Continuous service energy system for autonomous vehicle

Abstract

A battery storage system (300) is suitable for installation in an electric vehicle (1000) and adapted to supply both a high voltage DC energy source for traction use and a low voltage DC energy source for system use. Multiple discrete battery modules (314) are paired directly with associated multiple discrete DC-DC converter units (330) in 1:1 relation. The multiple discrete battery modules (314) are arranged in series formation with respect to each other. The multiple discrete DC-DC converter units (330) are arranged in parallel formation with respect to each other. A converter management module (340) is in communication with each of the multiple discrete DC-DC converter units (330) to co-ordinate control of the multiple discrete DC-DC converter units and thus charging and discharging of the multiple discrete battery modules (314). The converter management module (340) can be configured to execute various operational modes in the battery storage system (300).

Description

CONTINUOUS SERVICE ENERGY SYSTEM FOR AUTONOMOUS VEHICLETECHNICAL FIELD

[0001] The present invention relates to the field of autonomous vehicles, and more specifically power storage systems suitable for autonomous vehicles.BACKGROUND ART

[0002] Electric vehicles and autonomous vehicles are powered by DC power storage batteries to power essential functions, such as traction, steering, braking, as well as various ancillary functions.

[0003] The capacity of such storage batteries must be significant to power traction motors as well as ancillary demands while also meeting reasonable range expectations before recharging is required.

[0004] Vehicle operation is dependent upon the state of battery storage, for daily operation, and more broadly vehicle integrity relies upon the integrity of battery storage.

[0005] The integrity of battery storage relies on a number of critical factors, including the operational consistency of the battery cell chemistry, the correct functioning of the battery cell charge management circuitry, the integrity of each battery cell group’s physical interconnects, the operation of each battery cell’s charge, discharge and thermal profile being within the cell’s viable temperature range thus avoiding potential thermal runaway issues, and managing design of the array of battery cells into module and pack form to achieve the desired pack output voltage and current for the application being powered. Complex battery cell, module and pack management circuit elements are often present, internally and externally to the pack, to provide the minimum functionality required.

[0006] Conventionally, in vehicle and other applications, a primary battery pack is used as the traction energy source to power the drivetrain of the vehicle, and a secondary battery pack is used to provide energy to power all vehicle systems and controllers, including safety and integrity critical systems across the vehicle or other application.

[0007] One objective of the present invention is to at least attempt to address one or more of these and other existing limitations associated with vehicular powersystems, and provide solutions that address issues such as continued system output integrity in the event of any fault in the main battery energy source, flexibility of system energy requirements, reduction of complexity and hardware costs, and additionally, assists with the control and management of the main battery energy source.SUMMARY OF INVENTION

[0008] The present invention in one aspect relates to a battery storage system suitable for installation in an electric vehicle and adapted to supply both a high voltage DC energy source for traction use supplied via traction voltage terminals and a low voltage DC energy source for system use supplied via system voltage terminals, the battery storage system comprising:

[0009] multiple discrete battery modules paired with multiple discrete DC-DC converter units in 1 :1 relation, such that (i) the multiple discrete battery modules are arranged in series formation with respect to each other, (ii) the multiple discrete DC- DC converter units are arranged in parallel formation with respect to each other;

[0010] traction battery terminals coupled to the series formation of the multiple discrete battery modules;

[0011] system battery terminals coupled to the parallel formation of the multiple discrete DC-DC converter units; and

[0012] a converter management module in communication with each of the multiple discrete DC-DC converter units to co-ordinate control of the multiple discrete DC-DC converter units.

[0013] Advantageously, the described battery storage system avoids the need for a separate system battery in addition to a conventional traction battery. The described inventive arrangement of a battery storage system permits power supply as required at differentiated voltages, namely a traction voltage and a system voltage.

[0014] The modularised construction of power storage across multiple discrete battery modules, and the DC-DC converter function across multiple discrete DC-DC converter units can achieve cost and weight benefits compared to a monolithic DC- DC converter unit and a monolithic battery unit. Furthermore, individual of the multiple discrete battery modules and the multiple discrete DC-DC converter units can be replaced as needed.

[0015] Architectures that rely on traction batteries and system batteries as separate components can be reconfigured to use in effect a traction battery alone, and in effect source system power from a traction battery, thus avoiding the need for a system battery distinct from a traction battery.

[0016] As the converter management module is in communication with each of the multiple discrete DC-DC converter units each of the multiple discrete battery modules can be charged or discharged as required through control of a paired instance of the multiple discrete DC-DC converter units. This permits the configuration of the various inventive operational modes made possible by the architecture of the described battery storage system.

