battery 22 IB
• current would flow through the circuit-loop consisting of the battery 21 IB, conductors 212, 2122, 222, battery 22 IB, and conductor 2121.
• batteries in parallel may not charge to their full capacity if the electrical couplings between the circuit connector and each battery do not all have the same characteristics.
• the depicted connecting circuitry preferably maintains an equal discharge current from each battery, and an equal voltage across each battery. Conversely, during the charging process, the connecting circuitry maintains an equal charge current to each battery and an equal voltage across each battery. Further, because the battery characteristics are kept identical or as similar as possible, the charge-acceptance rates of the batteries are maintained as equal.
• the parallel combination divides the series impedance of each battery (or series line of batteries) by the number of parallel connections, thus drastically reducing the series impedance of the pack and increasing the maximum charge rate.
• a maximum charge rate may be employed to implement a pulse charging scheme, for example.
• conductors linking batteries in series within adjacent columns have identical or, as closely as possible, similar electrical characteristics.
• all the conductors linking two columns of batteries may have a nearly identical resistance.
• the resistances 212R, 222R, ...2N2R of all the conductors linking the first two battery columns may be the same within 1%.
• a 5% tolerance is considered acceptable, but for other applications (typically larger arrays) a 1% or 0.1% tolerance is preferred.
• all the conductors linking two columns of batteries may have a nearly identical inductance.
• the inductances 2121, 2221, ...2N2I of all the conductors linking the first two battery columns may be the same within 0.1% or less.
• Larger arrays of batteries preferably have smaller tolerances.
• the array depicted in FIG. 7 preferably has a 0.1% or less tolerance.
• all the conductors linking two columns of batteries may have a nearly identical capacitance.
• the capacitance 212C, 222C, ...2N2C of all the conductors linking the first two battery columns may be the same within 1%.
• the similarity of impedance values may apply to operating (under load) characteristics as well as to open circuit characteristics.
• Precision conductors may be made to have similar characteristics by tightly controlling manufacturing variation.
• a single batch of batch of material may be used to create a matched set of conductors.
• the precision conductors may be wires, cables, solid conductors, etc.
• a single spool of cable may be used to manufacture a set of matched conductors; for example, conductors 212, 222, 232,...2N2C may all be manufactured as a batch from the same spool of cable, with the same equipment, by the same operator during the same shift.
• Conductors 311-3 IN link each battery 21MB-2NMB on the positive edge of the array to a positive bus 301.
• Conductors 321-32N link each battery 211B-2N1B on the negative edge of the array to a negative bus 302.
• the conductors 321-32N also have identical or, as closely as possible, similar electrical characteristics to ensure that the circuit paths between each of the batteries and busses 301, 302 are as identical as possible.
• the conductors 311-3 IN are similarly identical to each other, and may be identical to conductors 321-32N. Similarly to the embodiment in FIG.
• this scheme provides for an identical or similar voltage level at the positive terminal of each battery in the top-level (highest voltage potential) column of batteries, 21MB-2NMB.
• the row conductors 311-3 IN at the positive end of the array are each connected to positive bus 301 and thereby conductively coupled to the positive main output line 310.
• the row conductors 321-32N at the negative end of the array are each connected to negative bus 302 and thereby conductively coupled to negative main output 320.
• FIGs. 3 A and 3B are more detailed circuit diagrams of the buses 301, 302 shown in FIG. 2.
• the output busses 301, 302 in this embodiment are designed to have conductive paths with similar electrical characteristics as seen from the output lines 310 and 320.
• the row conductors 311-3 IN are linked to the positive main output line 310 in a manner that facilitates similar conductive paths from the terminals of to the positive bus 310.
• the positive row conductors 311-3 IN may be joined to bus 310 in a radially symmetric fashion such as being clamped to a physically disc-shaped conductor, at locations equidistant from its center, with the positive main output line 310 attached to the center.
• conductors 321-32N on the negative edge of the battery array may be connected via bus 302 to negative main output line 320.
