U.S. patent application number 15/876896 was filed with the patent office on 2018-05-24 for battery management of multi-cell batteries.
The applicant listed for this patent is Antonio Trigiani. Invention is credited to Antonio Trigiani.
Application Number | 20180145519 15/876896 |
Document ID | / |
Family ID | 40720924 |
Filed Date | 2018-05-24 |
United States Patent
Application |
20180145519 |
Kind Code |
A1 |
Trigiani; Antonio |
May 24, 2018 |
Battery management of multi-cell batteries
Abstract
Apparatus for a modular battery management system for a battery
having a plurality of cells. The system includes interchangeable
chargers each associated with a slave module. The chargers are
connected to each cell and a master module controlling the system.
All the modules receive power through a transfer switch that
selectively switches between external sources and the battery. With
the transfer switch connecting the battery to the charger modules,
each charger operates independently to maintain its associated
cell. Each charger is electrically isolated from the other
chargers. The external sources provide capacity information used by
the master module. The slave modules are autonomous and shut down
the battery and disconnect the module when a critical parameter of
the cell is reached. When the battery is in service and a cell
parameter approaches the critical level, the master controller
instructs the corresponding slave module to charge the cell using
battery power.
Inventors: |
Trigiani; Antonio; (Bristol,
TN) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Trigiani; Antonio |
Bristol |
TN |
US |
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|
Family ID: |
40720924 |
Appl. No.: |
15/876896 |
Filed: |
January 22, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14042245 |
Sep 30, 2013 |
9876367 |
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15876896 |
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12331717 |
Dec 10, 2008 |
8547065 |
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14042245 |
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61012907 |
Dec 11, 2007 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y10T 307/469 20150401;
Y02E 60/10 20130101; H02J 7/0026 20130101; Y10T 307/461 20150401;
H02J 7/0014 20130101; Y02T 10/70 20130101; H02J 7/0018
20130101 |
International
Class: |
H02J 7/00 20060101
H02J007/00 |
Claims
1. An apparatus for managing a battery with a plurality of cells,
said apparatus comprising: a plurality of chargers, each one of
said plurality of chargers having an output configured to be
electrically connected to at least one of the plurality of cells,
each one of said plurality of chargers configured to charge said at
least one of the plurality of cells, each one of said plurality of
chargers having an input selectively connectable to the battery;
and a plurality of isolation circuits, each one of said plurality
of isolation circuits associated with a corresponding one of said
plurality of chargers, wherein each one of said plurality of
isolation circuits electrically isolates the battery from said at
least one of the plurality of cells associated with said
corresponding one of said plurality of chargers.
2. The apparatus of claim 1 further including a transfer switch,
said transfer switch operatively connected to said plurality of
chargers, said transfer switch having a first state wherein an
external power source is connected to power said plurality of
chargers, said transfer switch having a second state wherein the
battery is connected to provide power to said plurality of
chargers.
3. The apparatus of claim 1 wherein each one of said plurality of
chargers is energized to charge an associated cell after an
associated cell monitoring circuit detects a first operating
parameter with a specified value and said transfer switch is in
said second state.
4. The apparatus of claim 1 further including a first load
connection configured to electrically connect a first load across
the battery and a second load connection configured to electrically
connect a second load across a portion of the battery, and said
portion of the battery defined as at least one and less than all of
the plurality of cells of the battery, wherein said portion of the
battery is maintained by at least one of said plurality of
chargers.
5. The apparatus of claim 1 further including a plurality of
modules, each one of said plurality of modules including a
corresponding one of said plurality of chargers, each one of said
plurality of modules including a cell monitoring circuit and a
module disconnect switch, wherein each said module disconnect
switch operates to isolate said at least one of the plurality of
cells from said corresponding one of said plurality of chargers
when said cell monitoring circuit determines said at least one of
the plurality of cells has a first operating parameter outside an
acceptable range.
6. The apparatus of claim 5 wherein each one of said plurality of
modules is initialized with a unique identification based on an
identification of said at least one of the plurality of cells.
7. An apparatus for managing a battery having a plurality of cells
that are series connected, said apparatus comprising: a first
charger, said first charger having a first charger output
electrically connectable to a first set of cells including at least
one of the plurality of cells, said first charger having a first
charger input electrically connectable to the battery; and a second
charger, said second charger having a second charger output
electrically connectable to a second set of cells including at
least one of the plurality of cells, said first set of cells and
said second set of cells being disjoint sets, said second charger
having a second charger input electrically connectable to the
battery.
8. The apparatus of claim 7 further including a first isolation
circuit associated with said first charger wherein the battery is
electrically isolated from said first set of cells, and further
including a second isolation circuit associated with said second
charger wherein said the battery is electrically isolated from said
second set of cells.
9. The apparatus of claim 7 further including a first isolation
circuit associated with said first charger wherein said first
charger has said first charger output electrically isolated from
said first charger input, and further including a second isolation
circuit associated with said second charger wherein said second
charger has said second charger output electrically isolated from
said second charger input.
10. The apparatus of claim 7 further including a transfer switch,
said transfer switch operatively connected to said first charger
and said second charger, said transfer switch having a first state
wherein an external power source is connected to provide power to
said first charger and said second charger, said transfer switch
having a second state wherein the battery is connected to provide
power to said first charger and said second charger.
11. The apparatus of claim 10 wherein said first charger is
energized to charge said first set of cells after a cell monitoring
circuit associated with said first charger detects a first
operating parameter with a specified value and said transfer switch
is in said second state.
12. The apparatus of claim 10 wherein said first charger is
energized to charge said first set of cells after a cell monitoring
circuit associated with said first charger detects a first
operating parameter with a specified value and said transfer switch
is in said second state, and said second charger is energized to
charge said second set of cells after a cell monitoring circuit
associated with said second charger detects a second operating
parameter with a specified value and said transfer switch is in
said second state.
13. The apparatus of claim 7 further including a first module and a
second module, said first module including said first charger, said
second module including said second charger.
14. The apparatus of claim 13 wherein each one of said first module
and said second module further includes a cell monitoring circuit
and a module disconnect switch, wherein said first module
disconnect switch in said first module operates to isolate said
first set of cells from said first module when said cell monitoring
circuit determines said first set of cells has a first operating
parameter outside an acceptable range, and said second module
disconnect switch in said second module operates to isolate said
second set of cells from said second module when said cell
monitoring circuit determines said second set of cells has a second
operating parameter outside an acceptable range.
15. The apparatus of claim 7 further including a first load
connection configured to electrically connect a first load across
the battery and a second load connection configured to electrically
connect a second load across a portion of the battery, said portion
of the battery defined as at least one and less than all of the
plurality of cells of the battery, wherein said portion of the
battery is maintained by at least one of said first charger and
said second charger.
16. An apparatus for managing a battery having a plurality of
cells, said apparatus comprising: a transfer switch having a first
state wherein an external power source is connected to provide
power, said transfer switch having a second state wherein the
battery is connected to provide power; and a plurality of chargers
each configured to be electrically connected to an associated cell
of the battery, said plurality of chargers connected to said
transfer switch whereby said plurality of chargers receive power
from said external source with said transfer switch in said first
state and from the battery with said transfer switch in said second
state, each one of said plurality of chargers configured to charge
said associated cell.
17. The apparatus of claim 16 further including a first load
disconnect switch operatively connected to a master module, said
first load disconnect switch configured to isolate a first load
from the battery, said master module causing said first load
disconnect switch to isolate said first load from the battery when
any one of the plurality of cells is determined to have an
operating parameter outside an acceptable range as determined by a
cell monitoring circuit associated with a corresponding one of said
plurality of chargers associated with said one of said plurality of
cells.
18. The apparatus of claim 16 further including a first load
connection configured to electrically connect a first load to the
battery and a second load connection configured to electrically
connect a second load across a portion of the battery, said portion
of the battery defined as at least one and less than all of the
plurality of cells of the battery, wherein each one of said
plurality of cells in said portion of the battery is independently
maintained by a corresponding one of said plurality of
chargers.