[0017] Advantageously, the converter management module can be configured to operate the DC-DC converter units in various operational modes that mitigate faults for uninterrupted and reliable operation, increase the efficiency of individual battery modules to reduce wear of the multiple discrete battery modules, balance the multiple discrete battery modules to accommodate any degradation and manufacturing variances between the multiple discrete battery modules, and precondition the multiple discrete battery modules for charging also to reduce wear of the multiple discrete battery modules.

[0018] The present invention in further aspects relate to various methods of operating a battery storage system according to the abovementioned aspect of the present invention in accordance with the various operational modes described herein.

[0019] These particular operational modes are referred to as (i) a fault mitigation mode in response to a fault detected with one of the multiple discrete battery modules or a multiple discrete DC-DC converter unit with which the battery module is paired, (ii) a peak efficiency mode to increase an efficiency at which the system power is extracted from the multiple discrete battery modules, (iii) a battery module balancing mode in which the multiple discrete battery modules are balanced, and (iv) a battery module preconditioning mode in which the multiple discrete battery modules are preconditioned for charging.

[0020] Traction power demands are supplied at a traction voltage, and system power demands are at a system voltage. Traction voltage (for example 400V) is typically higher than system voltage (for example 12, 24, 48V) though the describedbattery storage system can be arranged to accommodate traction voltage and system voltage at different or multiple voltage levels if required.

[0021] Using multiple discrete DC-DC converter units paired or associated with each of the multiple discrete battery modules replaces the need for monolithic DC- DC converters. This architecture presents the opportunity for weight saving as using monolithic DC-DC converters require casings and heat sinks that represent increased weight over the cumulative weight of distributed, discrete DC-DC converter units.

[0022] The multiple discrete DC-DC converter units can be unidirectional or bidirectional in design. The described embodiments can be implemented using multiple discrete DC-DC converter units that are unidirectional, though the described battery module preconditioning mode requires bidirectional functionality of the multiple discrete DC-DC converter units. The multiple discrete DC-DC converter units may also operate in a step up mode or step down mode as required to achieve required system voltage.

[0023] Many other advantages exist, as will be evident to those skilled in the relevant art.BRIEF DESCRIPTION OF DRAWINGS

[0024] FIG 1 is a schematic diagram of a battery storage system according to an embodiment of the present invention, when installed in an autonomous vehicle.

[0025] FIG 2 is a schematic diagram of the battery storage system of FIG 1.

[0026] FIG 3 is a schematic diagram of battery modules comprising the battery storage system of FIGS 1 and 2.

[0027] FIG 4 is a schematic diagram of the battery storage system of FIGS 1 and 2, and is similar to FIG 2 though with further detail presented.

[0028] FIG 5 is a sequence diagram of a process in which the battery storage system presented in FIGS 1-4 handles a fault in a module or DC-DC converter unit of the battery storage system.

[0029] FIG 6 are sequence diagrams of a process in which the battery storage system operates in a peak efficiency mode. FIG 6A is a sequence diagram in overview of a process in overview in which the battery storage system that operates in a peak efficiency mode. FIGS 6B-6D is a sequence diagram in extended detail ofthe same process in which the battery storage system that operates in a peak efficiency mode.

[0030] FIG 7 are sequence diagrams of a process in which the battery storage system presented in FIGS 1-4 operates in a battery module voltage operation mode to balance modules according to module voltage. FIG 7A-7B is a sequence diagram of a process in which the battery storage system presented in FIGS 1-4 operates in a battery module voltage operation mode to balance modules according to module voltage when not all modules are powered on. FIG 7C-7D is a sequence diagram of a process in which the battery storage system presented in FIGS 1-4 operates in a battery module voltage operation mode to balance modules according to battery module voltage when all battery modules are powered on.

[0031] FIG 8 is a sequence diagram of a process in which the battery storage system presented in FIGS 1-4 operates in a battery preconditioning mode using the bi-directionality of the DC-DC converter units associated with battery modules, depicted across FIGS 8A-8C.DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0032] FIG 1 is a schematic diagram of an autonomous vehicle 1000 having a battery storage system (BSS) 300 installed in the autonomous vehicle 1000.

[0033] The BSS 300 is depicted as comprising a traction battery A (TBAT A) 310, a traction battery B (TBAT B) 320, a DC-DC converter unit (DCU) 330 separately connected directly to TBAT A 310 and TBAT B 320 as depicted. TBAT A 310 and TBAT B 320 provide a reserve of electric power storage for the autonomous vehicle 1000.