• the electrical characteristics of each path between the row conductors at the edge of the battery array and the main output lines 310, 320 may be modeled, as described above for the conductors linking batteries, by a resistor, an inductor, and a capacitor.
• the electrical characteristics in the positive bus 301 between conductor 311 and the positive main output line 310 may be modeled by a resistor 3 HR, an inductor 3111, and a capacitor 3 HC; electrical pathways between the positive line and the other conductors 312-3 IN may be similarly modeled. Buses which result in electrical pathways being nearly identical (e.g. within 1%), such as the configurations described above may further serve to equalize current flow through the batteries in the circuit 200.
• FIGs. 4A-C show 12 volt battery pack with parallel batteries and precision conductors according to another implementation.
• FIG. 4 A illustrates the internals of the 12 volt battery pack.
• FIG. 4B is a representation of the assembled 12 volt battery pack.
• FIG. 4C is a circuit diagram of the 12 volt battery pack.
• FIG. 4 A is an exploded diagram illustrating the internals of an exemplary 12V battery pack.
• the battery pack has high-performance power cells 401-405, precision cables 410, and a frame with several parts. Power cells 401-405 are connected in parallel by precision cables 410. The precision cables carry power from the power cells to an output connector 423 which may be coupled to an external load via a power bus and attached cables. The frame holds the assembly together.
• This exemplar battery pack may provide high levels of current to an electric device, such as an electric fork lift.
• Power cells 401-405 are connected in parallel with precision cables 410.
• the power cells have similar electrical characteristics, such as voltage and current output and charging curves.
• Precision cables 410 also have similar electrical characteristics, such as resistance, inductance, and capacitance, in order to provide a synchronized DC environment with equal voltages at each positive battery terminal as discussed herein.
• Precision cables 410 may be manufactured as described above to minimize the electrical differences among them.
• Precision cables 410 connect each of the power cells to a positive bus 413 and negative power bus 417, in parallel fashion.
• the power buses 416, 417 are in turn connected via a positive output cable 421 and a negative output cable 422 to a main output connector 423.
• the power buses 413, 417 are designed to minimize differences in the electrical paths between the precision cables 410 and the output cable 421. Such optimization may be performed by, for example, designing the power buses with the output cable 421 in the center of the bus. Some implementations may allow the distance between the output cable 421 and the various precision cables 410 to only vary by a certain tolerance, such as 1 milliohm, 10 milliohms, 50 milliohms, or 100 milliohms, for example.
• the depicted power busses 413 and 417 are, in this embodiment, straight busbars with the output connection made in the physical center of the busbar. Preferably, use of straight busbars (if no further parallel cabling is used in combination) is limited to bars less than 6" in length, in order to minimize parallel path length variation.
• a battery monitor shunt 426 may be used to monitor current flowing through the power cells 401-405. For example, multiple shunts may be placed such the current flowing through a single power cell may be monitored. Such information that is gathered may be used, for instance, to detect asymmetries in the battery pack 400, to monitor power remaining, to aid in charging control, etc.
• the conductors in the system e.g. the precision cables 410
• other techniques for forming the connections such as soldering, may be used.
• a frame holds the assembly together.
• a bottom compression frame 430 is located at the lower end of the stack of power cells 401-405 and a top compression frame 433 is located at the upper end of the stack.
• One or more compression braces 435 may connect the top compression frame to the bottom compression frame.
• the compression frame thus formed may prevent the power cells 401-405 from deforming, such as may occur during charging or discharging.
• One possible benefit of preventing the deformation of the power cells 401-405 is to preserve the physical structure of the power cells so that electrical similarity among them is not lost.
• the inter resistance and voltage of the power cell may deviate from the other power cells in the battery pack to cause an internal current loop that depletes the stored energy and accelerates the deleterious battery divergence causing battery failure or performance degradation.
• FIG. 4B shows an exterior view of the battery pack 400 embodiment depicted above in FIG. 4 A.
• Lift handles 437 may be attached to the assembly for ease of handling or to attach the battery pack, for instance to another device being powered such as a forklift.