19. The apparatus of claim 16 wherein a master module receives data
from said external power source, said data including a capacity of
said external power source, and said master module controlling said
plurality of chargers to ensure said capacity is not exceeded by
said plurality of said chargers.
20. The apparatus of claim 16 further including a connector between
said external power source and said transfer switch, said connector
communicating a connector status with a master module, said
connector status including information that said external power
source is about to be disconnected from said transfer switch, and
said master module causing said external power source to be
electrically disconnected before said connector breaks an
electrical connection between said external power source and said
transfer switch.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of prior application Ser.
No. 14/042,245, filed Sep. 30, 2013, which is a continuation of
application Ser. No. 12/331,717, filed Dec. 10, 2008, which claims
the benefit of U.S. Provisional Application No. 61/012,907, filed
Dec. 11, 2007.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
BACKGROUND OF THE INVENTION
1. Field of Invention
[0003] This invention pertains to a battery management system for a
multi-cell battery system.
2. Description of the Related Art
[0004] Portable power sources are becoming ubiquitous. Batteries
provide operating power to many portable devices, from handheld
devices to electric vehicles. As the portable devices become more
powerful and greater demands are placed on them, so too must the
power supply be able to provide the power needed by those
devices.
[0005] Traditionally, batteries were charged as a unit. That is, a
single battery charger charged all the cells in their connected
configuration. This arrangement, although simple to implement, is
inefficient. Typically, the cells in a multi-cell battery do not
all have the same state of charge before and after charging. If one
cell has a higher state of charge before charging, then that cell
may be overcharged by bringing up the other cells to a full charge
state. Or, that cell may be fully charged, but the cells that
started at a lesser charge state are not fully charged. Either
situation is not desirable.
[0006] Attempts have been made to provide even charging of battery
cells and/or to equalize the charge between cells. For example,
Published Application Number 2006/0097700 discloses a battery with
most of the series connected cells 320-335 having a charging source
305-315, a shunt regulator 350-360, and a cell monitor 380-395. The
charging sources 305-315 are used one at a time with the shunt
regulators 350-360 isolating the cells that are not to be charged.
U.S. Pat. No. 6,150,795 discloses a single charge source 32
connected to a battery with series connected cells 31. Parallel
with the cells 31 are equalizer diverter modules 36 that equalize
the charge on the cells 31.
[0007] Another example is U.S. Pat. No. 6,369,546, which discloses
an array of cell units 12 for an orbiting satellite The cell units
12 are grouped into cells 14 of parallel connected cell units 12.
Each group of parallel connected cell units 12 has a charging
circuit 26 and a bypass switch 28. A single bulk charger 16 charges
all the cells 14 at a high rate and then equalization/balancing is
performed by a plurality of balancing switches 22 connected to
corresponding transformer/rectifier circuits 26 that provide
individual equalization of the cells 14. U.S. Pat. No. 6,586,909
discloses isolated regulators 26 connected to each cell 40 of a
battery 30. The charging system uses a multiple-winding transformer
20 to supply regulators 26 connected to the individual cells 40, or
group of cells. Each regulator is supplied power from a single
winding 22 of the multiple-winding transformer 20.
BRIEF SUMMARY OF THE INVENTION
[0008] According to one embodiment of the present invention, a
modular battery management system with interchangeable modules
connected to each cell and including a master module controlling
and managing the battery system. The battery system includes a
battery made of cells typically connected in series. Such a system
is a scalable battery management system that allows easy
replacement and maintenance. In addition, the system is readily
configurable to various size battery systems. One feature of the
battery management system is the ability of the battery to provide
power to the battery chargers in each slave module, where each
battery charger is configured to charge one or more, but less than
all, cells. In such a configuration, the battery management system
ensures that all the cells are maintained at an equal charge by
charging cells that have a charge less than the average charge of
each cell in the battery. A second related feature of the battery
management system is a transfer switch that selects between an
external source and the battery to provide power to the chargers
connected to the cells. A third feature of the battery management
system is that the system receives capacity data from an external
source and operates to charge the battery using no more than the
capacity of the external source.
[0009] The battery management system includes a master module and a
multitude of slave modules that are controlled by the master
module. Each of the modules is associated with one or more cells
forming a battery. Each module includes an isolated charging
circuit, a monitoring circuit for measuring cell parameters, a
module disconnect switch, and a controller connected to a
communications port. The master module further includes a
monitoring circuit that monitors battery parameters and circuits
for a load disconnect switch and a transfer switch. The load
disconnect switch isolates the load from the battery. The transfer
switch selectively connects the battery, the modules, and an
external power source.
[0010] In one embodiment, each module, including the master and the
slave modules, has a cell charging circuit that is isolated from
its power source. In one embodiment, the cell charging circuit is
magnetically coupled to an input power circuit that receives power
from either an external source or the battery. The magnetic
coupling isolates the charging circuit and allows the charging
circuit to be configured to the voltage of the cell. When the input
power circuit is connected to the external source by the transfer
switch, each cell is charged by its corresponding charging circuit
independently of the other cells in the battery. When the input
power circuit is connected to the battery by the transfer switch,
the cell charging circuit uses the battery power to charge its
associated cell if the cell voltage drops below a threshold. No
battery power is lost as heat because equalizing shunts are not
required. In one embodiment, the cell is charged only if certain or
specified battery parameters are within specified limits.
[0011] In one embodiment, an auxiliary load is connected across one
or more cells of the battery. The auxiliary load, for example, the
12 Vdc system of a vehicle, is powered independently of the main
load. The battery management system controls the slave module
connected to each of the cells powering the auxiliary load in order
to maintain the cells. For example, the slave module is powered by
the battery and when the charge of a cell connected to the
auxiliary load falls below a threshold, the module initiates
charging of the cell using power from the battery.
[0012] In one embodiment, the external power source communicates
data to the battery management system. For example, the data
includes the capacity of the external source. The battery
management system uses the capacity data to limit the charging
current in order to not exceed the capacity of the connected
external source.
[0013] Each module also includes a cell monitoring circuit, a cell
disconnect, and a communications port. The cell monitoring circuit
measures various parameters of the cell. In various embodiments,
these parameters include one or more of temperature, voltage,
current, and amp-hour capacity. The cell, or module, disconnect
isolates the cell from the module upon a signal from the master
module when the voltage of the cell falls below a setpoint value.
The communications port provides communications between the slave
modules and the master module. In various embodiments, the
communications ports are connected in a daisy chain, a star, a
ring, or a bus configuration.
[0014] The master module also includes a load disconnect switch
circuit, a transfer switch circuit, and a master controller and
display unit. The load disconnect switch circuit operates the load
disconnect switch upon a command from the master controller, for
example, when the voltage of one cell falls below a threshold value
indicating that further use will damage that cell, but only after
the battery management system attempts to balance the cells of the
battery. The transfer switch circuit operates the transfer switch
that connects the various modules to either the battery, an
auxiliary power supply, or an external power supply, or source.
[0015] In one embodiment, the master module is associated with the
first cell, which is positioned adjacent the negative, or earth,
lead of the battery. Upon initialization of the system, the master
module communicates with the slave modules and assigns an
identification code to each slave module based upon its location in
the battery. The identification code is assigned when the battery
is initialized, allowing the number of cells to vary between
applications with the slave modules uniquely associated with a
cell. The identification code is displayed for defective or poorly
performing cells to allow easy identification of the cell for
maintenance.