[0034] A battery management system A (BMS A) 312 is connected to TBAT A 310, and a separate battery management system B (BMS B) 322 is connected to TBAT B 320. A converter management module (CMM) 340 is connected directly to the DCU 330. CMM 340 manages operation of DCU 330. CMM 340 is connected to CCU 110 and under control of CCU 110.

[0035] Within the autonomous vehicle 1000, the BSS 300 is connected to a system battery unit (SBU) 200. The SBU 200 is connected to the BSS 300 by separate connections to the BMS A 312, BMS B 322, and the DCU 330. SBU 200communicates with BMS A 312, BMS B 322, which in turn monitors operation of their respective traction batteries TBAT A 310, TBAT B 320.

[0036] The SBU 200 is also connected to a body control unit (BCU) 140 and an autonomous driving system (ADS) 120 of the autonomous vehicle 1000.

[0037] The BSS 300 is also attached to junction box 350. Junction box 350 connects to TBAT A 310 and TBAT B 320. Junction box 350 is connected to motor control unit (MCU) 160, and MCU 160 is in turn connected to motor 180. Junction box 350 receives power from TBAT A 310 and TBAT B 320 and directs that power to MCU 160. MCU 160 passes power to motor 180 as required. Dual traction batteries in the form of TBAT A 310 and TBAT B 320 are provided for redundancy. Typically, TBAT A 310 is ordinarily used to power motor 180, and the power source is switched to TBAT B 320 in the event of fault detected relating to TBAT A 310. A single battery bank can alternatively be used if required.

[0038] A combination of two or four pairs of MCU 160 and motor 180 are used to control and direct power to typically the rear wheels (not shown) or all wheels (not shown) of the autonomous vehicle 1000. A single MCU 160 and motor 180 is referenced in the description which follows for convenience.

[0039] Motor 180 is an edge device which operates under control of edge control unit MCU 160.

[0040] Junction box 350 receives power from the TBAT A 310 or TBAT B 320, or both and directs that traction power to MCU 160.

[0041] TBAT A 310 and TBAT B 320 accordingly supply DC power to motor 180, as depicted on one side of FIG 1 at left, and described above. At the other side of FIG 1 at right, DCU 330 of BSS 300 converts the DC power of TBAT A 310 and TBAT B 320 to a different voltage for use by SBU 200.

[0042] The voltage output of BSS 300 directly from TBAT A 310 and TBAT B 320 is typically a higher voltage for use by motor 180. Conversely, the voltage output of BSS 300 from DCU 330 accordingly is typically a lower voltage for use by SBU 200, though this need not always be the case.

[0043] The higher voltage and lower voltage output from BSS 300 are terms used for convenience, indicating only that the voltages are typically higher and lower relative to each other, reflecting use of traction voltage in a traction motor 180,typically a non-limiting but indicative range of 300V-800V, compared to a system voltage, typically a nominal 12V for use in system applications in autonomous vehicle 1000.

[0044] SBU 200 receives low voltage power from BSS 300, and supplies that low power voltage power to BCU 140, ADS 120 as well various other edge control units (not shown) and modules (not shown) of the autonomous vehicle 1000.

[0045] FIGS 2 and 3 depict aspects of the BSS 300 in further detail.

[0046] BSS 300 as depicted in FIG 2 omits BMS A 312, BMS B 322 and CMM 340. BSS 300 depicts the integration of TBAT A 310 (or, interchangeably TBAT B 320) and DCU 330. Only one of the dual redundancy traction battery modules 310, 320 is shown as typically only one is in operation at a given time. BSS 300 comprises a discrete series of multiple battery modules 314 connected directly with a matching discrete series of multiple DCU 330.

[0047] FIG 3 depicts an individual battery module 314 of FIG 2. Module 314 has output terminals 315. Each module 314 comprises a discrete series of battery cells 316 connected in series formation with the negative terminal of one cell 316 connected to the positive terminal of the next cell 316. As indicated in FIG 3, each cell 316 has a nominal voltage of 3.7V, by way of non-limiting but indicative example. The battery module 314 of FIG 3 by way of example has 12 cells 316 connected in series formation, so that the nominal voltage across the terminals of the module 314 is around a nominal 44V.