• the lift handles 437 may protrude through a cover 440 which may provide additional support or prevent unnecessary exposure of the internals of the pack.
• FIG. 4C is a circuit diagram of the 12V battery pack described above.
• FIGs. 5A-D illustrate a 24-volt battery pack using precision conductors.
• FIG. 5 A illustrates the internals of the 24-volt battery pack.
• FIG. 5B is a detailed view of the 24-volt battery pack interconnect ladder.
• FIG. 5 C is a representation of the assembled 24-volt battery pack.
• FIG 5D is a circuit diagram of the 24-volt battery pack.
• FIG. 5 A is an exploded diagram illustrating the internals of an exemplary 24-volt battery pack.
• the battery pack has high-performance power cells, precision cables, and a frame.
• the power cells are interconnected with precision interconnect ladders.
• the precision cables carry power from the power cells to an to an output connector external load via a power buses and output cables.
• the frame holds the assembly together.
• the resulting battery pack may supply approximately twice the voltage and five times the current of a single 12-volt power cell.
• Power cells 511-525 are capable of storing and releasing electrical energy.
• the power cells 511-525 all have similar electrical characteristics, such as similar voltage and current curves during charge and discharge cycles.
• the power cells 511-525 are electrically linked within the battery pack 500 by interconnect ladders 540 (FIG. 5B), precision cables 550, a positive power bus 560, and negative power bus 562.
• each power cell is connected to all other power cells via the precision interconnect ladder 540 and power buses 560, 562.
• Interconnect ladder 540 located on one end of battery pack 500 links power cells in each row in a serial manner.
• Interconnect ladder 540, along with precision cables 550 and power buses 560, 562, also link the power cells in each column in a parallel manner in locations with similar voltage potentials, thus forming a circuit similar to that depicted in FIGs. 2 and 3A-B in general (described above in further detail) and forming circuit depicted in FIG. 5D in particular.
• the precision cables 550, precision interconnect ladder 540, and power buses 560, 562 preferably have uniform electrical characteristics, such as resistance, inductance, and capacitance, to ensure that the currents passing through each power cell is identical or matched as closely as possible, such as by controlling design, materials, and manufacturing (as further described herein).
• Precision cables 50 connect each row of the power cells to a positive bus 560 and negative power bus 562, in parallel fashion. Power buses 560 and 562 are in turn connected via a positive output cable 570 and a negative output cable 572 to a main output connector 574.
• the precision cables 50, precision interconnect ladder 540, and power buses 560, 562 are designed to minimize differences in the electrical paths between the precision cables 550 and the output cable.
• the distance between the output cable 521 and the various precision cables 550 may vary by less than a specified tolerance.
• Power busses 560 and 562 are, as discussed above, circular with terminal connections made in the center and parallel connections made along the circumference to provide matched conductive paths to the terminal connection.
• Battery monitor shunts 580 may be used with a battery monitoring system 582 to monitor current flowing through the power cells 511-525. For example, multiple shunts may be placed such the current flowing through a single power cell may be monitored. Such information that is gathered may be used, for instance, to detect asymmetries in the battery pack 500, to monitor power remaining, to aid in charging, etc.
• the conductors in the system e.g. the precision cables 550
• other techniques for forming the connections such as soldering, may be used.
• a frame holds the assembly together.
• a bottom compression frame 590 may be located at the lower end of power cells 515-525 and a top compression frame 593 may be located at the upper end of power cells 515-525.
• One or more compression braces 595 may connect the top compression frame 593 to the bottom compression frame 590.
• the compression frame thus formed may prevent the power cells 515-525 from deforming, such as may occur during charging or discharging. Such a scheme has beneficial electrical results as described above.
• FIG. 5E depicts a battery compression cage.
• Some implementations may employ battery compression cages for individual batteries, for reasons similar to the compression frames discussed herein.
• the depicted battery 5El in FIG. 5E may have swelling due to cycling and temperature variation.