[0016] In the embodiment described above, the master module
includes the functions of a slave module because the master module
is connected to a cell and must monitor and charge that cell. In
other embodiments, the functions of the slave module are separated
from the master module and the master module is connected to the
battery, one or more cells, or an independent power supply. In such
an embodiment, the master module does not include a charging
circuit. Also, the master module has a battery monitoring circuit
for monitoring the parameters of the battery.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0017] The above-mentioned features of the invention will become
more clearly understood from the following detailed description of
the invention read together with the drawings in which:
[0018] FIG. 1 is a simplified schematic diagram of one embodiment
of a battery management system;
[0019] FIG. 2 is a simplified schematic diagram of one embodiment
of the master module;
[0020] FIG. 3 is a simplified schematic diagram of one embodiment
of one of the slave modules;
[0021] FIG. 4 is functional block diagram of one embodiment of the
steps taken to initialize the modules;
[0022] FIG. 5 is a simplified schematic diagram of one embodiment
of a scheme connecting two batteries to a single load; and
[0023] FIG. 6 is a simplified schematic diagram of another
embodiment of the master module.
DETAILED DESCRIPTION OF THE INVENTION
[0024] An apparatus for a battery management system 100 is
disclosed. Rechargeable batteries and cells attain a longer life
with greater capacity when the battery and its cells are charged
and discharged within its optimal operating parameters. Charging or
discharging individual cells or groups of cells allows the battery
or battery pack to not be limited by a cell that was not fully
charged or does not have the capacity of the other cells. The
battery management system features include charging, cell
equalization, load controlling, load monitoring and protection, and
battery pack management.
[0025] Charging returns a cell to a specified state of charge. Cell
equalization is balancing the cells in a battery such that the
cells have the same voltage and/or state of charge, within limits.
Load controlling is control of the load, such as with a motor
controller. Load monitoring and protection is measuring the
parameters of the load and ensuring that the parameters remain
within limits. Battery pack management includes ensuring that no
cell is operated outside its limits, thereby ensuring that the cell
is not damaged by over-discharging or over-charging, which will
ensure that the battery life is maximized. The apparatus also
creates and fosters a symbiotic relationship between load and
energy source in that by monitoring the load and energy source the
battery pack is protected from excessive loads and
over-discharging, and the load benefits by balancing cells and
delivering its maximum capacity to the load.
[0026] FIG. 1 illustrates a simplified schematic diagram of one
embodiment of a battery management system 100. The illustrated
embodiment of the system 100 includes a battery 106 with a
plurality of series connected cells 108. In various embodiments,
the cells 108 are individual battery units of one cell or a
collection of battery units with cells in a parallel configuration,
such as another battery cell. For example, if increased energy
capacity is desired, multiple individual cells are connected in
parallel and considered to be a single cell 108 in the
illustration. If increased voltage is desired, multiple individual
cells are connected in series and considered to be a single cell
108 in the illustration. As used herein, a cell 108 refers to a
battery unit, which includes one or more single cells connected in
series and/or parallel.
[0027] Connected to each cell 106 is either a master module 110 or
a slave module 112. One cell 108 is selected to be associated with
the master module 110. The other cells 108 are each associated with
a slave module 112. The slave modules 112 are in communication with
the master module 110. The communication connection is wired such
that the first cell 108-1 is associated with the master module 110,
the second cell 108-2 is associated with the first slave module
112-2, which is assigned the second sequential identifier. The
connections continue in this manner until the last cell 108-n is
associated with the last slave module 112-n, which is assigned the
last n sequential identifier. In one embodiment, the communication
connection is a daisy-chained connection, as illustrated in FIGS. 3
and 4, which allows for the automated identification of the slave
modules 112. In other embodiments, the communication connections
have other configurations, such as a star, ring, or a bus.
[0028] The power to the master module 110 and the slave modules 112
is controlled by a transfer switch 104. The transfer switch 104 has
multiple states and selectively connects the modules 110, 112 to
the battery 106 to an external source 102-A, or to an auxiliary
source 102-B or isolates the modules 110, 112 from both the battery
106 and the sources 102. In various embodiments, the transfer
switch 104 is an electromechanical relay-type switch or a
semiconductor-type switch. In the illustrated embodiment, the
transfer switch 104 is shown connected to the hot side or positive
potential side of the battery 106. In other embodiments, the
transfer switch 104 is located at the earth side of the battery 106
or two transfer switches 104 are positioned on opposite sides of
the battery 106. In various embodiments the sources 102 are power
sources or power supplies that provide power for charging the
battery and/or powering the load. For example, if the battery
management system 100 is in an electrically powered vehicle, the
external source 102-A is a power supply connected to the ac
(alternating current) mains. In various embodiments, the auxiliary
source 102-B a solar supply with or without an accumulator or
another power source that is configured to remain attached to the
battery management system 100, for example, a solar cell array
incorporated in the vehicle.
[0029] Connecting the sources 102 to the transfer switch 104 are
connectors 122-A, 122-B, each of which is an assembly with male and
female portions that make a removable electrical connection between
the sources 102 and the transfer switch 104. In the illustrated
embodiment, the connectors 122 communicate with the master module
110 to signal that the connected source 102-A, 102-B is about to be
disconnected from the transfer switch 104. In various embodiments,
the connectors 122 each include a switch, contacts, or conductors
that open before the power leads open when the connector 122 is
being disconnected. In another embodiment, the connectors 122
include a pair of coils that are magnetically connected to
establish a link when the connector 122 is mated. For example, the
connector 122 is a twist-lock type connector that requires that one
portion be twisted relative to the other. The twisting action
operates a switch or interrupts a signal path that signals the
master module 110. The master module 110 monitors for this signal
and when the master module 110 detects that the connector 122 is
being disconnected, the master module 110 causes the modules 110,
112 to shut down so as to minimize the power being carried through
the connector 122 before the connector 122 breaks the connection.
In another embodiment, one or both of the sources 102 monitor the
communications through the connector 122 and when the power source
102 determines that the connector 122 is being disconnected, the
power source 102 shuts down or interrupts the power flow before the
power circuit through the connector 122 is broken. In this way, the
connector 122 is not interrupting a large current flow between the
source 102 and the transfer switch 104.
[0030] In one embodiment, the connectors 122 include signal
conductors in addition to power conductors. The signal conductors
allow the master module 110 to communicate with the source 102. For
example, the external source 102-A communicates its power capacity
to the master controller 110, which then uses that information to
determine how best to control the slave modules 112 to charge the
associated cells 108. Another example is the auxiliary source 102-B
is a solar cell array, which communicates its capacity or available
wattage to the master controller 110, which then uses that
information to determine if the capacity is sufficient to supply
power to one or more of the slave modules 112 or otherwise meet the
needs of the system 100. If not, the master module 110 communicates
with the external source 102-A to determine if that source has
sufficient capacity.
[0031] One way the master module 110 uses power capacity
information is to instruct the slave modules 112 and the master
module 100 to limit the charging current for each associated cell
108 in order to not exceed the capacity of the available source
102. Another way is for the master module 110 to control the
charging circuits 202 in the modules 110, 112 so that the number of
cells 108 being charged at any one time does not exceed the
capacity of the connected source 102. For example, if the external
source 102 is rated at 40 amperes, the master module 110 instructs
the modules 110, 112 for each of the four cells 108 to limit the
charging current to 10 amperes, initially. If one cell 108 becomes
fully charged and the charging circuit 202 is shut down, the other
charging circuits 202 are instructed to increase their charging
current accordingly to maintain a maximum charging current without
exceeding the capacity of the source 102.
[0032] In one embodiment, the battery management system 100
connects only to the external source 102-A and there is no
auxiliary source 102-B. In another embodiment, the auxiliary source
102-B is located with the battery 106 and the battery management
system 100 and the external source 102-A is typically remotely
located from the system 100. The master module 110 monitors for the
presence of the external source 102-A. If the source 102-A is
present, in one such embodiment, the master module 110 selects one
source 102 preferentially over the other source 102 if both sources
102 have sufficient capacity to meet the power requirements of the
system 100. For example, the auxiliary source 102-B is selected to
supply power to the system 100 if the source 102-B has sufficient
capacity to meet the needs of the system 100. If the needs exceed
the capacity of the auxiliary source 102-B, the master module 110
causes the transfer switch 104 to connect the external source 102-A
to the modules 110, 112. In one embodiment, the auxiliary source
102-B is a solar cell array with a capacity testing device, such as
a voltage measurement device or a switched load that measures the
instantaneous power-producing capacity of the solar array.