[0048] FIG 2 for clarity omits the polarity of the modules 314 and DCU 330. The voltage from each of the battery modules 314 is 44V, which is used in the example of FIG 3. As depicted, BSS 300 has two output voltages, a high voltage or traction voltage (440V) and a low voltage or system voltage (12V). The high voltage is derived directly from battery modules 314, of which there are 10 connected in the example of FIG 2. Each of the multiple discrete battery modules 314 is connected to each other in series formation, as is more readily apparent from FIG 4 described below. The high voltage is additive of the separate discrete voltages of each of the modules 314, of which there are 10, and hence the cumulative voltage is a nominal 440V (that is, 10 x 44V).

[0049] Separately, each of the multiple discrete battery modules 314 is connected or paired to an associated instance of the multiple discrete DCU 330. The pairing ofrespective modules 314 and DCU 330 can be characterised as being a 1 :1 pairing relationship as depicted.

[0050] Preferably the module 314 and DCU 330 are integrated for a small form factor, though this is not essential. The DCU 330 receives an output of 44V from the module 314 and steps down the voltage to a nominal 12V output.

[0051] The output of each DCU 330 is connected in parallel, and thus is at 12V which represents the low voltage output of BSS 300. Referring back to FIG 1 , the low voltage output from BSS 300 supplies SBU 200, while the high voltage output from BSS 300 supplies junction box 350.

[0052] FIG 2 in summary depicts an arrangement in which the BSS 300 comprises discrete battery modules 314 and associated discrete DCU 330. The battery modules 314 and DCU 330 are preferably of integrated construction. The modularised layout permits simultaneously (i) a high voltage output from the BSS 300 by connecting the direct output of the modules 314 in series formation and (ii) a low voltage output from the BSS 300 by connecting the output of the modules 314 through the DCU 330 in parallel formation.

[0053] This arrangement is particularly suitable for use in the autonomous vehicle 1000, and other electric vehicles, as high voltage output is suitable from traction motors (in this case, motor 180), and low voltage output is suitable for use as a system voltage used by various subsystems other than such traction motors (in this case, for example BCU 140, ADS 120).

[0054] This arrangement further permits use of a single battery 310, 320 to power traction motors as well as system voltage accessories, rather than use separate traction batteries and system batteries. Dual redundancy traction batteries 310, 320 are still used in the example embodiment described and depicted, though a separate and dedicated system battery operating a low voltage is omitted, and system voltage power can be supplied by batteries 310, 320 that are configured to supply both traction power at a traction voltage (high voltage) and system power at a system voltage (low voltage).

[0055] An advantage of using multiple discrete battery modules 314 is that the BSS 300 is robust to failure of any given instance of the multiple discrete modules 314. Additionally, an individual module 314 can be diagnosed as faulty and replaced. System power can be maintained, though a loss of traction power will result. TheBSS 300 can be engineered to permit the faulty module 314 and / or DCU 330 can be replaced as required without requiring the entire battery 310, 320.

[0056] FIG 4 is similar to FIG 2, though with additional detail depicted. As is also evident in FIG 2, the multiple discrete battery modules 314 are paired with the multiple discrete DCU 330 in 1 :1 relation. The multiple discrete battery modules 314 are connected in series formation with respect to each other, and the multiple discrete DCU 330 are connected in parallel with respect to each other. As a consequence of the 1 :1 pairing of each module 314 with its matching DCU 330, output terminals of the modules 314 connect with input terminals of the paired DCU 330.

[0057] and the series connection of the modules 314 and parallel connection

[0058] The BSS 300 is depicted with both positive and negative terminals as indicated. The polarity of the terminals depicted in FIG 4 makes it clearer that output traction voltage at 440V from BSS 300 results from connection to the series formation of the multiple discrete battery modules 314 (or, alternatively series topology) with respect to each other. Modules 314 have output terminals 315 of oppositive polarity. Running down the bank of modules 314 depicted on the left side of the BSS 300, on the left, negative terminals of one module 314 connect to positive terminals of the successive module 314. This pattern continues running up the bank of modules 314 depicted on the right side of the BSS 300.

[0059] The positive terminal of the traction voltage terminals 316 is connected to the positive terminal of the first module 314 depicted at upper left, and the negative voltage of the traction voltage terminals 316 is connected to the negative terminal of the last module 314 depicted at upper right.

[0060] Conversely, the system voltage terminals 334 (12V) from BSS 300 is taken from a system power bus 333 depicted as extending down the centre of the BSS 300. Each DCU 330 is paired with module 314 by connection of output terminals 315 of module 314 with input terminals 331 of DCU 330, which outputs a low voltage at output terminals 332 of DCU 330. This is represented as a nominal 12V in this embodiment. The voltage input to the DCU 330 is represented as 44V, as supplied from the module 314.