• Battery compression cages 5E2 and 5E3 are bolted around the housing of battery 5El to form a "battery wrap" housing that mitigates swelling.
• a the compression cage depicted shows two parts held together with bolts 5E4 and 5E5, other designs may be employed.
• Some embodiments may compress a previously swelled battery to conform to its specification dimensions, or to more closely match such dimensions.
• Other embodiments may employ single-battery compression cages to prevent or reverse swelling.
• the cages may be added as an after-market improvement to battery cells that are purchased having an existing housing, even if such cells have a built in frame designed to stabilize the mechanical dimensions of the battery.
• Some implementations of battery packs may employ individual cages as depicted for all or some of the battery cells of the pack.
• the cages may also provide mechanical support and stability for the pack.
• FIG. 5C shows additional views of the battery pack 500 described above in FIG. 5 A.
• Lift handles 597 may be attached to the assembly for ease of handling or to attach the battery pack, for instance to another device being powered such as a forklift.
• the lift handles 597 may protrude through a cover 598.
• the cover 598 may provide additional support to the assembly or prevent unnecessary exposure of the internals of the pack.
• a battery monitoring system 582 may make use of the battery monitor shunt(s) 580, for instance, to monitor the remaining power level.
• FIG. 5D is a circuit diagram of the 24-volt battery pack described above.
• Precision cables 550 are depicted with their equivalent impedances which, as discussed, are preferably identical or as similar as possible.
• the depicted circuit diagram also includes equivalent impedances 5Dl -4, which represent an additional, optional, busbar connected as closely as possible to the negative terminals of batteries 511-15.
• a similar optional busbar may be connected along the positive battery terminals (not shown). This busbar serves, in combination with precision cables 550, as another conductive assembly which may provide a uniform DC environment at the connected battery terminals.
• FIGs. 6A-C illustrate a 36-volt battery pack using precision conductors.
• the battery pack 600 is similar to the battery pack 500 described above in FIGs. 5A-5D, with the addition of another column of power cells.
• Three columns of parallel 12V cells (611, 621, and 631) are connected in series to provide a 36V battery pack, as compared to the two columns of 12V cells depicted in FIGs. 5A-D.
• the depicted embodiment in FIGs. 6A-C also provides output busses such as negative output bus 662 arranged physically along the side of battery pack 600.
• An alternate design of an interconnect ladder 640 is shown in FIG. 6B.
• the equivalent circuit for battery pack 600 is shown in FIG. 6D, and shares similar matched impedances relationships in each column as previously discussed.
• FIGs. 7A-D illustrate a high-power battery pack suitable for a large scale load leveling or uninterruptible power system (UPS).
• a load leveling system may be employed, for example, to minimize peak power demand or cost, or to provide peak power in scenarios where the local grid capabilities are limited.
• a remote research station or a mission-critical factory assembly line may a UPS as a primary or secondary energy system where a power grid is not available or reliable enough to meet requirements. Such a system may also be used to provide isolation from a main power grid. In such case, power may come wholly or partially from other sources, such as a battery pack or uninterruptible power system.
• the battery pack 700 may be beneficially employed in a UPS.
• the battery pack 700 has power cells, a support frame, and precision conductors.
• the power cells are of a uniform type with similar electrical characteristics.
• the precision conductors link the power cells into a grid with parallel and series portions, and link the battery pack to an external load.
• the frame supports the power cells and precision conductors in an organized fashion. The resulting battery pack is capable of providing and storing a large amount of electrical power.
• a number of power cells 702 are arranged on a frame 704. As described above, the power cells are of a uniform nature with similar electrical characteristics.
• the frame has a lattice structure with horizontal and vertical dividers 706, 708 (FIG. 7B). The space bounded by the dividers 706, 708 may be used to hold power cells.
• FIG. 7C depicts an embodiment of a long crossbar bus 710.
• Such busses are used in the depicted battery pack 700 to connect all the terminals that share a similar voltage level.
• the depicted battery pack 700 has 10 levels each with 10 batteries arranged side by side.