[0033] In one embodiment, the external power source 102-A
determines that the source 102-A is connected to the battery
management system 100 because communications have been established
to the master module 110 through the connector 122-A. The power
source 102-A, after establishing communications with the master
module 110, powers up to a condition in which power is supplied to
the transfer switch 104. In a like manner, the external power
source 102-A powers down when the external power source 102-A
determines that the connector 122 is being disconnected, for
example, when communications is lost with the master module 110. In
one embodiment, the auxiliary source 102-B responds similarly.
[0034] A load 118 and a load disconnect switch 116 in series are
connected across the battery 106. The load 118 is any type of
electrical load, for example, a motor and controller for a vehicle
or remote field-operated equipment. The load disconnect switch 116
is controlled by the master module 110 to isolate the load 118 from
the battery. The load disconnect switch 116 is illustrated
connected to the earth side of the load 118. In other embodiments
the switch 116 is positioned on the other side of the load 118 or a
pair of switches 116 are connected on opposite sides of the load
118. The load disconnect switch 116 isolates the load 118 if one or
more cells 108 are determined to be operating outside specified
limits or if the master module 110 otherwise receives a signal to
control the switch 116. In various embodiments, the load disconnect
switch 116 is an electromechanical relay or a semiconductor-type
switch. In series with the cells 108 is a current sensor 120 that
communicates with the master module 110. The current sensor 120, in
one embodiment, is a current shunt suitable for the level of
current generated by the battery 106.
[0035] An auxiliary load 118' and an auxiliary load switch 116' in
series are connected across selected cells 108-1, 108-2 of the
battery 106. The auxiliary load 118' is any load that does not
require the full voltage of the battery 106. For example, when the
load 118 is a motor and controller for a vehicle that operates at
an elevated voltage, e.g., 48 volts, the auxiliary load 118'
includes the radio and other accessories that operate at a lower
voltage, e.g., 12 volts. In operation, the transfer switch 104 is
in the open state, that is, the transfer switch 104 isolates the
battery 106 and the sources 102 from the modules 110, 112. When the
voltage of any of the cells 108-1, 108-2 supplying the auxiliary
load 118' falls below a first setpoint, the transfer switch 104 is
directed, by the master module 110, to the state connecting the
battery 106 to the modules 110, 112. The master module 110 and/or
the slave module 112-2 that is connected to the cell 108-1, 108-2
with the low voltage charges that cell 108-1, 108-2 to raise its
voltage. In this way, the battery 106 and its cells 108 remain
serviceable for a longer period because the low cells 108 are
prevented from approaching the critical voltage point until almost
all the available energy in the battery 106 has been used. Stated
another way, some cells 108 are not required to supply as much
energy because the cells 108 are not required to supply a portion
of the load 118'. The cells 108 that are not required to supply
energy to the load 118' are used to supply energy indirectly,
through the master and slave modules 110, 112, to the cells that
supply energy directly to the load 118', thereby balancing the
battery 106. In the embodiment where an auxiliary power source
102-B is connected to the battery management system 100, the master
module 110 first causes the transfer switch 104 to connect the
auxiliary source 102-B to charge the cell 108 if the source 102-B
has sufficient capacity to be effective. If the source 102-B does
not have sufficient capacity, the transfer switch 104 connects the
battery 106 to the system 100.
[0036] In the illustrated embodiment, the battery management system
100 includes a controller 114 in communication with the master
module 110. In various embodiments, the controller 114 is an
external computer, a dedicated control console, or other
controller. For example, if the battery management system 100 is
used with an electric powered vehicle, the controller 114 includes
the operator console controls, such as the key switch, which is
comparable to the ignition switch of a gas powered vehicle. The
controller 114 accesses the information available to the master
module 110 and provides data storage and display of that
information. The controller 114 also provides control signals to
the master module 110 for operating and controlling the various
features that the master controller 110 controls. In one
embodiment, a portion of the control functions are assumed by the
controller 114 based on data passed to the controller 114 from the
master module 110.
[0037] In the illustrated embodiment, the battery management system
100 includes a remote display 124. The remote unit 124 communicates
with the master module 110 wirelessly. The remote unit 124 receives
status information on the management system 100 and the battery
106. For example, the received data includes the state of charge of
the battery 106 and the individual cells 108. The remote unit 124
is a personal device, such as a key fob or a personal data
assistant (PDA) or other wireless device, that has a display for
presenting the data to a user.
[0038] FIG. 2 illustrates a simplified schematic diagram of one
embodiment of the master module 110. The master module 110 is
configured to charge its associated cell 108-1, to monitor various
parameters of that cell 108-1 and the battery 106, to control the
load disconnect switch 116 and the transfer switch 104, and to
communicate with and control the slave modules 112.
[0039] A pair of power leads 222 supply power to the master module
110. The power leads 222 are connected to an input power circuit
206 that is, in turn, connected to a transformer 204 that
magnetically couples the power supply to the charging circuit 202.
The magnetic coupling provided by the transformer 204 isolates the
power supply connected to the power leads 222 from the electrical
connections 234 to prevent the cell 108 connected to the
connections 234 from shorting out to the next adjacent series
connected cell 108. The electrical isolation also avoids problems
associated with the various polarities and potentials associated
with the cell 108 connected to the cell leads 234. A module power
supply 232 provides power to the other components in the master
module 110. The power supply 232 receives power from the output of
the transformer 204 and/or from the cell 108 through the power
leads 234. The two power connections to the power supply 232 are
isolated by a pair of diodes 236 that allow current to flow to the
power supply 232, but isolate the two power connections from each
other. The power supply 232 remains operable regardless of the
power leads 222 being connected to a power supply 102, 106.
[0040] The charging circuit 202 is connected to a module disconnect
switch 212 that is connected to the cell 108 through a pair of
leads 234. The module disconnect switch 212 is controlled by the
master controller and display unit 214 to isolate the master module
110 from its associated cell 108. In the case where the associated
cell 108 has discharged to the point where continued use will
damage the cell 108, the master module 110 isolates itself from the
cell 108 to remove its parasitic draining of any remaining power
that the cell 108 may have left. Additionally, the module
disconnect switch 212 also isolates the cell 108 from the master
module 110 when the battery 106 is not being used or when another
source 102 is not available.
[0041] A cell and battery monitoring circuit 208 is electrically
connected to the associated cell 108 through the charging leads
234. The circuit 208 senses the voltage level of the cell 108
through these leads 234. The cell and battery monitoring circuit
208 also includes other connections 230 to the battery for
monitoring other parameters, for example temperature and/or
specific gravity. The cell and battery monitoring circuit 208 also
includes a connection 230 to the current sensor 120 that measures
the current through the battery 106. The cell and battery
monitoring circuit 208 provides data to the master controller and
display unit 214. In one embodiment the cell and battery monitoring
circuit 208 includes circuitry that converts the input signals
associated with the various parameters into an output signal
compatible with the master controller and display 214.
[0042] The master controller and display unit 214 includes a
processor that manages the master module 110 and the slave modules
112. In one embodiment the master controller and display unit 214
provides information to an operator, such as by illuminating
display lamps or by providing information on a text and/or
graphical display or monitor. In one embodiment, the master
controller 214 does not include a display unit portion. In one such
embodiment, the master module 110 communicates with a remote unit
124, such as a key fob or a personal data assistant (PDA) or other
wireless device. For example, the master controller and display
unit 214 includes a transmitter that sends data that is received by
the remote unit 124.