[0061] The output terminals 332 of each DCU 330 feeds to the system power bus 333. The multiple discrete DCU 330 are connected in parallel formation (or,alternatively parallel topology) with respect to each other. Accordingly system voltage terminals 334 provides power at 12V. Output terminals 332 of DCU 330 are arranged in parallel formation with respect to each other.

[0062] The DCU 330 may output at a different voltage value, or multiple voltage levels. Typical values for system voltage terminals 334 can be expected to be a nominal 12V, 24V or 48V. Accessories of the vehicle 1000 may predominantly operate at and require 12V, though some subsystems may operate at 24V or 48V as is familiar in the automotive and trucking industries.

[0063] Furthermore, CMM 340 is depicted connecting to each of the DCU 330. CMM 340 can fetch operating parameters of each of the DCU 330 and control operation of each of the individual DCU 330 to, for example, adjust current draw amongst various other functions. BMS 312, 322 is depicted connecting to each of the modules 314. BMS 312, 322 can fetch operating parameters of the operation of the each of the modules 314 and operates in conjunction with the CMM 340 and CCU 110 to deliver desirable operating modes of the BSS 300 as described below.Fault mitigation mode

[0064] FIG 5 is a sequence diagram depicting an example of operation of a fault mitigation mode in the BSS 300.

[0065] The individual DCU 330 are not collectively referenced but instead denoted DCU 1 330 through to DCU 10 330 in FIG 5 for ease of reference and understanding. The same schema is used in the examples of other modes described below with reference to FIGS 6-8.

[0066] This example denotes a fault detected in DCU 2 330.

[0067] Faults in DCU 330 are many and various, and by way of illustrative example comprise categories such as: input over current, input under voltage, output over current, output over voltage, thermal event.

[0068] Since the output of all the DCU 330 are connected in parallel, load demand is shared between all the active DCU 330. Under most typical operating conditions, a fault in a single DCU 330 should not prevent BSS 300 from supplying full output power to system voltage terminals 334.

[0069] Under a fault condition in a DCU 330, that DCU 330 self-isolates preserving low voltage energy at the terminals 334.

[0070] Modules 314 input power to their respective DCU 330 in step 502 depicted in FIG 5. Each of the DCU 330 reports an input-output voltage and current to the CMM 340 in step 504. CMM 340 performs a power proportionality calculation in step 506 based upon the input-output voltage and current reported by DCU 330 in step 504. The power proportionality calculation of step 506 profiles the relative contribution of each DCU 330.

[0071] CMM 340 also performs a fault diagnostics procedure in step 508 based upon the output of the power proportionality calculation of step 506. The fault diagnostic procedures uses heuristic measures to identify which of the DCU 330, namely DCU 1-10 330 is at fault. A message is accordingly sent from CMM 340 to, in this instance, DCU 2 330 commanding DCU 2 330 to self-isolate from the shared system power bus 333 in step 510.

[0072] DCU 2 330 receives this command and self-isolates in step 512. DCU 2 330 then returns an acknowledgement to CMM 340 in step 514 following self-isolation in step 512.

[0073] CMM 340 following the fault diagnostic procedure of step 508 reports a fault message to CCU 110 regarding the fault identified in step 508. CCU 110 performs a fault management procedure in step 518, and returns an acknowledgement to CMM 340 in step 520.

[0074] CMM 340 performs a DCU load share proportionality calculation in step 522. The DCU load share proportionality calculation of step 522 determines the output current share for each of the remaining DCU 330, namely DCU 1-10 330, except DCU 2 330 which is now isolated. CMM 340 transmits the output current share determined in step 522 to the respective DCU 330 in step 524. The DCU 330 then return the new input-output voltage and current in step 526, which is similar to step 504 described above.Peak efficiency mode

[0075] FIG 6 are sequence diagrams of a process in which the BSS 300 operates in a peak efficiency mode.

[0076] Peak operational efficiency for any DCU 330 occurs when the system power supplied is around a peak efficiency band of 85%-95% of rated capacity of the DCU 330. Accordingly, the architecture of the BSS 300 means that for a given load, only those DCU 330 as necessary are activated to supply a given power demand at ornear this peak efficiency band. A DCU 330 may be required to operate outside its peak efficiency band to meet prevailing demand for system power, though overall the number of DCU 330 operating outside its peak efficiency band is minimised. Remaining DCU 330 are isolated, with no current draw. Thus this avoids sharing demand for system power equally amongst DCU 330, which in most circumstances will result in the DCU 330 not operating with their peak efficiency band.