• a crossbar bus 710 connects the batteries at each level in parallel.
• Crossbar bus 710 is preferably made of soft copper or another suitable conductor with a low resistance (such as aluminum or copper and various alloys thereof) and has preferably equally spaced tap holes 712 for connection with bolts.
• crossbar bus 710 Connected along crossbar bus 710 are depicted ten shorter conductive bars 714 which implement connections between the depicted levels of power cells.
• the power cells are batteries having battery terminals are presented on side faces of the battery housing as conductive tapped holes with a conductive facing.
• Conductive blocks 716 are provided with tap holes on two faces to assemble each conductive bar 714 to its crossbar bus 710 with conductive bolts 718 and washers 720 and to connect to the two batteries, between which each conductive bar 714 vertically spans, with conductive bolts 722 and washers 724.
• Other suitable conductive connection schemes may be used.
• a limitation present in selecting such conductive connections is that the current output of a battery under operation will flow through a conductive bar 714, while only minimal current would typically flow horizontally along the length of a crossbar bus 710. This is because preferably the crossbar busses 710 are present to passively cause exact conformance of battery terminal voltage at each voltage level, so no cross current flows in ideal operation, while deviations from ideal battery convergence may cause minimal adjusting currents in crossbar busses 710.
• This and other similarly-configured high power busbar connection schemes may be referred to as a high-power precision DC busbar assembly.
• FIGs. 7E-G depicts a circuit equivalent to the battery pack depicted in Figs. 7A-7D.
• the batteries shown in physical perspective (FIG. 7C) as the lowermost depicted row often batteries are represented in circuit form (FIG. 7E) as battery elements 7E1-7E10.
• the physical top row of batteries in FIG 7C is represented by circuit elements 7E11-7E20 in FIG. 7E.
• conductive connections 7E21-30 are preferably made by conductive blocks 716, or similar pieces, coupling negative output busbar 726 to the lowermost battery row 7E1-7E10.
• Such conductive connections 7E21-30 are represented by their equivalent series impedances as depicted by resistor 7E31, inductor 7E32, and capacitor 7E33.
• resistor 7E31, inductor 7E32, and capacitor 7E33 are represented by their equivalent series impedances as depicted by resistor 7E31, inductor 7E32, and capacitor 7E33.
• parallel connections are uniform precision matched connections. It is only necessary that they are matched with each other at each voltage level (i.e. 7E21-7E30 all match). Figs.
• FIG. 7E connected along crossbar bus 710 are depicted ten shorter conductive bars 714 which implement connections between the depicted levels of batteries. Such connections are depicted in the FIG. 7E circuit as conductors (each represented by an equivalent R, I, and C element) in the vertical column labeled 710. Each conductive bar 714 in this embodiment being a single connecting conductive piece represented in FIG. 7E by its R, I, and C equivalent, such as those labeled 7E34.
• Each voltage level in the depicted pack 700 has at least one crossbar buss 710.
• a negative output busbar 726 (detailed in FIG. 7D) connects the most negative battery terminals in pack 700 together in parallel, and is thus the lowest voltage (typically OV) busbar of the pack 700.
• the next higher potential busbar is a 12V crossbar buss 710 arranged across the positive terminals of the depicted lower level of ten batteries. This 12V crossbar bus is on the back side of the depicted pack 700 and is not shown (the depicted batteries have positive terminals toward the opposite longitudinal end from the negative terminals).
• the next crossbar bus 710 (shown in Fig. 7C as 710(1) is at a 24V potential, and is shown conductive coupled to the positive terminals of the second-level depicted batteries and the negative terminals of the third-level depicted batteries. The connections are made similarly to raise the voltage level so that the positive output bus 728 (FIG 7D) is at a 120V potential.
• the crossbar busses 710 and the conductive bars combine to serve a similar function to the interconnect ladders previously described.
• FIG. 7D depicts an enlargement of the positive output bus 728, which connects to the most positive ten battery terminals in pack 700.