[0043] In one embodiment, the master controller 214 includes a
processor that executes a program or software that communicates
with the other internal circuits 202, 208, 212, 216, 218 and other
slave modules 112 through the communications port 210-M. The
communications port 210-M includes a communication line 224 that
starts the daisy chain connected to the slave modules 112. In one
embodiment, the communications port 210-M includes a circuit that
electrically isolates the communication line 224 from the other
components in the master module 110. For example, the
communications port 210 has opto-isolators that electrically
isolate the communications signals while allowing signal
communications to flow. The display portion of the master
controller and display unit 214 displays information regarding the
status of the master module 110, and also any information sent to
the master module 110 from any slave module 112. For example, if
the slave module 112-n, connected to the nth cell 108-n, determines
that its cell 108-n consistently is underperforming, the slave
module 112-n sends information that is displayed indicating that
the cell 108-n connected to slave module 112-n must be replaced or
serviced.
[0044] The load disconnect switch 116 is operated by the load
switch circuit 216, which is, in turn, controlled by the master
controller 214. The load switch circuit 216 converts the signal
from the master controller 214 to another signal suitable for
operating the load disconnect switch 116. In various embodiments,
the function of the load switch circuit 216 is performed by a
separate circuit or is incorporated into one or both of the load
disconnect switch 116 and the master controller 214.
[0045] The transfer switch 104 is operated by the transfer switch
circuit 218, which is, in turn, controlled by the master controller
214. The transfer switch circuit 218 converts the signal from the
master controller 214 to another signal suitable for operating the
transfer switch 104. In various embodiments, the function of the
transfer switch circuit 218 is performed by a separate circuit or
is incorporated into one or both of the transfer switch 104 and the
master controller 214.
[0046] FIG. 3 illustrates a simplified schematic diagram of one
embodiment of one of the slave modules 112. As in the master module
110, each slave module 112 is configured to charge its associated
cell 108-2 to 108-n, to monitor various parameters of that cell
108-2 to 108-n, and to communicate with the master controller 214
by sending commands via the communications port 210-S. FIG. 3 uses
the same reference numbers as used in FIG. 2 for the internal
circuit/module functions that are the same as those in FIG. 2.
[0047] The slave module 112 includes a pair of power leads 222 that
supply power to the slave module 112. The power leads 222 are
connected to an input power circuit 206 that is, in turn, connected
to a transformer 204 that magnetically couples the power supply to
the charging circuit 202. The magnetic coupling provided by the
transformer 204 isolates the power supply connected to the power
leads 222 from the electrical connections 234 to prevent the cell
108 connected to the connections 234 from shorting out to the next
adjacent series connected cell 108. The electrical isolation also
avoids problems associated with the various polarities and
potentials associated with the cell 108 connected to the cell leads
234. A module power supply 232 provides power to the other
components in the slave module 112. The power supply 232 receives
power from the output of the transformer 204 and/or from the cell
108 through the power leads 234. The two power connections to the
power supply 232 are isolated by a pair of diodes 236 that allow
current to flow to the power supply 232, but isolate the two power
connections from each other.
[0048] The charging circuit 202 is controlled by the slave
controller 302. The output of the charging circuit 202 is connected
to a module disconnect switch 212 that is connected to the cell 108
with a pair of leads 234. The module disconnect switch 212 is
controlled by the slave controller 302 to isolate the slave module
112 from its associated cell 108. The slave controller 302 receives
instructions from the master module 110 to operate the module
disconnect switch 212.
[0049] As in the master module 110, a cell monitoring circuit 308
is electrically connected to the associated cell 108 through the
charging leads 234. The circuit 308 senses the voltage level of the
cell 108 through these leads 234. The cell monitoring circuit 308
also includes other connections 230 to the battery for monitoring
other parameters, for example temperature and/or specific gravity.
The cell monitoring circuit 308 provides data to the slave
controller 302. In one embodiment the cell monitoring circuit 308
includes circuitry that converts the input signals associated with
the various parameters into an output signal compatible with the
slave controller 302.
[0050] The slave controller 302 evaluates one or more parameters
measured by the cell monitoring circuit 308 to determine if the
cell 108 has been discharged to the point where continued discharge
will damage the cell 108. For example, if the cell voltage drops
below a critical voltage point, the cell 108 is considered fully
discharged. The slave controller 302 communicates with the master
module 110 and provides status information on the cell 108
associated with that slave module 112.
[0051] In one embodiment, the slave controller 302 includes a
processor that executes a program or software that communicates
with the master controller 214 through the communications port
210-S to control the other internal circuits 202, 308, 212. The
communications port 210-S includes a pair of communication lines
304 that form a part of the daisy chain connecting the slave
modules 112 to the master module 110. In one embodiment, the
communications port 210-S includes a switch or other isolation
device or circuit that allows the communications port 210-S to
communicate with devices 110, 112 downstream in the daisy chain
304-dn, but selectively inhibits communication with devices 112
upstream in the daisy chain 304-up. In one embodiment, the
communications port 210-S includes a circuit that isolates the
communication lines 304 from the other components in the slave
module 112. For example, the communications port 210 has
opto-isolators that electrically isolate the communications signals
while allowing signal communications to flow.
[0052] In one embodiment, the slave module 112 includes a display
306 that provides visual indication of information. In one such
embodiment, the display 306 is controlled by the slave controller
302. The information provided by the display 306, in various
embodiments, includes the identification code of the slave module
112, status information of the slave module 112, and status
information for the associated cell 108. In one embodiment, the
display 306 includes light emitting diodes LEDs that indicate
status information for the slave module 112.
[0053] In one embodiment, one of the slave modules 112-2 to 112-n
is designated as a pseudo-master. The pseudo-master is a selected
slave module 112 that is configured to replace a master module 110
in the event that the master module 110 becomes, or in the process
of becoming, disabled. In such an embodiment, the selected slave
module 112 is programmed to take over the functions of the master
module 100 by assuming the master role and commanding all the other
slave modules 112. If the selected slave module, or pseudo master,
112 determines that the master module 110 is not functioning, the
selected slave module 112 initiates and controls an orderly
shutdown of the battery management system 100 by initiating
commands from the slave controller 302 through the communications
port 210-S to all the other slave modules 112.
[0054] In one embodiment, the battery management system 100
includes two master modules 110, but only one master module 100
(the primary) is operated as a master module 110. The other module
110 (the secondary) is operated as a slave module 112 until such
time that the secondary module 110 determines the primary module
100 is no longer operating properly. In one such embodiment, all
the slave modules 112 are master modules 110 operated as slaves. In
another such embodiment, the secondary module 110 executes a
watchdog routine to monitor the primary module 110.
[0055] The master module 110 stores data collected from the slave
modules 112. The master module 110 communicates this data to the
pseudo-master module 110, 112 so that, in case of need, the module
110, 112 has a duplicate of the data stored by the master module
110. Similarly, in one embodiment, the master module 110 also
stores data obtained and used by each slave module 112. When a
slave module 112 is replaced during maintenance, the master module
110 uploads the appropriate data to the replacement slave module
112.
[0056] Referring to FIGS. 1-3, the load disconnect switch 116
isolates the load 118 from the battery 106 upon a command from the
master module 110. The load 118 is disconnected by the switch 116
when any slave module 112 reports to the master module 110 or the
master module 110 itself determines that its associated cell 108
have a parameter outside specified limits or the master module 110
receives a signal from an outside source or the controller 114 to
disconnect the load 118.
[0057] A disconnection signal is also generated by the master
module 110 if the master module 110 determines that a slave module
112 is not functioning properly. The master module 110 periodically
communicates with each slave module 112. If the communication link
is interrupted, such as by a failure of a module 112, or a slave
module 112 self-reports a failure condition, the master module 110
isolates the load 118 with the disconnect switch 116.
[0058] The master module 110 isolates the load 118 when the module
110 determines that a battery parameter is outside specified
limits. For example, the current sensor 120 continuously measures
the battery current. If the battery current exceeds a specified
limit, the load 118 is isolated to prevent damage to the battery
106. In another example, the voltages of the battery 106 and each
cell 108 is continuously measured and the load 118 is isolated when
the voltage falls below a specified limit.