[0077] Considering that all the loads (before they are turned on) are known to CCU 110 and the current request information is fed to the CMM 340 in advance (feed forward mode), CMM 340 can turn on additional DCU 330 required for the load demand. Once the requested load demand is reduced by the CCU 110, the CMM 340 can turn off the additional DCU 330 and revert to the minimum number of DCU 330 required.

[0078] As the current demand increases more DCU 330 are turned on. Conversely, when the current demand decreases the CMM 340 commands particular DCU 330 to turn off otherwise and DCU 330 start to fall out of the desired peak efficiency band.

[0079] FIG 6A is a sequence diagram in overview of a process in overview in which the BSS 300 operates in a peak efficiency mode.

[0080] CCU 110 transmits a load current request to CMM 340. CMM 340 then performs a load calculation procedure in step 604, and then returns an acknowledgement to the CCU 110 in step 606. CMM 340 then determines in step 608 which DCU 330 are required for peak efficiency for the target load requested in step 602.

[0081] FIGS 6B-6D is a sequence diagram in extended detail of the same process of FIG 6A in which the BSS 300 operates in a peak efficiency mode.

[0082] Starting at FIG 6B, steps 602-610 are shared with those of FIG 6A described above. The CMM 340 activates an output current share to DCU 10 330 in step 612. The corresponding module 314 delivers input power to DCU 10 330 in step 613, and DCU 10 330 in step 614 reports input-output voltage and current to CMM 340.

[0083] Continuing on to FIG 6C, CMM 340 transmits a not active message to DCU 2 330 in step 616. Corresponding module 314 delivers input power to DCU 2 330 instep 613. DCU 2 330 in step 618 returns CMM 340 an acknowledgement of the not active message of step 616.

[0084] As depicted the same steps 612-614 described above for DCU 10 330 also occur for DCU 1 330.

[0085] CMM 340 then performs a power proportionality calculation in step 624 based upon the input-output voltage and current reported by DCU 330 in step 614.

[0086] CMM 340 then performs a fault diagnostics procedure in step 626. As the DCU 2 330 failed to stop consuming input power from module 314, CMM 340 commands DCU 2 330 to self-isolate in step 628, and DCU 2 330 returns an acknowledgement in step 630. Meanwhile, CMM 340 sends a fault message to CCU 110 in step 632.

[0087] CCU 110 executes a fault management process in step 634, and returns an acknowledgement to CMM 340 in step 636.

[0088] CMM 340 then executes a DCU load share proportionality calculation in step 638

[0089] Continuing on to FIG 6D, CMM 340 transmits an output current share in DCU 10 330 in step 640, and DCU 10 330 reports the input-output voltage and current at DCU 10 330 to CMM 340 in step 642. The same exchange occurs with DCU 1 330 as depicted.Module balancing mode

[0090] FIG 7 are sequence diagrams of a process in which the BSS 300 of FIGS 1-4 operates in a battery module voltage operation mode to balance modules according to module voltage.

[0091] Under load conditions, due to manufacturing tolerances and internal chemistry, the internal resistance of modules 314 and cells 316 is not the same. When load current passes through the cells 316, there may occur a voltage imbalance between different modules 314.

[0092] Over time the imbalance between the voltages of different modules 314 may become significant and reductions or increases in output current may be necessary from specific modules 314 to maintain a similar output voltage across all modules 314.

[0093] When not all DCU 330 are active, as depicted in FIGS 7A-7B, current draw from a module 314 that has a lower voltage is reduced and in effect transferring from that module 314 to a different module 314 that has a higher voltage, thereby balancing modules 314.

[0094] DCU 330 report their input and output voltage and current to CMM 340. CMM 340 determines how current draw is distributed between modules 314.

[0095] It can be expected that the voltages of the modules 314 will over time become the same following this approach.

[0096] When all the available DCU 330 are active (that is, turned on and delivering power), as depicted in FIGS 7C-7D, and thus no reserve or fallback DCU 330 is available in reserve, a compensatory reduction in current is achieved through changing the output current of individual DCU 330.

[0097] This is done by CMM 340 sending the target load current and then the DCU 330 accurately changing its output terminal voltage resulting in reduction of output current from that DCU 330. This results in other DCU 330 now providing additional current.

[0098] When current reduction from more than one DCU 330 is required, CMM 340 computes the required current share from each DCU 330 to be proportional to their input terminal voltage (module voltage).

[0099] First, FIG 7A-7B is a sequence diagram presenting this module balancing mode in which not all modules 314 of BSS 300 are powered on.