• the input and output power connections may be made to pack 700 in a variety of ways. Power may be extracted by, for example, conductively coupling a power cable to the middle of the input and output busbars. Connections to cables or other busbars may be made at the end of the output busbars 726 and 728. Such an arrangement is non-ideal, however, because it would present a non-equal DC resistance to each battery terminal from the power cable. (The conductive path is longer to the batteries on each end of pack 700). Some implementations may use an oversized busbar to minimize the DC resistance inequality.
• One preferred embodiment employs at least a five times capacity sized busbar, which may provide an end to end resistance within the desired system tolerance, such as, for example, below 0.5 or 0.1 milli-ohms.
• FIG. 7H depicts another output connection solution.
• This solution connects high- power cables 7Hl -10 to positive output busbar 728.
• the opposing end of the cables are connected to a main output line terminal 7Hl 2, which connects to a main output line or to the power load(s), for example.
• Cables 7H1-10 preferably have uniform precision impedances according to the methods described herein. That is, their equivalent series impedances shown in FIG. 7H are preferably identical or as similar as possible.
• Negative output terminal 726 has a similar connection according to this scheme. This presents a more uniform or synchronized DC environment as seen from the load.
• FIG. 8 shows an example of precision conductor configuration.
• the precision conductor 800 is in a "U" shape.
• the precision conductor 800 has slots 806A-D to which battery terminals may be connected, such as for forming a parallel or series circuit.
• This style of conductor may, for example, facilitate arranging batteries in a configuration designed to fit a constrained volume or make it easier to access portions of a battery pack that are being serviced.
• the conductor is designed such that the electrical characteristics between any adjacent two battery terminals connected the precision conductor 800 are uniform.
• FIGs. 9A-C illustrate a circuit diagram of a system for providing electric power.
• the system 900 has a genset 902, a battery pack 906, an inverter 908, and a charger 910.
• a genset refers to a electrical power generator coupled with a power plant such as a gas- powered engine.
• genset 902 generates DC power for providing a portable DC power source to charge battery pack 906.
• genset 902 also provides AC power (not shown) directly at an output on genset 902. The depicted combination may be useful for situations when a generator has either a much larger capacity than the intended load(s), and therefore fuel is wasted to continuously run the generator, or has too small a capacity for intended loads.
• genset 902 may be run for many hours to charge battery pack 906, which then supplies power to loads at a higher rate than the genset.
• the battery pack 906 may supply or store power.
• the inverter 908 may convert DC power provided by the genset 902 or battery pack 906 to AC power for powering external devices.
• the charger 910 may be used to charge the battery pack 906 from an external power source.
• the system 900 may provide AC power to external devices directly from the genset 902 or power stored in the battery pack 906 produced by an external source or the genset 902 during off-peak conditions.
• the battery pack 906 may have a similar structure to that described above in FIGs 2- 3B.
• Power cells 912 are of a similar type with uniform electrical characteristics.
• the power cells 912 may be connected in parallel by precision conductors 920-92N to a positive terminal 940 and by precision conductors 930-93N to a negative terminal 942.
• the precision conductors 920-92N have uniform electrical characteristics, such as resistance, inductance, and capacitance and are modeled by the corresponding circuit elements in FIG 9A (e.g. resistor 945, inductor 947, and capacitor 949 model precision conductor 920).
• Precision conductors 930-93N are similarly uniform, and are preferably uniform to conductors 920- 92N.
• the genset 902, inverter 908, and charger 910 are all connected in parallel with the battery pack 906 by conductors 914-919.
• one or more of conductors 914-919 may also have uniform properties to allow parallel simultaneous operation of their connected devices without deleterious cross-currents.
• preferred embodiments match the impedance of conductors on each side of the power components 902, 908, and 910.
• the resistance of conductors 914 and 917 is preferably equal.
• the capacitance and inductance are preferably equal as well. While one inverter 908 and charger 910 is shown, other embodiments may use multiple chargers or inverters, or other such components connected in parallel or series combinations.