[0059] When the battery management system 100 is used with an
electric powered vehicle, the master module 110 isolates the load
118 from the battery 106 when an external source 102-A is connected
to the system 100. Because the external source 102-A is outside the
vehicle, the load 118 is isolated to prevent the vehicle from
moving while it is tethered by the power cable connecting the
external source 102-A to the transfer switch 104.
[0060] The master module 110 also isolates the load 118 when the
controller 114 so instructs the master module 110. For example,
such an instruction is sent when the key switch for an
electric-powered vehicle is moved to the off position.
[0061] Referring to FIGS. 1-3, the transfer switch 104 is a
multi-state switch that selectively connects the battery 106 and/or
one of the sources 102 to the modules 110, 112. The transfer switch
104 is controlled by the master module 110.
[0062] When an external source 102-A is connected to the system
100, the transfer switch 104 connects the external source 102-A to
the modules 110, 112. Before the connection is made, the external
power source 102-A must satisfy specified parameters, such as
having the proper voltage and polarity. In various embodiments, the
master module 110 measures these parameters at the transfer switch
104 or at other locations to determine if the external source 102-A
is suitable for connection. After the transfer switch 104 connects
the external source 102-A to the modules 110, 112, the master
module 110 instructs the slave modules 112 to begin charging their
respective cells 108. In another embodiment, the parameters are
determined by the master module 110 and the external power supply
102-A communicating with each other. In one embodiment, the
auxiliary source 102-B operates in a similar manner.
[0063] After all the modules 110, 112 determine that their
corresponding cells 108 are fully charged, the master module 110
instructs the transfer switch 104 to isolate the sources 102 and
the battery 106 from the modules 110, 112. In another embodiment,
the transfer switch 104 is also instructed to isolate the battery
106 from the sources 102 and the modules 110, 112.
[0064] With the battery 106 providing power to the load 118, if a
module 110, 112 determines that a cell 108 is operating outside
specified limits, that is, the cell 108 is not balanced with the
other cells 108, the transfer switch 104 connects the battery 106
to the modules 110, 112. For example, a cell 108 with a voltage
less than a setpoint value or less than an average value of other
cell voltages or is not balanced with the other cells 108 or has an
energy capacity that is below a specified value, then the master
module 110 causes the transfer switch 104 to energize the modules
110, 112 with the battery 106 as a power source and instructs the
slave module 112 for that cell 108 to charge the cell 108. In
various embodiments, each module 110, 112 determines the energy
capacity of its associated cell 108 using a coulomb counting method
or other technique. The energy capacity information is transmitted
to the master module 110, which determines if the energy capacity
of any cell 108 is below a specified value or deviating by a
specified amount from the average capacity of the other cells 108.
The module 110, 112 associated with the unbalanced cell 108 relies
upon the battery 106 for the energy to charge that cell 108. After
that cell 108 is brought to the same state of charge as the other
cells 108, the master module 110, 112 instructs the module 110, 112
to cease charging and then instructs the transfer switch 104 to
isolate the modules 110, 112 from the battery 106.
[0065] Referring to FIGS. 1-3, the module disconnect switch 212
isolates the module 110, 112 from its associated cell 108 after the
cell 108 is discharged to a specified level, for example, 0%
capacity, but before the cell 108 becomes over-discharged. For
cells 108 associated with a slave module 112, when a measured
parameter of the cell 108 indicates that the cell 108 needs to be
isolated, the module 112 communicates that information to the
master module 110 and then operates the disconnect switch 212 to
remove any parasitic drain caused by the module 112. After an
external source 102-A is connected to the system, the master module
110 instructs the module 110, 112 to operate the disconnect switch
212 to reconnect the cell 108 to the module 110, 112. If the
auxiliary source 102-B has sufficient capacity to power the module
110, 112, such as a solar array that is exposed to sufficient
light, the master module 110 causes the transfer switch 104 to
connect the auxiliary source 102-B to the system 100 and instructs
the disconnected module 110, 112 to operate the disconnect switch
212 to reconnect the cell 108 to the module 110, 112.
[0066] Referring to FIGS. 1-3, the modules 110, 112 have a common
power input. The transfer switch 104 connects either the battery
106, the external source 102-A, or the auxiliary source 102-B to
all the modules 110, 112. The common power input to the modules
110, 112 is isolated from the other modules 110, 112 and cells 108.
In one embodiment, the isolation is accomplished by the magnetic
coupling through the transformer 204.
[0067] When the transfer switch 104 connects the source 102-A,
102-B to the modules 110, 112, any module 110, 112 that was
isolated from its associated cell 108 is powered up and
initialized. The initialization includes communicating with the
master module 110 and processing any instruction to operate the
module disconnect switch 212 to reconnect the associated cell 108
to the module 110, 112.
[0068] Referring to FIGS. 1-3, the master controller 214 and the
slave controller 302 include a storage component that stores data
relevant to the module 110, 112 and its associated cell 108. For
example, the cell 108 characteristics are stored, including the
cell nominal voltage, the cell critical voltage point, the cell
energy capacity. The controllers 214, 302 also store the
identification of the module 110, 112 and its associated cell
108.
[0069] In addition, the master controller 214 stores data relating
to the number and characteristics of the attached slave modules 112
and data relating to the battery 106, for example, the battery
nominal voltage, the battery current ratings, and the battery
energy capacity. For the case where a slave module 112 must be
replaced during maintenance, the master controller 110 initializes
the slave module 112 as illustrated in FIG. 4 and the by uploading
data to the replacement slave module 112 so that the replacement
slave module 112 is able to continue where the failed or replaced
module 112 left off.
[0070] FIG. 4 illustrates a functional block diagram of one
embodiment of the steps taken to initialize the modules 112. When
the battery management system 100 is first initialized, the master
module 110 identifies each slave module 112 by its order relative
to the cell 108 position in the battery 106. For example, the slave
module 112-2 associated with the second cell 108-2 has an
identification code of 2. The illustrated steps are performed by
each slave module 112.
[0071] When the system 100 is first energized or when a setup
switch is actuated, the process starts 402. Initially, the master
module 110 has a preset identification code and the master module
110 maintains its communications line 224 enabled. Initially, the
slave module 112 has its communications line 304 disabled. That is,
the slave module 112 does not communicate through the
communications port 210-S and the daisy-chain 304 is broken and no
signals are able to pass through the slave module 112. The
communications port 210-S includes a circuit that prevents
communications from passing in either direction between the
upstream line 304-up and the downstream line 304-dn of the
daisy-chained communications line 304. In various embodiments, the
circuit is implemented with a relay, optical switch, a
semiconductor switch, or other types of components and/or
circuits.
[0072] The first step 404 is for the slave module 112 to determine
if its identification code is set. If the slave module 112 has an
identification code set, then the next step 406 is for the slave
module 112 to begin normal operation, which includes the step 408
of enabling communications through the communications port 210-S.
The slave module 112 then performs the step 410 of checking to see
if it has received a reconfiguration command from the master module
110. If not, then the slave module 112 enters a continuous loop of
normal operation 406 with communications enabled 408 and periodic
checks to see if a reconfiguration command has been received
410.
[0073] If a reconfiguration command has been received or if the
slave module 112 does not have its identification code set, the
next step 412 is for the slave module 112 to generate a unique
identifier, such as a random number. The random number is
considered a unique identifier for each slave module 122 because
the pool of generated random numbers is significantly larger than
the number of slave modules 112. In another embodiment, each module
110, 112 has a unique serial number, which is a unique identifier
and used in place of the random number. Accordingly, the unique
identifier differentiates each slave module 112 from every other
slave module 112 in the battery management system 100.
[0074] After generating the unique identifier, the next step 414 is
for the slave module 112 to wait to connect to the communications
line 304. After waiting, the next step 416 is for the slave module
112 to enable communications. In one embodiment, communications is
enabled on the downstream communications line 304-dn. If the slave
module 112 establishes downstream communications 418, then that
means that either the slave module 112 is associated with the first
cell 108 or the slave modules 112 that are downstream have already
completed the steps to obtain an identification code.