[0100] First DCU 1 330 is not active and no power is being drawn from module 314 in step 702. DCU 1 330 sends that message to CMM 340 in step 704.

[0101] Second, DCU 2 330 receives input power from corresponding module 314 in step 706, and then reports its input-output voltage and current to CMM 340 in step 708. A similar sequence happens for other DCU 330, including DCU 10 330 as depicted in FIG 7A.

[0102] CMM 340 executes a power proportionality calculation in step 710. CMM 340 in step 718 then identifies which modules 314 need to be turned off and replaced with modules 314 of a higher output voltage or based upon thermal readings.

[0103] CMM 340 then transmits operational data to CCU 110 in step 714, and CCU 110 returns an acknowledgement to CMM 340 in step 716.

[0104] CMM 340 then transmits an output current share to DCll 330 in step 724, and DCU 330 returns an acknowledgment in step 728. Corresponding modules 314 meanwhile deliver input power to DCU 330 in step 726. Steps 724-726 are depicted as occurring for DCU 1 , 10 330 in FIG 7B. As regards DCU 2 330, CMM 340 transmits a deactivation command to DCU 2 330 in step 730, and DCU 2 330 returns an acknowledgement to CMM 340 in step 734. DCU 2 330 meanwhile stops consuming power from its paired module 314 as depicted in step 732.

[0105] Then, CMM 340 again sends operational data in step 720 to CCU 110 and receives in reply an acknowledgement from CCU 110 in step 722.

[0106] FIG 7C-7D is a sequence diagram of a process in which the BSS 300 presented in FIGS 1-4 operates in a battery module voltage operation mode to balance modules according to the voltage of the modules 314 when all battery modules 314 are powered on.

[0107] Modules 314 deliver input power to DCU 330 as depicted for DCU 1-10 330 in step 706, and DCU 330 report input-output voltage and current in step 708 to CMM 340. CMM 340 executes a power proportionality calculation in step 710, and step 730 identifies the proportionality of module voltage imbalance.

[0108] Operational data is transmitted from CMM 340 to CCU 110 in step 732, and an acknowledgement returned from CCU 110 to CMM 340 in step 734.

[0109] CMM 340 in step 736 determines DCU 330 output in proportion to output voltages of modules 314 as reported in step 708.

[0110] Again, operational data is sent to CCU 110 from CMM 340 in step 732, with an acknowledgement returned in step 734.

[0111] CMM 340 then commands an output current share to each DCU 330 in step 738. Each DCU 330 reports its input-output voltage and current in step 742, meanwhile each corresponding module 314 delivers its input power to DCU 330 in step 740

[0112] Operational data is then again sent to CCU 110 from CMM 340 in step 732, with an acknowledgement returned in step 734.Battery preconditioning

[0113] FIG 8 is a sequence diagram of a process in which the BSS 300 presented in FIGS 1-4 operates in a battery preconditioning mode using the bi-directionality of the DCU 330 associated with modules 314.

[0114] DCU 330 are advantageously bidirectional, which permits DCU 330 to be used to pre-condition the modules 314 prior to charging or use. DCU 330 generate heat when in use— and these heat losses can be repurposed through diversion of this heat energy to the modules 314 to raise the temperature of the modules 314 to a level that is optimal for charging, or at least increase the efficiency of charging.

[0115] Along with normal loading on the system power bus 333, additional power can be generated by requesting one or more DCU 330 to charge the modules 314 to which the DCU 330 are paired. This means that the rest of the DCU 330 are converting more power and generating more heat though their paired modules 314 discharging. The DCU 330 that are being used for charging modules 314 also generate heat.

[0116] The roles reverse periodically between charging and discharging. The DCU 330 that were previously feeding power the system power bus 333, now feeds from the system power bus 333. DCU 330 that were previously charging their paired battery module 314, now take power from their paired module 314 and feed into the system power bus 333. This reversal of role tends to keep all the modules 314 at a relatively similar state of charge.

[0117] By circulating the power within the BSS 300, when the required preconditioning temperature is met DCU 330 can revert to normal operation.

[0118] Referring to FIG 8A, a charge mode request is sent from CCU 110 to CMM 340 in step 802. Module thermal data is collected by CMM 340 in step 806. This comprises thermal data requests being sent from CMM 340 to DCU 330 in step 808. The DCU 330 relay a temperature sensing request to their paired module 314 in step 810. Module 314 returns a temperature reading in reply in step 812.

[0119] The DCU 330 are then able to return thermal data to the CMM 340 regarding the modules 314 in step 814.