• Power produced by the genset 902 may be used to charge a battery pack 906 or be converted by the inverter 908 to AC power for use by other devices (not shown).
• the genset 902 may run continuously, charging the battery pack 906 during times of less-than-maximum use; the battery pack 906 may then supplement the genset during time periods when power use exceeds that available from the genset 902.
• the battery pack 906 may provide backup power to the inverter 908 in case the genset is unavailable due to other constraints such as maintenance, lack of fuel, environmental regulations, etc.
• the charger 910 may be used to charge battery pack 902 from external electricity source. In some instances, it may be desirable or necessary to use an external electricity source such as cases where fuel for the genset 902 may be more expensive that equivalent electricity from the grid.
• the positive terminal 940 is shown in more detail in FIG. 9B and the negative terminal is shown in more detail in FIG. 9C.
• the figures show a circuit diagram that models characteristics of the electrical pathways 950-95N within the terminals (preferably a circular busbar) between the precision conductors 920-92N, 930-93N.
• the electrical characteristics of the pathways 950-95N preferably are uniform within a specified tolerance (e.g. 1 %) to ensure that current flowing to or from each power cell is uniform (see above).
• a specified tolerance e.g. 1 % to ensure that current flowing to or from each power cell is uniform (see above).
• Such matched tolerances provide equal impedance paths to the batteries as seen from power components 902, 908, and 910.
• FIGs. lOA-C illustrate a circuit diagram of a system having a battery pack coupled to a automobile electrical system.
• the system 1000 resembles the system 900 described above in FIGs. 9A-C, but makes use of a vehicle's engine and alternator in place of a genset.
• a system 1000 may be incorporated into a vehicle, for example, such as in a contractor's truck at a construction site or a mobile home at a campground.
• the system 1000 has an alternator 1002, a battery pack 1006, an inverter 1008, and a charger 1010.
• the alternator 1002 may generate DC power when an attached engine is running.
• the battery pack 1006 may supply or store power.
• the inverter 1008 may convert DC power provided by the alternator 1002 or battery pack 1006 to AC power for powering external devices.
• the charger 1010 may be used to charge the battery pack 1006 from an external power source.
• the system 1000 may provide AC power to external devices directly from the alternator 1002 or power stored in the battery pack 1006 produced by an external source or the alternator 1002 during off-peak conditions.
• the battery pack 1006 may have a similar structure to that described above in FIGs 2- 3B.
• Power cells 1012 are of a similar type with uniform electrical characteristics.
• the power cells 1012 may be connected in parallel by precision conductors 1020-1023 to a positive terminal 1040 and by precision conductors 1030-1033 to a negative terminal 1042.
• the precision conductors 1020-1023, 1030-1033 have uniform electrical characteristics, such as resistance, inductance, and capacitance and are modeled by the corresponding circuit elements in FIG 9A (e.g. resistor 1045, inductor 1047, and capacitor 1049 model precision conductor 1020).
• the alternator 1002, inverter 1008, and charger 1010 are all connected in parallel with the battery pack 1006 by conductors 1014-1016 and 1017-1019. These conductors may, in some embodiments, be uniform precision conductors having identical impedances to facilitate parallel operation. As discussed with regard to FIG. 9A, the conductive paths to the various attached power components are preferably matched on the positive and negative sides of each component. Power produced by the alternator 1002 may be used to charge a battery pack 1006 or be converted by the inverter 1008 to AC power for use by other devices (not shown).
• the alternator 1002 may run continuously, charging the battery pack 1006 during times of less-than-maximum use; the battery pack 1006 may then supplement the genset during time periods when power use exceeds that available from the alternator 1002.
• the battery pack 1006 may provide backup power to the inverter 1008 in case the genset is unavailable due to other constraints such as maintenance, lack of fuel, environmental regulations, etc.
• the charger 1010 may be used to charge battery pack 1002 from external electricity source. In some instances, it may be desirable or necessary to use an external electricity source such as cases where fuel for the alternator 1002 may be more expensive that equivalent electricity from the grid.

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