[0075] If the slave module 112 does not establish downstream
communications 418, then the next step 420 is to disable
communications and loop to the step 414 of wait to connect. In one
embodiment, the waiting step 414 waits a time based on a random
number. Doing so introduces randomness into the times that the
communications line 304 is enabled.
[0076] If the slave module 112 establishes communications
downstream with the master module 110 or another slave module 112,
the next step 422 is to query for the highest identification code
that has been assigned. In one embodiment, the step 422 of querying
is performed by communicating with the master module 110, which
informs the slave module 112 of the last identification code
assigned to a slave module 112. In another embodiment, the slave
module 112 communications with the next slave module 112 downstream
to obtain that module's identification code. The step 424 of
incrementing that identification code and saving it is then
performed and the slave module 112 then enters a normal operation
mode by next performing step 406 of beginning normal operation.
[0077] The communication ports 210-S of the slave modules 112 are
connected in a daisy-chain pattern with the master module 110 at
the beginning of the daisy chain. When each slave module 112
attempts to communicate with the master module 110 at random times
(step 406), the slave module 112 will only be successful if any
communication ports 210-S between that slave module 112 and the
master module 110 are open to communications. The first slave
module 112-2 that can communicate with the master module 110 is the
slave module 112-2 that is first in line from the master module
110. When that first slave module 112-2 establishes communication
408, the slave module 112-2 is assigned a sequential identification
number of two. The sequential identification number corresponds to
the position of the associated cell 108 in the battery 106. The
first slave module 112-2 keeps its communications port 210-S open
and connected after the slave module 112 identified. By keeping the
communications open, the next slave module 112 in line on the daisy
chain is able to establish communication with the master module
110. The slave modules 112 continue seeking communications until
all the slave modules 112 have sequentially established
communications and have been identified with a sequential,
incremental identifier.
[0078] If a slave module 112 is replaced because of failure or
other maintenance, the slave module identification setup is
re-initiated to identify the new slave module 112, along with
re-identifying the other slave modules 112. By using sequential
incremented identifiers, the master module 110 need only display
the identifier to allow a technician or other maintenance person to
quickly identify the cell 108 and/or slave module 112 for
servicing. For example, if the master module 110 reports a problem
with the cell 108 associated with the slave module 112 having a
sequential identifier of five, the service person need only count
the fifth cell 108 starting with the first cell 108-1 associated
with the master module 110.
[0079] Referring to FIGS. 1-4, the battery management system 100
operates by initializing the slave modules 112 as described in FIG.
4. When the slave modules 112 are initialized and identified, the
master module 110 switches the transfer switch 104 to the state
where the source 102 is connected to the modules 110, 112. In the
embodiment where the transfer switch 104 is connected to both an
external source 102-A and an auxiliary source 102-B, the master
module 110 selects the source 102 that has sufficient capacity to
meet the needs of the system 100. In one embodiment, the master
module 110 selects the source 102 that is most economical, for
example, an auxiliary source 102-B that receives solar power is
more economical than an external power source 102-B that is
requires a fee per unit power. Another example is an auxiliary
source 102-B that is a fuel cell or fuel powered generator, which
is more expensive to operate than to purchase power through the
external power source 102-A.
[0080] Upon receiving power, the modules 110, 112 determine the
condition of its associated cell 108 and charges that cell 108
accordingly. The loads 118, 118' may or may not be connected to the
battery 106 while it is being charged. The system 100 is controlled
by the controller 114 to connect the loads 118, 118' as
desired.
[0081] As each cell 108 is charged, the associated module 110, 112
turns off its charging circuit 202. When all the cells 108 are
charged, the master module 110 operates the transfer switch 104 to
the state isolating the modules 110, 112 from both the battery 106
and the sources 102.
[0082] If the external power source 102 and the auxiliary source
102-B is not available, or the auxiliary source 102-B does not have
sufficient capacity, and one of the modules 110, 112 determines
that a cell has reached a first specified discharge level, the
module 110, 112 communicates with the master module 110, which
operates the transfer switch 104 to the state connecting the
battery 106 to the modules 110, 112. The module 110, 112 associated
with the partially discharged cell 108 charges that cell 108 using
the battery 106 as a power source. In this way, the cells 108 are
balanced as the battery 106 is discharged. When any one of the
modules 110, 112 determines that a cell has reached a second
specified discharge level, the module 110, 112 communicates with
the master module 110, which operates the load disconnect switches
116, 116' to isolate the battery 106 from the loads 118, 118'. The
associated module 110, 112 operates the module disconnect switch
212 to isolate the associated cell 108 from the module 110, 112,
thereby turning off any parasitic load and minimizing the
probability that the cell 108 will be damaged. When the external
source 102-A is connected to the transfer switch 104, the master
module 110 operates the transfer switch 104 to the state connecting
the source 102-A to the modules 110, 112 and the modules 110, 112
begin charging their associated cells 108, as appropriate.
[0083] If either the external power source 102-A or the auxiliary
source 102-B is available with sufficient capacity and one of the
modules 110, 112 determines that a cell 108 has reached a first
specified discharge level, the master module 110 operates the
transfer switch 104 to the state connecting the source 102 to the
modules 110, 112 and the module 110, 112 associated with the
partially discharged cell 108 charges that cell 108 using the
source 102 as a power source. When any one of the modules 110, 112
determines that a cell has reached a second specified discharge
level, the module 110, 112 communicates with the master module 110,
which operates the load disconnect switches 116, 116' to isolate
the battery 106 from the loads 118, 118'. The unloaded battery 106
is then charged by the modules 110, 112.
[0084] FIG. 5 illustrates a simplified schematic diagram of one
embodiment of a scheme connecting two batteries 106-A, 106-B to a
single load 118. When multiple batteries 106-A, 106-B are available
for connecting to a load 118, it is often desirable to connect
those batteries 106-A, 106-B to the load 118 with a configuration
that accommodates the load's energy requirements. For example, when
greater energy capacity is required, two batteries 106-A, 106-B are
connected in parallel and when greater energy potential is
required, two batteries 106-A, 106-B are connected in series.
[0085] The illustrated configuration includes two independent
battery management systems 100-A, 100-B. The first battery 106-A
has one end connected directly to the load 118 and disconnect
switch 116 and the other end with a first switch (SW1) 502
connected between the load 118 and the first battery 106-A. The
second battery 106-B has a pair of switches (SW2 & SW1) 504,
502 connected between the second battery 106-B and the load 118 and
disconnect switch 116.
[0086] The two switches (SW1 & SW2) 502, 504 are positioned
such that to configure the two batteries 106-A, 106-B in parallel,
the first switch (SW1) 502 connects the positive end of the first
and second batteries 106-A, 106-B to the load 118 and the second
switch (SW2) 504 connects the negative end of the second battery
106-B to the load 118 and the disconnect switch 116 and isolates
the negative end of the second battery 106-B from the positive end
of the first battery 106-A. In this configuration, the energy
capacity available to the load 118 is doubled with the two
batteries 106-A, 106-B in parallel.
[0087] To configure the two batteries 106-A, 106-B in series, the
first switch (SW1) 502 isolates positive end of the first battery
106-A. The second switch (SW2) 504 isolates the negative end of the
second battery 106-B from the load 118 and the disconnect switch
116 and connects the negative end of the second battery 106-B to
the positive end of the first battery 106-A. In this configuration,
the potential applied to the load 118 is doubled with the two
batteries 106-A, 106-B in series.
[0088] In another embodiment, the first battery 106-A is connected
to the load 118 by isolating completely the second battery 106-B
from the load 118 by opening one or both of the switches (SW1 &
SW2) 502, 504. When the first battery 106-A is depleted, the first
battery 106-A is isolated by the switches (SW1 & SW2) 502, 504
and the second battery 106-B is connected to the load and the
disconnect switch 116 by the switches (SW1 & SW2) 502, 504. In
this embodiment, the running time of the load 118 is doubled with
the two batteries 106-A, 106-B.