[0120] The CMM 340 can then report battery thermal data to the CCU 110 in step 816. The CCU 110 then executes preconditioning logic 818 that decides upon preconditioning heat requirements, and which modules 314 should be heated. CCU110 commands CMM 340 to activate preconditioning in step 820. CMM 340 returns an acknowledgment to CCU 110 in step 822.

[0121] CMM 340 cycles a negative power request from the module 314 with the lower temperature first in step 824. Continuing to FIG 8B, CMM 340 commands an output power share to DCU 330 in step 826. Modules 314 accordingly deliver input power to the DCU 330 in step 828 and the DCU 330 transmit thermal data and input-output voltage and current to the CMM 340 in step 830.

[0122] As depicted, this occurs specifically for DCU 1 , 10 330. As regards DCU 2 330, CMM 340 sends a maximum negative power request to DCU 2 330 in step 832. DCU 2 330 outputs power to its paired module 314 in step 834 and returns thermal data and input-output voltage and current to CMM 340 in step 836.Accordingly this module 314 is warmed as a consequence of receiving power during recharging.

[0123] CMM 340 then repeats the steps 816-824 described above.

[0124] Then, CMM 340 repeats the steps 826-836 described above. Now though DCU 10 330 receives the maximum negative power request of step 832 as CMM 340 has determined it to be the coldest of the modules 314 in step 824. Power is drawn from DCU 1 , 2 330 as it was previously from DCU 1 ,10 330.

[0125] CMM 340 then repeats the steps 816-824 described above, and preconditioning is completed.

[0126] The various operational modes described above are implemented in illustrative embodiments, the details of which may be varied according to requirements.

Claims

CLAIMS1 . A battery storage system suitable for installation in an electric vehicle and adapted to supply both a high voltage DC energy source for traction use supplied via traction voltage terminals and a low voltage DC energy source for system use supplied via system voltage terminals, the battery storage system comprising: multiple discrete battery modules paired with multiple discrete DC-DC converter units in 1 :1 relation, such that (i) the multiple discrete battery modules are arranged in series formation with respect to each other, (ii) the multiple discrete DC-DC converter units are arranged in parallel formation with respect to each other; traction battery terminals coupled to the series formation of the multiple discrete battery modules; system battery terminals coupled to the parallel formation of the multiple discrete DC-DC converter units; and a converter management module in communication with each of the multiple discrete DC-DC converter units to co-ordinate control of the multiple discrete DC-DC converter units.

2. A battery storage system according to claim 1 , wherein the multiple discrete DC-DC converter units enable bi-directional operation to permit discharging and charging of the multiple discrete battery modules paired to the multiple discrete DC-DC converter units.

3. A battery storage system according to claim 1 or 2, wherein the converter management module is configured to execute one or more of (i) a fault mitigation mode in response to a fault detected with one of the multiple discrete DC-DC converter units, (ii) a peak efficiency mode to increase an efficiency at which the multiple discrete battery modules operate, (iii) a battery module balancing mode in the multiple discrete battery modules arebalanced, and (iv) a battery module preconditioning mode in which the battery modules are preconditioned for charging.

4. A battery storage system according to claim 3, wherein the fault mitigation mode comprises a step performed by the converter management module of commanding one of the multiple discrete DC-DC converter units to selfisolate when a fault is detected with the DC-DC converter module or its paired battery module.

5. A battery storage system according to claim 3, wherein the peak efficiency mode comprises steps performed by the converter management module of activating and deactivating selected multiple discrete DC-DC converter units to increase the number of the multiple discrete battery modules and their paired multiple discrete DC-DC converter units that operate within a high efficiency band.

6. A battery storage system according to claim 3, wherein the battery module balancing mode comprises steps performed by the converter management module of selectively deactivating and activating one or more of the multiple discrete DC-DC converter units in favour of the multiple discrete DC-DC converter units having higher input voltages received from the multiple discrete battery modules paired with the multiple discrete DC-DC converter units.

7. A battery storage system according to claim 3, wherein the battery module balancing mode comprises steps performed by the converter management module of commanding the multiple discrete DC-DC converter units to adjust current input levels in proportion to the observed input voltages received from the multiple discrete battery modules paired to the multiple discrete DC-DC converter units.

8. A battery storage system according to claim 3, wherein the battery module preconditioning mode comprises steps performed by the converter management module of commanding the multiple discrete DC-DC converter units to circulate energy between the multiple discrete battery modules with which the multiple discrete DC-DC converter units are paired from themultiple discrete battery modules having higher observed thermal readings to the multiple discrete battery modules having lower observed thermal readings.

Images