[0089] The controller 114 is connected to each system 100-A, 100-B
and the two switches (SW1 & SW2) 502, 504. The controller 114
changes the configuration of the multiple batteries 106-A, 106-B to
accommodate the changing requirements of the load 118. In other
embodiments, the number of batteries 106 varies to accommodate the
energy capacity and potential requirements of the load 118.
[0090] FIG. 6 illustrates a simplified schematic diagram of another
embodiment of the master module 100'. The illustrated master module
100' is not associated with a specific cell 108. Instead, the
master module is connected to the battery 106, or in various other
embodiments, an independent cell or battery. The connection leads
234 for the master module 100' are connected to the battery
106.
[0091] The illustrated embodiment of the master module 110' does
not include a battery charger 202 nor a cell and battery monitoring
circuit 208 because the master module 110' is not associated with a
cell 108 that needs monitoring and charging. The input power leads
222 provide power to the input power circuit 206, which supplies a
transformer 204. The output of the transformer 204 is connected to
the module power supply 232 through an isolation diode 236. The
leads 234 connecting the master module 110' to the battery 106 are
also connected to the module power supply 232 through another diode
236. The diodes 236 isolate the two power sources.
[0092] The master module 110' includes a battery monitoring circuit
608 that monitors parameters of the battery 106. In one embodiment,
the battery monitoring circuit 608 has a connection 630 to the
current sensor 120 that measures battery current. The battery
monitoring circuit 608 determines the state or condition of the
battery 108 as a whole. The master module 110' communicates with
the slave modules 112 to determine the state or condition of
individual cells 108.
[0093] FIGS. 1-3, 5, and 6 illustrate simplified schematics. The
simplified schematics do not illustrate various connections, for
example, power and ground connections to the various components;
however, those skilled in the art will recognize the need for such
wiring and understand how to wire such a circuit, based on the
components ultimately selected for use.
[0094] As used herein, the master controller 214 and the slave
controllers 302 should be broadly construed to mean any device that
accepts inputs and provides outputs based on the inputs, for
example an analog control device or a computer or component thereof
that executes software, such as a micro-controller or a general
purpose computer. In various embodiments, the controllers 214, 302
are a specialized device or a computer that implements the
functions. The controllers 214, 302 include input/output (I/O)
units for communicating with external devices and a processing unit
that varies the output based on one or more input values. A
computer-based controller 214, 302 includes a memory medium that
stores software and data and a processing unit that executes the
software. Those skilled in the art will recognize that the memory
medium associated with the computer-based controller 214, 302 can
be either internal or external to the processing unit of the
processor without departing from the scope and spirit of the
present invention.
[0095] The input component of the controller 214, 302 receives
input from external devices, such as current sensors 120 and
temperature sensors. The output component sends output to external
devices, such as the various switches 104, 116. The storage
component stores data and program code. In one embodiment, the
storage component includes random access memory and/or non-volatile
memory.
[0096] In one embodiment, each of the functions identified herein
are performed by one or more software routines executed by the
controllers 214, 302. In another embodiment, one or more of the
functions identified are performed by hardware and the remainder of
the functions are performed by one or more software routines run by
the controllers 214, 302. In still another embodiment, the
functions are implemented with hardware, with the controllers 214,
302 providing routing and control of the entire integrated system
100.
[0097] In one embodiment, the controllers 214, 302 execute
software, or routines, for performing various functions. These
routines can be discrete units of code or interrelated among
themselves. Those skilled in the art will recognize that the
various functions can be implemented as individual routines, or
code snippets, or in various groupings without departing from the
spirit and scope of the present invention. As used herein, software
and routines are synonymous. However, in general, a routine refers
to code that performs a specified function, whereas software is a
more general term that may include more than one routine or perform
more than one function.
[0098] The battery management system 100 includes various
functions. The function of preventing damage to a cell is
implemented, in one embodiment, by monitoring one or more
parameters of the cell 108 and isolating the cell 108 at or before
a critical point of one or more of those monitored parameters is
reached. Isolating the cell 108 prevents parasitic power draw from
the module 110, 112 draining the cell 108 and potentially damaging
the cell 108.
[0099] The function of prolonging the service life of a charge is
implemented, in one embodiment, by monitoring one or more
parameters, for example, the voltage, of each cell 108 when the
battery 106 is connected to the load 118 and charging any cell 108
that approaches a critical point of one or more of those
parameters. In this way the other cells 108 elevate the the weak
cell 108 instead of shutting down the battery 106 because one cell
108 is weak, thereby maximizing the operating time of the battery
106.
[0100] The function of preventing arcing when disconnecting the
source 102 is implemented, in one embodiment, by a connector 122
that allows communication between the master module 110 and the
power source 102 before the power connection is broken. In one such
embodiment, the master module 110 controls the modules 110, 112 to
reduce the load drawn from the source 102 instead of allowing the
connector 122 to interrupt the circuit. In another embodiment, the
source 102 determines the connector 122 is about to be disconnected
and the source 102 shuts down the power to the transfer switch
104.
[0101] The function of initializing the slave modules 112 during
initial installation or during maintenance replacements is
implemented, in one embodiment, by the master module 110
communicating with the slave modules 112, as illustrated in FIG. 4,
to assign identification codes to the slave modules 112.
[0102] The function of providing a failsafe for the master module
110 is implemented, in one embodiment, by one slave module 112
being designated as a pseudo-master. In another embodiment, the
function of providing a failsafe is implemented by having two
master modules 110, one operating as a primary and the other as a
secondary master module 110.
[0103] The function of maintaining battery 106 health under load
when one of the sources 102 is connected is implemented, in one
embodiment, by operating the master module 110 and the slave
modules 112 to continually monitor the cells 108 and charge any
cell 108 that is discharged below a specified setpoint. Because the
cells 108 are monitored individually, a weak cell 108 is able to be
charged before it is damaged or it shuts down the load 118. For the
case where the rate of discharge through the load 118 is less than
the charge rate of the modules 110, 112, the cells 108 are
maintained in a fully charged state. For the case where the rate of
discharge through the load 118 is greater than the charge rate of
the modules 110, 112, such as when the discharge rate is greater
than the capacity of the connected source 102, the battery 106 is
gradually discharged with no one cell 108 being depleted before the
others. That is, the weakest cells 108 are charged at a maximum
rate because the weakest cells 108 determine the point at which the
battery 106 must be shut down to prevent damage to the cells
106.
[0104] The function of powering a module 110, 112 with the transfer
switch 104 isolating the modules 110, 112 is implemented, in one
embodiment, by the power supply 232 receiving power from the
associated cell 108. In one embodiment, the diodes 236 isolate two
power sources: the cell 108 and the power from the input power
circuit 206.
[0105] The function of paralleling multiple batteries 106-A, 106-B
for a single load 118 is implemented, in one embodiment, by two
battery management systems 100, one for each battery 106-A, 106-B.
The source 102 is connected to both transfer switches 104-A, 104-B.
A third transfer switch 502 connects each battery 106-A, 106-B to
the load 118, independently or together. A fourth transfer switch
504, in conjunction with the third switch 502, performs the
function of connecting the batteries 106-A, 106-B to the load 118
in series or in parallel.
[0106] While the present invention has been illustrated by
description of several embodiments and while the illustrative
embodiments have been described in considerable detail, it is not
the intention of the applicant to restrict or in any way limit the
scope of the appended claims to such detail. Additional advantages
and modifications will readily appear to those skilled in the art.
The invention in its broader aspects is therefore not limited to
the specific details, representative apparatus and methods, and
illustrative examples shown and described. Accordingly, departures
may be made from such details without departing from the spirit or
scope of applicant's general inventive concept.
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